RU2686253C2 - Braking system of vehicle - Google Patents

Abstract

FIELD: automotive industry.SUBSTANCE: invention relates to automotive industry. Vehicle braking system includes a working braking element to be controlled by a vehicle driver, hydraulic brake device provided for one of front wheel and rear wheel and configured to generate hydraulic braking force in accordance with operation of operating brake element, and an electric braking device provided for the other of the front wheel and the rear wheel and configured to generate an electric braking force in accordance with the operation of the operating braking element. Hydraulic braking force depends on working fluid pressure. Electric braking force depends on electric motor motion.EFFECT: improved technical characteristics of the device.15 cl, 30 dwg

Description

The level of technology

The technical field to which the invention relates.

[0001] The present disclosure relates to a braking system configured to brake a vehicle.

Description of the prior art

[0002] Many conventional vehicle brake systems are hydraulic brake devices, as disclosed, for example, in JP-A-2004-338582. Some vehicle brake systems are electrical braking devices, as disclosed, for example, in JP-A-2001-263395.

Summary of Invention

[0003] A hydraulic braking device has the advantage of high reliability, and an electric braking device has the advantage of a good response. However, these braking devices have corresponding drawbacks. The disclosure aspect provides a vehicle brake system having a high utility.

[0004] In one aspect of the disclosure, a vehicle braking system includes: a service braking element that is to be controlled by a driver of the vehicle; a hydraulic braking device provided for one of the front wheel and the rear wheel and configured to form a hydraulic braking force in accordance with the operation of the operating braking element, the hydraulic braking force depending on the pressure of the working fluid; and an electric braking device provided for the other of the front wheel and the rear wheel and configured to form an electric braking force in accordance with the operation of the operating braking element, the electric braking force depending on the movement of the electric motor.

[0005] According to a vehicle braking system with a structure as described above, a hydraulic braking device and an electric braking device are provided for one and the other of the front wheel and the rear wheel. Therefore, it is possible to implement practically applicable brake system, which takes advantage of the respective brake devices.

Various forms

[0006] Various forms of a vehicle braking system, which may be claimed as a subject of the claims, are approximately illustrated and explained below. Each of the forms is numbered as a clause of the appended claims and depends on a different form or forms as necessary. This serves to simplify the understanding of the vehicle braking system claimed as a matter of the claims, and it should be understood that the combinations of the constituent elements that make up the vehicle braking system are not limited to the forms described below. Thus, it should be understood that the claimed vehicle brake system as claimed in the claims must be interpreted in the light of the following description of various forms and embodiments. Additionally, it should be understood that, provided that the vehicle brake system as claimed is interpreted as such, any form in which one or more of the constituent elements are added or removed to / from any of the following forms can be considered as one form of as the subject of the claims of the vehicle brake system.

[0007] a. Basic forms

(1) A vehicle braking system comprising:

- working brake element, which must be controlled by the driver of the vehicle;

- hydraulic brake device provided for one of the front wheel and rear wheel and configured to form a hydraulic braking force in accordance with the operation of the operating braking element, the hydraulic braking force depending on the pressure of the working fluid; and

- an electric braking device provided for the other of the front wheel and the rear wheel and configured to form an electric braking force in accordance with the operation of the operating braking element, the electric braking force depending on the movement of the electric motor.

[0008] This form is the basic form of the vehicle brake system claimed as a subject of the claims. According to this form, braking devices of mutually different types are provided for one and the other of the front wheel and the rear wheel. In view of this, it is possible to design a braking system that takes advantage of the respective two braking devices, i.e. hydraulic braking device and electric braking device. In particular, a hydraulic braking device has the advantage of high reliability, and an electric braking device has the advantage of a good response. Thus, the vehicle brake system according to this form takes advantage of the respective devices. Additionally, it is not necessary to provide a hydraulic braking device for both of the front wheel and the rear wheel, so that the hydraulic braking device has a compact size, and the vehicle brake system itself, respectively, is compact.

[0009] Preferred specific hydraulic brake device designs are explained in the following forms. The electric braking device can be of any design, provided that the electric braking device is configured to apply, through a motion conversion mechanism, a force generated by an electric motor as a force to stop or slow down the rotation of the wheel when controlling the force.

[0010] It is not necessary that both of the hydraulic braking device and the electric braking device are configured to control the respective braking forces to be generated. In a hydraulic braking device comprising a master cylinder equipped with an amplifier due to negative pressure, for example, it is possible to obtain, without electronic control, a braking force in accordance with the working force applied to the operating braking element. In the case in which such a hydraulic braking device is used, the braking force generated by the electric braking device is mainly controlled. Because of this, this form can be modified.

[0011] In this form, a hydraulic braking device may be provided for the front wheel, while an electric braking device may be provided for the rear wheel, or a hydraulic braking device may be provided for the rear wheel, while an electric braking device may be provided for the front wheels. In conventional vehicles, the braking force provided to the front wheel is set above the braking force provided to the rear wheel. In view of this, the first is preferable, namely, it is preferable in order to provide, for the front wheel, a hydraulic braking device with high reliability. As explained below, in the case in which the vehicle braking system includes a regenerative braking device, a determination as to which front wheel and rear wheel each of the hydraulic braking device and the electric braking device are provided for may be performed depending on For which of the front wheel and the rear wheel is a regenerative braking device provided.

[0012] b. Combined control of hydraulic braking force and electric braking force

The following forms relate to the combined control of hydraulic braking force and electric braking force.

[0013] (11) The braking system of the vehicle according to form (1), in which the hydraulic braking force and the electric braking force are controlled so that they interact with each other.

[0014] By interacting the hydraulic braking force and the electric braking force, it is possible to design a more practically applicable vehicle braking system according to this form. The interaction of hydraulic braking force and electric braking force is not limited to a specific configuration, provided that each of the hydraulic braking force and electric braking force acts as one component of the braking force to brake the vehicle (hereinafter referred to as "vehicle braking force" if necessary) in a state in which the relative regulation of the hydraulic braking force and the electric braking force is maintained. For example, one configuration of the interaction of hydraulic braking force and electric braking force may include a configuration in which at least one of the hydraulic braking force and electric braking force is controlled so that the distribution of the braking force on the front wheel and the rear wheel becomes equal a given distribution, regardless of whether or not regenerative braking force should be formed (which is explained below). Specific interaction configurations are explained in more detail in the following forms.

[0015] (12) The vehicle braking system is in accordance with form (11), in which the hydraulic braking force and the electric braking force are formed at a given distribution coefficient.

[0016] In this form, the configuration of the interaction of hydraulic braking force and electric braking force is limited. In this form, the two braking forces are controlled according to a simple control rule, due to which it is possible to easily control the required braking force required for the vehicle as a whole. This form is effective when insufficient braking force (which is explained below) is covered by the hydraulic braking force and the electric braking force. In this case, the hydraulic braking force and the electric braking force to cover the insufficient braking force can easily be formed with appropriate, appropriate absolute values. The distribution coefficient can be fixed or it can be variable depending on some factor.

[0017] (13) A vehicle braking system according to form (11) or (12), further comprising a regenerative braking device provided for one of the front wheel and a rear wheel for which one of the hydraulic braking device and an electric braking device regenerative braking device is configured to generate regenerative braking force using the generation of electric power by rotating one of the front wheel and rear his wheels

- while the hydraulic braking force, the electric braking force and the regenerative braking force are controlled in such a way that they interact with each other.

[0018] In this form, the three braking forces interact with each other in order to form the braking force required for the vehicle as a whole. This form provides a brake system design that takes advantage of a regenerative braking device, in addition to the advantages of a hydraulic braking device and an electric braking device.

[0019] A vehicle braking system of this form includes a regenerative braking device, in addition to a hydraulic braking device and an electric braking device. The regenerative braking device is installed on vehicles driven by motor power, for example, on electric vehicles and hybrid vehicles. The regenerative braking device permits the motor to act as an electric generator in order to restore part of the kinetic energy of the vehicle as electrical power. Thus, the regenerative braking device generates the braking force to brake the vehicle. The absolute value of the braking force generated by the regenerative braking device, i.e. regenerative braking force varies depending on various factors such as the speed of the vehicle and the amount of battery charge in which electrical power is restored. The brake system of a vehicle of this form is advantageous in that the variation of the regenerative braking force is permitted by controlling the electric braking force, which ensures a good response. The three braking forces are jointly controlled, so that the required braking force is provided to the vehicle as a whole. Consequently, the vehicle braking system of this form provides high utility, in particular, when used for electric vehicles and hybrid vehicles.

[1420] (14) The vehicle braking system according to the form (13), in which the hydraulic braking force and the electric braking force are controlled so that the hydraulic braking force and the electric braking force cover an insufficient braking force that cannot be covered by regenerative braking the inadequate braking force is a shortage in the required total braking force, which is the braking force required for the vehicle as a whole.

[0021] This form is one example of the interaction of three braking forces. According to this form, a regenerative braking force is preferably formed, and the hydraulic braking force and the electric braking force are formed so as to cover the shortage in the required total braking force, which cannot be covered by the regenerative braking force. In other words, this form includes a constraint regarding the interaction of the three braking forces, namely, the constraints regarding the interaction of hydraulic braking force, electrical braking force and regenerative braking force. According to this form, the required required total braking force can be easily obtained due to the joint control of the three braking forces even in a situation in which, for example, the regenerative braking force varies.

[0022] c. Overcoming the variation of braking force

The following forms are intended to allow variation of the braking force, namely, the variation of one of the hydraulic braking force and the electric braking force.

[21] (21) The vehicle braking system according to any of the forms (1) to (14), in which in the case in which one of the hydraulic braking force and electric braking force varies, the other of the hydraulic braking force and electric braking force in such a way that it corresponds to variation.

[0024] In this form, the configuration of the interaction of hydraulic braking force and electric braking force is limited. According to this form, when one of the hydraulic braking force and the electric braking force varies or fluctuates, the other of the hydraulic braking force and the electric braking force changes according to the variation or fluctuation, thereby producing the necessary braking force of the vehicle. In particular, it is possible to properly overcome the variation of one of the hydraulic braking force and the electric braking force not by changing the braking force generated by one of the hydraulic braking device and the electric braking device that generates the braking force subject to variation, but by changing the braking force generated by means of another of the hydraulic braking device and an electric braking device (for example, a braking device The properties that form the braking force, not subject to variation). “A situation in which one of the hydraulic braking force and electric braking force varies” means a situation in which the hydraulic braking force or the electric braking force that is actually generated is greater or less, due to some reason, the hydraulic braking force or the electric braking force, which should be formed.

[0025] (22) The vehicle braking system according to the form (21), in which in the case in which one of the hydraulic braking force and the electric braking force is reduced, the other of the hydraulic braking force and the electric braking force changes.

[0026] When the braking force varies due to some reason, the braking force, which should actually be formed, tends to become less than the braking force, which should be formed, instead of becoming larger than it. According to this form, it is possible to overcome the variation of one of the hydraulic braking force and the electric braking force in a situation that is more likely to occur.

[0027] (23) The braking system of the vehicle according to the form (22), in which the other of the hydraulic braking force and the electric braking force is increased so that it covers the reduction of one of the hydraulic braking force and the electric braking force.

[0028] This form is one form to overcome a situation in which one of the hydraulic braking force and the electric braking force is reduced. In other words, this form is one configuration of the interaction of hydraulic braking force and electric braking force. According to this form, the reduction of one of the hydraulic braking force and the electric braking force is covered by the other of the hydraulic braking force and the electric braking force, thereby reducing or eliminating the reduction of the braking force that must be provided to the vehicle as a whole (hereinafter referred to as "full braking" force "if necessary). Here, “one of the hydraulic braking force and the electric braking force is reduced” means that one of the braking forces is less than the braking force to be generated, namely, one of the braking forces is insufficient. In this connection, “a situation in which one of the hydraulic braking force and electric braking force is reduced” is hereinafter referred to as “insufficient braking force situation” if necessary.

[0029] (24) The vehicle braking system according to the form (22), in which another of the hydraulic braking force and the electric braking force is reduced in accordance with a decrease in one of the hydraulic braking force and the electric braking force.

[0030] This form is another form to overcome a situation in which one of the hydraulic braking force and the electric braking force is reduced, i.e. insufficient braking force situation. In other words, this form is a different configuration of the interaction of hydraulic braking force and electric braking force. This form allows you to reduce or eliminate the change in the distribution of braking force on the front wheel and rear wheel. Therefore, it is possible to reduce or eliminate the change in sensation from the operation of pressing the brake pedal experienced by the driver.

[0031] (25) The vehicle braking system according to any of the forms (22) - (24) in which the other of the hydraulic braking force and the electric braking force changes in a situation in which one of the hydraulic braking force and the electric braking force decreases due delays increase one of the hydraulic braking force and electric braking force.

[0032] A situation in which a decrease in one of the hydraulic braking force and an electric braking force may be a situation in which one of the braking forces continues to decrease during the entire period of time during which one of the braking forces is generated. Additionally, the situation may be a situation in which one of the hydraulic braking force and the electric braking force becomes less than expected in the process of increasing one of the braking forces due to a delay in response to the increase. This form is suitable for overcoming the second situation.

[0033] (26) The vehicle braking system according to any of the forms (22) - (25), in which it is estimated that the vehicle is in a situation in which one of the hydraulic braking force and the electric braking force is reduced, based on at least one of the environment in which the vehicle is located, and the states of the constituent component of the brake system of the vehicle, and the other of the hydraulic braking force and the electric braking force varies based on the evaluation.

[0034] In this form, when the factors causing the reduction of one of the hydraulic braking force and the electric braking force are identified by means of determination or evaluation, the other of the hydraulic braking force and the electric braking force is changed. According to this form, it is possible to easily overcome the variation without determining the variation of the actual braking force. The degree of change of the other of the hydraulic braking force and the electric braking force can be determined in accordance with the degree of factors identified.

[0035] (27) The vehicle braking system according to form (26), in which it is estimated that the vehicle is in a situation in which one of the hydraulic braking force and the electric braking force is reduced, based on at least one of outside temperature, atmospheric pressure, temperature of the electric motor and battery voltage, made with the ability to supply electrical power to the electric motor.

[0036] In this form, the factors causing the reduction of one of the hydraulic braking force and the electric braking force, i.e. factors causing a situation of insufficient braking force. In the case in which the outside temperature is low, for example, the viscosity of the working fluid increases due to a decrease in the temperature of the working fluid of the hydraulic braking device. In this case, the response of the hydraulic braking force deteriorates, and the hydraulic braking force becomes less than expected during its increase. In the case in which the atmospheric pressure is low, the response of the hydraulic braking force deteriorates due to the low pressure of the working fluid in the tank, the low pressure in the chamber with the atmospheric pressure of the booster due to negative pressure, etc., when the pressure of the working fluid in the hydraulic brake increases . In this case, the response of the hydraulic braking force deteriorates, and the hydraulic braking force becomes less than expected during its increase. In the case in which the temperature of the electric motor is high, the protection circuit works, for example, and the supply current to the electric motor decreases. In this case, the electric braking force becomes less than expected in the process of its increase. In the case in which the battery voltage is lowered due to a decrease in charge, etc., the supply current to the electric motor decreases. In this case, the electric braking force becomes less than expected in the process of its increase. In this form, when any of such factors is identified, it is estimated that one of the hydraulic braking force and the electric braking force is reduced, based on the identification, and the other of the hydraulic braking force and the electric braking force changes in accordance with the decrease.

[0037] Each of the outside temperature and atmospheric pressure may be considered as one example of the environment in which the vehicle is housed. Each of the motor temperature and battery voltage can be considered as one example of the state of the constituent component of a vehicle's brake system. The outside temperature can be determined by an outside temperature sensor or can be obtained from information from a car navigation system. Atmospheric pressure can be determined by means of an atmospheric pressure sensor or can be obtained from information from a car navigation system. The temperature of the electric motor can be determined by a temperature sensor or can be estimated from the history of the movement of the electric motor. Battery voltage can be detected by a voltage sensor.

[0038] Although it belongs to this form, it can be estimated that one of the hydraulic braking force and the electric braking force is reduced based on the following factors, and the other of the hydraulic braking force and the electric braking force can be changed based on the evaluation. For example, a condition in which air bubbles are mixed in the flow of hydraulic fluid of a hydraulic braking device can be identified as one factor causing a decrease in hydraulic braking force, and the electric braking force can be changed based on identification. This condition can be identified by determining the temperature of the working fluid, estimating from the history of the movement of the hydraulic braking device, or estimating from the relationship between the working value of the working brake element and the pressure of the working fluid.

[0039] In a hydraulic braking device or an electric braking device made in the form of a disc braking device, the clearance between the disk rotor and the brake shoe may vary relatively significantly depending on the turning state of the vehicle in the state in which the brake shoe is significantly worn. For example, when a vehicle makes a very sharp turn, ground clearance becomes relatively large. In such a state, a delay in the formation of the braking force is expected. With this in mind, clearance can be assessed from the position of the piston, which pushes the brake shoe to the disc rotor. Additionally, high ground clearance can be identified as one factor causing the reduction of one of the hydraulic braking force and the electric braking force, and the other of the hydraulic braking force and the electric braking force can be changed based on the identification.

[0040] In the case in which an electric motor is used as a source of propulsion for a pressure pump, an amplifier, etc., in a hydraulic braking device, a high temperature of an electric motor and a low battery voltage configured to supply electric power to the electric motor identify as factors causing a decrease in hydraulic braking force, similar to an electric braking device. Electrical braking force may vary when factors are identified.

[0041] (28) The braking system of the vehicle according to any of the forms (22) - (25),

- in which one of the hydraulic braking force and electric braking force, which are actually formed, determined,

- it identifies, on the basis of the definition, that the vehicle is in a situation in which one of the hydraulic braking force and the electric braking force is reduced.

[0042] In this form, the factors causing a decrease in braking force are not identified. Instead, the actual braking force is determined, and the reduction of one of the hydraulic braking force and the electric braking force is overcome based on the determination. According to this form, a reduction in actual braking force is not identified on the basis of an estimate, so that the reduction is adequately overcome, regardless of the factors causing the decrease.

[0043] (29) The vehicle braking system according to form (28), in which another of the hydraulic braking force and the electric braking force varies based on the determined one of the hydraulic braking force and the electric braking force.

[0044] According to this form, the amount of change of the other of the hydraulic braking force and the electric braking force is determined based on the actual amount of reduction of one of the hydraulic braking force and the electric braking force, so that the reduction is more appropriately overcome. Here, a “magnitude reduction” may be considered as an insufficient magnitude of one of the braking forces relative to the magnitude of the braking force to be generated.

[0045] (30) A vehicle braking system according to any of the forms (21) - (29), further comprising a regenerative braking device provided for one of the front wheel and a rear wheel, for which one of the hydraulic braking devices is provided, configured to to form a hydraulic braking force, and an electric braking device, configured to generate an electric braking force, the regenerative braking device being configured to to form the regenerative braking force using the generation of electric power by rotating one of the front wheel and the rear wheel, for which the regenerative braking device is provided,

- wherein, when the switching operation is performed to increase one of the hydraulic braking force and the electric braking force while reducing the regenerative braking force, the other of the hydraulic braking force and the electric braking force changes so that it corresponds to variation in a situation in which braking force and electric braking force varies.

[0046] In this form, the vehicle braking system further includes a regenerative braking device. In most vehicles, the regenerative braking force generated by the regenerative braking device is designed to be replaced by another braking force, for example, at a time when the vehicle speed becomes very low. In particular, in the case in which (a) one of the hydraulic braking force and electric braking force and (b) the regenerative braking force is provided to one of the front wheel and the rear wheel, the regenerative braking force provided to one of the front wheel and the rear wheel is replaced one of the hydraulic braking force and electric braking force. This form is suitable for such a case. When one of the hydraulic braking force and the electric braking force varies in such a case, the other of the hydraulic braking force and the electric braking force provided to the other from the front wheel and the rear wheel changes, so that the variation is appropriately overcome.

[0047] d. The design of the hydraulic braking device

The following forms refer to the design of the hydraulic braking device.

[0048] (31) A vehicle braking system according to any of the forms (1) to (30), in which the hydraulic braking device includes:

- the body of rotation, made with the ability to rotate with one of the front wheel and rear wheel;

- friction element made with the ability to nestle on the body of rotation;

- wheel brake cylinder, made with the ability to work through the working fluid filed in it, to press the friction element to the body of rotation;

- a pump adapted to pressurize the working fluid and deliver the working fluid under pressure to the wheel brake cylinder; and

- a pressure maintenance valve designed to control the pressure of the working fluid in a controlled manner, which must be supplied to the wheel brake cylinder.

[0049] This form includes a restriction on the design of the hydraulic braking device. In most hydraulic braking devices made with the ability to control hydraulic braking force using a control valve, two types of control valves are used, i.e. a control valve to increase the pressure of the working fluid to be supplied to the wheel brake cylinder; and a control valve to reduce the pressure of the working fluid. In the hydraulic brake device of this form, on the contrary, the pressure of the working fluid to be supplied to the wheel brake cylinder is reduced, for example, by means of a pressure-maintaining valve, while the working fluid having a high pressure is directly supplied from the pump, so that the pressure of the working fluid maintained at target pressure. Thus, the hydraulic braking force is controlled by only one control valve, and not by two control valves. Therefore, the hydraulic braking device can have a compact size, and the vehicle brake system itself, respectively, can have a compact size.

[0050] (32) The vehicle braking system according to form (31), in which the hydraulic braking device further includes:

- a master cylinder including (a) a piston connected to a working braking element, and (b) an injection chamber in which pressure is pumped on the working fluid introduced into it by moving the piston, the main cylinder being configured to pressurize working fluid through the work force applied by the driver to the working brake element;

- the main fluid line, through which the working fluid, to which the pressure in the pressure chamber of the main cylinder is pressurized, is supplied to the wheel brake cylinder; and

- valve open / close, made with the ability to open and close the main line for the liquid,

- wherein the wheel brake cylinder operation by means of the working fluid supplied from the master cylinder, and the wheel brake cylinder operation by means of the working fluid fed from the pump are selectively set based on the operating mode of the open / close valve.

[0051] In the hydraulic braking device according to this form, the formation of the hydraulic braking force, which depends on the driver's working force through the master cylinder, and the formation of the hydraulic braking force by the pump and the pressure-maintaining valve, regardless of the working force, is switchable. According to this form, when an electrical failure occurs in a hydraulic braking device, a hydraulic braking force is generated, which depends on the work force, which results in a vehicle braking system that is excellent in terms of fault tolerance. In the case in which the solenoid valve is used as an open / close valve, it is preferable, from the point of view of fault tolerance, to use a normally open solenoid valve, namely, a solenoid valve configured to open the main liquid line in a state in which the electric current is not served, i.e. able without power supply.

[0052] (33) The braking system of the vehicle according to the form (32)

- in which the hydraulic braking device includes: a tank that contains the working fluid and from which the pump pumps the working fluid; and a fluid channel in the tank that connects the tank and the pump, and

- wherein the pressure maintenance valve allows part of the working fluid to be supplied from the pump to the wheel brake cylinder to pass through the pressure maintaining valve in order to regulate the pressure of the working fluid and part of the working fluid that passes through the pressure maintenance valve flows into tank or channel for fluid in the tank.

[0053] In the hydraulic braking device of this form, the working fluid ejected from the pump effectively returns through the pressure-maintaining valve in the state in which the hydraulic braking force is generated. For higher efficiency, the working fluid that passes through the pressure-maintaining valve preferably flows into the fluid channel in the tank rather than into the tank. In the case in which the working fluid that passes through the pressure-maintaining valve is configured to flow into the fluid channel in the tank, it is desirable that the working fluid be configured to flow into the fluid channel in the tank at a position near the pump. This form is applicable to a form that does not use a master cylinder, as well as a form that uses a master cylinder.

[0054] (34) The vehicle braking system according to the form (33), in which the hydraulic braking device includes a shut-off valve, configured to cut off the flow of working fluid in the tank or the channel for the fluid in the tank when the wheel brake cylinder works by working fluid fed from the master cylinder in the state in which the open / close valve is open.

[0055] According to the hydraulic braking device of this form, the flow of working fluid, which must be supplied to the wheel brake cylinder, to the tank when the hydraulic braking force, which depends on the working force, is effectively prevented From the point of view of fault tolerance for electrical failure, in the case in which the solenoid valve is used as a shut-off valve, it is desirable to use a normally closed solenoid valve, i.e. an electromagnetic valve made with the ability to cut off the flow of the working fluid in a state in which electric current is not supplied to it, i.e. able without power supply.

[0056] (35) The braking system of the vehicle according to the form (33) or (34), in which the tank is located near the main cylinder, and the pressure in the discharge chamber of the main cylinder is pressurized to the working fluid.

[0057] In the hydraulic braking device of this form, we can assume that the tank for the main cylinder and the tank for the pump are set common to each other. Additionally, we can assume that the pump uses a tank for the main cylinder and pumps the working fluid from the tank. In a hydraulic braking device of this form, only one tank is needed, even when the hydraulic braking device is equipped with a master cylinder. Thus, the hydraulic braking device has a compact size.

[0058] (36) The vehicle braking system according to any of the forms (32) - (35), in which the hydraulic braking device includes a pedal travel resistance simulator provided in the main fluid line and adapted to provide an operation braking operation. at the same time providing the working brake element with a counteracting force in accordance with the operation of the working brake element when the wheel brake cylinder is operated by means of a working fluid supplied from Sosa in the condition in which the opening / closing valve is closed.

[0059] When the opening / closing valve is closed to form a hydraulic braking force by activating the pump, the working fluid to which the pressure in the master cylinder is pressurized is not applied anywhere, and the working stroke of the working brake element does not occur. Consequently, the feel of the brake pedal operation deteriorates. To eliminate the drawback, a simulator of resistance to pedal travel is provided in a hydraulic braking device. According to this form, the working braking element can work with a good feeling even in a situation in which a hydraulic braking force is formed that does not depend on the working force applied to the working braking element. The simulator resistance to movement of the pedal can be of any known construction. For example, a pedal-to-travel simulator may include: a fluid chamber that communicates with a main fluid path and the volume of which is variable; and an elastic body, adapted to apply, to the working fluid in the fluid chamber, a force in accordance with the magnitude of the increase in the fluid chamber volume.

[0060] (37) The vehicle braking system according to any of the forms (31) - (36), in which a pump and a pressure maintenance valve of a hydraulic braking device are included in an actuator module.

[0061] In the hydraulic braking device of this form, the pump and the pressure maintenance valve are unified so as to provide a single module, i.e. actuator module. The actuator module helps reduce the size of the hydraulic braking device. The actuator module may have a structure in which, for example, a motor is activated to activate the pump. Additionally, the actuator module preferably includes a fluid passage that connects the constituent components, such as a pump and a pressure maintenance valve, to each other. In the case in which the hydraulic braking device includes an open / close valve and a shut-off valve described above, these valves may be included in the actuator module. A hydraulic braking device is provided for one of the front wheel and the rear wheel, due to which the actuator module has a relatively compact size.

[0062] (38) The vehicle braking system according to any of the forms (31) - (37), in which the pressure-maintaining valve is a linear solenoid valve, configured to reduce the pressure of the working fluid to be supplied to the wheel brake cylinder, to pressure in accordance with the electric current supplied to the linear solenoid valve.

[0063] According to this form, a linear solenoid valve for reducing the pressure of the working fluid is used as a pressure maintaining valve, thereby easily and accurately controlling the hydraulic braking force, which must be generated by a hydraulic braking device.

Brief Description of the Drawings

[0064] The objectives, features, advantages, and technical and industrial significance of the present disclosure should be better understood by reading the following detailed description of embodiments when considered in connection with the accompanying drawings, in which:

FIG. 1 is a view conceptually showing the overall construction of a vehicle braking system according to a first embodiment;

FIG. 2 is a hydraulic circuit diagram of a brake hydraulic system of a vehicle braking system shown in FIG. one;

FIG. 3A is a cross-sectional view of a wheel brake of a hydraulic brake device of a vehicle braking system shown in FIG. 1, and FIG. 3B is a cross-sectional view of a wheel brake of an electric brake device of a vehicle braking system shown in FIG. one;

FIG. 4 is a graph showing the vehicle speed ratio used when the regenerative braking force is replaced by the hydraulic braking force during a vehicle deceleration process;

FIG. 5 is a graph showing changes with the passage of time, regenerative braking force, hydraulic braking force and electric braking force generated by the basic control, the changes being caused by the progress of the brake pedal operation;

FIG. 6A is a graph showing the variation of the hydraulic braking force, and FIG. 6B and 6C are graphs showing that the electrical braking force varies to overcome variation;

FIG. 7A is a graph showing the variation of the electric braking force, and FIG. 7B and 7C are graphs showing that the hydraulic braking force varies to overcome variation;

FIG. 8 shows graphs, respectively, indicating an ambient temperature coefficient, an atmospheric pressure ratio, and a gradient ratio of hydraulic braking force, which are used to estimate the magnitude of the decrease in hydraulic braking force

FIG. 9 shows graphs, respectively, indicating a motor temperature coefficient, a battery voltage ratio, and an electric brake force gradient ratio, which are used to estimate the magnitude of the electrical brake force reduction;

FIG. 10 is a flowchart showing the braking force control program executed in a vehicle braking system of the first embodiment;

FIG. 11 is a flowchart showing the nested procedure for preprocessing in the braking force control program of FIG. ten;

FIG. 12 is a flow chart showing the nested procedure for determining the required regenerative braking force in the braking force control program of FIG. ten;

FIG. 13A is a flowchart showing an embedded procedure for estimating the magnitude of the reduction in hydraulic braking force, and FIG. 13B is a flow chart showing the nested procedure for estimating the amount of electrical braking force reduction in the braking force control program of FIG. ten;

FIG. 14 is a view conceptually showing the general construction of a vehicle braking system according to a second embodiment;

FIG. 15A is a graph showing the variation of the hydraulic braking force, which is determined, and FIG. 15B and 15C are graphs showing that the electrical braking force varies to overcome a certain variation;

FIG. 16A is a graph showing the variation of the electric braking force, which is determined, and FIG. 16B and 16C are graphs showing that the hydraulic braking force varies to overcome a certain variation;

FIG. 17 is a flowchart showing the braking force control program executed in the vehicle braking system of the second embodiment;

FIG. 18 is a view conceptually showing the general construction of a vehicle braking system according to a third embodiment;

FIG. 19 is a hydraulic circuit diagram of a brake hydraulic system of a vehicle braking system shown in FIG. 18; and

FIG. 20 is a flowchart of the method, conceptually showing control of braking forces in a vehicle braking system of the third embodiment.

Detailed description of embodiments

[0065] With reference to the drawings, embodiments of the brake system of a vehicle are explained in more detail according to the various forms indicated above and modifications of the embodiments. It should be understood that the vehicle braking system according to the present disclosure is not limited to the details of the embodiments below and the forms described in the “Various forms” section, and may be modified and modified based on the knowledge of those skilled in the art.

Option 1 implementation

[0066] A. Overview of the vehicle drive system and vehicle brake system

As schematically shown in FIG. 1, the vehicle on which the vehicle braking system is installed according to the first embodiment is a hybrid vehicle having two front wheels 10F and two rear wheels 10R, and two front wheels 10F are driving wheels. First, the vehicle drive system is explained. A vehicle drive system mounted on a real vehicle includes an engine 12 as a source of propulsion, a generator 14, which acts primarily as an electric generator, a power distribution mechanism 16 to which the engine 12 and generator 14 are connected, and an electric motor 18 as another source of propulsion.

[0067] The power distribution mechanism 16 has the function of distributing the rotation of the engine 12 to the rotation of the generator 14 and the rotation of the output shaft. The motor 18 is connected to the output shaft through the gear mechanism 20, acting as a gearbox. The rotation of the output shaft is transmitted to the front left and right wheels 10F through the differential mechanism 22 and the corresponding drive shafts 24L, 24R, so that the front left and right wheels 10F rotate with the possibility of actuation. The generator 14 is connected to the battery 28 via an inverter 26G. The electric power obtained by generating the electric power of the generator 14 is accumulated in the battery 28. The electric motor 18 is connected to the battery 28 via an inverter 26M. The motor 18 and the generator 14 are controlled by controlling the inverter 26M and the inverter 26G.

[0068] As schematically shown in FIG. 1, the vehicle braking system of the first embodiment mounted on the vehicle includes (a) a regenerative braking device 30 configured to provide braking force to each of the two front wheels 10F, (b) a hydraulic braking device 32 made with the ability to provide braking force to each of the two rear wheels 10R, and (c) an electric braking device 34 configured to provide braking force to each of the two front wheels 10F, not depending on the braking force provided by the regenerative braking device 30. In the vehicle braking system, hydraulic braking device 32 is provided not for both of the front wheels 10F and rear wheels 10R, but only for the rear wheels 10R. Thus, the hydraulic braking device 32 is compact, and the vehicle brake system itself, respectively, is compact.

[0069] B. The design of the regenerative braking device

From the point of view of the equipment, the regenerative braking device 30 forms part of the drive system of the vehicle. When the vehicle decelerates, the electric motor 18 rotates by rotating the front wheels 10F without receiving power supply from the battery 28. The electric motor 18 generates electric power using the electromotive force generated by its rotation, and the electric power generated is accumulated through an inverter 26M in the battery 28 as the quantity of electricity (which may also be referred to as an “electrical quantity” or “electrical charge”). Thus, the electric motor 18 acts as an electric generator, so that the battery 28 is charged. The rotation of the front wheels 10F slows down, namely, the vehicle slows down by an amount corresponding to the energy that corresponds to the charged electrical quantity. In the present vehicle, the regenerative braking device 30 has this configuration. The braking force provided by the regenerative braking device 30 in the front wheels 10F (hereinafter referred to as “regenerative braking force” if necessary) depends on the amount of electrical power generated, and the regenerative braking force generated is controlled by controlling the 26M inverter. A detailed explanation of the regenerative braking device 30 is omitted, since any regenerative braking device having a known conventional design can be used as a regenerative braking device 30.

[0070] C. Design of a hydraulic braking device

i) General construction

The hydraulic braking device 32 includes (a) a master cylinder 42, to which the brake pedal 40 is connected, as an operating brake element to be controlled by the driver, (b) an actuator module 44, configured to allow the working fluid from the master cylinder 42 to pass through itself, in order to supply working fluid, or made with the ability to regulate the pressure of the working fluid, to which pressure is pressurized by means of its pump (which is explained below), with in order to supply the working fluid, and (c) two wheel brakes 46, respectively, provided for the right and left rear wheels 10R and configured to slow down the rotation of the respective right and left rear wheels 10R by means of the pressure of the working fluid supplied from the actuator module 44. The hydraulic braking device 32 is a device with two systems or a tandem type, corresponding to the right and left rear wheels 10. Actuator module 44 can be considered as a braking actuator, in which many component components are unified. The actuator module 44 acts as a pressure regulator, configured to control the pressure of the working fluid and supply the working fluid with a regulated pressure.

[0071] ii) Master Cylinder Design

As shown in FIG. 2, the master cylinder 42 is a device with a tandem-type cylinder, comprising, in the housing, two pistons 42a, arranged in series and connected to the brake pedal 40, and two pressure chambers 42b, each of which is connected to the working fluid, pressure is generated by moving the corresponding one of the pistons 42a. The tank 48, which contains the working fluid at atmospheric pressure, is located near the main cylinder 42. The working fluid from the tank 48 is pressurized in each of the two injection chambers 42b. The master cylinder 42 is configured to supply, to the actuator module 44, a working fluid whose pressure corresponds to the force applied to the brake pedal 40 (hereinafter referred to as the “working braking force” if necessary) for the respective two systems that correspond to the respective two rear wheels 10R. In particular, the actuator module 44 has fluid channels through which the working fluid supplied from the master cylinder 42 flows to the respective wheel brakes 46. Thus, the hydraulic braking device 32 has two fluid channels through which the working fluid flows from the main cylinder 42 to the corresponding wheel brakes 46, i.e. into the two main lines 50 for fluid. In the hydraulic braking device 32, the working fluid may be supplied from the master cylinder 42 to the wheel brakes 46 via the respective main fluid lines 50. Each of the wheel brakes 46 has a wheel brake cylinder (which is explained below) and the working fluid is supplied to the wheel brake cylinder.

[0072] One of the two main lines 50 for fluid connects the pedal travel resistance simulator 54 through the simulator opening valve 52, which is a normally closed solenoid open / close valve. In the normal operating condition, in which no electrical equipment failure occurs, the simulator opening valve 52 is energized with the valve open, so that the pedal travel resistance simulator 54 operates. In normal operating condition, the two main shut-off valves 56, which are opening / closing solenoid valves and which are provided in the actuator module 44 in such a way that they correspond to two systems, are transferred to the closed state of the valve, so that the pedal-drag simulator 54 permits the stroke of the pedal 40 brakes and provides, pedals 40 brakes, opposing labor in accordance with the course of pressing. Thus, simulator 54 resistance to the movement of the pedal has the function of improving the feeling of the operation of pressing the brake pedal, experienced by the driver in normal working condition. The simulator 54 resistance to the movement of the pedals of this embodiment has a known construction. For example, simulator 54 resistance to the movement of the pedal includes: a fluid chamber, which communicates with the main line 50 for the liquid, and the volume of which is variable; and an elastic body, adapted to apply, to the working fluid in the fluid chamber, a force in accordance with the magnitude of the increase in the fluid chamber volume. Thus, the simulator 54 resistance to the movement of the pedal is not explained in detail here.

[0073] iii) Design of the actuator module

The actuator module 44 includes: two main shut-off valves 56, each of which acts as a normally open electromagnetic open / close valve, configured to open and close the respective two main liquid lines 50; two pumps 60, which correspond to two systems; motor 62 for driving pumps 60; two pressure maintenance valves 64 (pressure control valves), each of which acts as a linear solenoid valve, corresponding to two systems; two shut-off valves 66, each of which acts as a normally closed electromagnetic open / close valve located in series with the respective pressure-maintaining valves 64; and two control valves 68 arranged in parallel with the respective pressure maintenance valves 64. In the hydraulic braking device 32, only one tank is provided, and two pumps 60 are configured to pump working fluid from the tank 48. To this end, a channel 69 is formed for the liquid in the tank that connects the two pumps 60 and the tank 48, and part of the channel 69 for fluid in the tank is located in the module 44 of the actuator. Each of the pumps 60 is connected to a respective main fluid line 50 on the outlet side and delivers, to a respective wheel brake 46, a working fluid under pressure through a part of the main fluid line 50. On the output side of each pump 60, a buffer 70 is provided to reduce the pulsating change in pressure of the working fluid ejected from the corresponding pump 60. In the actuator module 44, two return channels 71 are formed, each of which is parallel with the corresponding pump 60 and connects the corresponding main line 50 for the liquid and the channel 69 for the liquid in the tank between them. A pressure maintenance valve 64 and a shut-off valve 66 are provided on each of the two return channels 71. The pressure maintenance valve 64 has the function of controlling the pressure of the working fluid to be supplied to the wheel brake 46. With this in mind, the pressure maintenance valve 64 may also be referred to as "valve pressure regulation. " The shut-off valve 66 has the function of shutting off the working fluid, which is to be supplied to the wheel brake 46. With this in mind, the shut-off valve 66 may also be referred to as a “shut-off valve”.

[0074] In normal operating condition, the main shut-off valves 56 are in the closed state of the valve, while the shut-off valves 66 are in the open state of the valve. When the pumps 60 are driven by the motor 62, pressure is pressurized to the working fluid in the tank 48, and the working fluid under pressure is supplied to the wheel brakes 46. Each pressure-maintaining valve 64 has the function of controlling the pressure of the working fluid to be supplied to the respective wheel brake 46 , to a pressure in accordance with the electric current supplied to the pressure maintenance valve 64. In other words, each pressure maintenance valve 64 is designed as a linear solenoid valve to reduce pressure, having the function of reducing the pressure of the working fluid to be supplied to the wheel brake 46. In the hydraulic braking device 32, the working fluid whose pressure is regulated by maintaining control valves 64 pressure applied to the wheel brakes 46 regardless of the pressure of the working fluid supplied from the master cylinder 42, namely, regardless of the working braking force, applying brake pedal 40. The pressure maintenance valve 64 is a pressure reduction valve, and the working fluid passes through the pressure maintenance valve 64 to adjust the pressure. The working fluid that passes through each pressure maintenance valve 64 returns to the fluid channel 69 in the tank and, accordingly, to the tank 48 through the corresponding return channel 71 and the corresponding shut-off valve 66 when the valve is open.

[0075] In the case in which hydraulic brake device 32 is subject to electrical failure, the main shut-off valves 56 are brought to the open state of the valve, while the shut-off valves 66 are turned to the closed state of the valve, so that the working fluid supplied from the master cylinder 42 the actuator module 44 is supplied to the wheel brakes 46. In other words, when the wheel brake cylinders (which are explained below) operate by means of a working fluid supplied from the main cylinder 42 in a state in which m main shut-off valves 56, each of which acts as an opening / closing valve are opened, each shutoff valve 66 shuts off flow of hydraulic fluid into the tank 48 or the channel 69 for fluid reservoir. Two pressure sensors in the wheel brake cylinder 72 and two pressure sensors 74 in the master cylinder are provided in such a way that they correspond to the two systems. Each pressure sensor in the wheel brake cylinder 72 is configured to determine the pressure of the working fluid, which must be supplied to the corresponding wheel brake 46 (hereinafter referred to as "pressure in the wheel brake cylinder" if necessary). Each pressure sensor 74 in the master cylinder is configured to determine the pressure of the working fluid supplied from the master cylinder 42 (hereinafter referred to as "the pressure in the master cylinder" if necessary).

[0076] iv) Wheel Brake Design

Each wheel brake 46 for stopping the rotation of the respective rear wheel 10R is a disc brake device schematically shown in FIG. 3A. Each wheel brake 46 includes a disc rotor 80, as a rotating body configured to rotate with a respective rear wheel 10R, and a caliper 82 supported rotatably by a carrier that holds the rear wheel 10R rotatably. The caliper 82 includes a wheel brake cylinder 84, the body of which is defined by part of the caliper 82. A pair of brake pads 88, each of which acts as a friction element, is provided so that one brake pad 88 is attached and held by the far end of the wheel piston 86 brake cylinder 84, and another brake shoe 88 is attached and held by means of a portion of the caliper 82 located opposite its portion, which includes a wheel brake cylinder 84. Taki In this way, two brake pads 88 are located opposite each other, with the disc rotor 80 being placed between them.

[0077] The working fluid is supplied from the actuator module 44 to the fluid chamber 90 of the wheel brake cylinder 84, and the pressure of the working fluid causes the brake pads 88 to clamp the disc rotor 80 between them. Thus, the wheel brake cylinder 84 operates with the ability to force the brake pads 88 to push on the disc rotor 80. Thus, each wheel brake 46 forms a braking force using the friction force to stop the rotation of the corresponding rear wheel 10R, i.e. braking force in order to brake the vehicle (hereinafter referred to as “hydraulic braking force” if necessary). Hydraulic braking force has an absolute value in accordance with the pressure of the working fluid supplied from the module 44 of the actuator. The wheel brakes 46 are of conventional design, and their detailed explanation is omitted.

[0078] In the hydraulic braking device 32, the pressure of the working fluid to be supplied to the wheel brake cylinder 84 is reduced by means of the pressure maintenance valve 64, while the working fluid having a high pressure is directly supplied from the pump 60, whereby the pressure working fluid is maintained equal to the target pressure. Thus, the hydraulic braking force, which must be generated by each wheel brake 46, is controlled by only one control valve, and not by two control valves. Therefore, the module 44 of the actuator of the hydraulic braking device 32 is of a compact size, so that the hydraulic braking device as a whole, respectively, has a compact size. Additionally, the vehicle's braking system itself has a compact size.

[0079] D. Design of the electric braking device

As shown in FIG. 1, the electric braking device 34 includes a pair of wheel brakes 100 for stopping the rotation of the respective front wheels 10F. As shown in FIG. 3B, each wheel brake 100 is similar in construction to the wheel brakes 46 of the hydraulic braking device 32. Each wheel brake 46 operates by means of the working fluid pressure, while each wheel brake 100 is operated by the power of an electric motor.

[0080] Each wheel brake 100 includes a disc rotor 102, as a rotational body configured to rotate with a respective front wheel 10F and a caliper 104 supported to be movable by a carrier that holds the corresponding front wheel 10F rotatably. The caliper 104 includes an electrical actuator 106. The electrical actuator 106 includes (a) a plunger 108 held by the caliper 104 so that it is extendable and retractable, (b) a threaded rod 110 that is held by the caliper 104 such in a manner that is non-rotatable, and in such a way that it is extendable and retractable relative to the disk rotor 102, and which has an external thread formed on the outer circumference, (c) a nut 112, which has a morning thread that is held in engagement with the external thread of the threaded rod 110 and which is held by the caliper 104 in such a way that it is rotating and in such a way that it is not extendable and retractable relative to the disk rotor 102 and, (d) the electric motor 114, configured to rotate the nut 112. The electric motor 114 includes: magnets 116 connected to the outer circumference of the nut 112; and coils 118 held by the caliper 104.

[0081] A pair of brake pads 120, each of which acts as a friction element, is provided in such a way that one brake shoe 120 is attached and held by the far end of the plunger 108 of the electric actuator 106, and the other brake shoe 120 is attached and held by the caliper section 104, located opposite its section, in which the electrical actuator 106 is located. Thus, two brake pads 120 are located opposite each other , The disc rotor 102 located therebetween. The electric actuator 106 is configured such that the brake pads 120 are pushed onto the disk rotor 102 by rotating the electric motor 114 as the driving source. In other words, the electric actuator device 106 includes a mechanism consisting of a plunger 108, a threaded rod 110 and a nut 112, namely, a motion conversion mechanism for moving the friction elements by means of the power of the electric motor 114. Thus, each wheel brake 100 of the electric brake device 34 controls the force that must be generated by the motor 114, and applies force as a force to stop or slow down the rotation of the wheel through the movement conversion mechanism I.

[0082] Thus, each wheel brake 100 of the electric braking device 34 forms, using friction force, a braking force in order to stop the rotation of the respective front wheel 10F, namely the braking force to brake the vehicle (hereinafter referred to as "electric braking force" if necessary). The electric braking force depends on the pushing force, by means of which the brake shoe 120 is pushed by the plunger 108. Each wheel brake 100 has a pushing force sensor 122, as a load sensor, provided between the plunger 108 and the brake shoe 120 to determine the pushing force. The wheel brakes 100 are of conventional design and their detailed explanation is omitted. As shown in FIG. 1, electric current is supplied to the electric motor 114 of each wheel brake 100 from the auxiliary battery 124, which is different from the battery 28.

[0083] E. the management of the brake system of the vehicle

i) Controller

The control of the present braking system, namely, the control of the braking force F, is performed by the electronic control module 130 (ECU), as the controller shown in FIG. 1. (The corresponding braking forces are collectively referred to as “braking force F” if necessary). ECU 130 includes a computer and actuators (actuators, drivers) for the components to be controlled. In particular, the ECU 130 controls the inverters 26G, 26M, which constitute the regenerative braking device 30, the pressure maintenance valves 64 of the actuator module 44, which constitute the hydraulic braking device 32, and the electric brakes 114 of the wheel brakes 100, which constitute the electric braking device 34, due to by controlling the regenerative braking force F _RG , hydraulic braking force F _HY and electric braking force F _EM . Therefore, the total braking force F _SUM , which is the braking force F, which must be provided to the vehicle as a whole, is controlled.

[0084] ii) Overview of Basic Management

With basic control of a true braking system, the required total braking force F _SUM ^* , which is the braking force F required for the vehicle as a whole (i.e. the sum of the braking forces F to be provided in four wheels 10), is determined based on the operation pressing the brake pedal 40. In particular, the brake pedal 40 comprises a work force sensor 132 for detecting the work force δ of pressing the brake pedal 40, as shown in FIG. 1 and 2. ECU 130 obtains the required full braking force F _SUM ^* by multiplying the work force δ determined by the working force sensor 132 by the braking force coefficient α _F. The work force δ is one example of a work value indicating the degree of operation of pressing the brake pedal 40, namely indicating the degree of operation of pressing the brake pedal, and can be considered as a parameter indicating the required full braking force F _SUM ^* .

[0085] In the present braking system, a regenerative braking force F _{RG is} preferably generated, and the hydraulic braking force F _HY and the electrical braking force F _EM cover the lack of the required full braking force F _SUM ^* , which cannot be covered by the regenerative braking force F _RG . The shortage is called "insufficient braking force F _IS ". The regenerative braking force F _RG , the hydraulic braking force F _HY and the electric braking force F _EM correspond to the sum of the braking forces F that must be provided in two wheels 10, i.e. two front wheels 10F or two rear wheels 10R, respectively, via a regenerative braking device 30, a hydraulic braking device 32 and an electric braking device 34. In fact, each of the two front wheels 10F or each of the two rear wheels 10R is provided, half of the regenerative braking force F _RG , half the hydraulic braking force F _HY and half the electric braking force F _EM . For brevity, the two front wheels 10F are considered as a virtual single front wheel 10F, and the two rear wheels 10R are considered as a virtual single rear wheel 10R, and the following explanation is given with the understanding that the regenerative braking force F _RG , hydraulic braking force F _HY and an electric braking force F _{EM is} provided to one 10F front wheel or one 10R rear wheel.

[0086] Below, control of the braking force F is specifically explained. Initially, the maximum regenerative braking force F _RG-MAX , which is the regenerative braking force F _RG that can be generated at this time, is identified based on the state of charge (SOC) of the battery 28, the driving speed vehicle etc. In the case in which the required total braking force F _SUM ^* is equal to or less than the maximum regenerative braking force F _RG-MAX , the required regenerative braking force F _RG ^* , which is the regenerative braking force F _RG , which is required, is defined as the required total braking force F _SUM ^* . On the other hand, in the case in which the required total braking force F _SUM ^* exceeds the maximum regenerative braking force F _RG-MAX , the required regenerative braking force F _RG ^* is defined as the maximum regenerative braking force F _RG-MAX .

[0087] Then, the insufficient braking force F _IS is determined by subtracting the required regenerative braking force F _RG ^* from the required total braking force F _SUM ^* . By appropriately multiplying the insufficient braking force F _IS by the hydraulic braking force distribution coefficient β _HY and the electric braking force distribution coefficient β _EM (β _HY + β _EM = 1), the required hydraulic braking force F _HY ^* , which is the hydraulic braking force F _HY , is determined , which must be formed, and the required electric braking force F _EM ^* , which is the electric braking force F _EM , which must be formed. Here, the coefficient β _{HY of} the hydraulic braking force distribution serves to obtain the magnitude of the hydraulic braking force F _HY , which must be distributed to the rear wheel 10R, and the coefficient β _{EM of the} distribution of the electric braking force serves to derive the electric braking force F _EM , which must be distributed 10F front wheel.

[0088] The regenerative braking device 30, the hydraulic braking device 32 and the electric braking device 34 are controlled based on the required regenerative braking force F _RG ^* , the required hydraulic braking force F _HY ^* and the required electric braking force F _EM ^* , defined as described above whereby the total braking force F _SUM based on the required total braking force F _SUM ^{* is} provided to the vehicle. The required regenerative braking force F _RG ^* , the required hydraulic braking force F _HY ^* and the required electric braking force F _EM ^* can be considered as targets for the braking force F, which must be generated, respectively, by the regenerative braking device 30, hydraulic braking device 32 and electric brake device 34. In this sense, these braking forces F _RG ^* , F _HY ^* and F _EM ^* , respectively, may be referred to as the target regenerative braking force, the target hydraulic braking force th force and target electrical braking force.

[0089] When the vehicle speed v is below the threshold speed v ₀ (for example, 10 km / h) at the time of the start of the brake pedal operation, namely, at the beginning of the brake pedal 40, the regenerative braking force F _{RG is} not formed until the end of this brake pedal operation. When the vehicle speed v is lower than the threshold speed v ₀ as a result of the brake pedal operation, the regenerative braking force F _RG , which is formed, gradually decreases to 0, so that it is replaced by the hydraulic braking force F _HY before the transport speed v means becomes equal to the threshold speed v ₁ (e.g., 5 km / h) below the threshold speed v _0, and the hydraulic braking force F _HY gradually increased by an amount corresponding to the amount regenerative reduction first braking force F _RG. In other words, a switching operation is performed in which the hydraulic braking force F _{HY is} increased, while the regenerative braking force F _RG is reduced. In particular, the vehicle speed coefficient C _RG (v), which uses the vehicle speed v as a parameter, is set as shown in the graph of FIG. 4. By multiplying the required regenerative braking force F _RG ^* by the coefficient C _RG (v) of the vehicle speed, the magnitude dF _{RG of} reducing the regenerative braking force is determined. By subtracting the dF _RG value of reducing the regenerative braking force from the required regenerative braking force F _RG ^* and summing the dF _RG value of reducing the regenerative braking force with the required hydraulic braking force F _HY ^* , the required regenerative braking force F _RG ^* and the required hydraulic braking force F _{HY are} corrected ^* . It should be noted that the threshold speed v ₀ , used at the beginning of the brake pedal operation, and the threshold speed v ₀ , used when the vehicle’s speed v becomes lower, may differ from each other.

[0090] FIG. 5 shows one example of changes, with the passage of time, the regenerative braking force F _RG , the hydraulic braking force F _HY and the electric braking force F _EM , formed according to the basic control described above, and the changes are caused as the brake pedal operation is performed. FIG. 5 also shows the change in the required total braking force F _SUM ^* . FIG. 5 shows the changes in the event that the brake pedal depressing operation starts when the vehicle speed v is above the threshold speed v ₀ and if the required full braking force F _SUM ^* exceeds the maximum regenerative braking force F _RG-MAX .

[0091] In the example shown in FIG. 5, when the required total braking force F _SUM ^{* is} increased after the brake pedal operation has been started, the required full braking force F _SUM ^{* is} covered by the regenerative braking force F _RG before the regenerative braking force F _RG exceeds the maximum regenerative braking force F _{RG-MAX ..} From the point in time when the regenerative braking force F _RG exceeds the maximum regenerative braking force F _RG-MAX , the hydraulic braking force F _HY and the electric braking force F _EM are formed at a distribution coefficient tion (β _HY : β _EM ) based on the coefficient β _{HY of} the hydraulic braking force distribution and the electric braking force distribution coefficient β _EM in order to cover the insufficient braking force F _IS . In the period from the time when the vehicle speed v becomes lower than the threshold speed v ₀ , until the time when the vehicle speed v becomes equal to the threshold speed v ₁ as the brake pedal is pressed, the regenerative braking force F _RG decreases, and the hydraulic braking force F _{HY is} increased by the amount of reduction of the regenerative braking force F _RG . At the end of the brake pedal operation, the required total braking force F _SUM ^* is reduced, and the hydraulic braking force F _HY and the electric braking force F _EM are reduced.

[0092] According to the basic control explained above, the regenerative braking force F _{RG is} preferably formed, and the hydraulic braking force F _HY and the electric braking force F _EM cover the lack of the required total braking force F _SUM ^* , which cannot be covered by the regenerative braking force F _{The RG} , namely the hydraulic braking force F _HY and the electric braking force F _EM, cover the insufficient braking force F _IS . Additionally, the hydraulic braking force F _HY and the electric braking force F _EM are formed at a given distribution coefficient (β _HY : β _EM ). In other words, the regenerative braking force F _RG , the hydraulic braking force F _HY and the electric braking force F _EM interact as described above in the braking system of the present embodiment.

[0093] iii) Variation of hydraulic braking force and variation of electric braking force

The hydraulic braking force F _HY and the electric braking force F _EM may vary or fluctuate due to the environment in which the vehicle is placed and the state of the constituent components of the hydraulic braking device 32 and the electric braking device 34. For example, when the vehicle is placed in a low temperature the temperature of the working fluid decreases, and the viscosity of the working fluid, respectively, increases. In this case, the response of the hydraulic braking force F _HY deteriorates and the hydraulic braking force F _HY becomes less than the required hydraulic braking force F _HY ^* to some extent in the process of increasing the hydraulic braking force F _HY . When the vehicle moves in the high-altitude region, the pressure of the working fluid in the tank 48 decreases, so that the hydraulic braking force F _HY becomes less than the required hydraulic braking force F _HY ^* to some extent during the process of increasing the hydraulic braking force F _HY . For example, due to a delay in increasing the hydraulic braking force F _HY , the hydraulic braking force F _HY decreases during its increase, for example, when the brake pedal operation starts or when the vehicle speed v decreases below the threshold speed v ₀ , as shown in . 6A.

[0094] When the temperature of the electric motor 114 of the electric brake device 34 rises, the protection circuit operates in such a way as to reduce the supply current to the electric motor 114. Additionally, when the charge state (SOC) of the auxiliary battery 124 for supplying the electric current to the electric motor 114 decreases, the auxiliary voltage the battery 124, respectively, decreases, the current supply to the motor 114 is reduced. In the case in which the supply current to the electric motor 114 is reduced, the speed of movement of the plunger 108 becomes low, and the electric braking force F _EM , respectively, becomes less than the required electric braking force F _EM ^* to some extent. For example, due to the delay in increasing the electric braking force F _EM , the electric braking force F _EM decreases in the process of increasing it, namely when the brake pedal operation starts, as shown in FIG. 7A. In each wheel brake 100, the external thread of the threaded rod 110 and the internal thread of the nut 112 are maintained in engagement with each other, and therefore the difference between the positive efficiency (direct efficiency) and the negative efficiency (inverse efficiency) is large. Thus, even if the supply current to the motor 114 decreases, the electric braking force F _EM in a stationary state does not decrease.

[0095] iv) Measures to overcome the reduction in hydraulic braking force and reduce the electric braking force

This vehicle braking system, in the case of personification, identifies factors that cause the variation of the hydraulic braking force F _HY and the variation of the electric braking force F _EM , namely, the factors causing the reduction of hydraulic braking force F _HY and the reduction of the electric braking force F _EM That the vehicle is in a situation in which one of the hydraulic braking force F _HY and the electric braking force F _EM varies, that is, decreases. Additionally, the present braking system modifies, based on evaluation, another of the hydraulic braking force F _HY and the electric braking force F _EM . In other words, in a situation of insufficient braking force, in which the hydraulic braking force F _HY and the electric braking force F _EM is insufficient, the real braking system overcomes the situation.

[0096] As shown in FIG. 1, the present braking system is equipped with an ambient temperature sensor 134 for determining the ambient temperature T _E , which is the temperature of the environment in which the vehicle is located, an atmospheric pressure sensor 136 for determining the atmospheric pressure P _A, and a battery voltage sensor 138 for determining the voltage V _{B of the} battery, which is the output voltage of the auxiliary battery 124. As shown in FIG. 3B, the present braking system is additionally equipped with motor temperature sensors 140, each of which is intended to determine the temperature T _{M of the} motor, which is the temperature of the electric motor 114 of each wheel brake 100 of the electric braking device 34. Based on certain values of these sensors, 134, 136, 138, 140 gradient change ΔF _HY hydraulic braking force which is the gradient of changes required hydraulic braking force F _HY ^*, and the gradient of change ΔF _EM electrical braking force, which is tsya gradient changes required electrical braking force F _EM ^*, estimated value dF _HY reduce the hydraulic braking force which is a quantity of reduction of the hydraulic braking force F _HY, and the amount dF _EM decreasing the electrical braking force, which is a value decreasing the electrical braking force F _EM. Here, the gradient ΔF _{HY of} change in hydraulic braking force can be considered as the rate of increase of the required hydraulic braking force F _HY ^* in the process of increasing it, and the gradient ΔF _{EM of} changing the electric braking force can be considered as the rate of increase of the required electric braking force F _EM ^* in the process of increasing it . Additionally, the hydraulic braking force reduction value dF _HY may be considered as an insufficient value relative to the required hydraulic braking force F _HY ^* , and the electric brake force reduction dF _EM may be considered as an insufficient value relative to the required electric braking force F _EM ^* .

[0097] As shown in the graphs of FIG. 8, ambient temperature coefficient C _TE (T _E ), which uses ambient temperature T _E as a parameter, coefficient C _PA (P _A ) of atmospheric pressure, which uses atmospheric pressure P _A as a parameter, and coefficient C _ΔFHY (ΔF _HY ) The gradient of change in hydraulic braking force, which uses the gradient ΔF _HY change in hydraulic braking force as a parameter, is set as data in the form of a map. These coefficients are obtained by referring to the data based on the determined or obtained ambient temperature T _E , atmospheric pressure P _A and gradient ΔF _{HY of the} change in hydraulic braking force. The ambient temperature coefficient C _TE (T _E ), atmospheric pressure coefficient C _PA (P _A ), and the gradient of hydraulic brake force coefficient C _ΔFHY (ΔF _HY ) are multiplied by the required hydraulic braking force F _HY ^* . Additionally, the difference obtained by subtracting such a result obtained from the required hydraulic braking force F _HY ^* is estimated as dF _{HY of} the hydraulic braking force reduction. As is apparent from FIG. 8, the ambient temperature coefficient C _TE (T _E ) is set to a value less than 1 when the ambient temperature T _{E is} below the threshold temperature T _E0 (for example, 5 ° C), and the atmospheric pressure coefficient C _PA (P _A ) is equal to the value less than 1 when the atmospheric pressure P _{A is} below the threshold pressure P _A0 (for example, 1 hPa). Thus, when the ambient temperature T _{E is} below the threshold temperature T _E0 , and when the atmospheric pressure P _{A is} below the threshold pressure P _A0 , in the present braking system it is considered that there are factors causing a decrease in the hydraulic braking force F _HY . It should be noted that for the hydraulic braking force F _HY , it becomes more difficult to follow the increase in the required hydraulic braking force F _HY ^* as the gradient ΔF _{HY of the} change in hydraulic braking force becomes large. With this in mind, the coefficient C _ΔFHY (ΔF _HY ) of the gradient of change in hydraulic braking force is set to a value less than 1 when it exceeds the threshold gradient ΔF _HY0 .

[0098] As shown in the graphs of FIG. 9, the motor temperature coefficient C _TM (T _M ), which uses the motor temperature T _M as a parameter, the battery voltage coefficient C _VB (V _B ), which uses the battery voltage V _B as a parameter, and the coefficient C _ΔFEM (ΔF _EM ) electric brake force gradient change, which uses the gradient ΔF _{EM of} the electric brake force change as a parameter, is set as data in the form of a map. These coefficients are obtained with reference to the data based on the determined or obtained temperature T _{M of the} motor, voltage V _{B of the} battery and gradient ΔF _{EM of the} change in electrical braking force. The motor temperature coefficient C _TM (T _M ), battery voltage coefficient C _VB (V _B ), and gradient ratio C _ΔFEM (ΔF _EM ) of the electric brake force are multiplied by the required electric braking force F _EM ^* . Additionally, the difference obtained by subtracting such a result obtained from the required electric braking force F _EM ^* is estimated as dF _{EM of} the electric braking force reduction. As is apparent from FIG. 9, the motor temperature coefficient C _TM (T _M ) is set to a value less than 1 when the motor temperature T _{M is} higher than the threshold temperature TM ₀ (for example, 50 ° C), and the battery voltage coefficient C _VB (V _B ) is equal to the value less than 1 when the voltage V _{B of the} battery is below the threshold voltage VB ₀ (for example, 11 V). Thus, when the temperature T _{M of the} motor is above the threshold temperature TM ₀ , and when the voltage V _{B of the} battery is below the threshold voltage V _{B 0} , in the present braking system it is considered that there are factors causing a decrease in the electric braking force F _EM . It should be noted that for the electric braking force F _EM , it becomes more difficult to follow the increase in the required electric braking force F _EM ^* as the gradient ΔF _{EM of the} change in electric braking force becomes large. With this in mind, the coefficient C _ΔFEM (ΔF _EM ) of the gradient of change of the electric braking force is set to a value less than 1 when it exceeds the threshold gradient ΔF _EM0 .

[0099] The required electric braking force F _EM ^* and the required hydraulic braking force F _HY ^* , respectively, are changed based on such an estimated dF _HY value of the hydraulic braking force reduction and the dF _EM value of the electric braking force reduction, so that the required electric braking force F _EM ^* and the required hydraulic braking force F _HY ^{* are} adjusted. Correction is performed in the selected one of the two modes, i.e. supplement mode and equilibrium mode.

[0100] In the addition mode, when it is estimated that the hydraulic braking force F _HY decreases, the required electric braking force F _EM ^* increases by the amount dF _{HY of} the hydraulic braking force reduction, as shown in FIG. 6b. In addition, when it is estimated that the electric braking force F _{EM is} reduced, the required hydraulic braking force F _HY ^{* is} increased by the amount dF _{EM of} the electric braking force reduction, as shown in FIG. 7b. In the supplement mode, a decrease in hydraulic braking force F _HY and a decrease in electrical braking force F _EM are supplemented, so that it is possible to reduce or prevent the reduction of the total braking force F _SUM due to the decrease in hydraulic braking force F _HY and the electric braking force F _EM .

[0101] In the equilibrium mode, when it is estimated that the hydraulic braking force F _HY decreases, the required electric braking force F _EM ^* is reduced by an amount corresponding to the dF _HY value of the hydraulic braking force reduction, as shown in FIG. 6C. In particular, the result of the product, which is obtained by multiplying the dF _HY value of reducing the hydraulic braking force by the ratio (β _EM / β _HY ) of the coefficient _{EM of the} distribution of the electric braking force relative to the coefficient β _{HY of the} distribution of the hydraulic braking force, is subtracted from the required electric braking force F _EM ^* . When it is estimated that the electric braking force F _{EM is} reduced, the required hydraulic braking force F _HY ^* is reduced by an amount corresponding to the electric braking force dF _EM , as shown in FIG. 7C. In particular, the result of the product, which is obtained by multiplying the dF _{EM of} the electric braking force reduction by the ratio (β _HY / β _EM ) of the hydraulic braking force distribution coefficient β _HY relative to the electric braking force distribution coefficient β _EM , is subtracted from the required hydraulic braking force F _HY ^* . In the equilibrium mode, it is possible to decrease or prevent changes in the distribution of the braking force F to the front wheel 10F and rear wheel 10R, thereby reducing or preventing the change in sensation from the brake pedal operation experienced by the driver.

[0102] In the present braking system, it is estimated that factors causing variations in the hydraulic braking force F _HY and the electric braking force F _EM exist without actually determining the variations, and the electric braking force F _EM and the hydraulic braking force F _HY vary in accordance with degrees of factors. Thus, the present braking system easily overcomes the variation of the hydraulic braking force F _HY and the electric braking force F _EM .

[0103] v) Sequence of control operations

The present vehicle braking system is controlled such that the computer of the ECU 130 repeatedly executes the braking force control program shown by means of the flow chart of FIG. 10, with a short step, for example, from several ms to several ms. Next, a sequence of operations for controlling the braking force in the present braking system is explained on the basis of an explanation of the processing according to the control program.

[0104] In the processing according to the braking force control program, the pre-processing was initially performed in step 1. (Later in this document, step 1 is abbreviated as "S1", and other steps are abbreviated similarly). The preprocessing is performed by executing a nested preprocessing procedure, indicated by the flowchart of FIG. 11. In preprocessing, at S21, it is initially determined which of the two modes is selected with respect to the correction of the hydraulic braking force F _HY and the electric braking force F _EM . Although not illustrated, a mode selection switch that should be controlled by the driver is provided on the dashboard of the vehicle. The determination on S21 is made based on the state of the switch. When the add mode is selected, the mode flag M is set to 0 in S22. When the equilibrium mode is selected, the M mode flag is set to 1 in S23. Then, in S24, the work force δ, which is applied to the brake pedal 40, is obtained based on the determined value of the work force sensor 132. In S25-S29, the vehicle speed v is obtained based on the determined value of the vehicle speed sensor 142 (FIG. 1), the ambient temperature T _{E is} obtained based on the determined value of the ambient temperature sensor 134, the atmospheric pressure P _{A is} obtained based on the determined sensor value 136 atmospheric pressure, the motor temperature T _{M is} obtained based on the determined value of the sensor 140 of the motor temperature, and the battery voltage V _{B is} obtained based on the determined value of the sensor 138 voltage battery

[0105] After the pre-processing is completed, the required total braking force F _SUM ^* is determined by S2 by multiplying the obtained work force δ by the given braking force coefficient α _F. Then, at S3, the required regenerative braking force F _RG ^* is determined based on the determined required total braking force F _SUM ^* before determining the required hydraulic braking force F _HY ^* and the required electric braking force F _EM ^* . Processing to determine the required regenerative braking force F _RG ^* is performed by performing a nested procedure to determine the required regenerative braking force indicated by the flowchart of FIG. 12.

[0106] When processing according to a nested procedure for determining the required regenerative braking force, at S31, it is initially determined whether equal or less than 0 or not a certain required total braking force F _SUM ^* . A state in which the required total braking force F _SUM ^* is 0 indicates a state in which the brake pedal operation is not performed. When the brake pedal push operation is not performed, the regenerative braking force non-generating flag S is reset to S32. The regenerative braking non-generating flag is set to 1 when the regenerative braking force F _RG should not be generated.

[0107] Thereafter, in S33, it is determined whether or not the brake pedal operation starts. In particular, it is determined that the operation of pressing the brake pedal starts when the operation of pressing the brake pedal is not performed before the current program execution, and the operation of pressing the brake pedal is performed by the current execution of the program. When it is determined that the operation of depressing the brake pedal begins, at S34, it is determined whether or not the vehicle speed V is lower than the threshold speed v ₀ . When it is determined that the vehicle movement speed v is below the threshold speed v ₀ , the regenerative braking force non-formation flag is set to 1 at S35, and it is determined that the regenerative braking non-formation flag value is 1. Then, at S37, the required regenerative the braking force F _RG ^* is determined to be 0, and the regenerative braking force F _{RG is} controlled so that it does not form in the current sequence of the brake pedal operation. On the other hand, when it is determined that the vehicle speed v is equal to or higher than the threshold speed v ₀ , the regenerative braking force non-generating flag value is maintained at 0, and the corresponding regenerative braking force F _RG is generated in the current brake pedal operation by S38 and the following stages.

[0108] The processing in S38 and the following steps is explained below. In S38, the maximum regenerative braking force F _RG-MAX , which is the regenerative braking force F _RG that can be generated at the moment, is identified based on the state of charge (SOC) of the battery 28, the vehicle speed v, etc. Thereafter, at S39, it is determined whether the required total braking force F _SUM ^{* or the} maximum regenerative braking force F _RG-MAX is equal to or less. When the required total braking force F _SUM ^* is equal to or less than the maximum regenerative braking force F _RG-MAX , the required full braking force F _SUM ^* may be covered by the regenerative braking force F _RG . In this case, the required regenerative braking force F _RG ^* is determined to be equal to the required full braking force F _SUM ^* at S40. On the other hand, when the required total braking force F _SUM ^* exceeds the maximum regenerative braking force F _RG-MAX , the required regenerative braking force F _RG ^* is determined equal to the maximum regenerative braking force F _RG-MAX on S41 in order to form the regenerative braking force F _RG as large as possible.

[0109] When the vehicle slows down as a result of the brake pedal pressing operation, and the vehicle speed v, respectively, falls below the threshold speed v ₀ , correction processing of the required regenerative braking force F _RG ^* is performed to replace the regenerative braking force F _RG by hydraulic braking force F _HY . In the correction processing, the vehicle speed coefficient C _RG (v) in accordance with the vehicle speed v is identified with reference to the map data shown in S42 of FIG. 4. Then, the regenerative braking force reduction value dF _RG is determined in S43 by multiplying the required regenerative braking force F _RG ^* by the vehicle speed ratio C _RG (v). In S44, a certain amount of dF _RG reducing the regenerative braking force is subtracted from the required regenerative braking force F _RG ^* , thereby correcting the required regenerative braking force F _RG ^* .

[0110] After the required regenerative braking force F _RG ^* is determined by processing according to a nested procedure for determining the required regenerative braking force, the insufficient braking force F _IS is determined in S4 by subtracting the required regenerative braking force F _RG ^* from the required total braking force F _SUM ^* . Then, at S5, the insufficient braking force F _IS is multiplied by the hydraulic brake force distribution coefficient β _HY , and the regenerative braking force reduction dF _{RG is} summed with the result of the product, thereby determining the required hydraulic braking force F _HY ^* . By multiplying the insufficient braking force F _IS by the electric braking force distribution coefficient β _EM , the required electric braking force F _EM ^* is determined by S6.

[0111] In S7, given the reduction in hydraulic braking force F _HY due to the presence of the factors mentioned above, the dF _HY value of reducing the hydraulic braking force is estimated as a shortage of hydraulic braking force F _HY , which should actually be generated relative to the required hydraulic braking force F _HY ^* . The evaluation is performed by performing a nested procedure to estimate the magnitude of the decrease in hydraulic braking force, indicated by the flowchart of FIG. 13A. When processing according to the nested procedure, the gradient ΔF _{HY of the} change in hydraulic braking force is initially obtained at S51 based on the difference between the required hydraulic braking force F _HY ^* during the previous program execution (i.e. the required hydraulic braking force F _HY ^* determined at S5 at the previous execution) and the required hydraulic braking force F _HY ^* during the current program execution. In S52-S54, the ambient temperature coefficient C _TE (T _E ), the atmospheric pressure coefficient C _PA (P _A ) and the gradient of hydraulic braking force change coefficient C _ΔFHY (ΔF _HY ) are identified, respectively, based on the ambient temperature T _E , P _A and the gradient ΔF _HY change the hydraulic braking force by referring to the map data shown in FIG. 8. In S55, the dF _HY value of the decrease in hydraulic braking force is estimated as follows. The identified ambient temperature coefficient C _TE (T _E ), atmospheric pressure coefficient C _PA (P _A ), and the gradient of hydraulic brake force coefficient C _ΔFHY (ΔF _HY ) are multiplied by the required hydraulic braking force F _HY ^* , and the result of the product is subtracted from the required hydraulic braking force F _HY ^* . Thus, the dF _HY value of the decrease in hydraulic braking force is estimated.

[0112] In S8, taking into account the reduction of the electric braking force F _EM due to the presence of the factors mentioned above, the dF _{EM of} the electric braking force reduction is estimated as a shortage of the electric braking force F _EM , which should actually be generated relative to the required electric braking force F _EM ^* . The evaluation is performed by performing a nested procedure for estimating the amount of electrical braking force reduction indicated by the flowchart of FIG. 13B. When processed according to the nested procedure, the gradient ΔF _{EM of the} change in the electric braking force is initially obtained at S61 based on the difference between the required electric braking force F _EM ^* during the previous execution of the program (i.e. the required electric braking force F _EM ^* determined at S6 at the previous execution) and the required electric braking force F _EM ^* during the current program execution. In S62-S64, the motor temperature coefficient C _TM (T _M ), the battery voltage coefficient C _VB (V _B ) and the electric brake force gradient coefficient C _ΔFEM (ΔF _EM ) are identified, respectively, based on the motor temperature T _M , voltage V _{B of the} battery and the gradient ΔF _EM changes the electric braking force by referring to the map data shown in FIG. 9. In S65, the dF _EM value of the electrical brake force reduction is estimated as follows. The identified motor temperature coefficient C _TM (T _M ), battery voltage coefficient C _VB (V _B ) and coefficient C _ΔFEM (ΔF _EM ) of the electric brake force gradient are multiplied by the required electric brake force F _EM ^* , and the result of the product is subtracted from the required electric braking force f _em ^* . Thus, the magnitude of dF _{EM of} the electrical brake force reduction is estimated.

[0113] Returning to the flowchart of FIG. 10, in S9, it is determined whether or not the flag M of mode 1 is equal, namely, whether the currently selected mode is the addition mode or the equilibrium mode. When the complement mode is selected, the electric brake force reduction dF _{EM is} summed with the required hydraulic braking force F _HY ^* at S10, and the hydraulic brake force reduction dF _{HY is} summed with the required electric braking force F _EM ^* at S11. Thus, the required hydraulic braking force F _HY ^* and the required electric braking force F _EM ^{* are} adjusted. On the other hand, when the equilibrium mode is selected, the result of the product is: the dF _EM values of the electrical braking force reduction; and the ratio β _HY / β _EM (which is the ratio of the coefficient β _{H of the} distribution of the hydraulic braking force to the coefficient β _{EM of the} distribution of the electric braking force) is subtracted from the required hydraulic braking force F _HY ^* at S12. Additionally, the result of the product: the dF _HY values reduce the hydraulic braking force; and the β _EM / β _HY ratio (which is the ratio of the electric braking force distribution coefficient β _EM to the hydraulic braking force distribution coefficient β _HY ) is subtracted from the required electric braking force F _EM ^* at S13. Thus, the required hydraulic braking force F _HY ^* and the required electric braking force F _EM ^{* are} adjusted.

[0114] Thereafter, in S14, a control command based on such a determined and corrected required regenerative braking force F _RG ^* , a required hydraulic braking force F _HY ^* and a required electric braking force F _EM ^* is output to the regenerative braking device 30, the hydraulic braking device 32 and the electric braking device 34. Thus, the processing sequence according to the program is completed.

Option 2 implementation

[0115] A. the design of the brake system of the vehicle

As shown in FIG. 14, the vehicle on which the brake system is installed according to the second embodiment is not a hybrid vehicle. The vehicle drive system mounted on the vehicle of the second embodiment includes the engine 12 as the driving source, the transmission mechanism 150, the differential mechanism 22 and the drive shafts 24L, 24R and is adapted to drive the right and left front wheels 10F. The present braking system includes a hydraulic braking device 32 and an electric braking device 34 without activating the regenerative braking device. In the following explanation, references with numbers identical to those used in the first embodiment are used to identify devices and constituent components of the second embodiment, having functions identical to those of the devices of the first embodiment, and their detailed explanation goes down. The vehicle braking system according to this second embodiment also takes advantage of reducing the size of the hydraulic braking device 32 and the vehicle braking system, as indicated in the illustrated first embodiment.

[0116] The hydraulic braking device 32 and the electric braking device 34 of the second embodiment are almost identical in design to the hydraulic braking device and the electric braking device of the vehicle braking system of the first embodiment. In the braking system of the second embodiment, the hydraulic braking device 32 is configured to provide hydraulic braking force to the front wheel 10F, and the electric braking device 34 is configured to provide the electric braking force to the rear wheel 10R.

[0117] B. Vehicle Brake Control

i) Management Overview

The braking force F is controlled in the present braking system, namely, the hydraulic braking force F _HY and the electric braking force F _{EM are} controlled by the ECU 130. In the following explanation, processing that is identical to the processing when controlling the vehicle braking system of the first embodiment, not explained.

[0118] In controlling the present braking system, the required total braking force F _SUM ^* is determined by multiplying the work force δ determined by the working force sensor 132 by the braking force coefficient α _F The determined required total braking force F _SUM ^{* is} distributed to the required hydraulic braking force F _HY ^* and the required electric braking force F _EM ^* . The distribution is performed based on the distribution coefficient (β _HY : β _EM ) based on the coefficient β _{HY of the} distribution of the hydraulic braking force and the coefficient β _{EM of the} distribution of the electric braking force.

[0119] As explained above, the hydraulic braking force and electric braking force can vary or fluctuate due to the environment in which the vehicle is located and the state of the constituent components of the hydraulic braking device 32 and the electric braking device 34. In the vehicle braking system of the first embodiment estimated the presence of factors causing variation and variation of one of the hydraulic braking force F _HY and the electric braking force F _EM overcoming It is affected by changing the other of the hydraulic braking force F _HY and the electric braking force F _EM according to the degree of factors. In the braking system of the second embodiment, the variation of one of the hydraulic braking force F _HY and the electric braking force F _{EM is} overcome based on the actually determined braking force F. Therefore, in the present braking system, variation can be adequately overcome by identifying the reduction of the actual braking force not based on an assessment, in other words, regardless of the presence of factors causing the variation.

[0120] In particular, the reduction in hydraulic braking force F _{HY is} identified as follows. The actual hydraulic brake force F _{HY is} obtained based on the pressure PW in the wheel brake cylinder, which is the pressure of the working fluid applied to the wheel brake cylinder 84 of the wheel brake 46. When the difference δF _{HY is the} hydraulic brake force which is the difference between the hydraulic brake force F _HY and the required hydraulic braking force F _HY ^* exceeds the threshold difference δF _HY-TH in the process of increasing the required total braking force F _SUM ^* , it is identified that the hydraulic braking force F _{HY is} less the required hydraulic braking force F _HY ^* due to a delay in increasing the hydraulic braking force F _HY .

[0121] Similarly, the reduction of the electric braking force F _{EM is} identified as follows. The actual electric brake force F _{EM is} obtained on the basis of a push load W that is applied to the disc rotor 102 by means of the brake shoe 120 of the wheel brake 100. When the difference δF _{EM is the} electric brake force which is the difference between the electric brake force F _EM and the required electric brake force F _EM ^* exceeds the threshold difference δF _EM-TH in the process of increasing the required total braking force F _SUM ^* , it is identified that the electric braking force F _{EM is} less than the required electric braking oh force F _EM ^* due to the delayed increase in the electric braking force F _EM .

[0122] Similar to the vehicle braking system of the first embodiment, reducing the hydraulic braking force F _HY and reducing the electric braking force F _{EM is} overcome differently between the supplement mode and the equilibrium mode. In the add-on mode, the reduction of the hydraulic braking force F _{HY is} overcome by summing the difference δF _{HY of the} hydraulic braking force with the required electric braking force F _EM ^* , thereby correcting the required hydraulic braking force F _HY ^* . In the equilibrium mode, the result of the product is: the ratio β _EM / β _HY (which is the ratio of the coefficient β _{EM of the} distribution of the electric braking force to the coefficient β _{HY of the} distribution of the hydraulic braking force); and the hydraulic brake force difference δF _HY is subtracted from the required electric braking force F _EM ^* , thereby correcting the required hydraulic braking force F _HY ^* . Similarly, in the add-on mode, the reduction of the electric braking force F _{EM is} overcome by summing the difference δF _{EM of the} electric braking forces with the required hydraulic braking force F _HY ^* , thereby correcting the required electric braking force F _EM ^* . In the equilibrium mode, the result of the product is: the ratio β _HY / β _EM (which is the ratio of the coefficient β _{HY of the} distribution of the hydraulic braking force to the coefficient β _{EM of the} distribution of the electric braking force); and the electric brake force difference δF _EM is subtracted from the required hydraulic braking force F _HY ^* , thereby correcting the required electric braking force F _EM ^* .

[0123] When the reduction of the hydraulic braking force F _HY shown in FIG. 15A, identified by the processing described above, the electric braking force F _{EM is} increased, as shown in FIG. 15B in a complement mode, while the electric braking force F _EM is reduced, as shown in FIG. 15C in equilibrium mode. When the decrease in electrical braking force F _EM shown in FIG. 16A, identified by the processing described above, the hydraulic braking force F _{HY is} increased, as shown in FIG. 16B in a complement mode, while the hydraulic braking force F _HY is reduced, as shown in FIG. 16C in equilibrium mode.

[0124] iii) Sequence of control operations

The control of the present vehicle braking system is performed in such a way that the computer of the ECU 130 repeatedly executes the braking force control program indicated by the flowchart of FIG. 17, with a short step, for example, from several ms to several ms. Next, a sequence of operations for controlling the braking force in the present braking system is explained on the basis of an explanation of the processing according to the control program. The following briefly explains parts of the processing in the brake system of a vehicle of the second embodiment, which are identical parts of the processing in the brake system of a vehicle of the first embodiment.

[0125] In processing according to the braking force control program, the work force δ is obtained at S101, and the required total braking force F _SUM ^* is determined at S102 by multiplying the work force δ by the braking force coefficient α _F. Then, at S103, the required hydraulic braking force F _HY ^* is determined by multiplying the required total braking force F _SUM ^* by the coefficient β _{HY of} the hydraulic braking force distribution, and the required electric braking force F _EM ^* is determined by multiplying the required total braking force F _SUM ^* by electrical brake force distribution coefficient β _EM .

[0126] Then, in S104, it is determined whether or not the required total braking force F _SUM ^{* is} in an increase process, based on the required total braking force F _SUM ^* in the previous program execution and the required total braking force F _SUM ^* in the current program execution. When the required total braking force F _SUM ^* is in the process of increasing, S105 and the following steps are implemented to overcome the reduction of the hydraulic braking force F _HY and the reduction of the electric braking force F _EM .

[0127] At S105, the actual hydraulic braking force F _{HY is} based on the pressure PW in the wheel brake cylinder, and the actual electrical braking force F _{EM is} obtained based on the pushing load W of the brake pad 120. At S106, the resulting hydraulic braking force F _HY is subtracted the required hydraulic braking force F _HY ^* , and the resulting actual electric braking force F _EM is subtracted from the required electric braking force F _EM ^* , resulting in the difference δF _{HY of the} hydraulic braking force and the difference δF _EM e Electric braking forces.

[0128] Thereafter, in S107, it is determined whether the mode is to overcome the reduction of the hydraulic braking force F _HY and the reduction of the electric braking force F _EM is a supplement mode or equilibrium mode. When the mode is an add-on mode, S108-S111 are implemented. When the mode is an equilibrium mode, S112-S115 are implemented.

[0129] In the addition mode, in S108, it is determined whether or not the difference δF _{HY of the} hydraulic braking forces exceeds the threshold difference δF _HY-TH . When the difference δF _HY hydraulic brake force exceeds the threshold difference δF _HY-TH, the sequence control process proceeds to S109, to summarize the difference δF _HY hydraulic brake force with the required electrical braking force F _EM ^*, whereby the adjusted desired electric braking force F _EM ^* . At S110, it is determined whether or not the difference δF _EM electric brake force threshold difference δF _EM-TH. When the difference δF _EM electric brake force exceeds the threshold difference δF _EM-TH, sequence control flow goes to S111, to summarize the difference δF _EM electric brake force to the required hydraulic braking force F _HY ^*, whereby the corrected required hydraulic braking force F _HY ^* . In the equilibrium mode, at S112, it is determined whether or not the difference δF _{HY of the} hydraulic braking forces exceeds the threshold difference δF _HY-TH . When the difference δF _HY hydraulic brake force exceeds the threshold difference δF _HY-TH, the sequence control process proceeds to S113, in which the product of the result: the relationship β _EM / β _HY (which is a ratio coefficient β _EM distribution of the electrical braking force to the coefficient β _HY distribution hydraulic braking force); and the difference δF _{HY of the} hydraulic braking forces is subtracted from the required electric braking force F _EM ^* , thereby correcting the required electric braking force F _EM ^* . At S114,, it is determined whether or not the difference δF _EM electric brake force threshold difference δF _EM-TH. When the difference δF _EM electric brake force exceeds the threshold difference δF _EM-TH, the sequence control process proceeds to S115, where the result is the product: ratio β _HY / β _EM (which is a ratio coefficient β _HY distribution of hydraulic brake force to the coefficient β _EM distribution of electric braking force); and the electric brake force difference δF _EM is subtracted from the required hydraulic braking force F _HY ^* , thereby correcting the required hydraulic braking force F _HY ^* .

[0130] In S116, a control command based on such a determined and corrected required hydraulic braking force F _HY ^* and the required electric braking force F _EM ^* is output to the hydraulic braking device 32 and the electric braking device 34. Thus, the processing sequence according to the program is completed.

Option 3 implementation

[0131] A. Overview of the vehicle drive system and vehicle brake system

As schematically shown in FIG. 18, the vehicle on which the vehicle braking system is mounted according to the third embodiment (hereinafter referred to as “the vehicle of the third embodiment” if necessary) is a hybrid vehicle, such as a vehicle on which the vehicle braking system is installed according to the first embodiment (hereinafter referred to as the “vehicle of the first embodiment”). The vehicle drive system according to the third embodiment is substantially similar to the vehicle drive system of the first embodiment. In the following explanation, references with numbers identical to those used in the first embodiment are used to identify the constituent components of the third embodiment having functions identical to those of the first embodiment, and their detailed explanation is omitted. In contrast to the control in the vehicle drive system installed on the vehicle of the first embodiment, control in the vehicle drive system installed on the vehicle of the third embodiment is performed by a monopole hybrid electronic control module 160 (hereinafter referred to as "HB-ECU" if necessary). In particular, HB-ECU 160 includes a computer and actuation circuits (actuators) for the components of the vehicle drive system that are to be controlled. The HB-ECU 160 controls, for example, the amount of charge of the battery 28 and controls the 26M inverter, 26G inverter.

[0132] As schematically shown in FIG. 18, the vehicle braking system of the present embodiment includes (a) a regenerative braking device 30 configured to provide braking force to each of the two front wheels 10F, (b) a hydraulic braking device 32 configured to provide braking force to each of the two the front wheels 10F, regardless of the braking force provided by the regenerative braking device 30, and (c) the electric braking device 34, configured to provide ive braking force to each of the two rear wheels 10R. Thus, unlike the vehicle brake system of the first embodiment, in which hydraulic brake device 32 is provided for rear wheels 10R, and electric brake device 34 is provided for front wheels 10F, hydraulic brake device 32 is provided for front wheels 10F, and electric brake the device 34 is provided for the rear wheels 10R in the vehicle braking system of the third embodiment, similarly to a transport braking system deleterious means of the second embodiment.

[0133] B. Regenerative braking device

The regenerative braking device 30 of the vehicle braking system of the present embodiment is substantially similar in design to the regenerative braking device 30 of the braking system of the vehicle of the first embodiment. However, the regenerative braking force is controlled by the HB-ECU 160.

[0134] C. Hydraulic braking device

The hydraulic braking device 32 of the vehicle braking system of the present embodiment (hereinafter referred to as the “hydraulic braking device 32 of the present embodiment) is substantially similar in design and function to the hydraulic braking device 32 of the vehicle braking system of the first embodiment (hereinafter referred to as the“ hydraulic braking device 32 of the first embodiment "), with the exception of the wheels that are provided with gi equal braking force. The actuator module 44 is slightly different between the hydraulic brake device 32 of the present embodiment and the hydraulic brake device of the first embodiment 32. In particular, as shown in Fig. 19, check valves 162 are provided in the module 44 of the hydraulic brake actuator 32 of the present embodiment, instead of buffers 70 provided in the actuator module 44 (FIG. 2) a hydraulic braking device 32 of the first embodiment. Additionally, the check valves 68 provided in the actuator module 44 of the hydraulic braking device 32 of the first embodiment are omitted in the actuator module 44 of the hydraulic braking device 32 of the present embodiment. Also in the vehicle braking system of the present embodiment, it is possible to take advantage of the reduced size of the hydraulic braking device.

[0135] D. Electric braking device

The electric braking device 34 of the vehicle braking system of the present embodiment is substantially similar in construction and function to the electric braking device 34 of the braking system of the vehicle of the first embodiment, with the exception of the wheels which are provided with an electric braking force.

[0136] E. the control of the brake system of the vehicle

i) Control system

The control of the vehicle braking system of the present embodiment, namely, the control of the braking force F, is performed by the control system shown in FIG. 18. In particular, the hydraulic braking device 32 is controlled by the electronic control module 164 for the hydraulic braking device (hereinafter referred to as “HY-ECU”). The electric braking device 34 is controlled by electronic control modules 166 provided for the respective wheel brakes 100 (hereinafter referred to as "EM-ECU"). HY-ECU 164 includes a computer and means of actuation (actuation circuits) for components of a hydraulic braking device 32. EM-ECU 166 includes a computer and means of actuation (actuating circuits) for components of an electric braking device 34. As explained above, the regenerative braking device 30 is controlled by the HB-ECU 160.

[0137] In particular, HB-ECU 160 controls the inverters 26G, 26M which constitute the regenerative braking device 30, the HY-ECU 164 controls the valves 64 to maintain the pressure of the actuator module 44, which constitutes the hydraulic braking device 32, and EM-ECU 166, accordingly, the electric motors 114 of the respective wheel brakes 100, which constitute the electric braking device 34, are controlled, thereby controlling the regenerative braking force F _RG , the hydraulic braking force F _HY and the electric braking force F _EM . Therefore, the total braking force F _SUM , which is the braking force F, which must be provided to the vehicle as a whole, is controlled. In the vehicle braking system, HB-ECU 160, HY-ECU 164 and EM-ECU 166 are interconnected by means of a network in a vehicle (CAN) and perform the appropriate types of control when communicating with each other. As explained below, the HY-ECU 164 acts, in the present vehicle braking system, as the main electronic control module that also controls the HB-ECU 160 and EM-ECU 166. We can assume that one controller consists of the HB-ECU 160, HY-ECU 164 and EM-ECU 166.

[0138] ii) Basic braking force control

The basic braking force control in a real vehicle braking system is performed conceptually, as shown in the flow chart of FIG. 20. The following explains the basic braking force control based on the flow chart. Processing based on the flowchart of the method is repeatedly performed in a short time step, for example, approximately several ms.

[0139] In step 201, the required total braking force F _SUM ^* is initially determined, which is the braking force F required for the vehicle as a whole, i.e. the sum of the braking forces F, which should be provided in four wheels 10, based on the operation of pressing the brake pedal 40. (Further in this document, step 201 is abbreviated as “S201”, and other steps are abbreviated in a similar manner). In particular, the brake pedal 40 includes a stroke sensor 168 for determining the stroke St as the operating amount of the depression of the brake pedal 40, as shown in FIG. 18 and 19. HY-ECU 164 obtains the required full braking force F _SUM ^* by multiplying the working stroke St, determined by means of the working stroke sensor 168, by the braking force coefficient α _F. Stroke St is one example of a working value indicating the degree of operation of pressing the brake pedal 40, namely indicating the degree of operation of pressing the brake pedal, and can be considered as a parameter indicating the required full braking force F _SUM ^* .

[0140] In the present vehicle braking system, a regenerative braking force F _{RG is} preferably generated, and the hydraulic braking force F _HY and the electric braking force F _EM cover the lack of the required full braking force F _SUM *, which cannot be covered by the regenerative braking force F _Rg . The shortage is called "insufficient braking force F _IS ".

[0141] To achieve the above, the signal associated with the desired full braking force F _SUM ^* is transmitted from the HY-ECU 164 to the HB-ECU 160. In S202, the HB-ECU 160 determines the required regenerative braking force F _RG ^* force) as the maximum regenerative braking force F _RG , which can be formed in a range not exceeding the required total braking force F _SUM ^* . The signal associated with the required regenerative braking force F _RG ^* is returned from the HB-ECU 160 to the HY-ECU 164.

[0142] In S203, HY-ECU 164 determines the insufficient braking force F _IS by subtracting the required regenerative braking force F _RG ^* from the required total braking force F _SUM ^* . The insufficient braking force F _{IS is} covered by the hydraulic braking force F _HY and the electric braking force F _EM in such a way that the hydraulic braking force F _HY and the electric braking force F _EM satisfy the specified distribution coefficient (β _HY : β _EM ). In particular, in S204, HY-ECU 164, respectively, multiplies the insufficient braking force F _IS by the hydraulic braking force distribution coefficient β _HY and the electric braking force distribution coefficient β _EM (β _HY + β _EM = 1) in order to determine the required the hydraulic braking force F _HY ^* (target hydraulic braking force) as the hydraulic braking force F _HY to be generated, and the required electric braking force F _EM ^* (targeted electrical braking force) as the electric braking force F _EM that is up to false to form. The signal associated with the target electrical braking force F _EM ^* is transmitted from the HY-ECU 164 to the EM-ECU 166.

[0143] In S205, a regenerative braking device 30, a hydraulic braking device 32 and an electric braking device 34 are controlled, respectively, based on the required regenerative braking force F _RG ^* , the required hydraulic braking force F _HY ^* and the required electric braking force F _EM ^* defined as described above. In particular, the HB-ECU 160 controls the inverter 26M in such a manner that the regenerative braking force F _RG becomes equal to the required regenerative braking force F _RG ^* . The HY-ECU 164 controls the electrical currents to be supplied to the motor 62 and the pressure maintenance valves 64, so that the hydraulic braking force F _HY becomes equal to the required hydraulic braking force F _HY ^* . The EM-ECU 166 controls the electrical current that must be supplied to the electric motors 114, so that the electric braking force F _EM becomes equal to the required electric braking force F _EM ^* .

[0144] According to the control described above, the regenerative braking force, the hydraulic braking force, and the electric braking force are controlled so that they interact with each other. In particular, the regenerative braking force, the hydraulic braking force and the electric braking force are jointly controlled in such a way that the hydraulic braking force and the electric braking force cover the lack of the required total braking force, which cannot be covered by the regenerative braking force, i.e. insufficient braking force. Joint control provides the ability to simply obtain the required required total braking force, even if the regenerative braking force varies, for example, by varying the vehicle speed or varying charge state (SOC) of the battery 28. Additionally, the hydraulic braking force and the electric braking force are jointly controlled in this way that the hydraulic braking force and the electric braking force are formed at a given distribution coefficient (β _HY : β _EM ). Joint control provides the ability to control two braking forces according to a simple control rule, due to which, in general, the corresponding braking force required for a vehicle can be easily controlled.

Modifications

[0145] In a vehicle braking system of the first embodiment, an electric braking force is provided to one of the front wheel 10F and a rear wheel 10R to which regenerative braking force is provided, and a hydraulic braking force is provided to another from the front wheel 10F and the rear wheel 10R which is not provided regenerative braking force. In the vehicle braking system of the third embodiment, the electric braking force is provided to one of the front wheel 10F and the rear wheel 10R, which is not provided with regenerative braking force, and the hydraulic braking force is provided to the other from the front wheel 10F and the rear wheel 10R, which is provided with regenerative braking force . In the case in which the vehicle braking system includes a regenerative braking device, a determination as to which of the hydraulic braking force and the electric braking force is applied to the wheel, to which the regenerative braking force is provided, can be carried out in accordance with the general design principle of the braking system vehicle. The brake system of the first embodiment is mounted on a front-wheel drive vehicle. The braking system can be installed on rear-wheel drive vehicles or on four-wheel drive vehicles. In the vehicle braking system of the first embodiment, when the vehicle speed falls below a threshold speed as a result of a vehicle deceleration, a switching operation is performed in which the regenerative braking force gradually decreases and the hydraulic braking force gradually increases. The switching operation can be modified in such a way that the electrical braking force gradually increases with a gradual decrease in the regenerative braking force.

[0146] In the vehicle brake system of the second embodiment, the hydraulic braking force is provided to the driving wheel, and the electric braking force is provided to the non-driving wheel. Electrical braking power may be provided to the drive wheel, and hydraulic braking power may be provided to the non-driving wheel. The brake system of each of the first to third embodiments is mounted on a vehicle with front-wheel drive. The braking system of each of the first to third embodiments may be mounted on rear-wheel drive vehicles or four-wheel drive vehicles. In the vehicle braking system of each of the first embodiment and the third embodiment, a regenerative braking device is provided for the front wheels 10F. It is possible to design a vehicle braking system in which a regenerative braking device is provided for the rear wheels 10R.

[0147] From the point of view of identifying the variation of one of the hydraulic braking force and the electric braking force, the braking force control principle of the braking system of the vehicle of the second embodiment can be used in the braking system of the vehicle of the first embodiment. In other words, a braking system equipped with a regenerative braking device can be configured to: identify the variation of one of the hydraulic braking force and the electric braking force based on the determination of the actual braking force; and vary the other of the hydraulic braking force and the electric braking force. In this case, S104-S115 in the braking force control program (FIG. 17) executed in the vehicle braking system of the second embodiment is replaced with S7-S13 in the braking force control program (Fig. 10) running in the vehicle braking system the first embodiment.

[0148] Similarly, the braking force control principle of a vehicle braking system of the first embodiment can be used in a vehicle braking system of the second embodiment. In other words, a braking system that is not equipped with a regenerative braking device can be configured to: evaluate that the vehicle is in a situation in which one of the hydraulic braking force and the electric braking force is reduced, based on at least one of the environment in which the vehicle is located, and the status of the constituent component of the brake system of the vehicle; and vary the other of the hydraulic braking force and the electric braking force based on the evaluation. In this case, the braking force control program (FIG. 10) executed in the vehicle braking system of the first embodiment is executed such that the required regenerative braking force F _RG ^{* is} treated as being equal to 0.

[0149] In the vehicle brake system of the first embodiment, a switching operation is performed in which the hydraulic braking force is increased, while the regenerative braking force is reduced. The switching operation can be modified in such a way that the electric braking force is increased, while the regenerative braking force is reduced.

[0150] In the vehicle braking system of each of the first embodiment and the second embodiment, a braking device configured to electronically control the hydraulic braking force is used as the hydraulic braking device. A hydraulic braking device capable of non-electronically controlling the hydraulic braking force can be used, for example, a hydraulic braking device equipped with an amplifier due to negative pressure. In this case, although the variation of the electric braking force cannot be overcome by changing the hydraulic braking force, the variation of the hydraulic braking force can be overcome by changing the electric braking force.

[0151] Only one ECU 130 can control the respective braking forces F, similarly to the braking system of the first embodiment. Alternatively, the plurality of ECUs, respectively, may control the plurality of braking forces F when communicating with each other, similarly to the braking system of the third embodiment.

[0152] In the brake system of each of the illustrated embodiments, electric current is supplied from the auxiliary battery 124 to each of the wheel brakes 100, which constitute the electric braking device 34. Electric current may be supplied from the battery 28 of the vehicle drive system.

[0153] As one example of an operation value indicating the degree of operation of pressing the brake pedal 40 (which is a working brake element), namely indicating the degree of operation of pressing the brake pedal, the operating brake force δ is used in the vehicle braking system of the first embodiment, and the working stroke St is used in the vehicle braking system of the third embodiment. The operating value may be considered as a parameter indicating the required full braking force. Any of the operating braking force δ and stroke St can be used as the operating value in the brake systems of the vehicle of the first and third embodiments. Alternatively, both of the working braking force δ and the working stroke St can be used to determine the required total braking force.

Claims (33)

1. A vehicle braking system comprising: - working brake element (40), which must be controlled by the driver of the vehicle; - a hydraulic braking device (32) provided for one of the front wheel (10F) and the rear wheel (10R) and configured to form a hydraulic braking force in accordance with the operation of the operating braking element, the hydraulic braking force depending on the pressure of the working fluid; and - an electric braking device (34) provided for the other of the front wheel and the rear wheel and configured to form an electric braking force in accordance with the operation of the operating braking element, the electric braking force depending on the movement of the electric motor (114); characterized in that it is estimated that the vehicle is in a situation in which one of the hydraulic braking force and the electric braking force is reduced, based on at least one of the medium in which the vehicle is placed, and the state of the constituent component of the braking system of the vehicle, and the other of the hydraulic braking force and the electric braking force is increased so that it covers the reduction of said one of the hydraulic braking force and electric oh the braking force, or in which the other of the hydraulic braking force and the electric braking force is reduced in accordance with the reduction of said one of the hydraulic braking force and the electric braking force, based on said estimation. 2. A vehicle braking system according to claim 1, adapted to assessing that the vehicle is in a situation in which said one of the hydraulic braking force and the electric braking force is reduced, based on at least one of the outside temperature as the environment in which the vehicle is located, the atmospheric pressure as the environment in which the vehicle is located, the temperature of the electric motor (114) as a state of a component of the braking system of the vehicle VA and battery voltage (28), made with the ability to supply electrical power to the electric motor, as the state component of the brake system of the vehicle. 3. A vehicle braking system according to claim 1 or 2, in which the situation in which the other of the hydraulic braking force and the electric braking force decreases is a situation in which said one of the hydraulic braking force and the electric braking force decreases due to the delay of the increase mentioned one of the hydraulic braking force and electric braking force. 4. The brake system of the vehicle according to any one of paragraphs. 1-3, further comprising a regenerative braking device (30) provided for one of the front wheel (10F) and the rear wheel (10R), for which one of the hydraulic braking device (32) is provided, configured to form a hydraulic braking force, and an electric braking device (34) configured to form an electric braking force, the regenerative braking device being configured to generate a regenerative braking force using yrabotki electric power by the rotation of one of the front wheel and rear wheel, which provides for regenerative braking device, - while when the switching operation is performed to increase said one of the hydraulic braking force and the electric braking force while reducing the regenerative braking force, the other of the hydraulic braking force and the electric braking force increases or decreases so that it corresponds to the reduction of said one of the hydraulic braking force and an electric braking force in a situation in which said one of the hydraulic braking force and the electric braking force is reduced I. 5. The brake system of the vehicle according to any one of paragraphs. 1-4, such that the hydraulic braking force and the electric braking force can be generated at a given distribution coefficient (βHY: βEM). 6. A vehicle braking system according to claim 5, further comprising a regenerative braking device (30) provided for one of the front wheel (10F) and the rear wheel (10R), for which one of the hydraulic braking device (32) and the electric brake device (34), the regenerative braking device (30) being configured to generate regenerative braking force using the generation of electric power by rotating one of the front wheel (10F) and the rear wheel wheels (10R), - wherein the vehicle braking system is designed such that the hydraulic braking force, the electric braking force and the regenerative braking force can be controlled in such a way that they interact with each other. 7. A vehicle braking system according to claim 6, configured such that the hydraulic braking force and the electric braking force can be controlled so that the hydraulic braking force and the electric braking force cover the insufficient braking force that cannot be covered by the regenerative braking force, and insufficient braking force is a shortage in the required full braking force, which is the braking force required for the vehicle as a whole. 8. The brake system of the vehicle according to any one of paragraphs. 1-7, in which the hydraulic brake device (32) includes: - a rotation body (80) capable of rotating with one of the front wheel (10F) and the rear wheel (10R); - friction element (88), made with the ability to nestle on the body of rotation; - wheel brake cylinder (84), made with the ability to work through the working fluid filed in it, to press the friction element to the body of rotation; - a pump (60), made with the ability to pressurize the working fluid and supply the working fluid under pressure to the wheel brake cylinder; and - a pressure maintenance valve (64) configured to control the pressure of the working fluid in a controlled manner, which is to be supplied to the wheel brake cylinder. 9. The vehicle braking system in accordance with claim 8, - in which the hydraulic braking device (32) further includes: - a master cylinder (42) comprising (a) a piston (42a) connected to a working braking element (40), and (b) an injection chamber (42b) in which pressure is injected into the working fluid introduced into it displacement of the piston, wherein the master cylinder is adapted to pressurize the working fluid by means of a working force applied by the driver to the working braking element; - the main line (50) for the fluid, through which the working fluid to which the pressure in the pressure chamber of the main cylinder is pressurized, is fed to the wheel brake cylinder; and - valve (56) opening / closing, made with the ability to open and close the main line for the liquid, - wherein the wheel brake cylinder operation by means of the working fluid supplied from the master cylinder, and the wheel brake cylinder operation by means of the working fluid fed from the pump are selectively set based on the operating mode of the open / close valve. 10. A vehicle braking system in accordance with claim 9, - in which the hydraulic braking device (32) includes: a tank (48), which contains the working fluid and from which the pump (60) pumps the working fluid; and a channel (69) for the fluid in the tank that connects the tank and the pump, and - wherein the pressure maintenance valve (64) allows a portion of the working fluid, which is to be supplied from the pump to the wheel brake cylinder (84), to pass through the pressure maintenance valve in order to regulate the pressure of the working fluid, and a portion of the working fluid that passes through pressure maintenance valve, flows into the tank or the channel for the liquid in the tank. 11. A vehicle braking system according to claim 10, wherein the hydraulic braking device (32) includes a shut-off valve (66) adapted to cut off the flow of working fluid into the tank (48) or channel (69) for the fluid in the tank, when the wheel brake cylinder (84) is operated by means of a working fluid supplied from the master cylinder (42), in the state in which the valve (56) of opening / closing is open. 12. A vehicle braking system according to claim 10 or 11, in which the reservoir (48) is located near the master cylinder (42) and the working pressure from the reservoir (42b) of the master cylinder is pressurized to the working fluid. 13. The brake system of the vehicle according to any one of paragraphs. 9-12, in which the hydraulic brake device (32) includes a simulator (54) of resistance to the pedal travel, provided in the main line (50) for the fluid and configured to provide the possibility of operation of the operating brake element (40), while ensuring the working to the brake element, the counteracting force in accordance with the operation of the operating brake element, when the wheel brake cylinder (84) is operated by means of the working fluid supplied from the pump (60), in the state in which the valve (56) of opening / closing is acryt 14. The brake system of the vehicle according to any one of paragraphs. 8-13, in which the pump (60) and the valve (64) to maintain the pressure of the hydraulic braking device (32) are included in the module of the actuator (44). 15. The brake system of the vehicle according to any one of paragraphs. 8-14, in which the pressure maintenance valve (64) is a linear solenoid valve configured to reduce the pressure of the working fluid to be supplied to the wheel brake cylinder (84) to a pressure in accordance with the electric current supplied to the linear solenoid valve .

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