JPH037648A - Anti-lock control device of vehicle - Google Patents

Abstract

PURPOSE:To secure the braking force even when the vehicle is running on a badly conditioned road by restricting decompression of the braking liquid when it is judged that the varying condition of the wheel speed is synchronized with the vertical vibrating condition of the sub-spring structure during anti-lock control. CONSTITUTION:When a control logic circuit is in anti-lock control mode, a periodic variation of the front wheel speed Vwf is sensed by the period measuring circuit 15a of a badly conditioned road judging part 15, while another period measuring circuit 15c senses the periodic vertical vibration of the sub-spring structure sensed by a high-G generation sensor circuit 15b, and the two values obtained are compared by a synchronization judging circuit 15d. If judgement is such that the periodic variation of the wheel speed is synchronized with the periodic vertical vibration of the sub-spring structure, the decompression of the brake liquid is restricted accordingly. Thus the premature decompression start of the braking liquid pressure at the time of braking on a badly conditioned road is prevented, and the braking force can be secured.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an anti-lock control method for preventing wheels from locking during braking of a vehicle, and in particular to an anti-lock control method that improves braking characteristics on rough roads. Regarding equipment.

(Prior art) In general, anti-lock control devices for vehicles convert wheel speeds detected by wheel speed sensors into electric signals for the purpose of ensuring vehicle steering performance and running stability and shortening braking distance during braking. Based on this, the brake fluid pressure control mode is determined, and a hold valve consisting of a normally open solenoid valve and a decay valve consisting of a normally closed solenoid valve are opened and closed to increase, maintain, or reduce the brake fluid pressure. It is controlled by a control unit containing a microcomputer.

FIG. 8 shows changes in wheel speed Vw, wheel acceleration/deceleration dVw/d, t, and brake fluid pressure pw in such anti-lock control, as well as hold signal H3 and decay signal DS for opening and closing the hold valve and decay valve. FIG.

When the brake is not operated while the vehicle is running, the brake fluid pressure Pw is not pressurized, and both the hold signal H3 and the decay signal DS are OFF.
Therefore, the hold valve is open and the decay valve is closed, but as the brakes are operated, the brake fluid pressure p
w is pressurized from time to and rapidly increases in normal mode),
The wheel speed Vw decreases due to the dirt. When the wheel deceleration (negative acceleration) dVw/dt reaches a predetermined dark value, for example -1, IG at time 1, 1, anti-lock control is started from this time t1. On the other hand, at time 1.1, a pseudo wheel speed Vf is set that decreases linearly with a deceleration gradient θ of -1.1G from a speed (Vw - Δ■) lower by a constant speed Δ■ than the wheel speed Vw. be done.

Then, at a time t2 when the wheel deceleration dVw/dt reaches a threshold value Gnax for achieving a predetermined maximum deceleration, the hold signal H3 is turned on to close the hold valve and maintain the brake fluid pressure Pw.

As the brake fluid pressure pw is maintained, the wheel speed Vw further decreases, and the wheel speed Vw becomes equal to the pseudo wheel speed Vf at time t3, but at this time t3, the decay signal DS is turned ON and the decay valve is opened. Start reducing the brake fluid pressure pw. Due to this pressure reduction, the wheel speed turns to acceleration after reaching the low peak at time t4, but at this low peak time t4, the decay signal DS is turned OFF, the decay valve is closed, and the pressure reduction of the brake fluid pressure pw is completed. Maintain pressure pw. Although the wheel speed Vw reaches /'% peak at time t7, the brake fluid pressure pw starts to be increased again from time t7. The force n pressure here can be determined by turning the hold signal HS 0N-OFF in relatively small steps to obtain the brake fluid pressure p.
The pressurization and holding of W are repeated alternately, thereby slowly increasing the brake fluid pressure Pw and decreasing the wheel speed Vw, and the depressurization mode is generated again from time point 18 (corresponding to t3). Note that the speed vb (=vβ
+0.15Y), and the time t6, which is increased from the low peak speed ■β by an amount corresponding to 80% of the speed difference Y, to the speed Vc (=Vff +0.8Y) is detected. The first pressurization period Tx starting from time t7 is equal to the period Δ between the above-mentioned times t5 and t6.
The subsequent holding period or pressurization period is determined by determining the road surface friction coefficient μ based on the calculation of the average acceleration (Vc-Vb)/ΔT at T, and the subsequent holding period or pressurization period is determined by the wheel deceleration dVw detected immediately before the holding or pressurization period. /dt. By combining pressurization, holding, and depressurization of the brake fluid pressure pw as described above, it is possible to reduce the vehicle speed by controlling the wheel speed Vw without locking the wheels.

By the way, when a vehicle equipped with the above-mentioned anti-lock control device drives on a rough road with many bumps, the wheels often become suspended in the air, so if the brakes are activated at that time, Wheels in the air decelerate rapidly, and once a wheel that has decelerated rapidly starts rotating again when it touches the ground, the change in wheel speed exhibits a different behavior than on a normal road. That is, when the vehicle is traveling on a rough road, the control cycle becomes faster and the amplitude of the speed change in the wheel speed Vw becomes larger than in the normal case.

Therefore, in conventional anti-lock control, when anti-lock control is started by applying the brakes while driving on a rough road as described above, changes in wheel speed caused by the rough road are compared to wheel speeds controlled by anti-lock control. Not only will this result in misidentification, resulting in poor controllability, but it will also cause changes in wheel speed! I
Since depressurization is frequently started, there is a problem in that the brake fluid pressure does not increase and the braking distance becomes longer. Therefore, an anti-skid control method has been proposed that takes into account vertical changes in vehicle height as a criterion for determining rough roads, as disclosed in, for example, Japanese Patent Application Laid-Open No. 63-232059, but the above-mentioned problems arise. This did not fundamentally resolve the issue.

(Purpose of the Invention) The present invention provides an anti-slip system that can prevent early depressurization of brake fluid pressure during braking on rough roads and secure braking force by accurately determining rough roads. The purpose is to provide a lock braking device.

(Structure of the Invention) In order to achieve the above object, the present invention includes means for detecting periodic fluctuations in wheel speed and means for detecting periodic upward and downward vibrations of the unsprung portion of the vehicle. During control, the wheel speed fluctuation state and the vertical vibration state of the unsprung portion are compared, and if it is determined that the two are synchronized, the brake fluid pressure reduction is limited in response. .

(Example) Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 is a block diagram showing the configuration of a three-system antilock control device used to implement an embodiment of the present invention. In the figure, 1 is sent to the left front wheel speed sensor, and 2 is sent to each control logic circuit 9, 10, ]2. This signal is also sent to a virtual vehicle speed deceleration gradient determination circuit 14 that determines the deceleration gradient of the pseudo vehicle speed Vv, and a signal determining this deceleration gradient is sent to each control logic circuit 9, 10, and 12.

On the other hand, a rough road determining section 15 that determines whether the rough road establishment condition is satisfied or not.
16.17.18 are provided. In addition, the lower parts of the springs of the left front wheel, right front wheel, left rear wheel, and right rear wheel are each
Sensors 31 to 34 are provided, and these G sensors 3
1 to 34 detect the acceleration and deceleration of the vertical vibration of each unsprung portion, and output the detected accelerations and decelerations to rough road determining units 15 to 18, respectively. The rough road determination units 15 to 18 receive signals from the wheel speed calculation circuits 5 to 8 and signals from the G sensors 31 to 34, respectively, and determine whether the conditions for forming a rough road are satisfied. When it is established, a signal indicating this is output to the control logic circuit 9.10.12.

Control logic circuits 9, 10 and 1 are configured to control each system speed V.
The hold hull right front wheel speed sensor of each system based on the signal that detects sl~Vs3 and the pseudo vehicle speed V'v,
3 is a left rear wheel speed sensor, and 4 is a right rear wheel speed sensor.

The outputs of these wheel speed sensors 1-4 are sent to calculation circuits 5-8 for calculation, and signals are obtained for each wheel speed Vwl-Vw4. Out of these four wheel speeds, a signal indicating the front left wheel speed Vwl and a front right wheel speed Vw2 is sent to the control logic circuit 9.10 as a signal indicating the first and second system speeds Vsl and Vs2, respectively. Also, the lower wheel speed of the left rear wheel speed Vw3 and the right rear wheel speed Vw4 is selected by the low select circuit 11, and this is sent to the control logic circuit 12 using the third system speed Vs3 as a hail signal.

Further, a signal instructing each wheel speed Vwl to Vw4 is sent to the virtual vehicle body speed calculation circuit 13, where the fastest wheel speed among the four wheel speeds Vwl to Vw4 is selected (high select). ± the following limit of the fastest wheel speed
The speed limited to IG is calculated as the pseudo vehicle speed Vv. The pseudo vehicle speed Vv obtained in this way is controlled to turn on and off the signal valve and decay valve. In particular, in order to determine the depressurization start point at which the ON control of the decay valve is started, depressurization start point determination sections 19, 20, and 21 are provided for each system, and these depressurization start point determination sections 19 to 21 are configured to perform respective control logics. Circuit 9.
10.12 via switches SWI to SW3, and directly connected to the input terminals of these circuits 9.10.12. And the above switches SW1~
SW3 is turned ON for each system when the anti-lock control is not activated (until the pressure reduction starts in the first control cycle) or when the pressurization mode is in effect, and the pressure reduction starts in the pressure reduction start determination units 19 to 20. Once the starting point is determined, the device is configured to be turned OFF from that depressurizing starting point to the next pressurizing starting point.

FIG. 2 is a diagram showing the contents of the rough road determining section 15. The signal Vwl, which indicates the wheel speed as shown in FIG.
The period Ta of the signal waveform is measured, and the result is sent to the synchronization determination circuit 15d. In addition, the above-mentioned vertical G sensor 31
The signal G1 as shown in FIG. 3(B) obtained from the above is first judged in the high G generation determination circuit 15b as to whether or not it has reached the high G region, and only the signal that has reached the high GwA region is detected as G. The signal is sent to the period measuring circuit 15c, and its generation period is measured. Then, the synchronization determination circuit 15d determines whether or not these two periods are synchronized, and if it is determined that they are synchronized, it is assumed that the rough road determination condition is satisfied.

That is, the rough road determining units 15 to 18 respectively receive the signals from the wheel calculation circuits 5 to 8 and the vertical G sensor 3.
Upon receiving the signals 1 to 34, it is determined whether the rough road establishment condition is satisfied or not.
When the rough road judgment is established, a signal indicating this is output to the control logic circuit 9.10.12.

Next, to explain Fig. 3, Fig. 3(A) shows the fluctuation of the wheel speed Vw in a vehicle traveling on a rough road (undulated road), and Fig. 3(B) shows the fluctuation of the vertical vibration of the wheel. In order to detect the acceleration/deceleration G, it is determined whether the output waveform of the vertical G sensor provided under the spring of each wheel is shown, that is, whether or not they are synchronized.If rYEsJ, the process proceeds to step S7; Turn on the rough road flag and perform anti-lock control to cope with driving on rough roads. Step S4 or Step S6
When the determination is rNOJ, the routine proceeds to step S8, where the rough road flag is turned OFF and normal anti-lock control J is performed.

The above explanation has clarified the rough road determination method applied to the anti-lock control device according to the present invention. Next, an example of the anti-lock control method when such a rough road determination is made will be described below. .

FIG. 5 is a diagram for explaining the operation from the brake fluid pressure point to the first pressure reduction start point, and is a control state diagram of the brake fluid pressure Pw during gentle braking while driving on a rough road. In the following description, each system speed Vsl-Vs3 is represented by the wheel speed Vw.

In the flowchart of FIG. 4, when the rough road flag is turned on, the pseudo wheel speed Vf, which is the reference for determining the brake fluid pressure reduction start point, is lower than this Vf. Ta
and Tb represent the period of fluctuation of the wheel speed Vw and the period of the output waveform of the vertical G sensor, respectively. If the condition 0.95<Tb/Ta<1.05 is satisfied between Ta and Tb, it is determined that the cycle of the vertical G sensor output and the cycle of the wheel speed Vw are synchronized.

The fourth rgJ is a flowchart showing the operation of the aforementioned rough road determining sections 15 to 18 that perform rough road determination using the above method. First, the wheel speed Vw is read in step Sl, and its cycle Ta is measured in step S2. Next, in step S3, the output signal of the vertical G sensor is inputted, and in step S4, the signal inputted in step S3 is detected in the high G region that occurs when driving on a rough road as shown in FIG. 3(B). If it is determined that it has been reached, the period Tb of the generated ``2 lower G'' is measured in step S5. In the next step S6, the ratio T of the period Tb of the above-mentioned vertical G and the period Ta of the wheel speed Vw is
b/Ta is within the range of 0.95 to 1.05.

First, a method of setting the pseudo wheel speeds Vf and vr' will be explained. The pseudo wheel speed Vf and VM are after the brake fluid pressure,
From point A where the deceleration of the wheel speed Vw becomes, for example, 1.1G, it is first set using the following equations (2) and (2).

V f =Vw−Δ■ −・ −・～ ■Vf'=V
w−Δ■′−=−−−−−−・■Here, the value of 8V′ is assumed to be, for example, ΔV, 1,500 km/h.

And after that, the pseudo wheel speed Vf and VM are -1,1
The wheel speed V decelerates at a gradient of G, but then accelerates.
From the point C where the speed difference between W and the pseudo wheel speed Vf becomes more than the above Δ■ (the point where the speed difference between the wheel speed Vw and the pseudo wheel speed Vf' becomes more than the above Δ■'), the vehicle starts decelerating again. 8V until the point where the deceleration of the wheel speed Vw becomes -1.1G.
and ΔV' are set by the above equations ② and 0. Points D and 0 are set in the same manner as from point A, and points from F are set in the same manner as from point 0.

Next, a method for determining the start point of decompression will be described with reference to FIG. In FIG. 5, the - dotted line indicates the state of change in brake fluid pressure Pw when the pressure reduction start point is determined based on the pseudo wheel speed Vf, and the solid line indicates the start of pressure reduction based on the pseudo wheel speed VM when the rough road logic is set. The state of the brake fluid pressure Pw when the point is determined is shown. That is, if the rough road determination is not established, pressure reduction is started at points B, E, and H, respectively, where the wheel speed Vw during deceleration becomes equal to the pseudo wheel speed Vf. Further, if the rough road judgment is established, pressure reduction is started for the first time from the intersection I between the wheel speed Vw during deceleration and the pseudo wheel speed Vf'. The aim of the rough road logic from the brake fluid pressure point to the first pressure reduction start point I as described above is to reduce the frequency of anti-lock activation during gentle braking when driving on rough roads, and to maintain braking force in accordance with the driver's brake pedal force. That's what I tried to do.

Next, FIG. 6 is a diagram for explaining the operation after the second control cycle control starts from the next pressurization start point after the brake fluid pressure Pw starts to decrease based on the pseudo wheel speed Vf'. It is a control state diagram of brake fluid pressure Pw.

Regarding the setting of pseudo wheel speeds Vf and Vf' here, predetermined speed differences Δ■,
From points B, E, and H where the wheel speed Vw is followed by ΔV' and the deceleration of the wheel speed Vw is -1, IG, the points are set to linearly decelerate with a deceleration gradient of -1,1G. Since this is the same as in FIG. 5, duplicate explanation will be omitted.

Furthermore, in FIG. 6, the - dotted line indicates the state of the brake fluid pressure Pw when the pressure reduction start point is determined based on the pseudo wheel speed Vf, and the solid line indicates the state of the brake fluid pressure Pw when the pressure reduction start point is determined based on the pseudo wheel speed Vf'. Indicates the condition.

First, if the rough road judgment is not established at the pressurization start point A where the wheel speed Vw reaches high peak and pressurization of the brake fluid pressure Pw starts, normal anti-lock control is executed and the Intersection point C between wheel speed Vw and pseudo wheel speed Vf
, F, and (), respectively, and pressurization starts from G when the wheel speed Vw reaches a high peak.

On the other hand, if the rough road judgment is established after the pressurization start point A, the predetermined time TI from the pressurization start point A, for example 0.2~
Until 0.3s elapses, the decompression judgment is based on the pseudo wheel speed v.
r', and pressure reduction is started from the intersection of the wheel speed Vw and the pseudo wheel speed Vf'.

Then, if the rough road determination has been established after the pressurization start point A, but the rough road determination has been canceled after T1 time has elapsed from the pressurization start point A, the wheel speed Vw and the pseudo wheel speed Vf
The pressure reduction is started again at the intersection point (3) with the wheel speed Vw and the virtual wheel speed Vr', but if the rough road determination is not canceled even after the T1 time has elapsed, the pressure reduction is started at the intersection point J between the wheel speed Vw and the virtual wheel speed Vr'.

By applying the rough road logic from the second control cycle onwards, during anti-lock control during braking on rough roads, changes in wheel speed on rough roads frequently result in early pressure reduction, resulting in insufficient brake fluid pressure. It is possible to prevent this from happening and also to increase the brake fluid pressure to an appropriate level.

Further, the follow-up speed difference Δ■' of the pseudo wheel speed VM with respect to the wheel speed Vw is normally, for example, Δv'=8■+km/
h, but if pressure reduction is started based on the pseudo wheel speed VM in the previous control cycle and the rough road judgment is still valid at the subsequent pressurization start point, Δ■' is For example, it is changed to Δ■'-ΔV+10km/h.

In this way, when determining the first rough road, Δ■′ is changed to Δ■′
- ΔV + 5 km/h and apply the rough road logic, and after that, after the rough road judgment is still valid and it becomes even more certain that it is a bad road, ΔV' is changed to Δv'=
Since the pseudo wheel speed VM is set in two stages, such as changing to ΔV+10 km/h, it is possible to avoid the adverse effects of applying the rough road logic on a low μ road.

Furthermore, in the rough road logic after the second control cycle, the deceleration gradient of the pseudo vehicle speed Vv between the pressurization start point of the previous cycle and the pressurization start point of the current cycle is set to a predetermined value, For example 0. When the speed is steeper than IG, or when the pseudo vehicle speed Vv is less than a predetermined speed, for example, 15 km.
/h or less, application of the rough road countermeasure is discontinued and brake fluid pressure reduction is started based on the pseudo wheel speed Vf. This makes it possible to avoid the adverse effects of applying the rough road logic on low μ roads or at low speeds.

When the rough road judgment is established and the brake fluid pressure starts to be reduced based on the pseudo wheel speed Vf', a flag indicating this is turned ON. Hereafter, this is the rVf' flag.
It is called.

FIG. 7 is a flowchart 1 showing the operation of the depressurization start point determination units 19 to 21 that perform the depressurization start determination as described above. Below, we will explain the preceding period from the brake fluid pressure point until the first start of depressurization based on the pseudo wheel speed Vf', that is, the period until the Vf' flag turns ON, and the period from when anti-lock control starts to the start of the next pressurization. The period after the second control cycle starting from point 1 will be explained separately.

9. If the signal is ON, proceed to step S30.
Compare the wheel speed Vw and the pseudo wheel speed Vf', and find that Vw≦
If it is a VM, proceed to step S31 and set the VM flag to O.
N, the timer flag is turned OFF in step 327, the decompression mode is set in step 328, and step S2
Start depressurizing at 9. From this pressure reduction point to the next pressurization start point, the switches SW1 to SW3 in FIG. 1 are turned off.

Next, the control after the second cycle of anti-lock control (after the next pressurization start point) will be explained. When the rough road judgment was established in the previous cycle and pressure reduction based on the pseudo wheel speed VM was started, the Vl flag was ON (step 531), so the judgment in step S20 here is rYBsJ. , the process goes to step S32 and the pseudo wheel speed VM is set as Vf'-Vf-If) km/h. Then, the determination at step 322 is rYEs.
Since it is J, the process advances to step 333. Step 333
In , it is determined whether the pseudo vehicle speed is 15 km/h or less, and in the preceding period, it is first determined in step S20 whether or not the VM flag is ON, but here, this determination is rNOJ. Therefore, in step S21, the pseudo wheel speed VM is set as Vf'=Vf-5km/h. Then, in step S22, it is determined whether the anti-lock control is in operation, that is, whether it is after the first pressure reduction start point. 52, the determination in step S22 is r
Since the result is NOJ, the VM flag is set to O in step S23.
FF is left as F, and the process proceeds to step S24, where it is determined whether or not the rough road flag is ON. If the rough road judgment is not established and this judgment is rNOJ, the process goes to step S25 to compare the wheel speed Vw and the pseudo vehicle body speed vr, and if Vw≦Vf, the process goes to step S26 to set the VM flag. OFF
Leave as is. Then, in step S27, the timer flag is left OFF, in the next step S28, a pressure reduction mode is set, and in step S29, both the hold valve and the decay valve are turned ON to perform pressure reduction. In addition, if the rough road determination is established in step S2, 1 and the rough road flannel is 0 rNOJ, the process proceeds to step S34, where a pseudo It is determined whether the deceleration gradient VvG of the vehicle speed Vv is steeper than -0,],G. When the determination in step 533 is [YESJ, or when the determination in step 334 is rYEsJ, the process goes to step S25 and the wheel speed Vw, ! : The start of pressure reduction is determined by comparison with the pseudo wheel speed vr.

On the other hand, when the determinations in step S33 and step S34 are both "NO", the process proceeds to step 335, and it is determined whether the rough road flag is ON.

After this second control cycle, if the rough road determination is still valid and the rough road flag is ON, the timer flag is turned ON in step S36. This timer flag is for holding the rough road logic for a predetermined time T1. The process then proceeds to step S30 via step S37, where a determination is made to start depressurization by comparing the wheel speed Vw and the pseudo wheel speed VM. If the rough road determination is not established here and the determination in step S35 is NO, then in step 338, the elapsed time T from the pressurization start point in the second and subsequent control cycles is compared with the predetermined time T1. . Then, if T<TI, the determination in step S38 is "NO".
'', the process goes to step S37 to determine whether or not the timer flag is ON, and when this determination is rYEsJ, the process advances to step S30, where a decompression start determination is performed based on the pseudo wheel speed VM. On the other hand, if T≧T1 and the determination in step 3138 is rYESJ, or if the determination in step S37 is rNOJ, the process proceeds to step S25, where a determination is made to start decompression based on the pseudo wheel speed Vf.

As explained above, according to this embodiment, the brake ON
During the period from this point to the start point of depressurization, it is possible to reduce the frequency of anti-lock operation when the brakes are applied when driving on a rough road, maintain the braking force in accordance with the driver's brake pedal force, and also maintain the
From the th control cycle onwards, brake 3 is used to prevent early start of brake fluid pressure depressurization due to changes in wheel speed on rough roads, or brake 3 is applied to prevent early start of brake fluid pressure depressurization due to changes in wheel speed on rough roads, or early start of brake fluid pressure reduction when the rough road logic is applied when driving at low speeds. This has the effect of avoiding problems such as the occurrence of mouth and bulges.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the configuration of a three-system antilock control device according to the present invention, FIG. 2 is an explanatory diagram of its rough road determination section, and FIG.
Figure 4 is an explanatory diagram of the rough road determination method, Figure 4 is a flowchart showing the rough road determination method, Figure 5 is a control state diagram from the brake ON point to the first depressurization start point, and Figure 6 is after anti-lock control. Control state diagram after the second control cycle, 7th
The figure is a flowchart for explaining a method for determining the start of pressure reduction, and FIG. 8 is a control state diagram in a conventional anti-lock control method. 1 to 4 - Wheel speed sensors 5 to 8 - Wheel speed calculation circuit 9.10.12 - Control loss circuit 11 - Low selection circuit 13 = Simulated vehicle body speed calculation circuit 14 - Simulated vehicle body speed deceleration gradient judgment circuit Ki hydraulic pressure By increasing the hydraulic pressure to an appropriate level, braking distance on rough roads can be shortened. (Effects of the Invention) As is clear from the above description, according to the present invention, it is determined that the fluctuation state of the wheel speed and the vertical vibration state of the unsprung lower part are synchronized by comparing the fluctuation state of the wheel speed and the vertical vibration state of the unsprung lower part. ” When the peak of the acceleration/deceleration of the second vibration reaches a predetermined value, it is determined that the road is rough (wavy road) based on these conditions, and the reduction in brake fluid pressure during anti-lock control is limited. Therefore, it is possible to accurately judge a rough road, thereby preventing a no-brake state when the brake is applied V'' while driving on a rough road, and ensuring braking force. Further, according to this embodiment, the setting of the pseudo wheel speed Vf' used for determining the starting point of depressurization when driving on a rough road is set in two stages, and furthermore, two rough road countermeasures are implemented as shown in steps S33 and S34 in FIG. Since the application of the rough road countermeasure is discontinued when the application discontinuation condition (○R condition) is met, it is assumed that a low μ road is incorrectly determined as a rough road. Starting point determination parts 31 to 34 - Upper and lower G sensor Agent Patent attorney Toshihito Yamamoto t5 0 Publication h ~

Claims (1)

[Scope of Claim] An anti-lock control device that alternately increases or decreases brake fluid pressure based on detection of wheel speed of a vehicle, comprising: means for detecting periodic fluctuations in wheel speed; and an unsprung portion of a vehicle. means for detecting periodic vertical vibrations of the wheel; means for comparing the fluctuation state of the wheel speed during anti-lock control with the vertical vibration state of the unsprung lower portion to determine whether the two are synchronized; An anti-lock control device for a vehicle, comprising: means for limiting reduction in brake fluid pressure in response to a determination by the determining means that the two are synchronized.