JP2521930B2 - Vehicle brake device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a vehicle brake device, and more particularly to a vehicle brake device capable of stopping a vehicle with a small amount of shaking back.

2. Description of the Related Art When stopping a running vehicle, if the brake pedal is continuously operated until the vehicle stops, so-called swinging back occurs at the time of stopping, and it is unavoidable to give an occupant a discomfort.
This is because when the vehicle running speed (hereinafter referred to as the vehicle speed) becomes zero and the vehicle stops, the deceleration suddenly drops from a constant value to zero. It is necessary to operate the brake with care so that it does not occur.

In order to alleviate such swinging back when the vehicle is stopped, in the device disclosed in Japanese Utility Model Laid-Open No. 56-129341, a rod that transmits the pedaling force of the brake pedal to the piston of the master cylinder when the brake pedal is depressed. While the pedal is moved forward with the pedal to operate the master cylinder, the rod can be retracted with the pedal in the depressed position immediately before the vehicle speed reaches zero, and the braking is automatically released. Is being done. The rod is connected to the brake pedal by a link mechanism that includes a solenoid, and normally moves with the pedal, but the solenoid is excited based on the signal output from the zero speed terminal of the speedometer immediately before the vehicle speed reaches zero. The current is supplied, the link mechanism allows the rod to move relative to the pedal, and the rod is retracted while the pedal is in the depressed position to release the brake. Thus, if the brake is released immediately before the vehicle speed becomes zero, the driver's intentional release of the brake pedal can be achieved, and the rebound can be reduced.

Problems to be Solved by the Invention However, the state in which the link mechanism allows the rod to retreat also means the state in which the brake pedal is allowed to move in the depressing direction, and the brake is applied when the vehicle is stopped. There is a problem that the pedal suddenly moves in a certain amount in the depressing direction and the posture of the driver is lost.

Further, it is desirable that the brake hydraulic pressure of the master cylinder be smoothly reduced in order to completely prevent the swaying back.However, in the above-mentioned device, the hydraulic pressure of the master cylinder is drastically reduced. There is also the problem that it is difficult to achieve the full preventive effect.

Furthermore, since the solenoid must be capable of generating a force of the same magnitude as the force transmitted from the brake pedal to the rod, it is inevitable that the solenoid becomes large,
There is also a problem that cost and weight increase cannot be avoided.

Means for Solving the Problems In order to solve the above-mentioned problems, the vehicle brake device according to the present invention is, as shown in FIG. 1, (a) depending on the depression of the brake pedal, A fluid pressure brake system that suppresses rotation, (b) vehicle speed detection means for detecting the vehicle speed of the vehicle, and (c) a deceleration that acquires the deceleration of the vehicle caused by the action of the fluid pressure brake system in response to depression of the brake pedal. Speed detection means, (d) reference vehicle speed determination means for determining a reference vehicle speed based on the deceleration acquired by the deceleration acquisition means and a predetermined time constant, and (e) detected by the vehicle speed detection means. After the vehicle speed has decreased to the reference vehicle speed, the fluid pressure of the fluid pressure brake system is reduced exponentially based on the time constant regardless of the constant depression force of the brake pedal. And a decompression control means for making the vehicle speed zero and the deceleration zero at the same time.

In order to exponentially decrease the fluid pressure in the fluid pressure brake system, for example, the boosting factor of the brake booster arranged between the brake pedal and the master cylinder may be exponentially reduced. It is also possible to use an actuator or controller of the anti-skid device to exponentially reduce the brake fluid pressure in the wheel cylinders regardless of the brake operating force.

In the vehicle brake device configured as described above, the reference vehicle speed determination means determines the reference vehicle speed based on the deceleration of the vehicle and the predetermined time constant, and the decompression control means determines the vehicle speed based on the vehicle speed. After the vehicle speed is reduced, the fluid pressure of the fluid pressure brake system is exponentially reduced based on the time constant so that the vehicle speed becomes zero and the deceleration becomes zero at the same time.

In order to completely eliminate the rolling back of the vehicle, it is necessary to smoothly reduce the deceleration immediately before the vehicle stops and to make the vehicle speed zero and the deceleration zero at the same time. Then, if the deceleration is exponentially decreased, the deceleration can be smoothly decreased, and the shape of the decrease curve is determined by the time constant of the exponential function. Further, since the deceleration of the vehicle is almost proportional to the fluid pressure of the brake system, if the fluid pressure is reduced exponentially, the vehicle deceleration can be reduced exponentially. And the time constants that define the deceleration decrease curve are approximately the same.

In addition, in the swing-back prevention control, it is desirable to set the time constant in advance. The fact that the time constant is set in advance means that the shape of the deceleration decrease curve is set in advance, and this is one of the reasons why the driver is easily accustomed to the change in deceleration due to the swing-back control. And
Another reason is that the fluid pressure can be easily controlled if the time constant of the fluid pressure drop curve is predetermined.

On the other hand, at least in the final stage of vehicle braking (near the time point when the swing-back control is started), it may be considered that the fluid pressure in the brake system is kept substantially constant and the vehicle speed is reduced substantially linearly. Although there are many cases, the decreasing gradient (deceleration) of the vehicle speed changes variously according to the depression force of the brake pedal. Then, no matter how the vehicle speed decrease gradient changes, the deceleration (and thus the vehicle speed) will be based on the predetermined time constant.
In order to smoothly reduce the vehicle speed and the vehicle speed to zero and the deceleration to zero at the same time, the straight line of various decreasing gradients and the vehicle speed decrease curve showing the vehicle speed change during the rebound prevention control are smoothed. It is necessary to be continuous.
To this end, when the vehicle speed that is decreasing at each decrease gradient (deceleration) reaches the vehicle speed that is at the point of contact between the straight line of each decrease gradient and the vehicle speed decrease curve that is being controlled to prevent deviation, The fluid pressure lowering control for the above may be started. The vehicle speeds at the points of contact between the straight lines of the respective decrease gradients and the vehicle speed decrease curves during the anti-swayback control are the reference vehicle speeds in the present invention.

EFFECTS OF THE INVENTION In the vehicle brake device according to the present invention, the fluid pressure of the fluid pressure brake system is reduced as described above, but the fluid pressure is not suddenly reduced, and is smoothly reduced exponentially. Therefore, both the vehicle speed and the deceleration are smoothly reduced, and further, the vehicle speed is controlled so that the vehicle speed becomes zero and the deceleration becomes zero at the same time, so that the swing back is completely prevented.

Further, when the fluid pressure of the fluid pressure brake system is reduced, the brake pedal does not move rapidly in a certain amount in the stepping direction as in the device described in the above publication. When the booster ratio of the brake booster is reduced, if the depression force of the brake pedal is kept constant, the brake pedal will be pushed back by a certain amount.
This will not disturb the driver's posture. Also,
When the anti-skid device is used to reduce the fluid pressure, the brake pedal may have some effect depending on the type of the anti-skid device, but this does not affect the driver's posture, and , An anti-skid device that has no effect on the brake pedal has already been developed.

Further, since a large solenoid is not required as in the above device, it is possible to obtain the above effect while suppressing an increase in vehicle weight and cost.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 2 is a diagram showing a vehicle brake device according to an embodiment of the present invention. In the figure, 10 is a brake pedal which is a brake operating member, and this pedal 10 operates a master cylinder 14 via a booster 12. Master cylinder 14
Has two pressurizing chambers independent of each other, and generates the hydraulic pressure of the same height in each pressurizing chamber based on the depression operation of the brake pedal 10. The hydraulic pressure generated in one pressurizing chamber is supplied to front wheel cylinders 20 and 22 of brakes provided on the left and right front wheels 16 and 18, respectively. The hydraulic pressure generated in the other pressurizing chamber is
And 26 are respectively supplied to the rear wheel cylinders 28 and 30 of the brakes, and this brake device is of a front and rear dual system type.

The booster 12 has an airtight casing 34 as shown in FIG. 3, and the inside of the casing 34 is divided into two parts by a diaphragm type power piston 36. One of the two chambers is divided into a vacuum source such as an engine intake manifold and a vacuum pump via a pipe joint 38 with a check valve.
A constant pressure chamber 42 connected to 40 is formed, and the other chamber is formed as a constant pressure chamber 42 or a variable pressure chamber 44 that is selectively communicated with the atmosphere to change the internal pressure. Power piston 36 is a constant pressure chamber
The return spring 46 disposed in the inside of the casing 42 urges it to the right in FIG. 3, and is always held in the original position where it abuts against the inner surface of the casing 34. When the pressure difference of 44 reaches or exceeds the set value, it moves (forwards) to the left against the biasing force of the spring 46.

The power piston 36 has a casing 34 at its outer peripheral edge.
A diaphragm rubber 50 held by the above, a diaphragm plate 52 that supports the diaphragm rubber 50, and a power piston main body 54 integrally attached to the diaphragm plate 52. The power piston main body 54 is formed with a communication passage 60 for communicating the constant pressure chamber 42 and the variable pressure chamber 44 and a communication passage 62 for communicating the variable pressure chamber 44 with the atmosphere, and also with the constant pressure chamber 42 of the variable pressure chamber 44 and the atmosphere. A control valve 64 and a relay mechanism 70 for controlling the communication of are provided.

The control valve 64 includes a first valve seat 72 formed on the power piston main body 54, a second valve seat 76 formed on a valve plunger 74 slidably fitted on the power piston main body 54, and both valve seats. The valve element 78 is made of an elastic material and is commonly arranged for the 72 and 76. The valve element 78 is biased toward both valve seats 72 and 76 by a compression spring 80. Further, the valve plunger 74 is connected to the input rod 82 connected to the brake pedal 10, and the forward end and the backward end are restricted by the stopper key 84.
The stopper key 84 has a base end portion fitted in a radial cutout hole provided in the power piston main body 54, and is prevented from coming off by an annular stopper plate 86 provided in an inner peripheral portion of the diaphragm rubber 50. That is, its tip is engaged with an annular groove formed in the valve plunger 74.

On the other hand, the relay mechanism 70 includes the valve plunger 74
And a relay member 90 fitted to the power piston body 54,
The reaction disk 92 made of soft rubber is interposed between the two. The reaction disc 92 has a function of transmitting a resultant force of both forces to the relay member 90 while allowing a minute relative movement between the valve plunger 74 and the power piston main body 54. The relay member 90 is integrally fitted with the output rod 94, and the stepping force applied to the brake pedal 10 is boosted by the booster 12 and is output from the output rod 94 to operate the master cylinder 14.

A limit switch 96 is attached to the input rod 82 as shown in FIG. The limit switch 96 is still ON with the lever 98 still separated from the valve element 78 when the valve element 78 is seated on both the first valve seat and the second valve seat 76. When 10 is stepped on and the input rod 82 is advanced, the lever 98 is engaged with the valve element 78 and turned off.

Further, as shown in FIG. 3, the booster 12 is provided with an opening / closing valve for controlling connection and disconnection of the constant pressure chamber 42 and the variable pressure chamber 44.
100 are provided. The space inside the housing 102 of the on-off valve 100 is divided into two by a partition plate 104, one chamber 106 is made to communicate with the constant pressure plate 42 by a pipe line 108, and the other chamber 110 is made a pipe line 112, a synthetic resin. The variable pressure chamber 44 is communicated with a passage 116 formed in a block 114 made of steel.
A small-diameter through hole 118 is formed in the center of the partition plate 104 to connect the two chambers 106 and 110 to each other, and a metal valve 120 disposed in the chamber 110 is seated in the opening of the through hole 118 on the chamber 110 side. By being separated from each other, the chambers 106 and 110 communicate with each other and are shut off from each other.
The valve element 120 is held slidably in the axial direction by the block 114, and is biased by a spring 122 in such a direction as to be seated in the opening of the through hole 118, around which a solenoid 124 is arranged. There is. The solenoid 124 is always demagnetized so that the valve element 120 blocks communication between the chambers 106 and 110. In addition, when the solenoid 124 is excited, the valve element 120 is penetrated by the solenoid 124.
Separated from 118, the chambers 106 and 110 and thus the constant pressure chamber 42
And the transformer room 44 are communicated with each other.

In the present embodiment, the pipes 108, 112 and the passage 116 form a communication passage that connects the constant pressure chamber 42 and the variable pressure chamber 44, and the partition plate 104 having the through hole 118 of the opening / closing valve 100 forms a throttle. Of.

The braking device configured as described above is controlled by the controller 130 shown in FIG. The controller 130 is mainly composed of a computer including a CPU (central processing unit) 132, a ROM (read only memory) 134, and a RAM (random access memory) 136, as shown in FIG. To the controller 130, rotation sensors 138 and 140 that detect the rotation of the front wheels 16 and 18, a brake switch 144 that detects that the brake pedal 10 is stepped on, and the limit switch 96 are connected. The controller 130 is provided with an arithmetic unit that processes the signals sent from the rotation sensors 138 and 140 to calculate the vehicle speed. CP
The U132 is provided with a timer 145, and the RAM 136 is provided with first and second vehicle speed memories 146, 147 and first and second deceleration memories 148, 149. In addition, the 6th in ROM134
The program shown by the flowchart in the drawing is stored, and the CPU 132 performs processing in accordance with the program to control the wheel cylinder hydraulic pressure.

Hereinafter, the operation of the braking device configured as described above will be described.

When the brake pedal 10 is not depressed, the second valve seat 76 is in contact with the valve element 78 and is separated from the first valve seat 72, as shown in FIG.
The variable pressure chamber 44 is communicated with the constant pressure chamber 42, and both chambers 42 and 44 are kept at the same negative pressure and there is no pressure difference. for that reason,
The power piston body 54 is urged toward the input rod 82 by the elastic force of the return spring 46, and the stopper plate
86 is brought into contact with the inner surface of the case 34.

When the brake pedal 10 is stepped on from this state and the input rod 82 is advanced, the first valve seat 72 contacts the valve element 78, and then the second valve seat 76 moves the valve element 78.
Away from, the variable pressure chamber 44 is separated from the constant pressure chamber 42 and communicates with the atmosphere. As a result, a pressure difference is generated between the variable pressure chamber 44 and the constant pressure chamber 42 into which the atmosphere flows, and the force based on this causes the power piston 36 to move forward. Power piston
36 moves output rod via reaction disk 92
It is transmitted to 94 and thrust is added. As a result, the brake fluid in the master cylinder 14 is transferred to the wheel cylinders 20, 22, 28, 30.
The rotation of the wheels is suppressed. At this time, the input rod 82 plays a part of the brake reaction force applied to the output rod 94 (the magnitude thereof is determined by the area ratio of the contact surface between the valve plunger 74 and the power piston main body 54 with respect to the reaction disc 92). Therefore, the stepping force applied to the input rod 82 is boosted and transmitted to the output rod 94.

When the wheel rotation is suppressed as described above, the controller 130 controls the brake fluid pressure of each wheel cylinder 20, 22, 28, 30 according to the flowchart shown in FIG. In step S1 (hereinafter, simply referred to as S1; the same applies to other steps), it is determined whether or not the brake pedal 10 is depressed. Whether or not the brake pedal 10 is depressed is determined by the signal emitted by the brake pedal switch 144. While the brake pedal 10 is not depressed, S1 is repeated,
When stepped on, S2 is executed and it is determined whether or not the timer 145 has finished the timekeeping operation for a predetermined short time, for example, 10 ms. Initially, since the timer 145 is in the state where the time counting operation is finished, the result of this determination is YES and S3
At 154, the timer 145 starts the time counting operation.

Subsequently, in S4, the vehicle speed v is fetched and stored in the first vehicle speed memory 146. Then, in S5, it is determined whether or not this vehicle speed acquisition is the first time, but initially, the result of this determination is YES, and S2 to S4 are executed again. The second vehicle speed acquisition is performed within a certain short time after the first vehicle speed acquisition. At this time, the first vehicle speed stored in the first vehicle speed memory 146 is transferred to the second storage memory 147, and the newly captured vehicle speed is stored in the first vehicle speed memory 146. The result of the determination in S5 executed after the second vehicle speed acquisition is NO, so S6 is executed, and the difference between the vehicle speeds stored in the first and second vehicle speed memories 146 and 147 is the fixed time. The deceleration α is calculated by dividing by (10ms), and the first deceleration memory 14
8 remembered. After that, in S7, it is determined whether or not the deceleration α is calculated for the first time. Initially, the result of this determination is YES, and S2 to S6 are executed again. The second deceleration α is calculated based on the second and third vehicle speeds stored in the first and second vehicle speed memories 146 and 147. The first deceleration α stored in 148
Is transferred to the second deceleration memory 149, and the newly calculated deceleration α is stored in the first deceleration memory 148.

The result of the judgment of S7 performed after the second deceleration calculation is
Since it becomes NO, the latest deceleration α stored in the first deceleration memory 148 in S8 is the reference deceleration set in advance.
It is judged whether or not it is 0.5 g or less. The result of the judgment is
If the value is NO, it means that the vehicle is in a sudden braking state, S17 is executed, the on-off valve 100 is kept closed, and the master cylinder 14 is boosted.
Activated by a force boosted by 12. Thereafter, in S18, it is repeatedly determined whether or not the depression of the brake pedal 10 is released, and when the depression is released, the program execution returns to S1. S9 during sudden braking
~ S16 is bypassed, and the swing-back prevention control is not performed.

On the other hand, if it is determined in S8 that the deceleration α is 0.5 g or less, the change in the deceleration α (α _n and α stored in the first and second deceleration memories 148 and 149) is determined in S9.
_It is determined whether or not the (difference from _n + ₁ ) is below a certain value, for example, 0.01 g or less. And the result of this judgment is
If it becomes NO, the deceleration α is not yet stable,
It means that it is early to enter the anti-sway control,
Program execution returns to S2. In addition, the judgment result is YES
If it becomes, it means that the deceleration α is stable, and S1
0 is executed.

In S10, it is determined whether or not the deceleration α is 0. If the determination result is NO, that is, if the deceleration α is 0, the brake pedal 10 is depressed while the vehicle is stopped. Or the vehicle has changed from a decelerating state to a constant speed running state, and the program following S11 is not executed and the process returns to S1. As a result, the program below S11 is executed and the on-off valve 100
Is prevented from being opened, and the execution of the program is stopped when the brake pedal 10 that has been stepped on is released midway.

If the determination result in S10 is YES, it means that the brake pedal 10 is still depressed and the vehicle is in a stopped state, and S11 is executed. In S11, it is determined whether or not the latest vehicle speed v fetched in S4 is equal to or less than the reference vehicle speed obtained by multiplying the latest deceleration α calculated in S6 by a predetermined time constant T. Be seen. The value of the time constant T is set to, for example, 0.3 ≦ T ≦ so that the vehicle speed v can be smoothly reduced to 0 as shown in FIG. 7 and the traveling distance of the vehicle during that time can be relatively short.
It is selected from the range of 3. When the deceleration α is exponentially reduced from α ₁ to zero, the deceleration α is expressed by the following equation (1) α = α ₁ e ^{−t / T} (1), and this deceleration α There in order to also becomes zero at the same time the vehicle speed v becomes zero, it is necessary to start reducing the deceleration α of the vehicle speed v ₁ represented by the following formula (2), the vehicle speed v ₁ It is the standard vehicle speed.

Similarly, when the decelerations are α ₂ and α ₃ , the vehicle speeds are reduced to the reference vehicle speeds v ₂ and v ₃ in FIG. 7, respectively, and then the vehicle speeds are decreased along the solid line in FIG. At the same time, v becomes zero, and it is possible to prevent the swinging back. Above S1
The judgment in 1 is that the vehicle speed is deceleration such as α ₁ , α ₂ , α ₃ etc.
When it is decreasing linearly as shown by the thin line in the figure, it is a judgment as to whether or not it has decreased to the reference vehicle speed v ₁ , v ₂ , v ₃ etc., and the judgment result is NO Then, the program returns to S2, and S2 to S11 are repeatedly executed at regular intervals.

Then, when the vehicle speed v becomes equal to or lower than the reference vehicle speed v ₁ , v ₂ , v _3, etc., S12 is executed and the on-off valve 100 is opened. That is, the solenoid 124 is excited, the valve element 120 is attracted and separated from the opening of the through hole 118, and the constant pressure chamber 4 of the booster 12 is
2 and the transformer chamber 44 are communicated with each other, whereby the boost factor of the booster 12 is smoothly reduced. The area S of the through hole 118 is determined so as to satisfy the following expression (3), the pressure in the variable pressure chamber 44 is exponentially decreased, and the boost factor of the booster 12 is smoothly decreased. Yes, which causes the hydraulic pressure in the wheel cylinders 20, 22, 28, 30 to drop exponentially.

However, V ₀ : Volume of the variable pressure chamber 44 C: Flow coefficient At this time, the driver usually keeps the brake pedal operating force constant, so as the booster 12 boost factor decreases, the master cylinder The brake pedal 10 is gently pushed back by the reaction force from the 14 side. As a result, the driver can confirm that the wheel cylinder hydraulic pressure has been reduced and the swing-back prevention control is being performed.

If the driver continues to apply a constant treading force to the brake pedal 10, the master cylinder hydraulic pressure does not decrease to 0 even if the brake booster 12 does not function as a booster.
Although a slight rebound will occur, the extent is very small and there is no practical problem.

After the opening / closing valve 100 is opened in S12, it is determined in S13 whether or not the depression amount of the brake pedal 10 is increased, that is, whether or not the vehicle is in a state requiring a braking force larger than the current braking force. If the depression amount of the brake pedal 10 increases, the input rod 82 and the valve element
There is relative movement between 78 and the limit switch 96
Is detected by the
S17 is executed. Solenoid 124 is demagnetized to open / close valve 10
When 0 is closed, the booster 12 returns to a state where the brake fluid pressure corresponding to the operating force boosted is obtained.

If it is determined in S13 that the brake pedal 10 has not been further increased, the brake pedal 10 is determined in S14.
It is determined whether or not the stepping on is released. The determination result being YES means that the brake pedal 10 is released after the opening / closing valve 100 is opened, and S17 is executed to close the opening / closing valve 100. on the other hand,
If the determination result in S14 is NO, the brake pedal 10 is still depressed and the vehicle is in a braking state.
After the vehicle speed v is captured in 5, it is determined in S16 whether the captured vehicle speed v is zero. If the determination result is NO, the process returns to S13. S13 to S16 are repeatedly performed until the vehicle speed v becomes zero, and a situation in which a large braking force is required until the vehicle completely stops, or braking is released and the vehicle enters a constant speed or acceleration running state. When this happens, the on-off valve 100 is returned to its original closed state. Then, when the vehicle speed v becomes zero, S17
Is executed and the on-off valve 100 is closed, S18 is repeatedly executed and the operation of the brake pedal 10 is released, and then the program execution returns to S1.

As is clear from the above description, in this embodiment, S2 of the flow chart shown in FIG.
~ S7 storage area, CPU132, the first and second vehicle speed memory 146, 147 constitutes the deceleration detection means, R
The opening / closing valve control means is constituted by the area for storing S8 to S18 in the flow chart of the OM134, the CPU 132, and the first and second deceleration memories 148, 149.

Thus, in the brake device of the present embodiment, the deceleration α is smaller than the predetermined reference deceleration (0.5 g),
In addition, the booster 12 has a stable power factor, and when the vehicle speed v becomes equal to or lower than the reference vehicle speed set on the basis of the deceleration α, the booster 12 has a boosting factor reduced and the wheel cylinder hydraulic pressure is exponentially reduced. As a result, the deceleration is exponentially reduced, and when the vehicle speed v becomes zero and the vehicle is stopped, the change in the deceleration α becomes zero or very small, and the vehicle is stopped quietly without shaking. Will be done.

Also, the vehicle speed at which the swing-back control is started is determined based on the deceleration at each vehicle stop, so the wheel cylinder hydraulic pressure drops in an ideal pattern regardless of the deceleration of the vehicle. As a result, swingback is always prevented well.

As is clear from the above description, in the present embodiment, the brake pedal 10, the booster 12, the master cylinder 14,
A fluid pressure brake system is configured by the wheel cylinders 20, 22, 28, 30 and the like, and vehicle speed detection means is configured by the rotation sensors 138, 140 and a portion for calculating the vehicle speed of the controller 130.
Execution of S6 of the controller 130 constitutes a deceleration acquisition means according to the part. In addition, S11 of the controller 130
In the above, the portion for calculating the reference vehicle speed constitutes the reference vehicle speed determination means, and the on-off valve 100, the portion for determining S11 of the controller 130 and the portion for executing S12 constitute the decompression control means.

Another embodiment of the present invention is shown in FIGS. In this embodiment, the brake fluid pressure is exponentially reduced by using an anti-skid device that prevents the wheels from slipping into a skid state during braking.

In FIG. 8, 170 is a brake pedal, and the stepping force applied to the brake pedal 170 is boosted by the booster 172 to operate the master cylinder 174. The master cylinder 174 is provided with two pressurizing chambers independent of each other, and generates a hydraulic pressure of the same height in each pressurizing chamber based on the depression operation of the brake pedal 170. The hydraulic pressure generated in one pressurizing chamber is supplied to front wheel cylinders 180 and 182 of brakes provided on the left and right front wheels 176 and 178, respectively. The hydraulic pressure generated in the other pressurizing chamber is supplied to rear wheel cylinders 188 and 190 of the brakes provided on the left and right rear wheels 184 and 186, respectively.

An electromagnetic control valve 19 is provided in the middle of the main fluid passage connecting the master cylinder 174 and the front wheel cylinders 180 and 182.
2, 194 are provided so that the main liquid passage is the master cylinder side passage 196 and the wheel cylinder side passage 19.
It is divided into 8,199. Return passages 200 and 202 are connected between the master cylinder side passage 196 and the wheel cylinder side passages 198 and 199, respectively, and brake fluid from the wheel cylinder side passages 198 and 199 to the master cylinder side passage 196 is supplied to the return passages 200 and 202, respectively. Check valves 204 and 206 are provided that allow flow but block reverse flow.

A reservoir 210 is connected to the electromagnetic control valves 192 and 194 via a reservoir passage 208, and the brake fluid discharged from the front wheel cylinders 180 and 182 is changed by switching the electromagnetic control valves 192 and 194 to the rightmost state in the figure. It is designed to be stored in the reservoir 210. And
The brake fluid stored in the reservoir 210 is used as the check valves 212, 2
Pumped by pump 216 equipped with 14, hamp passage 2
It is supplied to the master cylinder side passage 196 via 18.

Although the front system has been described above, the rear system is also similar to the front system, including the electromagnetic control valve 224, the master cylinder side passage 226, the wheel side passage 228, the return passage 232, the check valve 234, the reservoir 236, the check valve 238, 240. And a pump 242. However, only one electromagnetic control valve 224 is provided on the rear side, the wheel cylinder side passage 228 is divided into two, and the brake fluid is divided into two after passing through the electromagnetic control valve 224, and is respectively divided into the rear wheel cylinders 188 and 190. It is being supplied.

The brake fluid pumped by the pumps 216 and 242 respectively provided in the front system and the rear system is supplied to the front wheel cylinders 180 and 182 and the rear wheel cylinders 188 and 190 when the electromagnetic control valves 192, 194 and 224 are switched to the leftmost state in the figure. To be done. In this embodiment, the pumps 216 and 242 form a power hydraulic pressure source separate from the master cylinder 174.

Further, the rotation speeds of the left and right front wheels 176 and 178 are detected by the sensors 246 and 248, respectively, and the rotation speeds of the rear wheels 184 and 186 are detected by the sensor 250, and the detection signals thereof are supplied to the controller 252. Controller 252
Calculates the slip ratio of each wheel based on the detection signals from these sensors, and based on the result, the electromagnetic control valve 192,
It is designed to control 194,224. Controller 252
Are electromagnetic control flights 192, 194, 224, reservoirs 210, 236, pumps 216,
It constitutes the anti-skid device with 242 etc. The controller 252 also includes a brake pedal 1
A brake switch 254 for detecting the depression of 70 is connected. The booster 172 has the same structure as the booster 12 except that the on-off valve 100 is not provided, and detailed description thereof will be omitted.

Hereinafter, the operation of the anti-skid device will be representatively described for the system of the front wheels 176. Normally, as shown in the figure, the electromagnetic control valve 192 is in a pressurization permitting state in which the hydraulic pressure of the front wheel cylinder 180 is permitted to rise, and the master cylinder 174 and the front wheel cylinder 180 are in communication with each other. Therefore, when the brake pedal 170 is depressed, the brake fluid discharged from the master cylinder 174 is supplied to the front wheel cylinder 180, and as a result, the brake operates and the front wheel 176 is braked.

When the depression force of the brake pedal 170 is low in relation to the friction coefficient of the road surface, the slip ratio of the front wheels 176 is low, so the controller 252 does not operate. But,
When the stepping force of the brake pedal 170 is large in relation to the friction coefficient of the road surface, the slip ratio of the front wheels 176 increases beyond the proper range, and the controller 252 causes the sensor 2
By detecting the fact based on the detection signal from 46, the solenoid of the solenoid control valve 192 is supplied with current to make the solenoid control valve 192 in the cut-off state shown in the center of the figure or the step-down allowance shown on the right side. While switching to the state (state that allows the hydraulic pressure of the wheel cylinder to drop),
The drive motor of the pump 216 is started.

When the solenoid control valve 192 is switched to the shut-off state, the front wheel cylinder 180 shifts the master cylinder 174.
The hydraulic pressure is kept constant, and the braking force on the front wheels 176 is kept constant. Further, even if the pump 216 is activated, the reservoir 210
Since the brake fluid is not stored in, the brake fluid is not pumped.

On the other hand, when the electromagnetic control valve 192 is switched to the pressure reduction allowable state, the front wheel cylinder 180 moves the reservoir 210
The brake fluid is discharged from the front wheel cylinder 180 and stored in the reservoir 210. The brake fluid stored in the reservoir 210 is pumped up by the pump 216 and returned to the master cylinder side passage 196.

As a result of the hydraulic pressure of the front wheel cylinder 180 being reduced as described above, if the slip ratio of the front wheels 176 decreases to a predetermined constant value, the controller 252 recognizes that fact and controls the electromagnetic control valve 192. Switch to the cut-off state or the boosting allowable state. When switched to the cutoff state, the hydraulic pressure of the front wheel cylinder 180 is kept constant, but when switched to the pressure increase allowable state, brake fluid is supplied from the master cylinder 174 and the hydraulic pressure of the front wheel cylinder 180 rises. To be made.

The above control is repeated in a relatively short time, whereby the hydraulic pressure of the front wheel cylinder 180 is properly controlled, and the slip ratio of the front wheel 176 is kept in the proper range.

Preventing vehicle skids with this anti-skid device
This is done when the pedaling force of the brake pedal 10 is relatively large.
The anti-skid device will not operate if the vehicle is gently stopped. Therefore, in this embodiment, the anti-skid device is also made to perform the swing-back prevention control.

The controller 252 is similar to the controller 130.
The CPU is mainly composed of a computer including a ROM, a RA, and the RAM is provided with a first and a second vehicle speed memory and a deceleration memory like the RAM 136, while the ROM is a ninth memory.
A plurality of types of programs and deceleration patterns for exponentially decreasing the wheel cylinder hydraulic pressure shown in the flowchart of the drawing are stored according to each deceleration, and the CPU performs processing in accordance with the program.

In this flowchart, steps S101 to S111 are the same as those in the above embodiment, and detailed description thereof will be omitted.
If the determination result in S111 is YES, the vehicle speed v and the target vehicle speed are acquired in S112. This target vehicle speed is S109
Is obtained from the deceleration pattern selected based on the deceleration α that is determined to be substantially constant in S111, and the vehicle speed v is captured based on the time measured from when the determination result in S111 is YES. The corresponding vehicle speed is sometimes taken in as the target vehicle speed. In subsequent S113, it is determined whether the taken vehicle speed v is higher than the target vehicle speed. If the determination result in S113 is YES, the actual vehicle speed v is higher than the target vehicle speed, so a pressure increase instruction is issued in S114 and the electromagnetic control valve 19
The supply of current to the 2,194,224 solenoids is cut off, and the pressure is allowed to be increased to increase the braking force.

Further, if the determination result in S113 is NO, it is determined in S115 whether or not the actual vehicle speed v is lower than the target vehicle speed, and if it is small, the braking force is too large.
A pressure reduction instruction is issued in S116. Solenoid control valve 192,194,
The 224 is switched to the step-down allowable state. Further, when the determination result in S115 is NO, it means that the vehicle speed v is the same as the reference speed, and in S117, the holding instruction is issued, the electromagnetic control valve is shut off, and the wheel cylinder hydraulic pressure is set. Is kept constant.

Whichever of S114, 116, 117 is executed, S118 is subsequently executed to determine whether or not the brake pedal 170 is further pressed. If the pedal is further pressed, a large braking force is required, so S122 is executed and the solenoid control valves 192, 194, 224 are set to the pressurization allowable state. If the pedal is not pressed further, the brake pedal is pressed in S119.
A determination is made as to whether 170 has been released. Here, if the operation of the brake pedal 170 is released, S122 is executed, the electromagnetic control valves 192, 194, 224 are switched to the pressurization allowable state, and the brake pedal 170 is still maintained.
If is depressed, the vehicle speed v is fetched in S120, and then it is determined in S121 whether or not the vehicle speed v is 0. If it is not 0, the program is executed in S112.
Then, the process up to S121 is repeated. The actual vehicle speed v is compared with the target vehicle speed obtained from a predetermined deceleration pattern, and the wheel silling hydraulic pressure is appropriately increased.
It is held and lowered so as to decrease exponentially as a whole according to the deceleration pattern.

Then, if the determination result in S121 is YES, S122 is executed, and the solenoids of the electromagnetic control valves 192, 194, 224 are demagnetized by the pressure increase instruction, and the pressurization allowable state is set. After that, after it is confirmed in S123 that the operation of the brake pedal 170 is released, the program execution returns to S101.

As is clear from the above description, in this embodiment, the brake pedal 170, the booster 172, the master cylinder 17
4, a fluid pressure brake system is configured by the wheel cylinders 180, 182, 188, 190, etc., vehicle speed detection means is configured by the sensors 246, 248, 250 and a portion for calculating the vehicle speed of the controller 252, and deceleration acquisition means by the portion executing S106 of the controller 252. It is configured. Further, the reference vehicle speed determination means is configured by the portion that calculates the reference vehicle speed in S111 of the controller 252, and the depressurization control means is constituted by the electromagnetic control valves 192, 194, 224 and the portion that determines S111 of the controller 252 and the portion that executes S112 to S117. It is configured.

In the present embodiment, the wheel cylinder hydraulic pressure is exponentially reduced by the antiskid device of the type in which the brake fluid pumped from the reservoirs 210, 236 is returned to the master cylinder 174.
It is also possible to control the wheel cylinder hydraulic pressure exponentially by another type of anti-skid device, such as an anti-skid device in which the master cylinder is disconnected from the wheel cylinder during operation of the anti-skid device. .

In addition, traction control that prevents slipping of the wheels when the vehicle starts, braking effect control that always obtains a braking effect that corresponds to the depression force of the brake pedal, regardless of fluctuations in the friction coefficient of the brake friction material. It is also possible to use the power hydraulic pressure source and electromagnetic control valve that are provided for the control to perform the swing back prevention control, and it is also possible to provide a power hydraulic pressure source and solenoid control valve dedicated to the swing back prevention. It is possible. In short, the fluid pressure brake system includes a master cylinder that generates hydraulic pressure in response to depression of the brake pedal, and a brake cylinder that operates with the hydraulic pressure of the master cylinder, and the depressurization control means is the master cylinder. A separate power hydraulic pressure source, a reservoir, an electromagnetic control valve for selectively communicating the brake cylinder with the power hydraulic pressure source and the reservoir, and an exponential function of the brake cylinder hydraulic pressure by controlling the electromagnetic control valve. What is necessary is just to include the electromagnetic control valve control means for reducing

In addition, although not exemplified, the present invention can be implemented in various modified and improved modes based on the knowledge of those skilled in the art.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing a configuration of a vehicle brake device according to the present invention. FIG. 2 is a system diagram of a vehicle brake device according to an embodiment of the present invention. FIG. 3 is a front sectional view showing a booster of the brake device. FIG. 4 is a front sectional view showing the vicinity of the control valve in the booster. FIG. 5 is a block diagram showing a computer which is the main body of the controller of the brake device, and FIG. 6 is a flowchart of a program stored in the ROM of the controller. FIG. 7 is a graph showing a state of vehicle speed control in the brake device. FIG. 8 is a system diagram of a vehicle brake device according to another embodiment of the present invention, and FIG. 9 is a flowchart of a program stored in the ROM of the controller of the brake device. 10: Brake pedal, 12: Booster 14: Master cylinder 20, 22: Front wheel cylinder 28,30: Rear wheel cylinder 100: Open / close valve, 118: Through hole 120: Valve, 124: Solenoid 130: Controller, 170: Brake Pedal 174: Master cylinder 180,182: Front wheel cylinder 188,190: Rear wheel cylinder 192,194,224: Electromagnetic control valve 246,248,250: Sensor 252: Controller

Claims (3)

(57) [Claims] 1. A fluid pressure brake system for suppressing rotation of wheels of a vehicle in response to depression of a brake pedal, vehicle speed detection means for detecting vehicle speed of the vehicle, and a fluid pressure brake system in response to depression of the brake pedal. Deceleration acquisition means for acquiring the deceleration of the vehicle caused by the action of, and reference vehicle speed determination means for determining the reference vehicle speed based on the deceleration acquired by the deceleration acquisition means and a predetermined time constant. And, after the vehicle speed detected by the vehicle speed detecting means is reduced to the reference vehicle speed, the fluid pressure of the fluid pressure brake system is set to the time constant regardless of the depression force of the brake pedal being kept constant. And a decompression control means for reducing the deceleration to zero at the same time as reducing the vehicle speed to zero by exponentially lowering the vehicle break. Apparatus. 2. The fluid pressure brake system includes a booster for boosting the depression force of the brake pedal, the booster having a power piston that operates based on a pressure difference between a constant pressure chamber and a variable pressure chamber, and The decompression control means, a communication passage for communicating the constant pressure chamber and the variable pressure chamber of the booster through a throttle, an on-off valve that always shuts off the communication passage, and the on-off valve, the vehicle speed up to the reference vehicle speed The vehicle brake device according to claim 1, further comprising an opening / closing valve control means that opens after the temperature has dropped. 3. The fluid pressure brake system includes a master cylinder that generates hydraulic pressure in response to depression of the brake pedal, and a brake cylinder that operates with hydraulic pressure of the master cylinder, and The reduction control means controls a power hydraulic pressure source separate from the master cylinder, a reservoir, an electromagnetic control valve for selectively communicating the brake cylinder with the power hydraulic pressure source and the reservoir, and the electromagnetic control valve. The vehicle brake system according to claim 1, further comprising: an electromagnetic control valve control unit that exponentially lowers the hydraulic pressure of the brake cylinder.