JP2012153181A - Hydraulic brake system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent erroneous detection in a self-diagnosis function of a brake system in a situation that a temperature of an operating fluid is lowered.SOLUTION: The brake system is so structured that when a liquid pressure generated by a power liquid pressure source device continues to be lower than a threshold liquid pressure Pfor a threshold continuing time Tor longer in travelling, supply of the operating liquid to a brake cylinder is switched from the power liquid pressure source device to a master cylinder device. The brake system is structured so as to achieve at least one of a value P' which is a lower threshold liquid pressure, and a value T' which is a longer threshold continuing time when it is estimated that the temperature of the operating fluid is lowered more than a set temperature. Erroneous diagnosis, that the power liquid pressure source device is abnormal, can be prevented in a situation that the temperature of the operating fluid is lower than the set temperature.

Description

  The present invention relates to a hydraulic brake system including a hydraulic brake device that operates by hydraulic pressure of hydraulic fluid to apply a braking force to a wheel.

  The hydraulic brake system described in Patent Document 1 below is a power hydraulic pressure source device that pressurizes hydraulic fluid based on a force generated by a power source without depending on an operating force applied to a brake operation member by a driver. And a hydraulic pressure adjusting device that adjusts the hydraulic pressure generated by the power hydraulic pressure source device, and the braking force can be controlled. In such a brake system, when it is detected that the braking force cannot be normally controlled, the supply of hydraulic fluid from the power hydraulic pressure source device to the brake cylinder is cut off and added to the brake operation member. The hydraulic fluid is supplied to the brake cylinder from the master cylinder device that pressurizes the hydraulic fluid depending on the operated force, and is configured to generate a braking force according to the operation of the brake operation member. That is, it is configured to switch to a so-called backup mode when the brake system is abnormal. For example, the brake system described in Patent Document 1 below is configured to switch to the backup mode when a large difference between the target hydraulic pressure of the brake cylinder and the actual hydraulic pressure continues.

JP 2009-143265 A

  When switching to the backup mode described above, there is a system configured to manually return to the normal brake mode using a dedicated tool or the like from the viewpoint of fail-safe. In such a system, if an abnormality in the brake system is erroneously detected, even if the system is normal, it is necessary to suppress wheel locking, skidding, etc. until the brake mode is restored. There is a problem that the braking force cannot be controlled. This invention is made | formed in view of such a situation, and makes it a subject to prevent it being diagnosed as abnormality of a brake system accidentally.

  In order to solve the above-described problem, the hydraulic brake system of the present invention, when traveling, when the hydraulic pressure generated by the power hydraulic pressure source device is lower than the threshold hydraulic pressure continues for a threshold duration or longer, The supply of the hydraulic fluid to the brake cylinder is switched from the power hydraulic pressure source device to the master cylinder device, and when it is estimated that the temperature of the hydraulic fluid is lower than the set temperature, the threshold fluid It is configured to perform at least one of lowering the pressure and increasing the threshold duration.

  During sudden braking, it may be detected by a sensor or the like that the amount of hydraulic fluid received relative to the amount of hydraulic fluid supplied by the power hydraulic pressure source device is insufficient and the hydraulic pressure temporarily decreases. is there. When the temperature of the hydraulic fluid is lowered and the viscosity is increased, the detection result of the hydraulic pressure may satisfy the condition for switching to the backup mode. In the hydraulic brake system of the present invention, when the temperature of the hydraulic fluid is low, the switching condition is changed so that it is difficult to switch to the backup mode. That is, according to the hydraulic brake system of the present invention, it is possible to avoid erroneously diagnosing an abnormality of the power hydraulic pressure source device in a situation where the temperature of the hydraulic fluid is lower than the set temperature. It is.

Aspects of the Invention

  In the following, some aspects of the invention that can be claimed in the present application (hereinafter sometimes referred to as “claimable invention”) will be exemplified and described. As with the claims, each aspect is divided into sections, each section is numbered, and is described in a form that cites the numbers of other sections as necessary. This is merely for the purpose of facilitating the understanding of the claimable inventions, and is not intended to limit the combinations of the constituent elements constituting those inventions to those described in the following sections. In other words, the claimable invention should be construed in consideration of the description accompanying each section, the description of the embodiments, etc., and as long as the interpretation is followed, another aspect is added to the form of each section. In addition, an aspect in which some constituent elements are deleted from the aspect of each item can be an aspect of the claimable invention.

  In each of the following items, the item (1) corresponds to the item (1), and the technical features described in the item (3) are added to the item (1). The technical feature described in (5) is added to Claim 3, and the technical feature described in (5) is added to Claim 2 or Claim 3, in Claim 4, or from 2 to 3. The technical feature described in (6) is added to any one of claims 4 and corresponds to claim 5, respectively.

(1) a brake operation member operated by a driver;
A brake device provided corresponding to the wheel, having a brake cylinder, and operating by a hydraulic pressure of hydraulic fluid supplied to the brake cylinder to apply a braking force to the wheel;
A master cylinder device that pressurizes the hydraulic fluid based on an operating force applied to the brake operating member;
A power-type hydraulic pressure source device that has a power source and pressurizes hydraulic fluid depending on the force generated by the power source;
A hydraulic pressure adjusting device for adjusting the hydraulic pressure of the hydraulic fluid generated by the power hydraulic pressure source device;
(a) A first state in which the supply of hydraulic fluid from the master cylinder device to the brake cylinder is shut off and the supply of hydraulic fluid from the power hydraulic pressure source device to the brake cylinder is allowed in a normal state. And controlling the hydraulic pressure adjusting device to adjust the hydraulic pressure of the hydraulic fluid, thereby controlling the braking force applied to the wheels, and (b) When the hydraulic pressure generated by the pressure source device is lower than the threshold hydraulic pressure for a threshold duration or longer, the supply of hydraulic fluid from the power hydraulic pressure source device to the brake cylinder is interrupted; and Switching to a second state in which the supply of hydraulic fluid from the master cylinder device to the brake cylinder is allowed, and a realization state switching unit for generating a braking force according to the operation of the brake operation member; and (c) the temperature of the hydraulic fluid is Set temperature A switching condition changing unit that performs at least one of lowering the threshold liquid pressure and increasing the threshold duration when it is estimated that the liquid temperature state is a lower state. A control device comprising:
Hydraulic brake system with

  The hydraulic brake system described in this section includes two hydraulic pressure sources, that is, a master cylinder device and a powered hydraulic pressure source device. Normally, hydraulic fluid is supplied from the powered hydraulic pressure source device, and the power It is assumed that hydraulic fluid is supplied from the master cylinder device when the hydraulic fluid pressure source device is abnormal. The “powered hydraulic pressure source device” may include a pump device that operates by receiving electric power to generate hydraulic pressure. Further, the power-type hydraulic pressure source device may include an accumulator that stores hydraulic fluid in a pressurized state. The “hydraulic pressure adjusting device” that adjusts the hydraulic pressure generated by the power-type hydraulic pressure source device may include an electromagnetic control valve that controls the hydraulic fluid in accordance with the electric power supplied to itself. The hydraulic pressure adjusting device can include a device that adjusts the hydraulic pressure of a brake cylinder provided corresponding to each wheel. Furthermore, the hydraulic pressure adjusting device is provided between the device for adjusting the hydraulic pressure of the brake cylinder and the power hydraulic pressure source device separately from the device for adjusting the hydraulic pressure of the brake cylinder. A device for adjusting the output hydraulic pressure of the device may be included.

  In a brake system equipped with a power hydraulic pressure source device as described above, if an abnormality occurs in which the power hydraulic pressure source device cannot generate a sufficient fluid pressure, the master cylinder device removes hydraulic fluid. It is configured to shift to a state in which supply is performed (the second state, hereinafter sometimes referred to as “backup mode”). The abnormality of the power hydraulic pressure source device is determined by whether or not the state in which the hydraulic pressure generated by the power hydraulic pressure source device is lower than the threshold hydraulic pressure has continued for a threshold duration or longer.

  However, in a brake system equipped with a power hydraulic pressure source device, the amount of hydraulic fluid received may be insufficient with respect to the amount of hydraulic fluid supplied by the power hydraulic pressure source device during sudden braking. In that case, although temporarily, the sensor or the like detects that the output hydraulic pressure of the power hydraulic pressure source device is low. Further, the decrease in the output hydraulic pressure of the power type hydraulic pressure source device appears more prominently when the temperature of the hydraulic fluid is low, that is, when the viscosity of the hydraulic fluid is high. Specifically, the decrease in the output hydraulic pressure of the power hydraulic pressure source device increases the amount of decrease or increases the time until recovery to the controlled level. In other words, when the temperature of the hydraulic fluid is low, there is a possibility that the switching condition for switching to the backup mode may be satisfied, and if the condition is satisfied, the backup mode Will be transferred to.

  In the hydraulic brake system described in this section, in a situation where the temperature of the hydraulic fluid is decreasing, at least one of lowering the threshold hydraulic pressure and increasing the threshold duration is performed. The threshold is configured to change. In other words, according to the hydraulic brake system described in this section, the switching condition to the backup mode is changed and the transition to the backup mode is difficult under the condition that the temperature of the hydraulic fluid is lowered. As a result, abnormalities in the power-type hydraulic pressure source device are not detected by mistake, and braking force control to prevent wheel locks, skidding, etc. is restored to the brake mode even if the system is normal. It is possible to avoid a situation in which it cannot be performed until it is performed.

  The “low liquid temperature state” described in this section refers to a state where the temperature of the hydraulic fluid is low and the viscosity of the hydraulic fluid is high. Whether or not it is in the low liquid temperature state may be detected directly from the estimation result under the situation where the vehicle is parked, as will be described in detail later, as the temperature of the hydraulic fluid may be directly detected. May be.

(2) The power type hydraulic pressure source device is
It has an accumulator that stores hydraulic fluid in a pressurized state, and is controlled so that the pressure of the hydraulic fluid stored in the accumulator becomes a pressure within a pressure accumulation range that is a pressure within a set range.
The hydraulic brake system according to item (1), wherein the threshold pressure is set to be a difference in which a difference from a lower limit value of the pressure in the pressure accumulation range is determined.

  In the aspect described in this section, the threshold fluid pressure that is the switching condition from the first state to the second state is embodied in the realization state switching unit. The threshold fluid pressure is preferably lower by some margin than the lower limit value of the pressure in the pressure accumulation range, but depending on the relationship with the threshold duration, it may be the same value as the lower limit value or higher than the lower limit value. It may be a value.

(3) The controller is
When starting the vehicle, it is estimated whether or not the vehicle has not been started for a set time or more, and whether or not the outside air temperature is lower than the set temperature, is estimated that the vehicle has not been started for the set time or more, and When it is estimated that the temperature is lower than the set temperature, the low liquid temperature state estimation unit that estimates that the low liquid temperature state is present,
The switching condition changing unit is
Item (1) or (2) configured to change at least one of the threshold fluid pressure and the threshold duration when the low fluid temperature state estimation unit estimates that the fluid is in the low fluid temperature state ) Hydraulic brake system according to item.

  In the aspect described in this section, a method for estimating whether or not there is a low liquid temperature state is embodied. To put it flatly, the aspect described in this section is estimated to be in a low liquid temperature state when the vehicle is parked for a long time in a place where the temperature is low. The method for estimating “whether the vehicle has not been started for a set time or more” and “whether the outside temperature is lower than the set temperature” is not particularly limited. For example, “whether or not the vehicle has not been started for a set time or longer” may be estimated based on, for example, the time at the time of starting and the time immediately before parking the vehicle in the previous time. It may be estimated based on the degree of decrease in accumulator pressure or the like. Further, “whether or not the outside temperature is lower than the set temperature” may be estimated based on, for example, the time or temperature at the time of starting the vehicle, and as will be described in detail later, You may estimate based on a use condition.

(4) The power type hydraulic pressure source device is
It has an accumulator that stores hydraulic fluid in a pressurized state, and is controlled so that the pressure of the hydraulic fluid stored in the accumulator becomes a pressure within a pressure accumulation range that is a pressure within a set range.
The low liquid temperature state estimation unit,
The hydraulic brake system according to (3), wherein whether the vehicle has not been started for a set time or longer is estimated based on the pressure of the hydraulic fluid stored in the accumulator when the vehicle is started.

  In the aspect described in this section, a technique for estimating “whether or not the vehicle has been started for a set time or more” is embodied. Since the hydraulic fluid stored in the accumulator gradually leaks from the control valve etc. provided in the brake system, the accumulator pressure, which is the pressure of the hydraulic fluid stored in the accumulator, gradually decreases and the pressure of the low pressure source (atmospheric pressure) Will fall to. Therefore, based on the accumulator pressure, it is possible to estimate the time when the vehicle is parked, that is, it is possible to estimate “whether the vehicle has not been started for a set time or more”. According to the aspect of this section, since it is estimated from information used for control of the brake system, it is not necessary to acquire other information from another control device or the like. As a result, for example, the communication capacity with other control devices decreases, so that parts having a small capacity can be adopted for the communication, and the system can be simplified and miniaturized.

(5) The low liquid temperature state estimation unit includes:
The hydraulic brake system according to (3) or (4), wherein whether or not the outside air temperature is lower than a set air temperature is estimated based on a use state of a heating device mounted on the vehicle.

  In the aspect described in this section, a method for estimating “whether or not the outside temperature is lower than the set temperature” is embodied. The aspect of this section is configured to estimate, for example, whether the heating device is operating at the time of starting the vehicle, or whether the heating device is operating immediately before parking the vehicle last time. Can do. Further, in the aspect of this section, for example, the set temperature of the heating device can be used as an index for estimating whether the set temperature of the heating device is equal to or higher than a threshold temperature.

(6) The control device
A liquid temperature recovery estimation unit that estimates whether or not the temperature of the hydraulic fluid has recovered to a set temperature after being estimated by the low liquid temperature state estimation unit to be in the low liquid temperature state;
The switching condition changing unit is
When the temperature of the hydraulic fluid is estimated to have recovered to a set temperature by the liquid temperature recovery estimation unit, at least one of the changed threshold fluid pressure and the threshold duration is returned to the value before the change. The hydraulic brake system according to any one of (3) to (5), which is configured.

(7) The liquid temperature recovery estimation unit
The hydraulic brake system according to item (6), wherein when the number of times of operation of the brake operation member after the vehicle is started exceeds a set number of times, it is estimated that the temperature of the hydraulic fluid has recovered to the set temperature.

  The system described in the above two sections is configured to restore the changed threshold. That is, according to the aspects described in the above two items, even when the temperature of the hydraulic fluid is lowered, the threshold value is restored with the recovery of the temperature of the hydraulic fluid. This realizes a system in which the condition for detecting the abnormality is made appropriate according to the temperature of the hydraulic fluid.

  The estimation method of “whether or not the temperature of the hydraulic fluid has recovered to the set temperature” by the “liquid temperature recovery estimation unit” described in the former aspect of the above two aspects is not particularly limited. For example, the elapsed time since the vehicle was started (specifically, the elapsed time since the engine or the like was started and the vehicle was allowed to travel) or the brake operation as in the latter mode A method of estimating based on the number of operations of the member can be employed. Furthermore, for example, the configuration may be such that the number of times of brake operation is indirectly estimated based on the number of times the drive source of the power hydraulic pressure source device is actuated or the fluctuation of the accumulator pressure.

  In addition, according to the latter aspect, since it estimates from the information used for the control of the said brake system, it is not necessary to acquire the detected value of a thermometer from other control apparatuses etc., for example, communication with other control apparatuses It is possible to reduce the cost of the system by assuming that the parts required for the system have a small capacity.

It is the schematic of the brake circuit with which the hydraulic brake system which is an Example of claimable invention is provided. It is a schematic sectional drawing which shows the linear valve for pressure increase shown in FIG. 1, and the linear valve for pressure reduction. It is a figure which shows the flow of the hydraulic fluid in the 1st state while showing the 1st state implement | achieved when a system is normal. It is a figure which shows the flow of the hydraulic fluid in the 2nd state while showing the 2nd state implement | achieved at the time of failure of an accumulator. It is a figure which shows the change of the accumulator pressure at the time of vehicle starting. It is a figure which shows the change of the accumulator pressure at the time of operation which becomes a sudden brake in a low liquid temperature state. It is a flowchart showing the switching condition determination program performed by the brake electronic control unit which is a control apparatus which manages control of the hydraulic brake system which is an Example of claimable invention. It is a flowchart showing the switching condition return program performed by the brake electronic control unit which is a control apparatus which manages control of the hydraulic brake system which is an Example of claimable invention. It is a block diagram which shows the function of the control apparatus which manages control of the hydraulic brake system which is an Example of claimable invention.

  Hereinafter, representative embodiments of the claimable invention will be described in detail with reference to the drawings. In addition to the following examples, the claimable invention is implemented in various modes including various modifications and improvements based on the knowledge of those skilled in the art, including the mode described in the above [Mode of Invention]. can do.

<Configuration of hydraulic brake system>
The hydraulic brake system which is an embodiment of the claimable invention includes the brake circuit shown in FIG. This hydraulic brake system includes a brake pedal 10 as a brake operation member, a manual hydraulic pressure source device 12 that pressurizes hydraulic fluid based on a pedaling force applied to the brake pedal 10, and a force generated by a power source. Power hydraulic pressure source device 14 that pressurizes the hydraulic fluid on the basis of the above, four hydraulic brake devices 18 provided on the front, rear, left and right wheels 16, respectively, the two hydraulic pressure source devices 12, 14 and the brake device 18 and a brake actuator 20 serving as a hydraulic pressure adjusting device that adjusts the hydraulic pressure generated by the power hydraulic pressure source device 14. It should be noted that some components such as “wheel 16” are used as a generic term, but when indicating that they correspond to any of the four wheels, the left front wheel, the right front wheel, the left rear wheel, The subscripts “FL”, “FR”, “RL”, and “RR” are assigned to the right rear wheel, respectively.

  Each of the four brake devices 18 has a brake cylinder 22, which is actuated by the hydraulic pressure of the brake cylinder 22 to apply a braking force to the wheel 16. In the present embodiment, the disk brake is a disk brake that presses a brake pad as a friction material held by a non-rotating body against the disk rotor as a brake rotating body that rotates together with the wheels 18 by the hydraulic pressure of the brake cylinder 22.

  The manual hydraulic pressure source device 12 includes a hydraulic pressure booster 30 and a master cylinder 32. The hydraulic booster 30 is linked to a hydraulic pressure adjusting unit (regulator, indicated as reg in FIG. 1) 34 that generates a hydraulic pressure higher than the hydraulic pressure corresponding to the operating force applied to the brake pedal 10, and the brake pedal 10. And a booster chamber 38 provided behind the power piston 36. The hydraulic pressure adjusting unit 34 includes a spool valve, a pressure adjusting chamber, and the like (not shown), and is connected to the power hydraulic pressure source device 14 and to the reservoir 40. The movement of the spool valve accompanying the operation of the brake pedal 10 causes the pressure regulating chamber to selectively communicate with the power hydraulic pressure source device 14 or the reservoir 40, and the hydraulic pressure in the pressure regulating chamber becomes a magnitude corresponding to the operating force. Adjusted. By supplying the hydraulic fluid in the pressure adjusting chamber (the hydraulic fluid adjusted by the hydraulic pressure adjusting unit 34) to the booster chamber 38, a forward force is applied to the power piston 36, and the operating force is assisted. .

  The master cylinder 32 includes a pressurizing piston 50 linked to the power piston 36 described above and a pressurizing chamber 52 provided in front of the pressurizing piston 50. As the power piston 36 advances, the pressurizing piston 50 is advanced, and a hydraulic pressure is generated in the pressurizing chamber 52.

  When the brake pedal 10 is depressed, the power piston 36 is advanced, and the pressurizing piston 50 is advanced accordingly. The booster chamber 38 is supplied with the hydraulic pressure adjusted to a magnitude corresponding to the operating force in the hydraulic pressure adjusting unit 34. The pressurizing piston 50 is advanced by a force that combines an operating force and an assisting force (a force corresponding to the hydraulic pressure of the booster chamber 76), and a hydraulic pressure having a magnitude corresponding to the force is applied to the pressurizing chamber 52. Be generated. In the present embodiment, the hydraulic pressure of the hydraulic pressure adjusting unit 34 and the hydraulic pressure of the pressurizing chamber 52 are set to be substantially the same.

  The power type hydraulic pressure source device 14 includes a pump 60 that pumps hydraulic fluid from the reservoir 40, a pump motor 62 as a power source that drives the pump 60, and hydraulic fluid discharged from the pump 60 in a pressurized state. And an accumulator 64 for storing. The pump motor 62 is controlled such that the pressure of the hydraulic fluid stored in the accumulator 64 is within a predetermined range. The power hydraulic pressure source device 14 also has a relief valve 66 that regulates the discharge pressure of the pump 60 to a set value or less, so that the discharge pressure of the pump 60 is prevented from becoming excessive.

  The power-type hydraulic pressure source device 14, the hydraulic pressure adjusting unit 34 of the hydraulic pressure booster 30, and the pressurizing chamber 52 of the master cylinder 32 are connected to the brake actuator 20. More specifically, the power hydraulic pressure source device 14, the hydraulic pressure adjusting unit 34 of the hydraulic booster 30, and the pressurizing chamber 52 of the master cylinder 32 are connected to a control pressure passage 70, a booster passage 72, and a master passage 74, respectively. The control pressure passage 70, the booster passage 72, and the master passage 74 are connected to a common passage 76 that the brake actuator 20 has. The common passage 76 is connected to brake cylinders 22FR, 22FL, 22RR, and 22RL corresponding to the wheels 16FR, 16FL, 16RR, and 16RL via individual passages 78FR, 78FL, 78RR, and 78RL, respectively. Has been. Further, the common passage 76 is connected to the reservoir 40 via the low pressure passage 80.

  The brake actuator 20 has an output hydraulic pressure control valve device 90 that adjusts the pressure of the hydraulic fluid stored in the accumulator 64, that is, the hydraulic pressure output from the power hydraulic pressure source 14. The output hydraulic pressure control valve device 90 connects the pressure increasing linear valve 92 provided in the control pressure passage 70 connecting the power hydraulic pressure source device 14 and the common passage 76, the common passage 76 and the reservoir 40. And a pressure reducing linear valve 94 provided in the low pressure passage 80. The pressure-increasing linear valve 92 can control the flow of hydraulic fluid from the power hydraulic pressure source device 14 to the common passage 76, while the pressure-decreasing linear valve 94 is a reservoir in the common passage 76. It is possible to control the outflow of hydraulic fluid to 40. The pressure-increasing linear valve 92 and the pressure-decreasing linear valve 94 have a predetermined fixed relationship between the hydraulic pressure difference between the high-pressure side hydraulic fluid and the low-pressure side hydraulic fluid and the supply current. The valve opening pressure can be changed accordingly. Therefore, the pressure-increasing linear valve 92 and the pressure-decreasing linear valve 94 can continuously change the supply pressure, which is the hydraulic pressure of the hydraulic fluid supplied to the common passage 76, by controlling the supply current. It is possible to control to an arbitrary height.

  Specifically, as shown in FIG. 2, each of the pressure-increasing linear valve 92 and the pressure-decreasing linear valve 94 includes a seating valve including a valve body 100 and a valve seat 102, a spring 104, and a solenoid 106. It has. The urging force F1 of the spring 104 acts in a direction in which the valve body 100 approaches the valve seat 102, and when a current is supplied to the solenoid 106, the driving force F2 acts in a direction in which the valve body 100 is separated from the valve seat 102. To do. In the pressure-increasing linear valve 92, the differential pressure acting force F3 corresponding to the differential pressure between the hydraulic pressure of the hydraulic fluid pressurized by the power-type hydraulic pressure source device 14 and the supply pressure causes the valve body 100 to move to the valve seat 102. In the pressure reducing linear valve 94, the pressure of the hydraulic fluid stored in the reservoir 40, that is, the differential pressure acting force F3 corresponding to the pressure difference between the atmospheric pressure and the supply pressure is applied to the valve body. It acts in a direction to separate 100 from the valve seat 102. Therefore, in both the pressure-increasing linear valve 92 and the pressure-reducing linear valve 94, the differential pressure acting force F3 is controlled by controlling the energization amount to the solenoid 106, and the pressure-increasing linear valve 92 and the pressure-decreasing linear valve. The valve opening pressure of 94 can be controlled. In other words, the supply pressure can be changed in a controllable manner by causing the pressure-increasing linear valve 92 and the pressure-decreasing linear valve 94 to function as a differential pressure valve.

  The brake actuator 20 has an individual hydraulic pressure control valve device 110 for adjusting the hydraulic pressure of each of the four brake cylinders 22FR, 22FL, 22RR, 22RL. The individual hydraulic pressure control valve device 110 includes four holding valves 112FR, 112FL, 112RR, 112RL provided in each of the individual passages 78FR, 78FL, 78RR, 78RL described above, and each of the four holding valves 112. Four pressure reducing valves 114FR, 114FL, 114RR, 114RL provided between the reservoir 40 and the reservoir 40 are configured. The holding valve 112 is a normally open electromagnetic control valve that is open when no current is supplied to the solenoid, and is for increasing and holding the hydraulic pressure in the brake cylinder 22. The pressure reducing valve 114 is a normally closed electromagnetic control valve that is in a closed state when no current is supplied to the solenoid, and for reducing the hydraulic pressure in the brake cylinder 22.

  The common passage 76 is provided with a communication valve 120 between a portion to which the left and right front wheels 16FR and 16FL are connected and a portion to which the left and right rear wheels 16RR and 16RL are connected. That is, the communication valve 120 is in a state where the brake cylinders 22RR, 22RL corresponding to the left and right rear wheels 16RR, 16RL are in communication with the brake cylinders 22FR, 22FL corresponding to the left and right front wheels 16FR, 16FL, Are to be switched. The communication valve 120 is a normally closed electromagnetic control valve that is closed when no current is supplied to the solenoid. The communication valve 120 is normally opened, and the hydraulic fluid from the pressure-increasing linear valve 92 described above is not limited to the brake cylinders 22RR and 22RL corresponding to the left and right rear wheels 16RR and 16RL. The brake cylinders 22FR and 22FL corresponding to the front wheels 16FR and 16FL are connected to each other so as to be supplied.

  Further, the brake actuator 20 has a regulator cut valve 130 provided in the booster passage 72 and a master cut valve 132 provided in the master passage 74. The regulator cut valve 130 and the master cut valve 132 are both normally open electromagnetic control valves that are open when no current is supplied to the solenoid. In the middle of the master passage 72, a stroke simulator 134 is connected via a simulator cut valve 136 which is a normally closed electromagnetic control valve.

  This brake system includes a brake electronic control unit (hereinafter, also referred to as “brake ECU” or simply “ECU”) 150 as a control device. The ECU 150 is connected to the pump motor 62 of the power hydraulic pressure source device 14 and the electromagnetic control valves 92, 94, 112, 114, 130, 132, 136 that the brake actuator 20 has. 62 and each electromagnetic control valve are controlled to control the hydraulic pressure of the brake cylinder 22 of each brake device 18. Incidentally, the ECU 150 also has a driver circuit for controlling the operation of the electromagnetic motor and the electromagnetic control valve.

  The hydraulic brake system includes various sensors as devices for acquiring control parameters, and these sensors are also connected to the brake ECU 150. Specifically, the stroke sensor 160 that detects the operation amount of the brake pedal 10 and the control pressure passage 70 are provided in the accumulator pressure sensor 162 that detects the pressure of hydraulic fluid stored in the accumulator 64 and the booster passage 72. The regulator pressure sensor 164 for detecting the hydraulic pressure of the hydraulic pressure adjusting unit 34 of the hydraulic pressure booster 30 generated according to the operating force applied to the brake pedal 10 by the driver is provided in the common passage 76 and provided in the common passage 76. A brake cylinder pressure sensor 166 that detects the hydraulic pressure of the brake cylinder 22 by detecting the hydraulic pressure of the brake cylinder 22 is connected to the ECU 150.

<Control in hydraulic brake system>
In the present hydraulic brake system, the power hydraulic pressure source device 14 is controlled by controlling the pressure increasing linear valve 92 and the pressure reducing linear valve 94, the regulator cut valve 130, and the master cut valve 132 of the output hydraulic pressure control valve device 90. One or more of the hydraulic booster 30 and the master cylinder 32 included in the manual hydraulic pressure source device 12 can be selectively communicated with the common passage 76. In the brake system, the first state as shown in FIG. 3 is realized in a normal state. Specifically, the regulator cut valve 130 and the master cut valve 132 are closed, and the supply of hydraulic fluid from the manual hydraulic pressure source device 12 is shut off, and the solenoid 106 of the pressure increasing linear valve 92 and the pressure reducing linear valve 94 is supplied. Is supplied, the hydraulic fluid is supplied from the power hydraulic pressure source device 14. In this case, the communication valve 120 is opened and the simulator cut valve 142 is opened. The brake cylinder 22 is operated by the hydraulic fluid supplied by the power hydraulic pressure source device 14 by opening all the four holding valves 112 and closing all the pressure reducing valves 114.

Since the control at the normal time is a known control, it will be briefly described. When the brake pedal 10 is operated by the driver, the target braking force is determined based on the detection results of the stroke sensor 160 and the regulator pressure sensor 164, and the output hydraulic pressure control valve device is set so as to be the target braking force. 90 is controlled. The power hydraulic pressure source device 14 is controlled so that the accumulator pressure Pacc becomes a pressure in a pressure accumulation range (P _min <Pacc <P _max ) that is a pressure within a set range. Specifically, when the accumulator pressure Pacc detected by the accumulator pressure sensor 162 is lower than the pressure in the pressure accumulation range, the pump motor 62 is operated, and when the pressure in the pressure accumulation range is reached, the operation of the pump motor 62 is stopped. It has come to be. In this brake system, control to stabilize the behavior of the vehicle, ABS (Anti-lock Brake System) control to suppress wheel lock during sudden braking, etc. VSC (Vehicle Stability Control) control for suppressing, TRC (Traction Control) control for suppressing idling of the driving wheel at the time of vehicle start, sudden acceleration, etc. is executed, and rotation of each wheel 16 is performed. Based on the speed, slip ratio, etc., the holding valve 112 and the pressure reducing valve 114 of the individual hydraulic pressure control valve device 110 are controlled.

<Switch to backup mode>
i) Outline of Backup Mode In this brake system, when an abnormality occurs in the system, hydraulic fluid is supplied from the manual hydraulic pressure source device 12 instead of the power hydraulic pressure source device 14. ing. For example, when a failure occurs in the power hydraulic pressure source device 14 and the accumulator 64 cannot accumulate pressure, the second state shown in FIG. 4 is realized. Specifically, the pressure-increasing linear valve 92 and the pressure-decreasing linear valve 94 are closed, the supply of hydraulic fluid from the power hydraulic pressure source device 14 is shut off, the regulator cut valve 130 is closed, and the master cut is performed. The valve 132 is opened and hydraulic fluid is supplied from the master cylinder 32. In this case, the communication valve 120 is closed and the simulator cut valve 142 is closed. The brake cylinders 22FR and 22FL corresponding to the left and right front wheels 16FR and 16FL are moved by the hydraulic fluid supplied from the master cylinder 32 by opening all the four holding valves 112 and closing all the pressure reducing valves 114. It works.

  For example, when the operation of the brake actuator 20 is stopped due to a failure or the like, each electromagnetic control valve is not supplied with current, and the second state shown in FIG. 4 is realized. However, since the power hydraulic pressure source device 14 is normal, hydraulic fluid is supplied not only from the master cylinder 32 but also from the hydraulic booster 30, and the brake cylinders 22 corresponding to all the four wheels 16 are operated.

ii) Switching condition and change of the switching condition In the present brake system, a determination for detecting a failure that cannot accumulate pressure in the accumulator 64 is always performed. Specifically, the accumulator pressure sensor 162 accumulator pressure Pacc detected by the, if閾液pressure P _B from the low state becomes the threshold duration T _B above, the second state is realized as described above, backup mode Can be switched to. The threshold fluid pressure P _B is set to a value (P _min −ΔP) that is lower by a difference ΔP that is defined as a difference from the lower limit value P _min of the fluid pressure in the pressure accumulation range.

  For example, when an operation of applying a sudden brake is performed by the driver, the supply amount of the hydraulic fluid from the accumulator 64 increases rapidly, so that the supply of the hydraulic fluid to the accumulator 64 by the pump motor 62 is not in time, and temporarily However, the accumulator pressure may be low. Furthermore, when the temperature of the hydraulic fluid is lowered and the viscosity of the hydraulic fluid is increased, the decrease in accumulator pressure Pacc accompanying sudden braking is the time until the amount of decrease increases or the pressure is restored to the pressure in the pressure accumulation range. Will become longer. That is, when the temperature of the hydraulic fluid is low, the above switching condition for switching to the backup mode may be satisfied. If the switching condition is satisfied, the system is shifted to the backup mode even though there is no abnormality in the system. Therefore, in this hydraulic brake system, it is estimated whether or not the temperature of the hydraulic fluid is low, and when it is estimated that the temperature of the hydraulic fluid is low, it is difficult to shift to the backup mode due to the above switching condition. Therefore, the switching condition is changed. Hereinafter, the change of the switching condition will be described in detail.

  The estimation of whether or not the hydraulic fluid is in a low fluid temperature state where the temperature of the hydraulic fluid is lower than the set temperature is performed based on whether or not the vehicle equipped with the brake system has been parked in a place where the temperature is low for a long time. Specifically, when starting the vehicle, it is estimated whether or not the vehicle has been started for a set time or more, and whether or not the outside air temperature is lower than the set temperature, and the vehicle has not been started for the set time or more. When it is estimated and the outside air temperature is estimated to be lower than the set air temperature, it is estimated that the liquid temperature state is low.

Specifically, first, whether or not the vehicle has been started for a set time or longer is estimated based on the detection result of the accumulator pressure sensor 162. When the vehicle is parked, the hydraulic fluid stored in the accumulator 64 gradually leaks from the spool valve of the hydraulic pressure booster 30, and the accumulator pressure is reduced to atmospheric pressure. When the accumulator pressure is reduced to the atmospheric pressure, that is, when the accumulator pressure is the atmospheric pressure P ₀ at the start of the vehicle, it is estimated that the vehicle has not been started for a set time or more. Note that when accumulator pressure is accumulated from a state where the pressure has decreased to atmospheric pressure, the accumulator pressure rapidly increases up to the enclosed pressure of the accumulator 64 as shown in FIG. Therefore, when the increase gradient ΔPacc of the accumulator pressure after the start of the vehicle is larger than the set gradient, it may be estimated that the vehicle has not been started for a set time or more.

  Next, the estimation of whether or not the outside air temperature is lower than the set air temperature is performed based on the usage state of the heating device 180 (see FIG. 9) mounted on the vehicle. It is estimated that the outside air temperature was lower than the set temperature when the heating device 180 was used immediately before parking the vehicle last time, or when the heating device 180 is used immediately after the vehicle is started this time.

When it is estimated by the above estimation method that the vehicle has not been started for a set time or more and the outside air temperature is lower than the set temperature, and it is estimated that the vehicle is in a low liquid temperature state, 'together are in the threshold duration is longer T _B than T _B' pressure is low P _B from P _B is adapted to be. As shown in FIG. 6, even if an operation of applying a sudden brake is performed by changing these threshold values, the changed switching condition is not satisfied, and switching to the backup mode is avoided.

In addition, after it is estimated that the fluid temperature is low, it is estimated whether or not the temperature of the hydraulic fluid has recovered to normal after exceeding the set temperature, and when it is estimated that the temperature of the hydraulic fluid has recovered. The switching conditions that have been changed are restored to the original. Specifically, based on the number of brake operations after the vehicle is started, it is estimated whether or not the temperature of the hydraulic fluid has recovered. More specifically, the number of braking operations is counted based on the detection result of the stroke sensor 160, and the changed switching condition is returned to the original values P _B and T _B based on the number of times. If a brake operation is performed, hydraulic fluid is supplied from the power hydraulic pressure source device 14, and the pump motor 62 operates to recover the reduced pressure of the accumulator 64. Therefore, the number of brake operations is estimated based on the number of times the pump motor 62 is operated or the number of times the pump motor 62 is turned off from the ON state, and it is estimated whether or not the temperature of the hydraulic fluid has recovered. May be. Further, the number of brake operations may be estimated based on the number of times that the accumulator pressure detected by the accumulator pressure sensor 162 becomes a pressure that turns off the pump motor 62.

<Control program>
In the present hydraulic brake system, as described above, when it is detected that an abnormality that cannot be accumulated in the accumulator 64 has occurred, switching to the backup mode is performed so that the abnormality is not erroneously detected. In addition, the switching condition is changed. In this system, in order to determine whether or not to change the switching condition, after the vehicle is started and the brake ECU 150 is activated, the switching condition determination program shown in the flowchart of FIG. 7 is executed. Further, in this system, when there is no possibility of erroneous detection after the switching condition is changed, the switching condition return program shown in the flowchart of FIG. 8 is repeatedly executed to restore the changed threshold value. . Below, the flow of control processing by the switching condition determination program and the switching condition return program will be described with reference to the flowchart shown in the figure.

  It should be noted that the threshold value change flag FL that indicates whether or not the threshold value used for the switching condition has been changed is adopted in the processing by the two programs in the present hydraulic brake system. The flag value of the flag FL is set to 0 when the threshold value is not changed, and is set to 1 when the threshold value is changed.

i) Switching Condition Determination Program In the processing by the switching condition determination program shown in the flowchart of FIG. 7, first, after ECU 150 is started in step 1 (hereinafter simply referred to as “S1”, the same applies to other steps). In S2, it is determined whether or not the elapsed time since the pump motor 62 is turned on exceeds the set time T2. When those elapsed times do not exceed the set time, the process of determining whether or not the temperature of the hydraulic fluid after S3 is lower than the set temperature is performed. First, in S3 and S4, it is estimated whether or not the vehicle has not been started for a set time. Specifically, in S3, the accumulator pressure Pacc immediately after start of the vehicle is acquired, it is determined whether the accumulator pressure Pacc is in the atmospheric pressure P _0, the accumulator pressure Pacc becomes the atmospheric pressure P ₀ If it is, it is estimated that the vehicle has not been started for more than the set time. In S4, the accumulator pressure increasing gradient ΔP is calculated, and if the increasing gradient ΔP is larger than the set gradient ΔP0, it is estimated that the vehicle has not been started for a set time or more. When it is estimated that the vehicle has not been started for the set time or longer, it is estimated in S5 and S6 whether or not the outside air temperature while parked is lower than the set temperature. When it is estimated that the time when the vehicle has not been started is less than the set time, it is not necessary to change the switching condition. Therefore, in S7, the threshold hydraulic pressure is set to P _B and the threshold duration T _B.

Specifically, the estimation as to whether or not the outside temperature while parked was lower than the set temperature is first made in S5 based on whether or not the heating device 180 was used immediately before parking the vehicle. In step S6, whether or not the heating device 180 is currently used is determined. That is, when the heating device 180 is used immediately before parking the vehicle last time, or when the heating device 180 is currently used, it is estimated that the outside air temperature was lower than the set temperature. In that case, the switching condition is changed in S8, the threshold hydraulic pressure is set to P _B ′, the threshold duration is set to T _B ′, and the flag value of the threshold change flag FL is set to 1 in S9. When the switching condition is changed, the subsequent execution of this program is not performed at the end of the execution of the current program in S10. When it is estimated that the outside air temperature is not lower than the set air temperature, the switching condition is not changed, and the threshold hydraulic pressure is set to P _B and the threshold duration is set to T _B in S7. This completes one execution of the program.

Incidentally, in S3 and S4, when the elapsed time after the ECU 150 is started and the elapsed time after the pump motor 62 is turned on exceeds the set time, the switching condition is not changed and the threshold fluid pressure is changed. Let P _B be the threshold duration T _B. In this case, in S10, the subsequent execution of this program is not performed with the end of execution of the current program.

ii) Switching condition return program Next, in the processing by the switching condition return program shown in the flowchart of FIG. 8, first, in S21, the flag value of the threshold change flag FL is confirmed, and only when the flag value is 1, S2 The subsequent processing is executed. In S2 to S26, it is estimated whether or not the temperature of the hydraulic fluid has recovered to the set temperature. Specifically, first, in S22 and S23, the number of times of brake operation Na since the vehicle was started is estimated based on the amount of operation of the brake pedal 10 detected by the stroke sensor 160, and the number of times of brake operation. When Na exceeds the set number N ₀ , it is estimated that the temperature of the hydraulic fluid has recovered to the set temperature. Further, in S24 and S25, the number of times when the pressure at which the pump motor 62 is turned off is obtained from the detection result of the accumulator pressure sensor 162, and the number of brake operations Nb is estimated from the number of times. When the number of brake operations Nb exceeds the set number N ₀ , it is estimated that the temperature of the hydraulic fluid has recovered to the set temperature. Further, in S26, the number of times Nc to the pump motor 62 is operated is acquired, if the number of times Nc exceeds a set number N _1, the temperature of the hydraulic fluid is estimated to have recovered to a set temperature.

If it is estimated by any of the above determinations that the temperature of the hydraulic fluid has recovered to the set temperature, the changed switching condition is returned to the original in S27. That is, the threshold fluid pressure is P _B and the threshold duration is T _B. In S28, the flag value of the threshold change flag FL is set to 0. Thus, one execution of the switching condition return program is completed.

<Functional configuration of control device>
The brake ECU 150 that performs the above-described control and functions as a control device can be considered to have various functional units that perform the various processes described above. Specifically, as shown in FIG. 9, the brake ECU 150 realizes a first state in which the supply of hydraulic fluid from the power hydraulic pressure source device 14 to the brake cylinder 22 is permitted in a normal state, and the brake actuator 20 is A braking force control unit 200 that controls the braking force applied to the wheels 16 by controlling and adjusting the hydraulic pressure of the hydraulic fluid is provided. Further, the brake ECU 150 switches to the second state in which the supply of hydraulic fluid from the master cylinder 32 to the brake cylinder 22 is permitted when the state where the accumulator pressure is lower than the threshold fluid pressure continues for a threshold duration or longer during traveling. The realization state switching unit 202 is configured to generate a braking force according to the operation of the brake pedal 10.

  Furthermore, the brake ECU 150 estimates whether or not the hydraulic fluid is in a low fluid temperature state in which the temperature of the hydraulic fluid is lower than the set temperature, and the low fluid temperature state estimation unit 204. And a switching condition changing unit 206 that lowers the threshold liquid pressure used for the switching condition in the realization state switching unit 202 and lengthens the threshold duration when it is estimated that the liquid temperature state is low. . Furthermore, the brake ECU 150 estimates whether or not the temperature of the hydraulic fluid has recovered to the set temperature after the low fluid temperature state estimation unit 204 has estimated that the fluid temperature state is low. have. Note that when the liquid temperature recovery estimation unit 208 estimates that the temperature of the hydraulic fluid has recovered to the set temperature, the switching condition change unit 206 changes the changed threshold fluid pressure and threshold duration before the change. It is supposed to return to the value. Incidentally, the low liquid temperature state estimation unit 204 includes a part for executing S3 to S6 of the switching condition determination program, and the switching condition change unit 206 includes S8 of the switching condition determination program and the switching condition return program. The liquid temperature recovery estimation unit 208 is configured to include a part for executing S22 to S26 of the switching condition return program.

  10: Brake pedal 12: Manual hydraulic pressure source device 14: Power hydraulic pressure source device 16: Wheel 18: Hydraulic brake device 20: Brake actuator (hydraulic pressure adjusting device) 22: Brake cylinder 30: Hydraulic booster 32: Master cylinder 60: Pump 62: Pump motor 64: Accumulator 90: Output hydraulic pressure control valve device 92: Linear valve for pressure increase 94: Linear valve for pressure reduction 106: Solenoid 110: Individual hydraulic pressure adjustment device 112: Holding valve 114: Pressure reduction valve 120: Communication valve 130: Regulator cut valve 132: Master cut valve 134: Stroke simulator 136: Simulator cut valve 150: Brake electronic control unit (brake ECU, control device) 160: Stroke sensor 62: accumulator pressure sensor 180: Heating device 200: braking force control unit 202: realized state converter 204: low liquidus temperature state estimation unit 206: switching condition changing section 208: liquid temperature recovery estimator

Claims (5)

A brake operating member operated by a driver;
A brake device provided corresponding to the wheel, having a brake cylinder, and operating by a hydraulic pressure of hydraulic fluid supplied to the brake cylinder to apply a braking force to the wheel;
A master cylinder device that pressurizes the hydraulic fluid based on an operating force applied to the brake operating member;
A power-type hydraulic pressure source device that has a power source and pressurizes hydraulic fluid depending on the force generated by the power source;
A hydraulic pressure adjusting device for adjusting the hydraulic pressure of the hydraulic fluid generated by the power hydraulic pressure source device;
(a) A first state in which the supply of hydraulic fluid from the master cylinder device to the brake cylinder is shut off and the supply of hydraulic fluid from the power hydraulic pressure source device to the brake cylinder is allowed in a normal state. And controlling the hydraulic pressure adjusting device to adjust the hydraulic pressure of the hydraulic fluid, thereby controlling the braking force applied to the wheels, and (b) When the hydraulic pressure generated by the pressure source device is lower than the threshold hydraulic pressure for a threshold duration or longer, the supply of hydraulic fluid from the power hydraulic pressure source device to the brake cylinder is interrupted; and Switching to a second state in which the supply of hydraulic fluid from the master cylinder device to the brake cylinder is allowed, and a realization state switching unit for generating a braking force according to the operation of the brake operation member; and (c) the temperature of the hydraulic fluid is Set temperature A switching condition changing unit that performs at least one of lowering the threshold liquid pressure and increasing the threshold duration when it is estimated that the liquid temperature state is a lower state. A control device comprising:
Hydraulic brake system with The control device is
When starting the vehicle, it is estimated whether or not the vehicle has not been started for a set time or more, and whether or not the outside air temperature is lower than the set temperature, is estimated that the vehicle has not been started for the set time or more, and When it is estimated that the temperature is lower than the set temperature, the low liquid temperature state estimation unit that estimates that the low liquid temperature state is present,
The switching condition changing unit is
The liquid according to claim 1, configured to change at least one of the threshold liquid pressure and the threshold duration when the low liquid temperature state estimation unit estimates that the liquid is in the low liquid temperature state. Pressure brake system. The power hydraulic pressure source device is
It has an accumulator that stores hydraulic fluid in a pressurized state, and is controlled so that the pressure of the hydraulic fluid stored in the accumulator becomes a pressure within a pressure accumulation range that is a pressure within a set range.
The low liquid temperature state estimation unit,
The hydraulic brake system according to claim 2, wherein it is estimated whether or not the vehicle has not been started for a set time or more based on the pressure of the hydraulic fluid stored in the accumulator when the vehicle is started. The low liquid temperature state estimation unit,
The hydraulic brake system according to claim 2 or 3, wherein whether or not the outside air temperature is lower than a set air temperature is estimated based on a use state of a heating device mounted on the vehicle. The control device is
A liquid temperature recovery estimation unit that estimates whether or not the temperature of the hydraulic fluid has recovered to a set temperature after being estimated by the low liquid temperature state estimation unit to be in the low liquid temperature state;
The switching condition changing unit is
When the temperature of the hydraulic fluid is estimated to have recovered to a set temperature by the liquid temperature recovery estimation unit, at least one of the changed threshold fluid pressure and the threshold duration is returned to the value before the change. The hydraulic brake system according to any one of claims 2 to 4, wherein the hydraulic brake system is configured.

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