JP2003344435A - Wheel speed detection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress as small as possible the difference (gap) between a rotational speed calculated based on the frequency of a waveform signal and a rotational speed of an actual wheel at the point of time when detecting the edge of the waveform signal, not by calculating the rotational speed of the wheel at the point of time when detecting the edge of the waveform signal but by calculating the rotational speed of the wheel before reaching the point of time, when the rotational speed of the wheel becomes gradually low in a wheel speed device. <P>SOLUTION: When the present counter value N becomes larger than a signal frequency counter value Nn stored beforehand which is a counter value before reset in the case where the rotational speed of the wheel becomes gradually low (at the deceleration time of a vehicle), the CPU 21 of an electronic control device 20 calculates the rotational speed of the wheel based on the present counter value N at a fixed time (prescribed short time Δt) interval (step 128, 132). <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wheel speed detecting device for calculating a wheel rotation speed based on a signal period detected by a wheel speed sensor.

[0002]

2. Description of the Related Art As a wheel speed detecting device of this type, as shown in FIG. 1, each wheel Tf1, Tf2, Tr of a vehicle is shown.
1, wheel speed sensors S1, S2, S3, S4 for detecting waveform signals of frequencies corresponding to the rotational speeds of Tr2,
Each wheel Tf1, Tf2, Tr is connected to these wheel speed sensors S1, S2, S3, S4 and based on the cycle of the waveform signal input from each wheel speed sensor S1, S2, S3, S4.
A device including a control device 20 that calculates the rotational speeds of 1 and Tr2 is known.

The controller 20 calculates the rotational speed of the wheels as follows. The control device 20 uses the wheel speed sensors S1, S
Waveform signals are input from S2, S3, and S4 (see FIG. 4A), the input waveform signals are compared with the reference voltage V0, and a waveform signal smaller than the reference voltage V0 is changed to a waveform signal larger than the reference voltage V0. It is detected as "the rising edge of the waveform (edge of the waveform)" (t4, t5, t7). At the time of this detection, the period of the waveform signal is calculated by calculating the time difference between the previous “waveform rising” time point and the current “waveform rising” time point, and the wheel rotation speed is calculated based on this waveform signal cycle. Is calculated (see FIG. 4D).

[0004]

In the wheel speed detecting device described above, the wheel rotation speed is calculated only at the time when the "rise of the waveform" is detected. According to this, when there is almost no change in the rotation speed of the wheels, or when the rotation speed of the wheels gradually increases, the calculated rotation speed indicates the actual rotation speed. On the other hand, at the time of deceleration, the rotational speed of the wheels gradually decreases, so that the time difference between the “waveform rising” gradually increases, that is, the cycle of the waveform signal gradually increases. At this time, in the time zone that exceeds the previous cycle, that is, until the cycle becomes longer and the next "rise of the waveform" is detected, the rotational speed of the wheel calculated last time (latest) is held,
The gap (gap) from the actual rotation speed increases as the time elapses until the next “waveform rise”, and at the time when the edge of the waveform signal is detected,
Since there is a large gap between the rotation speed of the wheel calculated last time and the rotation speed of the wheel calculated this time, there is a problem that the wheel speed changes abruptly.

Therefore, the present invention has been made to solve the above-mentioned problems, and in a wheel speed detecting device,
When the rotational speed of the wheels gradually decreases, instead of calculating the rotational speed of the wheels at the time of detecting the edge of the waveform signal, by calculating the rotational speed of the wheels before reaching that time, An object is to suppress the difference (gap) between the rotation speed calculated based on the cycle of the waveform signal at the time when the edge of the waveform signal is detected and the actual rotation speed of the wheel as small as possible.

[0006]

In order to solve the above problems, a structural feature of the invention according to claim 1 is that a wheel speed sensor for sending a waveform signal having a frequency corresponding to the rotation speed of a wheel, and a waveform Whenever an edge of a signal is detected, it is reset and starts timing of the signal cycle, and when the edge of the waveform signal is detected, the time measured by the timing means is stored as a signal cycle. In the wheel speed detection device that calculates the rotation speed of the wheel based on the time, when the time measured by the time measuring means becomes longer than the previous signal cycle stored, the time measuring means measures the time without detecting an edge. That is, the rotation speed of the wheels is calculated at regular time intervals based on the time.

According to a second aspect of the invention, the wheel speed sensor for sending out a waveform signal having a frequency corresponding to the rotational speed of the wheel and the presence or absence of an edge of the waveform signal executed at regular time intervals are detected. Edge detection means, a counter that is added each time the edge detection means is executed, and is reset when an edge is detected, and a count value before the counter is reset when an edge is detected is stored as a signal cycle. ,
In a wheel speed detecting device having a calculating means for calculating the rotation speed of a wheel based on this signal cycle, when the current count value of the counter becomes larger than the count value before reset, calculation is performed without detecting an edge. By means of the means, the rotational speed of the wheel is calculated at regular time intervals based on the current count value of the counter.

According to a third aspect of the present invention, the calculating means comprises: a first calculating means for calculating the rotational speed of the wheel when an edge is detected; and a current count value of the counter before resetting. The second calculation means calculates the rotation speed of the wheels when the count value becomes larger than the count value of.

According to a fourth aspect of the present invention, in the wheel speed detecting device according to the above-mentioned invention, the rotational speed difference between the left and right wheels, the front wheel side rotational speed, and the rear wheel are controlled in the control of the driving force transmission device. It is used to detect the difference from the side rotation speed.

[0010]

In the invention according to claim 1 configured as described above, when the wheel rotates, the wheel speed sensor sends out a waveform signal having a frequency corresponding to the rotation speed of the wheel, and the timing means outputs the waveform signal. Each time the edge of is detected, it is reset and the timing of the signal period is started. The wheel speed detection device stores the time measured by the time measuring means as a signal cycle at the time when the edge of the waveform signal is detected, and calculates the wheel rotation speed based on this signal cycle.

However, when the rotation speed of the wheel is gradually reduced and the time during which the time is measured is longer than the previous signal cycle stored, the wheel speed detection device detects the edge. Even if it is not detected, the rotation speed of the wheel is calculated at regular time intervals by the time measuring means based on the time during the time measurement. According to this, it is possible to calculate the rotation speed of the wheel before the time of detecting the edge of the waveform signal is reached, and therefore, based on the cycle of the same waveform signal at the time of detecting the edge of the next waveform signal. The difference (gap) between the calculated rotation speed and the actual rotation speed of the wheels can be kept as small as possible.

In the invention according to claim 2 configured as described above, when the wheel rotates, the wheel speed sensor sends a waveform signal having a frequency corresponding to the rotation speed of the wheel, and the edge detecting means at constant time intervals. It is executed to detect the presence or absence of an edge of the waveform signal from the wheel speed sensor, the counter is added every time the edge detection means is executed, and the counter is reset when the edge is detected, and the calculation means is reset when the edge is detected. The count value before reset is stored and the wheel rotation speed is calculated based on this count value.

However, when the rotational speed of the wheels gradually decreases and the current count value of the counter becomes larger than the count value before the reset, the arithmetic means does not detect the edge for a certain period of time. The rotation speed of the wheel is calculated at intervals based on the current count value of the counter. According to this, it is possible to calculate the rotation speed of the wheel before the time of detecting the edge of the waveform signal is reached, and therefore, based on the cycle of the same waveform signal at the time of detecting the edge of the next waveform signal. The difference (gap) between the calculated rotation speed and the actual rotation speed of the wheels can be kept as small as possible.

In the invention according to claim 3 configured as described above, the calculating means is the first calculating means for calculating the rotational speed of the wheel when the edge is detected, and the current count value of the counter is reset. It comprises a second calculation means for calculating the rotation speed of the wheel when the count value becomes larger than the previous count value.
Therefore, the wheel speed can be reliably calculated regardless of whether the current count value of the counter is greater than the count value before resetting or when an edge is detected.

In the invention according to claim 4 configured as described above, the wheel speed detecting device according to the above-mentioned invention controls the difference between the rotational speeds of the left and right wheels in the control of the driving force transmission device.
It is used to detect the difference between the front wheel side rotation speed and the rear wheel side rotation speed. According to this, based on the accurate wheel rotation speed calculated by the wheel speed detection device, it is possible to accurately detect the rotation speed difference between the left and right wheels and the difference between the front wheel side rotation speed and the rear wheel side rotation speed. Therefore, the control of the driving force transmission device is accurately performed.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION A wheel speed detecting device according to the present invention will be described below with reference to the embodiment shown in FIG. As shown in FIG. 1, the wheel speed detecting device according to the present embodiment includes a front wheel T of an automobile M driven by an engine 10.
A differential control device 1 provided in a drive force transmission path that connects f1 and Tf2 to rear wheels Tr1 and Tr2 and that can change transmission torque.
5 and an electronic control unit (control unit) 20 that controls the transmission torque of the differential control unit 15. The driving force from the engine 10 is transmitted to a transfer 12 via a transaxle 11 having a transmission, and the driving force distributed to the front wheels is passed through a front differential (not shown) to the left and right front wheels Tf1, Tf.
The driving force transmitted to the rear wheel 2 and distributed to the rear wheel side is transmitted to the propeller shaft 13 provided with a differential control device 15 on the way.
Drive force transmission path and rear differential 1
It is transmitted to the left and right rear wheels Tr1 and Tr2 via 4 The differential control device 15 is an electromagnetic multi-plate friction clutch, and the transmission torque is changed according to the control output from the electronic control device 20. Left and right front wheels Tf1, Tf2 and rear wheel T
Wheel speed sensors S1, S2, S3, S4 for detecting respective rotation speeds are provided on r1 and Tr2. As the wheel speed sensors S1, S2, S3, S4, magnetic sensors, for example, magnetic sensors are used.

The electronic control unit 20 stores a CPU 21 for calculating a control value of the engaging force output to the differential control unit 15 according to the running state of the automobile M, and a control program necessary for this calculation / output. Existing ROM 22, RAM 23 used as a work area for this calculation, these CPU 21, ROM 22 and RAM 23, differential control device 15 and wheel speed sensors S1, S2, S3, S
An input / output circuit 24 is provided for inputting / outputting data to / from the digital camera 4.
The CPU 21 of the electronic control unit 20 controls each wheel speed sensor S
1, S2, S3, S4 detected by each wheel Tf1,
Although the edge of each waveform signal is detected based on the waveform signal of the frequency corresponding to the rotation speed of Tf2, Tr1, Tr2, when the time measured starting from the time when the previous edge is detected is shorter than the previously stored signal cycle, or In the case of the same, this measured time is stored as a signal cycle, the rotation speed of the wheels is calculated based on this signal cycle, and in the case of a long time,
The rotation speed of the wheel is calculated at constant time intervals based on the time during the timekeeping.

Next, according to the flow chart shown in FIG.
Regarding the calculation of the rotation speed of the wheels, a case where the vehicle is stopped, a case where the vehicle is accelerating, and a case where the vehicle is decelerating will be described.

The CPU 21 of the electronic control unit 20 sets the counter value N, the wheel speed, and the signal voltages V and V1 to "0" when an ignition key (not shown) is turned on.
2 and clear the program shown in FIG.
Repeat every t. The signal voltage V is read every time the program is executed.
And the signal voltage V1 is the signal voltage read in the program executed last time (the one before). The execution of this program is started in step 100, and the CPU 21 first adds "1" to the counter value N to substantially activate the counter, that is, starts counting up (step 102).

Then, the CPU 21 stores the signal voltage V of this time (or when the program is executed last time) as the signal voltage V1 of the last time (or when the program is executed two times before) (step 104), and each wheel speed sensor S1, S2. , S
3, voltage values output from S4 (left and right front and rear wheels Tf1,
A voltage at a predetermined time of a (waveform) signal corresponding to the rotation speeds of Tf2, Tr1, Tr2 is input (step 106), and the input voltage value is the latest (current) signal voltage V (from each wheel speed sensor). Voltage values Vf1, Vf2, Vr1, V
It is stored as a generic name of r2 (step 108).

Next, a case where the vehicle starts traveling and is in an accelerating state will be described. In this case, from the wheel speed sensors S1, S2, S3, S4, the left and right front and rear wheels Tf1,
Waveform signals corresponding to the rotation speeds of Tf2, Tr1, Tr2 are input. This waveform signal has a shorter signal period as time passes (see FIG. 3).

The CPU 21 detects the edge (rising edge) of this waveform signal. Specifically, the CPU 21
When it is determined that the previous signal voltage V1 is lower than the reference voltage V0 and the current signal voltage V is equal to or higher than the reference voltage V0 (in both Steps 110 and 112, “Yes”).
The edge of the waveform signal is detected by determining that the waveform signal has an edge). That is, as shown in FIG. 3, the CPU 21 controls the times t1 and t
At 2 and t3, the edge of the waveform signal is detected.

When the CPU 21 detects the edge of the waveform signal, the CPU 21 determines whether or not the vehicle is stopped at the time of the detection. Specifically, the CPU 21 determines in step 114 that the current counter value N is the reference counter value N1.
It is determined that the vehicle is stopped, and when it is exceeded, it is determined that the vehicle is stopped, and when not, it is determined that the vehicle is running. The reference counter value N1 is set to a very large value corresponding to the stop of the vehicle. Since the vehicle is in an accelerating state, the CPU 21 executes the program in step 1
The process proceeds to 16 to calculate the wheel speed (wheel rotation speed). That is, the signal cycle Ts (inter-edge time) obtained by multiplying the counter value (count value) N by a predetermined short time Δt is calculated by the following formula 1, and the wheel speed (= k × 1 / T) is calculated based on the signal cycle Ts.
s) is calculated. In addition, k is a constant determined from the number of teeth of the sensor rotor.

[0024]

## EQU1 ## Ts = N × Δt

In this embodiment, the signal period Ts (inter-edge time) is calculated by using the above-mentioned clocking means for counting up the counter value (count value) N.

Further, the CPU 21 calculates the wheel speed from the time when the edge of the waveform signal is detected this time to the time when the edge of the next waveform signal is detected, in step 11
The counter value N used in 6 is used as the signal cycle counter value Nn.
(Step 118). The signal period Ts calculated in step 116 may be stored instead of the signal period counter value Nn. Further, the CPU 21
In order to calculate the wheel speed when the edge of the next waveform signal is detected, the counter value N is reset to "0" in order to restart the counting of the counter value N after the time when the edge of the current waveform signal is detected. (Step 120). Then, the CPU 21 advances the program to step 122, and once ends this routine.

The CPU 21, except for detecting the edge of the waveform signal, that is, the current and previous signal voltages V,
If both V1 are equal to or higher than the reference voltage V0, or if the current signal voltage V is lower than the reference voltage V0, the program proceeds to step 128 (step 1).
10, 112). If the current counter value N does not exceed the signal cycle counter value Nn stored in step 118, the CPU 21 advances the program to step 138 (step 128). Note that instead of this processing, if the elapsed time from the edge detection time calculated from the current counter value N does not exceed the signal period Ts calculated in step 116, the program may be advanced to step 138. Good.

Then, the CPU 21 maintains the wheel speed calculated at the time when the edge of the waveform signal was previously detected in step 138 as it is. The wheel speed is used for controlling the drive type transmission device. After that, the CPU 21 advances the program to step 122, and once ends this routine.

The above control will be described in detail with reference to FIG. 3. At times t1 and t2, the CPU 21 resets the counter value N to "0" at time t1 and then counts the counter value N again. The counting up is started until the time t2 when the edge is detected next (the steps 100 to 112, 128, 138 and 122 are repeated). When an edge is detected at time t2, CP
U21 calculates the signal cycle Ts based on the counter value N, calculates the wheel speed based on the calculated signal cycle Ts, stores the counter value N as the signal cycle counter value Nn, and resets the counter value N to "0". (Steps 100 to 122). Then, after time t2, the CPU 21 starts counting up the counter value N again, and continues counting up until time t3 when the next edge is detected (steps 100 to 112, 128, 1).
38 and 122 are repeated). During this time, the CPU 21
Maintains the wheel speed calculated at time t2 as the wheel speed. After that, the CPU 21 repeatedly executes the above-mentioned processing.

Further, a case where the vehicle is in a decelerating state will be described. In this case as well, the CPU 21 executes the same processing as that of the vehicle in the acceleration state described above. From the wheel speed sensors S1, S2, S3, S4, the left and right front and rear wheels Tf
Waveform signals corresponding to the rotational speeds of 1, Tf2, Tr1, Tr2 are input. This waveform signal has a longer signal period as time passes (see FIG. 4).

The control in the decelerating state will be specifically described with reference to FIG. 4. At time t5, the CPU 21
The signal cycle Ts is calculated based on the counter value N measured from time t4 to t5, the wheel speed is calculated, the counter value N is stored as the signal cycle counter value Nn, and the counter value N is reset to "0". (Steps 100 to 12
Process 2).

Thereafter, at times t5 to t6, the CPU 2
1 starts counting up the counter value N again, and the current counter value N is the signal cycle counter value Nn previously stored.
Continue counting up until the time exceeds (Step 10
The processing of 0 to 112, 128, 138 and 122 is repeated). During this time, the CPU 21 maintains the wheel speed calculated at time t5 as the wheel speed.

Then, at time t6, when the CPU 21 detects that the current counter value N exceeds the previously stored signal cycle counter value Nn, the vehicle is stopped at the time of the detection as in step 114 described above. It is determined whether or not (step 130). Since the vehicle is in the decelerating state, the CPU 21 advances the program to step 132 to calculate the wheel speed. That is, the CPU 21 calculates the time Tn according to the counter value N in step 132 by the following mathematical expression 2, and based on the time Tn, the wheel speed (= k × 1 / T).
n) is calculated. In addition, k is a constant determined from the number of teeth of the sensor rotor.

[0034]

(2) Tn = N × Δt

After that, the CPU 21 continues the above-described calculation of the wheel speed until time t7 when the edge is detected next (steps 100 to 112, 128, 130, 132, 122).
Process is repeated). Therefore, from time t6 to t7, the wheel speed is calculated every predetermined short time Δt.

The case where the vehicle stops while the above-described processing is repeated will be described. Since the wavelength of the input waveform signal becomes very large and the counter value N exceeds the reference counter value N1, the CPU 21 During the above process, step 114 (or step 130)
Detects the stopped state of the vehicle in step 1 of the program
After 24 (or step 134), the wheel speed is set to "0" and the counter value N is set to the reference counter value N.
1 is substituted (steps 124 and 126, or steps 134 and 136).

As is apparent from the above description, in the present embodiment, when the rotational speed of the wheels is gradually reduced (when the vehicle is decelerating), the current counter value N is the counter value before reset. When it becomes larger than the previously stored signal cycle counter value Nn, the CPU 21 of the electronic control unit 20 detects the edge based on the current counter value N at regular time intervals (predetermined short time Δt). Calculate the wheel rotation speed. According to this, since the rotation speed of the wheel can be calculated before reaching the time point (for example, time t7) at which the edge of the waveform signal is detected, at the time point (time t7) when the edge of the next waveform signal is detected. hand,
The difference (gap) between the rotation speed calculated based on the cycle of the waveform signal and the actual rotation speed of the wheel can be suppressed as small as possible.

Further, based on the accurate wheel rotation speed calculated by the wheel speed detection device, the difference between the left and right wheel rotation speeds and the difference between the front wheel side rotation speed and the rear wheel side rotation speed can be accurately detected. Therefore, the control of the driving force transmission device is accurately performed.

Further, the CPU 21 of the electronic control unit 20 is
Calculating the wheel rotation speed when an edge is detected
1 calculation means (processing of steps 100 to 122) and second calculation means (steps 100 to 112) for calculating the wheel rotation speed when the current count value N of the counter becomes larger than the count value before reset. , 128 to 132, 122
Processing). Therefore, the wheel speed can be reliably calculated regardless of whether the current count value of the counter is greater than the count value before resetting or when an edge is detected.

In the above-mentioned embodiment, the counter is adopted as the time measuring means, but a timer may be adopted instead of the counter. In this case, the timer adds a predetermined short time Δt to the timer value T. Specifically, “Δt” may be added to the timer value T in step 102, and the timer value T may be stored as the signal period timer value Tn in step 118.
In step 120, the timer value T may be cleared to "0", and in step 128, the current timer value T and the signal period timer value Tn stored in step 118 may be compared. At 130, the current timer value T may be compared with the reference timer value T1 corresponding to the stopped state.

Further, in the above-described embodiment, only the rising edge in which the signal voltage value from the wheel speed sensor is less than the reference voltage V0 to the reference voltage V0 or more is detected, but the signal voltage value from the wheel speed sensor is detected. You may make it detect only the falling edge which becomes more than the reference voltage V0 and becomes less than the reference voltage V0. In this case, it may be determined in step 110 whether or not the current signal voltage V is lower than the reference voltage V0, and in step 112 whether or not the previous signal voltage V1 is equal to or higher than the reference voltage V0.

Further, in the above-described embodiment, the detection of the falling edge described above may also be performed together. In this case, the wheel speed can be detected every half cycle of the signal waveform. Specifically, it stores whether the previously detected edge is "rising" or "falling",
The following process may be performed instead of the processes of steps 110 and 112. That is, if the previous edge is "rising" and the signal voltage is less than the reference voltage V0, "falling" is detected and the program proceeds to step 114. If the signal voltage is not less than the reference voltage V0, the processing proceeds to step 128. . If the previous edge is “falling” and the signal voltage is equal to or higher than the reference voltage V0, “rising” is detected and the program is executed in step 114.
And if the signal voltage is less than the reference voltage V0, proceed to step 128. The counter value N, the signal cycle counter value Nn, and the reference counter value N1 are set to values corresponding to the case of a half cycle.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an overall configuration of an embodiment of a wheel speed detection device according to the present invention.

FIG. 2 is a diagram showing a flow chart of a control program of the embodiment shown in FIG.

FIG. 3 is a time chart showing the operation of the wheel speed detection device of FIG. (A) shows the input signal from the vehicle speed sensor, (b) shows the counter value,
(C) shows the wheel speed.

FIG. 4 is a time chart showing the operation of the wheel speed detection device of FIG. (A) shows the input signal from the vehicle speed sensor, (b) shows the counter value,
(C) shows the wheel speed, and (d) shows the wheel speed calculated by the conventional technique.

[Explanation of symbols]

10 ... Engine, 11 ... Transaxle, 12 ... Transfer, M ... Four-wheel drive vehicle, S1, S2, S3, S4 ...
Wheel speed sensor, Tf1, Tf2 ... Left and right front wheels, Tr1, T
r2 ... left and right rear wheels.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference)

Claims (4)

[Claims] 1. A wheel speed sensor which sends out a waveform signal having a frequency corresponding to the rotation speed of a wheel, and a timing means which is reset each time an edge of the waveform signal is detected and starts timing of a signal period, When the edge of the waveform signal is detected, the time measured by the time measuring means is stored as a signal cycle, and in the wheel speed detecting device for calculating the rotation speed of the wheel based on the signal cycle, the time measuring means measures the time. When the time becomes longer than the stored previous signal period, the wheel rotation speed is calculated at constant time intervals based on the time being measured by the time measuring means without detecting the edge. Wheel speed detection device characterized by. 2. A wheel speed sensor which sends out a waveform signal having a frequency corresponding to the rotational speed of a wheel, an edge detection means which is executed at regular time intervals and detects the presence or absence of an edge of the waveform signal, and the edge detection means. Is added every time is executed,
A counter that is reset when the edge is detected,
When the edge is detected, the count value before resetting of the counter is stored as a signal cycle, and in the wheel speed detecting device including a calculating means for calculating the rotation speed of the wheel based on the signal cycle, the current value of the counter When the count value of is larger than the count value before the reset, the rotation speed of the wheel is calculated by the calculating means based on the current count value of the counter at the constant time interval without detecting the edge. A wheel speed detecting device characterized by: 3. The first calculating means for calculating the rotation speed of the wheel when the edge is detected,
A second method for calculating a wheel rotation speed when a current count value of the counter becomes larger than the count value before the reset.
The wheel speed detecting device according to claim 1 or 2, comprising: 4. The wheel speed detecting device according to any one of claims 1 to 3, wherein in controlling the driving force transmission device, a difference in rotation speed between the left and right wheels, and a front wheel side rotation speed and a rear wheel side rotation speed. A wheel speed detecting device characterized by being used for detecting a difference between