JP2000272485A - Brake fluid pressure holding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a brake hydraulic pressure holding device releasing the action of the brake hydraulic pressure in a wheel cylinder when a driver has the intention of a going downhill. SOLUTION: In a brake hydraulic pressure holding device RU for exerting the brake hydraulic pressure in a wheel cylinder WC continuously, until a departure drive force is generated in a vehicle itself, after the pedaling release of a brake pedal BP, even when the departure drive force is not generated, when a vehicular speed is increased upto a prescribed speed, the action of the brake hydraulic pressure in the wheel cylinder WC by the brake hydraulic pressure holding device RU is released.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle which, even after a brake pedal is depressed and released, until the vehicle itself generates a starting drive force.
The present invention relates to a brake fluid pressure holding device for continuously applying brake fluid pressure in a wheel cylinder.

[0002]

2. Description of the Related Art There is known a brake fluid pressure holding device capable of applying a brake fluid pressure in a wheel cylinder until a start driving force is generated in a vehicle itself even after a brake pedal is released. With this brake fluid pressure holding device, the vehicle can easily start smoothly without backing off when starting uphill.

For example, Japanese Patent Laying-Open No. 9-202159 discloses a braking force control device using a traction control system. This braking force control device operates until the driving force detecting means detects that the driving force has been switched from a small state to a large state (ie,
Until a starting driving force is generated), a constant braking force can be maintained under the control of the traction control system. Therefore, the vehicle does not move backward on an uphill. In addition, Japanese Patent Application No. Hei.
Japanese Patent Application No. 0-370249 describes a brake fluid pressure holding device using a brake fluid pressure reduction speed reducing means.
This brake fluid pressure holding device reduces the brake fluid pressure in the wheel cylinder by decreasing the brake fluid pressure in the wheel cylinder relative to the decreasing speed of the driver's depressing force of the brake pedal until the starting drive force is generated in the vehicle itself. The force is gradually reduced to maintain the braking force. Therefore, on an uphill, the vehicle does not move backward,
On a downhill, the vehicle can also be started simply by releasing or partially releasing the brake pedal.

[0004]

However, even in a vehicle equipped with the above-described brake fluid pressure holding device, when the slope is steep, the moving force in the direction of going down the slope is maintained by the propulsive force of the vehicle's own weight. It may exceed the braking force you are doing. Therefore, before the starting drive force is generated in the vehicle itself, that is, when the brake pedal is released or partially released, the vehicle
There is a case where the vehicle moves backward on an uphill and starts to descend on a downhill. At this time, if the driver intends to stop or climb the hill, when the vehicle starts to lean, the driver immediately depresses the brake pedal to increase the brake fluid pressure in the wheel cylinder, or depresses the accelerator pedal. In this way, a starting drive force is generated to prevent the vehicle from moving backward. On the other hand, if the driver intends to go downhill, even if the vehicle begins to go down, the driver will tolerate that condition. Note that “downhill” means that the vehicle goes downhill. In particular, when the driver intends to go downhill, the driver may travel downhill while adjusting the depression force of the brake pedal. In this case, the holding of the braking force by the brake fluid pressure holding device is an unnecessary braking force for traveling downhill. Therefore, if the driver intends to go downhill, it is better to release the holding of the braking force by the brake fluid pressure holding device and generate a braking force in accordance with the driver's operation of the brake pedal. It can be performed.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a brake fluid pressure holding device for releasing the action of brake fluid pressure in a wheel cylinder when a driver intends to go downhill.

[0006]

The brake fluid pressure holding device according to the present invention, which has solved the above-mentioned problems, continues to maintain the brake fluid pressure in the wheel cylinder even after the brake pedal is released and released until the vehicle itself generates a starting drive force. In a brake fluid pressure holding device that applies pressure, even when no starting drive force is generated, when the vehicle speed increases to a predetermined vehicle speed, the brake fluid pressure in the wheel cylinder is released from the action of the brake fluid pressure in the wheel cylinder. It is characterized by doing. According to this brake fluid pressure holding device, when the vehicle speed increases to a level at which the driver can determine that the driver intends to go downhill, the action of the brake fluid pressure in the wheel cylinder is released even when no starting drive force is generated. I do. After the release, the brake fluid pressure in the wheel cylinder becomes a brake fluid pressure according to the depression force of the brake pedal of the driver.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a brake fluid pressure holding device according to the present invention will be described below with reference to the drawings. 1 is a configuration diagram of a brake fluid pressure holding device, FIG. 2 is a system configuration diagram of a vehicle including the brake fluid pressure holding device, FIG. 3 is a control logic of the brake fluid pressure holding device when the vehicle stops, and FIG. Control logic to close the solenoid valve,
4B is a control logic for automatically stopping the engine, FIG. 4 is a control logic when the vehicle is started by the brake fluid pressure holding device, FIG. 4A is a control logic for opening the solenoid valve, and FIG. FIG. 5 is a control time chart of a vehicle equipped with a brake fluid pressure holding device. FIG. 5A shows a change in driving force and braking force in a time sequence of deceleration → stop → start of the vehicle. FIG. 6B is a configuration diagram of a brake hydraulic circuit when the vehicle is stopped, and FIG. 6 is a diagram illustrating a case where no starting drive force is generated when the vehicle starts and the vehicle speed increases to a predetermined vehicle speed. FIG. 7 is a control time chart corresponding to FIG. 5, and FIG. 7 is a control time chart corresponding to FIG. 6 when the engine is not automatically stopped when the vehicle stops.

[0008] The brake fluid pressure holding device of the present invention includes a brake device that is operated by hydraulic pressure (brake fluid pressure).
In addition, the present invention can be applied to all vehicles equipped with a motor. The prime mover includes an engine that is an internal combustion engine that uses gasoline or the like as a power source, a Stirling engine that is an external combustion engine, a motor that uses electricity as a power source, and the like. Vehicles include a manual transmission vehicle equipped with a manual transmission (hereinafter referred to as an MT vehicle) and an automatic transmission vehicle equipped with an automatic transmission (hereinafter referred to as an AT vehicle). The brake fluid pressure holding device of the present invention can be applied.

<< Structure of Brake Fluid Pressure Holding Device >> The brake fluid pressure holding device of the present invention continues to hold the brake fluid pressure in the wheel cylinder even after the brake pedal is released and released until the vehicle itself generates a starting drive force. It is a device to do.
Means for holding the brake fluid pressure include brake fluid pressure decreasing speed decreasing means for decreasing the decreasing speed of the brake fluid pressure in the wheel cylinder with respect to the decreasing speed of the stepping force of the driver's brake pedal, Using a traction control system to maintain a constant brake fluid pressure in the wheel cylinder
The means is not particularly limited. Further, the brake fluid pressure holding device of the present invention has a function of releasing the holding of the brake fluid pressure in the wheel cylinder when the vehicle speed increases to a predetermined vehicle speed even when no starting driving force is generated.

[0010] The term "until the starting driving force is generated in the vehicle itself" means that the output from the prime mover such as an engine or a motor is transmitted to the driving wheels, and the vehicle does not drop on a slope without a braking force. It is until it becomes. In order to detect this state, the drive torque of the drive wheels may be directly measured. However, generally, it is determined that the starting drive force has occurred in the vehicle itself at the following time. In the case of an MT vehicle, the determination is made when the accelerator pedal is depressed by the driver's operation and the clutch is connected. In the case of an AT car, the determination is made when the accelerator pedal is depressed by the driver's operation. Also, in the case of an AT car in which the torque transmission capacity of the starting clutch is increased such that the driving force is automatically increased to a level that automatically resists the slope in response to the release of the brake pedal, the starting clutch The determination is made when the torque transmission capacity is increased.

The "predetermined vehicle speed" is a vehicle speed at which the driver can determine that the driver intends to go downhill. In the present embodiment, the predetermined vehicle speed is set to 20 km / h. However, if the vehicle speed is set too low, the brake fluid pressure acting by the brake fluid pressure holding device can be reduced only when the vehicle slightly moves backward when starting uphill. May be canceled. Therefore, it is desirable to set the speed to about 10 km / h or more.

Referring to FIG. 1, the brake hydraulic pressure holding device of the present invention will be described together with a hydraulic brake device.
The brake fluid pressure holding device RU is a hydraulic brake device BK.
And the brake fluid pressure in the wheel cylinder WC is held by the brake fluid pressure reduction speed reducing means.

[Hydraulic Brake Apparatus] First, the hydraulic brake apparatus BK will be described. The brake hydraulic circuit BC of the hydraulic brake device BK includes a master cylinder MC, a wheel cylinder WC, and a brake fluid pipe FP connecting the master cylinder MC and the wheel cylinder WC. Since the brake plays a very important role for safe driving, the hydraulic brake device BK is provided with two independent brake hydraulic circuits (BC (A), BC
(B)) Even if one system fails, a minimum braking force can be obtained in the remaining systems.

The master cylinder MC has a piston M
The CP is inserted and the driver
, The piston MCP is pushed, and pressure is applied to the brake fluid in the master cylinder MC to convert mechanical force into brake fluid pressure (pressure applied to the brake fluid).
When the driver releases his / her foot from the brake pedal BP to release the depression, the master cylinder MC returns the piston MCP by the force of the return spring MCS, and at the same time, also returns the brake fluid pressure to the original. The master cylinder MC shown in FIG. 1 is a tandem-type master cylinder in which two pistons MCP are arranged and the main body is divided into two parts from the viewpoint of fail-safe in which two independent brake hydraulic circuits BC are provided.

Further, in order to reduce the operating force of the brake pedal BP, the brake pedal BP and the master cylinder M
Between C, a master power MP (brake booster) is provided. The master power MP shown in FIG. 1 is of a vacuum (negative pressure) servo type, and takes out a negative pressure from an intake manifold (not shown) of the engine to facilitate the driver's operation of the brake pedal BP.

The brake fluid pipe FP is connected to the master cylinder M
C and wheel cylinder WC, and master cylinder MC
Plays a role of a flow path for transmitting the brake fluid pressure generated by the brake fluid to the wheel cylinder WC by moving the brake fluid. When the brake fluid pressure of the wheel cylinder WC is higher, it functions as a flow path for returning the brake fluid from the wheel cylinder WC to the master cylinder MC. As described above, independent brake fluid circuits BC are provided, and two independent brake fluid pipes FP are provided. In the brake hydraulic circuit BC constituted by the brake fluid pipe FP shown in FIG. 1, one brake hydraulic circuit BC (A) brakes the right front wheel and the left rear wheel, and the other brake hydraulic circuit BC (B ) Is of the X-pipe type that brakes the left front wheel and the right rear wheel. Note that the brake hydraulic circuit may be of a front-rear split type in which one brake hydraulic circuit brakes both front wheels and the other brake hydraulic circuit brakes both rear wheels, instead of the X piping system.

The wheel cylinder WC is provided for each wheel, and applies a brake fluid pressure generated by the master cylinder MC and transmitted to the wheel cylinder WC through the brake fluid pipe FP to a mechanical force (braking force) for braking the wheel. ). The wheel cylinder WC is
A piston is inserted into a main body (not shown), and the piston is pushed by the brake fluid pressure to actuate a brake pad in the case of a disc brake or a brake shoe in the case of a drum brake to brake the wheels. Create braking force. In addition to the above, the brake fluid pressure of the front wheel cylinder WC and the rear wheel cylinder WC
A brake fluid pressure control valve for controlling the brake fluid pressure is provided as necessary.

[Brake hydraulic pressure holding device] Next, the brake hydraulic pressure holding device RU will be described. Brake fluid pressure holding device R
U is the driver's brake pedal B when the vehicle starts.
Wheel cylinder WC against the decreasing speed of the stepping force of P
And a brake fluid pressure decreasing speed reducing means for decreasing the decreasing speed of the brake fluid pressure. The brake fluid pressure decreasing speed decreasing means determines the speed at which the brake fluid pressure of the wheel cylinder WC decreases (the speed at which the braking force decreases) when the driver releases the brake pedal BP when the vehicle restarts. Has a function of lowering the speed at which the depression force of the brake pedal BP is reduced.

The means for reducing the brake fluid pressure decreasing speed having such a function can be constituted by providing a portion in the brake fluid pressure circuit BC which becomes a fluid resistance to the flow of the brake fluid. In addition, besides the brake hydraulic circuit BC, for example, the movement of the brake pedal BP itself is regulated so that even if the driver quickly releases the depression of the brake pedal BP, the brake pedal BP is gradually returned to its original position. Can also be configured. In the former case, the flow of the brake fluid itself is regulated. In the latter case, the movement of the brake pedal BP itself is restricted. In any case, it is possible to reduce the rate of decrease of the brake fluid pressure in the wheel cylinder WC with respect to the rate of decrease of the driver's depression force on the brake pedal BP.

The brake fluid pressure holding device RU shown in FIG. 1 has a brake fluid pressure reduction speed reducing means provided in a brake fluid pressure circuit BC of a hydraulic brake device BK. The brake fluid pressure holding device RU includes a solenoid valve SV and a throttle D in the brake fluid pressure circuit BC and, if necessary, a check valve CV and a relief valve RV in order to regulate the flow of the brake fluid itself.
Is provided. In the brake fluid pressure holding device RU, the solenoid valve SV and the throttle D constitute a brake fluid pressure decreasing speed reducing means.

The solenoid valve SV is connected to the ECU 6 (CVT ECU).
6: will be described later in detail), and in the closed state, shuts off the flow of the brake fluid in the brake fluid pipe FP and serves to maintain the brake fluid pressure applied to the wheel cylinder WC. . By the way, two solenoid valves S
V (A) and SV (B) indicate that they are both open. By the solenoid valve SV, even when the driver releases the depression of the brake pedal BP when starting up a hill, the brake fluid pressure is held in the wheel cylinder WC, and the vehicle can be prevented from moving backward. Note that "backward movement" means that the vehicle travels in a direction opposite to the direction in which the driver intends to travel due to the own weight (potential energy) of the vehicle (downslope).

As the solenoid valve SV, there are a normally closed type which is opened when energized and a normally open type which is closed when energized, and any of the solenoid valves SV can be used. However, from the viewpoint of fail-and-safe, a normally open solenoid valve SV
Is preferred. This is because when the power supply is cut off due to a failure or the like, the normally closed solenoid valve SV does not operate the brake, or conversely, the brake remains effective. Therefore, in the present embodiment, a normally open solenoid valve SV is used. In normal operation,
The solenoid valve SV is closed from the time the vehicle stops to the time when the vehicle starts moving, but under what conditions the solenoid valve SV will be closed or open will be determined later. This will be described in detail. Also, the brake fluid pressure holding device RU
To release the action of the brake fluid pressure in the wheel cylinder WC by opening the solenoid valve SV and conducting between the wheel cylinder WC and the master cylinder MC, and the brake fluid pressure in the wheel cylinder WC is reduced by the driver's brake pedal BP. The brake fluid pressure according to the stepping force of the brake pedal.

The throttle D conducts between the master cylinder MC and the wheel cylinder WC regardless of the open / close state of the solenoid valve SV. In particular, when the solenoid valve SV is closed and the driver releases or depresses the brake pedal BP, the throttle D gradually releases the brake fluid trapped in the wheel cylinder WC toward the master cylinder MC. To reduce the brake fluid pressure of the wheel cylinder WC at a predetermined speed. The throttle D can be configured by providing a flow rate adjusting valve in the brake fluid pipe FP, or a portion of the brake fluid pipe FP that becomes a resistance to fluid (a portion where the cross-sectional area of the flow passage is reduced). ) May be provided.

If the driver releases or loosens the brake pedal BP due to the presence of the throttle D, even if the solenoid valve SV is in the closed state, there is no state in which the brake is permanently applied, and the braking force ( Braking force) decreases. That is, the rate of decrease in the brake fluid pressure in the wheel cylinder WC can be made smaller than the rate of decrease in the depression force of the driver's brake pedal BP. Thus, even after the solenoid valve SV is closed, the braking force is sufficiently reduced after a predetermined time, and the vehicle can be restarted (uphill) by the driving force of the prime mover. Also, on a downhill, the vehicle can be started only by the vehicle's own weight without the driver depressing the accelerator pedal.

Note that, as long as the brake fluid pressure of the master cylinder MC is higher than the brake fluid pressure of the wheel cylinder WC while the driver is depressing the brake pedal BP, the braking force does not decrease due to the presence of the throttle D. . This is because the throttle D has a function of flowing the brake fluid at a predetermined speed from a higher brake fluid pressure to a lower brake fluid pressure by a difference (differential pressure) between the brake fluid pressures of the wheel cylinder WC and the master cylinder MC. That is, as long as the driver does not loosen the depression of the brake pedal BP, the brake fluid pressure of the wheel cylinder WC may increase due to the presence of the throttle D, but does not decrease. The throttle D may have a check valve function to prevent the flow of the brake fluid from the master cylinder MC to the wheel cylinder WC.

The speed at which the brake fluid pressure of the wheel cylinder WC is reduced is, for example, when the driver releases the depression of the brake pedal BP and depresses the accelerator pedal (change of pedal) on an uphill or the like, and the vehicle itself starts uphill. What is necessary is just to be able to secure time to prevent the vehicle from dragging backward until sufficient driving force is generated. The time required until the driving force sufficient for the vehicle itself to start a hill by changing the pedal is about 0.5 second.

When the speed of reducing the brake fluid pressure of the wheel cylinder WC is high, even if the solenoid valve SV is in the closed state, the brake force is released immediately after the brake pedal BP is released, and sufficient driving force is obtained. The vehicle is backing up the slope before you get Therefore, the purpose of facilitating starting on an uphill by the brake fluid pressure holding device RU cannot be achieved. Conversely, if the speed at which the brake fluid pressure of the wheel cylinder WC is reduced is low, even if the brake pedal BP is released, the vehicle continues to be in a well-operated state, so that the vehicle does not lean backwards. Extra time and power are required to secure a sufficient driving force to withstand, which is not preferable. Also, it is difficult to easily start the climb.

The speed at which the throttle D reduces the brake fluid pressure of the wheel cylinder WC is determined by the properties of the brake fluid and the type of the throttle D (shape such as the cross-sectional area and length of the flow path). Note that the throttle D is set to the solenoid valve SV and the check valve CV.
Alternatively, it may be provided integrally with the relief valve RV.
By combining them, the number of parts and the installation space can be reduced.

The check valve CV is provided as required. When the solenoid valve SV is closed and the driver steps on the brake pedal BP, the brake fluid pressure generated in the master cylinder MC is applied to the wheel cylinder WC. Play the role of communicating. The check valve CV is activated effectively when the brake fluid pressure generated in the master cylinder MC exceeds the brake fluid pressure of the wheel cylinder WC, and the brake of the wheel cylinder WC is quickly actuated in response to an increase in the driver's brake pedal BP. Increase hydraulic pressure. When the brake fluid pressure of the master cylinder MC is higher than the brake fluid pressure of the wheel cylinder WC, if the solenoid valve SV which has been closed is opened, the brake pedal BP can be controlled only by the solenoid valve SV. Therefore, it is not necessary to provide the check valve CV.

The relief valve RV is provided as necessary. When the solenoid valve SV is closed and the driver releases or depresses the brake pedal BP,
The brake fluid confined in the wheel cylinder WC is quickly brought to the master cylinder MC until a predetermined brake fluid pressure is reached.
Plays a role to escape to the side. The relief valve RV operates when the brake fluid pressure of the wheel cylinder WC is equal to or higher than a predetermined brake fluid pressure and higher than the brake fluid pressure of the master cylinder MC. Thus, even when the solenoid valve SV is in the closed state, the brake fluid pressure in the wheel cylinder WC that is more than necessary can be quickly reduced to a predetermined brake fluid pressure (relief pressure). Therefore, it takes time to reduce the brake fluid pressure of the wheel cylinder WC only by the throttle D after the brake pedal BP is depressed more than necessary at the time of starting uphill and the brake pedal BP is released. The problem of "undesirable" can be solved by the relief valve RV.

The brake switch BSW detects whether or not the brake pedal BP is depressed, and the ECU 6 issues an instruction to open or close the solenoid valve SV based on the detected value.

The brake fluid pressure holding device of the present invention can be constituted by various means other than the brake fluid pressure holding device RU shown in FIG. For example, a brake using a proportional solenoid valve capable of controlling the flow rate of the brake fluid by adjusting the opening of the solenoid valve as the brake fluid pressure decreasing speed reducing means, or a return speed of the brake pedal as the brake fluid pressure decreasing speed reducing means. There is a configuration that regulates itself. Also,
In a vehicle equipped with a traction control system, a brake fluid pressure holding function may be provided as one function of the traction control system.

<< Basic Operation of Brake Fluid Pressure Holding Device >> Next, a basic operation of the brake fluid pressure holding device RU will be described with reference to FIG.

(Stop / Start on Uphill) For example, when trying to stop on an uphill, the driver depresses the brake pedal BP from the running state. As a result, the brake fluid in the master cylinder MC is compressed, and the brake fluid pressure increases. Then, the brake fluid pressure is transmitted to the wheel cylinder WC through the brake fluid pipe FP and the solenoid valve SV in the open state with the flow of the brake fluid, and is converted into a braking force for braking the wheels. As a result, the vehicle stops on the slope.

The ECU 6 determines conditions such as that the vehicle is stopped, closes the solenoid valve SV, and holds the brake fluid pressure in the wheel cylinder WC. At this time, EC
U6 does not need to determine whether the place where the vehicle is stopped is on a slope. Note that even when the solenoid valve SV is closed, the driver can increase the braking force through the check valve CV by stepping on the brake pedal BP.

Next, the driver releases the brake pedal BP in order to start on a slope,
Depress the accelerator pedal (not shown). During this operation, since the solenoid valve SV is in the closed state, the braking force is maintained, and the vehicle does not retreat on the slope even if the driver releases the brake pedal BP. However, the brake fluid pressure in the wheel cylinder WC gradually decreases through the throttle D. Therefore, the braking force also gradually decreases. On the other hand, when the driver depresses the accelerator pedal, the driving force increases. Then, when the driving force is larger than the sum of the force of going down the hill due to the vehicle's own weight and the gradually decreasing braking force, the vehicle starts uphill on the hill.

With the aperture D, if the vehicle does not back down the slope for about 0.5 seconds after the driver releases the depression of the brake pedal BP, the driver can easily start uphill. Normally, brake pedal BP
This is because a sufficient starting drive force is generated 0.5 seconds after the pedal is released due to the depression of the accelerator pedal or the like. In some cases, the driver depresses the brake pedal BP more than necessary. In such a case, the brake fluid pressure in the wheel cylinder WC can be reduced to a predetermined brake fluid pressure (relief pressure) by releasing the brake pedal BP or releasing the brake pedal BP with the relief valve RV. Because it is possible, the hill can be started quickly.

If the solenoid valve SV is in the closed state forever after starting uphill, it is not preferable that the brake is dragged. Therefore, when the driver's start operation is performed,
It is preferable to perform control to open the solenoid valve SV. Specifically, the solenoid valve SV is opened when the accelerator pedal is depressed in an AT car or when the starting clutch is connected by depressing the accelerator pedal and returning the clutch pedal in an MT car. It is good to perform the control which performs. Further, as a fail-and-safe action, control for opening the solenoid valve SV may be performed after a predetermined time (for example, after 2 to 3 seconds) since the depression of the brake pedal BP is released. The depression of the brake pedal BP and the release of the depression are detected by the brake switch BSW.

(Stop / Start on Downhill) When stopping on a downhill, the driver depresses the brake pedal BP to stop, as in the case of uphill. The ECU 6 determines conditions such as that the vehicle is stopped, closes the solenoid valve SV, and holds the brake fluid pressure in the wheel cylinder WC, as in the case of an uphill. The ECU 6 does not determine whether the vehicle is going downhill or uphill as described above.

Next, the driver releases the brake pedal BP in order to go down the hill (to start).
In the case of a downhill, the driver may try to use the vehicle's own weight to go down a hill by releasing the brake pedal BP or relaxing the brake pedal without depressing the accelerator pedal. According to the brake fluid pressure holding device RU, even when the solenoid valve SV is in the closed state, the braking force is gradually weakened by the throttle D by releasing or loosening the depression of the brake pedal BP. Therefore, the vehicle can be started without depressing the accelerator pedal, as in the case of starting the vehicle downhill in a normal vehicle.

Further, when it can be determined that the driver intends to go downhill, it is better to eliminate unnecessary dragging of the brake and generate a braking force in accordance with the operation of the brake pedal BP by the driver. I can run.
Therefore, even when the starting drive force is not generated (for example, when the accelerator pedal is not depressed), the brake fluid pressure holding device RU opens the solenoid valve SV when the vehicle speed increases to a predetermined vehicle speed. Perform control. In addition,
In the present invention, the intention of the driver to go downhill is determined based on whether or not the vehicle speed has increased to a predetermined vehicle speed (20 km / h in the present embodiment). Therefore, when the vehicle speed is 20 km / h or less, the solenoid valve SV is maintained in the closed state, while the vehicle speed is 20 km / h.
When the speed exceeds km / h, the solenoid valve SV is opened, and the brake fluid pressure in the wheel cylinder WC is set to the brake fluid pressure according to the depression force of the brake pedal BP of the driver.

According to the brake fluid pressure holding device RU, the vehicle can easily start even on an uphill where starting is difficult. Also, there is no problem in starting the vehicle even on a downhill or a flat place. Further, when the driver determines that the driver intends to go downhill, the action of the brake fluid pressure in the wheel cylinder WC is released, and the vehicle can travel downhill smoothly.

[0043]

Next, the present invention will be described in more detail with reference to examples. In this embodiment, the brake fluid pressure holding device of the present invention is applied to an AT vehicle (hereinafter, referred to as a vehicle).

The vehicle described in this embodiment is a so-called hybrid vehicle having an engine and a motor as prime movers, and has a belt-type continuously variable transmission (hereinafter referred to as CVT) as a transmission. The brake hydraulic pressure holding device RU used in this vehicle is shown in FIG. 1 in which an electromagnetic valve SV, a throttle D, a relief valve RV, and a check valve CV are provided in a brake hydraulic circuit BC.

Further, in this vehicle, a driving force reducing device or / and / or a driving force reducing device for reducing the driving force of creep under the condition that the prime mover is in an idling state and at a predetermined vehicle speed or less and the brake pedal BP is depressed. A prime mover stopping device capable of automatically stopping the prime mover while the vehicle is stopped is provided. In addition, this vehicle has a configuration in which the depression of the brake pedal BP is released and the brake switch BSW is turned off, and at the same time, control for generating a driving force in the vehicle is automatically started.

<< System Configuration >> First, referring to FIG.
A system configuration of the vehicle according to the present embodiment will be described. The vehicle includes an engine 1 and a motor 2 as prime movers, and a CVT 3 that is a belt-type continuously variable transmission as a transmission. The engine 1 is controlled by a fuel injection electronic control unit (hereinafter, referred to as FIECU). The FIECU is integrally formed with a management electronic control unit (hereinafter, referred to as MG ECU), and is provided in a fuel injection / management electronic control unit (hereinafter, referred to as FI / MG ECU) 4. The motor 2 is controlled by a motor electronic control unit (hereinafter referred to as MOTECU) 5. Further, the CVT 3 is controlled by a CVT electronic control unit (hereinafter referred to as CVT ECU) 6.

Further, a drive shaft 7 on which drive wheels 8, 8 are mounted is mounted on the CVT 3. The drive wheels 8, 8
Disc brakes 9, 9 having a wheel cylinder WC (see FIG. 1) and the like are provided. The master cylinder MC is connected to the wheel cylinders WC of the disc brakes 9, 9 via a brake fluid pressure holding device RU. The depression from the brake pedal BP is transmitted to the master cylinder MC via the master power MP. The brake switch BP detects whether the brake pedal BP is depressed or not.

The engine 1 is an internal combustion engine that utilizes heat energy, and drives the drive wheels 8 via a CVT 3 and a drive shaft 7. In some cases, the engine 1 is automatically stopped when the vehicle stops to prevent deterioration of fuel efficiency. For this purpose, the vehicle includes a motor stop device that stops the engine 1 when an engine automatic stop condition is satisfied.

The motor 2 has an assist mode for assisting driving by the engine 1 by using electric energy from a battery (not shown). Further, the motor 2 has a regenerative mode in which kinetic energy due to rotation of the drive shaft 7 is converted into electric energy when assist is not required (during downhill, deceleration, etc.) and stored in a battery (not shown). It has a start mode for starting.

The CVT 3 changes the speed ratio steplessly by winding an endless belt between a drive pulley and a driven pulley, and changing the width of each pulley to change the winding radius of the endless belt. And CVT3
Connects the start clutch to the output shaft, engages the start clutch, and transmits the output of the engine 1 or the like shifted by the endless belt to the drive shaft 7 via the output gear of the start clutch. The vehicle including the CVT 3 is capable of creep running and includes a driving force reducing device that reduces the driving force of the creep. The driving force of creep is adjusted by the engaging force of the starting clutch, and has two magnitudes, a state where the driving force is large and a state where the driving force is small. The state where the driving force is large is a state where the driving force balances the inclination of 5 °, and is referred to as a strong creep state in the present embodiment. On the other hand, a state where the driving force is small is a state where there is almost no driving force, and is called a weak creep state in the present embodiment. In the strong creep state, when the accelerator pedal is released (that is, in the idling state), the travel range (D range,
When the (L range or R range) is selected, when the brake pedal BP is released, the vehicle moves slowly as if crawling. In the weak creep state, the vehicle is stopped or at a very low speed when the vehicle speed is equal to or lower than a predetermined low vehicle speed and the brake pedal BP is depressed. The position switch PS
The W range position is selected by the shift lever. The range of the position switch PSW is the P range used when parking and stopping, the N range which is neutral, the R range used when traveling backward, the D range used when traveling normally, and used when sudden acceleration or strong engine braking is required. There is an L range. The travel range is a range position where the vehicle can travel, and in this vehicle, the D range, L range
There are three ranges, a range and an R range. further,
When the D range is selected by the position switch PSW, the mode switch MSW can select the D mode as the normal driving mode and the S mode as the sports driving mode.

FI ECU included in FI / MG ECU 4
Controls the fuel injection amount so as to obtain the optimum air-fuel ratio, and controls the engine 1 as a whole. FIE
Information indicating the throttle opening and the state of the engine 1 is transmitted to the CU, and the CU is controlled based on each information. MGECU included in FI / MGECU 4
Controls mainly the MOTECU 5 and determines an automatic engine stop condition and an automatic engine start condition. Information indicating the state of the motor 2 is transmitted to the MGECU, and information indicating the state of the engine 1 and the like are input from the FIECU, and an instruction to switch the mode of the motor 2 is given to the MOTECU 5 based on each information. Further, information indicating the state of the CVT 3, information indicating the state of the engine 1, range information of the position switch PSW, information indicating the state of the motor 2, and the like are transmitted to the MGECU. Or determine the automatic start.

MOTECU 5 controls motor 2 based on a control signal from FI / MG ECU 4. FI /
The control signal from the MGECU 4 includes mode information for instructing the start of the engine 1 by the motor 2, assisting the driving of the engine 1 or regeneration of electric energy, an output request value for the motor 2, and the like. A command is issued to the motor 2 based on the instruction. Further, information is obtained from the motor 2 and the like, and information on the motor 2 such as the amount of power generation and the capacity of the battery are transmitted to the FI / MG ECU 4.

The CVT ECU 6 controls the gear ratio of the CVT 3 and the engaging force of the starting clutch. Information indicating the state of the CVT 3, information indicating the state of the engine 1, range information of the position switch PSW, and the like are transmitted to the CVT ECU 6. To the CVT 3. Further, the CVT ECU 6 turns ON / OFF (open / close) the solenoid valves SV, SV (see FIG. 1) of the brake fluid pressure holding device RU.
Is controlled, and it is determined whether the driving force of creep is set to a large state or a small state. Also, CVT
The ECU 6 includes a failure detection device DU for detecting a failure of the brake fluid pressure holding device RU. This failure detection device DU is a solenoid valve S of the brake fluid pressure holding device RU.
A drive circuit for turning on / off (opening / closing) V and SV is also provided.

The disc brakes 9, 9 are driven by wheels 8, 8,
The disk rotor, which rotates together with the disk rotor, is sandwiched between brake pads driven by a wheel cylinder WC (see FIG. 1), and a braking force is obtained by the frictional force. The brake fluid pressure of the master cylinder MC is supplied to the wheel cylinder WC via the brake fluid pressure holding device RU.

The brake fluid pressure holding device RU applies the brake fluid pressure to the wheel cylinder WC even after the brake pedal BP is released. Brake fluid pressure holding device RU
Are the solenoid valves SV, SV of the brake fluid pressure holding device RU in the failure detection device DU in the CVT ECU 6 (see FIG. 1).
Also includes a drive circuit for driving (ON / OFF) the. The ON / OFF of the solenoid valve SV means that
"In a normally open solenoid valve, when the solenoid valve is turned on, it means that the solenoid valve is closed and becomes closed, and when the solenoid valve is turned off, it means that the solenoid valve is opened and becomes open." On the other hand,
"In a normally-closed solenoid valve, when the solenoid valve is turned on, it means that the solenoid valve is opened and becomes open, and when the solenoid valve is turned off, it means that the solenoid valve is closed and becomes closed." The solenoid valves SV, SV in the present embodiment are normally open solenoid valves. Further, the drive circuit supplies current to each coil of the solenoid valves SV, SV to turn on the solenoid valves SV, SV, and stops the current supply to turn off the solenoid valves SV, SV. The master cylinder MC, master power M
P, the brake switch BSW, and the like are as described above.

The driving force reducing device provided in this vehicle has a CV
It is composed of a T3 and a CVT ECU 6. The driving force reduction device is used when the brake pedal BP is depressed and the vehicle speed is 5 km / h or less (at a predetermined low vehicle speed or less).
Then, the driving force of creep is reduced to change from a strong creep state to a weak creep state. The driving force reduction device is a CVT ECU
In step 6, whether or not the brake pedal BP is depressed is determined from the signal of the brake switch BSW, and whether or not the vehicle speed is 5 km / h or less is determined from the vehicle speed pulse of the CVT 3. Further, in addition to the above two basic conditions, the CVTECU 6 drives the brake fluid pressure holding device RU normally (the solenoid valves SV, SV (see FIG. 1) of the brake fluid pressure holding device RU) when the brake fluid temperature is equal to or higher than a predetermined value. (Including normal circuit)
Also, it is determined that the range of the position switch PSW is the D range, and when five conditions are satisfied, the driving force is reduced. The vehicle prevents deterioration of fuel efficiency by reducing the driving force by the driving force reduction device. In a weak creep state and when the engine 1 is stopped, C
The VT ECU 6 determines conditions for a strong creep. When the condition of strong creep is satisfied, CVT
A command to increase the engagement force of the starting clutch is transmitted from the ECU 6 to the CVT 3 to increase the creep driving force.

The motor stopping device provided in this vehicle is an FI
/ MG ECU 4 and the like. The motor stop device is
When the vehicle is stopped, the engine 1 can be stopped automatically. The motor stop device is FI / MGECU4
Determines the automatic engine stop condition such as the vehicle speed of 0 km / h. The engine automatic stop condition will be described later in detail. When it is determined that all the engine automatic stop conditions are satisfied, the FI / MG
An engine stop command is transmitted from the ECU 4 to the engine 1,
The engine 1 is automatically stopped. The vehicle further prevents fuel consumption from deteriorating due to the automatic stop of the engine 1 by the motor stop device. Note that when the engine 1 is automatically stopped by the motor stop device, the M
The GECU determines an engine automatic start condition. Then, when the engine automatic start condition is satisfied, FI / MG
An engine start command is transmitted from the ECU 4 to the MOTECU 5, and a command to start the engine 1 is transmitted from the MOTECU 5 to the motor 2.
Is automatically started and a strong creep condition is set. The automatic engine start condition will be described later in detail.

Next, signals transmitted and received in this system will be described. Note that “F_” added before each signal in FIG. 2 indicates that the signal is flag information of 0 or 1, and “V_” indicates that the signal is numerical information (unit is arbitrary). "I_" indicates that the signal is information including a plurality of types of information.

The signal transmitted from FI / MG ECU 4 to CVT ECU 6 will be described. V_MOTTRQ
Is an output torque value of the motor 2. F_MGSTB
Is F_CV in the automatic engine stop condition described later.
This flag indicates whether or not all the conditions except for the five conditions of TOK are satisfied. The flag is 1 when the condition is satisfied, and is 0 when the condition is not satisfied. By the way, F_MGST
When both B and F_CVTOK are switched to 1, the engine 1 is automatically stopped, and when either of the flags is switched to 0, the engine 1 is automatically started.

The signals transmitted from FI / MG ECU 4 to CVT ECU 6 and MOTECU 5 will be described. V
_NEP is the rotation speed of the engine 1.

The signal transmitted from CVT ECU 6 to FI / MG ECU 4 will be described. F_CVTOK is
The CVT 3 is in a weak creep state, the ratio (pulley ratio) of the CVT 3 is low, the oil temperature of the CVT 3 is a predetermined value or more, the brake fluid temperature is a predetermined value or more, and the brake fluid pressure holding device RU is normal (the electromagnetic pressure of the brake fluid pressure holding device RU). Valves SV, SV (FIG. 1)
5) indicates whether or not the five conditions (including normal operation of the drive circuit) are satisfied. The flag indicates whether all of the five conditions are satisfied, and 1 if at least one of the conditions is not satisfied. 0. When the engine is stopped, CVT
3 weak creep, CVT3 ratio low, CVT
The condition that the oil temperature is equal to or higher than the predetermined value and the brake fluid temperature is equal to or higher than the predetermined value is maintained, and F_CVTOK is determined only by whether or not the brake hydraulic pressure holding device RU is normal. That is,
When the engine is stopped, if the brake fluid pressure holding device RU is normal, F_CVTOK is 1, and the brake fluid pressure holding device RU
Is a fault, F_CVTOK is zero. F_CV
TTO is a flag indicating whether the oil temperature of the CVT 3 is equal to or higher than a predetermined value, and is 1 when the oil temperature is equal to or higher than the predetermined value, and is 0 when the oil temperature is lower than the predetermined value. The oil temperature of the CVT 3 is estimated from the electric resistance of the linear solenoid valve that controls the hydraulic pressure of the starting clutch of the CVT 3. F_POSR is a flag indicating whether or not the range of the position switch PSW has been selected to be the R range, and is 1 for the R range and 0 for other than the R range. F_POSDD is a flag indicating whether or not the range of the position switch PSW is the D range and the mode of the mode switch MSW is the D mode, and is 1 when the D mode is the D range, and 1 when the mode is other than the D range D mode. 0. In addition, FI / MGE
CU4 is D range D mode, R range, P range, N
If the information indicating the range has not been input, the D range S
It is determined that either the mode or the L range has been selected.

From engine 1 to FI / MG ECU 4 and CV
The signal transmitted to the TECU 6 will be described. V_A
NP is a negative pressure value of the intake pipe of the engine 1. V_TH
Is the throttle opening. V_TW is engine 1
Is the cooling water temperature. V_TA is the intake air temperature of the engine 1. Note that the brake fluid temperature of the brake fluid pressure holding device RU disposed in the engine room is estimated based on the intake air temperature. This is because both change in relation to the temperature of the engine room.

From CVT 3 to FI / MGECU 4 and CVT
The signal transmitted to the ECU 6 will be described. V_VS
P1 is a vehicle speed pulse output from one of two vehicle speed pickups provided in CVT3. The vehicle speed is calculated based on the vehicle speed pulse.

The signal transmitted from CVT 3 to CVT ECU 6 will be described. V_NDRP is a pulse indicating the rotation speed of the drive pulley of the CVT 3. V_NDN
P is a pulse indicating the rotation speed of the driven pulley of the CVT 3. V_VSP2 is a vehicle speed pulse output from the other of the two vehicle speed pickups provided in CVT3. Note that V_VSP2 has higher accuracy than V_VSP1, and is used for calculating the slip amount of the starting clutch of the CVT3.

The signal transmitted from MOTECU 5 to FI / MG ECU 4 will be described. V_QBAT is the remaining capacity of the battery. V_ACTTRQ is the motor 2
, Which is the same value as V_MOTTRQ. I_MOT is information such as a power generation amount of the motor 2 indicating an electric load. In addition, all the electric power consumed by this vehicle including the motor driving electric power is generated by the motor 2.

The signal transmitted from FI / MG ECU 4 to MOTECU 5 will be described. V_CMDPWR
Is an output request value for the motor 2. V_ENGT
RQ is an output torque value of the engine 1. I_MG
Is information such as a start mode, an assist mode, and a regenerative mode for the motor 2.

The signal transmitted from master power MP to FI / MG ECU 4 will be described. V_M / PNP is
This is a negative pressure detection value of the constant pressure chamber of the master power MP.

From position switch PSW to FI / MG
The signal transmitted to the ECU 4 will be described. Only when either the N range or the P range is selected by the position switch PSW, N or P is transmitted as position information.

The signal transmitted from CVT ECU 6 to CVT 3 will be described. V_DRHP is a hydraulic pressure command value to the linear solenoid valve that controls the hydraulic pressure of the cylinder of the drive pulley of the CVT 3. V_DNHP is CVT
This is a hydraulic command value to the linear solenoid valve that controls the hydraulic pressure of the cylinder of the driven pulley No. 3. Note that V_DRH
The gear ratio of CVT3 is changed by P and V_DNHP.
V_SCHP is a hydraulic pressure command value to the linear solenoid valve that controls the hydraulic pressure of the starting clutch of CVT3. In addition,
V_SCHP changes the engaging force of the starting clutch.

The signal transmitted from CVT ECU 6 to brake fluid pressure holding device RU will be described. F_SOLA
Is a flag for turning on / off the solenoid valve SV (A) (see FIG. 1) of the brake fluid pressure holding device RU.
The value is 1 when it is to be turned off, and 0 when it is turned off. F_S
OLB is the solenoid valve SV of the brake fluid pressure holding device RU.
(B) is a flag for turning ON / OFF (see FIG. 1), and is 1 when it is turned ON and 0 when it is turned OFF.

From position switch PSW to CVTEC
The signal transmitted to U6 will be described. Which position of the N range, P range, R range, D range or L range is selected by the position switch PSW is transmitted as position information.

Mode switch MSW to CVT ECU 6
Will be described. Mode switch M
Whether the D mode (normal running mode) or the S mode (sports running mode) is selected by SW is transmitted as mode information. The mode switch MSW
Is a mode selection switch that functions when the position switch PSW is set to the D range.

From the brake switch BSW to FI / MGE
The signals transmitted to the CU 4 and the CVT ECU 6 will be described. F_BKSW indicates whether the brake pedal BP is depressed (ON) or the depression is released (OFF)
The flag is 1 when the pedal is depressed, and is 0 when the pedal is released.

<< When the brake fluid pressure is maintained >>
A case where the brake fluid pressure is held by the brake fluid pressure holding device RU in the vehicle having the system configuration will be described. As shown in FIG. 3A, the brake fluid pressure is maintained when I) the driving force of the vehicle is in a weak creep state, and II) the vehicle speed is 0 km / h.
When this condition is satisfied, the two solenoid valves SV, SV (the solenoid valves A and B) are both closed, and the brake fluid pressure is held in the wheel cylinder WC. It should be noted that the driving force enters the weak creep state (F_WCRPON = 1) after the weak creep command (F_WCRP = 1) is issued.

I) The condition of "weak creep state" is as follows.
On a slope, the brake pedal BP is strong enough for the driver.
Is to be stepped on. That is, in the strong creep state, the driver has a driving force so that the vehicle does not back up even on a slope having an inclination of 5 degrees, so that the driver can stop the vehicle on the slope without strongly depressing the brake pedal BP. Therefore, the driver may depress the brake pedal BP only weakly. In such a case, if the solenoid valve SV is closed and the engine 1 is further stopped, the vehicle moves backward on a slope.

II) The condition that the vehicle speed is 0 km / h is because the vehicle cannot be stopped at an arbitrary position if the solenoid valve SV is closed during traveling.

[Weak creep command condition] As shown in FIG. 3 (a), the weak creep command (F_WCRP) includes: 1) that the brake fluid pressure holding unit RU is normal; There is (F_BKTO), 3) The brake switch BP is turned on when the brake pedal BP is depressed
(F_BKSW), 4) The vehicle speed is 5 km /
h (F_VS), 5) The position switch PSW is in the D range (F_POSD),
Is issued when all of the conditions are satisfied. The driving force is set to be in the weak creep state in addition to the reason that the driver strongly depresses the brake pedal BP as described above, and also the reason that fuel efficiency is improved.

1) The weak creep command is not issued when the brake fluid pressure holding device RU is not normal because, for example,
If there is an abnormality such as the solenoid valve SV not being closed, if the weak creep command is issued and the vehicle is in the weak creep state, the brake fluid pressure is not held in the wheel cylinder WC. This is because, when the driver steps on the vehicle, the braking force is lost at once and the vehicle moves backward on the slope. In this case, by maintaining a strong creep state, backward movement on a slope is prevented, and starting on a slope (starting on a slope) is facilitated.

2) The reason why the weak creep command is not issued when the brake fluid temperature is lower than the predetermined value is that when the brake fluid pressure is low and the solenoid valve SV is closed by operating the brake fluid pressure holding device RU, the brake pedal This is because when the depression of the BP is partially relaxed, there is a problem that the rate of decrease in the brake fluid pressure of the wheel cylinder WC becomes extremely slow. That is, only by depressing the brake pedal BP, the brake switch BSW remains ON and the solenoid valve SV is kept closed forever. Accordingly, the brake fluid is discharged only through the narrow throttle D. However, since the brake fluid has a high viscosity when the temperature is low, the brake fluid does not flow at a desired speed, so that the brake force is maintained in a strong state forever. This is because they will be left behind. As described above, when the brake fluid temperature is low, the weak creep state is prohibited, the strong creep state is maintained, and backward movement on a slope is prevented. By the way, if the strong creep state is maintained, the brake fluid pressure holding device RU does not operate, and the solenoid valve SV does not close. In the case of a brake fluid pressure holding device having a configuration in which no throttle is provided in the brake fluid pressure circuit, for example, in the case of a brake fluid pressure holding device having a configuration using a proportional solenoid valve capable of changing the valve opening, The importance of controlling the temperature of the brake fluid is not very high. Also, in the case of a brake fluid pressure holding device configured to delay the return of the brake pedal itself, the temperature management of the brake fluid is not so important. Therefore, even when the brake fluid temperature is low to some extent, a weak creep command can be issued.

3) The reason why the weak creep command is not issued when the brake pedal BP is not depressed (F_BKSW) is that the driver does not want to at least reduce the driving force.

4) The reason why the weak creep command is not issued when the vehicle speed is 5 km / h or more is that the reverse driving force from the driving wheels 8 and 8 is transmitted to the engine 1 and the motor 2 via the starting clutch and the engine braking is performed. This is because the regenerative power generation by the motor may be performed.

5) Unlike the case where the position switch PSW is in the D range, no weak creep command is issued when the position switch PSW is in the R range or the L range. This is for facilitating garage entry due to strong creep running.

Whether or not the vehicle is in the weak creep state is determined based on the hydraulic pressure command value for the CVT starting clutch. The flag F_WCRPON in the weak creep state continues until the next strong creep state.

[Automatic Engine Stop Condition] In order to further improve fuel efficiency, the engine 1 is automatically stopped by the motor automatic stop device when the vehicle is stopped. This condition will be described. When all of the following conditions are satisfied, an engine stop command (F_ENGOFF) is issued, and the engine 1 automatically stops (see FIG. 3B).

1) The position switch PSW is in the D range and the mode switch MSW is in the D mode (hereinafter, this state is referred to as “D range D mode”). In other than the D range D mode, unless the ignition switch is turned off. , The engine 1 is not automatically stopped. For example, when the position switch PSW is in the P range or the N range,
This is because if a command to automatically stop the engine 1 is issued and the engine 1 is stopped, the driver may leave the vehicle assuming that the ignition switch has been turned off. The position switch PSW
Is in the D range and the mode switch MSW is in the S mode (hereinafter, this state is referred to as “D range S mode”), the engine 1 is not automatically stopped. The driver is D
This is because in the range S mode, it is expected that the vehicle can be started quickly. Further, the reason why the engine 1 is not automatically stopped when the position switch PSW is in the L range or the R range is that it is troublesome for the driver if the engine 1 is automatically stopped frequently when the vehicle is put in a garage or the like.

2) The brake pedal BP is depressed and the brake switch BSW is ON; this is to call the driver's attention. When the brake switch BSW is ON, the driver has put his foot on the brake pedal BP. Therefore, even if the driving force is lost due to the automatic stop of the engine 1 and the vehicle starts moving backward on the slope, the driver can easily increase the brake pedal BP.

3) After starting the engine, once the vehicle speed is 5 km /
h or more; in order to make it easy to put in and out of the garage during creep running. This is because it is troublesome for the driver if the engine 1 is automatically stopped every time the vehicle 1 is stopped due to a switching operation when the vehicle is taken in and out of the garage.

4) The vehicle speed is 0 km / h; if the vehicle is stopped, no driving force is required. 5) The battery capacity is equal to or greater than a predetermined value; this is to prevent a situation where the engine 2 cannot be restarted by the motor 2 after the engine is stopped. 6) The electric load must be less than the specified value; this is to ensure the supply of electricity to the load. If the electric load is equal to or less than the predetermined value, there is no problem even if the engine 1 is automatically stopped.

7) The negative pressure in the constant pressure chamber of the master power MP is equal to or higher than a predetermined value; When the engine 1 is automatically stopped while the negative pressure in the constant pressure chamber is small, the negative pressure in the constant pressure chamber becomes
This is because the negative pressure in the constant-pressure chamber is further reduced, the amplification of the depression force when the brake pedal BP is depressed is reduced, and the effectiveness of the brake is reduced.

8) The accelerator pedal is not depressed; the driver does not want to increase the driving force, and there is no problem even if the engine 1 is automatically stopped.

9) The CVT 3 is in a weak creep state; this is for preventing the vehicle from moving backward even after the engine is stopped by forcing the driver to depress the brake pedal BP strongly. That is, when the engine 1 is started, backward movement on a slope is prevented by the sum of the braking force and the creep force. For this reason, in the strong creep state, the driver may adjust the depression of the brake pedal BP and depress it only weakly. Therefore, the engine 1 is automatically stopped after the weak creep state.

10) The ratio of CVT3 is low;
If the ratio (pulley ratio) of the CVT 3 is not low, the engine 1 is not automatically stopped because smooth start may not be performed. Therefore, for a smooth start, CV
When the ratio of T3 is low, the engine 1 is automatically stopped.

11) The water temperature of the engine 1 is equal to or higher than a predetermined value;
Is preferably performed in a stable state. If the water temperature is low, the engine 1 may not be restarted in a cold region, so the automatic stop of the engine 1 is not performed.

12) The oil temperature of the CVT 3 is equal to or higher than a predetermined value; when the oil temperature of the CVT 3 is low, the actual rise of the hydraulic pressure of the starting clutch is delayed, and the engine 1 is brought into a strong creep state from the start. Since it takes time until the vehicle moves backward on a slope, the engine 1 is not automatically stopped.

13) The temperature of the brake fluid is equal to or higher than a predetermined value; if the temperature of the brake fluid is low, the fluid resistance in the throttle D increases, causing unnecessary brake dragging. For this reason, the brake hydraulic pressure holding device RU is not operated. Therefore, the automatic stop and the weak creep state of the engine 1 are prohibited, and the descent on the slope is prevented by the strong creep. In the case of a brake fluid pressure holding device having a configuration in which no throttle is provided in the brake fluid pressure circuit, for example,
In the case of a brake fluid pressure holding device that uses a proportional solenoid valve that can change the opening of the valve, or in the case of a brake fluid pressure holding device that slows the return of the brake pedal itself, the temperature management of the brake fluid is Not so important. Therefore, even when the brake fluid temperature is low to some extent, the engine automatic stop command can be issued.

14) The brake fluid pressure holding device RU is normal. If the brake fluid pressure holding device RU is abnormal, the brake fluid pressure may not be able to be held. Be careful not to let the vehicle back on the slope. Therefore, when there is an abnormality in the brake fluid pressure holding device RU, the engine 1 is not automatically stopped. On the other hand, if the brake fluid pressure holding device RU is normal, there is no problem even if the engine 1 is automatically stopped.

<< When the holding of the brake fluid pressure is released >>
As shown in FIG. 4 (a), the solenoid valve SV that has been once closed is in a state of I) when a predetermined delay time elapses after the brake pedal BP is released, and II) the driving force is in a strong creep state. III) When the vehicle speed reaches a predetermined vehicle speed (20 km /
When the pressure rises to h), the wheel cylinder WC is opened when any one of the conditions is satisfied, and the holding of the brake fluid pressure in the wheel cylinder WC is released.

I) The delay time is determined when the brake pedal BP is released (when the brake switch BSW is
FF). The delay time is about 2 to 3 seconds, and the solenoid valve SV is opened as a fail-and-safe action to eliminate dragging of the brake.

II) The solenoid valve SV is opened when the driving force is in a strong creep state, because the strong creep state has a driving force capable of stopping the vehicle against a hill of 5 degrees. This is because it is not necessary to hold the brake fluid pressure in the wheel cylinder WC to prevent the vehicle from moving backward. The strong creep state is set after the strong creep command (F_SCRP) is issued, but the strong creep command is issued when the brake pedal BP is released in the D range.

III) The vehicle speed is a predetermined vehicle speed (20 km /
When the vehicle speed reaches 20 km / h, the driver determines that the driver intends to go downhill and eliminates unnecessary dragging of the brake when the vehicle speed reaches 20 km / h. That is, when the driver loosens the brake pedal BP (or releases the depression) and intends to go downhill, a braking force corresponding to the driver's operation of the brake pedal BP is generated, and the driver smoothly operates. Be able to run downhill. It should be noted that since the vehicle speed has increased to 20 km / h when the vehicle is in a weak creep state (that is, a state in which no starting driving force is generated), the vehicle obtains propulsive power other than the driving force of the prime mover. In the running of the vehicle, the propulsive force of the vehicle other than the driving force of the prime mover is obtained on a downhill slope by the propulsive force of the vehicle's own weight and the braking force reduced by the driver loosening or releasing the brake pedal BP. be able to. On a downhill, the driver loosens or releases the brake pedal BP when the driver runs downhill. Therefore, when the vehicle speed increases to 20 km / h in the weak creep state, it can be determined that the driver intends to go downhill.

[Automatic engine start conditions] After the engine 1 is automatically stopped, the engine 1 automatically starts under the following conditions. This engine automatic start condition will be described (FIG. 4B).
reference). The engine 1 automatically starts when any of the following conditions is satisfied.

1) D range D mode and brake pedal BP is released; engine 1 is automatically started because it is determined that the driver's start operation has been started.

2) When the mode is switched to the D range S mode: When the engine is automatically stopped in the D range D mode and then switched to the D range S mode, the engine 1 is automatically started. This is because the driver expects a quick start in the D range S mode, and automatically starts the engine 1 without waiting for the brake pedal BP to be released.

3) When the accelerator pedal is depressed;
This is because the driver expects the driving force of the engine 1.

4) When the range is switched to the P range, the N range, the L range, and the R range; When the engine 1 is automatically stopped in the D range D mode and then switched to the P range, the engine 1 is automatically started. If the engine 1 is not automatically started when the range is switched to the P range or the N range, the driver thinks that the ignition switch has been turned off or thinks that there is no need to turn off the ignition switch, and leaves the vehicle as it is. This is not preferable from the viewpoint of fail-safe.
In order to prevent such a situation, the engine 1 is restarted. The reason why the engine 1 is automatically started when the range is switched to the L range or the R range is that it is determined that the driver intends to start.

5) When the battery capacity falls below a predetermined value: If the battery capacity does not exceed the predetermined value, the engine 1
Is not automatically stopped, the battery capacity may be reduced even after the engine 1 is automatically stopped once. In this case, for the purpose of charging the battery, the engine 1
To start automatically. Note that the predetermined value is set to a value higher than the limit battery capacity at which the engine 1 cannot be automatically started if the battery capacity further decreases.

6) When the electric load exceeds a predetermined value;
For example, when an electric load such as lighting is operating, the battery capacity is rapidly reduced, and the engine 1 cannot be restarted. Therefore, when the electric load is equal to or more than the predetermined value regardless of the battery capacity, the engine 1 is automatically started.

7) When the negative pressure of the master power MP falls below a predetermined value: When the negative pressure of the master power MP decreases, the braking force of the brake decreases, and the engine 1 is automatically started to secure this. .

8) When the brake fluid pressure holding device RU is out of order; When the solenoid valve SV or the drive circuit of the solenoid valve SV is out of order, the engine 1 is started to make a strong creep state. If a failure is detected in the brake fluid pressure holding device RU including the drive circuit of the solenoid valve SV after the automatic stop of the engine 1, the brake fluid pressure may be held when the brake pedal BP is released when the vehicle starts moving. In some cases, the engine 1 is automatically started when a failure is detected in order to set a strong creep state. That is, the vehicle is prevented from moving backward in the strong creep state, and the vehicle can be easily started uphill.

<< Control Time Chart in Normal Time >> Next, with reference to FIG. 5, the control when the vehicle equipped with the above system is decelerated, stopped, and started will be described. The position switch PSW and the mode switch MSW of the vehicle are used.
Is not changed in the D mode D range. The upper part of the time chart in FIG. 5A is a diagram showing, in chronological order, increases and decreases in the driving force and the braking force of the vehicle. The thick line in the figure indicates the driving force, and the thin line indicates the braking force.
The lower part of the time chart in FIG. 5A is a diagram showing the open / closed state of the solenoid valve SV. FIG. 5B is a diagram showing a state of the brake hydraulic circuit at the time of stoppage, and the solenoid valve SV is in a closed state.

First, in FIG. 5A, when the vehicle is running,
When the driver steps on the brake pedal BP (the brake S
W [ON]), the braking force increases. When the driver depresses the brake pedal BP, the driver releases the depression of the accelerator pedal, so that the driving force is reduced, and eventually the vehicle enters a strong creep state (normal idling state). And
The brake pedal BP is continuously depressed and the vehicle speed is 5 km
/ H or less, a weak creep command (F_WCRP) is issued, the driving force is further reduced, and the weak creep state (F
_WCRPON).

When the vehicle speed becomes 0 km / h, the solenoid valve SV is closed and the engine 1 is automatically stopped (F_ENGOFF), and the driving force is lost. At this time, since the solenoid valve SV is closed, the brake fluid pressure is held in the wheel cylinder WC. Also, Engine 1
Stops after passing through the weak creep condition, the driver must make the brake pedal B strong enough so that the vehicle does not back up on the slope.
Stepping on P. Therefore, even if the engine 1 automatically stops, the vehicle does not move backward (reverse restraining force). Even if the driver steps backward, the driver can slightly increase the brake pedal BP to prevent the driver from moving backward. Since the driver is in the state where the brake pedal BP is depressed (the state where the foot is put on the brake pedal BP), the driver can easily increase the brake pedal BP without panic. The reason why the engine 1 is automatically stopped is to improve fuel efficiency and eliminate generation of exhaust gas. Conditions for setting the driving force to a weak creep state, conditions for closing the solenoid valve SV, and conditions for automatically stopping the engine 1 include:
This has already been described with reference to FIG.

Next, the driver releases the brake pedal BP to restart the vehicle. In addition,
FIG. 5A shows a case where the driver has depressed the brake pedal BP to a level higher than the set pressure (relief pressure) of the relief valve RV.
As shown in (2), when the brake pedal BP is released, the relief valve RV operates, and the braking force is reduced to the relief pressure in a short time. With this relief valve RV, even when the driver is depressing the brake pedal BP more than necessary, it is possible to quickly start uphill.

When the depression of the brake pedal BP is completely released (brake SW [OFF]), an engine automatic start command (F_ENGON) is issued, and after a time lag due to signal communication and a delay in the mechanical system, the engine 1 is automatically activated. Start. Then, the driving force increases, and a strong creep state (F_SCRPON) is set. When the brake pedal BP is released (the brake switch BSW is turned off)
) To a strong creep state is about 0.5 seconds. During this time, the solenoid valve SV maintains the closed state, so that the brake fluid in the wheel cylinder WC can move toward the master cylinder MC only through the throttle D. Therefore, the braking force is reduced only gradually, and the rearward movement of the vehicle is prevented.

Then, in the strong creep state (F_SCRPO
At N), the vehicle generates a driving force that can withstand a slope. In order to prevent the vehicle from being hindered by the braking force or to prevent unnecessary dragging of the brake, the vehicle is operated in the solenoid valve SV in the closed state.
Is opened, and the brake fluid pressure of the wheel cylinder WC is reduced at a stretch to eliminate the braking force. Thereafter, the driving force increases by further depressing the accelerator pedal, and the vehicle accelerates. The conditions for setting the driving force to the strong creep state and the conditions for setting the solenoid valve SV to the open state are as already described with reference to FIG.

In the line indicating the braking force in the upper part of FIG. 5A, the imaginary line extending obliquely downward to the right from the “relief pressure” portion indicates the case where the brake fluid pressure is not maintained. In this case, the braking force is reduced and disappears without delaying the reduction in the depressing force of the brake pedal BP, so that it is not easy to start uphill. Also, in the line indicating the braking force in the upper diagram of FIG. 5A, a virtual line that gradually decreases to the lower right from the portion where the solenoid valve SV is in the open state does not indicate that the solenoid valve SV is in the open state. The situation of the reduction of the braking force in the case is shown. When the braking force is reduced as shown by the imaginary line, the brake is dragged, which is not preferable. V_BKDLY in the lower part of FIG. 5A indicates a delay time. After the delay time has elapsed, the solenoid valve SV is opened regardless of the situation as a fail-and-safe action.

<< Control Time Chart on Downhill (1) >> Next, with reference to FIG. 6, control when the vehicle having the same configuration as that described with reference to FIG. 5 decelerates, stops, and starts on a downhill will be described. Note that the position switch PSW and the mode switch MSW of the vehicle are not changed in the D mode D range. The upper part of the time chart in FIG. 6 is a diagram showing, in chronological order, changes in the driving force and the braking force of the vehicle. The thick line in the figure indicates the driving force, and the thin line indicates the braking force. The time chart in the middle part of FIG. 6 shows the vehicle speed. The lower time chart of FIG. 6 is a diagram showing the open / closed state of the solenoid valve SV.

Since the control shown in FIG. 6 is the same as the control shown in FIG. 5 until the vehicle stops, the description is omitted. In addition,
In order to stop the vehicle on a downhill, the driver depresses the brake pedal BP more strongly than stopping the vehicle on a flat ground. This is because, on a downhill, there is a propulsive force in a direction going downhill due to the weight of the vehicle. for that reason,
This is because stopping on a downhill requires a braking force that exceeds the propulsion force.

In order for the driver to restart the vehicle,
Release the brake pedal BP. When the driver depresses the brake pedal BP to a pressure equal to or higher than the set pressure (relief pressure) of the relief valve RV, the relief valve R is released by releasing the brake pedal BP as shown in FIG.
V is activated, and the braking force is reduced to the relief pressure in a short time.

After the braking force has been reduced to the relief pressure,
In the case of a steep downhill, the vehicle starts to go downhill due to a reduction in propulsive force and braking force due to the vehicle's own weight. The vehicle then increases in speed.

When the depression of the brake pedal BP is completely released (brake SW [OFF]), an engine automatic start command (F_ENGON) is issued, and after a time lag due to signal communication and a delay in the mechanical system, the engine 1
Starts automatically.

When the vehicle speed reaches 20 km / h before the driving force increases and the vehicle enters a strong creep state (F_SCRPON) (that is, before the starting driving force is generated), the vehicle closes the solenoid valve SV. To an open state to conduct the master cylinder MC and the wheel cylinder WC. Then
The brake fluid in the wheel cylinder WC flows into the master cylinder, and the braking force is lost. Therefore, the vehicle goes downhill without unnecessary brake dragging. As a result, the vehicle speed further increases.

In the control shown in FIG. 6, the depression of the brake pedal BP is released in the D range D mode (the brake S
W [OFF]), the engine 1 was automatically started. However, when the vehicle travels while partially depressing the brake pedal BP and the vehicle speed reaches 20 km / h, the vehicle is stopped in the state where the engine 1 is stopped (that is, the state where there is no driving force), and The valve SV is changed from the closed state to the open state. Then, the driver can travel downhill while controlling the depression force of the brake pedal BP without unnecessary dragging of the brake.

<< Control Time Chart on Downhill (2) >> Next, referring to FIG. 7, if the engine 1 is not automatically stopped at the time of stopping the vehicle in the control described in FIG. Control when decelerating, stopping, and starting will be described. The reason why the engine 1 is not automatically stopped when the vehicle is stopped may be a case where the vehicle does not have a motor stop device or a case where the vehicle is provided with a motor stop device.
The condition (b) may not be satisfied. Note that the position switch PSW and the mode switch MSW of the vehicle are not changed in the D mode D range. The upper part of the time chart in FIG. 7 is a diagram showing, in chronological order, increases and decreases in the driving force and the braking force of the vehicle. The thick line in the figure indicates the driving force, and the thin line indicates the braking force. The middle time chart in FIG. 7 shows the vehicle speed. The lower part of the time chart in FIG. 7 is a diagram showing the open / closed state of the solenoid valve SV.

Since the control shown in FIG. 7 is the same as the control shown in FIG. 5 until the vehicle stops, the description is omitted. However, even if the vehicle speed becomes 0 km / h, the engine 1 is not automatically stopped because the engine automatic stop condition is not satisfied or the engine stop device is not provided. Therefore, the driving force is maintained in the weak creep state. In order to stop the vehicle on a downhill, the driver depresses the brake pedal BP more strongly than when stopping on a flat ground. This is because, on a downhill, there is a propulsive force in a direction going downhill due to the weight of the vehicle. Therefore, in order to stop on a downhill, a braking force exceeding the propulsion force is required.

In order for the driver to restart the vehicle,
Release the brake pedal BP. When the driver has depressed the brake pedal BP at a pressure higher than the set pressure (relief pressure) of the relief valve RV, the relief valve R is released by releasing the depression of the brake pedal BP as shown in FIG.
V is activated, and the braking force is reduced to the relief pressure in a short time.

After the braking force has been reduced to the relief pressure,
In the case of a steep downhill, the vehicle starts to go downhill due to a reduction in propulsive force and braking force due to the vehicle's own weight. The vehicle then increases in speed.

When the depression of the brake pedal BP is completely released (brake SW [OFF]), a strong creep command (F_SCRP) is issued, and the driving force increases.

When the vehicle speed reaches 20 km / h before the driving force increases and the vehicle enters a strong creep state (F_SCRPON) (ie, before the starting driving force is generated), the vehicle closes the solenoid valve SV. To an open state to conduct the master cylinder MC and the wheel cylinder WC. Then
The brake fluid in the wheel cylinder WC flows into the master cylinder, and the braking force is lost. Therefore, the vehicle goes downhill without unnecessary brake dragging. As a result, the vehicle speed further increases.

In the control shown in FIG. 7, the brake pedal BP is released in the D range D mode (the brake S
W [OFF]), a strong creep command (F_SC)
RP). However, the vehicle is run by partially depressing the brake pedal BP, and the vehicle speed is 20 km / h.
, The vehicle maintains the weak creep state, and changes the solenoid valve SV from the closed state to the open state. Then, the driver can use the brake pedal BP without dragging unnecessary brakes.
It is also possible to drive downhill while controlling the stepping force of the vehicle.

As described above, the present invention is not limited to the above-described embodiment, but may be embodied in various forms. For example, the predetermined vehicle speed at which the operation of the brake fluid pressure in the wheel cylinder by the brake fluid pressure holding device is released is set to 20 km / h, but the numerical value is not particularly limited, and it can be determined that the driver intends to go downhill. The vehicle speed. In addition, as a configuration of the brake fluid pressure holding device, the brake fluid pressure in the wheel cylinder is held by the brake fluid pressure decreasing speed reducing means by the throttle and the solenoid valve, but the means capable of holding the brake fluid pressure in the wheel cylinder is particularly limited. Not a thing,
One of the functions of the traction control system may be one that holds the brake fluid pressure.

[0132]

According to the brake fluid pressure holding device of the present invention, when the driver intends to go downhill, the driver does not receive the action of the brake fluid pressure in the wheel cylinder by the brake fluid pressure holding device. Thus, a braking force corresponding to the operation of the brake pedal can be generated. Therefore, the driver can smoothly go downhill only by adjusting the depression force of the brake pedal.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a brake fluid pressure holding device according to the present invention.

FIG. 2 is a system configuration diagram of a vehicle including the brake fluid pressure holding device according to the present invention.

3A and 3B are control logics of the brake fluid pressure holding device according to the present invention when the vehicle is stopped, wherein FIG. 3A is a control logic for closing an electromagnetic valve, and FIG. 3B is a control logic for automatically stopping an engine. .

4A and 4B are control logics of the brake fluid pressure holding device according to the present invention when the vehicle starts, wherein FIG. 4A is a control logic for opening an electromagnetic valve and FIG. 4B is a control logic for automatically starting an engine. .

FIG. 5 is a control time chart of a vehicle provided with the brake fluid pressure holding device according to the present invention, wherein (a) shows the deceleration of the vehicle →
The change of the driving force and the braking force along the time sequence of stop → start, and the opening / closing state of the solenoid valve are shown, and FIG. 2B is a configuration diagram of a brake hydraulic circuit when the vehicle stops.

FIG. 6 is a control time chart corresponding to FIG. 5 in a case where no starting drive force is generated at the time of starting the vehicle and a case where the vehicle speed has increased to a predetermined vehicle speed.

FIG. 7 is a control time chart corresponding to FIG. 6 when the engine is not automatically stopped when the vehicle stops.

[Explanation of symbols]

 BP: brake pedal RU: brake fluid pressure holding device WC: wheel cylinder

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Toshiya Kanda 1-4-1 Chuo, Wako-shi, Saitama Pref. Honda Technology Laboratory Co., Ltd. (72) Inventor Satoshi Haneda 1-4-1 Chuo, Wako-shi, Saitama Inside Honda R & D Co., Ltd. (72) Inventor Takahiro Eguchi 1-4-1 Chuo, Wako-shi, Saitama Prefecture Inside Honda R & D Co., Ltd. (72) Hirotoshi Inoue 1-4-1 Chuo, Wako-shi, Saitama Pref. F-term in Honda R & D Co., Ltd. (Reference) 3D046 BB03 CC02 EE01 EE02 HH02 HH07 HH15 HH17 HH22 JJ05 KK12 LL02 LL14 LL23 LL29

Claims (1)

[Claims] In a brake fluid pressure holding device for continuously applying brake fluid pressure in a wheel cylinder even after a brake pedal is depressed and released until a starting drive force is generated in the vehicle itself, a case where no start drive force is generated. Even if the vehicle speed has increased to a predetermined vehicle speed, the brake fluid pressure holding device releases the brake fluid pressure in the wheel cylinder by the brake fluid pressure holding device.