JPH11310119A - Brake device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To assist an uphill road starting by maintaining the brake force only in the condition in which the backward movement of the vehicle in the uphill road starting time cannot be prevented by a creep phenomenon, in the brake device for vehicle having the function to maintain the brake force. SOLUTION: A brake device for vehicle has a one-way valve 16 and a holding valve 22 provided between a master cylinder 10 and a wheel cylinder 18. When the holding valve 22 is made in a closing (ON) condition, the brake force is maintained. When it is discriminated that the vehicle is stopping, and the engine rotation frequency NE is less than a specific value, an ECU 26 makes the holding valve 22 in the closing condition, so as to maintain the brake force. When the running starting of the vehicle is detected, the holding of the brake force is released by making the holding valve 22 in the opening condition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brake system for a vehicle, and more particularly to a brake system having a function of assisting starting on a slope by maintaining a braking force.

[0002]

2. Description of the Related Art Conventionally, for example, Japanese Patent Application Laid-Open No. Hei 7-16506.
As disclosed in Japanese Patent Publication No. 3 (1993), a vehicle brake device is known. The brake device is mounted on a manual transmission (MT) vehicle, and includes a brake force holding unit that holds a brake force after the brake operation is released. The braking force holding means is activated when it is determined that the vehicle is stopped. According to the conventional brake device described above, the braking force is maintained even after the brake operation is released while the vehicle is stopped, so that the vehicle is prevented from retreating when starting on a slope.

[0003] The above-mentioned conventional brake device also has a clutch stroke sensor for detecting a stroke of a clutch pedal. When the stroke of the clutch pedal reaches a predetermined value, the braking force holding operation by the braking force holding means is released. Therefore, according to the conventional brake device described above, when the vehicle is started on the slope, the holding of the braking force is released when the clutch is in the half-clutch state, so that the vehicle can be started on the slope smoothly.

[0004]

In an automatic transmission (AT) vehicle, when the idling speed is maintained at a certain value or more,
Due to the creep phenomenon, the vehicle can be prevented from retreating when starting on a slope. However, from the viewpoint of improving fuel efficiency, it is required to suppress the idling speed of the engine. In this case, the creep force decreases due to a decrease in the idling rotational speed, and depending on the creep phenomenon, it may be difficult to prevent the vehicle from moving backward. Therefore,
A brake device mounted on an AT vehicle also needs a function of assisting starting on a sloping road like the above-described conventional brake device.

[0005] As described above, when the idling speed of the AT vehicle is high, the vehicle can be prevented from retreating at the time of starting on a sloping road due to the creep phenomenon, so that assistance for starting on the sloping road is unnecessary. On the other hand, the holding of the braking force after the release of the braking operation is a process for generating the braking force irrespective of the driver's intention, and therefore should be performed within a minimum necessary range. Therefore, it is desirable that the holding of the braking force in the AT vehicle is performed only in a situation where the vehicle cannot be prevented from retreating due to the creep phenomenon. However, the above-described conventional brake device is premised on mounting on an MT vehicle, and does not take into account operating the braking force holding means based on the engine speed. For this reason, the configuration of the above-mentioned conventional brake device is changed to A
When the present invention is applied to a T car, the braking force is maintained even in a situation where the idling speed is high and assistance for starting on a slope is unnecessary.

[0006] Further, the conventional brake device requires a stroke sensor for detecting a stroke of a clutch pedal in order to determine a timing for releasing the holding of the braking force. That is, extra parts are required for releasing the holding of the braking force, which leads to an increase in cost. The present invention has been made in view of the above points, and in an AT car,
It is a first object of the present invention to provide a vehicular brake device capable of holding a braking force and assisting starting on a sloping road only in a situation where retreat of the vehicle cannot be prevented due to a creep phenomenon.

It is a second object of the present invention to provide a vehicle brake device capable of determining the timing of releasing the holding of the braking force by a simple means in an MT vehicle.

[0008]

The above object is achieved by the present invention.
A vehicle braking device mounted on an automatic transmission vehicle and provided with braking force holding means for holding a braking force after a brake operation is released, the stopping state determining means for determining whether or not the vehicle is stopped And brake operation determining means for determining whether or not a brake operation is being performed, engine speed detecting means for detecting an engine speed, and when the vehicle is stopped and the brake operation is being performed. Holding operation means for operating the brake force holding means when the engine speed is equal to or lower than a predetermined value, travel start detection means for detecting the start of travel of the vehicle, and The present invention is attained by a vehicle brake device including: a holding release unit that releases an operation of a braking force holding unit.

In the present invention, the holding operation means is provided when the vehicle is stopped and the brake operation is being performed.
When the engine speed is equal to or lower than a predetermined value, the brake force holding means is operated. When the brake force holding means is operated, the brake force is held even after the brake operation is released. Therefore, when the vehicle starts moving, the braking force is held, so that the vehicle is prevented from moving backward when starting on a slope. The holding release unit releases the operation of the braking force holding unit when the start of traveling is detected. Therefore, it is possible to prevent the brake from being dragged after the start of traveling. By the way, as described above, when the engine speed is equal to or less than the predetermined value, the braking force holding means is operated, so that the vehicle cannot be prevented from moving backward due to the creep phenomenon of the AT vehicle. Retreat is prevented. Therefore, according to the present invention, it is possible to reliably prevent the vehicle from retreating when starting on a slope without increasing the engine speed. Also,
In a situation where the engine speed is high and the vehicle can be prevented from moving backward due to the creep phenomenon, the brake holding means holding operating means is not operated. Thus, according to the present invention,
Unnecessary holding of the braking force is prevented.

[0010] Another object of the present invention is to provide a brake system for a vehicle having a brake force holding means mounted on a manual transmission vehicle and holding a brake force after the brake operation is released. Stop state determining means for determining whether or not the vehicle is being stopped, brake operation determining means for determining whether or not the brake operation is being performed, and when the vehicle is stopped and the brake operation is being performed, Holding operation means for operating the braking force holding means, elapsed time measuring means for measuring an elapsed time after the brake operation is released, and operation of the braking force holding means when the elapsed time reaches a predetermined value This is achieved by a vehicle brake device comprising:

In the present invention, the holding operation means operates the braking force holding means when the vehicle is stopped and the brake operation is being performed. When the brake force holding means is operated, the brake force is held even after the brake operation is released. Therefore, when the vehicle starts moving, the braking force is held, so that the vehicle is prevented from moving backward when starting on a slope. Further, the holding release unit releases the operation of the braking force holding unit when the elapsed time after the brake operation is released reaches a predetermined value. Generally, when the vehicle starts running, the driver performs an accelerator operation following the release of the brake operation. Therefore, when a predetermined time has elapsed since the brake operation was released, it can be determined that the driver intends to start traveling. According to the present invention, in such a case, the holding of the braking force is released. That is, the timing for releasing the braking force is determined by a simple means that only measures the elapsed time.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a vehicle brake device (hereinafter simply referred to as a brake device) according to an embodiment of the present invention.
FIG. The brake device of the present embodiment is mounted on an AT car. As shown in FIG. 1, the brake device includes a master cylinder 10. A brake pedal 12 is connected to the master cylinder 10. A hydraulic pressure (hereinafter, referred to as master cylinder pressure PM _{/ C} ) is generated in master cylinder 10 in accordance with the depression force on brake pedal 12.
A brake pipe 14 communicates with the master cylinder 10. A wheel cylinder 18 provided for each wheel communicates with the brake pipe 14 via a one-way valve 16. The one-way valve 16 is connected to the master cylinder 10
It is configured to allow only the flow of fluid from the side to the wheel cylinder 18 side. The wheel cylinder 18 generates a braking force according to the internal pressure thereof (hereinafter, referred to as wheel cylinder pressure P _{W / C} ). FIG. 1 shows only the wheel cylinder 18 for one wheel.

The brake pipe 14 has a brake pipe 20
Are in communication. The brake pipe 20 communicates with each wheel cylinder 18 via a holding valve 22. The holding valve 22 is a two-position solenoid valve that is open in a normal state and is closed when an ON signal is supplied to an electromagnetic coil provided therein. The electromagnetic coil of the holding valve 22 is connected to the electronic control unit 26 via the changeover switch 24.
(Hereinafter, referred to as ECU 26). The changeover switch 24 is a two-position manual switch that takes one of a conduction (ON) state and a cutoff (OFF) state.

The ECU 26 includes an NE sensor 28 for detecting the engine speed NE and a vehicle speed sensor 3 for detecting the vehicle speed V.
0, an accelerator switch 32 for detecting whether the accelerator pedal is depressed, a brake switch 34 for detecting whether the brake pedal 12 is depressed, and a select lever sensor 36 for detecting the position of the select lever.

In the brake device of this embodiment, when the brake pedal 12 is depressed in a state where the holding valve 22 is opened (off), a master cylinder pressure P _{M / C} corresponding to the depression force is generated. . This master cylinder pressure P
_{The M / C} is supplied to the wheel cylinder 18 via the holding valve 22 and the one-way valve 16. Also, the brake pedal 12
Is released, the brake fluid is recovered from the wheel cylinder 18 to the master cylinder 10 via the holding valve 22, so that the wheel cylinder pressure P _{W / C} is reduced. Therefore, according to the brake device, a braking force corresponding to the depression force of the brake pedal 12 can be generated.

When the holding valve 22 is closed (ON) in a state where the brake pedal 12 is depressed (that is, when an ON signal is supplied from the ECU 26 to the electromagnetic coil of the holding valve 22), , Wheel cylinder 18
Of the brake fluid from the cylinder to the master cylinder 10 is blocked. In such a state, the brake pedal 12
Is released, the wheel cylinder pressure P _{W / C} is not reduced, so that the braking force is maintained. Hereinafter, the state in which the holding valve 22 is closed is referred to as a state of holding the braking force of the brake device. When the brake pedal 12 is further depressed in the braking force holding state, the master cylinder pressure PM _{/ C} is increased. Therefore, the boosted master cylinder pressure P _{M / C} is transmitted to the wheel cylinder 18 via the one-way valve 16 so that the wheel cylinder pressure P _{M / C} is increased.
_{W / C is} also boosted.

As described above, according to the brake force holding state, the brake force can be held after the depression of the brake pedal 12 is released, and when the brake pedal 12 is further depressed, the braking is performed according to the depressed amount. Power can be increased. When the holding valve 22 is opened (off) in the braking force holding state, the brake fluid is moved from the wheel cylinder 18 to the holding valve 2.
By being collected by the master cylinder 10 via the second cylinder 2, the holding of the braking force is released. According to the brake device of the present embodiment, the vehicle can be prevented from retreating by realizing the brake force holding state when starting on a slope.

In the case of an AT car, when the idling speed is maintained at a certain level or more, the vehicle can be prevented from moving backward on a hill due to a creep phenomenon. However, from the viewpoint of improving fuel efficiency, it is desirable to suppress the idle speed of the engine to be low. In this case, if the idling rotational speed is suppressed, it becomes impossible to sufficiently secure the creep force, and depending on the creep phenomenon, it may not be possible to prevent the vehicle from moving backward on a hill.

The brake device of the present embodiment realizes the above-described braking force holding state only when it is determined that the vehicle cannot be prevented from retreating on a hill due to creep phenomenon, thereby ensuring the vehicle's retreat. The feature is that it can be prevented. Such a function is realized by the ECU 26 executing a predetermined routine. Hereinafter, the contents of the routine executed by the ECU 26 in the present embodiment will be described. In the following description, it is assumed that the changeover switch 24 is set to the ON state.

FIG. 2 is a flowchart showing an example of a routine executed by the ECU 26 to realize the brake force holding state in this embodiment. FIG. 3 shows the ECU 2
6 is a flowchart showing an example of a routine executed to release a brake force holding state. The routine shown in FIGS. 2 and 3 is a periodic interruption routine started at predetermined time intervals. First, the routine shown in FIG. 2 will be described.

When the routine shown in FIG. 2 is started, first, the process of step 100 is executed. Step 10
When it is 0, it is determined whether or not the braking force holding state is realized. As a result, if the braking force holding state has been realized, the current routine ends without executing any processing. On the other hand, if the braking force holding state is not realized in step 100, the process of step 102 is executed next.

In step 102, the brake switch 3
4, it is determined whether or not the brake pedal 12 is depressed. As a result, if the brake pedal 12 is not depressed, no braking force to be held is generated, and it is determined that it is not necessary to realize the brake force holding state, and the current routine ends. You. On the other hand, if it is determined in step 102 that the brake pedal 12 has been depressed, the process of step 104 is performed.

In step 104, it is determined whether or not the vehicle speed V detected by the vehicle speed sensor 30 is less than a predetermined value α. Here, the predetermined value α is a threshold value that is set in consideration of a measurement error of the vehicle speed sensor 30 and the like when determining the stop state based on the vehicle speed V. In step 104, V
If <α is not satisfied, the vehicle has not stopped, and
It is determined that the braking force should not be maintained, and the current routine ends. On the other hand, in step 104, V
If <α holds, the process of step 106 is executed next.

In step 106, it is determined based on the output signal of the select lever sensor 36 whether or not the select lever of the vehicle is in the D range. As a result, if the select lever is not in the D range, it is determined that the driver does not intend to start traveling, and thus it is unnecessary to assist starting on a sloping road, and the current routine ends. On the other hand, if it is determined in step 106 that the select lever is in the D range, the process of step 108 is executed next.

In step 108, the accelerator switch 3
Based on the output signal of No. 2, it is determined whether or not the depression of the accelerator pedal has been released. As a result, if the depression of the accelerator pedal is not released, it is determined that the vehicle is not stopped. In this case, it is determined that it is not necessary to realize the braking force holding state, and the current routine ends. On the other hand, if the depression of the accelerator pedal is released in step 108, it is determined that the vehicle is in a stopped state, and the process of step 110 is executed next.

In step 110, it is determined whether or not the engine speed NE detected by the NE sensor 28 is equal to or less than a predetermined value N0. Here, the predetermined value N0 is set to be the lower limit value of the engine speed NE that can prevent the vehicle from moving backward on a slope due to creep phenomenon. Therefore, in step 110, NE ≦ N
If 0 is not established, it is determined that the idling rotational speed is increasing due to, for example, the operation of the air conditioner, and that the vehicle can be prevented from moving backward due to the creep phenomenon. In this case, it is determined that the holding of the braking force is unnecessary, and the current routine ends. On the other hand, if it is determined in step 110 that NE ≦ N0, it is determined that the vehicle cannot be prevented from retreating when starting on a slope due to the creep phenomenon. In this case, in step 112, the holding valve 22 is turned on (closed) to realize the brake force holding state, and then the current routine ends.

As described above, according to the routine shown in FIG. 2, it is determined in step 102 that the brake pedal 12 is depressed, it is determined in steps 104 and 108 that the vehicle is stopped, and in step 106, the driver is instructed. It is determined that there is an intention to start running, and in step 110, the engine speed NE is increased to a predetermined value N0.
The holding valve 22 is turned on only when it is determined that the condition is below. That is, the braking force holding state is realized only when it is determined that the vehicle may start on a slope and that the vehicle cannot be prevented from retreating due to the creep phenomenon. Therefore, according to the routine shown in FIG. 3, it is possible to prevent the vehicle from retreating when starting on a hill, without unnecessarily maintaining the braking force.

Next, referring to FIG. 3, the contents of a routine executed by the ECU 26 to release the brake force holding state will be described. When the routine shown in FIG. 3 is started, first,
Step 120 is executed. In step 120, it is determined whether the braking force holding state has been realized. As a result, if the braking force holding state has not been realized, the current routine ends without executing any processing. On the other hand, if it is determined in step 120 that the braking force holding state has been achieved, the process of step 122 is executed next.

In step 122, the brake pedal 12
The elapsed time T after the depression of the step is released is a predetermined time Td.
It is determined whether or not this is the case. Generally, when the vehicle starts running, the driver operates the accelerator pedal following the release of the brake operation. The above predetermined time Td
Is set to be a standard time from when the brake operation is released to when the accelerator operation is performed in such a case. Therefore, if T ≧ Td is satisfied in step 122, the depression of the accelerator pedal, that is, the start of running of the vehicle is predicted, and it is determined that it is not necessary to maintain the brake force holding state. In this case, in step 124, the holding valve 22 is turned off to release the brake force holding state. When the process of step 124 is completed, the current routine is completed. On the other hand, in step 122,
If T ≧ Td is not satisfied, the process of step 126 is executed next.

In step 126, it is determined whether or not the accelerator pedal is depressed. As a result, if the accelerator pedal is depressed, it is determined that the vehicle has started traveling, and then the brake force holding state is released in step 124, and then the current routine is terminated. On the other hand, if the accelerator pedal is not depressed in step 126, the process of step 128 is executed next.

At step 128, the engine speed NE
Is greater than a predetermined value N1. Here, the predetermined value N1 is a threshold value for determining whether or not the vehicle is running based on the engine speed NE. Therefore, if NE> N1 is satisfied, it is determined that the vehicle has started running, for example, on a downhill road without depressing the accelerator pedal. In this case, it is determined that the brake force holding state should not be maintained. Next, after the brake force holding state is released in step 124, the current routine is terminated. On the other hand, in step 128, NE> N
If 1 is not established, the current routine ends without releasing the brake force holding state.

As described above, according to the routine shown in FIG. 3, after the depression of the brake pedal 12 is released, the braking force holding state is released at the timing when it is determined that the vehicle has started running. Therefore, according to the brake device of the present embodiment, it is possible to prevent the brake from being dragged after the start of traveling. Further, as described above, according to the processing of step 122 of the routine shown in FIG. 3, the brake force holding state is unconditionally released when a predetermined time Td has elapsed since the brake operation was released. Therefore, for example, on a flat road or a downhill road, the brake force holding state is maintained even when the vehicle is started due to the creep phenomenon without the accelerator pedal being depressed and without increasing the engine speed NE. It can be surely released.

As the predetermined time Td, for example, the time from the release of the brake operation to the depression of the accelerator pedal for various drivers is investigated, and a typical value thereof can be used. Further, the driver may manually set Td, or may learn and store the driving operation of the driver and automatically adjust the value of Td to be an optimum value for each driver. Is also good.

As described above, according to this embodiment, when the engine speed NE is equal to or lower than the predetermined value while the vehicle is stopped, the brake force holding state is realized, so that the vehicle is started on a slope without increasing the idling speed. It is possible to reliably prevent the vehicle from moving backward. Therefore, according to the brake device of the present embodiment, it is possible to smoothly start on a hill regardless of the skill of the driver while improving the fuel efficiency by suppressing the idling rotation speed.

Further, according to the present embodiment, the braking force holding state is realized only when the engine speed NE is equal to or lower than the predetermined value. Force retention is performed. Therefore, according to the brake device of the present embodiment, it is possible to assist starting on a sloping road without holding the braking force unnecessarily.

Further, according to the present embodiment, the vehicle is prevented from retreating when starting on a slope by holding the braking force.
The driver is prevented from idling the engine to prevent the vehicle from moving backward. According to the brake device of this embodiment, the effect of improving fuel efficiency can be obtained in this sense as well. In the brake device according to the present embodiment, when the changeover switch 24 is turned off, the ECU
Even if 26 outputs an ON signal to the holding valve 22, the braking force holding state is not realized. Therefore, a driver who does not want to perform the slope start assisting operation by holding the braking force can switch the switch 24 to the off state to prohibit the realization of the braking force holding state.

In the above-described embodiment, the holding valve 22 is provided, and the holding valve 22 is closed (on) to maintain the braking force. However, for example, a brake device having an anti-lock brake (ABS) function is provided with a hydraulic actuator for holding a braking force. Therefore, in such a brake device, the present invention is applied without separately providing a holding valve. Can be.

In the above embodiment, the holding valve 22 is connected to the braking force holding means described in the claims.
8 corresponds to the engine speed detecting means described in the claims, and the ECU 26 executes the processing of steps 104 and 108 of the routine shown in FIG. By executing the processing, the above-described brake operation determining means
By executing the processing of steps 110 and 112, the above-described holding operation means executes the processing of steps 122, 126, or 128 of the routine shown in FIG.
By executing the processing of the above, the holding release means described above,
Each has been realized.

Incidentally, in the above embodiment, the present invention is applied to the AT
The case where the present invention is applied to a car has been described.
It can also be applied to cars. Since the creep phenomenon does not occur in the MT vehicle, it is not necessary to determine whether to maintain the braking force based on the level of the engine speed NE. Therefore, in the MT vehicle, the routine shown in FIG. 2 is executed in a form in which step 110 is omitted, and the routine shown in FIG.
The following routine may be executed. As described above, according to the routine shown in FIG. 3, the timing for releasing the holding of the braking force can be determined only by measuring the elapsed time after the release of the brake operation. Accordingly, the timing at which the holding of the braking force is released without performing any special means such as detecting the stroke of the clutch pedal, for example, by executing the processing of step 122 of the routine shown in FIG. Can be easily determined. In this case, the ECU 26
Executes the processing of step 122 of the routine shown in FIG.

[0040]

As described above, according to the first aspect of the present invention, in an AT car, the braking force can be maintained only in a situation where the vehicle cannot be prevented from moving backward on a hill due to a creep phenomenon. . Therefore, according to the present invention, it is possible to prevent the vehicle from retreating when starting on a slope while suppressing unnecessary holding of the braking force.

According to the second aspect of the present invention, the MT
In a vehicle, the release timing of the holding of the braking force can be determined by a simple means only by measuring the elapsed time after the release of the brake operation.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a vehicle brake device according to an embodiment of the present invention.

FIG. 2 is a flowchart of an example of a routine executed by the ECU to realize a brake force holding state in the embodiment.

FIG. 3 is a flowchart illustrating an example of a routine that is executed by the ECU to cancel a brake force holding state in the embodiment.

[Explanation of symbols]

 22 Holding valve 26 ECU 28 NE sensor

Claims (2)

[Claims] 1. A vehicle braking device mounted on an automatic transmission vehicle and provided with braking force retaining means for retaining a braking force after a brake operation is released, wherein a stationary state determining means for determining whether or not the vehicle is stopped. And brake operation determining means for determining whether or not a brake operation is being performed, engine speed detecting means for detecting an engine speed, and when the vehicle is stopped and the brake operation is being performed. Holding operation means for operating the braking force holding means when the engine speed is equal to or lower than a predetermined value; driving start detecting means for detecting the start of running of the vehicle; A vehicle brake device comprising: a holding release unit that releases the operation of the braking force holding unit. 2. A vehicle braking device mounted on a manual transmission vehicle and provided with braking force retaining means for retaining a braking force after a brake operation is released, wherein a stationary state determining means for determining whether or not the vehicle is stopped. Brake operation determining means for determining whether or not a brake operation is being performed; holding operation means for activating the brake force holding means when the vehicle is stopped and a brake operation is being performed; An elapsed time measuring unit that measures an elapsed time after the brake operation is released, and a holding release unit that releases the operation of the braking force holding unit when the elapsed time reaches a predetermined value. Vehicle braking device.