JP2009274685A - Electric booster hydraulic brake device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent abrupt braking from occurring due to double boosting during failsafe in which a value obtained by multiplying a detected master cylinder hydraulic pressure value and a predetermined boosting ratio is set to wheel hydraulic pressure if the boosting fails during the braking. <P>SOLUTION: If the boosting fails at t3 during the braking in which a brake depressing force is kept at 20 N and master cylinder hydraulic pressure Pm=5 MPa is set to wheel cylinder hydraulic pressure Pw=5 MPa, after the failure time t3, a failsafe operation is performed to hold the wheel cylinder hydraulic pressure Pw at 5 MPa at the failure t3. Since the failsafe operation at the time of failure during the braking does not excessively increase the wheel cylinder hydraulic pressure Pw by the double boosting, the possibility of abrupt braking with the sense of incongruity can be eliminated. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electric boost type hydraulic brake device that raises a brake hydraulic pressure under a boost by stroke of a brake hydraulic pressure output member in response to a brake operation under the assistance of an electric motor.

As such an electric boost type hydraulic brake device, various devices have been conventionally proposed. For example, as described in Patent Document 1,
A brake fluid pressure generating member (primary piston) that is stroked by an electric motor according to a brake operation and generates a predetermined brake fluid pressure in the fluid pressure chamber;
Corresponding to the brake operation, when the brake fluid pressure generating means fails, the brake fluid pressure generating means is mechanically stroked to generate the brake operation force corresponding fluid pressure in the same fluid pressure chamber as above. A hydraulic pressure generating member (input rod),
There is known an electric boost type hydraulic brake device in which the predetermined brake hydraulic pressure or the hydraulic pressure corresponding to the brake operation force is directed to a wheel braking unit (wheel cylinder) as a wheel cylinder hydraulic pressure.

  In such an electric boost type hydraulic brake device, it is directly linked to the brake operation in the event of a failure of the above-described electric motor itself or a brake hydraulic pressure generating means that cannot obtain a boosting action due to a failure of its control system. The brake operating force corresponding hydraulic pressure generating member (input rod) striking and striking against the brake hydraulic pressure generating member (primary piston) pushes the brake hydraulic pressure generating member (primary piston). A pressure can be generated, and this is directed to a wheel braking unit (wheel cylinder) as a wheel cylinder hydraulic pressure, so that a fail-safe measure at the time of the failure can be taken.

However, in the fail-safe measures, the master cylinder hydraulic pressure is the same value as the brake operating force compatible hydraulic pressure and is not boosted.
There is a problem that a large brake operation force is required, or that a sufficient master cylinder hydraulic pressure cannot be obtained even by such a large brake operation force, resulting in a long braking distance.

  In order to solve such a problem, the hydraulic pressure generated in the hydraulic pressure chamber (master cylinder hydraulic pressure) is inserted into a pipe line that is directed to the wheel braking unit, and backup hydraulic pressure generating means is provided. The backup hydraulic pressure generating means supplies a predetermined backup hydraulic pressure to the wheel braking unit (wheel cylinder) instead of the master cylinder hydraulic pressure in the event of a failure in which the boosting action cannot be obtained due to the failure of the control system. It is conceivable to configure.

According to this fail-safe measure, depending on the setting of the backup fluid pressure, the same state as when the master cylinder fluid pressure is boosted can be obtained. The pressure (wheel cylinder hydraulic pressure) can be generated, and the above problem that the braking distance becomes long can be solved.
Japanese Patent Laid-Open No. 10-138909

However, in the above fail-safe measures, when the backup fluid pressure generating means determines the backup fluid pressure,
Based on the master cylinder hydraulic pressure at the time of failure detected by the pressure sensor, the hydraulic pressure value increased by the prescribed boost ratio at the time of failure is used as the backup hydraulic pressure, causing the following problems.

In other words, the master cylinder hydraulic pressure at the time of failure is often in a high state that is still boosted,
In the above fail-safe measures, the master cylinder hydraulic pressure that is still in a boosted state is further increased by the specified failure boost ratio (double boosted) to determine the backup hydraulic pressure as the backup hydraulic pressure. The backup fluid pressure is too high.
For this reason, in the above fail-safe measures, there is a concern that, in the event of a failure, too high a backup hydraulic pressure that has been double boosted is supplied to the wheel braking unit (wheel cylinder), resulting in an uncomfortable sudden braking state.

  Although the present invention follows the above-described configuration using the backup hydraulic pressure at the time of failure, the backup hydraulic pressure is not determined based on the master cylinder hydraulic pressure at the time of failure, but is determined by a specific procedure. It is an object of the present invention to propose an electric boost type hydraulic brake device that can eliminate concerns about sudden braking with a sense of incongruity.

For this purpose, the electric boost type hydraulic brake device according to the present invention is constructed as described in claim 1.
First, to explain the electric boost hydraulic brake device that is the premise of the present invention,
In conjunction with the brake operation, when the brake hydraulic pressure generating means fails, the brake hydraulic pressure generating means mechanically strokes the brake hydraulic pressure generating means to generate the hydraulic pressure corresponding to the brake operating force in the hydraulic pressure chamber. Means,
A backup that allows the hydraulic pressure generated in the hydraulic pressure chamber to be inserted into a pipe that directs the wheel braking unit toward the wheel braking unit so that a predetermined backup hydraulic pressure can be supplied to the wheel braking unit when the brake hydraulic pressure generating means fails. And a hydraulic pressure generating means.

The present invention, in such an electric boost type hydraulic brake device,
When the brake fluid pressure generating means fails during the brake operation, the backup fluid pressure to the wheel braking unit is set to the fluid pressure value from the fluid pressure chamber toward the wheel braking unit immediately before the failure. The backup hydraulic pressure generating means is configured to operate.

According to the electric boost type hydraulic brake device of the present invention described above,
When the brake fluid pressure generating means fails during the brake operation, the backup fluid pressure is such that the backup fluid pressure to the wheel braking unit becomes the fluid pressure value that was directed from the fluid pressure chamber to the wheel braking unit immediately before the failure. To activate the generating means,
The fail-safe measure at the time of failure does not increase the hydraulic fluid pressure of the wheel braking unit by the above-described double boosting, and the above-described concerns regarding sudden braking with a sense of incongruity can be eliminated.

Hereinafter, embodiments of the present invention will be described in detail based on examples shown in the drawings.
FIG. 1 shows an electric boost type hydraulic brake device according to an embodiment of the present invention together with its electronic control system,
Reference numeral 1 denotes a tandem master cylinder, and reference numeral 2 denotes an electric brake booster 2 configured to be integrally coupled to the tandem master cylinder 1.

  The cylinder body 3 of the tandem master cylinder 1 and the booster housing 4 of the electric brake booster 2 are concentrically connected to each other, and pass through the connecting portions of the cylinder body 3 and the booster housing 4. The primary piston 5 of the tandem master cylinder 1 serving as brake fluid pressure generating means is provided at the center of the cylinder body 3 and the booster housing 4.

The primary piston 5 is slidably inserted into the inner sleeve 6 fitted in the cylinder body 3 at the left end (front end) in the figure.
A free piston type secondary piston 7 is slidably fitted into the cylinder body 3 between the left end (front end) of the primary piston 5 and the bottom wall of the cylinder body 3.
The right end (rear end) of the primary piston 5 is positioned in the booster housing 4, and the input rod 8 that is a hydraulic pressure generating means corresponding to the brake operation force is slid into the hollow hole in the right end (rear end) of the primary piston 5. Insert freely.

A spring seat 10 is engaged in the inner sleeve 6 between the primary piston 5 and the secondary piston 7, and a return spring 11 is contracted between the spring seat 10 and the primary piston 5.
The return spring 11 is housed in a cylinder chamber 12 as a hydraulic chamber defined between the pistons 5 and 7.

  Thus, the primary piston 5 is urged to the right in the drawing by the return spring 11, and a thrust member 31 is provided in which the stroke of the primary piston 5 by the return spring 11 is coaxially opposed to the right end surface (rear end surface) of the primary piston 5. Is brought into contact with the corresponding end face of the booster housing 4 to limit the inactive stroke position shown in the figure.

A return spring 13 is contracted between the secondary piston 7 and the bottom wall of the cylinder body 3, and this return spring 13 is a cylinder chamber 14 defined between the secondary piston 7 and the bottom wall of the cylinder body 3. Store inside.
Thus, in the normal state, the secondary piston 7 is elastically supported by the return spring 13 at the illustrated non-operation stroke position in contact with the spring seat 10.

A relief port 16 for communicating between the brake fluid supply port 15 provided in the inner sleeve 6 so as to communicate with a reservoir tank (not shown) and the cylinder chamber 12 at a non-operating stroke position of the illustrated primary piston 5 is provided. It is formed at the left end (front end) of the primary piston 5.
A relief port 18 for communicating between the brake fluid supply port 17 provided in the inner sleeve 6 so as to communicate with a reservoir tank (not shown) and the cylinder chamber 14 at a non-operating stroke position of the illustrated secondary piston 7 is provided. It is formed at the left end (front end) of the secondary piston 7.

These relief ports 16 and 18 are in positions where they are immediately disconnected from the corresponding brake fluid supply ports 15 and 17 when the corresponding pistons 5 and 7 are pushed to the left in the figure from the non-actuating stroke position shown in the figure. Deploy.
The cylinder body 3 is further connected to the cylinder chambers 12 and 14 to form brake fluid pressure outlet ports 3a and 3b. From these ports, the brake fluid pressure Pm is supplied to the two brake fluid pressure systems 20F and 20R of the hydraulic brake device. Can be output.

The input rod 8 is slidably inserted in a hollow hole at the right end (rear end) of the primary piston 5 and can be displaced relative to the primary piston 5 in the axial direction. In between, the neutral springs 21 and 22 which act on the input rod 8 in opposite directions are contracted.
These neutral springs 21 and 22 elastically support the input rod 8 relative to the primary piston 5 at the neutral position shown in the figure where the spring forces of the neutral springs 21 and 22 are balanced, and at the neutral position, the left end of the input rod 8 ( The front end is projected into the cylinder chamber 12 under a liquid tight seal.

The input rod 8 is provided with a step 8a to limit the amount of relative stroke of the input rod 8 relative to the primary piston 5 to the left in the figure,
After this restriction, the input rod 8 is caused to make a stroke with the primary piston 5, and a failsafe measure described later is taken.

The above is mainly the description of the tandem master cylinder 1, but the electric brake booster 2 including the thrust member 31 described above moves the primary piston 5 from the inoperative position shown in the figure via the ball screw mechanism 33 by the electric motor 32. It can be stroked to the left of the figure.
Although not shown in detail, the thrust member 31 is not rotatable with respect to the booster housing 4 and can be stroked only in the axial direction.
A return spring 34 for biasing the thrust member 31 to the right in the figure is contracted between the thrust member 31 and the booster housing 4, and the stroke of the thrust member 31 by the return spring 34 is determined by the booster housing. By contacting the corresponding end face of 4, the non-actuated stroke position shown is limited.

  Although the detailed illustration is omitted on the outer periphery of the thrust member 31 that cannot be rotated in this manner, the ball nut 35 of the ball screw mechanism 33 is screwed and the rotational position of the ball nut 35 is controlled by the electric motor 32, whereby the primary piston The stroke position of 5 can be controlled.

The two brake hydraulic systems 20F and 20R from the cylinder chambers 12 and 14 are connected to, for example, a front wheel wheel cylinder 41F as a front wheel braking unit and a rear wheel wheel cylinder 41R as a rear wheel braking unit, respectively.
A backup hydraulic pressure generating unit 42, which is a backup hydraulic pressure generating means, is provided by being inserted into these two brake hydraulic pressure systems 20F and 20R.

The backup hydraulic pressure generating unit 42 is changed from a normal state to a controlled state when the brake hydraulic pressure generating means in which the stroke control of the primary piston 5 by the electric motor 32 has become impossible is made, and the two brake hydraulic pressure systems 20F, 20R. It is assumed that the wheel cylinder hydraulic pressure Pw from the front wheel cylinder 41F to the rear wheel cylinder 41R functions to a predetermined backup hydraulic pressure different from the master cylinder hydraulic pressure Pm from the cylinder chambers 12 and 14.
However, at the normal time when the above-mentioned failure has not occurred, the backup hydraulic pressure generating unit 42 is brought into a normal uncontrolled state, and the master cylinder hydraulic pressure Pm from the cylinder chambers 12 and 14 is directly used as the wheel cylinder hydraulic pressure Pw as it is. The cylinder 41F and the rear wheel wheel cylinder 41R are assumed to face.

For this reason, the backup hydraulic pressure generating unit 42 is not shown in detail, but includes a common motor 43 and hydraulic pressure sources 44F and 44R including a pump driven by this motor and a pressure increasing / reducing valve set that performs the above function. Become
These hydraulic pressure sources 44F and 44R are configured to be inserted into the corresponding brake hydraulic pressure systems 20F and 20R, respectively.

The electric boost type hydraulic brake device including the master cylinder 1 and the electric brake booster 2 configured as described above is attached to the dashboard (not shown) of the vehicle.
The push rod 23 is interposed between the input rod 8 and the brake pedal 21 in the vehicle interior so that the input rod 8 can be directly linked to the brake pedal 24.

The control of the backup hydraulic pressure generation unit 42 (the motor 43 and the pressure increasing / reducing valve in the hydraulic pressure sources 44F and 44R) and the control of the electric motor 32 are performed by the controller 51, respectively.
The controller 51 includes a signal from a stroke sensor 52 that detects the stroke St of the brake pedal 23,
A signal from the master cylinder hydraulic pressure sensor 53 for detecting the master cylinder hydraulic pressure Pm;
A signal from the wheel cylinder hydraulic pressure sensor 54 for detecting the wheel cylinder hydraulic pressure Pw is input.

The operation of the above-described electric boost type hydraulic brake device will be described below.
When the brake pedal 24 is not depressed, the electric motor 32 is in a rotational position where the thrust member 31 (and hence the primary piston 5) is set to the inoperative stroke position shown in the drawing.
When the brake pedal 24 is depressed, the input rod 8 is stroked from the non-operating neutral position shown in the drawing to the left in the drawing via the push rod 23.

  At this time, the controller 51 determines that the brake operation has been performed from the brake pedal stroke St detected by the stroke sensor 52, and moves the electric motor 25 from the non-actuated stroke position of the input member to the thrust member 31 (and hence the primary piston 5). Rotate to stroke in the direction to follow 8.

  The stroke of the primary piston 5 through the thrust member 31 is cut off from the relief port 16 from the brake fluid supply port 15 to form the cylinder chamber 12 as a containment chamber, and coupled with the stroke of the primary piston 5 in the cylinder chamber 12. Cylinder hydraulic pressure (brake hydraulic pressure) Pm is generated, and this master cylinder hydraulic pressure (brake hydraulic pressure) Pm is output from port 3a.

  In response to the hydraulic pressure Pm in the cylinder chamber 12 generated by the stroke of the primary piston 5, the free piston type secondary piston 7 also strokes in the same direction. The stroke of the secondary piston 7 supplies the relief port 18 with brake fluid. The cylinder chamber 14 is shut off from the port 17 to serve as a containment chamber. Together with the stroke of the secondary piston 7, the same master cylinder hydraulic pressure (brake hydraulic pressure) Pm is generated in the cylinder chamber 14, and this brake hydraulic pressure Pm is generated in the port. Output from 3b.

At this time, the manner of the brake boost can be freely set according to how the controller 51 causes the thrust member 31 (primary piston 5) to follow the input rod 8 by the electric motor 32.
In the case where the boost ratio K is set to K = 5, the hydraulic pressure corresponding to the brake operation force generated when the input rod 8 causes the primary piston 5 to make an interlocking stroke through the step portion 8a is, for example, a broken line in FIG. In the case of the case shown in (when the brake pedal operating force is 20N, the brake operating force compatible hydraulic pressure is 1 MPa),
As indicated by the solid line in FIG. 2, the master cylinder hydraulic pressure Pm is a value obtained by multiplying the hydraulic pressure corresponding to the brake operation force indicated by the broken line in FIG. 2 by K times (5 times).

The above is a normal operation when the motor 32 and its drive control system are functioning normally. However, since the controller 51 does not output a control signal to the backup hydraulic pressure generating unit 42 at such normal times, the backup hydraulic pressure is generated. The unit 42 is in an uncontrolled state (normal state), and as described above, the master cylinder hydraulic pressure (brake hydraulic pressure) Pm from the cylinder chambers 12 and 14 to the brake hydraulic pressure systems 20F and 20R is directly applied to the wheel cylinder hydraulic pressure Pw. To the wheel braking units 41F and 41R.
Therefore, when normal, the wheel cylinder hydraulic pressure Pw increases with the same time series change as the master cylinder hydraulic pressure (brake hydraulic pressure) Pm from the braking start instant t1 as shown in FIG.
The wheel brake units 41F and 41R can be operated by the wheel cylinder hydraulic pressure Pw (= Pm) to perform predetermined braking.

By the way, when the motor 32 and its drive control system fail to function normally, the primary piston 5 becomes unable to stroke and stops at the stroke position shown in FIG.
Therefore, the input rod 8 interlocked with the brake operation strokes to the left in FIG. 1 relative to the primary piston 5, and finally strokes in the same direction with the primary piston 5 by the step portion 8a.

The stroke of the primary piston 5 shuts off the relief port 16 from the brake fluid supply port 15 to form the cylinder chamber 12 as a containment chamber, and in combination with the stroke of the primary piston 5, the master cylinder hydraulic pressure (brake fluid Pressure) Pm is generated, and this master cylinder hydraulic pressure (brake hydraulic pressure) Pm is output from port 3a.
Further, in response to the hydraulic pressure Pm in the cylinder chamber 12 generated as described above, the free piston type secondary piston 7 also strokes in the same direction, and the stroke of the secondary piston 7 causes the relief port 18 to move from the brake fluid supply port 17. Shut off to make cylinder chamber 14 a containment chamber. Combined with the stroke of secondary piston 7, the same master cylinder hydraulic pressure (brake hydraulic pressure) Pm is generated in cylinder chamber 14, and this brake hydraulic pressure Pm is output from port 3b. To do.

However, in this case, the master cylinder hydraulic pressure (brake hydraulic pressure) Pm is not subjected to the above-described boosting action by the electric motor 32. Therefore, as shown by the solid line as the failure Pm in FIG. Is much lower than that of the hydraulic pressure corresponding to the brake operation force in FIG.
Therefore, using this low failure master cylinder hydraulic pressure (brake hydraulic pressure) Pm as the wheel cylinder hydraulic pressure Pw as it is can avoid the worst situation of non-braking, but may cause insufficient braking force or large brake operation There is a problem that power is required.

Therefore, in the present embodiment, when the controller 51 determines the above failure before the braking start instant t1, a control signal is output to the backup hydraulic pressure generation unit 42, and the control state is set as follows.
That is, at this time, the controller 51 generates a control signal with a hydraulic pressure value obtained by boosting the low master cylinder hydraulic pressure (brake hydraulic pressure) Pm at a specified boost ratio K = 5 as a target value for the backup hydraulic pressure. Command the backup hydraulic pressure generating unit 42.

The backup hydraulic pressure generating unit 42 responds to this control signal, and as shown in FIG. 3, the wheel cylinder hydraulic pressure obtained by boosting the low master cylinder hydraulic pressure (brake hydraulic pressure) Pm with the specified boost ratio K = 5. Pw (backup hydraulic pressure) is directed from the brake hydraulic pressure system 20F, 20R to the wheel braking units 41F, 41R.
Therefore, even at the time of the failure, the wheel cylinder hydraulic pressure Pw is the same value as that in the normal state shown in FIG. 2, and it is possible to avoid the problem that the braking force is insufficient or a large brake operation force is required. it can.

However, if the above fail-safe control at the time of failure is executed in the same way even at the time of failure during braking, the problem described below with reference to FIG. 4 occurs.
FIG. 4 shows the same braking state after the instant t2 in FIG. 2, that is, at the instant t3 during braking in which the brake pedal depression force is maintained at 20 N and the master cylinder hydraulic pressure Pm = 5 MPa remains unchanged as the wheel cylinder hydraulic pressure Pw = 5 MPa. It is an operation | movement time chart at the time of performing said fail-safe control in the same way also when said failure occurs.

Even if the motor 32 cannot control the stroke of the primary piston 5 due to the failure, the primary piston 5 is maintained at the stroke position at the time of failure due to the change of the brake pedal position. As shown, Pm = 5 MPa is also maintained after the failure t3.
For this reason, the controller 51 uses the hydraulic pressure value 25 MPa obtained by boosting the master cylinder hydraulic pressure Pm = 5 MPa detected by the sensor 53 at a specified boost ratio K = 5 as a target value for the backup hydraulic pressure. The signal is commanded to the backup hydraulic pressure generating unit 42.

At this time, the backup hydraulic pressure generating unit 42 responds to this control signal and, as shown in FIG. 4, further doubles the above-mentioned boosted master cylinder hydraulic pressure Pm = 5 MPa at the specified boost ratio K = 5. The applied wheel cylinder hydraulic pressure Pw (backup hydraulic pressure) is directed from the brake hydraulic pressure system 20F, 20R to the wheel braking units 41F, 41R.
Therefore, at the time of failure during braking, the wheel cylinder hydraulic pressure Pw is double boosted, and as high as 25 MPa as shown after the failure t3 in FIG. 4, sudden braking with a sense of incongruity due to excessive braking force can occur. This causes a problem that occurs.

At this time, the inside of the cylinder chamber 12 is also set to the same pressure as the above-described excessive wheel cylinder hydraulic pressure Pw (backup hydraulic pressure) = 25 MPa, and the assisting force of the primary piston 5 by the electric motor 32 becomes zero.
The above-mentioned hydraulic pressure in the cylinder chamber 12 = 25 MPa is kicked back to the brake pedal 24 as it is, and the brake pedal depression force (brake pedal reaction force) is increased from 20N to 100N by multiplying this by the boost ratio K = 5. To do.

In order to solve this problem, in this embodiment, the fail-safe control at the time of failure during braking as described below with reference to FIG. 5 is adopted.
FIG. 5 shows the same braking state after the instant t2 of FIG. It is an operation | movement time chart when the said failure generate | occur | produces.

After the failure t3 during braking, the controller 51 controls the wheel cylinder hydraulic pressure Pw = 5 MPa from the cylinder chambers 12 and 14 toward the wheel braking units 41F and 41R at the time of the failure as a target value of the backup hydraulic pressure. Is commanded to the backup hydraulic pressure generating unit 42.
At this time, the backup hydraulic pressure generating unit 42 responds to this control signal and holds the wheel cylinder hydraulic pressure Pw (backup hydraulic pressure) at the hydraulic pressure value 5 MPa at the time of failure t3 after the failure t3 as shown in FIG. The wheel cylinder hydraulic pressure Pw = 5 MPa is directed from the brake hydraulic pressure system 20F, 20R to the wheel braking units 41F, 41R.

  Therefore, the fail-safe measure at the time of failure during braking is that the hydraulic fluid pressure of the wheel braking units 41F and 41R is not excessively increased by the double boosting as described above with reference to FIG. Concerns can be dispelled.

  The fail-safe control at the time of failure during braking described above with reference to FIG. 5 is for the case where the brake pedal operation is kept unchanged after the failure, but after the failure, the brake pedal is depressed or depressed to operate the brake pedal. Is changed to fail-safe control during failure as described below with reference to FIG.

FIG. 6 shows the same braking state after the instant t2 in FIG. 2, that is, at the instant t3 during braking in which the brake pedal depression force is maintained at 20 N and the master cylinder hydraulic pressure Pm = 5 MPa remains unchanged as the wheel cylinder hydraulic pressure Pw = 5 MPa. Said failure occurs,
During this failure t3 to instant t4, perform the brake pedal depressing operation as shown by the brake pedal depression force change,
During the instant t4 to t5, perform the depressing operation of the brake pedal as shown by the brake pedal pressing force change,
FIG. 5 is an operation time chart when a brake pedal depressing operation is performed between instants t5 and t6 as indicated by a change in brake pedal depression force.

  While the brake pedal is being depressed from the time t3 to the moment t4 (while the brake operating force is decreasing), the controller 51 performs backup fluid in relation to the master cylinder hydraulic pressure Pm that decreases as shown in the figure. The target value of pressure (wheel cylinder hydraulic pressure Pw) is determined as follows.

  In other words, the controller 51 performs wheel braking when the brake pedal depressing operation (decreasing brake operating force) is started (t3) with respect to the backup hydraulic pressure (wheel cylinder hydraulic pressure Pw) with respect to the master cylinder hydraulic pressure Pm. Boost ratio K1 = (5MPa / 5MPa) between wheel cylinder hydraulic pressure Pw = 5MPa that was heading toward units 41F and 41R and master cylinder hydraulic pressure Pm = 5MPa that was generated in cylinder chambers 12 and 14 = The backup hydraulic pressure generating unit 42 is commanded with a control signal for setting the backup hydraulic pressure value (wheel cylinder hydraulic pressure Pw) at the time of decrease while maintaining 1 as the target value of the backup hydraulic pressure (wheel cylinder hydraulic pressure Pw).

  At this time, the backup hydraulic pressure generating unit 42 responds to this control signal, and as shown in FIG. 6, the wheel cylinder hydraulic pressure Pw (backup hydraulic pressure) from the instant t3 to the master cylinder after the start of the brake pedal depressing operation t3. It operates so as to decrease the hydraulic pressure Pm while maintaining the boost ratio K1 = 1 determined as described above, and this wheel cylinder hydraulic pressure Pw is directed from the brake hydraulic system 20F, 20R to the wheel braking units 41F, 41R. .

Therefore, the wheel cylinder hydraulic pressure Pw (backup hydraulic pressure) to the wheel braking units 41F and 41R during the t3 to t4 when the brake pedal is depressed while the fail-safe measures are taken during braking. However, the boost ratio K1 set as described above with respect to the master cylinder hydraulic pressure Pm is maintained and decreased.
The brake force can be reduced linearly when the brake pedal is depressed by the driver, and a natural braking feeling corresponding to the brake pedal depressing operation can be realized even during fail-safe control during failure. Can do.

  During the depression of the brake pedal between the instants t4 and t5 in FIG. 6 (while the brake operation force is increasing), the controller 51 performs backup hydraulic pressure in relation to the master cylinder hydraulic pressure Pm that increases as shown. Determine the target value of (wheel cylinder hydraulic pressure Pw) as follows.

  That is, the controller 51 determines that the wheel cylinder hydraulic pressure Pw (backup hydraulic pressure) after the start of increase in brake operation force t4 is the amount of increase ΔPm in the master cylinder hydraulic pressure Pm from the start of increase in the brake operation force t4 to the present. Backup hydraulic pressure value when increasing by the hydraulic pressure (ΔPm × K) obtained by multiplying the specified failure boost ratio (here, K = 5, which is the same as the normal boost ratio) A control signal for setting the wheel cylinder hydraulic pressure Pw) as a target value of the backup hydraulic pressure (wheel cylinder hydraulic pressure Pw) is commanded to the backup hydraulic pressure generating unit 42.

  At this time, the backup hydraulic pressure generating unit 42 responds to this control signal, and, as shown in FIG. 6, during the t4 to t5 during the brake pedal depressing operation, the wheel cylinder hydraulic pressure Pw (backup hydraulic pressure) is set to the above hydraulic pressure ( The wheel cylinder hydraulic pressure Pw is moved from the brake hydraulic pressure systems 20F and 20R to the wheel braking units 41F and 41R.

Therefore, the wheel cylinder hydraulic pressure Pw (backup hydraulic pressure) to the wheel braking units 41F and 41R is maintained during t4 to t5 when the brake pedal is depressed while failsafe measures are taken during braking. As the master cylinder hydraulic pressure Pm increases, it is increased by the hydraulic pressure determined as described above (ΔPm × K). As a result, the wheel cylinder hydraulic pressure Pw (backup hydraulic pressure) to the wheel braking units 41F and 41R is increased. , Boost ratio K2 = K = 5 with respect to master cylinder hydraulic pressure Pm,
The driver's boost hydraulic pressure corresponding to the depression of the brake pedal can be directed to the wheel braking units 41F and 41R. Sufficient control is available to handle the depression of the brake pedal even during fail-safe control during failure during braking. Power can be generated.

  While the brake pedal is being stepped back from the moment t5 to t6 in FIG. 6 (while the brake operation force is decreasing), the controller 51 is also stepping back the brake pedal (the brake operation force is being reduced) as described above for the instant t3 to t4. ), The target value of the backup hydraulic pressure (wheel cylinder hydraulic pressure Pw) is determined as follows in relation to the master cylinder hydraulic pressure Pm that decreases as shown in the figure.

  In other words, the controller 51 performs wheel braking when the brake pedal depressing operation (decreasing brake operating force) is started (t5) with respect to the backup hydraulic pressure (wheel cylinder hydraulic pressure Pw) with respect to the master cylinder hydraulic pressure Pm. Boost ratio K3 = (4MPa / 1.6MPa) between wheel cylinder hydraulic pressure Pw = 4MPa toward unit 41F, 41R and master cylinder hydraulic pressure Pm = 1.6MPa generated in cylinder chambers 12, 14 ) = Commands the backup hydraulic pressure generating unit 42 to control the backup hydraulic pressure value (wheel cylinder hydraulic pressure Pw) at the time of decrease while maintaining 2.5 as a target value of the backup hydraulic pressure (wheel cylinder hydraulic pressure Pw).

  At this time, the backup hydraulic pressure generating unit 42 responds to this control signal, and as shown in FIG. 6, the wheel cylinder hydraulic pressure Pw (backup hydraulic pressure) from the instant t5 to the master cylinder after the start of the brake pedal depressing operation t5. It operates so as to reduce the hydraulic pressure Pm while maintaining the boost ratio K3 = 2.5 as defined above, and this wheel cylinder hydraulic pressure Pw is directed from the brake hydraulic pressure system 20F, 20R to the wheel braking units 41F, 41R. .

Therefore, during the t5 to t6 when the brake pedal is depressed while the fail-safe measures are taken during braking, the wheel cylinder hydraulic pressure Pw (backup hydraulic pressure) to the wheel braking units 41F and 41R However, the boost ratio K3 determined as described above with respect to the master cylinder hydraulic pressure Pm is maintained to be 2.5,
The brake force can be reduced linearly when the brake pedal is depressed by the driver, and a natural braking feeling corresponding to the brake pedal depressing operation can be realized even during fail-safe control during failure. Can do.

  By the way, when the brake pedal is stepped back (decrease in brake operation force) during fail-safe control during failure during braking, unconditionally between the instants t3 and t4 in FIG. When the above-described control is performed between the instants t5 and t6 in the figure, the problem described below with respect to FIG. 7 occurs.

FIG. 7 shows the same braking state after the instant t2 of FIG. Said failure occurs,
In response to this, the driver depressed the brake pedal for a moment between t3 and t4, but suddenly depressed the brake pedal force (brake pedal reaction force) suddenly increased by the fail-safe control. It is an operation time chart in the case where the brake pedal is depressed again between t4 and t5 (refer to the increase in the pedal force shown in the figure).

Thus, unconditionally during the period t3 to t4 when the brake pedal depressing operation is not intended to reduce the brake operating force, between the instant t3 and t4 in FIG. 6 and between the instant t5 and t6 in the figure When the brake pedal depressing control described above is performed,
As indicated by the alternate long and short dash line in FIG. 7, the wheel cylinder hydraulic pressure Pw decreases rapidly while maintaining the boost ratio K1 = 1 with respect to the master cylinder hydraulic pressure Pm in the same manner as the wheel cylinder hydraulic pressure Pw between the instants t3 and t4 in FIG. .

  Such a sudden decrease greatly reduces the wheel cylinder hydraulic pressure Pw in spite of the period t3 to t4 when the brake pedal depressing operation that is not intended to decrease the brake operating force is performed, and the subsequent brake pedal When the engine is stepped on again, a return delay of the wheel cylinder hydraulic pressure Pw occurs from t4 to t5.

  Therefore, in this embodiment, when the brake pedal depression force increases immediately after the decrease, when the controller 51 controls the backup hydraulic pressure generating unit 42 in response to the decrease in the brake pedal depression force, the brake pedal depression force decrease ( As shown by A1, A2, and A3 in FIG. 7, the decrease in the wheel cylinder hydraulic pressure Pw (back-up hydraulic pressure) in response to t3 to t4 in FIG. The backup hydraulic pressure generating unit 42 is controlled.

The reduction characteristics of the wheel cylinder hydraulic pressure Pw (backup hydraulic pressure) indicated by A1, A2, and A3 in Fig. 7 all decrease the backup hydraulic pressure while maintaining a boost ratio smaller than the boost ratio K1 described above with reference to Fig. 6. In the following, the A1, A2, and A3 characteristics will be described individually.
The drop characteristic of wheel cylinder hydraulic pressure Pw (backup hydraulic pressure) indicated by A1 in FIG.
Instead of the master cylinder hydraulic pressure Pm at the start t3 when the brake pedal depression starts, the average value of the master cylinder hydraulic pressure Pm at the past multiple times after the start of the brake pedal depression t3 is used. The ratio of the wheel cylinder hydraulic pressure Pw at the start t3 is the boost ratio, and the hydraulic pressure value that keeps this small boost ratio relative to the master cylinder hydraulic pressure Pm is the target value of the wheel cylinder hydraulic pressure Pw (backup hydraulic pressure) It is a characteristic in the case of.

  When the wheel cylinder hydraulic pressure Pw (backup hydraulic pressure) is reduced as indicated by A1 in FIG. 7, the controller 51 determines the wheel cylinder hydraulic pressure Pw at t3 when the pedal depression force starts to decrease with respect to the master cylinder hydraulic pressure Pm, and the pedal. The hydraulic pressure value that decreases while maintaining the boost ratio between the average value of the master cylinder hydraulic pressure Pm for the past multiple times after t3 when treading force starts to decrease is the target value of the backup hydraulic pressure value (wheel cylinder hydraulic pressure Pw). A control signal to be transmitted is commanded to the backup hydraulic pressure generating unit 42.

  At this time, the backup hydraulic pressure generating unit 42 responds to this control signal, and as shown by A1 in FIG. 7, the wheel cylinder hydraulic pressure Pw (backup hydraulic pressure) is calculated from the instant t3 after t3 when the brake pedal depressing operation starts. The wheel cylinder hydraulic pressure Pw is directed from the brake hydraulic pressure system 20F, 20R to the wheel braking units 41F, 41R by lowering the master cylinder hydraulic pressure Pm while maintaining the boost ratio determined as described above.

Therefore, even if a brake pedal depressing operation is performed while fail-safe measures are taken during a failure during braking, this does not intend to reduce the pedal effort as in the instant t3 to t4 in FIG. If it is,
The wheel cylinder hydraulic pressure Pw (backup hydraulic pressure) to the wheel braking units 41F and 41R is slowly reduced at a boost ratio smaller than the boost ratio K1 = 1 at the instant t3 to t4 in FIG.
The wheel cylinder hydraulic pressure Pw will not be significantly reduced despite the brake pedal stepping back operation that is not intended to reduce the brake operating force. It is possible to solve the problem that the return delay of the wheel cylinder hydraulic pressure Pw occurs.

The decrease characteristic of wheel cylinder hydraulic pressure Pw (backup hydraulic pressure) indicated by A2 in FIG.
When a brake pedal depressing operation that does not intend to reduce the brake operating force is performed, the boost ratio is not calculated, but the boost ratio is fixed to a small upper limit value, and this is compared with the master cylinder hydraulic pressure Pm. This is a characteristic when a hydraulic pressure value that maintains a small upper limit boost ratio is a target value of the wheel cylinder hydraulic pressure Pw (backup hydraulic pressure).

  When the wheel cylinder hydraulic pressure Pw (backup hydraulic pressure) is reduced as indicated by A2 in FIG. 7, the controller 51 reduces the hydraulic pressure value while maintaining the above small upper limit boost ratio with respect to the master cylinder hydraulic pressure Pm. Is commanded to the backup hydraulic pressure generating unit 42 as a target value for the backup hydraulic pressure value (wheel cylinder hydraulic pressure Pw).

  At this time, the backup hydraulic pressure generating unit 42 responds to this control signal, and as shown by A2 in FIG. 7, the wheel cylinder hydraulic pressure Pw (backup hydraulic pressure) is calculated from the instant t3 after t3 when the brake pedal depressing operation starts. It operates so as to decrease the master cylinder hydraulic pressure Pm while maintaining the above small upper limit boost ratio, and this wheel cylinder hydraulic pressure Pw is directed from the brake hydraulic pressure system 20F, 20R to the wheel braking units 41F, 41R.

Therefore, even if a brake pedal depressing operation is performed while fail-safe measures are taken during a failure during braking, this does not intend to reduce the pedal effort as in the instant t3 to t4 in FIG. If it is,
The wheel cylinder hydraulic pressure Pw (backup hydraulic pressure) to the wheel braking units 41F and 41R is slowly lowered at an upper boost ratio smaller than the boost ratio K1 = 1 at the instant t3 to t4 in FIG.
The wheel cylinder hydraulic pressure Pw will not be significantly reduced despite the brake pedal stepping back operation that is not intended to reduce the brake operating force. It is possible to solve the problem that the return delay of the wheel cylinder hydraulic pressure Pw occurs.

The wheel cylinder hydraulic pressure Pw (backup hydraulic pressure) characteristic indicated by A3 in FIG.
When a brake pedal depressing operation that does not intend to decrease the brake operating force is performed, the boost ratio is not calculated and the upper limit is not set, and the value of the wheel cylinder hydraulic pressure Pw at t3 during the brake pedal depressing operation is calculated. This is a characteristic when the target value of the wheel cylinder hydraulic pressure Pw (backup hydraulic pressure) is set and maintained for a certain period of time.

  When the wheel cylinder hydraulic pressure Pw (back-up hydraulic pressure) is maintained as indicated by A3 in FIG. 7, the controller 51 sets the wheel cylinder hydraulic pressure Pw at the time t3 when the brake pedal is stepped back to the wheel for the predetermined time. The cylinder hydraulic pressure Pw (backup hydraulic pressure) is maintained as a target value, and a corresponding control signal is commanded to the backup hydraulic pressure generating unit 42.

  At this time, the backup hydraulic pressure generating unit 42 responds to this control signal. As shown by A3 in FIG. 7, the wheel cylinder hydraulic pressure Pw (backup hydraulic pressure) is maintained for a certain period of time after t3 when the brake pedal depressing operation starts. Is maintained at the fluid pressure value at the instant t3, and the wheel cylinder fluid pressure Pw is directed from the brake fluid pressure systems 20F and 20R to the wheel braking units 41F and 41R.

Therefore, even if a brake pedal depressing operation is performed while fail-safe measures are taken during a failure during braking, this does not intend to reduce the pedal effort as in the instant t3 to t4 in FIG. If it is,
The wheel cylinder hydraulic pressure Pw (backup hydraulic pressure) to the wheel braking units 41F and 41R is maintained at the instantaneous t3 value without being reduced.
The wheel cylinder hydraulic pressure Pw will not be significantly reduced despite the brake pedal stepping back operation that is not intended to reduce the brake operating force. It is possible to solve the problem that the return delay of the wheel cylinder hydraulic pressure Pw occurs.

It is a principal part vertical side view which shows the electric boost type hydraulic brake device which becomes one Example of this invention with the electronic control system. 2 is an operation time chart when the electric boost type hydraulic brake device shown in FIG. 1 is normal. FIG. 2 is an operation time chart when the boost failure occurs during non-braking in the electric boost hydraulic brake device shown in FIG. FIG. 2 is an operation time chart when the conventional control is executed in the case where the boost failure occurs during braking by the electric boost hydraulic brake device shown in FIG. FIG. 3 is an operation time chart when the brake pedal operating force does not change when the electric boost type hydraulic brake device shown in FIG. 1 has a boost failure during braking. FIG. FIG. 2 is an operation time chart when the brake pedal operating force changes when the electric boost type hydraulic brake device shown in FIG. 1 has a boost failure during braking. Operation time chart when the brake pedal depressing operation that does not intend to decrease the brake pedal operating force is performed when the electric boost type hydraulic brake device shown in FIG. It is.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Master cylinder 2 Electric brake booster 3 Cylinder body 4 Booster housing 5 Primary piston (brake hydraulic pressure generating means)
6 Inner sleeve 7 Secondary piston 8 Input rod (hydraulic pressure generating means corresponding to brake operating force)
11,13 Return spring
12,14 Cylinder chamber (hydraulic chamber)
15,17 Brake fluid supply port
16,18 Relief port
20F, 20R Brake hydraulic system (brake hydraulic line)
21,22 Neutral spring
23 Push rod
24 Brake pedal
31 Thrust member
32 electric motor
33 Ball screw mechanism
34 Return spring
41 Wheel braking unit
42 Backup fluid pressure generating unit (backup fluid pressure generating means)
44F, 44R Hydraulic pressure source
51 Controller
52 Brake pedal stroke sensor
53 Master cylinder hydraulic pressure sensor
54 Wheel cylinder hydraulic pressure sensor

Claims (8)

Brake fluid pressure generating means for generating a predetermined brake fluid pressure in the fluid pressure chamber by being stroked by an electric motor according to a brake operation;
In conjunction with the brake operation, when the brake hydraulic pressure generating means fails, the brake hydraulic pressure generating means mechanically strokes the brake hydraulic pressure generating means to generate the hydraulic pressure corresponding to the brake operating force in the hydraulic pressure chamber. Means,
A backup that allows the hydraulic pressure generated in the hydraulic pressure chamber to be inserted into a pipe that directs the wheel braking unit toward the wheel braking unit so that a predetermined backup hydraulic pressure can be supplied to the wheel braking unit when the brake hydraulic pressure generating means fails. In the electric boost type hydraulic brake device comprising the hydraulic pressure generating means,
When the brake fluid pressure generating means fails during the brake operation, the backup fluid pressure to the wheel braking unit is set to the fluid pressure value from the fluid pressure chamber toward the wheel braking unit immediately before the failure. An electric boost type hydraulic brake device characterized in that the backup hydraulic pressure generating means is operated. In the electric boost type hydraulic brake device according to claim 1,
While the brake operating force is reduced after the failure of the brake hydraulic pressure generating means, the hydraulic pressure value at which the backup hydraulic pressure to the wheel braking unit is directed toward the wheel braking unit at the start of the decrease in the brake operating force And an electric booster hydraulic pressure characterized in that the backup hydraulic pressure generating means is operated so as to decrease while maintaining a boost ratio between the hydraulic pressure generated in the hydraulic pressure chamber and the hydraulic pressure generated in the hydraulic pressure chamber. Brake device. In the electric boost type hydraulic brake device according to claim 1 or 2,
While the brake operation force increases after the failure of the brake hydraulic pressure generating means, the backup hydraulic pressure to the wheel braking unit is the hydraulic pressure in the hydraulic chamber from the start of the increase of the brake operation force to the present. An electric boost type hydraulic brake device characterized in that the backup hydraulic pressure generating means is operated so as to increase by an amount of hydraulic pressure obtained by multiplying the increase amount by a prescribed boost ratio at failure. In the electric boost type hydraulic brake device according to claim 2 or 3,
If the brake operating force is increased immediately after the brake fluid pressure generating unit fails, the backup hydraulic pressure generating unit is controlled so as to suppress the decrease in the backup hydraulic pressure in response to the decrease in the brake operating force. An electric boost type hydraulic brake device characterized by being configured to control. In the electric boost type hydraulic brake device according to claim 4,
The suppression of the decrease in the backup hydraulic pressure is a boost ratio between the hydraulic pressure value toward the wheel braking unit and the hydraulic pressure generated in the hydraulic pressure chamber at the start of the decrease in brake operation force. Instead, the electric booster hydraulic brake device is realized by lowering the backup hydraulic pressure while maintaining a smaller booster ratio. In the electric boost type hydraulic brake device according to claim 5,
The small boost ratio is obtained by using the average value of the hydraulic pressure values in the hydraulic chamber a plurality of times in the past after the brake operating force is reduced, instead of the hydraulic pressure in the hydraulic pressure chamber at the start of the decrease in the brake operating force. An electric boost type hydraulic brake device having a boost ratio obtained. In the electric boost type hydraulic brake device according to claim 5,
The electric boost type hydraulic brake device, wherein the small boost ratio is a boost ratio obtained by setting an upper limit of the boost ratio. In the electric boost type hydraulic brake device according to claim 5,
The suppression of the decrease in the backup hydraulic pressure is realized by maintaining the backup hydraulic pressure at the same value as the hydraulic pressure value directed toward the wheel braking unit when the brake operation force starts decreasing for a certain period of time. Electric boost type hydraulic brake device.

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