JP4396475B2 - Vehicle braking force control device - Google Patents

Description

  The present invention relates to braking force control when the driver performs a braking operation by depressing the brake pedal during automatic braking for inter-vehicle distance control, vehicle speed control, etc., and in particular, the driver depresses the brake pedal after such braking operation. The present invention relates to a braking force control device for a vehicle that suitably controls the braking force when the vehicle is returned.

As a braking force control device for a vehicle, for example, a driver reference target deceleration is obtained from a braking operation state by a brake pedal, and a braking operation response formula for controlling the braking force of the vehicle so that the actual deceleration matches the driver reference target deceleration. The device is known.
On the other hand, as the braking force control device for a vehicle, the braking operation response type braking device and the braking system are shared, but the wheel is automatically braked for the vehicle distance control and the vehicle speed control, separated from the braking operation by the driver. However, there is an automatic brake device that realizes a target deceleration for automatic braking.

By the way, when the driver depresses the brake pedal during the automatic braking, it is necessary to switch from the braking force control for realizing the automatic braking target deceleration to the braking force control for realizing the driver reference target deceleration.
At this time, once the target deceleration is reset, the vehicle deceleration cannot be increased immediately after the switching, and there is a sense of incongruity due to the discontinuity of the deceleration.

  Therefore, conventionally, as described in Patent Document 1, for example, when the driver performs a braking operation during braking by the automatic brake, the target braking speed immediately before the braking operation is set to the target according to the increase in the braking operation amount. The final target deceleration obtained by adding the deceleration correction amount is obtained, the wheel is braked to achieve this, and if the braking operation amount subsequently decreases, the final target deceleration is set to the driver reference target deceleration. There has been proposed a braking force control device for a vehicle that brakes a wheel so that the final target deceleration is realized while being reduced.

According to such braking force control, when determining the final target deceleration at the time of switching from the automatic brake to the braking operation response brake, the target deceleration corresponding to the increase in the braking operation amount is added to the automatic braking target deceleration immediately before the braking operation. Since the speed correction amount is added and calculated, the vehicle deceleration can be increased immediately after the above switching, which can avoid the discomfort that is discontinuous, and the driver's braking operation is immediately reflected in the vehicle deceleration. Can improve the braking performance.
JP 2004-161173 A

  However, in the conventional braking force control, when the final target deceleration is lowered toward the driver reference target deceleration by depressing the brake pedal and reducing the braking operation amount after the braking operation, the final target deceleration is reduced. Since the deceleration is lowered to the driver reference target deceleration with a constant time change gradient regardless of the braking operation, the following problem occurs.

  FIG. 9 shows the case where the braking operation amount (master cylinder hydraulic pressure Pmc) by the driver increases in the case where the automatic braking target deceleration just before the braking operation by the driver is at point A. When the final target deceleration rate αdem increases as shown by a and reaches the value corresponding to point B, the driver releases the brake pedal so that the driver reference target deceleration rate αbase becomes something like b. The change state of the final target deceleration rate αdem when the master cylinder hydraulic pressure Pmc) is decreased to 0 at the C point is shown.

  When the driver reduces the braking operation amount (master cylinder hydraulic pressure Pmc) by releasing the brake pedal, the final target deceleration rate αdem is decreased from the value equivalent to point B to the driver reference target deceleration rate αbase. As described above, since the final target deceleration rate αdem is decreased at a constant time change gradient, the final target deceleration rate αdem has no correlation with the braking operation amount (master cylinder hydraulic pressure Pmc), and the release of the brake pedal is not performed. Depending on the way, the braking operation amount (master cylinder hydraulic pressure Pmc) decreases with the relationship indicated by d, decreases with the relationship indicated by e, and the vehicle deceleration has a different sense of discomfort than the driver expected. There is a concern to become.

For example, when the driver depresses the brake pedal slightly (slowly) under the same conditions as in FIG. 9, the brake operation amount (master cylinder hydraulic pressure Pmc) decreases slightly (slowly) despite this. The vehicle deceleration is greatly (rapidly) lowered and a change in deceleration different from the driver's expectation occurs, which may cause the driver to feel uncomfortable.
On the other hand, if the driver depresses the brake pedal greatly (rapidly), the vehicle deceleration slightly decreases despite the rapid decrease in the braking operation amount (master cylinder hydraulic pressure Pmc). Even in this case, a deceleration change different from that expected by the driver may occur, which may cause the driver to feel uncomfortable.

According to the present invention, the above-described problem is caused by lowering the final target deceleration after the start of stepping back of the brake pedal with a constant time-varying gradient until it matches the driver reference target deceleration without relating to the braking operation. Based on the factual recognition that
By causing the final target deceleration to be reduced to the driver reference target deceleration in the context of the braking operation, the vehicle deceleration with an uncomfortable feeling different from the driver's expectation in the braking operation at the time of stepping back can be obtained. An object of the present invention is to propose a braking force control device for a vehicle that can solve the problem of occurrence.

For this purpose, the braking force control device for a vehicle according to the present invention is configured as described below.
First of all, to explain the prerequisite braking force control device,
Automatic braking means that automatically brakes the wheel separately from the driver's braking operation and achieves the target deceleration for automatic braking;
Basically, the wheels are braked so as to achieve the driver reference target deceleration according to the driver's braking operation. If the driver performs a braking operation during braking by the automatic brake means, The brakes were reduced by braking the wheels to achieve the final target deceleration obtained by adding the target deceleration correction amount corresponding to the increase in the braking operation amount to the target deceleration for automatic braking at Thereafter, the vehicle is provided with braking operation response brake means for braking the wheel so as to realize the final target deceleration while decreasing the final target deceleration toward the driver reference target deceleration.
The present invention provides a braking force control device for such a vehicle,
A decrease in the final target deceleration of the driver reference target deceleration after reduction of the amount of braking operation, such as low down in the final target deceleration for lowering the braking operation amount as the rate of decrease in the amount of braking operation is fast becomes large Having a configuration provided with a final target deceleration change rate correction means at the time of stepping back performed in a mode ,
The final target deceleration change rate correcting means at the time of stepping down reduces the automatic braking target deceleration immediately before the driver starts the braking operation and the amount of braking operation after the braking operation. In accordance with the deceleration ratio between the target deceleration correction amount immediately before the target, the region where the final target deceleration is decreased with respect to the decrease in the braking operation amount in the region where the deceleration ratio is small, and the deceleration ratio is large. This is characterized in that the reduction speed of the final target deceleration is increased with respect to the reduction of the braking operation amount at .

In the braking force control apparatus of the present invention, the final target deceleration that was increased in response to the driver's braking operation during braking by the automatic braking means has been reduced in the braking operation amount. When the target deceleration is reduced toward the driver reference target deceleration, the final target deceleration is reduced to the driver reference target deceleration. The faster the braking operation amount decreases, the lower the final target deceleration relative to the decrease in the braking operation amount. There is provided a final target deceleration change rate correction means at the time of stepping back that is performed in such a manner that the bottom increases , and this final target deceleration change rate correction means at the time of stepping back is set by the driver during braking by the automatic brake means. Deceleration is performed in accordance with the deceleration ratio between the target deceleration for automatic braking immediately before the operation is started and the target deceleration correction amount immediately before the braking operation amount is reduced after the braking operation. Since the ratio is slow reduction rate of the final target deceleration for decrease in amount of braking operation of a small area, increasing the reduction rate of the final target deceleration for decrease in amount of braking operation in the deceleration ratio is large area,
When the final target deceleration is decreased toward the driver reference target deceleration due to a decrease in the braking operation amount, the faster the braking operation amount decreases, the faster the final target deceleration decreases. As a result, the vehicle deceleration as expected can be generated when the braking operation amount decreases due to the above, and it is possible to eliminate or alleviate the uncomfortable feeling that a vehicle deceleration different from that expected.

Hereinafter, embodiments of the present invention will be described in detail based on examples shown in the drawings.
FIG. 1 shows a hydraulic brake device for a vehicle including a braking force control device according to an embodiment of the present invention.
This hydraulic brake device generates a braking force by supplying hydraulic pressure to a wheel cylinder 2 provided in association with a wheel 1 (only one is shown in the figure). It also serves as a means, and specifically has the following configuration.

3 is a brake pedal that the driver depresses according to the braking force of the vehicle desired by the driver. The pedal force of the brake pedal 3 is boosted by the hydraulic booster 4, and the unillustrated piston cup of the master cylinder 5 is boosted by the boosted force. Is pushed, the master cylinder 5 outputs the master cylinder hydraulic pressure Pmc corresponding to the depression force of the brake pedal 3 to the brake hydraulic pressure pipe 6.
In FIG. 1, the brake hydraulic pipe 6 is connected only to the wheel cylinder 2 provided on one wheel 1. However, the brake hydraulic pipe 6 can also be connected to the wheel cylinders related to other three wheels not shown. Needless to say.

The hydraulic booster 4 and the master cylinder 5 use brake fluid in a common reservoir 7 as a working medium.
The hydraulic booster 4 includes a pump 8. The pump 8 accumulates brake fluid sucked and discharged from the reservoir 7 in the accumulator 9, and the accumulator internal pressure is sequence-controlled by the pressure switch 10.
The hydraulic booster 4 boosts the depression force of the brake pedal 3 using the pressure in the accumulator 9 as a pressure source, and pushes the piston cup in the master cylinder 5 with the boosted depression force.
At this time, the master cylinder 5 contains the brake fluid from the reservoir 7 in the brake pipe 6 and generates a master cylinder hydraulic pressure Pmc corresponding to the brake pedal depression force. The wheel 1 can be hydraulically braked.

The wheel cylinder hydraulic pressure Pwc can be feedback controlled (electronically controlled) as will be described later using the accumulator internal pressure of the accumulator 9, and a brake-by-wire actuator 20 is provided for this purpose.
This actuator 20 is provided with an electromagnetic switching valve 21 inserted in the middle of the brake pipe 6, and connected to the brake pipe 6 on the wheel cylinder 2 side of the electromagnetic switching valve 21, and the pressure increasing valve 22 is inserted. A pressure-increasing circuit 23 and a pressure-reducing circuit 25 in which a pressure-reducing valve 24 is inserted.

The pressure increasing circuit 23 is extended between the brake pipe 6 and the suction circuit of the pump 8, and the pressure reducing circuit 25 is extended between the brake pipe 6 and the discharge circuit of the pump 18.
The electromagnetic switching valve 21 normally opens the brake pipe 6 as shown in the figure to direct the master cylinder hydraulic pressure Pmc to the wheel cylinder 2 and shuts off the brake pipe 6 when the solenoid 21a is turned on and the master cylinder 5 to the stroke simulator. According to the wheel cylinder 2, the same hydraulic load is applied to the brake pedal 3, so that the brake pedal 3 can be continuously given the same operation feeling as usual.

The pressure increasing valve 22 normally opens the pressure increasing circuit 23 as shown in the figure to increase the wheel cylinder hydraulic pressure Pwc by the internal pressure of the accumulator 9, but when the solenoid 22a is turned ON, the pressure increasing circuit 23 is proportional to the amount of current supplied. Decrease the opening and decrease the increase ratio of wheel cylinder hydraulic pressure Pwc,
The pressure reducing valve 24 normally shuts off the pressure reducing circuit 25 as shown in the figure, but when the solenoid 24a is turned ON, the pressure reducing circuit 25 increases the opening degree in proportion to the energization amount to reduce the reduction ratio of the wheel cylinder hydraulic pressure Pwc. It shall increase.

Here, the pressure increasing valve 22 and the pressure reducing valve 24 shut off the corresponding pressure increasing circuit 23 and the pressure reducing circuit 25 while the switching valve 21 opens the brake pipe 6, and thereby the wheel cylinder hydraulic pressure Pwc is mastered. As determined by the cylinder hydraulic pressure Pmc,
In order to function as an automatic brake means or a brake operation response brake means, the brake pipe 6 is shut off by turning on the switching valve 21 while the pressure increase valve 22 or the pressure reducing valve 24 is used to increase or decrease the wheel cylinder hydraulic pressure Pwc. Thus, the wheel cylinder hydraulic pressure Pwc can be increased or decreased without being affected by the master cylinder hydraulic pressure Pmc.

The control of the switching valve 21, the pressure increasing valve 22 and the pressure reducing valve 24 is performed by a hydraulic brake controller 27.
A signal from the pressure sensor 28 for detecting the master cylinder hydraulic pressure Pmc representing the braking force of the vehicle requested by the driver;
A signal from the pressure sensor 29 for detecting the wheel cylinder hydraulic pressure Pwc representing the actual value of the hydraulic braking torque, and
A signal from a wheel speed sensor 30 that detects a wheel speed Vw that is a peripheral speed of the wheel 2, and
A signal from the acceleration sensor 31 that detects the acceleration / deceleration G acting on the vehicle is input.
Based on the input information, the hydraulic brake controller 27 controls the switching valve 21, the pressure increasing valve 22, and the pressure reducing valve 24 so that a hydraulic braking force command value described later is achieved.

2 and 3 are control programs executed by the hydraulic brake controller 27 for controlling the braking force targeted by the present invention.
FIG. 2 shows a main routine repeatedly executed by a scheduled interrupt every 10 msec, and FIG. 3 shows a subroutine related to the calculation processing of the final target deceleration rate αdem in this main routine.
In step S10 of FIG. 2, the master cylinder hydraulic pressure Pmc and the wheel cylinder hydraulic pressure Pwc of the wheel 1 are calculated.

In the next step S20, the wheel speed Vw of the wheel 1 is calculated, and this wheel speed Vw is passed through a bandpass filter indicated by the following transfer function Fbpf (s) to obtain the wheel deceleration αv.
Fbpf (s) = s / {(1 / ω ² ) s ² + (2ζ / ω) s + 1} (1)
s: Laplace operator However, actually, it is calculated using a recurrence formula obtained by discretization by Tustin approximation or the like.

In step S30, an automatic brake target deceleration rate αauto is read from a high-speed communication reception buffer with an unillustrated automatic brake controller.
The target deceleration αauto for automatic braking is a deceleration obtained by the controller for automatic braking to control the inter-vehicle distance, control the vehicle speed, etc., and increases as the inter-vehicle distance becomes shorter than the set value. It increases as the set vehicle speed is greatly exceeded.

In step S40, from the master cylinder hydraulic pressure Pmc, the constant K1 corresponding to the vehicle specifications stored in the ROM in advance, and the automatic brake target deceleration rate αauto, the vehicle will be described in detail later with reference to FIG. The final target deceleration rate αdem is calculated.
Hereinafter, the deceleration is treated as a negative value, and the braking torque is treated as a negative value.
Needless to say, the braking physical quantity (vehicle driving state) commanded by the driver may be detected not only by the master cylinder hydraulic pressure Pmc but also by the master cylinder stroke or the brake pedal depression force.

In step S50 of FIG. 3, a braking torque command value Tdff (brake torque feedforward compensation amount) necessary to realize the target deceleration rate αdem is calculated using the feedforward compensator 51 of FIG.
That is, first, the target deceleration rate αdem is converted into the braking torque using the constant K2 determined by the vehicle specifications, and then the response characteristic Pm (s) of the control target vehicle 54 is converted into the characteristic Fref (s) of the reference model 52 in FIG. ) For the target deceleration αdem through the braking torque corresponding to the target deceleration (αdem) to the characteristic C _FF (s) expressed by the following equation of the feedforward compensator (phase compensator) 51 for matching Determine command value Tdff (feedforward compensation amount).

Actually, the braking torque command value Tdff (feed forward compensation amount) for the target deceleration rate αdem is also discretized and calculated as described above.
C _FF (s) ＝ Fref (s) / Pm (s)
= (Tp · s + 1) / (Tr · s + 1) (2)
Tp: Time constant
Tr: Time constant
Pm: Vehicle model characteristics of the controlled vehicle
(Vehicle deceleration characteristics with respect to braking torque command value)

  Next, in step S60, it is determined whether or not the brake pedal has been depressed depending on whether or not the master cylinder hydraulic pressure Pmc is a minute set value or more. When this brake pedal is operated, in step S70, A braking torque command value Tdfb (feedback compensation amount) for the target deceleration rate αdem is obtained, and a total braking torque command value Tdcom necessary for realizing the target deceleration rate αdem is obtained.

In this embodiment, the deceleration controller is configured by a “two-degree-of-freedom control system” as shown in FIG. 4 and includes a feedback compensator 53 in addition to the feedforward compensator 51 and the reference model 52 described above. Shall.
Closed-loop performance such as control stability and disturbance resistance is realized by the feedback compensator 53, and response to the target deceleration αdem is basically realized by the feedforward compensator 51 (when there is no modeling error). The
The first final target deceleration αdem is in calculating the feedback compensation amount Tdfb, through reference model 52 having a characteristic Fref (s) represented by the following equation obtains the reference model response deceleration alpha _ref.
Fref (s) = 1 / (Tr · s + 1) (3)

Further, as shown in FIG. 4, a deceleration feedback deviation Δα between the reference model response deceleration α _ref and the actual deceleration αv of the control target vehicle 54 (see step S20) is obtained.
△ α = α _ref −αv ···(Four)
Then, the deceleration feedback deviation Δα is passed through a feedback compensator 53 having a characteristic C _FB (s) expressed by the following equation to obtain a braking torque feedback compensation amount Tdfb.
C _FB (s) = (Kp · s + Ki) / s (5)
However, in this embodiment, this characteristic is realized by a basic PI controller, and the control constants Kp and Ki are determined in consideration of gain margin and phase margin.
Equations (3) and (5) are calculated in the same manner as described above.

  Next, as shown in FIG. 4, the braking torque command value Tdff (feedforward compensation amount) for the final target deceleration αdem described above and the braking torque feedback compensation amount Tdfb are added together to obtain the total braking torque command value (target Determine braking torque (Tdcom).

  While it is determined in step S60 that the brake pedal is not operated, in step S80, the braking torque feedback compensation amount Tdfb and the internal variable of the digital filter expressed by the equation (5) used when obtaining this are initialized to PI. The integral term of the controller is initialized, and the total braking torque command value (target braking torque) Tdcom is set to 0 in response to no brake pedal operation.

In the next step S90 in FIG. 2, the target braking torque Tdcom obtained as described above is distributed back and forth based on the front and rear wheel braking torque ideal distribution characteristics illustrated in FIG. Tdcomf and rear wheel braking torque command value Tdcomr are obtained.
The front / rear braking torque ideal distribution characteristics illustrated in FIG. 5 are determined by taking into consideration the prevention of rear wheel tip lock accompanying the front / rear wheel load movement during braking, stability of vehicle behavior, shortening of the braking distance, etc. This is the front / rear braking force distribution that simultaneously locks the brakes.

In the next step S100 in FIG. 2, constants based on vehicle specifications previously stored in the ROM based on the hydraulic braking torque command values Tbcomf and Tbcomr for the front and rear wheels determined in step S90 as described above. Using K3 and K4, the front and rear wheel cylinder hydraulic pressure command values Pbcomf and Pbcomr are calculated by the following equations.
Pbcomf ＝ Tbcomf × K3
Pbcomr = Tbcomr × K4

In the next step S110, the front and rear wheel wheel hydraulic pressure command values Pbcomf and Pbcomr obtained in step S100 are transmitted to the hydraulic brake controller 27 in FIG.
The hydraulic brake controller 27 controls the hydraulic pressure applied to the wheel cylinder 2 to the corresponding wheel cylinder hydraulic pressure command value through the control of the solenoid valves 21, 22, 24, and the wheel cylinder hydraulic pressure of the other three wheels. Similarly, control is performed so that the corresponding wheel cylinder hydraulic pressure command value is obtained.

The process for obtaining the final target deceleration rate αdem in step S40 of FIG. 2 will be described in detail with reference to FIG.
In the following, it is assumed that [i] attached to each symbol means the current value, and [i-1] means the previous value.

First, in step S401, it is determined whether braking is performed when the brake pedal is depressed or non-braking is performed when the brake pedal is released depending on whether or not the current master cylinder hydraulic pressure Pmc [i] is equal to or higher than a minute set value.
If the brake pedal is released and the vehicle is not being braked, the driver reference target deceleration rate αauto [i] is set to the final target deceleration rate αdem [i] in step S402 to perform braking by automatic braking.
The driver reference target deceleration rate αauto [i] includes, of course, αauto [i] = 0 when automatic braking is not required.

When it is determined in step S401 that the brake pedal is being depressed, it is determined in step S403 whether the current master cylinder hydraulic pressure Pmc [i] is equal to or higher than the previous master cylinder hydraulic pressure Pmc [i-1]. It is determined whether the brake pedal is being depressed (including when the brake pedal is released), the pedal position is maintained, or the brake pedal is being depressed.
When it is determined in step S403 that the brake pedal is being increased or the pedal position is maintained, in step S404, the target deceleration that represents the change rate of the final target deceleration with respect to the change in the master cylinder hydraulic pressure Pmc (braking operation amount). the rate of change K _alpha, substitutes the constant K1 for each vehicle specification that has been stored in the ROM as a target deceleration rate of change for widening stepping.

On the other hand, when it is determined in step S403 that the brake pedal is being returned, in step S406, the target deceleration for stepping back representing the change rate of the final target deceleration with respect to the change in the master cylinder hydraulic pressure Pmc (braking operation amount). Substitute the ratio between the previous final target deceleration rate αdem [i-1] and the previous master cylinder hydraulic pressure Pmc [i-1] for the rate of change Kg.
Kg = αdem [i-1] / Pmc [i-1] (6)
And decide.
In the next step S407, it sets the target deceleration change rate Kg for the stepping back to the target deceleration rate of change K _alpha.
In the next step S408, corrected by the above as-determined target deceleration rate of change K _alpha for depression return in step S407 as follows.

That is, the brake pedal depression returning velocity Vdown calculated from the time rate of change of the master cylinder pressure Pmc, searches the correction coefficient H1 is based on a correction coefficient map for the target deceleration rate of change K _alpha previously defined as illustrated in FIG. 6 To do.
Here, as apparent from FIG. 8, the minimum value of the correction coefficient H1 is 1, and the correction coefficient H1 is set to a value larger than 1 as the brake pedal depressing speed Vdown increases.
Then, the target deceleration change rate _Kα is corrected by the following equation.
K _α = K _α × H1 (7)

Furthermore, based on the correction coefficient map for the target deceleration rate of change K _alpha previously defined as illustrated in Figure 7, to find the correction coefficient H2 from the deceleration ratio Arufarto.
Note that the deceleration ratio αrto is the automatic braking target deceleration rate αauto [value immediately before starting the braking operation] (see FIGS. 10 and 11) immediately before the braking operation is performed during automatic braking, and the subsequent stepping back. A ratio Δα [a value just before the start of stepping back] / αauto [a value immediately before the start of the stepping back] relative to the target deceleration correction amount Δα [a value immediately before the start of stepping back] (see FIG. 10 and FIG. 11; The value immediately before the start of operation].
As is apparent from FIG. 7, the correction coefficient H2 is smaller in the region where the deceleration rate αrto is smaller than the set value αrto1, that is, according to the braking operation of the driver with respect to the actually generated deceleration. In a region where the ratio is small, the smaller the ratio, the smaller the positive value, and in a large region where the deceleration ratio αrto is greater than or equal to the set value αrto1, the greater the deceleration ratio αrto, that is, the actual deceleration that occurs. On the other hand, in a region where the ratio of the driver's braking operation is large, the larger the ratio, the larger the value.
Then, further corrected by the following equation the target deceleration rate of change K _alpha corrected by equation (7).
K _α = (K _α × H1) × H2 (8)

Furthermore, based on the correction coefficient map for the target deceleration rate of change K _alpha previously defined as illustrated in FIG. 8, it retrieves a correction coefficient H3 from the turning radius of the vehicle.
Here, as apparent from FIG. 8, the maximum value of the correction coefficient H3 is 1, and the positive value is smaller than 1 as the turning radius is smaller.
Then, the target deceleration change rate K _α corrected by the equation (7) is further corrected by the following equation,
K _α = (K _α × H1) × H3 (9)
If desired, further corrected by the following equation the target deceleration rate of change K _alpha corrected by equation (10).
K _α = (K _α × H2 × H4) × H5 (10)

Step S408, since it corrects the target deceleration rate of change K _alpha for depression return as described above, corresponds to the final target deceleration change rate correcting means during depression return in the present invention.

In the next step S409, the target deceleration rate of change K _alpha corrected as described above in step S408 may determine whether the target deceleration rate of change less than Kg for depression return obtained in step S406, If it is less than the target deceleration change rate K _α = Kg, the target deceleration change rate K _α is prevented from becoming smaller than the target deceleration change rate Kg for stepping back in step S410.
When K _alpha <Kg is not satisfied in step S409, by skipping step S410, the target deceleration rate of change K _alpha corrected in step S408 is used as it is.

As described above, after the target deceleration change rate K _α is obtained in step S404, step S408, or step S410, in step S411, the current master cylinder hydraulic pressure Pmc [i] and the previous master cylinder are determined. calculating a hydraulic pressure Pmc [i-1] target deceleration change amount by multiplying the target deceleration rate of change K _alpha in the change amount (change amount of the brake operation) between the [Delta] [alpha].
Next, in step S412, the above-described target deceleration change amount Δα is added to the previous final target deceleration rate αdem [i-1] to calculate the current final target deceleration rate αdem [i].
In step S413, the driver reference target deceleration rate αbase [i] is calculated by multiplying the master cylinder hydraulic pressure Pmc [i] by a constant K0 corresponding to the vehicle specifications stored in advance in the ROM.
αbase [i] ＝ Pmc [i] × K0 (11)

In the next step S414, it is checked whether or not the final target deceleration rate αdem [i] obtained in step S412 is less than the driver reference target deceleration rate αbase [i] calculated in step S413. By setting [i] = αbase [i], the final target deceleration rate αdem [i] is prevented from falling below the driver reference target deceleration rate αbase [i].
However, when it is determined in step S414 that αdem [i] <αbase [i] is not satisfied, the final target deceleration rate αdem [i] obtained in step S412 is used as it is.

In step S40 of FIG. 2, the final target deceleration rate αdem [i] is obtained as described above in step S402, step S412, or step S415 of FIG. 3, and this is used for the calculation after step S50.
After obtaining the current final target deceleration rate αdem [i] as described above in step S402, step S412, or step S415 in FIG. 3, the current final target deceleration rate αdem [i] is determined in step S416. In addition to memorizing αdem [i-1], this master cylinder hydraulic pressure Pmc [i] is memorized in Pmc [i-1], and these αdem [i-1] and Pmc [i-1] Used in calculations.

The effects of the above-described embodiment will be described below with reference to FIGS. 10 to 12 when the driver performs a braking operation as shown in FIG.
In FIG. 13, automatic braking for inter-vehicle distance control and the like was performed until the instant t1, but after that, the driver performed a braking operation in which the master cylinder hydraulic pressure Pmc changed in time series as illustrated. At the moment, that is, instant t1 (corresponding to point A in FIG. 9), the brake pedal is depressed to start switching from automatic braking to braking operation response braking, and braking is performed between instant t2 and t3 (corresponding to point B in FIG. 9). 10 is an operation time chart when the pedal depression position is kept the same, the brake pedal is stepped back between instants t3 and t4, and the brake pedal is released at instant t4 (corresponding to point C in FIG. 9).

  During automatic braking up to instant t1, the final target deceleration rate αdem is set to the target deceleration rate αauto for automatic braking (step S402). After t1 when the brake pedal starts to be depressed, Since the target deceleration correction amount Δα corresponding to the increase in the braking operation amount (master cylinder hydraulic pressure Pmc) is added to obtain the final target deceleration rate αdem (steps S411 and S412), the automatic brake changes to the braking operation response brake. Immediately after the switching instant t1, the vehicle deceleration can be increased to avoid discontinuity, and the driver's braking operation can be immediately reflected in the vehicle deceleration, improving the braking performance. Can be realized.

  On the other hand, when the final target deceleration rate αdem is returned to the driver reference target deceleration rate αbase after the instant t3 when the brake pedal is returned, the conventional target deceleration rate αdem is conventionally set to the braking operation as described above with reference to d and e in FIG. Regardless of the above, since it was decreased at a constant time change gradient (speed) as shown by f in FIG. 13 and matched with the driver reference target deceleration rate αbase, a deceleration with a sense of incongruity different from the braking operation was generated as described above. However, according to the present embodiment, this problem can be alleviated or solved for the following reason.

In other words, the amount of braking operation, such as momentary t3~t4 decrease in the final target deceleration by setting and correction of the target deceleration rate of change K _alpha according to the braking operation by the step S406~ step S408 in (master cylinder pressure Pmc) As illustrated in g in FIG. 13 and as illustrated in j in FIG. 10, αdem has a corresponding correlation with the braking operation amount (master cylinder hydraulic pressure Pmc) and has a driver reference target deceleration rate αbase. It is possible to generate the vehicle deceleration as expected when the amount of braking operation (master cylinder hydraulic pressure Pmc) by the driver is reduced, and there is a sense of incongruity that a vehicle deceleration different from that expected is generated. It can be eliminated or alleviated.

Then, when the target deceleration change rate _Kα is corrected in step S408 in FIG. 3 when the braking operation amount (master cylinder hydraulic pressure Pmc) decreases (at the time of stepping back) as shown by the instant t3 to t4, the correction coefficient H1 As shown in Fig. 6, the change (decrease) in the brake operation amount (master cylinder hydraulic pressure Pmc) increases as the brake operation amount (master cylinder hydraulic pressure Pmc) decrease rate (brake pedal depressing speed) increases. Because we decided to increase the rate of change (decrease rate) of the final target deceleration αdem with respect to
The case where the brake pedal is released and the braking operation amount (master cylinder hydraulic pressure Pmc) is set to 0 at the same point B in FIG. 10 as in FIG. 9 will be explained. The final target deceleration rate αdem gradually changes (decreases) as shown by j in the figure with respect to the change (decrease) in the pressure Pmc). Will change (decrease) rapidly as shown,
In other words, as described in FIG. 13, the final target deceleration rate αdem after t3 at the start of stepping back, slowly decreases toward the driver reference target deceleration rate αbase as indicated by g at the slow stepping back speed, and the fast stepping back speed In this case, as shown by h, it quickly matches the driver reference target deceleration rate αbase, and the following effects can be obtained.

If fine adjustment of vehicle deceleration is not required, such as when the brake pedal is suddenly returned (rapid release), the vehicle deceleration is quickly reduced as indicated by k and h in Figs. 10 and 13. The speed can be returned to αbase.
On the other hand, if fine adjustment of the vehicle deceleration is required, such as when the brake pedal is slowly depressed (released), the vehicle deceleration should be adjusted gently as shown by j and g in Figs. By returning to the reference target deceleration rate αbase, it is possible to easily perform the fine adjustment when it is necessary to finely adjust the vehicle deceleration on the way.

Further, when the braking operation amount (master cylinder hydraulic pressure Pmc) decreases at the instant t3 to t4 in FIG. 13 (when the brake pedal is released), the target deceleration change rate _Kα is corrected in step S408 in FIG. 7, the correction coefficient H2 is determined as shown in FIG. 7, and the automatic braking target deceleration rate αauto [immediately before starting the braking operation] immediately before the driver starts the braking operation during the braking by the automatic braking means (the point A). Value] (see FIG. 11) and the deceleration between the target deceleration correction amount Δα [the value immediately before the start of stepping back] (see FIG. 11) immediately before the braking operation amount is decreased after the braking operation (point B). According to the ratio αrto (= Δα [value immediately before starting to return] / αauto [value immediately before starting braking operation]), the braking operation amount (master cylinder hydraulic pressure) in the region where this deceleration ratio αrto is small (αrto <αrto1 in FIG. 7). Decrease in final target deceleration rate αdem against decrease in Pmc) In the region where the rate is reduced and the deceleration ratio αrto is large (αrto ≧ αrto1 in Fig. 9), the reduction rate of the final target deceleration rate αdem with respect to the decrease in the braking operation amount (master cylinder hydraulic pressure Pmc) is increased. An effect is obtained.

In other words, in the region where the deceleration ratio αrto is small (αrto <αrto1), in other words, when the ratio of the deceleration requested by the driver to the actual vehicle deceleration is small, the braking operation amount (master By reducing the decrease rate of the final target deceleration rate αdem with respect to the decrease in the cylinder hydraulic pressure (Pmc) as shown by m in FIG. 11, fine adjustment of the deceleration rate can be facilitated and the sense of incongruity due to sudden changes in the deceleration rate can be alleviated. .
On the other hand, in the region where the deceleration ratio αrto is large (αrto ≧ αrto1), in other words, when the ratio of the deceleration requested by the driver by the braking operation to the actually generated vehicle deceleration is large, the braking operation amount ( By increasing the decrease rate of the final target deceleration rate αdem with respect to the decrease in the master cylinder hydraulic pressure Pmc) as indicated by n in FIG. 11, it is possible to quickly return to the driver reference target deceleration rate αbase. it can.

Further, when the braking operation amount (master cylinder hydraulic pressure Pmc) decreases at the instant t3 to t4 in FIG. 13 (when the brake pedal is released), the target deceleration change rate _Kα is corrected in step S408 in FIG. The correction factor H3 is determined as illustrated in FIG.
When the turning radius of the vehicle is large, the change rate (decrease rate) of the final target deceleration rate αdem with respect to the change (decrease) in the braking operation amount (master cylinder hydraulic pressure Pmc) is increased as indicated by q in FIG.
When the turning radius of the vehicle is small, the change rate (decrease rate) of the final target deceleration rate αdem with respect to the change (decrease) in the braking operation amount (master cylinder hydraulic pressure Pmc) is reduced as indicated by u in FIG. Since the,
A change in the yaw rate of the vehicle caused by a change in deceleration, which becomes a problem when the turning radius is small, can be suppressed to prevent a decrease in turning traveling stability.

In any case, when the braking operation amount (master cylinder hydraulic pressure Pmc) is reduced to 0 due to a decrease in the braking operation amount (master cylinder hydraulic pressure Pmc) as shown in the instants t3 to t4 in FIG. 13, as indicated by g in FIG. j, m in FIG. 11, and u in FIG. 12, so that the final target deceleration rate αdem returns to the driver reference target deceleration rate αbase before the braking operation amount (master cylinder hydraulic pressure Pmc) decreases to 0. to determine the degradation rate of the final target deceleration αdem for decrease in amount of braking operation (master cylinder pressure Pmc), setting step S406~ step S408 of FIG. 3 is a target deceleration rate of change K _alpha in accordance with the braking operation and It is better to make corrections.
In such a case, when the driver sets the braking operation amount (master cylinder hydraulic pressure Pmc) to 0, the final target deceleration rate αdem is also surely set to 0, and there is still a feeling of deceleration even though the brake pedal is released. A sense of incongruity can be avoided.

1 is a schematic system diagram showing a hydraulic brake device for a vehicle including a braking force control device according to an embodiment of the present invention, together with its control system. It is a flowchart which shows the main routine of the braking force control program which the hydraulic brake controller in the control system performs. It is a flowchart which shows the subroutine regarding the final target deceleration calculating process in the main routine. It is a block diagram which illustrates the deceleration controller of a vehicle. It is a characteristic view which illustrates the front-and-rear wheel braking torque ideal distribution characteristic of vehicles. It is a change characteristic figure of the target deceleration correction coefficient for stepping-back at the time of brake pedal stepping-back speed. It is a change characteristic figure of the target deceleration correction coefficient for stepping back with respect to a deceleration ratio. It is a change characteristic figure of the target deceleration correction coefficient for the step back at the time of vehicles turning radius. It is a characteristic view which shows the change tendency of the final target deceleration with respect to the amount of braking operations at the time of using the conventional braking force control apparatus. FIG. 4 is a characteristic diagram showing a change tendency of a final target deceleration with respect to a braking operation amount when the braking force control of FIGS. 2 and 3 is performed for each stepping-back speed. FIG. 4 is a characteristic diagram showing a change tendency of a final target deceleration with respect to a braking operation amount when the braking force control of FIGS. 2 and 3 is performed for each deceleration ratio. FIG. 4 is a characteristic diagram showing a change tendency of a final target deceleration with respect to a braking operation amount when the braking force control of FIGS. 2 and 3 is performed for each turning radius of the vehicle. FIG. 4 is an operation time chart when the braking force control of FIGS. 2 and 3 is performed. FIG.

Explanation of symbols

1 Wheel 2 Wheel Cylinder 3 Brake Pedal 4 Hydraulic Booster 5 Master Cylinder 6 Brake Piping 7 Reservoir 8 Pump 9 Accumulator
10 Pressure switch
20 Brake-by-wire actuator
21 Solenoid switching valve
22 Booster valve
23 Booster circuit
24 Pressure reducing valve
25 Pressure reducing circuit
26 Stroke simulator
27 Hydraulic brake controller
28,29 Pressure sensor
30 Wheel speed sensor
31 Acceleration / deceleration sensor
51 Feedforward compensator
52 Reference model
53 Feedback compensator
54 Vehicles to be controlled

Claims (3)

Automatic braking means that automatically brakes the wheel separately from the driver's braking operation and achieves the target deceleration for automatic braking;
Basically, the wheels are braked so as to achieve the driver reference target deceleration according to the driver's braking operation. If the driver performs a braking operation during braking by the automatic brake means, The brakes were reduced by braking the wheels to achieve the final target deceleration obtained by adding the target deceleration correction amount corresponding to the increase in the braking operation amount to the target deceleration for automatic braking at Thereafter, in a braking force control device for a vehicle comprising braking operation response brake means for braking the wheel so as to realize the final target deceleration while reducing the final target deceleration toward the driver reference target deceleration,
A decrease in the final target deceleration of the driver reference target deceleration after reduction of the amount of braking operation, such as low down in the final target deceleration for lowering the braking operation amount as the rate of decrease in the amount of braking operation is fast becomes large setting the final target deceleration change rate correcting means during depression return to perform in a manner,
The final target deceleration change rate correcting means at the time of stepping down reduces the automatic braking target deceleration immediately before the driver starts the braking operation and the amount of braking operation after the braking operation. In accordance with the deceleration ratio between the target deceleration correction amount immediately before the target, the region where the final target deceleration is decreased with respect to the decrease in the braking operation amount in the region where the deceleration ratio is small, and the deceleration ratio is large. A braking force control apparatus for a vehicle, characterized by increasing a decrease speed of a final target deceleration with respect to a decrease in a braking operation amount in the vehicle. The braking force control apparatus for a vehicle according to claim 1 ,
Brake force control for a vehicle characterized in that the final target deceleration change rate correction means at the time of stepping back decreases the decrease rate of the final target deceleration with respect to the decrease in the braking operation amount as the turning radius of the vehicle decreases. apparatus. The vehicle braking force control device according to claim 1 or 2 ,
The final target deceleration change rate correcting means at the time of stepping back returns the final target deceleration with respect to the decrease in the braking operation amount so that the final target deceleration returns to the driver reference target deceleration before the braking operation amount decreases to 0. A braking force control device for a vehicle, which determines a decrease speed of the vehicle.

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