DE4118461A1 - VEHICLE BRAKING SYSTEM WITH IMPROVED DEVICE FOR INDEPENDENT REGULATING THE BRAKE FORCES ON THE VEHICLE WHEELS - Google Patents

Description

The present invention relates to a vehicle brake system, that with a device for independent control the braking forces on the vehicle wheels are equipped.

A brake system for vehicles according to the state of the art, which is equipped with such a device in Japanese Patent Provisional Publication No. 62-1 49 542 and 62-1 49 543.

That in the preliminary Japanese patent publication No. 62-1 49 542 brake system disclosed includes a shutoff valve between a master cylinder and one Wheel brake cylinder and a pressure increase transmission device with inlet and outlet liquid chambers which by a movable piston are separated. The inlet liquid chamber is with a second fluid pressure source connected via a control valve, and the outlet liquid chamber is connected to the wheel brake cylinder.  

Japanese Patent Provisional No. 62- 1 49 543 brake system disclosed includes a pressure booster to generate a pressure increase depending on one Accumulator pressure and a master cylinder pressure, and a pressure modulator for generating a brake pressure that the Sum of boost pressure and master cylinder pressure is.

A disadvantage of the first brake system is that the brake pressure not reduced under the master cylinder brake pressure can be because the wheel brake cylinder from the master brake cylinder is cut off when the master cylinder pressure, which is generated by depressing the brake pedal, is raised above a predetermined value and then by the pressure increase transmission device is increased.

A disadvantage of the latter braking system is that Driver or user has a strange or strange feeling when operating the brake pedal because the gain the brake pressure by the pressure modulator etc. from one sudden change in master cylinder brake pressure, d. H. a sudden change in brake pedal reaction force is followed.

Accordingly, it is an object of the present invention a new and improved braking system is available to make that feel good when you apply the brake pedal offers.

It is another object of the present invention a new and improved braking system with the one described above  To provide property that one achieve variable brake pressure in another area can.

It is another object of the present invention a new and improved braking system with the one described above To provide property that design restrictions can decrease.

It is another object of the present invention a new and improved braking system with the one described above Property to provide that in various vehicle control systems useful and applicable is.

These and other tasks are performed by a vehicle braking system with an improved device for independent Regulate the braking forces for the vehicle wheels like it is defined in the appended claims. In particular, according to the present invention a new and improved vehicle braking system is available which comprises: a manual operating device to generate a manual actuation, a master brake cylinder for generating a master cylinder pressure depending from the operation of the manual control device, a wheel brake cylinder for generating a braking force in dependence a brake pressure applied to it, a first one Pressure transmission device, which at one end with the master brake cylinder is connected, a second pressure transmission device, connected at one end to the wheel brake cylinder is a shutoff valve device connected to a connection  between the first and second pressure transmission devices is arranged to selectively connect between to enable the master brake cylinder and the wheel brake cylinder or to block a fluid pressure device to generate a predetermined fluid pressure independently from manual operation of the manual control device, a liquid cylinder device for variable Regulating the fluid pressure in the second pressure transmission device depending on the master cylinder pressure and a regulatory pressure applied thereto, where the liquid cylinder device has a first liquid chamber, which is part of the second pressure transmission device, a second fluid chamber that communicates with the fluid pressure source is connected and receives the regulatory pressure, and a movable piston between the first and second Has liquid chambers, a flow control valve device between the fluid pressure source and the fluid cylinder device for variable control of the connection between the liquid pressure source and the second Fluid pressure of the fluid cylinder device and for regulating the regulating pressure in the second liquid chamber, a control device for control operations the shutoff valve device and the flow control valve device depending on the driving condition of the vehicle.

Fig. 1 is a diagram of a vehicle braking system according to one embodiment of the present invention.

FIG. 2 is an illustration of various operating modes of the brake system from FIG. 1.

FIG. 3 is an enlarged view of various variants of area "E" of FIG. 2.

FIG. 4 is a view similar to FIG. 1 and shows another embodiment of the present invention.

As shown in Fig. 1, a vehicle brake system of the type is used to achieve an ideal distribution of the braking force between the front and rear wheels or between the left and right wheels.

The vehicle brake system consists of a master brake cylinder 2 for generating a master brake cylinder pressure as a function of the depression of a brake pedal 1 , a wheel brake cylinder 3 which is provided for each wheel (not shown) in order to transmit a braking force as a function of a brake pressure to the vehicle wheel, a closure valve 6 , which is arranged on a connection between a master cylinder pressure passage 4 in connection with the master brake cylinder 2 and a brake pressure passage 5 in connection with the wheel brake cylinder 3 , a liquid cylinder 7 with a first liquid chamber 7 a, which forms part of the brake pressure passage 5 , and a second Liquid chamber 7 b, which is connected via a control pressure passage 8 and a flow control valve 9 in connection with a hydraulic pump 11 , a memory 12 for generating a constant liquid pressure regardless of a braking operation, ie regardless of the depression de s brake pedal 1 , and a control unit 13 for controlling the operation of the shutoff valve 6 and the flow control valve 9 . The closure valve 6 is a normally open solenoid valve which is actuated by a magnet 6 a, and the flow control valve 9 is a solenoid valve which is actuated by a magnet 9 a.

The closure valve 6 , the liquid cylinder 7 and the flow control valve 9 are provided for each vehicle wheel, but for the sake of brevity only one is shown.

The liquid cylinder 7 comprises the first cylindrical liquid chamber 7 a with a smaller diameter, the second cylindrical liquid chamber 7 b with a larger diameter, a stepped piston 7 c, which is movable in the first and second liquid chambers 7 a and 7 b, and a pair of centering springs 7 d and 7 e, which are installed in the first and second liquid chambers 7 a and 7 b, respectively, in order to force the piston 7 c into its centered position.

The hydraulic pump 11 and the accumulator 12 are connected to one another via a check valve 14 , which only allows the flow from the hydraulic pump 11 to the accumulator 12 in one direction.

The control unit 13 receives signals from a steering angle sensor 15 , a pitch rate sensor 16 , a lateral acceleration sensor 17 , a longitudinal acceleration sensor 18 , a vehicle speed sensor 19 , a vehicle wheel speed sensor 20 , a master cylinder pressure sensor 21 and a brake pressure sensor 22 and is suitable to set a target brake pressure based on a predetermined one To determine target brake pressure characteristic and a vehicle brake state or a vehicle driving state, as is known from the signals from the above sensors, and to supply signals to the magnets 6 a of the closure valve 6 and the magnets 9 a of the flow control valve 9 , so that the difference between the target brake pressure and the actual brake pressure is eliminated.

The operation is described below.

(A) Normal braking

During normal braking, the control unit 13 generates a signal to cause the closure valve 6 to open by switching off the magnet 6 a, and a signal to maintain a predetermined reference control pressure in the passage of the second liquid chamber 7 b of the liquid cylinder 7 through the flow control valve to effect by switching the magnet 9 a on and off.

Thus, when the master cylinder 2 generates a master cylinder pressure depending on a depression of the brake pedal 1 , the master cylinder pressure is supplied to the wheel brake cylinder 3 through the pressure passages 4 and 5 , whereby the vehicle wheel is subjected to a braking force resulting from the master cylinder pressure (flow I in Fig. 2) .

(B) Brake pressure increase

Depending on the type of signal supplied from the control unit to the shutoff valve 6 , a plurality of boost modes are achieved in which the brake pressure is boosted via the master cylinder pressure, namely a boost mode with a sudden change in the brake pedal reaction characteristic (flow II-1 in FIG. 2) , a boost mode of the type with a gradual change in the brake pedal response characteristic (flow II-2) and a boost mode of the type with substantially no change in the brake pedal response characteristic (flow II-3).

In the case of the boost mode of the type that is accompanied by a sudden change in the brake pedal characteristics (flow II-1), the control unit 13 generates a signal that causes the shutter valve 6 to open by turning off the magnet 6 a, and a signal , causes that the flow control valve 9 as the reference control pressure in the passage 8 and in the second liquid chamber 7 b of the fluid cylinder 7 by controlling the switching on and off of the magnets 9 holds a fluid pressure higher a.

Thus, when the brake pedal 1 is depressed, the master cylinder 2 generates a master cylinder pressure depending on the depression of the brake pedal 1 . On the other hand, the second liquid chamber 7 b of the liquid cylinder 7 is supplied with a liquid pressure 7 higher than the reference control pressure. As a result, the piston 7 c is moved in the direction in which a volume reduction of the first liquid chamber 7 b of the liquid cylinder is caused, as a result of which the brake pressure in the passage 5 and in the master brake cylinder is increased or increased. An increased braking force is then applied to the vehicle wheel connected to it. On the other hand, since the shut-off valve is kept open in the case of the flow II-1 in Fig. 2, the pressure within the master cylinder 2 is also increased or increased, whereby the resistance of the brake pedal is increased.

In the case of the boost mode, which is accompanied by a slight change in the brake pedal response characteristic (flow II-2 in Fig. 2), the control unit 13 generates a signal that causes the shutter valve 6 to open and close repeatedly and a signal that causes the flow control valve 9 holds a liquid pressure higher than the reference control pressure in the passage 8 and the second liquid chamber 7 b of the liquid cylinder 7 .

Thus, as shown in flow II-2 in Fig. 2, while the C-point pressure characteristic or brake pressure characteristic is similar to that in the case of the boost mode with a sudden change in the brake pedal response characteristic, the B-point pressure characteristic or master cylinder pressure characteristic shows a gradual or gradual change due to the effect of repeatedly opening and closing the shutoff valve 6 , and this gradual pressure change is dampened and weakened by the liquid in the master cylinder 2 , causing the A-point pressure characteristic or brake pedal response characteristic to show a smooth change and therefore it makes it possible to get a good feeling when operating the brake pedal 1 .

As shown in Fig. 3, which shows different variants of the area "E" of Fig. 2, the pressure change pattern of the master cylinder can be changed in different ways by changing the turn-off and turn-on times for the magnet 6 a of the closure valve 6 .

In the case of the boost mode, which is accompanied by substantially no change in the brake pedal response characteristic, the control unit 13 generates a signal that causes the shutoff valve 6 to close and a signal that causes the flow control valve 9 to have a fluid pressure higher than the reference control pressure in the passage 8 and the second liquid chamber 7 b of the liquid cylinder 7 holds.

Accordingly, as shown in flow II-3 of FIG. 2, the C-point pressure characteristic or brake pressure characteristic is the same as that in the case of the boost mode with a sudden change in the brake pedal response characteristic. However, the B-point pressure characteristic or master cylinder pressure characteristic is not influenced at all by the increased brake pressure due to the closing of the master cylinder pressure control valve 6 , and therefore no change in the brake pedal response characteristic is caused.

(C) reducing the brake pressure

There are three types of reduction modes by which the brake pressure is reduced below the master cylinder pressure, namely a reduction mode with a sudden change in the brake pedal response characteristic (flow III-1 in FIG. 2), a reduction mode with a gradual change in the brake pedal response characteristic (flow III -2 in Fig. 2) and a reduction mode of the type with essentially no change in the brake pedal response characteristic.

In the case of the reduction mode of the type accompanied by a sudden change in the brake pedal characteristic, the control unit 13 generates a signal that causes the shut-off valve 6 to open and a signal that causes the flow control valve 9 to have a fluid pressure lower than the reference control pressure in the passage 8 and the second liquid chamber 7 b of the liquid cylinder 7 holds.

Accordingly, since a pressure lower than the reference control pressure in the second fluid chamber 7 b of the liquid cylinder 7 prevails during a brake application, the piston 7 is c in the direction moves, which causes the first fluid chamber 7 a its volume increases. As a result, the brake pressure is reduced by the effect of the volume increase of the first liquid chamber 7 a of the liquid cylinder, and therefore the lower brake pressure is applied to the wheel brake cylinder 3 and generates a reduced braking force on the wheel. That the closure valve 6 is kept open, the pressure in the master cylinder 2 is reduced by the effect of the decrease in the brake pressure, causing a change in the brake pedal response characteristic.

In the case of the reduction mode accompanied by a slight change in the brake pedal response characteristic, the control unit 13 generates a signal that causes the shutoff valve 6 to open and close repeatedly and a signal that causes the flow control valve 9 to have a fluid pressure lower than the reference control pressure in the passage 8 and the second liquid chamber 7 b of the liquid cylinder 7 holds.

Thus, as shown in flow II-2 in Fig. 2, the C-point pressure characteristic or brake pressure characteristic is similar to that in the case of the reduction mode with a sudden change in the brake pedal response characteristic. However, the B-point pressure characteristic or master cylinder pressure characteristic shows a gradual or gradual change due to the effect of repeatedly opening and closing the shutter valve 6 . This pressure change is dampened and attenuated by the liquid in the master cylinder 2 , causing the A-point pressure characteristic or brake pedal reaction characteristic to show a smooth change and therefore make it possible to get a good feeling when the brake pedal 1 is operated .

In the case of the boost mode, which is accompanied by substantially no change in the brake pedal response characteristic, as shown in flow III-3 of FIG. 2, the control unit 13 generates a signal that causes the shutoff valve 6 to close and a signal that causes the flow control valve 9 to hold a liquid pressure lower than the reference control pressure in the passage 8 and the second liquid chamber 7 b of the liquid cylinder 7 .

As a result, the C-point pressure characteristic or brake pressure characteristic is the same as that in the case of the boost mode with a sudden change in the brake pedal response characteristic. However, the B-point pressure characteristic or master cylinder pressure characteristic is not affected at all by the brake pressure due to the closing of the master cylinder pressure control valve 6 , and therefore no change in the brake pedal reaction characteristic is caused.

(D) Apply a braking force when the brake pedal is not is operated

When it is desired to apply a braking force to each vehicle wheel without operating the brake pedal 1 , the control unit 13 is activated to generate a signal to cause the shutter valve 6 to close, and then to generate a signal to cause the Flow control valve 9 maintains a certain boost pressure in the passage 8 and the second liquid chamber 7 b of the liquid cylinder 7 , the boost pressure being higher than the pressure in the passage 5 and in the master brake cylinder 2 .

Accordingly, the working fluid is trapped in the brake passage 5 by the closing of the shutoff valve, and the piston 7 c of the fluid cylinder 7 is moved by the boost pressure in the direction in which it causes a volume reduction of the first fluid chamber 7 a proportional to the boost pressure.

As a result, a braking force is applied to each vehicle wheel depending on the boost pressure or a resultant change in the volume of the first liquid chamber 7 a of the liquid cylinder 7 . Thus, by regulating the boost pressure to be applied to the fluid cylinder by regulating the circuit by monitoring the resulting brake pressure Pw by means of the brake pressure sensor 22, a desired braking force can be applied to the vehicle wheel without the brake pedal 1 being actuated.

Next, an example of braking force control, when the brake pedal is operated.

Regulation of an ideal braking force distribution between Front and rear wheels

The brake pressures to be applied to the front and rear wheels become relative to a master cylinder brake pressure based on a longitudinal vehicle acceleration condition or front or rear load condition, the known from the longitudinal acceleration XG etc. increased or decreased. This creates an ideal distribution of braking forces between the front and rear wheels achieved without blocking the rear wheels at one earlier stage of braking is caused.

Regulation of the ideal braking force distribution between the left and right wheels. The right and left wheel brake cylinders brake pressures to be supplied are relative to one Master cylinder pressure based on a vehicle steering condition,  that of a lateral acceleration YG, one Pitch rate, a steering angle R, a vehicle speed V (or a loading condition of the left and right Wheels) etc. is known, and a predetermined, ideal Brake force distribution characteristic between the left and right wheels enlarged and reduced. This will make one ideal braking force distribution between the left and right Get wheels without blocking one of the left or cause right wheels at an earlier braking stage.

Anti-slip regulation

A slip rate is based on one for each wheel Vehicle speed determined from an integrated Value of a longitudinal vehicle acceleration XG and one Vehicle wheel speed VW is calculated, and a Brake pressure is controlled in a control loop so that the Hatch rate becomes an ideal value. This can cause blocking a wheel in the event of braking on a road with a Surface with a low µ value or in the case of a sudden, violent braking can be prevented it becomes possible to have a reduced braking distance and to achieve braking stability.

Then an example of braking force control in the event that the brake pedal is not operated, given.

Steering characteristic control

The brake pressure is regulated so that a current steering characteristic while driving based on the  lateral acceleration YG, the pitch rate, the steering angle R and vehicle speed V (or loading condition for the left and right wheels) etc. becomes neutral steering. This makes it possible a strong understeer or oversteer while steering avoid.

Stability control when driving straight ahead

If there is a change in lateral acceleration or the pitch rate of the vehicle due to a disturbance such as a convex or concave road surface, cross wind etc. occurs, this is immediately determined and by the Control of brake pressure and braking force corrected. Thereby straight running stability can be obtained without that it is affected by a disturbance.

Pitch rate control

First, a difference between the pitch rate known from the pitch rate sensor 16 and the target pitch rate known from the vehicle speed V and the steering angle R is determined, and the braking force is controlled by controlling the braking pressure so that the above difference becomes zero. This makes it possible to obtain an optimum pitch rate characteristic when driving straight ahead and when steering.

From the above it is clear that the brake system according to the invention is equipped with a shut-off valve 6 which is installed on the connection between the master cylinder pressure passage 4 and the brake pressure passage 5 and which is opened and closed in response to external commands, thereby making it possible to create a strange one or to avoid the unfamiliar feeling that is otherwise generated when the brake pedal 1 is operated at the time of increasing or decreasing the brake pressure, and at the same time to vary the brake pressure in a wider, regulated range, and therefore the brake system described above becomes possible in various ways Use brake controls.

It is also clear that in the invention Braking system never occurs a case in which the braking force is decreased during an increase in brake pressure and is increased during a decrease in brake pressure.

It is also clear that the brake system according to the invention makes it possible to achieve a good feeling when the brake pedal 1 is actuated by a control which causes the closure valve 6 to open and close repeatedly.

It is also clear that in the event of a pressure reduction is possible during the application of the brake Reduce brake pressure below the master cylinder brake pressure which makes it possible to control the adjustable range of the Increase brake pressure and thereby the design restrictions of the braking system.

Fig. 4 shows a modified embodiment of the invention. In this embodiment, the hydraulic pump 11 is, for example, a power control pump and suitable for general uses. In particular, the brake system is also provided with a flow dividing valve 30 , a solenoid-operated shut-off valve 31 , a pressure switch 32 and a reservoir 33 .

In operation, when the pressure within the accumulator 21 drops below a predetermined value, the pressure switch is switched on, as a result of which the closure valve 6 is closed. As a result, the liquid flow to the reservoir 33 is stopped and the liquid supply from the hydraulic pump 11 is directed into the reservoir 12 , which causes the predetermined fluid pressure to be stored in the reservoir 12 .

Except for the above, this embodiment is substantially similar to the previous embodiment of FIG. 1 and can produce the substantially same effects.

Claims (14)

1. Vehicle braking system which comprises:
a manual actuation device ( 1 ) for generating a manual actuation,
a master brake cylinder ( 2 ) for generating a master brake cylinder pressure as a function of the actuation of the manual actuation device,
a wheel brake cylinder ( 3 ) for generating a braking force as a function of a braking pressure applied to it,
characterized in that it also includes:
a first pressure transmission device ( 4 ) which is connected at one end to the master brake cylinder,
a second pressure transmission device ( 5 ) which is connected at one end to the wheel brake cylinder,
a closure valve device ( 6 ) which is arranged on a connection between the first and second pressure transmission device in order to selectively enable or block a connection between the master brake cylinder and the wheel brake cylinder,
a liquid pressure device ( 12 ) for generating a predetermined liquid pressure independently of the manual actuation of the manual actuation device,
a fluid cylinder device ( 7 ) for variably regulating the fluid pressure in the second pressure transmission device as a function of the master brake cylinder pressure and a control pressure applied thereto, the fluid cylinder device comprising a first fluid chamber ( 7 a), which is part of the second pressure transmission apparatus, a second fluid chamber ( 7 b) , which is connected to the liquid pressure source and receives the control pressure, and has a movable piston ( 7 c) between the first and second liquid chambers,
a flow control valve device ( 9 ) between the liquid pressure source and the liquid cylinder device for variably controlling the connection between the liquid pressure source and the second liquid pressure of the liquid cylinder device and for regulating the control pressure in the second liquid chamber, and
a control device ( 13 ) for control operations of the shutter valve device and the flow control valve device depending on the driving condition of the vehicle. 2. A vehicle braking system according to claim 1, characterized in that the closure valve means (6) and the Flußregelungsventilvorrichtung (9) solenoid-actuated (6 a, 9 a) valve devices. 3. Vehicle braking system according to claim 2, characterized in that the first liquid chamber ( 7 a) of the liquid cylinder device ( 7 ) is smaller in diameter than the second liquid chamber ( 7 b) and that the movable piston ( 7 c) has a stepped shape and in the first and second liquid chambers is movable. 4. A vehicle brake system according to claim 3, characterized in that the control device ( 13 ) comprises a device for generating a signal for causing the closure valve device to open and a signal for causing the predetermined control valve pressure to be held by the flow control valve device in the second liquid chamber of the liquid cylinder device. 5. A vehicle braking system according to claim 3, characterized in that the control device ( 13 ) means for generating a signal for causing the closure valve device to open and a signal for causing a pressure higher than the predetermined reference control pressure by the flow control valve device in the second liquid chamber of the Fluid cylinder device includes. 6. Vehicle braking system according to claim 3, characterized in that the control device ( 13 ) means for generating a signal for causing the opening and closing of the shutoff valve device repeatedly and a signal for causing a pressure higher than the predetermined reference control pressure by the flow control valve device in the second liquid chamber of the liquid cylinder device. 7. The vehicle brake system according to claim 3, characterized in that the control device ( 13 ) means for generating a signal for causing the opening and closing of the shutter valve device repeatedly and a signal for causing a pressure lower than the predetermined reference control pressure by the flow control valve device in the second liquid chamber of the liquid cylinder device. 8. A vehicle brake system according to claim 3, characterized in that the control device ( 13 ) means for generating a signal for causing the shutoff valve device to repeatedly open and close and a signal for causing the flow control valve device to hold a predetermined reference control pressure in the second liquid chamber of the liquid cylinder device includes. 9. Vehicle braking system according to claim 3, characterized in that the control device ( 13 ) means for generating a signal for causing the closure valve device to close and a signal for causing a pressure higher than the predetermined reference control pressure by the flow control valve device in the second liquid chamber of the Fluid cylinder device includes. 10. The vehicle brake system according to claim 3, characterized in that the control device ( 13 ) means for generating a signal for causing the closure valve device to close and a signal for causing a pressure lower than the predetermined reference control pressure by the flow control valve device in the second liquid chamber of the Fluid cylinder device includes. 11. The vehicle brake system according to claim 3, characterized in that the control device has a steering angle sensor ( 15 ), a pitch rate sensor ( 16 ), a lateral acceleration sensor ( 17 ), a vehicle speed sensor ( 19 ) and a brake pressure sensor ( 21 ) for determining the vehicle driving state. 12. A vehicle brake system according to claim 1, characterized in that the pressure source device ( 12 ) comprises a hydraulic pump ( 11 ), a reservoir ( 33 ) and a check valve ( 14 ) to allow fluid flow in one direction from the pump to the reservoir . 13. The vehicle braking system according to claim 12, characterized in that the pressure source device further comprises: a flow dividing valve ( 30 ) for directing a discharge of the pump to another location in addition to the accumulator, a pressure sensor for detecting the pressure in the accumulator, a liquid passage which is extending between the flow dividing valve and the check valve, a reservoir ( 33 ) and a shutoff valve ( 31 ) for draining the liquid passage into the reservoir when the pressure sensor detects that the pressure in the reservoir is lower than a predetermined value. 14. Vehicle braking system according to claim 1, characterized in that the manual actuation device ( 1 ) comprises a brake pedal.