JP4779768B2 - Vehicle braking device - Google Patents

Description

  The present invention relates to a vehicle braking device that applies braking force to a plurality of wheels provided in a vehicle.

2. Description of the Related Art Conventionally, there has been known a combined brake cooperative control device that realizes a target braking torque determined according to a driving state and a traveling state of a vehicle by cooperation of regenerative braking and friction braking (for example, see Patent Document 1). A hydraulic braking force applying mechanism is employed as friction braking. This device determines the regenerative braking torque and friction braking torque command values so that the regenerative braking torque does not exceed this limit value based on the regenerative braking torque limit value obtained by applying a predetermined limit to the allowable maximum regenerative braking torque. . The allowable maximum regenerative braking torque is calculated by the motor torque controller from the state of charge of the battery, temperature, and the like.
JP 2004-328884 A

  In the above-described brake control, the allowable maximum regenerative braking torque increases or decreases depending on the state of charge and temperature of the battery. It is considered that the regenerative braking torque also increases / decreases as the allowable maximum regenerative braking torque increases / decreases. Since it is cooperative control, the friction braking torque is also increased or decreased according to the increase or decrease of the regenerative braking torque. In order to increase or decrease the friction braking torque, it is necessary to execute switching between hydraulic pressure increase control and pressure reduction control. If such switching is frequently performed as the regenerative braking torque increases or decreases, the durability of the components of the hydraulic braking force applying mechanism such as the hydraulic control valve may be adversely affected.

  In view of the above, an object of the present invention is to provide a brake control device that can realize a long life of a hydraulic braking force application mechanism used for cooperative control between regenerative braking and hydraulic braking.

  In order to solve the above problems, a vehicle braking apparatus according to an aspect of the present invention includes a regenerative braking unit that generates a regenerative braking force by regenerative control of an electric motor, and a required braking force that is applied to a wheel by complementing the regenerative braking force. Therefore, a hydraulic brake unit that generates hydraulic braking force by supplying hydraulic fluid from a hydraulic pressure source, a control unit that controls the regenerative brake unit so that the regenerative energy absorption rate during braking does not exceed a predetermined upper limit value, Is provided.

  According to this aspect, the vehicle braking device includes a regenerative braking unit that generates a regenerative braking force by regenerative control of the electric motor, and a hydraulic brake unit that generates a hydraulic braking force by supplying hydraulic fluid from a hydraulic pressure source. ing. In this device, cooperative control between the regenerative brake and the hydraulic brake, that is, cooperative control is performed in which the regenerative braking force is preferentially used and the amount that is deficient in the required braking force is supplemented by the hydraulic braking force. In such cooperative control, the control unit limits the increase in the regenerative energy absorption rate so that the regenerative energy absorption rate does not exceed the upper limit value while generating the hydraulic braking force, while reducing the regenerative energy absorption rate. Control the regenerative brake unit to allow. Here, the regenerative energy absorption rate refers to electric energy per unit time obtained by regenerative control of the electric motor.

  By controlling the regenerative energy absorption rate during braking so as not to exceed the set upper limit value, as long as the regenerative energy absorption rate reaches the upper limit value, the regenerative braking force increases smoothly as the vehicle speed decreases . Since the hydraulic braking force is controlled so as to complement the regenerative braking force, if the increase in the regenerative braking force is smooth, the variation in the hydraulic braking force is also smooth. As a result, the load on the hydraulic brake unit is reduced, and a longer life can be realized. As a result, it is possible to relax the design requirements regarding the life of the hydraulic brake unit, and the hydraulic brake unit and thus the vehicle braking device can be designed at a lower cost and more simply.

  Furthermore, while generating the hydraulic braking force, the control unit limits the increase in the regenerative energy absorption rate so as not to exceed the upper limit value, but allows the decrease. The regenerative energy absorption rate may vary according to changes in the state of, for example, an electric motor or a storage battery. However, according to this aspect, a decrease in the regenerative energy absorption rate during the generation of the hydraulic braking force is allowed while an increase is limited. Therefore, the regenerative energy absorption rate during braking has a decreasing tendency and does not increase or decrease in vibration. As a result, the increase and decrease of the regenerative braking force is also suppressed, and the load on the hydraulic brake unit can be further reduced.

  In addition, the battery may further include a storage battery that stores electric energy obtained by regenerative control of the electric motor, and the control unit may set the energy receiving capacity of the storage battery at the start of generation of the hydraulic braking force as an upper limit value.

  According to this aspect, the storage battery accumulates electric energy obtained by the regenerative brake. The accumulated electric energy is appropriately used for the subsequent driving of the wheels and the like, thereby improving the fuel efficiency of the vehicle. At this time, the upper limit value of the regenerative energy absorption rate may be the energy receiving capacity of the storage battery at the start of generation of the hydraulic braking force. Here, the energy acceptance capacity of the storage battery refers to electric energy per unit time that can be stored in the storage battery.

  By making the energy acceptance capacity of the storage battery the upper limit value of the regenerative energy absorption rate, the recovery efficiency of energy obtained from the regenerative brake can be increased. In addition, by setting the value at the start of the generation of hydraulic braking force as the upper limit, even if the energy receiving capacity increases after the operation of the hydraulic brake unit starts, the regenerative energy absorption rate follows the increase and reaches the upper limit. There is no increase beyond that. Thereby, improvement of energy recovery efficiency and coexistence with the load reduction of a hydraulic brake unit can be aimed at.

  Furthermore, the control unit may update the regenerative energy absorption rate after the decrease as the upper limit value when the regenerative energy absorption rate decreases after reaching the initially set upper limit value. Each time the regenerative energy absorption rate decreases, the upper limit value is updated to the value of the regenerative energy absorption rate after the decrease, thereby preventing an increase again after the decrease of the regenerative energy absorption rate. Therefore, it becomes possible to make the fluctuation | variation of a hydraulic braking force smooth, and can reduce the load of a hydraulic brake unit.

  According to the present invention, it is possible to extend the life of a hydraulic braking force application mechanism.

  First, an outline of the vehicle braking device according to the present embodiment will be described. According to the present apparatus, the switching frequency of increase / decrease of the hydraulic braking force that supplements the regenerative braking force is reduced, and the design requirements regarding the durability of the components of the hydraulic brake unit, particularly the hydraulic control valve, can be eased. it can. Therefore, the hydraulic brake unit and thus the vehicle braking device can be simply designed at a lower cost.

  Therefore, in this device, an upper limit value is set for the regenerative energy absorption rate, and the regenerative brake unit is preferably controlled so as to monotonically increase the regenerative braking force along an equal energy curve corresponding to this upper limit value. . By monotonically increasing the regenerative braking force, it is possible to reduce the switching frequency between the pressure increase control and the pressure decrease control of the hydraulic braking force that complements the regenerative braking force.

  In this device, in order to improve the fuel efficiency of the vehicle, braking force due to regeneration of the electric motor (referred to as “regenerative braking force” in this specification as appropriate) and friction braking force due to hydraulic pressure (herein referred to as “hydraulic braking force” as appropriate). To generate the required braking force. The regenerative braking force is a braking force applied to the wheel by operating an electric motor for driving the wheel as a generator that receives the rotational torque of the traveling wheel. The kinetic energy of the vehicle is converted into electric energy, and the electric energy is accumulated in the storage battery from the electric motor through a power conversion device including an inverter and the like. The accumulated electric energy is used for driving the wheels and the like, and contributes to improving the fuel consumption of the vehicle. On the other hand, the hydraulic braking force is a braking force applied to the wheel by pressing the friction member against the rotating member that rotates together with the wheel by supplying hydraulic fluid from the hydraulic pressure source. In order to further improve the fuel consumption, it is preferable to preferentially use the regenerative braking force, and to supplementarily generate the amount that is insufficient for the required braking force by the regenerative braking force by the hydraulic braking force.

  FIG. 1 is a diagram schematically illustrating an example of a temporal change in vehicle speed and braking force during braking of the vehicle braking apparatus according to the present embodiment. The vehicle speed is shown in the upper part of FIG. 1, the required braking force and the regenerative braking force are shown in the middle part, and the hydraulic braking force is shown in the lower part. As described above, the difference between the required braking force and the regenerative braking force is the hydraulic braking force, but the hydraulic braking force is shown at the bottom of FIG. 1 for easy understanding.

  The regenerative braking force monotonously increases as the vehicle speed decreases under a constant regenerative energy absorption rate. A curve indicating the relationship between the regenerative braking force and the vehicle speed when the regenerative energy absorption rate is constant is called an equal energy curve. Here, the regenerative energy absorption rate refers to electric energy per unit time obtained by regenerative control of the electric motor. That the regenerative energy absorption rate is constant means that the rate of decrease in the kinetic energy of the vehicle due to regenerative braking is constant. If the rate of decrease in kinetic energy is constant, the vehicle deceleration decreases as the vehicle speed increases. Conversely, the vehicle deceleration increases as the vehicle speed decreases. That is, it can be said that the regenerative braking force decreases as the vehicle speed increases, and the regenerative braking force increases as the vehicle speed decreases.

  If the regenerative braking force increases as the vehicle decelerates, it may be relatively difficult to control the regenerative braking force. Therefore, the control unit performs control to gradually reduce the regenerative braking force in order to maintain controllability after the vehicle speed becomes sufficiently small.

  From the above, the regenerative braking force monotonously increases along the equal energy curve and reaches a predetermined maximum value as the vehicle speed decreases as shown in region a in FIG. Then, the vehicle speed is further controlled to decrease gradually as shown in region b in FIG. In this way, the regenerative braking force is ideally controlled so as to draw one smooth mountain during one braking.

  On the other hand, the required braking force increases to a value corresponding to the driver's brake operation amount in response to the braking request (region c in FIG. 1), and is maintained until the driver's brake operation is released (FIG. 1). Area d). For this reason, the hydraulic braking force repeats the switching from the pressure increase control to the pressure reduction control twice per braking as follows.

  First, when the required braking force increases, the regenerative braking force increases with a decrease in the vehicle speed, so that the hydraulic braking force also increases (region e in FIG. 1). Next, even after the required braking force reaches a value corresponding to the brake operation, the regenerative braking force continues to increase toward the maximum value, so that the hydraulic braking force decreases (region f in FIG. 1). This is the first switching. Next, when the regenerative braking force reaches the maximum value and starts to decrease, the hydraulic braking force complementarily increases (region g in FIG. 1). Then, the hydraulic braking force also decreases as the required braking force decreases due to the release of the brake operation. This is the second switching.

  By the way, the regenerative braking force may fluctuate due to a change in the state of the electric motor or the storage battery. For example, the regenerative energy absorption rate of the motor or the energy receiving capacity of the storage battery varies as the temperature of the motor or the storage battery or the SOC (State of Charge) of the storage battery varies. Here, the energy receiving capacity of the storage battery refers to the energy per unit time that can be stored in the storage battery. The regenerative braking force varies according to the variation of the regenerative energy absorption rate and the energy receiving capacity. If the regenerative energy absorption rate or the like increases, the regenerative braking force also increases. Conversely, if the regenerative energy absorption rate or the like decreases, the regenerative braking force also decreases.

  FIG. 2 is a diagram schematically illustrating an example of a temporal change in vehicle speed and braking force during braking of a conventional vehicle braking device. FIG. 2 shows a case where the regenerative energy absorption rate increases at a stage where the regenerative braking force increases along the equal energy curve. As in FIG. 1, the vehicle speed is shown in the upper part of FIG. 2, the required braking force and the regenerative braking force are shown in the middle part, and the hydraulic braking force is shown in the lower part.

  When the regenerative energy absorption rate increases, the regenerative braking force further increases aiming at the increased equal energy curve. If the increase in the regenerative braking force is large, there may be a case where control for temporarily reducing the regenerative braking force is required for reasons such as ensuring controllability. Then, the regenerative braking force is controlled not to draw one mountain during one braking as described above, but to draw a plurality of peaks by repeatedly increasing and decreasing as shown in FIG. End up.

  If the regenerative braking force repeatedly increases or decreases, the hydraulic braking force must be increased or decreased frequently to compensate for this increase or decrease. In order to increase or decrease the hydraulic braking force, for example, a pressure increasing control valve or a pressure reducing control valve, which is a component of the hydraulic brake unit, is opened and closed. As the frequency of increase / decrease in the regenerative braking force increases, the operation frequency of these control valves and the like also increases, which may adversely affect durability.

  Therefore, in this apparatus, the control unit sets an upper limit value for the regenerative energy absorption rate, and controls the regenerative brake unit so that the regenerative energy absorption rate during braking does not exceed the set upper limit value. The control unit may control the regenerative brake unit so that the regenerative energy absorption rate does not exceed the upper limit value at least during the increase of the regenerative braking force after the start of generation of the hydraulic braking force. As long as the regenerative energy absorption rate reaches the upper limit, the regenerative braking force smoothly increases along the equal energy curve as the vehicle speed decreases as shown in FIG. Since the hydraulic braking force is controlled so as to complement the regenerative braking force in the brake regenerative cooperative control, if the increase of the regenerative braking force is smooth, the fluctuation of the hydraulic braking force becomes smooth.

  The control unit sets the upper limit value of the regenerative energy absorption rate with the energy receiving capacity of the storage battery as the upper limit. This is because, from the viewpoint of energy recovery, it is less necessary for the regenerative energy absorption rate of the motor to exceed the energy receiving capacity of the storage battery. Actually, it is desirable to set the energy receiving capacity when the hydraulic braking force starts to be generated after the braking request as the upper limit value of the regenerative energy absorption rate. If it does so, while the fluctuation | variation of a hydraulic braking force can be smoothed quickly from the time of the operation | movement start of a hydraulic brake unit, energy recovery efficiency can be made high.

  Subsequently, the best mode for carrying out the present invention will be described in more detail with reference to the drawings.

  FIG. 3 is a schematic configuration diagram illustrating a vehicle to which a vehicle braking device according to an embodiment of the present invention is applied. A vehicle 1 shown in the figure is configured as a so-called hybrid vehicle, and includes an engine 2, a three-shaft power split mechanism 3 connected to a crankshaft that is an output shaft of the engine 2, and a power split mechanism 3. A motor generator 4 capable of generating electricity, an electric motor 6 connected to the power split mechanism 3 via a transmission 5, and an electronic control unit for hybrid (hereinafter referred to as “hybrid ECU”) that controls the entire drive system of the vehicle 1. The electronic control unit is all referred to as “ECU”). A right front wheel 9FR and a left front wheel 9FL, which are drive wheels of the vehicle 1, are connected to the transmission 5 via a drive shaft 8.

  The engine 2 is an internal combustion engine that is operated using a hydrocarbon-based fuel such as gasoline or light oil, and is controlled by the engine ECU 13. The engine ECU 13 can communicate with the hybrid ECU 7, and performs fuel injection control, ignition control, intake control, etc. of the engine 2 based on control signals from the hybrid ECU 7 and signals from various sensors that detect the operating state of the engine 2. Execute. Further, the engine ECU 13 gives information regarding the operating state of the engine 2 to the hybrid ECU 7 as necessary.

  The power split mechanism 3 transmits the output of the electric motor 6 to the left and right front wheels 9FR, 9FL via the transmission 5, distributes the output of the engine 2 to the motor generator 4 and the transmission 5, and the electric motor. 6 and the speed of the engine 2 is reduced or increased. The motor generator 4 and the electric motor 6 are each connected to a battery 12 via a power converter 11 including an inverter, and a motor ECU 14 is connected to the power converter 11. As the battery 12, for example, a storage battery such as a nickel hydride storage battery can be used. The motor ECU 14 can also communicate with the hybrid ECU 7 and controls the motor generator 4 and the electric motor 6 via the power converter 11 based on a control signal from the hybrid ECU 7 or the like. The hybrid ECU 7, engine ECU 13, and motor ECU 14 described above are all configured as a microprocessor including a CPU. In addition to the CPU, a ROM that stores various programs, a RAM that temporarily stores data, and an input / output port And a communication port.

  The left and right front wheels 9FR and 9FL can be driven by the output of the electric motor 6 by supplying electric power from the battery 12 to the electric motor 6 via the power converter 11 under the control of the hybrid ECU 7 and the motor ECU 14. . Further, the vehicle 1 is driven by the engine 2 in a driving region where the engine efficiency is good. At this time, by transmitting a part of the output of the engine 2 to the motor generator 4 via the power split mechanism 3, the electric motor 6 is driven using the electric power generated by the motor generator 4 or the power conversion device 11 is operated. It is possible to charge the battery 12.

  When the vehicle 1 is braked, the electric motor 6 is rotated by the power transmitted from the front wheels 9FR and 9FL under the control of the hybrid ECU 7 and the motor ECU 14, and the electric motor 6 is operated as a generator. That is, the electric motor 6, the power converter 11, the hybrid ECU 7, the motor ECU 14, and the like function as a regenerative brake unit 10 that applies braking force to the left and right front wheels 9FR, 9FL by regenerating the kinetic energy of the vehicle 1 into electric energy. To do.

  In addition to the regenerative brake unit 10, the vehicle 1 includes a hydraulic brake unit 20 that generates a braking force by supplying hydraulic fluid from a power hydraulic pressure source 30 or the like as shown in FIG. 4. The vehicle braking device of the present embodiment is capable of braking the vehicle 1 by executing brake regeneration cooperative control in which the regenerative brake unit 10 and the hydraulic brake unit 20 are coordinated. The vehicle 1 in the present embodiment can generate a desired braking force by using the regenerative braking force and the hydraulic braking force together by executing the brake regeneration cooperative control.

  FIG. 4 is a system diagram showing the hydraulic brake unit 20 according to the present embodiment. As shown in FIG. 4, the hydraulic brake unit 20 includes disc brake units 21FR, 21FL, 21RR and 21RL provided for each wheel, a master cylinder unit 27, a power hydraulic pressure source 30, a hydraulic brake unit 20 Pressure actuator 40.

  Disc brake units 21FR, 21FL, 21RR, and 21RL apply braking force to the right front wheel, the left front wheel, the right rear wheel, and the left rear wheel of the vehicle, respectively. The master cylinder unit 27 as a manual hydraulic pressure source sends brake fluid as hydraulic fluid pressurized according to the amount of operation by the driver of the brake pedal 24 as a brake operation member to the disc brake units 21FR to 21RL. To do. The power hydraulic pressure source 30 can send the brake fluid pressurized by the power supply to the disc brake units 21FR to 21RL independently from the operation of the brake pedal 24 by the driver. The hydraulic actuator 40 appropriately adjusts the hydraulic pressure of the brake fluid supplied from the power hydraulic pressure source 30 or the master cylinder unit 27 and sends it to the disc brake units 21FR to 21RL. Thereby, the braking force with respect to each wheel by hydraulic braking is adjusted.

  Each of the disc brake units 21FR to 21RL, the master cylinder unit 27, the power hydraulic pressure source 30, and the hydraulic actuator 40 will be described in more detail below. Each of the disc brake units 21FR to 21RL includes a brake disc 22 and wheel cylinders 23FR to 23RL incorporated in the brake caliper, respectively. The wheel cylinders 23FR to 23RL are connected to the hydraulic actuator 40 via different fluid passages. Hereinafter, the wheel cylinders 23FR to 23RL are collectively referred to as “wheel cylinders 23” as appropriate.

  In the disc brake units 21FR to 21RL, when brake fluid is supplied to the wheel cylinder 23 from the hydraulic actuator 40, a brake pad as a friction member is pressed against the brake disc 22 that rotates together with the wheel. Thereby, a braking force is applied to each wheel. In the present embodiment, the disc brake units 21FR to 21RL are used, but other braking force applying mechanisms including a wheel cylinder 23 such as a drum brake may be used.

  In this embodiment, the master cylinder unit 27 is a master cylinder with a hydraulic booster, and includes a hydraulic booster 31, a master cylinder 32, a regulator 33, and a reservoir. The hydraulic booster 31 is connected to the brake pedal 24, amplifies the pedal effort applied to the brake pedal 24, and transmits it to the master cylinder 32. When the brake fluid is supplied from the power hydraulic pressure source 30 to the hydraulic pressure booster 31 via the regulator 33, the pedal effort is amplified. The master cylinder 32 generates a master cylinder pressure having a predetermined boost ratio with respect to the pedal effort.

  A reservoir 34 for storing brake fluid is disposed above the master cylinder 32 and the regulator 33. The master cylinder 32 communicates with the reservoir 34 when the depression of the brake pedal 24 is released. On the other hand, the regulator 33 is in communication with both the reservoir 34 and the accumulator 35 of the power hydraulic pressure source 30, and the reservoir 34 is used as a low pressure source, the accumulator 35 is used as a high pressure source, and the hydraulic pressure is approximately equal to the master cylinder pressure. Is generated. Hereinafter, the hydraulic pressure in the regulator 33 is appropriately referred to as “regulator pressure”.

  The power hydraulic pressure source 30 includes an accumulator 35 and a pump 36. The accumulator 35 converts the pressure energy of the brake fluid boosted by the pump 36 into the pressure energy of an enclosed gas such as nitrogen, for example, about 14 to 22 MPa and stores it. The pump 36 has a motor 36 a as a drive source, and its suction port is connected to the reservoir 34, while its discharge port is connected to the accumulator 35. The accumulator 35 is also connected to a relief valve 35 a provided in the master cylinder unit 27. When the pressure of the brake fluid in the accumulator 35 increases abnormally to about 25 MPa, for example, the relief valve 35 a is opened, and the high-pressure brake fluid is returned to the reservoir 34.

  As described above, the hydraulic brake unit 20 includes the master cylinder 32, the regulator 33, and the accumulator 35 as a supply source of brake fluid to the wheel cylinder 23. A master pipe 37 is connected to the master cylinder 32, a regulator pipe 38 is connected to the regulator 33, and an accumulator pipe 39 is connected to the accumulator 35. These master pipe 37, regulator pipe 38 and accumulator pipe 39 are each connected to a hydraulic actuator 40.

  The hydraulic actuator 40 includes an actuator block in which a plurality of flow paths are formed, and a plurality of electromagnetic control valves. The flow paths formed in the actuator block include individual flow paths 41, 42, 43 and 44 and a main flow path 45. The individual flow paths 41 to 44 are respectively branched from the main flow path 45 and connected to the wheel cylinders 23FR, 23FL, 23RR, 23RL of the corresponding disc brake units 21FR, 21FL, 21RR, 21RL. Thereby, each wheel cylinder 23 can communicate with the main flow path 45.

  In addition, ABS holding valves 51, 52, 53 and 54 are provided in the middle of the individual flow paths 41, 42, 43 and 44. Each of the ABS holding valves 51 to 54 has a solenoid and a spring that are ON / OFF controlled, and both are normally open electromagnetic control valves that are opened when the solenoid is in a non-energized state. Each of the ABS holding valves 51 to 54 in the opened state can distribute the brake fluid in both directions. That is, the brake fluid can flow from the main flow path 45 to the wheel cylinder 23, and conversely, the brake fluid can also flow from the wheel cylinder 23 to the main flow path 45. When the solenoid is energized and the ABS holding valves 51 to 54 are closed, the flow of brake fluid in the individual flow paths 41 to 44 is blocked.

  Further, the wheel cylinder 23 is connected to the reservoir channel 55 via pressure reducing channels 46, 47, 48 and 49 connected to the individual channels 41 to 44, respectively. ABS decompression valves 56, 57, 58 and 59 are provided in the middle of the decompression channels 46, 47, 48 and 49. Each of the ABS pressure reducing valves 56 to 59 has a solenoid and a spring that are ON / OFF controlled, and is a normally closed electromagnetic control valve that is closed when the solenoid is in a non-energized state. When the ABS pressure reducing valves 56 to 59 are closed, the flow of brake fluid in the pressure reducing flow paths 46 to 49 is blocked. When the solenoid is energized and the ABS pressure reducing valves 56 to 59 are opened, the brake fluid is allowed to flow through the pressure reducing flow paths 46 to 49, and the brake fluid flows from the wheel cylinder 23 to the pressure reducing flow paths 46 to 49 and It returns to the reservoir 34 via the reservoir channel 55. The reservoir channel 55 is connected to the reservoir 34 of the master cylinder unit 27 via a reservoir pipe 77.

  The main channel 45 has a separation valve 60 in the middle. By this separation valve 60, the main channel 45 is divided into a first channel 45 a connected to the individual channels 41 and 42 and a second channel 45 b connected to the individual channels 43 and 44. The first flow path 45a is connected to the front wheel side wheel cylinders 23FR and 23FL via the individual flow paths 41 and 42, and the second flow path 45b is connected to the rear wheel side wheel cylinder via the individual flow paths 43 and 44. Connected to 23RR and 23RL.

  The separation valve 60 has a solenoid and a spring that are ON / OFF controlled, and is a normally closed electromagnetic control valve that is closed when the solenoid is in a non-energized state. When the separation valve 60 is in the closed state, the flow of brake fluid in the main flow path 45 is blocked. When the solenoid is energized and the separation valve 60 is opened, the brake fluid can be circulated bidirectionally between the first flow path 45a and the second flow path 45b.

  In the hydraulic actuator 40, a master channel 61 and a regulator channel 62 communicating with the main channel 45 are formed. More specifically, the master channel 61 is connected to the first channel 45 a of the main channel 45, and the regulator channel 62 is connected to the second channel 45 b of the main channel 45. The master channel 61 is connected to a master pipe 37 that communicates with the master cylinder 32. The regulator channel 62 is connected to a regulator pipe 38 that communicates with the regulator 33.

  The master channel 61 has a master cut valve 64 in the middle. The master cut valve 64 is provided on the brake fluid supply path from the master cylinder 32 to each wheel cylinder 23. The master cut valve 64 has a solenoid and a spring that are ON / OFF-controlled, and the valve closing state is guaranteed by the electromagnetic force generated by the solenoid when supplied with a prescribed control current, so that the solenoid is in a non-energized state. It is a normally open electromagnetic control valve that is opened in some cases. The master cut valve 64 in the opened state can cause the brake fluid to flow in both directions between the master cylinder 32 and the first flow path 45 a of the main flow path 45. When a prescribed control current is applied to the solenoid and the master cut valve 64 is closed, the flow of brake fluid in the master flow path 61 is interrupted.

  A stroke simulator 69 is connected to the master channel 61 via a simulator cut valve 68 on the upstream side of the master cut valve 64. That is, the simulator cut valve 68 is provided in a flow path connecting the master cylinder 32 and the stroke simulator 69. The simulator cut valve 68 is a normally closed electromagnetic control valve that has a solenoid and a spring that are ON / OFF controlled and is closed when the solenoid is in a non-energized state. When the simulator cut valve 68 is closed, the flow of brake fluid between the master flow path 61 and the stroke simulator 69 is blocked. When the solenoid is energized and the simulator cut valve 68 is opened, the brake fluid can be circulated bidirectionally between the master cylinder 32 and the stroke simulator 69.

  The stroke simulator 69 includes a plurality of pistons and springs, and creates a reaction force corresponding to the depression force of the brake pedal 24 by the driver when the simulator cut valve 68 is opened. As the stroke simulator 69, in order to improve the feeling of brake operation by the driver, it is preferable to employ one having a multistage spring characteristic.

  The regulator flow path 62 has a regulator cut valve 65 in the middle. The regulator cut valve 65 is provided on the brake fluid supply path from the regulator 33 to each wheel cylinder 23. The regulator cut valve 65 also has a solenoid and a spring that are ON / OFF controlled, and the valve closing state is guaranteed by the electromagnetic force generated by the solenoid upon receipt of a specified control current, and the solenoid is in a non-energized state. It is a normally open electromagnetic control valve that is opened in some cases. The regulator cut valve 65 that has been opened can cause the brake fluid to flow in both directions between the regulator 33 and the second flow path 45 b of the main flow path 45. When the solenoid is energized and the regulator cut valve 65 is closed, the flow of brake fluid in the regulator flow path 62 is blocked.

  In the hydraulic actuator 40, an accumulator channel 63 is also formed in addition to the master channel 61 and the regulator channel 62. One end of the accumulator channel 63 is connected to the second channel 45 b of the main channel 45, and the other end is connected to an accumulator pipe 39 that communicates with the accumulator 35.

  The accumulator flow path 63 has a pressure-increasing linear control valve 66 in the middle. Further, the accumulator channel 63 and the second channel 45 b of the main channel 45 are connected to the reservoir channel 55 via the pressure-reducing linear control valve 67. The pressure-increasing linear control valve 66 and the pressure-decreasing linear control valve 67 each have a linear solenoid and a spring, and both are normally closed electromagnetic control valves that are closed when the solenoid is in a non-energized state. In the pressure-increasing linear control valve 66 and the pressure-decreasing linear control valve 67, the opening degree of the valve is adjusted in proportion to the current supplied to each solenoid.

  The pressure-increasing linear control valve 66 is provided as a common pressure-increasing control valve for each of the wheel cylinders 23 provided corresponding to each wheel. Similarly, the pressure reducing linear control valve 67 is provided as a pressure reducing control valve common to the wheel cylinders 23. That is, in this embodiment, the pressure-increasing linear control valve 66 and the pressure-reducing linear control valve 67 are a pair of common control valves that control the supply and discharge of the working fluid sent from the power hydraulic pressure source 30 to each wheel cylinder 23. It is provided as. If the pressure-increasing linear control valve 66 and the like are made common to each wheel cylinder 23 in this way, it is preferable from the viewpoint of cost as compared with the case where a linear control valve is provided for each wheel cylinder 23.

  In the hydraulic brake unit 20, the power hydraulic pressure source 30 and the hydraulic actuator 40 are controlled by the brake ECU 70. The brake ECU 70 is configured as a microprocessor including a CPU, and includes a ROM that stores various programs, a RAM that temporarily stores data, an input / output port, a communication port, and the like in addition to the CPU. The brake ECU 70 can communicate with a host hybrid ECU (not shown) and the like, and based on control signals from the hybrid ECU and signals from various sensors, the pump 36 of the power hydraulic pressure source 30 and the hydraulic pressure Brake regeneration cooperative control can be executed by controlling the electromagnetic control valves 51 to 54, 56 to 59, 60, and 64 to 68 constituting the actuator 40.

  Further, a regulator pressure sensor 71, an accumulator pressure sensor 72, and a control pressure sensor 73 are connected to the brake ECU 70 (see FIG. 3). The regulator pressure sensor 71 detects the pressure of the brake fluid in the regulator flow path 62 on the upstream side of the regulator cut valve 65, that is, the regulator pressure, and gives a signal indicating the detected value to the brake ECU 70. The accumulator pressure sensor 72 detects the pressure of the brake fluid in the accumulator flow path 63, that is, the accumulator pressure on the upstream side of the pressure increasing linear control valve 66, and gives a signal indicating the detected value to the brake ECU 70. The control pressure sensor 73 detects the pressure of the brake fluid in the first flow path 45a of the main flow path 45, and gives a signal indicating the detected value to the brake ECU 70. The detection values of the pressure sensors 71 to 73 are sequentially given to the brake ECU 70 every predetermined time, and are stored and held in a predetermined storage area of the brake ECU 70 by a predetermined amount.

  Further, the sensor connected to the brake ECU 70 includes a stroke sensor 25 provided on the brake pedal 24. The stroke sensor 25 detects a pedal stroke as an operation amount of the brake pedal 24 and gives a signal indicating the detected value to the brake ECU 70. The output value of the stroke sensor 25 is also sequentially given to the brake ECU 70 every predetermined time, and is stored and held in a predetermined storage area of the brake ECU 70 by a predetermined amount. A brake operation state detection unit other than the stroke sensor 25 may be provided in addition to the stroke sensor 25 or in place of the stroke sensor 25 and connected to the brake ECU 70. Examples of the brake operation state detection means include a pedal depression force sensor that detects an operation force of the brake pedal 24 and a brake switch that detects that the brake pedal 24 is depressed.

  FIG. 5 is a flowchart for explaining brake regeneration cooperative control in the vehicle braking apparatus of the present embodiment. The brake regenerative cooperative control in the present embodiment is applied to each wheel by the regenerative braking torque applied to the front wheels 9FR and 9FL as drive wheels by the regenerative brake unit 10 including the electric motor 6 and the hybrid ECU 7 and the like, and the hydraulic brake unit 20. This is to make the total braking torque, which is the sum of the friction braking torques to be made, coincide with the braking torque required by the driver.

  The vehicle braking device starts braking upon receiving a braking request. The braking request is generated when a braking force should be applied to the vehicle. The braking request is, for example, when the driver operates the brake pedal 24, or when the distance from the other vehicle is narrower than a predetermined distance when the distance from the other vehicle is automatically controlled during traveling. It is born. When execution of the brake regeneration cooperative control is permitted, the brake ECU 70 receives the braking request and starts the brake regeneration cooperative control as described below. If an abnormality is detected in the system, execution of the brake regenerative cooperative control is prohibited, and the brake ECU 70 generates the required braking force by the hydraulic brake unit 20 without using the regenerative braking force.

As shown in FIG. 5, first, the brake ECU 70 calculates a requested total braking torque F ^* requested by the driver based on a signal from the stroke sensor 25 (S1). Furthermore, the brake ECU 70 receives information necessary for the calculation of the regenerative braking torque such as the value of the regenerative energy absorption rate of the electric motor 6 from the hybrid ECU 7 (S2). The value of the regenerative energy absorption rate of the electric motor 6 is controlled by the motor ECU 14 so as not to exceed the energy receiving capability of the battery 12 at the start of generation of the hydraulic braking force. The setting process of the upper limit value of the regenerative energy absorption rate will be described later with reference to FIG.

Based on the received information, the brake ECU 70 calculates the required regenerative braking torque, and applies the calculated required regenerative braking torque to the hybrid ECU 7 (S3). Here, when the required total braking torque F ^* is smaller than the calculated required regenerative braking torque, the required braking force can be generated without using the hydraulic braking force. The braking torque F ^* is applied to the hybrid ECU 7 as the required regenerative braking torque.

When a signal indicating the required regenerative braking torque is received from the brake ECU 70 in S3, the hybrid ECU 7 gives a signal indicating the required regenerative braking torque to the motor ECU 14. The motor ECU 14 sends a control signal for making the braking torque applied to the left and right front wheels 9FR, 9FL by the electric motor 6 coincide with the required regenerative braking torque to the power converter 11. Then, information indicating the operating state of the regenerative brake unit 10 such as the actual number of revolutions of the electric motor 6 is given from the motor ECU 14 to the hybrid ECU 7. Hybrid ECU7 from these information, calculates the actual regenerative braking torque _{F E} which is actually obtained by the operation of the electric motor 6, and transmits the actual regenerative braking torque _{F E} to the brake ECU 70 (S4).

When the brake ECU 70 receives the actual regenerative braking torque F _E from the hybrid ECU 7, the brake ECU 70 subtracts the actual regenerative braking torque F _E from the required total braking torque F ^*, thereby requesting the required fluid that is the braking torque to be generated by the hydraulic brake unit 20. The pressure braking torque is calculated (S5). Then, the brake ECU 70 calculates the target hydraulic pressure of each of the disc brake units 21FR to 21RL based on the calculated required hydraulic braking torque, and sets the value of the supply current I to the pressure-increasing linear control valve 66 and the pressure-decreasing linear control valve 67. Determine (S6). The routine of FIG. 5 is repeated every predetermined time, for example, every several milliseconds, while the execution of the brake regeneration cooperative control is allowed.

  As a result, in the hydraulic brake unit 20, the brake fluid is supplied from the power hydraulic pressure source 30 to each wheel cylinder 23 via the pressure-increasing linear control valve 66, and braking force is applied to the wheels. Further, brake fluid is discharged from each wheel cylinder 23 through the pressure-reducing linear control valve 67 as necessary, and the braking force applied to the wheel is adjusted.

  At this time, the brake ECU 70 closes the regulator cut valve 65 so that the brake fluid sent from the regulator 33 is not supplied to the main flow path 45. Further, the brake ECU 70 closes the master cut valve 64 and opens the simulator cut valve 68. This is for the purpose of supplying the brake fluid sent from the master cylinder 32 to the stroke simulator 69 in accordance with the operation of the brake pedal 24 by the driver.

  FIG. 6 is a flowchart for explaining the setting process of the upper limit value of the regenerative energy absorption rate in the vehicle braking apparatus according to the present embodiment. The upper limit setting process is started upon receipt of a braking request in a state in which the accelerator pedal is released, and is repeatedly executed by the hybrid ECU 7 at a predetermined cycle during braking. When the process is started, the hybrid ECU 7 first determines whether or not the pressure-increasing linear control valve 66 has been opened (S10). If it is determined that the pressure-increasing linear control valve 66 has not been opened (No in S10), the hybrid ECU 7 ends this process and starts this process again at the next execution timing.

  On the other hand, when it is determined that the pressure-increasing linear control valve 66 has been opened (Yes in S10), the hybrid ECU 7 electrically uses the energy receiving capability of the battery 12 when the pressure-increasing linear control valve 66 is opened. The upper limit value of the regenerative energy absorption rate of the motor 6 is set (S12). When the upper limit value has already been set, the hybrid ECU 7 updates the energy receiving capability of the battery 12 at the time when the pressure-increasing linear control valve 66 is opened as a new upper limit value. Upon receiving the setting of the upper limit value, the motor ECU 14 controls the regenerative energy absorption rate of the electric motor 6 so as not to exceed the upper limit value.

  By setting an upper limit value for the regenerative energy absorption rate, it is possible to prevent fluctuations in the direction in which the regenerative energy absorption rate becomes larger than the upper limit value due to a state change of the battery 12 or the like. Further, since the energy receiving capability of the battery 12 at the time when the pressure-increasing linear control valve 66 is opened, that is, when the hydraulic braking force is generated, is set as an upper limit value, the hydraulic brake unit 20 can be operated promptly from the start of operation. Variations in the hydraulic braking force can be smoothed.

  Note that a value smaller than the energy receiving capability of the battery 12 at the time of opening of the pressure-increasing linear control valve 66 can be set as the above-described upper limit value. However, in order to maximize the energy recovery efficiency, it is preferable to set the energy receiving capacity of the battery 12 to an upper limit value.

  It is also possible to set the energy receiving capacity of the battery 12 before the valve opening of the pressure-increasing linear control valve 66, for example, at the time of a braking request, as the upper limit value. However, if the energy receiving capacity of the battery 12 is increased at the time of opening of the pressure-increasing linear control valve 66 than before the valve opening, in order to maximize the energy recovery efficiency, the pressure-increasing linear control valve 66 It is desirable to update the upper limit value to the value of the energy acceptance capacity at 66 when the valve is opened.

  When the upper limit value of the regenerative energy absorption rate is set, the hybrid ECU 7 determines whether or not the energy receiving capacity of the battery 12 has decreased from the set upper limit value (S14). If a decrease in energy acceptance capability is not detected (No in S14), the hybrid ECU 7 ends this process and starts this process again at the next execution timing. On the other hand, when it is determined that the energy reception capability has decreased (Yes in S14), the hybrid ECU 7 updates the upper limit value of the regenerative energy absorption rate to the value of the energy reception capability after the decrease (S16), and during braking Repeats this setting process.

  The energy receiving capacity of the battery 12 varies depending on the SOC and temperature. When the energy receiving capacity of the battery 12 fluctuates, for example, when it decreases once and increases again, similarly, the regenerative energy absorption rate and the regenerative braking force also decrease once and increase again. . If the hydraulic braking force increase control is being performed, it is necessary to switch from the pressure increase control to the pressure reduction control when the regenerative braking force is increased again, so that the frequency of opening and closing the control valve increases. By updating the upper limit value of the regenerative energy absorption rate in accordance with the decrease in the energy receiving capacity of the battery 12, the re-increase in the regenerative braking force as described above can be suppressed, and the opening / closing frequency of the control valve can be reduced. .

  For the same reason, the hybrid ECU 7 may determine whether or not the regenerative energy absorption rate has decreased from the upper limit value after the regenerative energy absorption rate has reached the set upper limit value. If it is determined that the value has decreased, the hybrid ECU 7 updates the upper limit value of the regenerative energy absorption rate to the value of the regenerative energy absorption rate after the decrease. Each time the regenerative energy absorption rate decreases, the hybrid ECU 7 may update the upper limit value to the value of the regenerative energy absorption rate after the decrease. That is, the hybrid ECU 7 allows a decrease in the regenerative energy absorption rate while prohibiting an increase in the regenerative energy absorption rate while generating the hydraulic braking force. Even if it does in this way, since the increase after the decrease of the regenerative energy absorption rate can be prevented, the open / close frequency of the control valve can be reduced.

  In other words, it can be said that the control unit controls the regenerative brake unit so as to keep the time change rate during braking of the regenerative energy absorption rate below zero. As a result, the regenerative energy absorption rate maintains a constant value or decreases with time, and the frequency of switching between pressure increase control and pressure reduction control in the hydraulic brake unit can be reduced.

  FIG. 7 schematically shows an example of temporal changes in vehicle speed and braking force in this case. FIG. 7 shows a state where the regenerative braking force is reduced by reducing the regenerative energy absorption rate in the region c where the required braking force increases. Since the regenerative energy absorption rate after the decrease is not exceeded, the hydraulic braking force continues to increase monotonously (region e in FIG. 7), and switching to the decompression control is unnecessary.

  As described above, in the present embodiment, the regenerative energy absorption rate is prohibited from increasing beyond the upper limit value. Further, it is preferable that the increase again after the regenerative energy absorption rate once decreases is also prohibited. However, it is not necessary to completely prohibit these increases, and an increase in the regenerative energy absorption rate may be permitted within a range that does not cause switching between the pressure increase control and the pressure decrease control in the hydraulic brake unit. The degree to which the fluctuation of the regenerative energy absorption rate is allowed can be determined based on the design philosophy of how to achieve both the life extension of the hydraulic brake unit and the improvement of the energy recovery efficiency by regeneration.

  By the way, during braking, the pressure-increasing linear control valve 66 may be once closed and then opened again to increase the hydraulic braking force. This occurs, for example, when the brake operation amount of the driver once decreases during braking and then increases again. Or it may be caused by an increase or decrease in regenerative braking force. Thus, when the increase in the hydraulic braking force is resumed during braking, the hybrid ECU 7 may update the energy receiving capability of the battery 12 when the increase in the hydraulic braking force is resumed as the upper limit value of the regenerative energy absorption rate. . In particular, when the energy receiving capacity of the battery 12 is increasing while the pressure increasing linear control valve 66 is closed, the upper limit value can be increased by updating. In such a case, it is desirable to update the upper limit value in order to increase the energy recovery efficiency by regenerative braking.

It is a figure which shows typically an example of the time change of the vehicle speed and braking force at the time of the braking of the vehicle braking device which concerns on one Embodiment of this invention. It is a figure which shows typically an example of the time change of the vehicle speed and braking force at the time of the braking of the conventional vehicle braking device. 1 is a schematic configuration diagram illustrating a vehicle to which a vehicle braking device according to an embodiment is applied. It is a systematic diagram showing a hydraulic brake unit concerning this embodiment. It is a flowchart for demonstrating the brake regeneration cooperative control in the vehicle braking device of this embodiment. It is a flowchart for demonstrating the setting process of the upper limit of the regenerative energy absorption rate in the vehicle braking device which concerns on this embodiment. It is a figure which shows typically an example of the time change of the vehicle speed and braking force at the time of the braking of the vehicle braking device which concerns on one Embodiment of this invention.

Explanation of symbols

  6 electric motor, 7 hybrid ECU, 10 regenerative brake unit, 12 battery, 14 motor ECU, 20 hydraulic brake unit, 23 wheel cylinder, 24 brake pedal, 30 power hydraulic pressure source, 66 pressure-increasing linear control valve, 70 brake ECU .

Claims (4)

A regenerative brake unit that generates regenerative braking force by regenerative control of the electric motor;
A hydraulic brake unit that generates a hydraulic braking force by supplying hydraulic fluid from a hydraulic pressure source in order to supplement the regenerative braking force and apply a required braking force to the wheels;
While generating the hydraulic braking force, the increase in the regenerative energy absorption rate is limited so that the regenerative energy absorption rate does not exceed the upper limit set from the time when the braking is requested until the start of the generation of the hydraulic braking force. A control unit that controls the regenerative brake unit to allow a decrease in absorption rate; and
A vehicle braking device comprising: A storage battery for storing electrical energy obtained by regenerative control of the electric motor;
2. The vehicle braking device according to claim 1, wherein the control unit sets an energy receiving capability of the storage battery at the time of the braking request as the upper limit value. A storage battery for storing electrical energy obtained by regenerative control of the electric motor;
2. The vehicle braking device according to claim 1, wherein the control unit sets the energy receiving capacity of the storage battery at the start of generation of the hydraulic braking force as the upper limit value. Wherein, when the regenerative energy absorption rate has decreased after reaching the upper limit value, wherein the regenerative energy absorption rate after reduction to any one of claims 1 to 3, characterized by updating the upper limit value Vehicle braking device.

Images