JPH09323634A - Master cylinder pressure estimating device and wheel cylinder pressure estimating device using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To precisely estimate both cylinder pressures without measuring means by setting a master cylinder pressure estimated value, reducing the master cylinder pressure estimated value when the feed hydraulic pressure to a wheel cylinder is intensified, and increasing the master cylinder pressure estimated value when the feed hydraulic pressure is reduced. SOLUTION: An electronic control device 80 performs the initial set of the master cylinder pressure estimated value of a master cylinder 14, and also performs its correction and estimation. The wheel cylinder pressure of each wheel cylinder 26, 36, 46, 56 is estimated by use of the estimated master cylinder pressure. Namely, after the lapse of a prescribed time from braking start, the master cylinder pressure is estimated. When it is judged that the wheel cylinder pressure is intensified, the master cylinder pressure estimated value is reduced in proportion to the predicted intensified quantity of the wheel cylinder pressure at that time, and intensified contrarily when the feed hydraulic pressure to the wheel cylinder is reduced. The master cylinder pressure can be thus precisely estimated according to intensification and reducing of the wheel cylinder pressure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a master cylinder pressure estimating device and a wheel cylinder pressure estimating device using the same.

[0002]

2. Description of the Related Art Conventionally, an anti-skid brake system (ABS) has been developed in order to ensure vehicle stability and steerability during sudden braking. This controls the hydraulic pressure generated by the master cylinder of the braking device and supplied to the wheel cylinders according to the running state of the vehicle, so that excessive braking force is not applied to the wheels and the wheels are locked. To do.

In order to properly perform this increase / decrease control by the hydraulic pressure control device, it is important to accurately detect or estimate the master cylinder pressure and the wheel cylinder pressure.

For example, in JP-A-5-502423, a target braking fluid pressure (target wheel) of a braking device is controlled by PI feedback control based on a deviation between a target slip and an actual slip obtained from a wheel speed, a vehicle body speed and the like. A method for obtaining a cylinder pressure) is disclosed. Further, there, the opening / closing time of the anti-skid hydraulic pressure control valve is calculated from the target braking hydraulic pressure, the master cylinder pressure, and the lateral force based on the reverse hydraulic pressure model, and the opening / closing of the valve is controlled. ing.

[0005]

However, in the conventional anti-skid brake system including the one disclosed in the above Japanese Patent Publication No. 5-502423, the target braking hydraulic pressure, which is an index of control, is set to the target slip, Since it is directly calculated from parameters such as wheel speed or vehicle body speed, it has not been possible to realize more precise and comprehensive control according to the motion characteristics of the vehicle.

For example, in the control device disclosed in the above Japanese Patent Publication No. 5-502423, when the valve opening / closing time of the actuator is calculated using the reverse hydraulic model, a simple orifice is assumed as the valve model, Although the valve opening / closing time is calculated by various models, control accuracy cannot be secured in an actual hydraulic system without considering changes in pipe rigidity. Further, the control device has a problem that it cannot be controlled with sufficient accuracy because it is not calculated by a dynamic model considering the vehicle motion, the gain and phase of the actuator, the hydraulic characteristic, and the like.

On the other hand, the applicant previously filed Japanese Patent Application No. 7-5.
No. 4474, means for measuring the master cylinder pressure,
A method for estimating the wheel cylinder pressure from the history of increase / decrease control of the master cylinder pressure and the wheel cylinder pressure measured by the measuring means, constantly grasping the estimated value of the wheel cylinder pressure, and controlling the wheel cylinder pressure appropriately is provided. Proposed.

The present invention has been made in view of the above conventional problems, and is to improve the above-mentioned prior application by the present applicant to accurately estimate the master cylinder pressure and the wheel cylinder pressure without providing measuring means. It is an object of the present invention to provide a master cylinder pressure estimation device capable of achieving the above and a wheel cylinder pressure estimation device using the same.

[0009]

SUMMARY OF THE INVENTION The invention described in claim 1 is, as shown in FIG. 1 (A) in its gist, a hydraulic pressure generated by a master cylinder of a braking device and supplied to a wheel cylinder, In a master cylinder pressure estimation device equipped with a hydraulic control device for increasing / decreasing control according to a running state of a vehicle, initial setting means for uniformly setting a master cylinder pressure estimated value after a braking operation by a predetermined arithmetic expression for a predetermined period. After the lapse of the predetermined period of time and after the start of the increase / decrease control, when the hydraulic pressure supplied to the wheel cylinder is about to be increased by the hydraulic pressure control device, the amount of increase in pressure is estimated according to the expected increase amount. When the master cylinder pressure estimated value is reduced and corrected, and when the hydraulic pressure supplied to the wheel cylinder is about to be reduced, the master cylinder pressure estimation is performed according to the expected reduction amount. By having a master cylinder pressure correcting and estimating means for increasing the correction value is obtained by solving the above problems.

The invention described in claim 7 is, as shown in FIG. 1 (B), in which the hydraulic pressure generated by the master cylinder of the braking device is supplied to the wheel cylinders.
In a wheel cylinder pressure estimation device including a hydraulic pressure control device that controls increase / decrease in accordance with a running state of a vehicle, the estimated master cylinder pressure value estimated in claim 1 after the increase / decrease control is started, and the estimated value in claim 1 By providing a means for estimating the next wheel cylinder pressure based on the amount of increase or decrease of the hydraulic pressure supplied to the wheel cylinder,
This is a solution to the above problem.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment is claim 1.
In the invention described in (1), the expected pressure reduction amount when the hydraulic pressure supplied to the wheel cylinder is about to be reduced is approximated only by the wheel cylinder pressure at that time. Is. Generally, the amount of reduction of the wheel cylinder pressure is determined depending on the wheel cylinder pressure, the hydraulic pressure of the reservoir, the conduit resistance (of the conduit from the wheel cylinder to the reservoir), etc. It can be approximately calculated from only. As a result, the pressure reduction amount can be easily calculated, and the master cylinder pressure can be estimated accordingly.

In another preferred embodiment, in the invention described in claim 1, the vehicle deceleration is controlled after the predetermined period has elapsed and before the increase / decrease control of the hydraulic pressure supplied to the wheel cylinder is started. It is used to correct and estimate the master cylinder pressure.

In another preferred embodiment, in the invention described in claim 1, the wheel cylinder pressure is actually estimated at that time after the elapse of the predetermined time and before the start of the increase / decrease control. It is to be estimated to be equal to the existing master cylinder pressure.

When the increase / decrease control is not entered even after a lapse of a predetermined period after the braking operation, the master cylinder pressure is not reduced because the weak braking state (without slip) is considered, and therefore the wheel cylinder pressure is the master cylinder pressure. It is considered that the pressure is almost the same as the pressure. In addition, the wheel cylinder pressure when there is no slip should uniquely correspond to the vehicle deceleration in accordance with the load applied to the wheels.

Therefore, the other preferred embodiment described above is
Based on these principles, if the increase / decrease control is not entered even after the lapse of a predetermined period after the braking operation, it is assumed that the master cylinder pressure is equal to the wheel cylinder pressure, and the wheel cylinder pressure, that is, the master cylinder pressure is corrected and estimated from the vehicle deceleration. To do.
This makes it possible to easily estimate the master cylinder pressure and improve the estimation accuracy of the master cylinder pressure even after the increase / decrease control is started.

Further, in another preferred embodiment, in the same invention as set forth in claim 1, the initial setting means uses a function increasing with respect to a braking operation time as the predetermined arithmetic expression. That is.

Thus, it is possible to easily perform highly accurate estimation by selecting an appropriate increasing function such as a function simulating the pressure increasing gradient of the master cylinder pressure at the time of a normal driver's sudden braking operation.

Further, in another preferred embodiment, in the invention described in claim 1 as well, a master cylinder pressure sensor for detecting an actual master cylinder pressure is provided, and the master cylinder pressure is estimated based on the master cylinder pressure estimated value. That is, the abnormality determination of the pressure sensor is performed.

As a result, even if a defect occurs in the actual master cylinder pressure detecting means (master cylinder pressure sensor), the master cylinder pressure estimating device backs up the defect so that the proper master cylinder pressure estimated value can always be grasped. can do. As a result, it is possible to accurately estimate the wheel cylinder pressure and perform appropriate vehicle control.

Hereinafter, more specific embodiments will be described in detail with reference to the drawings.

FIG. 2 is a schematic diagram showing a master cylinder pressure estimating apparatus to which the present invention is applied and a wheel cylinder pressure estimating apparatus using the same.

FIG. 2 shows a diagonal two-system braking system.

In FIG. 2, when the brake pedal 10 is stepped on, the booster (boost device) 12 amplifies the pedaling force,
As a result, the piston of the master cylinder is operated, and the master cylinder 14 generates hydraulic pressure (master cylinder pressure). Two brake fluid passages 20 from the master cylinder 14.
And 40 extend. The brake fluid passage 20 is divided into two brake fluid passages 24 and 34, the brake fluid passage 24 is connected to the wheel cylinder 26 of the left rear wheel RL, and the brake fluid passage 34 is connected to the wheel cylinder 36 of the right front wheel FR. . The brake fluid passage 40 has two brake fluid passages 44.
And 52, the brake fluid passage 44 is connected to the wheel cylinder 46 of the left front wheel FL, and the brake fluid passage 52 is connected to the wheel cylinder 54 of the right rear wheel RR. The master cylinder pressure generated by the master cylinder 14 is transmitted to each wheel cylinder 26, 36, 46, 54 through these brake fluid passages 24, 34, 44, 52.

Pumps 66 and 74 are provided in the brake fluid passages 20 and 40, respectively. The pump 66 pumps the brake fluid from the reservoir 64, and the pump 74 pumps the brake fluid from the reservoir 72. Also, the pump 66
And 74 are driven by a motor 76.

Switching valves 22, 34 and control valves 60, 62 are provided between the brake fluid passages 20 and 34.
Further, switching valves 42, 5 are provided between the brake fluid passages 40 and 52.
0 and control valves 68, 70 are provided.

The hydraulic pressure control device 78 is constructed as described above.

Wheel speed sensors 100, 102, 104 and 106 are provided on the wheels RL, FR, FL and RR, respectively. Wheel speed sensors 100, 102, 10
The signals 4, 106 are sent to the electronic control unit 80. or,
The depression of the brake pedal 10 is detected by the brake switch 110.

The electronic control unit 80 initializes the master cylinder pressure estimated value and corrects / estimates the master cylinder pressure. The electronic control unit 80 also estimates the wheel cylinder pressure using the estimated master cylinder pressure. Further, the electronic control unit 80 determines the slip of the wheel by a known method, and when it is determined that the wheel is slipping, performs the braking hydraulic pressure control represented by the known ABS control (anti-skid brake control). This braking hydraulic pressure control corresponds to the increase / decrease control of the hydraulic pressure (wheel cylinder pressure) supplied to the wheel cylinder 46 of claim 1.

The operation of this embodiment will be described below with reference to the flow charts of FIGS. 3 and 4.

In step 100 of FIG. 3, the start of the brake operation is detected by the signal from the brake switch 110. The brake operation starts with each wheel speed sensor 100,
Alternatively, the decrease in wheel speed may be detected by detecting the signals from 102, 104, and 106.

If the brake operation has not been started yet, in step 110, the electronic control unit 80 initializes the set values used for various controls. At this time, the counter Tafter indicating the elapsed time from the detection of the start of the brake operation is also cleared to zero.

When the start of the brake operation is detected, the process proceeds to the next step 120 and the counter Tafter is incremented.

In the next step 130, it is determined whether or not ABS control is in progress. If ABS control is in progress, the process proceeds to step 210 in FIG. Immediately after starting the brake operation, it is still AB
Since the S control has not been entered, the routine proceeds to the next step 140.
In step 140, it is determined whether or not a predetermined time has elapsed from the start of the brake operation. This determination is made based on whether or not the counter Tafter has exceeded a predetermined value FBT (Fast Brake Time). If the counter Tafter does not exceed the predetermined value FBT, the master cylinder pressure estimated value is initialized in the next step 150.

This initial setting is shown in FIG. 5 simulating the pressure increasing gradient of the master cylinder pressure when a normal driver performs a sudden braking operation.
Based on the graph shown in (1), the pressure increase gradient Pgrad, the elapsed time Tafter from the start of the brake operation, and the constant Pconst are set by the following equation (1).

Pme = Pgrad × Tafter + Pconst (1)

In the next step 160, the master cylinder pressure estimated value Pme is guarded in order to prevent the master cylinder pressure estimated value Pme from being abnormally high. That is, the master cylinder pressure estimated value Pme is equal to the predetermined value Pme.
If it is smaller than max1, the master cylinder pressure estimated value Pme
Is a predetermined value Pmemax1 and the master cylinder pressure estimated value Pme
Is larger than the predetermined value Pmemax2, the master cylinder pressure estimated value Pme is set to the predetermined value Pmemax2. As a result, the master cylinder pressure estimated value Pme becomes two predetermined values Pmemax1 and Pmemax1.
Regulated during memax2. These predetermined values are, for example,
Values such as Pmemax1 = 1.5 Mp and Pmemax2 = 20 Mp are selected.

In the next step 170, using the previous master cylinder pressure estimated value Pme (n-1) and the wheel cylinder pressure estimated value Pwe (n-1), the current wheel cylinder is calculated from the following equation (2). The estimated pressure value Pwe (n) is determined.

Pwe (n) = Pwe (n−1) + Ciw × (Pme (n−1) −Pwe (n−1)) ^1/2 (2) where Ciw is a predetermined coefficient.

When it is determined in step 140 that the predetermined time FBT has elapsed from the start of the brake operation, the routine proceeds to step 180, where the master cylinder pressure is estimated. In this way, when the ABS control is not entered even after the lapse of the predetermined time FBT from the start of the brake operation, it is considered that the vehicle is in the weak braking state (the wheels are not locked, that is, the grip state). In the weak braking state, the wheel cylinder pressure is not reduced and is considered to be almost the same as the master cylinder pressure. Further, since the wheels are not locked, that is, the wheel cylinder pressure in the grip state is considered to uniquely correspond to the vehicle deceleration according to the load applied to the wheels,
The wheel cylinder pressure, that is, the master cylinder pressure can be estimated from the vehicle deceleration. FIG. 6 shows the vehicle deceleration D.
6 is a graph showing a relationship between vve and a master cylinder pressure estimated value (= wheel cylinder pressure estimated value) Pme. The vehicle deceleration Dvve is the wheel speed sensor 100, 102, 104, 10
The signal from 6 is constantly calculated by a known method. The vehicle deceleration Dvve here is obtained by smoothing the difference between the current and previous estimated vehicle speeds.

The method of estimating the wheel cylinder pressure (master cylinder pressure) before and after the predetermined time FBT from the start of the brake operation is changed because the brake pedal force increases before the predetermined time FBT. This is because it is estimated that the transition period of the master cylinder pressure is large, and under such a situation, the master cylinder pressure and the wheel cylinder pressure are not equal due to the influence of the conduit resistance from the master cylinder 14 to the wheel cylinder 26. .

Further, under the condition that the braking hydraulic pressure control is not started after the predetermined time FBT, it can be estimated that the change in brake pedal force is small and the master cylinder pressure and the wheel cylinder pressure are substantially equal to each other.

In the next step 190, the master cylinder pressure estimated value Pme is guarded as in step 160.

In step 200, the wheel cylinder pressure estimated value Pwe is set to the same value as the master cylinder pressure estimated value Pme just obtained for the above reason.

Next, a method of estimating the master cylinder pressure and the wheel cylinder pressure after the ABS control is started will be described with reference to the flowchart of FIG.

If it is determined in step 130 of FIG. 3 that ABS control is in progress, step 210 of FIG.
Proceed to. In step 210, the ABS control is performed to determine whether or not the wheel cylinder pressure is being increased (including a case where the pressure is about to be increased). When the pressure is not being increased, the routine proceeds to step 220, where it is determined whether or not the pressure is being reduced (including the case where the pressure is about to be reduced). If it is not under reduced pressure, it returns immediately. If the pressure is being reduced, the master cylinder pressure is estimated in the next step 230.

The frequency of wheel cylinder pressure reduction during ABS control is based on the physical phenomenon that the higher the master cylinder pressure, the higher the master cylinder pressure is, and is proportional to the (predicted) amount of wheel cylinder pressure reduction at that time. The estimated pressure value Pme is corrected and estimated. More accurately, the reduction of the wheel cylinder pressure is affected by the current hydraulic pressure of the wheel cylinder as well as the hydraulic pressure of the reservoir, the line resistance, and the like. It can be approximated as a quantity proportional to the square root of the wheel cylinder pressure. Therefore, the master cylinder pressure estimated value Pme (n) of this time depends on only the wheel cylinder pressure according to the following equation (3) with Cdm as a predetermined coefficient.
Is estimated by increasing.

Pme (n) = Pme (n-1) + Cdm × (Pwe (n-1)) ^1/2 (3)

In the next step 240, the master cylinder pressure estimated value Pme is guarded as in step 160.

In the next step 250, the estimated wheel cylinder pressure value Pwe (n) of this time is estimated by using the estimated wheel cylinder pressure value Pwe (n-1) of the previous time. This estimation is performed by the following equation (4) using Cdw as a predetermined coefficient.

Pwe (n) = Pwe (n-1) −Cdw × (Pwe (n-1)) ^1/2 (4)

On the other hand, when it is determined in step 210 that the wheel cylinder pressure is increasing, the routine proceeds to step 260, where the estimated master cylinder pressure value is reduced and corrected to obtain a new estimated master cylinder pressure value. That is, the master cylinder pressure estimated value Pme is decompressed and corrected by an amount proportional to the expected increase amount of the wheel cylinder pressure at that time. According to a test conducted by the present inventor, the expected increase amount of the wheel cylinder pressure can be approximated as an amount proportional to the square root of the difference between the master cylinder pressure estimated value and the wheel cylinder pressure estimated value. Therefore, a new master cylinder pressure estimated value Pme (n) is estimated by the following equation (5) using Cim as a predetermined coefficient.

Pme (n) = Pme (n-1) -Cim × (Pme (n-1) -Pwe (n-1)) ^1/2 (5)

In the next step 270, the master cylinder pressure estimated value Pme thus obtained is guarded as in step 160.

In the next step 280, a new wheel cylinder is calculated by the above-mentioned equation (2) using the previous wheel cylinder pressure estimated value Pwe (n-1) and the master cylinder pressure estimated value Pme (n-1). Estimate the pressure Pwe (n).

As described above, in the method for estimating the master cylinder pressure and the wheel cylinder pressure according to the present embodiment, the master cylinder pressure estimated value is made higher as the wheel cylinder pressure depressurization frequency (quantity) increases, and the pressure increase frequency (quantity) increases. It is intended to estimate the actual master cylinder pressure with high accuracy by lowering the master cylinder pressure estimated value as the number increases.

This is because the wheel cylinder pressure is frequently reduced.
It is considered that the master cylinder pressure occurring in the master cylinder 14 is high, and the fact that the wheel cylinder pressure is increased frequently means that the master cylinder pressure occurring in the master cylinder 14 at that time is low. Because.

FIG. 7 is a graph showing the manner of estimating the master cylinder pressure and the wheel cylinder pressure described above.

As indicated by A in the graph of FIG. 7, a predetermined time FBT (Fast Brake Tim) has elapsed after the start of the brake operation.
Up to e), the master cylinder pressure increases linearly. In this part, it is estimated by an increasing function having a predetermined slope Pgrad (initial setting). Here, Pconst is the brake pedal 10 and the master cylinder 1
4 corresponds to the jumping characteristic value of the booster 12 interposed between the four. In addition, after a predetermined time FBT has elapsed after the start of the brake operation, that is, the braking pressure (brake pedal force)
Is presumed to be substantially constant, and before the wheels are locked, the portion indicated by B in the graph before the ABS control is started is in the weak braking state (before the wheels are locked).
It is. Here, it is considered that the master cylinder pressure estimated value and the wheel cylinder pressure estimated value match, and is estimated from the vehicle deceleration. When the ABS control is started, the wheel cylinder pressure is first reduced. The portion indicated by w1 in the graph is the (predicted) depressurization amount Cdw of the estimated wheel cylinder pressure value.
(Pwe) ^1/2 , whereas the portion indicated by m1 in the graph is the increase correction amount Cdm × (Pw of the master cinder pressure estimated value.
e) ^1/2 . Also, the portion indicated by w2 in the graph is the (expected) pressure increase amount Ciw × (Pme−P) of the estimated wheel cylinder pressure value.
We) ^1/2 , whereas the part indicated by m2 in the graph is the reduction correction amount Cim × (Pme−
Pwe) ^1/2 .

Next, a second embodiment of the present invention will be described.

In the second embodiment, a master cylinder pressure sensor is further provided in addition to the first embodiment. Normally, the master cylinder pressure is detected by the output of this sensor, and the master cylinder pressure sensor has a defect. In this case, according to the present invention, the master cylinder pressure is properly estimated to back up. As a result, the wheel cylinder pressure is accurately estimated and braking control is properly performed.

FIG. 8 is a flow chart showing the master cylinder pressure monitoring process according to the second embodiment.

In step 300 of FIG. 8, the master cylinder pressure detection value Pms detected by the sensor is smaller than the master cylinder pressure estimation value Pme obtained according to the present invention multiplied by a predetermined coefficient (here, 1.5). It is determined whether or not. As a result, when the master cylinder pressure detection value Pms is smaller, the process proceeds to the next step 310. In step 310, the master cylinder pressure detection value Pms is added to the master cylinder pressure estimated value Pme by a predetermined coefficient (here, 0.
It is determined whether it is larger than the value obtained by multiplying 6). as a result,
If the master cylinder pressure detection value Pms is larger, this process ends. If either of the above two conditions is not satisfied, it is determined that the master cylinder pressure sensor is abnormal (the detected value Pms is different from the actual master cylinder pressure Pm), and the master is judged at step 320. The cylinder pressure estimated value Pme is set as the master cylinder pressure Pm actually used for control.

Further, a process as shown in FIG. 9 in which the predetermined coefficient (dead band coefficient, here, 1.5 and 0.6) used above is further reduced to improve the accuracy can be considered.

In step 400 of FIG. 9, a value Tmp for comparison with the master cylinder pressure detection value Pms is calculated by the following equation (6).

Tmp = Pme × Pmr + ΔPms (6) Here, Pmr is a proportional coefficient Pme / Pms, and ΔPms is an offset amount Pme−Pms.

In the next step 410, it is determined whether the master cylinder pressure detection value Pms is smaller than Tmp + 0.2. As a result of the determination, when the master cylinder pressure detection value Pms is smaller, the process proceeds to the next step 420. In step 420, the master cylinder pressure Pms is Tmp-0.
It is determined whether it is greater than 1. If the result of determination is that the master cylinder pressure detection value Pms is greater, then the next step 4
Proceed to step 30 and update Pmr and ΔPms with new values.

If either of the above two conditions is not satisfied, it is determined that the master cylinder pressure sensor is abnormal, and in step 440, the master cylinder pressure Pm actually used for control is calculated by the following equation (7). calculate.

Pm = Pme × Pmr + ΔPms (7)

As described above, by using the actual master cylinder pressure measurement and the master cylinder pressure estimation together, the duplication check is performed, and as a result, the wheel cylinder pressure is properly estimated to prevent the ABS control from being defective. .

The use of the wheel cylinder pressure properly estimated by the present invention will be described below.

The first is the use for determining an impossible estimated vehicle deceleration.

FIG. 10 shows the estimated vehicle deceleration (acceleration) Dvv.
6 is a graph showing a relationship between e (corresponding to a road surface friction coefficient μ) and an estimated wheel cylinder pressure value Pwe. As shown in the graph of FIG. 10, an approximately proportional relationship is established between the estimated vehicle deceleration (acceleration) Dvve (= smooth Vve−Vveold) determined by the road surface friction coefficient μ and the wheel cylinder pressure PweF of the front wheels. .

Utilizing this property, the vehicle deceleration (acceleration) desired by the estimated wheel cylinder pressure PweF of the front wheels is obtained.
Dvv is obtained, and a state in which the estimated vehicle deceleration (acceleration) Dvve is lower than the desired vehicle deceleration (acceleration) Dvv is detected. If the estimated vehicle deceleration Dvve is small, it is considered that the wheel slip is estimated to occur more than it actually is. Therefore, in this case, the reference slip amount ΔVR that is the control target of the rear wheels is made small (for example, 1/2) so that the pressure reduction in the ABS control can be executed with a smaller slip amount, and the wheel speed of the rear wheels is reduced. Try to create a reliable maximum wheel speed from. As a result, it is possible to prevent the estimated vehicle speed from deviating to the lower speed side than the actual vehicle speed.

That is, it is known that even if the ABS control is performed, all four wheels easily go to the lock during the slow braking on the low μ road. As shown in FIG. 10, the road surface friction coefficient μ is estimated from the wheel cylinder pressure, and when the desired vehicle deceleration (acceleration) Dvv shows a high μ with respect to the value of μ, the reference slip that is the control target of the rear wheels. By reducing the amount ΔVR, the rear wheels can easily enter the ABS control. This allows
By ensuring that the highest wheel speed is obtained, and thus creating an accurate estimated vehicle speed, it is possible to prevent four wheels from reaching lock at the same time.

The second is the use for correlating the front and rear wheel cylinder pressures.

Between the wheel cylinder pressures of the four wheels,
The maximum allowable wheel cylinder pressure on the wheel side is determined by the load distribution at each wheel position and the corresponding road surface friction coefficient. By providing means for controlling the wheel cylinder pressure of the front wheels to be high and the wheel cylinder pressure of the rear wheels to be low according to the load distribution and the maximum allowable pressure, the rear wheels can be used as vehicle speed monitoring wheels to achieve a stable maximum. Wheel speed and estimated vehicle speed can be obtained.

It is preferable that the means compares the front and rear wheel cylinder pressure estimated values on the same side of the left and right wheels in consideration of split road surfaces having different road surface friction coefficients for the left and right wheels. When the pressure is higher in the rear wheels than in the front wheels, the reference slip amount ΔVR of the rear wheels is reduced (for example, to 1/2). This allows the rear wheels to be low-slip, ie unlocked, and the maximum wheel speed can be reliably achieved, resulting in an accurate estimated vehicle speed. On the other hand, it is possible to control the wheel cylinder pressure of the front wheels to be high, and to bring out a high braking ability.

The third is utilization for rapid return to the top pressure immediately before depressurization.

The estimated value of the wheel cylinder pressure immediately before the pressure reduction is stored as the top pressure, and when the pressure increase is restarted, the estimated top pressure immediately before the pressure reduction is compared with the current estimated value of the wheel cylinder pressure. As a result, when the current estimated wheel cylinder pressure value is lower than the top pressure, the pressure increase amount is increased so as to return to the top pressure early, and when the pressure is higher than the top pressure, the pressure increase amount is reduced. By doing so, a higher braking force can be secured.

That is, in the past, since the signal time of the solenoid valve was directly determined, the pressure increase amount immediately after depressurization often becomes too large, and there is a problem that re-pressurization due to overbraking is likely to occur. Therefore, the amount of pressure increase immediately after depressurization could not be increased to the limit. However, by using the estimated wheel cylinder pressure value immediately before depressurization this time, it is possible to increase the amount of pressure increase immediately after depressurization to the limit without inducing overbraking, and it is possible to bring out a higher braking ability.

Fourthly, the low μ transition information of the front wheels is used for transmission to the rear wheels.

The estimated value of the wheel cylinder pressure immediately before the pressure reduction is stored as the top pressure, and the top pressure immediately before the pressure reduction is compared with the current estimated value of the wheel cylinder pressure to judge that the state is in the low μ state. This also reduces the front wheel μ
Transition information is created, and by using this low μ transition information, a means for prohibiting an increase in the wheel cylinder pressure of the rear wheel or for reducing the pressure in advance is used. The slip state can be avoided.

For example, when the estimated wheel cylinder pressure value of the front wheels is smaller than the top pressure, the reference slip amount ΔVR of the rear wheels is made small (for example, 1/2). When the front wheels approach a low μ road surface, slippage of the front wheels causes
The vehicle deceleration decreases. Further, the ground load with the road surface of the rear wheel increases due to the slip of the front wheel, the rear wheel enters a low slip state, and the operation of increasing the wheel cylinder pressure on the rear wheel side is started. This pressure increasing operation is an inconvenient pressure increasing operation that requires a larger amount of pressure reducing operation when the rear wheels soon approach a low μ road surface. In this case, the information of low μ shift is transmitted to the rear wheel side, and for example, the reference slip amount Δ of the rear wheel is
If VR is reduced to cope with the problem, it is possible to prevent the inconvenient increase of the wheel cylinder pressure of the rear wheels, and improve the stability of the vehicle (both the braking force and the steerability are compatible).

As described above, according to this embodiment, it is possible to accurately estimate the master cylinder pressure without using the master cylinder pressure sensor. Moreover, since the initial setting of the master cylinder pressure estimated value is performed using a function that increases with time, the master cylinder pressure estimated value converges quickly and the estimation accuracy is improved. Further, the reliability of control using the master cylinder pressure estimated value and the wheel cylinder pressure estimated value estimated using the master cylinder pressure estimated value is improved.

Further, when the actual master cylinder pressure measuring means is provided, even if the master cylinder pressure estimated value is in the coarse accuracy range of -30% to + 50% of the master cylinder pressure detected value, the wheel cylinder pressure estimated value is 4%. Since the magnitude relationship between the wheels is required with high accuracy, the wheel cylinder pressure estimation value exerts a sufficient effect for the usage 1 to 4.

[0086]

As described above, according to the present invention,
The master cylinder pressure can be accurately estimated without using an actual master cylinder pressure measuring means, and as a result, the wheel cylinder pressure can be accurately estimated and appropriate braking control can be performed.

[Brief description of drawings]

FIG. 1 is a block diagram showing the gist of the present invention.

FIG. 2 is a configuration diagram schematically showing a braking force control device according to the present invention.

FIG. 3 is a flowchart showing the operation of the first embodiment of the present invention.

FIG. 4 is a flowchart showing the operation of the first embodiment of the present invention.

FIG. 5 is a diagram showing a relationship between time immediately after brake operation and master cylinder pressure.

FIG. 6 is a diagram showing the relationship between vehicle deceleration and master cylinder pressure.

FIG. 7 is a diagram showing how master cylinder pressure and wheel cylinder pressure are estimated in the first embodiment.

FIG. 8 is a flowchart showing the operation of the second embodiment of the present invention.

FIG. 9 is a flowchart showing a modification of the second embodiment of the present invention.

FIG. 10 is a diagram showing a relationship between vehicle deceleration and wheel cylinder pressure.

[Explanation of symbols]

 10 ... Brake pedal 12 ... Booster 14 ... Master cylinder 20, 24, 34, 40, 44, 52 ... Brake fluid passage 22, 32, 42, 50 ... Switching valve 26, 36, 46, 54 ... Wheel cylinder 60, 62, 68, 70 ... Control valve 64, 72 ... Reservoir 76 ... Motor 78 ... Hydraulic pressure control device 80 ... Electronic control device 100, 102, 104, 106 ... Wheel speed sensor 110 ... Brake switch

Claims (7)

[Claims] 1. A master cylinder pressure estimating device having a hydraulic pressure control device for increasing / decreasing a hydraulic pressure generated by a master cylinder of a braking device and supplied to a wheel cylinder according to a running state of a vehicle. Initial setting means for uniformly setting the master cylinder pressure estimated value according to a predetermined arithmetic expression for a predetermined period, and after the lapse of the predetermined period and after the start of the increase / decrease control, the hydraulic pressure control device controls the wheel cylinders. When the hydraulic pressure supplied to the wheel cylinder is about to be increased, the estimated master cylinder pressure value is corrected according to the expected increase amount, and the hydraulic pressure supplied to the wheel cylinder is reduced. And a master cylinder pressure correction / estimation means for increasing and correcting the master cylinder pressure estimated value according to the expected pressure reduction amount. Star cylinder pressure estimation apparatus. 2. The method according to claim 1, wherein the expected amount of pressure reduction when the hydraulic pressure supplied to the wheel cylinder is about to be reduced is approximated depending only on the wheel cylinder pressure at that time. A master cylinder pressure estimating device characterized by. 3. The master cylinder pressure estimating device according to claim 1, wherein the master cylinder pressure is corrected / estimated using the deceleration of the vehicle after the predetermined period has elapsed and before the increase / decrease control is started. . 4. The wheel cylinder pressure is estimated to be equal to the master cylinder pressure currently estimated at that time after the predetermined period has elapsed and before the increase / decrease control is started. Master cylinder pressure estimation device. 5. The initial setting means according to claim 1,
A master cylinder pressure estimating device, wherein a function that increases with respect to a braking operation time is used as the predetermined arithmetic expression. 6. A master cylinder according to claim 1, further comprising a master cylinder pressure sensor for detecting an actual master cylinder pressure, and determining an abnormality of the master cylinder pressure sensor based on the estimated master cylinder pressure value. Pressure estimation device. 7. A wheel cylinder pressure estimating device comprising a hydraulic pressure control device for increasing / decreasing a hydraulic pressure generated by a master cylinder of a braking device and supplied to a wheel cylinder according to a running state of a vehicle. After the start, means for estimating the next wheel cylinder pressure based on the master cylinder pressure estimated value estimated in claim 1 and the increase / decrease amount of hydraulic pressure supplied to the wheel cylinder estimated in claim 1 A wheel cylinder pressure estimation device comprising: