JP2001213294A - Vehicular hydraulic braking device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a brake pedal stroke and further improve a pedal feel and responsiveness of a hydraulic braking device at a rapid pressurization or a low temperature, in a device whose braking hydraulic pressure is generated by a power-driven pump when an electric control system thereof is normal and a hydraulic pressure is supplied to enhance responsiveness also from a fail-safe master cylinder in a rapid pressurization. SOLUTION: An alternative path 19 is provided for communicating the master cylinder 1 and wheel cylinders 2A, 2B bypassing an on-off valve 3 which is usually closed during braking, and a check valve 20 and a shut-off valve 21 are provided in the alternative path 19, wherein the shut-off valve 21 is opened at a rapid pressurization or a low temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention provides a fuel-safe master cylinder in addition to a power-driven pump serving as a main hydraulic pressure source. For example, at the time of sudden pressurization (sudden braking), at a low temperature where the brake fluid viscosity increases, or when the pump performance is reduced due to a voltage drop or the like, the hydraulic pressure is also supplied from the master cylinder in order to increase responsiveness. The present invention relates to an improvement plan of a vehicle hydraulic brake device.

[0002]

2. Description of the Related Art There has been an increasing number of hydraulic brake devices for vehicles that electrically control the effectiveness of the brake in order to control the advanced behavior of the vehicle. As an example of such an apparatus, for example, Japanese Patent Publication No. 2590825 includes a hydraulic pressure source constituted by a pump and an accumulator separately from a master cylinder that generates hydraulic pressure by pedal operation. Regardless, a brake device capable of supplying hydraulic pressure to the wheel cylinder is disclosed, but since this device includes an accumulator that takes up space, the brake device is poorly mountable in an engine room.

Further, an apparatus for generating a replenishing brake fluid only by a pump when the wheel cylinder pressure is increased or decreased by electronic control is disclosed in JP-A-9-20229 or JP-A-10-67.
Although these devices have been proposed in Japanese Patent Publication No. 311 or the like, when the communication passage between the master cylinder and the wheel cylinder is blocked, the pump must cover the entire amount of brake fluid required for braking. A large capacity pump is required. In addition, there is a problem of delay in boosting pressure during sudden pressurization, etc.
The braking distance also increases.

[0004] Therefore, there has been proposed a brake device which addresses the above-mentioned problems.

FIG. 3 is a basic circuit diagram of the device. As shown in the figure, the master cylinder 1 and the wheel cylinder 2
The electromagnetically driven on-off valve 3 and the stroke simulator 4 are inserted in the communication passage between A and 2B (the symbols A and B are used for convenience and may be omitted in the following description). A control valve for controlling the wheel cylinder pressure based on a command from an electronic control unit (not shown) (the on-off valves 5A and 5B for pressurization and the on-off valves 6A and 6B for pressure reduction);
Open / close valve 9 for a return passage from the discharge port of a pump 7 (the electric hydraulic pump in the figure) to the suction side connected to a reservoir 8
A bypass passage 10 for communicating the suction side of the pump 7 with the master cylinder 1, an on-off valve 11 for opening and closing the bypass passage 10, and a check valve 12 for preventing a liquid flow from the bypass passage 10 to the reservoir 8. ing. Although the on-off valves 5 and 6 are provided to enable antilock control, they are not essential elements of the present invention.

Reference numerals 13A and 13B denote pressure sensors for detecting hydraulic pressure, 14 is a relief valve for preventing excessive pressure increase, 15 is a throttle for silencing, and 16 is a silencer. Although the relief valve 14, throttle 15 and silencer 16 are newly added to the previously proposed circuit, these are only preferred elements.

Here, a back pressure chamber 4b (4a is a main chamber) of the stroke simulator 4 is connected to a reservoir 8 to keep the chamber in a wet state.

[0008]

In the brake device shown in FIG. 3, the brake fluid pressure during normal operation (when the electric control system is normal) is generated by the pump 7, and the brake fluid viscosity increases at the time of rapid pressurization or at a low temperature. When the supply of the hydraulic pressure is not sufficient with the pump 7 alone, the hydraulic pressure is also supplied from the master cylinder 1 to the wheel cylinder 2.

[0009] The hydraulic pressure supply from the master cylinder
However, if this method is adopted, the pulsation caused by the operation of the pump or the intermittent opening and closing of the on-off valve 3 is transmitted to the brake pedal 17, and the pedal feel deteriorates. Also,
When the on-off valve 3 is kept open, kickback of the brake pedal occurs when the hydraulic pressure on the wheel cylinder exceeds the master cylinder pressure (the hydraulic pressure generated in the master cylinder).

In the apparatus shown in FIG. 3, a bypass 10 having an on-off valve 11 is provided to eliminate the problem and the hydraulic pressure is supplied from the master cylinder 1 via the pump 7, but the on-off valve 11 is opened. At the time of sudden pressurization or the like, the check valve 12 closes and the pump 7 stops sucking the liquid from the reservoir 8, so that the amount of replenishing liquid from the master cylinder increases and the pedal stroke (stroke of the brake pedal 17) decreases. Is larger than at the time of gentle pressurization with the closed.

In addition, since the pump intermittently pumps the liquid from the master cylinder, the pulsation is transmitted to the brake pedal. Further, when the throttle 15 is provided on the discharge side of the pump 7 as a measure against noise, the effect of the rapid pressurization is weakened by the influence of the throttle.

SUMMARY OF THE INVENTION It is an object of the present invention to solve such a problem and increase the responsiveness of the hydraulic brake device without deteriorating the pedal feel.

[0013]

In order to solve the above-mentioned problems, according to the present invention, when the electric control system of the apparatus is normal, the communication passage between the master cylinder and the wheel cylinder is closed by an on-off valve and the pump is moved from the wheel cylinder. A detour is provided for the vehicle hydraulic brake device that supplies the brake fluid pressure to the master cylinder and the wheel cylinder by bypassing the opening / closing valve, and the detour includes a fluid flow from the master cylinder to the wheel cylinder. A check valve or a relief valve that allows only the pressure and a shutoff valve are provided.

When the throttle 15 is provided on the discharge side of the pump as shown in FIG. 3, it is preferable to connect the bypass to a circuit closer to the wheel cylinder than the throttle.

[0015]

According to the brake device of the present invention, the brake from the master cylinder to the wheel cylinder is opened by opening the bypass valve of the detour when the supply of hydraulic pressure is insufficient with only the pump, such as during rapid pressurization or at low temperatures. Since the liquid is supplied and the entire amount of the liquid from the pump is also supplied to the wheel cylinder, the pressure rise delay is reduced.

When the wheel cylinder pressure exceeds the master cylinder pressure, the check valve in the bypass is closed, so there is no need to open and close the shutoff valve, and the pedal feel does not deteriorate. In addition, closing the check valve in the detour prevents kickback of the pedal when the wheel cylinder pressure rises.Furthermore, when the check valve closes, liquid supply from the master cylinder stops, so the pedal stroke is small. Can be suppressed.

If a relief valve that opens when a certain differential pressure is generated (which can also be considered as a type of check valve) is used instead of the check valve, the pulsation caused by the pump operation is not easily transmitted, and the pedal feel is reduced. It gets even better.

In a device in which a restrictor is provided in a discharge circuit of a pump, when the replenishing liquid from the master cylinder is introduced into a circuit between the restrictor and the pump, the effect of improving the response at the time of rapid pressurization is weakened by the influence of the restrictor. , Fluid supply from the master cylinder
Preferably, it is directed to the circuit between the throttle and the wheel cylinder.

[0019]

FIG. 1 shows an embodiment of a hydraulic brake device for a vehicle according to the present invention. This figure shows one of the hydraulic circuits normally provided in two separate systems. The wheel cylinders 2A and 2B include front left and right wheels, rear left and right wheels, left front wheel and right rear wheel, right front wheel and left rear wheel The wheel belongs to one of the wheel brakes.

The master cylinder 1 is provided to enable braking by the pedaling force when the electric control system of the device fails. In order to prevent a decrease in the braking force due to the braking by the pedaling force, the master cylinder 1 The operation force of 17 is proportionally amplified by a vacuum booster 18 to generate a hydraulic pressure.

The brake device shown in FIG. 1 is a modification of the above-described device shown in FIG. 3, and therefore, the same portions except for the changed portions are denoted by the same reference numerals and will not be described again.

On the suction side and the discharge side of the pump 7, a check valve for preventing the backflow of the brake fluid to the reservoir 8 and a check valve for preventing the backflow of the brake fluid from the wheel cylinder 2 to the pump 7 are provided. However, these check valves are not shown because they are included in the pump 7.

The brake device shown in FIG. 1 is provided with a bypass 19 for connecting the master cylinder 1 and the wheel cylinder 2 to bypass the valve 3 instead of the bypass 10 and the valve 11 of the device shown in FIG. Further, the bypass 19 is provided with a check valve 20 and a shut-off valve (electromagnetically driven on-off valve) 21 for allowing only the liquid flow from the master cylinder 1 to the wheel cylinder 2, which is shown in FIG. Different from device.

In the brake device having the above structure, when the brake pedal 17 is depressed, the on-off valve 3 is closed by a signal from a brake switch (not shown) and / or a pressure sensor 13A, and the pump 7 is rotated. In this way, by adjusting the amount of liquid supplied from the pump 7 to the wheel cylinder 2, an arbitrary amount of pressure increase can be set, and vehicle braking can be performed based on the driver's intention.
When the pressure is increased by operating the wheel cylinder 2, first, the pump 7 is operated at a high speed with the open / close valve 9 of the return passage closed at the start of braking. At this time, the on-off valve 3 in the communication passage from the master cylinder is closed, and the entire amount of the brake fluid pumped by the pump 7 is supplied to the wheel cylinder 2 to increase the brake fluid pressure. Accordingly, when the output of the pressure sensor 13B on the wheel cylinder side reaches a predetermined pressure, the rotation speed of the pump 7 is reduced or stopped, and in some cases, the on-off valve 9 is opened.

Although the hydraulic pressure is generated in the master cylinder 1 in proportion to the operating force of the driver, the brake fluid is not supplied from the master cylinder via the on-off valve 3 because the on-off valve 3 is closed. . As a result, the driver is separated from the pulsation generated by the pump 7, and a good pedal feel can be obtained. Further, when a sudden increase in brake pressure is required due to an operation delay of the pump 7 or the like at the time of sudden braking or low temperature, the shut-off valve 21 of the bypass 19 is opened, and the brake fluid pressure is supplied from the master cylinder 1 to the wheel cylinder 2. To prevent delay in boosting. At the end of braking, the operation of the pump 7 is terminated, and the hydraulic pressure of the wheel cylinder 2 is returned to the reservoir 8 by opening the on-off valve 9. The on-off valves 5 and 6 in the figure are arranged for performing antilock control. At this time, if necessary, the on-off valve 6 may be opened to return the fluid pressure to the reservoir sooner. In the low pressure range, the on-off valve 3 may be opened to return a part of the discharged liquid to the master cylinder 1 side.

The amount of liquid supplied to the wheel cylinder 2 is determined, for example, by detecting the operating force of a brake pedal by a driver and the hydraulic pressure of the wheel cylinder, adjusting the rotation speed of the pump 7, adjusting the torque of the pump drive motor, or adjusting the on-off valve 6. , 9 can be adjusted in such a way that the wheel cylinder pressure is set to a value corresponding to the operating force. Although only one of the two hydraulic circuits is shown in the figure, it is also possible to obtain different hydraulic pressure levels for each system by changing the degree of pressure adjustment of the on-off valves 9 and 6 for each system.

Whether the pump discharge amount is insufficient is determined by whether the change rate of the operating force by the driver or the master cylinder pressure exceeds a predetermined value (in the case of sudden braking, the change rate is large), and the like. Can be determined by comparing the pressure sensors 13A and 13B. If the shut-off valve 21 is opened when it is determined that the pump discharge amount is insufficient (this determination is, of course, made by an electronic control unit (not shown)), high responsiveness can be obtained even at the time of sudden braking or low temperature. Demonstrate. Generally, the pressure sensors 13A,
3B, the shut-off valve 21 is closed when the pressure on the wheel cylinder side is sufficiently increased. However, since the check valve 20 is provided in the detour 19, even when the shut-off valve 21 is kept open, the kickback of the brake pedal is performed. Does not happen. Further, when the check valve 20 is closed due to an increase in the wheel cylinder pressure, the liquid supply from the master cylinder is stopped, so that the brake pedal 17 does not become unnecessarily large, and a good pedal feel is maintained. Rapid pressurization becomes possible.

The illustrated brake device has on-off valves 5, 6, 9 for controlling the pressure increase and decrease of the wheel cylinder pressure, and pressure sensors 13A, 13B for detecting the master cylinder pressure and the hydraulic pressure of the discharge side circuit of the pump, respectively. In addition, by providing a brake switch, an electronic control unit, and a wheel speed sensor (none of which are shown), 1) the hydraulic pressure supplied from the pump to the wheel cylinder is controlled by the operation amount of the brake pedal ( 2) anti-lock control when the wheels show a tendency to lock, 3) pressurizing the brake system for the purpose of deceleration and vehicle body posture control without brake pedal operation 4) Regenerative coordination that increases the regenerative efficiency by reducing the hydraulic braking force according to the regenerative braking used in electric vehicles, etc. Brake control, 5) Brake assist control that generates a braking force that is greater than the braking force in proportion to the driver's brake pedal operation amount during sudden braking, etc., 6) EBD control that optimally distributes the braking force relationship between the front and rear wheels, etc. A variety of fluid pressure controls can be performed.

The check valve 20 shown in FIG. 1 may be replaced with a relief valve 22 shown in FIG. This relief valve 22
Does not open until the hydraulic pressure difference between the master cylinder side and the pump discharge side exceeds a predetermined value (for example, about 10 bar). Pulsation is difficult to transmit to the brake pedal. Therefore, when a relief valve is used, the pedal feel at the time of sudden pressurization when the shut-off valve 21 opens is further improved.

In some cases, it is conceivable to set the relief valve opening differential pressure relatively high (for example, 20 bar or more) and omit the shutoff valve 21.

Also, as shown in FIG. 1, a throttle 15 which attenuates pulsation in the discharge circuit of the pump to reduce noise due to pulsation.
It is preferable to connect the bypass 19 to the circuit on the wheel cylinder side rather than the throttle 15 as shown in the figure, so that the effect of the throttle 15 is eliminated and the effect of improving the response at the time of rapid pressurization is maximized. Drawn to the limit.

Although the operation of the on-off valve 3 has been described as being performed by a signal from the brake switch and / or the pressure sensor 13A, the operation amount of the brake pedal is detected instead of or in addition to these. The signal of the stroke sensor can also be used.

[0033]

As described above, the brake device of the present invention uses the check valve to supply the brake fluid to be supplied from the master cylinder to the wheel cylinder at the time of sudden pressurization when the supply of the hydraulic pressure is insufficient with the pump alone. Since it is introduced to the discharge side of the pump through a detour with a shut-off valve, entry of the brake pedal during sudden pressurization is reduced, kickback of the pedal due to reverse flow of hydraulic pressure, pedal vibration due to intermittent opening and closing of the shut-off valve And a good pedal feel can be obtained.

Also, in the case of sudden pressurization, etc., the entire amount of the liquid discharged from the pump is effectively used, and the replenishing liquid from the master cylinder is added thereto. The performance and reliability of a small hydraulic brake device that does not include an accumulator and has a reduced pump capacity are further improved.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a hydraulic brake device according to an embodiment.

FIG. 2 is a diagram showing an example in which a check valve in a bypass is replaced with a relief valve.

FIG. 3 is a circuit diagram of a hydraulic brake device to be improved.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Master cylinder 2A, 2B Wheel cylinder 3 On-off valve 4 Stroke simulator 5A, 5B On-off valve 6A, 6B On-off valve 7 Pump 8 Reservoir 9 On-off valve 12 Check valve 13A, 13B Pressure sensor 14 Relief valve 15 Restrictor 16 Silencer 17 Brake Pedal 18 Vacuum booster 19 Detour 20 Check valve 21 Shutoff valve 22 Relief valve

Continued on the front page F-term (reference)

Claims (2)

[Claims] A master cylinder for generating a hydraulic pressure corresponding to a brake operation force, a power-driven pump having an intake port connected to a reservoir, and an on-off valve provided in a communication passage between the master cylinder and the wheel cylinder. When the electric control system of the apparatus is normal, the on-off valve is closed to supply brake fluid pressure from the pump to the wheel cylinder. In a vehicle hydraulic brake device, the master cylinder and the wheel cylinder are communicated by bypassing the on-off valve. A hydraulic brake device for a vehicle, comprising: a detour, a check valve or a relief valve that allows only a liquid flow from the master cylinder to the wheel cylinder, and a shutoff valve. 2. A hydraulic brake device for a vehicle according to claim 1, wherein a throttle is inserted into a discharge side circuit of said pump, and one end of said bypass circuit is connected to a circuit closer to a wheel cylinder than said throttle.