JP2000264182A - Braking force control device and vehicle control device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To run a vehicle at a microspeed without operating an accelerator pedal by inhibiting or suspending the execution of braking force holding control when a driver operates an operation switch. SOLUTION: In the case where a vehicle is requested to hold braking force, an electronic brake control unit 10 puts holding valves 40, 44 in on state (valve closed state). In this state, when an operation switch 56 is turned on, the processing of putting the holding valves 40, 44 in the off state (valve opening state) for releasing the braking force holding state is executed, so that a master cylinder 27 and wheel cylinders 52, 54 become continuity state. In this case, a brake fluid of the wheel cylinders 52, 54 flows out to the master cylinder 27 side, so that the braking force is decreased by lowering of wheel cylinder pressure. By this method, the held braking force can be decreased without accelerator operation. Thus, a vehicle is enabled to advance at microspeed by utilizing gravity on a down-hill or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a braking force control device, and more particularly to a braking force control device having a function of retaining a braking force, and a control device for a vehicle including the device.

[0002]

2. Description of the Related Art Conventionally, for example, Japanese Patent Application Laid-Open No. Hei 9-18823.
As disclosed in No. 3, a braking force control device that holds a braking force generated in a vehicle under a predetermined situation is known. This braking force control device includes an electromagnetic valve that switches a conduction state between a master cylinder and a wheel cylinder. A drive signal is supplied to such an electromagnetic valve when a predetermined condition is satisfied. In this case, the cutoff state is established between the master cylinder and the wheel cylinder, and the wheel cylinder maintains the wheel cylinder pressure immediately before the cutoff state. Therefore, according to the above-described conventional braking force control device, even when the brake operation is released, the braking force generated in the vehicle when the predetermined condition is satisfied can be maintained. Hereinafter, this control is referred to as braking force holding control.

[0003] In the above-mentioned conventional device, when the depression of the accelerator pedal exceeds a predetermined amount, the supply of the drive signal to the solenoid valve is stopped. In this case, conduction is established between the master cylinder and the wheel cylinder, the brake fluid in the wheel cylinder flows out to the master cylinder side, and the wheel cylinder pressure decreases. Therefore, according to the above-described conventional braking force control device, the holding state of the braking force generated in the vehicle can be released based on the depression amount of the accelerator pedal.

[0004]

When a driver wants to move a stopped vehicle forward at a very low speed by utilizing creep force, gravity on a downhill, or the like during a traffic jam or the like. There is. In this case, it is necessary to reduce the braking force generated in the vehicle. In a vehicle equipped with the above-described conventional device, in order to reduce the braking force in a state where the braking force is held, it is necessary to depress the accelerator pedal to release the holding state of the braking force. However, when the accelerator pedal is depressed to reduce the braking force, the braking force decreases and the driving force increases, so that the vehicle may accelerate rapidly. For this reason, it is not easy for the above-mentioned conventional device to advance the vehicle, in which the braking force is maintained, at a very small speed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and allows a vehicle to run at a very low speed by prohibiting or stopping execution of braking force holding control without operating an accelerator pedal. It is an object of the present invention to provide a braking force control device capable of performing the control.

[0006]

The above object is achieved by the present invention.
In the braking force control device capable of executing the braking force holding control for holding the braking force when a predetermined condition is satisfied, an operation switch operable by the driver and a case where the operation switch is operated And a holding control prohibiting means for prohibiting or suspending the execution of the braking force holding control.

In the present invention, when the operation switch is operated by the driver, the execution of the braking force holding control is prohibited or stopped. In this case, the holding of the braking force is released or prohibited by the driver's intention, so that the vehicle can run at a very small speed by utilizing the creep force, the gravity on the downhill, and the like. According to a second aspect of the present invention, there is provided a braking force control device capable of executing a braking force holding control for holding a braking force when a predetermined condition is satisfied, wherein the shift lever is operated to a neutral range. And a holding control prohibiting unit for prohibiting or stopping the execution of the braking force holding control.

In the present invention, when the driver operates the shift lever in the neutral range, the execution of the braking force holding control is prohibited or stopped. When the shift lever is operated to the neutral range, it can be determined that the driver intends to coast the vehicle. in this case,
The vehicle can be effectively moved forward and backward.
Therefore, according to the present invention, when the shift lever is operated in the neutral range, the holding of the braking force is released or prohibited, so that the vehicle travels at a very low speed by utilizing gravity or the like on a downhill. It becomes possible.

[0009] The object of the present invention is as described in claim 3.
In a braking force control device capable of executing a braking force holding control for holding a braking force when a predetermined condition is satisfied, a downhill determination unit that determines whether or not the traveling road is downhill, This is achieved by a braking force control device comprising: a holding control prohibiting unit that prohibits the execution of the braking force holding control when it is determined that the vehicle is on a slope.

In the present invention, when it is determined that the traveling road on which the vehicle travels is downhill, the execution of the braking force holding control is prohibited. Therefore, the braking force is not maintained on the downhill, and the vehicle can be advanced at a very low speed by using gravity. According to a fourth aspect of the present invention, there is provided a braking force control apparatus according to the third aspect, further comprising: a tilt sensor that detects a degree of forward tilt of the vehicle body; and a vehicle speed sensor that detects a vehicle speed.
The above-described downhill determination means is achieved by a braking force control device, which determines whether or not a traveling road is on a downhill based on an output signal of the inclination sensor and an output signal of the vehicle speed sensor. .

In the present invention, whether or not the traveling path on which the vehicle travels is downhill is determined based on the forward inclination of the vehicle body and the vehicle speed. The output signal of the tilt sensor indicates a signal in which the vehicle body tilts forward when the traveling road is downhill and when the vehicle is decelerating. When the vehicle is decelerating, the vehicle speed exceeds “0”, and by detecting the forward inclination of the vehicle body in the state where the vehicle speed is “0”, the case where the traveling road is downhill is determined. It is possible to distinguish between a case where the vehicle decelerates and a case where the vehicle decelerates. For this reason, according to the present invention, it is possible to accurately determine the downhill of the traveling road. In the present invention, when it is determined that the traveling path on which the vehicle travels is downhill, the execution of the braking force holding control is prohibited. If the execution of the braking force holding control is prohibited when the traveling road is on a downhill, the holding of the braking force is not performed, and the vehicle can move forward at a very low speed on the downhill.

[0012] The object of the present invention is as described in claim 5.
In a braking force control device capable of executing a braking force holding control for holding a braking force when a predetermined condition is satisfied, an operation amount detecting means for detecting a brake operation amount, and a situation in which the braking force holding control is executed The braking force control device includes: a braking force reducing unit configured to reduce a held braking force by an amount corresponding to a change amount of the brake operation amount.

In the present invention, a brake operation amount is detected. The braking force reducing means is configured to convert the held braking force into an amount corresponding to a change amount of the brake operation amount to the depressed release side, that is, the amount corresponding to the decrease amount of the brake operation amount, in a state where the braking force holding control is being executed. Only decrease. That is, the braking force reducing means gradually reduces the held braking force as the amount of reduction in the amount of brake operation is smaller, and decreases the held braking force more rapidly as the amount of reduction in the amount of brake operation is larger. When the braking force is reduced in accordance with the brake operation amount, the holding state of the braking force is released while reflecting the driver's intention. Thus, according to the present invention,
The vehicle can run at low speed while generating a braking force according to the driver's intention.

Further, as described in claim 6, claim 1 is
A braking force control device according to any one of claims 1 to 5, and an engine stop control device that executes an engine stop control that stops the internal combustion engine while the vehicle is stopped. A brake booster for applying an assist force corresponding to the supplied negative pressure to the master cylinder, a negative pressure detecting means for detecting the negative pressure, and the negative pressure during operation of the holding control prohibiting means or the braking force reducing means. A control unit for prohibiting or canceling the execution of the engine stop control when the value of the control value becomes smaller than a predetermined value. This is effective in maintaining the vehicle in a state where a large braking force can be generated even when the control for stopping or executing the control for decreasing the held braking force is performed.

[0015] In the present invention, the brake booster applies an assist force to the master cylinder according to the negative pressure from the internal combustion engine. A braking force holding control for holding the braking force when a predetermined condition is satisfied, and a control for inhibiting or stopping the execution of the braking force holding control in a predetermined case (hereinafter, referred to as holding inhibition control), or Then, control for reducing the held braking force (hereinafter, referred to as braking force reduction control) is executed. Further, engine stop control for stopping the operation of the internal combustion engine while the vehicle is stopped is executed. If the holding prohibition control or the braking force reduction control is being performed while the engine stop control is being performed, that is, if a state in which a braking force can be generated by the braking operation is formed, the brake operation is performed. Is performed, a situation may occur in which the negative pressure from the internal combustion engine decreases. When this happens,
Since the assist force applied to the master cylinder is small, a large braking force cannot be secured.

In the present invention, the execution of the engine stop control is prohibited or stopped when the negative pressure from the internal combustion engine is reduced to a predetermined value or less while the holding inhibition control or the braking force reduction control is being executed. You. That is, the operating state of the internal combustion engine continues, or the internal combustion engine switches from the stopped state to the operating state. When the internal combustion engine is in operation,
The reduction of the negative pressure is prevented, and a large braking force can be secured. Therefore, according to the present invention, the vehicle can be maintained in a state where a large braking force can be generated when the holding prohibition control or the braking force reduction control is being executed.

[0017]

FIG. 1 is a system configuration diagram of a braking force control device and an engine control device mounted on a vehicle according to a first embodiment of the present invention. The braking force control device according to the present embodiment includes a brake electronic control unit (hereinafter, referred to as a brake ECU).
The brake ECU 10 controls the wheel cylinder pressure of the wheels under the control of the brake ECU 10. Further, the engine control device of the present embodiment includes an engine electronic control unit (hereinafter, referred to as an engine ECU) 11, and controls the operating state of the internal combustion engine under the control of the engine ECU 11. Specifically, the engine ECU 11
Executes engine stop control for stopping the operation of the internal combustion engine when the vehicle is stopped due to traffic congestion or a signal waiting at an intersection. FIG. 1 shows only a portion corresponding to the left front wheel FL and the right rear wheel RR in the braking force control device of the present embodiment.

The braking force control device of this embodiment includes a brake pedal 12. A brake switch 14 is provided near the brake pedal 12. The brake switch 14 maintains the off state when the depression of the brake pedal 12 is released, and the brake pedal 1
When the brake pedal is depressed, the ON signal is sent to the brake ECU.
Output to 10 The brake ECU 10 determines whether the brake pedal 12 is depressed based on the output signal of the brake switch 14.

A brake booster 18 is connected to the brake pedal 12 via an operation shaft 16. Operating shaft 1
6 is provided with a stroke sensor 20. The stroke sensor 20 outputs a signal corresponding to the pedal stroke S of the brake pedal 12 to the brake ECU 10. The brake ECU 10 includes a stroke sensor 20
The pedal stroke S is detected on the basis of the output signal.

The brake booster 18 is provided with the diaphragm 2
1 is divided into a negative pressure chamber 22 and an atmospheric pressure chamber 23. The intake manifold 25 of the internal combustion engine 24 communicates with the negative pressure chamber 22. The internal combustion engine 24 is an engine ECU
The operation state is controlled based on a signal from the engine ECU 11. Engine ECU 11
When a predetermined condition such as that the brake pedal 12 is depressed while the vehicle is stopped is satisfied, the internal combustion engine 2
4 is supplied with a command signal so as to stop.
When a request to start the internal combustion engine 24 is issued,
Supplies a command signal so as to be in an operating state. When the internal combustion engine 24 enters the operating state, intake negative pressure is generated in the intake manifold 25, and the negative pressure is guided to the negative pressure chamber 22. During operation of the internal combustion engine 24, the brake booster 18 generates an assist force having a predetermined boosting ratio with respect to the brake depression force when the brake pedal 12 is depressed.

In the passage between the intake manifold 25 and the negative pressure chamber 22, a negative pressure sensor 26 is provided. The negative pressure sensor 26 outputs a signal corresponding to the internal pressure of the passage, that is, a negative pressure guided to the negative pressure chamber 22 to the brake ECU 10. The brake ECU 10 detects the negative pressure VAC in the negative pressure chamber 22 based on the output signal of the negative pressure sensor 26.

A master cylinder 27 is connected to the brake booster 18. The master cylinder 27 includes a first hydraulic chamber 28 and a second hydraulic chamber 30 therein. In the first hydraulic pressure chamber 28 and the second hydraulic pressure chamber 30, a master cylinder pressure is generated according to the resultant force of the brake depression force and the assist force. Above the master cylinder 27, a reservoir tank 32 is provided. The master cylinder 27 and the reservoir tank 32 enter a conductive state when the depression of the brake pedal 12 is released, and enter a disconnected state when the brake pedal 12 is depressed. First
A first hydraulic passage 34 communicates with the hydraulic chamber 28, and a second hydraulic passage 36 communicates with the second hydraulic chamber 30. The first hydraulic passage 34 forms a first hydraulic circuit that communicates with the front left wheel FL and the rear right wheel RR. In addition, the second hydraulic passage 36
Constitutes a second hydraulic circuit communicating with the front right wheel FR and the rear left wheel RL. Since the first hydraulic circuit and the second hydraulic circuit are substantially the same in configuration, the configuration and operation of the first hydraulic circuit will be described below.

A master cylinder pressure sensor 38 is provided in the first hydraulic pressure passage 34. The master cylinder pressure sensor 38 outputs a signal corresponding to the internal pressure of the first hydraulic pressure passage 34, that is, a master cylinder pressure generated by the master cylinder 27, to the brake ECU 10. Brake ECU
Reference numeral 10 detects the master cylinder pressure Pmc based on the output signal of the master cylinder pressure sensor 38.

A control hydraulic pressure passage 42 communicates with the first hydraulic pressure passage 34 via a holding valve 40 and a holding valve 44
A control hydraulic pressure passage 46 communicates with the control hydraulic pressure passage 46. Holding valve 4
0,44 maintain the valve open state in the normal state, and the brake ECU
The solenoid valve is a two-position solenoid valve that is closed when a drive signal is supplied from the solenoid valve 10. Check valves 48 and 50 are arranged in parallel with the holding valves 40 and 44. Check valve 48,5
0 is the control hydraulic pressure passages 42 and 46 from the first hydraulic pressure passage 34 side.
This is a one-way valve that allows only the flow of brake fluid toward the side.

The wheel cylinder 52 of the left front wheel FL communicates with the control hydraulic pressure passage 42. Also, the control hydraulic pressure passage 4
The wheel cylinder 54 of the right rear wheel RR communicates with 6. The wheel cylinders 52, 54 are connected to the control hydraulic passages 42,
The braking force according to the hydraulic pressure supplied from the wheel FL, R
Assigned to R. The brake ECU 10 is connected to an operation switch 56 that is disposed on a console in the vehicle and that can be operated by a driver. The operation switch 56 maintains an off state in a normal state, and outputs an on signal to the brake ECU 10 when operated by a driver. The brake ECU 10 determines whether or not the operation switch 56 is on based on the output signal of the operation switch 56.

A vehicle speed sensor 58 and a gradient sensor 60 are connected to the brake ECU 10. The vehicle speed sensor 58 outputs a signal corresponding to the speed of the vehicle to the brake ECU.
Output to 10 Further, the gradient sensor 60 outputs a signal corresponding to the degree of inclination of the vehicle to the brake ECU 10. The brake ECU 10 determines the vehicle speed SPD based on the output signals of the vehicle speed sensor 58 and the gradient sensor 60.
And the vehicle inclination K are detected.

Next, the operation of the braking force control device of this embodiment will be described. In this embodiment, the brake ECU 1
0 indicates that the holding valves 40 and 44 are in an off state (valve closed state) in a normal state. In this case, in the braking force control device, FIG.
The state shown in FIG. In the situation shown in FIG. 1, the wheel cylinders 52, 54 communicate with the master cylinder 27, so that a wheel cylinder pressure equal to the master cylinder pressure is guided to the wheel cylinders 52, 54. Therefore, according to the braking force control device of the present embodiment, it is possible to generate the braking force according to the brake operation amount in the normal state.

When the vehicle is stopped, there may be a case where a request for maintaining the wheel cylinder pressure to maintain the braking force generated on the vehicle occurs. When such a request occurs, the brake ECU 10
Turns on the holding valves 40 and 44 (valve open state).
When such a state is realized, the wheel cylinders 52, 54
Is shut off from the master cylinder 27. In this case, the wheel cylinder pressure is maintained at the pressure immediately before the wheel cylinders 52 and 54 are disconnected from the master cylinder 27.
Therefore, according to the braking force control device of the present embodiment, when the predetermined condition is satisfied, the braking force generated in the vehicle can be maintained even if the depression of the brake pedal 12 is subsequently released. Hereinafter, this control is referred to as braking force holding control.

By the way, when the vehicle is in a traffic jam or the like, the driver
There is a case where it is desired to move a stopped vehicle at a very small speed by using creep force or gravity on a downhill. Such a request
If this occurs in a state where the braking force holding control is being executed, it is necessary to release the holding of the braking force promptly. The braking force control device according to the present embodiment has a first feature in that the holding of the braking force is released without the driver depressing the accelerator pedal. Hereinafter, the characteristic portions will be described.

FIG. 2 shows a flowchart of an example of a control routine executed by the brake ECU 10 in the braking force control device of this embodiment to release the holding of the braking force. The routine shown in FIG. 2 is a periodic interruption routine that is repeatedly driven every predetermined time. When the routine shown in FIG. 2 is started, first, the process of step 100 is executed.

In step 100, it is determined whether or not the braking force is being maintained, that is, whether or not the holding valves 40 and 44 have been on (closed state) for a predetermined time. As a result, if it is determined that the ON state of the holding valves 40 and 44 continues for a predetermined time, the process of step 102 is executed next. On the other hand, if it is determined that the ON state of the holding valves 40 and 44 does not continue for the predetermined time, the current routine ends without any processing being performed.

In step 102, it is determined whether or not the operation switch 56 is on based on the output signal of the operation switch 56. As a result, if it is determined that the operation switch 56 is in the ON state, the process proceeds to step 10.
4 is executed. On the other hand, if it is determined that the operation switch 56 is not on, the current routine ends.

In step 104, a process for releasing the holding state of the braking force, specifically, a process for turning off the holding valves 40 and 44 (opened state) is executed. This step 1
When the process in step 04 is executed, the master cylinder 27 and the wheel cylinders 52 and 54 are brought into conduction. in this case,
The brake fluid of the wheel cylinders 52 and 54 flows out to the master cylinder 27 side, and the braking force decreases due to a decrease in the wheel cylinder pressure. When the process of step 104 is completed, the current routine is completed.

According to the above processing, when the operation switch 56 is turned on while the braking force is held, the held state can be released, that is, the braking force can be reduced. According to such a method, it is not necessary to operate the accelerator pedal to reduce the held braking force. Therefore, according to the braking force control device of the present embodiment, the held braking force can be reduced according to the driver's intention without performing the accelerator operation. This allows the vehicle to:
It becomes possible to move forward at a very small speed by utilizing creep force and gravity on a downhill.

In the present embodiment, as described above, the engine ECU 11 executes the engine stop control for stopping the operation of the internal combustion engine 24 when the vehicle is stopped due to traffic congestion or signal waiting at an intersection. When such engine stop control is performed, the internal combustion engine 24 is stopped,
The negative pressure is no longer supplied from the intake manifold 25 to the negative pressure chamber 22 of the brake booster 18. If the brake operation is frequently performed in a state where the negative pressure is not supplied, the internal pressure of the negative pressure chamber 22 approaches the atmospheric pressure, and the assist force applied from the brake booster 18 to the master cylinder 27 decreases.

In this embodiment, when the holding state of the braking force is released, the vehicle can move forward at a very small speed by utilizing the creep force and the gravity on the downhill. In this case, a braking force corresponding to the driver's braking operation may be generated in the vehicle. When the engine stop control is executed and the brake operation is performed in a state where the vehicle can move forward at a very small speed as described above, the negative pressure in the negative pressure chamber 22 is consumed, so that the master from the brake booster 18 is released. The assist force applied to the cylinder 27 decreases. When the assist force is small, it is difficult to increase the wheel cylinder pressure to a large pressure, and there is a possibility that a large braking force cannot be secured.

In order to solve such a problem, the system of this embodiment prohibits execution of the engine stop control when the negative pressure VAC approaches the atmospheric pressure, thereby reducing the negative pressure in the negative pressure chamber 22 to a large pressure. It has a second feature in that it is maintained. Hereinafter, the characteristic portions will be described. FIG. 3 shows a flowchart of an example of a control routine executed by the brake ECU 10 in the braking force control device of the present embodiment to inhibit the execution of the engine stop control. The routine shown in FIG. 3 is a periodic interruption routine that is repeatedly started at predetermined time intervals. When the routine shown in FIG. 3 is started, first, the process of step 110 is executed.

In step 110, it is determined whether the negative pressure sensor 26 or the vehicle speed sensor 58 is in an abnormal state. If the sensor is abnormal, it is not possible to accurately detect a parameter for executing the engine stop control, and it is not appropriate to execute the engine stop control. Therefore, when it is determined that an abnormality has occurred in the sensor, the process of step 118 is executed next. On the other hand, if it is determined that no abnormality has occurred in the sensor, the process of step 112 is performed next.

In step 112, the negative pressure VAC and the vehicle speed SPD are detected based on the output signal of the sensor. In step 114, it is determined whether or not the absolute value of the negative pressure VAC detected in step 112 is equal to or greater than a predetermined value VAC0. The predetermined value VAC0 is a minimum pressure at which an assist force having a predetermined boosting ratio with respect to the brake depression force can be generated. When | VAC | ≧ VAC0 holds, it can be determined that a large negative pressure is generated in the negative pressure chamber 22 of the brake booster 18. In this case, the wheel cylinder pressure can be quickly increased, and the internal combustion engine 24
There is no inconvenience even if is stopped. Therefore, if it is determined that | VAC | ≧ VAC0 holds as a result of the above processing, the processing of step 116 is executed next.

On the other hand, when it is determined that | VAC | ≧ VAC0 is not established, it can be determined that a negative pressure is not generated in the negative pressure chamber 22 so large that the wheel cylinder pressure can be quickly increased. In this case, it is appropriate to bring the internal combustion engine 24 into an operating state. Therefore, when such a determination is made, the process of step 118 is executed next. In step 116, the vehicle speed S detected in step 112 is determined.
It is determined whether the PD is equal to or greater than a predetermined value SPD0.
The predetermined value SPD0 is a limit speed at which it can be determined that the vehicle is quickly stopped within a predetermined range while the internal combustion engine 24 is stopped. If SPD ≧ SPD0 does not hold as a result of the above processing, it can be determined that the vehicle is traveling at a speed small enough to stop quickly. In this case, the internal combustion engine 2
No inconvenience occurs even if 4 is stopped. Therefore,
If it is determined that SPD ≧ SPD0 does not hold, the current routine is terminated.

On the other hand, if SPD ≧ SPD0 holds, it can be determined that the vehicle is traveling at a somewhat high speed. In order to stop the vehicle in a situation where the vehicle runs at high speed, it is necessary to generate a large braking force on the vehicle. However, when the operation of the internal combustion engine 24 is stopped, a large negative pressure is not supplied to the negative pressure chamber 22 of the brake booster 18, so that a large braking force may not be secured. Therefore, it is appropriate to bring the internal combustion engine 24 into the operating state when the above condition is satisfied. Therefore, when it is determined that SPD ≧ SPD0 holds,
Next, the process of step 118 is executed.

In step 118, the engine ECU 11
In response, a signal for inhibiting execution of engine stop control for internal combustion engine 24 is output. This step 118
Is executed, the execution of the engine stop control in the engine ECU 11 is prohibited thereafter. This step 11
When the process of step 8 is completed, the current routine is completed.
According to the above processing, when the negative pressure VAC has decreased,
Further, when the vehicle speed SPD is high, a signal prohibiting execution of the engine stop control for the internal combustion engine 24 is output to the engine E.
It can be output to CU11.

FIG. 4 is a flowchart showing an example of a control routine executed by the engine ECU 11 in the engine control device according to the present embodiment. The routine shown in FIG. 4 is a periodic interrupt routine that is repeatedly started at predetermined time intervals. When the routine shown in FIG. 4 is started, first, the process of step 122 is executed. In step 122, it is determined whether a predetermined condition for executing the engine stop control is satisfied. As a result, if it is determined that the above condition is satisfied, then the process of step 124 is executed. On the other hand, if the above condition is not satisfied, the internal combustion engine 2
It is not necessary to stop the operation of the internal combustion engine 4, and it is necessary to continue the operation of the internal combustion engine 24 or to start the stopped internal combustion engine 24. Therefore, if such a determination is made, then step 124 is jumped to execute step 126.

In step 124, the brake ECU 10
Thus, it is determined whether a signal requesting prohibition of execution of the engine stop control for the internal combustion engine 24 has been received. As a result, if such a signal is received, then step 1
26 is executed. On the other hand, if the above signal has not been received, the process of step 128 is performed next.

In step 126, a process for operating the internal combustion engine 24 is executed. When the process of step 126 is executed, the operation of the internal combustion engine 24 continues thereafter, or the stopped internal combustion engine 24 starts.
In this case, air is sucked toward the internal combustion engine 24, and a large negative pressure is guided to the negative pressure chamber 22 of the brake booster 18. When the process of step 126 ends, the current routine ends.

In step 128, a process for stopping the operation of the internal combustion engine 24 is executed. After the process of step 128 is performed, the air is no longer sucked into the internal combustion engine 24. When the process of step 128 ends, the current routine ends. According to the above processing, even when the execution condition of the engine stop control is satisfied, the execution of the engine stop control is prohibited when the signal for prohibiting the execution of the engine stop control is received from the brake ECU 10. Can be. When the execution of the engine stop control is prohibited, the internal combustion engine 24 switches from the stop state to the operation state or continues the operation state. For this reason, according to the present embodiment, it is possible to prevent a decrease in the negative pressure generated in the negative pressure chamber 22 of the brake booster 18, and it is possible to secure a large braking force. Therefore, according to the present embodiment,
When the control for reducing the held braking force is executed, the vehicle can be maintained in a state where a large braking force can be generated.

In the above embodiment, the brake E
The CU 10 executes the processing of the step 104, and the “holding control prohibiting means” according to claim 1 detects the negative pressure VAC based on the output signal of the negative pressure sensor 26. The "negative pressure detecting means" is realized, and the "engine stop control prohibiting means" is realized by the engine ECU 11 executing the process of step 126.

In the above-described embodiment, when the operation switch 56 is operated by the driver, the holding state of the braking force is released. However, the present invention is not limited to this. A shift position sensor that outputs a signal corresponding to the position of the shift lever of the transmission to the brake ECU 10 is provided. Based on the output signal, it is determined whether the shift lever is operated in the neutral range. When it is determined that the operation has been performed in the neutral range, the holding state of the braking force may be released. In this case, the brake ECU 1
By executing the process of step 104 based on the result of the determination, the "holding control prohibiting means" is realized.

In the above embodiment, when the operation switch 56 is operated, the holding state of the braking force is released for the vehicle on which the braking force holding control has been executed.
Although the traveling of the vehicle is enabled, the present invention is not limited to this. When the operation switch 56 is operated, the vehicle can be driven by prohibiting the execution of the braking force holding control. You may do it.

Next, a braking force control device according to a second embodiment of the present invention will be described with reference to FIG. 5 together with FIG.
The system of the present embodiment is realized by causing the brake ECU 10 to execute the routine shown in FIG. 5 in the braking force control device shown in FIG. In the above-described first embodiment, when the predetermined condition is satisfied under the condition that the braking force holding control is being executed, the holding of the braking force is released, so that the vehicle can advance at a very small speed. I have. In contrast, the system of the present embodiment prohibits the execution of the braking force holding control when the vehicle is on a downhill,
The feature is that the vehicle can advance at a very small speed.

FIG. 5 shows a flowchart of an example of a control routine executed by the brake ECU 10 in the braking force control device of the present embodiment to realize the above functions. FIG.
Is a regular interruption routine that is repeatedly started at predetermined time intervals. When the routine shown in FIG. 5 is started, first, the process of step 130 is executed.

In step 130, the vehicle speed SPD and the vehicle inclination K are detected based on the output signals of the vehicle speed sensor 58 and the gradient sensor 60. In step 132, it is determined whether or not the traveling path on which the vehicle travels is downhill. In the present embodiment, the determination of the downhill of the traveling path is
The determination is performed based on the vehicle speed SPD and the vehicle inclination degree K. The vehicle inclination degree K is calculated as follows:
Also, when the vehicle decelerates, the value of the downward slope is obtained. When the vehicle decelerates, the vehicle speed SPD exceeds "0". Therefore, it is determined whether or not the vehicle speed SPD is "0". Can be distinguished. Therefore, the vehicle speed SPD
Is "0", and a value of the downslope appears in the vehicle inclination degree K, it can be determined that the traveling road on which the vehicle travels is downhill.

If it is determined in step 132 that the traveling road is downhill, the process in step 134 is executed. On the other hand, if it is determined that the traveling path is not a downhill, the process of step 136 is executed next. In step 134, processing for inhibiting the execution of the braking force holding control, that is, processing for inhibiting the holding valves 40 and 44 from being turned on (closed state) is executed. When the process of step 134 is executed, the wheel cylinder pressure is not maintained thereafter, and the wheel cylinders 52 and 54 may generate the wheel cylinder pressure corresponding to the brake depression force. When the process of step 134 ends, the current routine ends.

In step 136, a process for permitting the execution of the braking force holding control, that is, a process for allowing the holding valves 40 and 44 to be opened and closed according to the conditions for establishing the braking force holding control, is executed. When the process of step 136 ends, the current routine ends. According to the above processing, when the traveling path on which the vehicle travels is a downhill, the braking force holding control can be prohibited. If the braking force holding control is prohibited in such a case, the braking force will not be held except for the brake operation, and the wheel cylinders 52, 5
4, a wheel cylinder pressure corresponding to the brake operation can be generated. Therefore, according to the braking force control device of the present embodiment,
When the traveling path is a downhill, the vehicle can be advanced at a very small speed by utilizing the gravity of the vehicle on the downhill.

In the above embodiment, the brake E
The CU 10 executes the process of the step 132 based on the output signal of the vehicle speed sensor 58 and the output signal of the gradient sensor 60, so that the “downhill determining means” executes the process of the step 134. Thereby, the "holding control prohibiting means" of claim 3 is realized respectively.

In the above-described embodiment, the determination of the downhill of the traveling road is made based on the vehicle speed SPD and the vehicle inclination K, but the method of determining the downhill of the traveling road is not limited to this. Instead, the difference between the vehicle height at the front wheels and the vehicle height at the rear wheels may be considered, or the determination may be made based on the information on the traveling path on which the vehicle is currently traveling from the GPS navigation. .

Next, a braking force control device according to a third embodiment of the present invention will be described with reference to FIG. The system of the present embodiment is realized by using a linear valve instead of the holding valves 40 and 44 in the braking force control device shown in FIG. 1 and causing the brake ECU 10 to execute a routine shown in FIG. In the present embodiment, the linear valve maintains the valve open state in a normal state, closes when a drive signal is supplied from the brake ECU 10, and in the valve closed state, the hydraulic pressure in the control hydraulic pressure passage 42 is reduced to the first hydraulic pressure. This is a control valve that opens when the pressure is higher than a predetermined relief pressure as compared with the hydraulic pressure in the pressure passage 34. The linear valve changes the relief pressure linearly according to a drive signal from the brake ECU 10. Specifically, the linear valve has a larger relief pressure as the drive signal is larger, and has a smaller relief pressure as the drive signal is smaller.

During execution of the braking force holding control, a constant braking force is generated in the vehicle regardless of the brake operation. In this embodiment, when the brake pedal 12 is depressed and the depression is released, the relief pressure of the linear valve is changed in accordance with the change amount of the pedal stroke S to the depressed side. When the relief pressure changes,
Accordingly, the amount of brake fluid flowing from wheel cylinders 52, 54 to the master cylinder increases or decreases. In this case, the wheel cylinder pressure generated in the wheel cylinders 52 and 54 changes, and the braking force generated in the vehicle changes. In the system of the present embodiment, in the process of releasing the state from the state in which the braking force holding control is being executed, the relief pressure of the linear valve is changed in accordance with the amount of change in the pedal stroke S of the brake pedal 12 to the side where the depression is released. Is characterized in that the amount of decrease in the braking force is changed by changing.

FIG. 6 shows a flowchart of an example of a control routine executed by the brake ECU 10 in the braking force control device of the present embodiment to realize the above functions. FIG.
Is a periodic interruption routine that is repeatedly driven at predetermined time intervals. When the routine shown in FIG. 6 is started, first, the process of step 140 is executed.

In step 140, it is determined whether or not the braking force holding control is being executed, that is, whether or not the on-state (closed state) of the linear valve has continued for a predetermined time. As a result, when it is determined that the above condition is satisfied, the process of step 142 is executed next. On the other hand, if it is determined that the above condition is not satisfied, the current routine ends without any processing being performed.

In step 142, the stroke sensor 2
Based on the output signal of 0, the pedal stroke S of the brake pedal 12 is detected. In step 144, a change amount ΔS of the pedal stroke S from the previous processing cycle to the current processing cycle is calculated. Step 1
At step 46, a process is executed to set the drive signal IH supplied to the linear valve to a value obtained by subtracting an amount I (ΔS) corresponding to the pedal stroke change amount ΔS from the drive signal IH in the previous processing cycle. .

At step 148, processing for outputting the calculated drive signal IH to the linear valve is executed.
When the processing of step 148 is executed, according to the above processing, the pedal stroke S of the brake pedal 12 is
The drive signal IH to the linear valve can be reduced according to the amount of change ΔS to the release side of the depression.

In this embodiment, the brake pedal 12
As the amount of change .DELTA.S toward the stepping release side becomes larger, the amount of decrease in the drive signal IH to the linear valve becomes larger and the relief pressure becomes extremely small. For this reason, as the change amount ΔS is larger, the brakes from the wheel cylinders 52 and 54 toward the master cylinder 27 until the pressure difference between the hydraulic pressure on the wheel cylinders 52 and 54 and the hydraulic pressure on the master cylinder 27 side becomes smaller. Fluid can escape. That is, the larger the change amount ΔS is, the larger the amount of brake fluid flowing from the wheel cylinders 52 and 54 toward the master cylinder 27 is.

Therefore, when the change amount ΔS is large, the pressure reduction amount of the wheel cylinder pressure is large, and the held braking force decreases quickly. On the other hand, when the change amount ΔS is small, the wheel cylinder pressure reduction amount is The small, held braking force decreases slowly. As described above, according to the present embodiment, in the process of releasing the state from the state where the braking force holding control is being executed, by changing the relief pressure,
The amount by which the braking force is reduced can be changed. Therefore, according to the present embodiment, the driver does not operate the accelerator pedal and releases the holding state of the braking force while changing the reduction amount of the braking force according to the change amount of the pedal stroke S of the brake pedal 12. be able to. As a result, the vehicle equipped with the braking force control device of the present embodiment can move forward at a very small speed by using the creep force and the gravity on the downhill while adjusting the braking force.

In the above embodiment, the brake E
The CU 10 detects the pedal stroke S of the brake pedal 12 based on the output signal of the stroke sensor 20, and the “operation amount detection means” according to claim 5 executes the processing of step 146. The described "braking force reducing means" is realized respectively.

In the first to third embodiments, the brake fluid is guided to the wheel cylinders 52 and 54 to generate a braking force. However, the present invention is not limited to this. The present invention is also applicable to a device that generates a braking force by supplying a drive signal to an electric motor. Next, a braking force control device according to a fourth embodiment of the present invention will be described with reference to FIG. The system of the present embodiment is realized by the brake ECU 10 executing the routine shown in FIG. 7 instead of the routine shown in FIG. 6 in the braking force control device of the third embodiment.

When the pedal stroke S changes, the master cylinder pressure Pmc changes accordingly. Therefore, in the system according to the present embodiment, the above-described relief pressure is changed according to the reduced amount of the master cylinder pressure Pmc. FIG. 7 shows a flowchart of an example of a control routine executed by the brake ECU 10 in the braking force control device of the present embodiment to realize the above functions. The routine shown in FIG. 7 is a periodic interruption routine that is repeatedly started at predetermined time intervals. In FIG. 7, steps that execute the same processing as the steps shown in FIG. 6 are denoted by the same reference numerals, and description thereof is omitted. That is, in the routine shown in FIG. 7, after it is determined in step 140 that the braking force holding control is being executed, the process of step 150 is executed.

In step 150, the master cylinder pressure Pmc is determined based on the output signal of the master cylinder pressure sensor 38.
Is detected. In step 152, the change amount ΔPmc of the master cylinder pressure Pmc from the previous processing cycle to the current processing cycle is calculated. In step 154, the drive signal IH supplied to the linear valve is set to a value obtained by subtracting an amount I (ΔPmc) corresponding to the change amount ΔPmc of the master cylinder pressure from the drive signal IH in the previous processing cycle. Be executed. When the processing of step 154 is completed, the routine of this time is terminated after step 148 is executed.

According to the above processing, the master cylinder pressure P
The drive signal IH to the linear valve according to the decrease amount ΔPmc of mc
Can be reduced. In the present embodiment, as the decrease amount ΔPmc of the master cylinder pressure Pmc increases, the decrease amount of the drive signal IH to the linear valve increases, and the relief pressure becomes extremely small. For this reason, according to the present embodiment, similarly to the case of the third embodiment, in the process of releasing the state from the state in which the braking force holding control is being executed, by changing the relief pressure, The amount by which the braking force is reduced can be changed. Therefore, according to the present embodiment, it is possible to release the holding state of the braking force while changing the amount of decrease in the braking force according to the amount of change in the master cylinder pressure Pmc without the driver operating the accelerator pedal. . as a result,
The vehicle equipped with the braking force control device of the present embodiment can move forward at a very small speed by using the creep force and the gravity on the downhill while adjusting the braking force.

In the above embodiment, the brake E
The CU (10) detects the master cylinder pressure (Pmc) based on the output signal of the master cylinder pressure sensor (38).
The "braking force reducing means" according to the fifth aspect is realized by executing the processing of the fourth aspect.

[0071]

As described above, according to the first aspect of the present invention, when the driver operates the operation switch without depressing the accelerator pedal, the execution of the braking force holding control is prohibited or stopped. Thus, the vehicle can run at a very low speed. According to the invention described in claim 2,
When the driver operates the shift lever to the neutral range without depressing the accelerator pedal, the execution of the braking force holding control is prohibited or stopped, so that the vehicle can run at a very low speed.

According to the third aspect of the present invention, when the traveling path on which the vehicle travels is downhill, the execution of the braking force holding control is prohibited, so that the vehicle can move forward at a very small speed. Becomes According to the invention described in claim 4, it is possible to accurately determine whether or not the traveling path on which the vehicle travels is a downhill.

According to the fifth aspect of the present invention, since the amount of decrease in the braking force changes in accordance with the amount of brake operation, the holding state of the braking force can be released while reflecting the driver's intention. This allows the vehicle to run at a low speed while generating a braking force according to the driver's intention without depressing the accelerator pedal. According to the invention described in claim 6, when the control for prohibiting or stopping the execution of the braking force holding control or the control for reducing the held braking force is executed, the vehicle is forced to exert a large braking force. It can be maintained in a state where it can occur.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram of a braking force control device and an engine control device mounted on a vehicle according to a first embodiment of the present invention.

FIG. 2 is a flowchart illustrating an example of a control routine that is executed to cancel a holding state of a braking force in the embodiment.

FIG. 3 is a flowchart of an example of a control routine executed to start an internal combustion engine in the braking force control device according to the embodiment.

FIG. 4 is a flowchart of an example of a control routine executed to start the internal combustion engine in the engine control device of the embodiment.

FIG. 5 is a flowchart of an example of a control routine executed in a braking force control device according to a second embodiment of the present invention.

FIG. 6 is a flowchart of an example of a control routine executed in a braking force control device according to a third embodiment of the present invention.

FIG. 7 is a flowchart of an example of a control routine executed in a braking force control device according to a fourth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Brake electronic control unit (brake ECU) 11 Engine electronic control unit (engine ECU) 12 Brake pedal 18 Brake booster 20 Stroke sensor 24 Internal combustion engine 26 Negative pressure sensor 27 Master cylinder 38 Master cylinder pressure sensor 52, 54 Wheel cylinder 58 Vehicle speed sensor 60 gradient sensor

Claims (6)

[Claims] 1. A braking force control device capable of executing a braking force holding control for holding a braking force when a predetermined condition is satisfied, comprising: an operation switch operable by a driver; and when the operation switch is operated. And a holding control prohibiting means for prohibiting or stopping the execution of the braking force holding control. 2. A braking force control device capable of executing a braking force holding control for holding a braking force when a predetermined condition is satisfied, wherein the braking force holding control is performed when a shift lever is operated to a neutral range. A braking force control device comprising: a holding control prohibiting unit that prohibits or cancels execution. 3. A braking force control device capable of executing a braking force holding control for holding a braking force when a predetermined condition is satisfied, comprising: a downhill discriminating means for discriminating whether or not a traveling road is a downhill. And a holding control prohibiting means for prohibiting the execution of the braking force holding control when it is determined that the traveling road is downhill. 4. The braking force control device according to claim 3, further comprising: an inclination sensor for detecting a degree of forward inclination of the vehicle body; and a vehicle speed sensor for detecting a vehicle speed; A braking force control device that determines whether or not a traveling road is downhill based on an output signal of a sensor and an output signal of the vehicle speed sensor. 5. A braking force control device capable of executing a braking force holding control for holding a braking force when a predetermined condition is satisfied, wherein: an operation amount detecting means for detecting a brake operation amount; A braking force control device comprising: a braking force reduction unit configured to reduce a held braking force by an amount corresponding to a change amount of the brake operation amount in a situation where the braking operation is being performed. 6. A vehicle comprising: a braking force control device according to claim 1; and an engine stop control device that executes an engine stop control for stopping an internal combustion engine while the vehicle is stopped. In the control device, a brake booster that applies an assist force corresponding to a negative pressure supplied from the internal combustion engine to a master cylinder; a negative pressure detecting unit that detects the negative pressure; a holding control prohibiting unit or the braking force decrease A control device for a vehicle, comprising: engine stop control prohibiting means for prohibiting or stopping the execution of the engine stop control when the negative pressure falls below a predetermined value during operation of the means.