JP3163774B2 - Vehicle turning judgment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle turning judgment method for judging whether a vehicle is in a turning state during antilock control, and more particularly to a technique for judging using a wheel speed of each wheel. It is.

[0002]

2. Description of the Related Art There is a method for determining whether or not a vehicle is in a turning state from the relationship between the wheel speed of a left wheel of a vehicle and the wheel speed of a right wheel. This is a method in which the wheel speeds are acquired at the same time and the vehicle is in a turning state when the difference between the two is greater than the set value.

[0003]

However, with this conventional method, it is not possible to obtain a correct determination result during the antilock control. This is because during the anti-lock control, the brake pressure of the left wheel and the brake pressure of the right wheel are periodically increased and decreased, respectively. At that time, the brake pressures of the two wheels usually change asynchronously. This is because, even in the straight traveling state, there may be a difference greater than the set value between the wheel speeds acquired simultaneously for the left wheel and the right wheel.

An object of the present invention is to provide a method for determining whether a vehicle is in a turning state during antilock control, based on the assumption that wheel speed is used.

[0005]

SUMMARY OF THE INVENTION In order to solve this problem, the present invention increases the brake pressure of each wheel at the time of vehicle braking based on the vehicle speed and each wheel speed of a plurality of wheels to lock each wheel. A method of determining whether or not the vehicle is in a turning state during execution of anti-lock control to prevent the vehicle from falling into a turning state. When the wheel acceleration is equal to the reference acceleration common to both vehicle speeds, the deviation of each wheel speed from the vehicle speed is obtained. If the difference between the two obtained deviations is larger than a set value, the vehicle is in a turning state. Is determined.

[0006] The "vehicle speed" here is, for example,
The vehicle speed estimated based on the wheel speeds of a plurality of wheels can be selected, and the traveling speed of the vehicle center of gravity detected by a Doppler speed sensor or the like can be selected.

[0007]

The respective wheel speeds when the wheel acceleration of each wheel coincides with the reference acceleration common to both wheels are likely to have substantially the same phase when the fluctuation of each wheel speed is approximated by the periodic fluctuation. Therefore, if the wheel speeds having the same wheel acceleration are compared with each other, the result does not need to be affected by the asynchronousness of the two wheel speeds. But that is not enough. This is because, although having the same wheel acceleration, the two wheel speeds are usually obtained under different vehicle speeds. Therefore, if the deviations of the wheel speeds from the vehicle speed are compared with each other, it is possible to compare the wheel speeds while eliminating the effect of the vehicle speed mismatch.

Based on the above findings, in the vehicle turning determination method according to the present invention, the wheel acceleration of each of the left wheel and the right wheel of the vehicle during the antilock control is set to a common reference value. The deviation of each wheel speed from the vehicle speed at the time when the acceleration coincides with the vehicle speed is obtained. If the difference between the two obtained deviations is larger than a set value, it is determined that the vehicle is in a turning state.

[0009]

As described above, according to the present invention, without being affected by asynchronous and periodic fluctuation of each wheel speed,
The effect is obtained that the determination as to whether the vehicle is in a turning state using the wheel speed can be made accurately during the antilock control.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An anti-lock type brake system using a vehicle turning judgment method according to an embodiment of the present invention will be described below in detail with reference to the drawings.

In FIG. 2, reference numeral 10 denotes a brake pedal, which is linked to a master cylinder 14 via a booster 12. The master cylinder 14 is of a tandem type in which two pressurizing chambers are arranged in series with each other, and generates a brake pressure of the same height in the pressurizing chambers.

The brake system is an X-pipe type in which two independent brake systems are arranged in an X-shape.
In the first brake system, one pressurizing chamber of the master cylinder 14 is connected to a wheel cylinder 26 of the brake of the left rear wheel RL via a liquid passage 20, a normally open solenoid valve 22, and a liquid passage 24. Liquid passages 20, 3
0, normally open solenoid valve 32 and liquid passage 34
And is connected to the wheel cylinder 36 of the brake of the right front wheel FR. On the other hand, in the second brake system, the other pressurizing chamber is connected to the wheel cylinder 46 of the brake of the left front wheel FL via the liquid passage 40, the normally open solenoid valve 42 and the liquid passage 44, and the liquid passage 40 , 48, via a normally open solenoid valve 50 and a fluid passage 52 to be connected to a brake wheel cylinder 54 for the right rear wheel RR.

In the first brake system, the liquid passage 24 passes through a normally closed solenoid valve 60, and the liquid passage 34 also passes through a normally closed solenoid valve 6.
Each is connected to a reservoir 64 through a second line. The reservoir 64 is connected to a suction port of a pump 66, and a discharge port thereof is connected to the liquid passage 20. on the other hand,
In the second brake system, the liquid passage 44 passes through a normally closed solenoid valve 68 and the liquid passage 52
Are connected to a reservoir 72 via a normally closed solenoid valve 70, respectively. The reservoir 72 is connected to a suction port of a pump 74, and a discharge port thereof is connected to the liquid passage 40. The two pumps 66 and 74 are driven by a common motor 76.

Therefore, for example, with respect to the brake pressure of the left rear wheel RL, a pressure-increasing state is realized by setting both the solenoid valves 22 and 60 to a non-energized state.
The holding state is realized by setting only the energized state, and the depressurized state is realized by setting both the solenoid valves 22 and 60 to the energized state. The same applies to the brake pressures of the other wheels. That is, the brake pressure of each wheel is selectively realized in a pressure-increasing state, a holding state, and a pressure-reducing state by a combination of two solenoid valves. The signals supplied to the solenoids of the respective solenoid valves to realize the holding state and the pressure reducing state are referred to as a pressure increasing pulse, a holding pulse and a pressure reducing pulse.

The electromagnetic valves 22 and the like are controlled by an electronic control unit 80. As shown in FIG. 3, the electronic control device 80 is mainly configured by a computer 82,
It includes a CPU 84, a ROM 86, a RAM 88, a timer 90, an input interface circuit 92, and an output interface circuit 94. The motor 76 and the solenoid valve 22 are connected to the output interface circuit 94 via each driver 96. On the other hand, the input interface circuit 92 is connected to the
The wheel speed sensors 100, 102, 104, 106 and the stop lamp switch 110 (see FIG. 2) are respectively connected. Each of the wheel speed sensors 100 to 106 detects the rotation of a rotor that rotates together with each wheel. The stop lamp switch 110 detects a depression of the brake pedal 10 by a driver.

As shown in FIG. 4, various programs necessary for antilock control are stored in the ROM 86 in advance. Hereinafter, representative programs will be described.

(1) Wheel Speed Calculation Routine This routine is executed by the wheel speed sensors 100 to 106 of each wheel.
Based on the output signal from, sequentially calculates the wheel speed V _W of each wheel. The calculation result is stored in the RAM 88 in association with each wheel.

(2) Wheel acceleration calculation routine This routine sequentially calculates the wheel acceleration V _W ′ by differentiating the wheel speed V _W calculated by the wheel speed calculation routine with respect to time. The calculation result is stored in the RAM 88 in association with each wheel.

(3) Estimated vehicle speed calculation routine This routine calculates the estimated vehicle speed V _SO by estimating that the wheel speed V _W of the fastest wheel having the maximum wheel speed V _W among the four wheels represents the vehicle speed. After the wheel acceleration V _W 'of the fastest wheel exceeds the predetermined upper limit, the vehicle speed is estimated by fixing the upper limit to the estimated upper vehicle speed V _SO . The calculation result is R
AM88.

(4) Estimated vehicle deceleration calculation routine This routine sequentially calculates the estimated vehicle deceleration V _SO 'by differentiating the estimated vehicle speed V _SO calculated by the estimated vehicle speed calculation routine with respect to time. The calculation result is RAM8
8 is stored.

(5) Wheel Speed Deviation Calculation Routine This routine is performed individually for each wheel for the estimated vehicle speed V _SO.
Sequentially calculates the wheel speed deviation ΔV obtained by subtracting the wheel speed V _W from. Further, the value of the wheel speed deviation ΔV when the wheel acceleration V _W ′ of each wheel decreases to the negative reference acceleration G1 is determined as the specific wheel speed deviation ΔV _SN . The calculation result is stored in the RAM 88 in association with each wheel. Note that the reference acceleration G1 is a variable value calculated based on the estimated vehicle body deceleration V _SO '. FIG. 1 is a graph showing an example of the relationship between the wheel speed deviation ΔV and the specific wheel speed deviation ΔV _SN .

(6) Turn Determination Routine This routine determines whether or not the vehicle is turning, during the antilock control, by diverting the four wheel speed sensors 100 to 106. The determination result indicates that the vehicle is not currently in a turning state in the OFF state, while the RAM 88 indicates the contents of a turning flag indicating that the vehicle is in the turning state in the ON state.
Is stored. This routine is represented by a flowchart in FIG. 5, and details thereof will be described later.

(7) Hydraulic pressure control mode determination routine This routine is executed when each wheel has a tendency to lock.
A hydraulic control mode suitable for performing antilock control for increasing or decreasing the brake pressure of each wheel so that each wheel does not fall into the locked state is sequentially determined for each wheel. The determination result is stored in the RAM 88 in association with each wheel. Since the basic method of mode determination in this routine is a general one, it will be briefly described with reference to the graph of FIG.

The wheel acceleration V _W 'is equal to the reference acceleration G1.
(Note that in FIG. "ΔG1" is a is intended to impart a hysteresis characteristic with respect to a result of comparison between the wheel acceleration V _W 'and reference acceleration G1) from the time of drops, the wheel speed V _W is estimated vehicle speed Reference wheel speed decrease ΔV with respect to V _SO
It is determined that the decompression mode should be executed when the pressure drops by _R (described later). That is, the wheel speed deviation ΔV at a certain time is the specific wheel speed deviation ΔV _SN and the reference wheel speed reduction amount ΔV
It is determined that the decompression mode should be executed when the value increases to the sum of _R.

Subsequently, by executing the pressure reduction mode, when the wheel acceleration V _W ′ increases to the negative reference acceleration G 2, it is determined that the pressure reduction mode should be ended and the mode should be shifted to the holding mode. Thereafter, by executing the holding mode, the wheel acceleration V _W ′ is changed to the positive reference acceleration G4 (note that “ΔG
4 "is for imparting a hysteresis characteristic to the comparison result between the wheel acceleration V _W 'and the reference acceleration G4).
V is when reduced to the sum of the specific wheel speed deviation [Delta] V _SN and the reference wheel speed decrease amount [Delta] V _R, to exit the hold mode is determined as to execute a pulse increase mode. Since this pulse pressure increasing mode is a mode in which the rapid pressure increasing mode and the gentle pressure increasing mode are performed in that order, it is first determined that the rapid pressure increasing mode should be executed, and the execution time of the pressure decreasing mode and the estimated vehicle deceleration V _SO ′
When the output of all of the pulse numbers n determined based on the above is completed, it is determined that the rapid pressure increase mode should be terminated and the slow pressure increase mode should be executed.

Thereafter, the wheel speed deviation ΔV at a certain time
Is the latest specific wheel speed deviation ΔV _SN and the reference wheel speed reduction amount ΔV
When the value increases to the sum of _R , the gradual pressure increase mode is ended, that is, it is determined that the first control cycle is ended and the pressure reduction mode in the second control cycle is to be executed.
Thereafter, the control mode is sequentially determined in the same manner.

In this routine, anti-lock control is performed independently for left and right front wheels, and low select control is performed for left and right rear wheels, which is simultaneous left and right control.

(8) Reference Wheel Speed Reduction Calculation Routine This routine includes a variable coefficient K (0 to 1) and an estimated vehicle speed V
A routine for sequentially calculating a reference wheel speed decrease amount [Delta] V _R as the product of the _SO, in which the direction of the cornering coefficient K is calculated as greater than when traveling straight. Calculation result is RAM
88. In the present embodiment, the reference wheel speed decrease amount [Delta] V _R is used as a common value for all the wheels. This routine is represented by a flowchart in FIG. 7, and details thereof will be described later.

(9) Pressure Reduction Mode Execution Routine This routine calculates the duty ratio of the pressure reduction pulse of the solenoid valve corresponding to each wheel based on the estimated vehicle deceleration V _SO 'and the wheel acceleration V _W ' at the start of the pressure reduction mode. And decide
A pressure reduction pulse is output to each solenoid valve according to the duty ratio.

(10) Holding Mode Execution Routine This routine outputs a holding pulse to the solenoid valve corresponding to each wheel.

(11) Rapid pressure increase mode execution routine This routine outputs a pressure increase pulse to the solenoid valve corresponding to each wheel.

[0032] (12) slow increase mode execution routine This routine pressure increase pulse in the solenoid valve corresponding to each wheel, a routine for outputting at a longer holding time T ₁ in the rapid increase mode, turning and it outputs a pressure increase pulse towards the time is at a short retention time T ₁ from the time of straight. This routine is shown in the flowchart of FIG. 8, and the details will be described later.

Here, the turning determination routine will be described in detail.

First, the principle of the turning determination will be described. For convenience of description, as shown in FIG. 9, the left front wheel FL of the four wheels is a first wheel, the right front wheel FR is a second wheel, the left rear wheel RL is a third wheel, and the right rear wheel RR is a fourth wheel. Let's say four wheels. Also, only a left turn will be representatively described, and a description of a right turn will be omitted.

Before the anti-lock control, since the wheelslip is small, the second wheel is the outermost wheel and the third wheel is the innermost wheel. At this time, the following relationship is established between the wheel speed V _W of each wheel. (a) Wheel speed V _W of the first wheel (1) <estimated vehicle speed V _SO (b) Wheel speed V _W of the second wheel (2)> Wheel speed V _W of the first wheel (1) (c) Third Wheel speed V _W (3) <Estimated vehicle speed V _SO

On the other hand, during the antilock control, there are two differences between before and after the antilock control. That, during antilock control, since the side slip of the wheels is large, the first wheel is the outermost inner race, and that tends to fourth wheel is the most outer ring is strong in anti-lock control of each wheel wheel speed V _W is periodically varies, and is're a different from the anti-lock control before in that the wheel speeds V _W is usually not changed in synchronization with each other. Therefore, if the above relationship is used as it is, the turning determination during the antilock control cannot be correctly performed.

[0037] Therefore, first, adopted the following approach in order to solve the asynchronous nature of the problem of the wheel speed V _W. That is, when comparing the wheel speeds V _W between different wheels, the wheel speeds obtained under the same wheel acceleration V _W ′ are not compared with the wheel speeds V _W obtained at the same time. This is a method of comparing V _{W with} each other. However, simply, just by comparing the wheel speed V _W to each other with the same wheel acceleration V _W 'is not sufficient. Because those wheel speeds V
_{This is because W} is generally obtained under different estimated vehicle speeds V _SO . Therefore, the same wheel acceleration V
By comparing deviations of each wheel speed V _{W from} the estimated vehicle speed V _SO under _W ′, the phase and the vehicle speed when the fluctuation of each wheel speed V _W is approximated by the periodic fluctuation are substantially equal. It was it possible to compare the wheel speed V _W with each other under. If this method is adopted, the equations (a) to (c) can be modified as follows.

(A) ′ The specific wheel speed deviation ΔV _{SN of} the first wheel
(1)> A Here, “the specific wheel speed deviation ΔV of the first wheel”
_SN (1) "as described above and, when the wheel acceleration V _W 'falls below the reference acceleration G1, which is the difference between the wheel speed V _SO and the first wheel of the wheel speed V _W (1). Other specific wheel speed deviation Δ
The same applies to V _SN . (b) ′ The specific wheel speed deviation ΔV _{SN of} the first wheel (1) −second
Wheel specific wheel speed deviation ΔV _SN (2)> B (c) ′ Third specific wheel speed deviation ΔV _SN (3)> C

Further, as described above, the following relationship is adopted in consideration of the fact that the fourth wheel is the outermost wheel and the low select control is performed on the left and right rear wheels. That is, strong four fourth tendency wheel slip ratio becomes the minimum is the most outer one of the wheels, after all, because the tendency of the wheel speed V _W of the fourth wheel coincides with the estimated vehicle speed V _SO is strong, following The relationship expressed by the formula was also adopted. (d) Specific wheel speed deviation ΔV _{SN of} the fourth wheel (4) <D

In short, the four conditions that must be satisfied at the same time when the vehicle is turning during the antilock control are set as follows. (a) First condition: specific wheel speed deviation ΔV _SN (1)> A (b) Second condition: specific wheel speed deviation ΔV _SN (1) −specific wheel speed deviation ΔV _SN (2)> B (c ) Third condition: specific wheel speed deviation ΔV _SN (3)> C (d) Fourth condition: specific wheel speed deviation ΔV _SN (4) <D

The value of A is, for example, 4 km / h, the value of B is, for example, 2 km / h, and the value of C is, for example, 4 km / h.
For example, 1 km / h can be selected as the values of h and D, respectively. In addition, the determination method is not limited to the stage after the start of the first pressure reduction mode in the antilock control,
Even at the stage when the brake pedal 10 is the wheel speed V _W to depressed with excessive force in relation to the friction coefficient of the road surface is started drop, it is effective. If it is defined that the "antilock control" is started immediately after the vehicle braking starts and the wheel acceleration _VW 'decreases to the reference acceleration G1, this turning determination method is effective during the antilock control. On the other hand, if it is defined that “anti-lock control” is started from the time when the first depressurization mode is started, this turning determination method is performed not only during the anti-lock control but also during the anti-lock control. The period from when the wheel acceleration V _W ′ decreases to the reference acceleration G1 immediately after the start of vehicle braking to when the first pressure reduction mode is started, that is, when the brake pedal 10 exerts an excessive force in relation to the road surface friction coefficient. It can be said that the device effectively functions even during the period in which the antilock control is about to be started because the vehicle is depressed.

Then, whether or not these four conditions are simultaneously satisfied is determined for each of the left and right front wheels. When the four conditions are simultaneously satisfied for any one of the front wheels,
It is determined that the vehicle is in a turning state.

Note that a right turn can be considered according to a left turn.

Next, the turning determination routine will be described in detail with reference to FIG. This routine is sequentially executed for four wheels. In the execution of this routine each time, first, in step S1 (hereinafter simply referred to as S1; the same applies to other steps), the wheel to be executed this time in this routine is one of the left and right front wheels. It is determined whether or not, and if not, the determination is NO and one execution of this routine ends, but if so, the determination is YES and the steps after S2 are executed.

First, in S2, it is determined whether the specific wheel speed deviation ΔV _SN (1) of the first wheel is larger than A,
If so, the determination is YES, and in S3, it is determined whether a value obtained by subtracting the specific wheel speed deviation ΔV _SN (2) of the second wheel from the specific wheel speed deviation ΔV _SN (1) is larger than B. . If so, the determination is YES, and in S4, it is determined whether the specific wheel speed deviation ΔV _SN (3) of the third wheel is larger than C. If so, the determination is YES
In S5, the specific wheel speed deviation ΔV of the fourth wheel
_It is determined whether _SN (4) is smaller than D. If so, the determination is YES, the turning flag is turned on in S6, and one cycle of this routine is completed.

On the other hand, if any one of the determinations in S2 to S5 is NO, it is determined in S7 whether the specific wheel speed deviation ΔV _SN (2) is larger than A. If the determination is YES, in S8, the specific wheel speed deviation ΔV of the first wheel is calculated from the specific wheel speed deviation ΔV _SN (2).
_It is determined whether the value obtained by subtracting _SN (1) is greater than B. If so, the determination is YES, and in S9, it is determined whether the specific wheel speed deviation ΔV _SN (4) is greater than C. If so, the determination is YES and S1
At 0, it is determined whether or not the specific wheel speed deviation ΔV _SN (3) is smaller than D. If so, the determination is YES, the turning flag is set to the ON state in S6, and one cycle of this routine is completed.

In any of the determinations in S7 to S10, N
If it is O, in S11, the turning flag is set to OF.
The state is changed to the F state, and one execution of this routine is completed.

In this embodiment, the vehicle is determined to be in a turning state if all four conditions are satisfied. For example, if the second condition is satisfied, the vehicle is determined to be in a turning state. It is determined that the vehicle is in a turning state if all of the second condition and one other condition are satisfied, or the second condition and the other two conditions are determined.
If all of these conditions are satisfied, it can be determined that the vehicle is in a turning state.

In the present embodiment, the second condition is that the difference in the specific wheel speed deviation ΔV _SN between the left front wheel FL and the right front wheel FR is larger than B. The difference in the specific wheel speed deviation ΔV _SN between one of the front wheels and one of the left and right rear wheels and the one at the diagonal position with respect to one of the left and right front wheels may be larger than B.

Next, the reference wheel speed reduction amount calculation routine will be described in detail with reference to FIG.

At each execution of this routine, first, S
At 101, it is determined whether the vehicle is currently in a turning state, that is, whether a turning flag is in an ON state,
Otherwise, the determination is NO, and in S102, the value of the coefficient K is calculated based on the estimated vehicle body deceleration V _SO '.
In addition, the reference wheel speed reduction amount ΔV _R is calculated as a product of the estimated vehicle speed V _SO and the estimated vehicle speed V _{SO in} S103. This completes one execution of this routine.

On the other hand, if it is assumed that the vehicle is in a turning state, the determination in S101 becomes YES, the value of the coefficient K is calculated in S104 in the same manner as in S102, and then the value is fixed in S105. Value α (for example,
5%), the value of the coefficient K is corrected. Then, the process proceeds to S103.

[0053] Thus, the value of the coefficient K than in the straight traveling state toward the turning state is increased, the value of the reference wheel speed decrease amount [Delta] V _R becomes larger, the brake pedal force in the turning state in relation to the friction coefficient of the road surface if it becomes excessively large, no longer it started simplifies anti-lock control, also, since the reference wheel speed decrease amount [Delta] V _R is also a starting condition each time decompression mode for the second time after antilock control is started In this case, the second and subsequent pressure reduction modes in the antilock control cannot be easily started. Also, anti-lock control is started becomes brake pedal force is excessive in the straight traveling state, if the transition to the middle turning state, the reference wheel speed decrease amount [Delta] V _R is increased, thereafter, pressure decrease mode is easy Will not start. As a result, in any case, excessive pressure reduction due to antilock control during turning is prevented. Further, when the vehicle is shifted from the turning state to the straight state during antilock control, since the reference wheel speed decrease amount [Delta] V _R is changed to be suitable for straight traveling state, after the transition to the straight state of each wheel There is no tendency for slip to increase.

Next, the slow pressure increase mode execution routine will be described in detail with reference to FIG.

This routine is sequentially executed for each wheel. In each execution of this routine, first, in S201, it is determined whether or not the pulse pressure increase mode is currently selected for a wheel to be executed this time in this routine (hereinafter, referred to as a current target wheel). Otherwise, the determination is NO, and one cycle of this routine is finished. If so, the determination is YES, and in S202, it is determined whether the slow pressure increase mode is currently selected for the target wheel this time. Is determined. Otherwise, the judgment is N
The result is O, and one cycle of this routine is finished. If so, the determination is YES, and in S203, whether or not the vehicle is currently turning, that is, the turning flag is ON.
It is determined whether it is in the state. Assuming that it is not the currently turning, a negative decision (NO) is obtained in S204, it is determined according to the normal rules the length of holding time T _1, at the same pressure increase pulse time target as a combination of pressure increase pulse width T ₂ Output to each solenoid valve corresponding to the wheel.

[0056] On the contrary, assuming that the vehicle is in a turning state, the determination is YES in S203, in S205, the holding time T ₁ is determined to a constant value which is expected. This value is the shorter becomes than always normal value of the retention time T _1.

Accordingly, in the present embodiment, the holding time T ₁ is shorter in the turning state than in the straight traveling state, so that the antilock control is started in the turning state or the turning is performed during the antilock control. In the case of transition to the state, the number of pressure increase pulses output within a fixed time in each slow pressure increase mode increases, the pressure increase gradient becomes steep, and excessive pressure reduction in the turning state is avoided. Further, when the vehicle is shifted from the turning state to the straight state during antilock control, the holding time T ₁ is is changed to be suitable for straight traveling state, the wheels slip after migration to the straight state increases It does not have a tendency to do so.

In short, in this embodiment, in the turning state, the conditions for starting each pressure reduction mode (including the conditions for starting the antilock control) are stricter than in the straight traveling state, and in the slow pressure increasing mode. In cooperation with the steep hydraulic pressure gradient, excessive decompression in the turning state is avoided, and extension of the braking distance due to the turning state is reliably avoided.

In this embodiment, if the vehicle shifts from the turning state to the straight running state during the antilock control, the conditions for starting the pressure reduction mode and the hydraulic pressure gradient in the slow pressure increasing mode are suitable for the straight running state. Because of the change, the slip of each wheel does not tend to increase after the shift to the straight traveling state.

The embodiment of the present invention has been described in detail with reference to the drawings. However, the present invention is used for purposes other than the prevention of excessive decompression in the turning state, and the present invention departs from the scope of the claims. Instead, the present invention can be implemented in various modified and improved forms based on the knowledge of those skilled in the art.

[Brief description of the drawings]

FIG. 1 is a graph for explaining a relationship between a wheel speed deviation ΔV and a specific wheel speed deviation ΔV _SN in a vehicle turning determination method according to one embodiment of the present invention.

FIG. 2 is a system diagram showing an anti-lock type brake system using the vehicle turning determination method.

FIG. 3 is a diagram conceptually showing a configuration of an electronic control device in FIG. 2;

FIG. 4 is a diagram conceptually showing a configuration of a ROM in FIG. 3;

FIG. 5 is a flowchart illustrating a turning determination routine in FIG. 4;

FIG. 6 is a graph showing an example of control by the antilock brake system.

FIG. 7 is a flowchart showing a reference wheel speed reduction amount calculation routine in FIG. 4;

FIG. 8 is a flowchart showing a slow pressure increase mode execution routine in FIG. 4;

FIG. 9 is a diagram for explaining numbers assigned to respective wheels.

[Explanation of symbols]

22, 32, 42, 50, 60, 62, 68, 70 Solenoid valve 26, 36, 46, 54 Wheel cylinder 80 Electronic control unit 100, 102, 104, 106 Wheel speed sensor

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-170855 (JP, A) JP-A-3-7649 (JP, A) JP-A-3-500331 (JP, A) (58) Survey Field (Int.Cl. ⁷ , DB name) B60T 8/58 B60T 8/24

Claims (1)

(57) [Claims] 1. A vehicle according to claim 1, wherein said vehicle is controlled by increasing or decreasing the brake pressure of each wheel during vehicle braking based on the vehicle speed and each wheel speed of said plurality of wheels to prevent each wheel from falling into a locked state. A method of determining whether or not the vehicle is in a turning state, wherein, for each of the left wheel and the right wheel of the vehicle during the anti-lock control, when the wheel acceleration of each wheel matches a reference acceleration common to both, A vehicle turning determination method comprising: obtaining a deviation of each wheel speed from a vehicle speed; and determining that the vehicle is in a turning state when a difference between the obtained two deviations is larger than a set value.