JPH1134846A - Abs - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately control a vehicle at all times despite of the changes in the high/low speed of a vehicle body and a state of a road surface. SOLUTION: An antilock brake system is provided with an M operation means 21 which calculates a differential parameter M matching to the difference between a road surface friction force F and a brake torque B based on the road friction force information and brake torque information, an Mω operation means 22 which calculates a wheel speed parameter Mω, which becomes 0 in a lock of the wheel, by compensating and integrating the differential parameter M calculated by the M operation means 21, a dMω/dt operation means 23 which calculates a wheel acceleration parameter dMω/dt by integrating the wheel speed parameter Mω calculated by the Mωoperation means 22, and a solenoid valve control means 26 which controls the hydraulic pressure of a brake device by using the wheel acceleration parameter dMω/dt calculated by the dMω/dt operation means 23.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ABS (antilock brake system) for preventing locking of wheels at the time of sudden braking of a vehicle.
tem) device.

[0002]

2. Description of the Related Art In a conventional ABS device, a hub having a gear is mounted on a wheel, the rotation of the gear is detected by an electromagnetic pickup, and a wheel speed is calculated based on the detected signal. The vehicle speed is calculated based on the detection signal from the vehicle, and the slip ratio is calculated from the wheel speed and the vehicle speed, thereby performing control using the slip ratio.

However, since it is difficult to directly calculate the vehicle speed, the vehicle speed is estimated based on the wheel speed and the detection signal from the acceleration sensor. , Control was inaccurate.

Furthermore, as the vehicle speed decreases, the period of the detection signal from the electromagnetic pickup increases, and the control accuracy decreases. Therefore, the vehicle stops after the vehicle speed starts to decrease by depressing the brake pedal. This is extremely inconvenient for an ABS device that needs to operate until the operation is completed.

[0005]

DISCLOSURE OF THE INVENTION The present invention has been conceived in view of the above circumstances, and provides an ABS apparatus which can always perform accurate control regardless of a change in a vehicle speed or a change in road surface conditions. Is the subject.

In order to solve the above problems, the present invention takes the following technical measures.

According to a first aspect of the present invention, road surface friction force information corresponding to a road surface friction force F acting between a vehicle wheel and a traveling road surface, and an operation between a vehicle wheel and a brake device. AB having an arbitrary number of first sensors capable of obtaining brake torque information corresponding to the brake torque T to be applied
An S device, wherein a difference parameter calculating means for calculating a difference parameter M corresponding to a difference between the road surface frictional force information and the brake torque information from the first sensor, and a difference parameter M calculated by the difference parameter calculating means. A wheel speed parameter calculating means for calculating a wheel speed parameter Mω which becomes 0 when the wheel is locked by correcting and integrating the wheel speed parameter Mω calculated by the wheel speed parameter calculating means. wheel acceleration parameter calculation means for calculating dMω / dt; and brake fluid pressure control means for controlling the hydraulic pressure of the brake device using the wheel acceleration parameter dMω / dt calculated by the wheel acceleration parameter calculation means. An ABS device is provided that features.

[0008] Road surface friction force information and brake torque information are:
Each of them may be obtained directly from one sensor, or may be obtained by calculating a detection signal from the sensor. For example, road surface friction force information can be obtained directly from a single sensor, or a detection signal from a sensor that outputs road surface friction coefficient information corresponding to the road surface friction coefficient μ is multiplied by a constant corresponding to the weight of the vehicle. Can also be obtained. Further, it may be obtained by calculating detection signals from a plurality of sensors.

As the first sensor, for example, a stress sensor composed of a strain gauge for detecting a shear force acting on the axle of the vehicle in each direction can be used, but is not limited to this.

The brake fluid pressure control means controls, for example, an electromagnetic valve incorporated in a hydraulic line of the brake device.

According to a preferred embodiment, there are provided an arbitrary number of second sensors capable of obtaining gravitational acceleration information corresponding to the gravitational acceleration G acting on the vehicle, and the wheel speed parameter calculating means includes a differential parameter M And a gravitational acceleration G based on the gravitational acceleration information to obtain a wheel speed parameter Mω.

The gravitational acceleration information may be obtained directly from one sensor, or may be obtained by calculating a detection signal from the sensor. Further, it may be obtained by calculating detection signals from a plurality of sensors.

When the difference parameter M and the gravitational acceleration G are processed as digital data, the difference between the difference parameter M and the gravitational acceleration G is calculated, for example, at every predetermined time. It can be realized by accumulating them.

According to another preferred embodiment, the wheel speed parameter calculating means integrates a difference between the difference parameter M and a value proportional to a first threshold value corresponding to the peak value of the difference parameter M. , The wheel speed parameter Mω
Get.

According to another preferred embodiment, an arbitrary number of second sensors capable of obtaining gravitational acceleration information corresponding to the gravitational acceleration G acting on the vehicle, and a trajectory of the gravitational acceleration G based on the gravitational acceleration information Gravitational acceleration change rate calculation means for calculating the inclination of the gravitational acceleration G, and first threshold value variable means for changing the first threshold value in accordance with the inclination of the locus of the gravitational acceleration G calculated by the gravitational acceleration change rate calculation means.

In the case where the gravitational acceleration G is processed as digital data, for example, the gravitational acceleration G is stored every predetermined time, and the inclination of the trajectory of the gravitational acceleration G based on the gravitational acceleration information is stored. It is obtained by calculating the difference from the current gravity acceleration G.

According to another preferred embodiment, a two-point difference calculating means for calculating a difference between the wheel speed parameters Mω at predetermined time intervals, and a difference between the wheel speed parameters Mω calculated by the two-point difference calculating means. First threshold changing means for changing the first threshold.

According to another preferred embodiment, a road frictional force change amount for calculating a difference between the value of the road frictional force F at the time of the start of the current pressure reduction and the value of the road surface frictional force F at the time of the start of the previous pressure reduction. A calculating means; and a first threshold varying means for changing a first threshold value in accordance with a change amount of the road friction force F calculated by the road friction force changing amount calculating means.

According to another preferred embodiment, the first threshold changing means changes the first threshold continuously.

The term "continuously changing" means not only a case of changing in an analog manner but also a case in which the inclination of the trajectory of the gravitational acceleration G, the difference in the wheel speed parameter Mω, or the difference in the road frictional force F changes every predetermined time. In this case, the case where the first threshold is necessarily changed according to the change is also included.

According to another preferred embodiment, the first threshold changing means changes the first threshold in a stepwise manner.

When the inclination of the trajectory of the gravitational acceleration G, the difference in the wheel speed parameter Mω, or the difference in the road surface frictional force F changes every predetermined time, the amount of change is equal to or more than a predetermined value. In this case, the first threshold is changed according to the amount of change.

According to another preferred embodiment, the brake fluid pressure control means reduces the brake fluid pressure when the wheel acceleration parameter dMω / dt reaches the second threshold after the brake fluid pressure is reduced. To end.

The second threshold value is set in the vicinity of the value of the wheel acceleration parameter dMω / dt when the wheel slip ratio is optimal.

Of course, the wheel acceleration parameter dMω /
The determination of the end point of the decompression using dt and the determination of the end point of the decompression using the wheel speed parameter Mω or the difference parameter M may be used in combination. In this case, although the determination results of the plurality of controls may be different, it is only necessary to follow the determination result that is determined to be the end point of the pressure reduction after a predetermined minimum pressure reduction period has elapsed since the start of the pressure reduction of the brake fluid pressure.

According to another preferred embodiment, the brake fluid pressure control means increases the brake fluid pressure abruptly when the wheel acceleration parameter dMω / dt reaches the third threshold after the brake fluid pressure is reduced. Apply pressure.

The third threshold value is a wheel acceleration parameter dM in a state where the wheel speed is about the relative vehicle speed.
It is set near the value of ω / dt. This third threshold is
It is larger than the second threshold.

The sudden increase of the brake fluid pressure means that, for example, after the brake oil pressure is reduced, the brake oil pressure is repeatedly increased and maintained at predetermined time intervals to gradually increase the brake oil pressure. This refers to shifting to a state in which the brake hydraulic pressure is increased, but is not limited to this.

According to another preferred embodiment, the difference parameter calculating means calculates a value obtained by subtracting the brake torque T from the road surface friction force F based on the road surface friction force information and the brake torque information from the first sensor. FT is obtained as a difference parameter M.

According to another preferred embodiment, the difference parameter calculating means calculates the difference from the first sensor when the radius of the wheel is R and the distance between the center of rotation of the wheel and the brake caliper of the brake device is r. Of the radius R and the distance r based on the road surface frictional force information and the brake torque information
A value (R / r) F−T obtained by subtracting the brake torque T from a product (R / r) F of the road surface friction force F and the road friction force F is obtained as a difference parameter M.

According to another preferred embodiment, when the vehicle turns, instead of the road surface frictional force F, a cornering force F acting on the wheels in a direction perpendicular to the traveling direction of the vehicle is used.
_{Using S} , a difference parameter M is obtained based on road surface friction force information corresponding to the cornering force F _S and brake torque information corresponding to the brake torque T.

According to another preferred embodiment, a steering angle sensor for detecting a steering angle of a wheel is provided, and a direction orthogonal to a rotation axis of the wheel and a traveling direction of the vehicle are determined based on a detection signal from the steering angle sensor. A side slip angle β which is a deviation from the direction is obtained, and a cornering force F is calculated based on the side slip angle β.
_It was configured to find _S.

As described above, according to the present invention, the control is executed using the difference parameter M obtained based on the road surface frictional force F and the brake torque T, and the wheel acceleration parameter dMω / dt obtained based on the difference parameter M. Therefore, as compared with the conventional control using a gear that rotates together with the wheels, accurate control can always be performed irrespective of the vehicle speed. In addition, since the difference parameter M and the wheel acceleration parameter dMω / dt are parameters from which the crosstalk component of the brake torque T included in the road surface friction force F has been removed, the control accuracy is improved.

Further, by correcting and integrating the difference parameter M calculated by the difference parameter calculation means, the wheel speed parameter Mω becomes 0 when the wheel is locked.
Is calculated, and the wheel acceleration parameter dMω is calculated based on the
/ Dt, it is possible to obtain a wheel acceleration parameter dMω / dt which is very similar to the actual behavior of the wheel acceleration, and it is possible to respond quickly and accurately to changes in the road surface condition, thus further improving the control accuracy. Can be done.

The wheel acceleration parameter dMω / dt
Is used, the amount of change of M is extremely small, especially when traveling on an extremely low μ road, and the first threshold value for judging the end of pressure reduction becomes extremely shallow, especially when traveling on an extremely low μ road. In addition, the problem that the control becomes impossible due to the response delay of the hydraulic system can be satisfactorily solved, and a remarkable effect can be obtained particularly on an extremely low μ road surface. Furthermore, the wheel acceleration parameter dMω / d is compared with the case where the pressure reduction end is determined using the wheel speed parameter Mω.
Since t does not have an initial value like the wheel speed parameter Mω, and can be controlled by monitoring the fluctuation near the 0 level, high-precision control can be performed easily and quickly.

Other features and advantages of the present invention will become more apparent from the detailed description given below with reference to the accompanying drawings.

[0037]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be specifically described below with reference to the drawings.

FIG. 1 is an explanatory view of the arrangement of a sensor block provided in the ABS device according to the present invention. The sensor block 1 is mounted in a hole 3 formed in a vehicle axle 2. The hole 3 does not necessarily need to be formed in the vehicle axle 2 itself, but may be formed in the vicinity of the vehicle axle 2.

FIG. 2 is a perspective view showing the appearance of the sensor block 1. The sensor block 1 is made of four metal resistive foils on each surface of a cubic substrate 5 made of, for example, a metal or silicon-based material. The stress-strain gauge 6 is attached in a cross shape. The substrate 5 is not necessarily required to have a cubic shape. For example, even if stress-strain gauges 6 are provided in a cross shape on the front and back of a plate-like substrate, for example, three plate-like substrates are installed in the hole 3. Good.

FIG. 3 is a circuit block diagram of an ABS device according to the present invention. The ABS device has a CPU (central processing unit) 1 for controlling the entire ABS device.
1. RAM used as work memory of CPU 11
(Random access memory) 12, ROM (read only memory) 1 storing various programs and data, etc.
3, and an interface 14 for controlling signal transfer between the CPU 11 and input / output devices such as sensors and solenoid valves. The interface 14 has a function of converting an input analog signal into a digital signal, a function of converting an output digital signal into an analog signal, and the like. A road surface friction force sensor 15 that outputs a voltage proportional to a road surface friction force F acting on the vehicle; a brake torque sensor 16 that outputs a voltage proportional to a brake torque T that acts between the vehicle wheels and the brake device; A gravitational acceleration sensor 17 that outputs a voltage proportional to the gravitational acceleration G acting on the brake device and an electromagnetic valve 18 for controlling the hydraulic pressure of the brake device are connected. Road surface friction force sensor 15,
Brake torque sensor 16 and gravitational acceleration sensor 1
7 is realized by the stress-strain gauge 6 of the sensor block 1.

FIG. 4 is a virtual circuit block diagram realized by the operation of the CPU 11 based on the program stored in the ROM 13.
The calculating means 21, the Mω calculating means 22, the dMω / dt calculating means 23, the −a calculating means 24, the sudden pressurizing determining means 25, and the solenoid valve control means 26 are realized. These circuits are activated when the brake pedal of the vehicle is depressed.
This is realized by the CPU 11 executing the ABS control program stored in the ROM 13. Although not shown, the CPU 11 determines the depression of the brake pedal based on a detection signal from a sensor attached to the brake pedal itself or a sensor for monitoring the hydraulic pressure of the brake device.

The M calculating means 21 includes a road friction force sensor 15
A difference parameter M = FT is calculated based on the road surface frictional force F and the brake torque T input from the brake torque sensor 16 via the interface 14.

The Mω calculating means 22 calculates the difference parameter M and the gravitational acceleration G based on the difference parameter M from the M calculating means 21 and the gravitational acceleration G input from the gravitational acceleration sensor 17 via the interface 14. Difference M-
By integrating G, a wheel speed parameter Mω is calculated.

The dMω / dt calculation means 23 calculates the wheel acceleration parameter dMω / dt by differentiating the wheel speed parameter Mω from the Mω calculation means 22.

The -a calculation means 24 is provided by the road friction sensor 1
5 and interface 1 from gravity acceleration sensor 17
Road frictional force F and gravitational acceleration G input through
Is calculated based on the first threshold value. Specifically, the gravitational acceleration G is monitored at predetermined time intervals, and the gradient of the trajectory of the gravitational acceleration G is calculated based on the difference between the current gravitational acceleration G and the previous gravitational acceleration G. −
a is changed continuously or stepwise. Further, the -a calculating means 24 continuously or stepwise calculates -a according to the difference between the value of the road surface friction force F at the time of the start of the current pressure reduction and the value of the road surface friction force F at the time of the previous time of the pressure reduction start. Change. Note that the initial -a when the brake pedal is depressed is determined in advance in accordance with the negative peak value of the standard difference parameter M, and is stored in the ROM 13.

The rapid pressure determination means 25 calculates the wheel acceleration parameter dMω / dt from the dMω / dt calculation means 23,
Comparing with the third threshold value + A stored in the ROM 13, if the value of the wheel acceleration parameter dMω / dt reaches the third threshold value + A, it is determined that the vehicle is in an excessively reduced pressure state.
Outputs a rapid pressurization instruction signal. Wheel acceleration parameter dM
When the value of ω / dt becomes smaller than the third threshold value + A, the output of the rapid pressurizing instruction signal is stopped.

The solenoid valve control means 26 includes a difference parameter M from the M calculation means 21, a wheel acceleration parameter dMω / dt from the dMω / dt calculation means 23, and a-a calculation means 2.
The energizing state of the solenoid of the solenoid valve 18 is switched based on −a from 4 and the rapid pressurizing instruction signal from the rapid pressurizing judging means 25.

That is, the M calculating means 21 constitutes a difference parameter calculating means for calculating a difference parameter M corresponding to a difference between road surface frictional force information and brake torque information from the first sensor. The Mω calculating means 22 constitutes a wheel speed parameter calculating means for calculating a wheel speed parameter Mω which becomes 0 when the wheel is locked by correcting and integrating the difference parameter M calculated by the difference parameter calculating means. . The dMω / dt calculation means 23 is
A wheel acceleration parameter calculating means for calculating a wheel acceleration parameter dMω / dt by differentiating the wheel speed parameter Mω calculated by the wheel speed parameter calculating means is configured. The sudden pressurizing determination unit 25 and the solenoid valve control unit 26 constitute a brake hydraulic pressure control unit that controls the hydraulic pressure of the brake device using the wheel acceleration parameter dMω / dt calculated by the wheel acceleration parameter calculation unit. . The -a calculating means 24 constitutes a gravitational acceleration change rate calculating means for calculating the inclination of the locus of the gravitational acceleration G. Further, the -a calculating means 24 constitutes a first threshold varying means for changing the first threshold according to the inclination of the locus of the gravitational acceleration G. Further, the -a calculation means 24 constitutes a road friction force change amount calculation means for calculating a difference between the value of the road friction force F at the time of the start of the current pressure reduction and the value of the road friction force F at the time of the start of the previous pressure reduction. ing. Furthermore-
The a calculating means 24 constitutes a first threshold varying means for changing the first threshold value in accordance with the variation of the road friction force F calculated by the road friction force variation calculating means.

Next, the operation of the above ABS apparatus will be described. When the brake pedal is depressed, the solenoid valve control means 26
Monitors the difference parameter M from the M calculating means 21 and -a from the -a calculating means 24, and the difference parameter M is-
At the time point when the pressure decreases to a, the electromagnetic valve 18 is controlled to reduce the brake hydraulic pressure. Then, the solenoid valve control means 26 determines that dM
Wheel acceleration parameter dM from ω / dt calculation means 23
ω / dt is monitored, and when the wheel acceleration parameter dMω / dt reaches the second threshold value + a after the start of the depressurization of the brake oil pressure, the solenoid valve 18 is controlled to end the decrease of the brake oil pressure, for example, for 10 msec. Pressure increase and 40msec
The brake oil pressure is gradually increased by alternately repeating the hydraulic pressure holding.

Thereafter, the above-described control for decreasing and increasing the brake hydraulic pressure is repeated until the vehicle stops.

At this time, the -a calculating means 24 calculates the gravitational acceleration G from the gravitational acceleration sensor 17 in accordance with the inclination thereof.
-A is updated. That is, the gradient of the gravitational acceleration G is large on a road surface having a large road friction coefficient μ, and the gradient of the gravitational acceleration G is small on a road surface having a small road friction coefficient μ. By changing -a which is the threshold value of 1, the timing of the start of pressure reduction of the brake hydraulic pressure is changed.

Further, the -a calculating means 24 updates -a in accordance with the difference of the road surface frictional force F for each cycle of the pressure reduction control. Specifically, the road surface frictional force F at the time of the start of the current pressure reduction and the road surface frictional force F at the time of the previous time of the pressure reduction start
Is multiplied by a predetermined coefficient, and a value obtained by subtracting the product of the value and the previous value of -a from the previous value of -a is set as the current value of -a. In other words, a value obtained by multiplying the difference between the road surface friction force F at the start of the current depressurization and the road surface friction force F at the start of the previous decompression by a predetermined coefficient, and multiplying that value by the previous value of -a is , The difference between the previous value of -a and the current value of -a. That is, the value of -a is changed according to the change in the moment of inertia due to the change in the vehicle speed.

On the other hand, if the timing of the end of the depressurization is delayed, the sudden pressurization determining means 25 detects the delay of the end of the depressurization by utilizing the fact that the value of the wheel acceleration parameter dMω / dt becomes excessively large after the end of the decompression. Then, a rapid pressurizing instruction signal is output to the solenoid valve control means 26. Thus, the solenoid valve control means 26 controls the solenoid valve 18 to rapidly increase the brake oil pressure. When the value of the wheel acceleration parameter dMω / dt decreases to the third threshold value + A due to the increase in the brake oil pressure, the sudden pressurizing determination unit 25 stops outputting the sudden pressurization instruction signal. As a result, the solenoid valve control means 26 controls the solenoid valve 18 to return to a state in which the brake oil pressure is gradually increased.

The reason why excellent ABS control can be performed by the above operation will be theoretically considered below.

FIG. 5 is an explanatory diagram for explaining changes in various parameters when wheels are locked due to sudden braking applied to a running vehicle. As is clear from FIG. At the time of rising, a period during which a sufficient frictional force remains between the road surface and the wheels (0 to t)
_{In 1} ), the road surface frictional force F and the brake torque T increase almost linearly with the increase of the brake oil pressure P so as to follow the brake oil pressure P. Difference parameter M for this period
Is a substantially constant value.

However, when the frictional force acting on the wheels from the road surface approaches the limit point, although the brake torque T increases in accordance with the brake oil pressure P, the degree of increase of the road surface friction force F starts to decrease, and eventually the brake oil pressure increases. When P reaches a certain pressure corresponding to the limit value of the frictional force obtained from the road surface, the pressure rapidly decreases along a descending line. Further, the brake torque T starts to decrease rapidly as the wheel reaches locking, similarly to the road surface friction force F. Therefore, this period (t ₁
~t ₂₎ differential parameter M in, including the rapid drop with decreasing degree of increase in road surface friction force F, it reaches the lowest point at the peak of the brake torque T. After that, the brake torque T increases in inverse proportion to the decrease, and eventually becomes a constant value.

Generally, the brake torque T is equal to the road friction force F
The road surface frictional force F that is normally detected includes a considerable amount of the crosstalk component of the brake torque T. Therefore, it is very difficult to detect a pure road friction force. By the way, in the approximate equation of motion shown in the following equation 1, F _pure is a pure road friction force, t is a crosstalk component mixed in the road friction force F detected by the road friction force sensor 15, and this crosstalk component t is proportional to the brake torque T. Therefore, t / T can be defined as a constant. Therefore, by performing control using the difference parameter M = FT, it becomes possible to perform control excluding the crosstalk component due to the brake torque T, and the fluctuation of the difference parameter M approximates the behavior of the rotational angular acceleration dω / dt of the wheel. Can be determined to be possible. In Equation 1, I is the moment of inertia of the wheel, ω is the rotational angular velocity of the wheel, and K ₁ and K ₂ are proportional constants.

[0058]

(Equation 1)

Therefore, immediately after the start of braking, the difference parameter M is sequentially calculated by the M calculating means 21 based on the road surface frictional force F from the road surface frictional force sensor 15 and the brake torque T from the brake torque sensor 16. The result is sent to the solenoid valve control means 27. Solenoid valve control means 2
In step 7, the difference parameter M is monitored immediately after the start of the brake braking, and when the value of the difference parameter M decreases to the value of -a from the -a calculation means 24, it is determined that the wheel is heading for locking. Using the time point as the pressure reduction control start timing of the ABS control, the brake oil pressure P is reduced to avoid locking of the wheels. -A in FIG.
Corresponds to the first threshold value and means a limit boundary line of the braking force in the brake control.

Incidentally, the limit boundary line corresponds to the limit boundary of the road surface friction coefficient μ, and the road surface friction coefficient μ changes in real time with the change of the road surface condition and the vehicle speed. That is, it is necessary to change the limit boundary -a in real time. The change control of -a will be described later.

When the brake hydraulic pressure P is increased, the brake torque T increases due to the transmission delay of the brake system, and the road surface friction force F increases further due to the transmission delay. Generally, FIG.
From the peak value of the road surface frictional force F, the left side is referred to as a stable region and the right side is referred to as an unstable region. There is a so-called overslip phenomenon, in which the wheel starts to decrease rapidly, at which point the wheel hydraulic locking is prevented by reducing the brake hydraulic pressure P.

On the other hand, during the increase or holding of the brake oil pressure P, the difference parameter M shifts largely in the negative region direction. Here, when reaching the unstable region, -a is given to the difference parameter M as a decompression threshold reference line serving as a boundary,
When -a is compared with the difference parameter M, a brake oil pressure decrease signal A is obtained as shown in FIG. 6, and the time (t ₄ ) at which the brake oil pressure decrease signal A is obtained is determined as the pressure reduction control start timing. This -a is to prevent unnecessary pressure reduction of the brake oil pressure P in the wheel stability region.
Difference parameter M based on existing maximum road friction coefficient μ
It must be slightly larger in the negative direction.

As described above, the difference parameter M can be approximated to the behavior of the rotational angular acceleration dω / dt of the wheel by the above equation (1). Therefore, from the following equation 2, the integral value Mω the differential parameter M can be judged to be approximately expressed in the behavior of the wheel speed V _W. In the following equation 2,
R is the wheel effective radius. Also shows the relationship between the integrated value Mω and the wheel speed V _W of the differential parameter M the following equation 3. In Equation 3 below, k and C are constants. Also,
Shows the behavior of the integrated value Mω approximate to the wheel speed V _W by the brake control in FIG.

[0064]

(Equation 2)

[0065]

(Equation 3)

[0066] As shown in FIG. 7, the differential parameter M acquired in basically the actual control, when the wheel locking to the wheel speed V _W is attributed to the value of 0 is always present in the negative region to order, the integral value Mω wheel speed V _W
However, there still remains a problem that correction must be made so as to approximate. Further, the relative deceleration of the vehicle during this period becomes an inertial force when the force acting on the wheels changes from the force based on the coefficient of static friction to the force based on the coefficient of dynamic friction, so that the deceleration is constant.

Then, as shown in FIG. 8, the wheel speed parameter Mω is calculated by integrating MG using the gravitational acceleration G from the gravitational acceleration sensor 17. In this way, by correcting the difference parameter M by using the gravitational acceleration G as the zero drift line and then integrating the difference parameter M, a wheel speed parameter Mω having a behavior equivalent to the wheel speed V _W in actual control is obtained.

There is a period in which the difference parameter M is located more positively than the zero drift line from immediately after the start of the brake control until the wheel is locked. The amount of change in the rotational angular acceleration of the wheels during this period is very small, and it can be determined that the period is a period that can be ignored in actual ABS control, that is, a stable region. Therefore, a period from immediately after the start of the brake control until the difference parameter M reaches the zero drift line can be a factor for determining that it is not necessary to perform the ABS control.

The wheel acceleration parameter dMω / dt is obtained by differentiating the wheel speed parameter Mω. In order to use the wheel acceleration parameter dMω / dt for judging the end of the pressure reduction control, as shown in FIG. + A is used. That is, after the brake control start, the wheel acceleration parameters dMω / dt is the time t ₅ that reaches the second threshold value + a, the wheel speed is determined as a pressure reducing control end timing is sufficiently recovered to a stable region.

In this way, even when the amount of change in the difference parameter M is extremely small, such as when traveling on an extremely low μ road, the amount of change in the wheel acceleration parameter dMω / dt is sufficiently large. The pressure reduction control end determination can be made well. Moreover, since the wheel acceleration parameter dMω / dt does not have an initial value unlike the wheel speed parameter Mω, control can be performed near the 0 level.

If the pressure reduction control is excessively performed during the pressure reduction control period despite the sufficient recovery of the wheel speed, the wheel speed tends to approach the relative vehicle speed, causing a loss in the slip ratio. . In this period, the wheel acceleration parameter dMω / dt also exceeds the second threshold value + a and reaches the third threshold value + A as shown in FIG. Normally, after the pressure reduction control is completed, gentle pressurization is performed by the pulse step control control. However, when excessive pressure reduction control occurs, the loss of the slip ratio is not eliminated, and as a result, the braking distance is lost. . Therefore, the third threshold larger than the second threshold + a
And a wheel acceleration parameter dMω / d
t moves quick acceleration and pressure to control from your gentle pressurization up to now at the time t ₆ beyond the third threshold + A. This aims to rapid recovery of lost slip ratio, determines that the wheel acceleration parameter dMω / dt is eliminated loss of slip ratio at the time t ₇ which has returned to the third threshold value + A again, normal moderate Return to proper pressurization control.

Generally, the road surface friction force F and the road surface friction coefficient μ are
It changes according to the type of the road surface under control, for example, a change from a dry asphalt road to a wet asphalt road, a change in vehicle body speed, and a magnitude of an inertia moment due to a gear position.
The conventional ABS control device employs a method in which main control parameters are replaced with a slip ratio and a wheel deceleration, and a set value thereof, that is, a value for detecting a wheel stability limit is changed. However, the gear-shaped wheel speed sensor used in the conventional ABS device has a problem in that the sensing becomes worse as the speed becomes lower, and the vehicle speed required for calculating the slip ratio is determined by the wheel speed. However, there is a problem that the reliability is lacking because of relying on the estimated value.

Therefore, as shown in FIG. 11, the value of the road surface frictional force F at the point α where the difference parameter M intersects −a and the point β which is the intersection in the previous control cycle is compared, and only the difference is calculated. -A or increase its inclination. That is, the bottom of the wheel stability limit is lowered. This is always monitored immediately after the start of the brake braking, and by continuously performing the control, -a is changed stepwise or continuously, thereby controlling the -a corresponding to the change in the inertia moment due to the change of the vehicle body speed. realizable.

Further, by changing -a stepwise or continuously according to the inclination of the locus of the gravitational acceleration G, -a control corresponding to a change in the road surface condition can be realized.

That is, real-time sensing can be performed without the disadvantages of the gear-shaped wheel speed sensor employed in the conventional ABS device, and control adapted to the magnitude of the moment of inertia depending on the road surface condition and the gear position of the vehicle is realized. .

FIG. 12 is a virtual circuit block diagram realized by the CPU 11 according to another embodiment of the present invention. In this embodiment, the Mω calculating means 31 is used.
Instead of calculating the wheel speed parameter Mω by integrating the difference MG between the difference parameter M and the gravitational acceleration G,
The wheel speed parameter Mω is calculated by integrating the difference from the value proportional to −a from the a calculating means 32. Further, instead of changing -a according to the inclination of the trajectory of the gravitational acceleration G, the -a calculating means 32 changes -a according to the difference between the wheel speed parameters Mω at predetermined time intervals. Other operations are the same as those of the circuit block shown in FIG. In this way, control can be performed without using the gravitational acceleration sensor 17.

That is, the Mω calculating means 31 calculates the difference parameter M and the first value corresponding to the peak value of the difference parameter M.
A wheel speed parameter calculating means for obtaining a wheel speed parameter Mω by integrating a difference between the wheel speed parameter Mω and a value proportional to the threshold value. The -a calculation means 32 constitutes a two-point difference calculation means for calculating a difference between the wheel speed parameters Mω at predetermined time intervals. Further, the -a calculating means 32 constitutes a first threshold varying means for changing the first threshold value according to the difference between the wheel speed parameters Mω calculated by the two-point difference calculating means.

Hereinafter, the reason why excellent ABS control can be performed by the above operation will be considered theoretically.

First, in calculating the wheel speed parameter Mω, as shown in FIG. 13, the fact that the difference parameter M reaches a constant value in the wheel locked state as in the case of deceleration is used to calculate the value of the difference parameter M during the wheel lock period. M
The correction is performed by using a zero drift line equivalent to 0, that is, a straight line having a value proportional to -a as a reference line.
Assume this zero drift line and reference line, i.e. by moving the origin to zero drift line, the wheel speed parameter Mω with the equivalent behavior and the wheel velocity V _W in the actual control is obtained.

There is a period in which the difference parameter M is more positive than the zero drift line in the period from immediately after the start of the brake control until the wheel locks. The change amount of the wheel acceleration during this period is very small, and it can be determined that it is a period that can be ignored in actual ABS control, that is, a stable region. Therefore, a period from immediately after the start of the brake control until the difference parameter M reaches the zero drift line can be a factor for determining that the ABS control is not necessary.

[0081] For change of the road surface conditions in brake control it can be estimated by the value derived from the two-point difference equations wheel speed parameters Mω be approximated the behavior of the wheel speed V _w. The variation of the wheel speed parameter Mω at a specified time and two-point difference which was determined in real time, corresponds to a change amount of the wheel speed V _w.

For example, when the condition of a road surface on which a vehicle under brake braking control passes changes from a wet asphalt road surface to a dry asphalt road surface, the friction coefficient existing on the road surface during traveling on a wet asphalt road surface in the first half. μ
Is low and −a must be relatively small. Naturally, the difference parameter M also becomes smaller, and the amount of change in the wheel speed parameter Mω corresponding to the integral value also becomes smaller. However, when the vehicle enters a dry asphalt road surface, the friction coefficient μ existing on the road surface increases, and −a can be increased, and as a result, the amount of change in the wheel speed parameter Mω increases. The change point of the wheel speed parameter Mω corresponds to a change point at which the road surface friction coefficient μ changes greatly due to the change of the road surface condition, and −a can be set according to each road surface condition.

In each of the above embodiments, the M calculating means 21 uses the value FT obtained by subtracting the brake torque T from the road surface friction force F as the difference parameter M based on the road surface friction force information and the brake torque information. Although it is configured so as to be obtained, it is not always necessary to do so. For example,
When the radius of the wheel is R and the distance between the center of rotation of the wheel and the brake caliper of the brake device is r, the radius R and the distance r are calculated based on the road surface frictional force information and the brake torque information.
The value (R / r) FT obtained by subtracting the brake torque T from the product (R / r) F of the ratio R / r of the road surface friction force F and the road surface frictional force F may be obtained as the difference parameter M. Radius R and distance r
Is predetermined in accordance with the vehicle on which the ABS device is mounted, so the value of the constant R / r is also known, and the constant R / r
r is stored in the ROM 13, for example.

That is, if the radius of the wheel is R and the distance between the center of rotation of the wheel and the brake caliper of the brake device is r, the tire torque is RF and the brake torque is rT. Is expressed as
It is clear that (R / r) FT can be used as the difference parameter M.

[0085]

(Equation 4)

In this way, the difference parameter M when the vehicle stops is set to 0, and control is facilitated. In addition, since the peak value of the difference parameter M during the operation of the brake device appears earlier in time, it quickly reaches the first threshold value -a, so that overslip is less likely to occur.

[0087] Furthermore, during turning of the vehicle, instead of the road surface frictional force F, used cornering force F _S acting on the wheel in a direction perpendicular to the traveling direction of the vehicle, road friction force information corresponding to the cornering force F _S The difference parameter M may be determined based on the brake torque information corresponding to the brake torque T. Of course, the brake control is executed separately for each wheel. That is, when the vehicle turns, the forces acting on the wheels on the inner wheel side and the outer wheel side are different, and the wheels on the inner wheel side tend to rock,
By executing the brake control using the cornering force F _S , it is considered that such a problem is solved and appropriate control can be performed.

By the way, when the cornering force F _S is derived using Fiala's theory regarding the cornering characteristics of the tire, it is known that the cornering force F _S can be approximately expressed by the product Kβ of the cornering power K and the side slip angle β. Also known as Here, the cornering power K is a constant determined by the tread shape and the material of the tire, and the side slip angle β is a deviation between a direction orthogonal to the rotation axis of the wheel and a traveling direction of the vehicle. Also,
Generally, the sideslip angle β is obtained based on the steering angle of the wheel. Therefore, by providing a steering angle sensor for detecting the steering angle of the wheel, the side slip angle β is obtained based on a detection signal from the steering angle sensor when the vehicle turns, and the cornering force is calculated based on the side slip angle β and the cornering power K. In search of F _S , this cornering force F _S
May be used as road surface frictional force information to calculate a difference parameter M, and brake control may be performed based on the difference parameter M.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of the arrangement of sensor blocks provided in an ABS device according to the present invention.

FIG. 2 is an external perspective view of a sensor block provided in the ABS device according to the present invention.

FIG. 3 is a circuit block diagram of an ABS device according to the present invention.

FIG. 4 is a CPU provided in the ABS device according to the present invention.
FIG. 3 is a virtual circuit block diagram realized by.

FIG. 5 is a signal waveform diagram of each part in the ABS device according to the present invention.

FIG. 6 is a signal waveform diagram of each part in the ABS device according to the present invention.

FIG. 7 is a signal waveform diagram of each part in the ABS device according to the present invention.

FIG. 8 is a signal waveform diagram of each part in the ABS device according to the present invention.

FIG. 9 is a signal waveform diagram of each part in the ABS device according to the present invention.

FIG. 10 is a signal waveform diagram of each part in the ABS device according to the present invention.

FIG. 11 is a signal waveform diagram of each part in the ABS device according to the present invention.

FIG. 12 is a virtual circuit block diagram realized by a CPU provided in an ABS device according to another embodiment.

FIG. 13 is a signal waveform diagram of each part of the ABS device according to another embodiment.

[Explanation of symbols]

 Reference Signs List 11 CPU 12 RAM 13 ROM 14 Interface 15 Road surface friction force sensor 16 Brake torque sensor 17 Gravitational acceleration sensor 18 Solenoid valve 21 M calculation means 22 Mω calculation means 23 dMω / dt calculation means 24 -a calculation means 25 Rapid pressure determination means 26 Solenoid valve control means 31 Mω calculation means 32-a calculation means

Claims (14)

[Claims] 1. A road surface friction force information corresponding to a road surface friction force F acting between a vehicle wheel and a traveling road surface, and a brake torque corresponding to a brake torque T acting between a vehicle wheel and a brake device. An ABS device having an arbitrary number of first sensors capable of obtaining information, wherein a difference parameter M is calculated in accordance with a difference between road surface frictional force information and brake torque information from the first sensor. Parameter calculating means, a wheel speed parameter calculating means for calculating a wheel speed parameter Mω which becomes 0 when the wheel is locked by correcting and integrating the difference parameter M calculated by the difference parameter calculating means; The wheel acceleration parameter dMω / dt is calculated by differentiating the wheel speed parameter Mω calculated by the speed parameter calculating means. A wheel acceleration parameter calculating unit; and a brake hydraulic pressure control unit that controls a hydraulic pressure of the brake device using the wheel acceleration parameter dMω / dt calculated by the wheel acceleration parameter calculating unit. ABS device. 2. An arbitrary number of second sensors capable of obtaining gravitational acceleration information corresponding to a gravitational acceleration G acting on the vehicle, wherein the wheel speed parameter calculating means includes a differential parameter M
And integrating a difference between the gravitational acceleration G based on the gravitational acceleration information to obtain a wheel speed parameter Mω.
The ABS device according to claim 1. 3. The wheel speed parameter calculating means obtains a wheel speed parameter Mω by integrating a difference between a difference parameter M and a value proportional to a first threshold value corresponding to a peak value of the difference parameter M. The ABS device according to claim 1. 4. An arbitrary number of second sensors capable of obtaining gravitational acceleration information according to the gravitational acceleration G acting on the vehicle, and gravity calculating a gradient of a trajectory of the gravitational acceleration G based on the gravitational acceleration information. 4. The apparatus according to claim 3, further comprising: an acceleration change rate calculation unit; and a first threshold value change unit that changes the first threshold value according to an inclination of a locus of the gravitational acceleration G calculated by the gravitational acceleration change rate calculation unit. 5. A described
BS equipment. 5. A two-point difference calculating means for calculating a difference between the wheel speed parameters Mω at predetermined time intervals, and the first threshold value is set in accordance with the difference between the wheel speed parameters Mω calculated by the two-point difference calculating means. First to change
The ABS device according to claim 3, further comprising: a threshold variable unit. 6. A road friction force change amount calculating means for calculating a difference between the value of the road friction force F at the time of the start of the current pressure reduction and the value of the road friction force F at the time of the start of the previous pressure reduction; 6. A first threshold changing unit that changes the first threshold according to a change amount of the road surface frictional force F calculated by the change amount calculating unit.
The ABS device according to any one of the above. 7. The ABS device according to claim 4, wherein said first threshold value changing means changes the first threshold value continuously. 8. The ABS device according to claim 4, wherein said first threshold value changing means changes the first threshold value in a stepwise manner. 9. The brake fluid pressure control means, after starting to reduce the brake fluid pressure, executes a wheel acceleration parameter dMω / d
The ABS device according to any one of claims 1 to 8, wherein the pressure reduction of the brake fluid pressure is terminated when t reaches the second threshold value. 10. The brake fluid pressure control means, after the pressure reduction of the brake fluid pressure is completed, a wheel acceleration parameter dMω /
The ABS device according to any one of claims 1 to 9, wherein the brake fluid pressure is rapidly increased when dt reaches a third threshold value. 11. The differential parameter calculating means calculates a difference FT obtained by subtracting a brake torque T from a road frictional force F based on the road frictional force information and the brake torque information from the first sensor. The ABS device according to any one of claims 1 to 10, which is obtained as M. 12. The road surface friction from the first sensor, wherein the difference parameter calculating means sets a radius of the wheel as R and a distance between a rotation center of the wheel and a brake caliper of the brake device as r. A ratio R / r of the radius R and the distance r based on force information and brake torque information.
11. A value (R / r) FT obtained by subtracting the brake torque T from a product (R / r) F of the road friction force F and the road friction force F is obtained as a difference parameter M. ABS device. At 13. The vehicle turning, instead of road surface frictional force F, used cornering force F _S acting on the wheel in a direction perpendicular to the traveling direction of the vehicle, road friction force information corresponding to the cornering force F _S And brake torque T
The ABS device according to any one of claims 1 to 12, wherein a difference parameter M is determined based on brake torque information according to the following. 14. A steering angle sensor for detecting a steering angle of a wheel, and a side slip angle which is a deviation between a direction orthogonal to a rotation axis of the wheel and a traveling direction of the vehicle based on a detection signal from the steering angle sensor. 14. The ABS device according to claim 13, wherein β is determined, and the cornering force F _S is determined based on the side slip angle β.