JPH05286377A - Wheel speed detector - Google Patents

Abstract

PURPOSE:To reduce cost by providing an averaging means to detect a weighted mean value as a typical wheel speed in such a manner that the weighting of a detected value on the wheel side read by a high-precision reading means is made smaller than the weighting of a detected value on the wheel side read by a low-precision reading means during high speed run. CONSTITUTION:On a driven wheel side, right and left wheel speeds are found from a memorized time in accordance with pulsing cycles and an averaged value by an averaging means 10 is detected as a wheel speed. Specially, the weighting of a detected value on the wheel side read by high-precision reading means 10a-10c is made smaller than the weighting of a detected value on the wheel side read by a low-precision reading means 10a during high speed run to detect a weighted mean value as a wheel speed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to a vehicle or the like which switches between two-wheel drive and four-wheel drive in accordance with a slip occurrence state of wheels, and drive wheels to which engine driving force is constantly transmitted.
The present invention relates to a device for detecting a wheel speed with a non-driving wheel whose driving force is separated when driving two wheels.

[0002]

2. Description of the Related Art Conventionally, in a vehicle, for example, a clutch mechanism is provided at a rear stage of a transmission, and the clutch is disengaged or connected according to vehicle traveling conditions such as a difference in wheel speed between front and rear wheels and vehicle speed. There is one that enables switching between four-wheel drive and four-wheel drive (see Japanese Patent Application No. 1-146462).
..

Here, when a pulse generated from a wheel speed sensor provided for four wheels at predetermined rotation angles is input to the CPU offset by the control device for performing such two-wheel drive / four-wheel drive switching control. At the same time, there has been a need for a highly functional device having a period measuring device (referred to as an input catcher) that reads and stores the input time of the pulse at least 4 channels according to at least the number of wheels.

[0004]

However, a general-purpose CPU having such a high function is expensive and has many unnecessary functions, which is not practical. The present invention has been made in view of such conventional problems, and at least one channel is subjected to cycle measurement using software processing, and a wheel speed capable of sufficiently compensating for deterioration in accuracy due to the cycle measurement. An object is to provide a detection device.

[0005]

Therefore, as shown in FIG. 1, a wheel speed detecting device according to the present invention includes left and right drive wheels which are driven by constantly transmitting an engine drive force, and an engine at least during a predetermined operation. Wheel speed signal generating means for generating a pulse for each predetermined rotation angle of the wheel is provided on each of the left and right non-driving wheels which are separated from the driving force and are in a non-driving state, and the pulse generation cycle of each wheel speed signal is provided. In the wheel speed detection device for detecting the wheel speed of each wheel from the wheel speed detection device for detecting the representative wheel speed by processing the left and right wheel speed detection values for the driving wheel side and the non-driving wheel side, respectively. One of the left and right driving wheels is provided with a high-accuracy reading means for reading a pulse from the corresponding wheel speed signal generating means and at the same time reading and storing the input time. Due to the occurrence of It is equipped with a low-precision reading unit that stores the time read after the completion of software processing by interrupting, while averaging the wheel speeds of the left and right wheels for the drive wheels and using the high-precision reading unit at high vehicle speeds. The weighting of the detection value on the wheel side to be read is made smaller than the weighting of the detection value on the wheel side to be read by the low-precision reading means, and the averaging processing means for detecting the value subjected to the weighted average processing as the representative wheel speed is configured. ..

[0006]

From the wheel speed signal generation means provided for each wheel,
A pulse is generated for each predetermined rotation angle, and among them, for the left and right wheels on the non-driving wheel side and the left and right wheels on the driving wheel side,
At the same time as the pulse is input by the high-accuracy reading means, the input time is read and stored, and for the other wheel on the driving wheel side, the low-precision reading means interrupts the generation of the pulse and after the software processing is completed. The read time is stored.

On the drive wheel side, the wheel speeds of the left and right wheels are respectively obtained from the times stored as described above based on the pulse generation cycle, and the values averaged by the averaging means are the wheels. Detected as fast. In particular,
When the vehicle speed is high, the weighting of the wheel-side detection value read by the high-precision reading means is made smaller than the weighting of the wheel-side detection value read by the low-precision reading means, and the value obtained by weighted averaging is detected as the wheel speed. ..

[0008]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 2 showing an embodiment, the driving force of the engine 1 is divided into two via a transfer (not shown), one of which is transmitted to the front differential 2 to drive the left and right front wheels 3A and 3B, and the other of which is a propeller. It is transmitted to the rear differential 6 via an electromagnetic clutch 5 mounted on the shaft 4 and drives the left and right rear wheels 7A, 7B. In the vicinity of the front wheels 3A, 3B and the rear wheels 7A, 7B, wheel speed sensors 8a to 8d as wheel speed signal generating means for generating a pulse at each predetermined rotation angle of the wheel.
Is provided.

The control unit 9 for controlling the switching between the two-wheel drive and the four-wheel drive has a built-in CPU 10, and the two wheels are selected from a map of traveling conditions preset based on the detection signals from the wheel speed sensors 8a to 8d. Switching control between drive and four-wheel drive is performed. Here, the CPU 10 is provided with three channels of cycle measuring devices 10a to 10c as high-precision reading means for reading and storing the value of the free-run counter, that is, the pulse input time, in synchronization with the pulse input (rising). The three-channel period measuring devices 10a to 10c respectively include one of the left and right front wheels 3 that are driving wheels, for example, the left front wheel 3A, and the left and right rear wheels 7A that are non-driving wheels during normal traveling. The wheel speed signals from the wheel speed sensors 8a, 8c and 8d respectively provided in 7B are input.

A wheel speed signal from a wheel speed sensor 8b provided on the remaining right front wheel 3B is input to an interrupt port IRQ of the CPU 10. Then, the CPU 10 inputs the wheel speed signals of the respective wheels, detects the wheel speeds of the front wheels and the wheel speeds of the rear wheels as follows, and uses the detected values for the two-wheel drive / four-wheel drive switching control.

First, the period measuring device 1 for the three channels
The wheel speed sensor 8a of the left front wheel 3A and the wheel speed sensors 8c of the left and right rear wheels 7A and 7B, which are input to 0a to 10c,
When a pulse is generated at a predetermined rotation angle from 8d, the count value T of the free-run counter is read in synchronization with the rising edge of the pulse, and the latest count value T ₁ and the previous count value T ₀ are stored in the registers. (See Figure 3). These processes are quickly executed by hardware.

On the other hand, a wheel speed sensor 8b for the right front wheel 3B
Similarly, when a pulse is generated, the interrupt is generated in synchronization with the rising edge of the pulse. Then, when the interrupt is accepted, the process of reading the count value of the free-run counter is started, and the count value is read after a predetermined time. The latest read value T ₁ 'at this time and the last read value T ₀ ' are stored in the memory (see FIG. 4). still,
The function of reading the count value by the CPU 10 corresponds to the low-precision reading means.

Next, a wheel speed calculation detection routine by the CPU 10 will be described with reference to FIG. Step (S in the figure
Is written. The same applies to the following) 1, the wheel speed sensors 8a to 8d
The count value stored in each of the registers or the memory described above is read based on the wheel speed signal from the. In step 2, the wheel speed sensors 8a~8d each, a pulse generation cycle of subtracting the count value T ₁ or 'count value read last time from T ₀ or T _0' T ₁ read respectively latest wheel speed signal The wheel speed of each wheel is calculated as a value inversely proportional to the cycle.

In step 3, the front wheels 3A, which are the driving wheels,
In order to detect the wheel speed V _wf representative of 3B, first, the wheel speeds V _wfl, V of the left and right front wheels 3A, 3B obtained in step 2 are detected.
computing the average of the wheel speed V _WfAV of _wfr as _{(V wfl + V wfr) /} 2. In step 4, the left and right wheel speeds V _wfl,
The weights m, n (m + n = 1) of V _{wfl and} V _wfr for calculating a representative wheel speed V _wf by _performing a weighted average calculation of V _wfr are characteristics set in advance for the average wheel speed V _wfAV ( Figure 6
Search from the map (see). Here, the characteristics of the _weights m and n are m = n = 0.5 in a low / medium speed range in which the average wheel speed V _wfAV is less than a predetermined value, but in FIG.
As shown in, m is set to increase stepwise in accordance with the increase in vehicle speed. Instead of the average wheel speed V _{wf AV} , either the vehicle body speed V _FF or the left and right wheel speeds V _wfl, V _wfr , which will be described later, may be used.

In step 5, the representative wheel speed V _wf of the front wheels is calculated by the following equation based on the weights m and n. V _wf = mV _wfl + nV _wfr Here, since the average wheel speed V _wfAV is m = n = 0.5 in a low / medium speed range where the average wheel speed V _wfAV is less than a predetermined value, the representative wheel speed V _wf matches the average wheel speed V _wfAV . To do.

In step 6, the rear wheels 7 which are non-driving wheels are used.
In order to detect the wheel speed V _wr representing A and 7B, first, the vehicle body speed V _FF is obtained by selecting the smaller one of the left and right wheel speeds V _{wrl and} V _wrr . This is because the larger one is considered to be slipping. In step 7, the turning locus correction value ΔVH at the time of turning operation is obtained by the following equation based on the wheel speeds V _wrl, V _wrr and the vehicle speed V _FF .

[0017] _{ΔVH = {K1- (V FF)} 2 K2} · (V
_wrl− V _wrr ) / V _FF Here, K1 and K2 are constants determined from the specifications of the vehicle. In step 8, the representative wheel speed V _wf of the rear wheels is obtained as a value obtained by subtracting the turning locus correction value ΔVH from the vehicle body speed V _FF . During non-turning operation, V _wrl -V _wrr = 0 and the representative wheel speed V _wf matches the vehicle body speed V _FF .

[0018] obtained as described above, on the basis of the representative wheel speed V _wf of the front and rear wheels of the representative wheel speed V _wf, switching control of two-wheel drive -4-wheel driving is performed. Specifically, the slip state of the drive wheels is known from the difference between the representative wheel speed V _wf of the front wheels and the representative vehicle body speed V _wf of the rear wheels. _Therefore , when the slip is large, it is determined that the torque distribution to the drive wheels is too large. Then, control is performed to increase the torque transmission rate to the rear wheels 7A _and 7B which are non-driving wheels.

In detecting the wheel speed, the rear wheel side, which is a non-driving wheel, has a difference in magnitude or difference between the left and right wheel speeds of two wheels-4.
It has a great influence on the wheel drive switching control. Therefore, for detecting the wheel speed of the rear wheels, the cycle measuring devices 10b _, 10c capable of detecting the wheel speed in real time with high accuracy are used as in the conventional case. On the other hand, on the drive wheel side, even if there is a difference in the left and right wheel speeds, it is sufficient to average them to obtain the representative wheel speed. Therefore, the detection accuracy is not required as much as for the non-drive wheels, so the remaining cycle measuring device for one channel is used. 10a is used to detect the wheel speed of one wheel 7A, but the wheel speed of the other wheel 7B is detected by the software processing by the above-mentioned interrupt.

By the way, the detection error by the software processing is obtained by the following equation (see FIG. 4) detection error = (T ₁ '-T ₀ ')-(T ₁ -T ₀ ) = T _e1 -T _e2 Here, T _{e1 and} T _e2 are processing waiting times from the generation of the latest pulse and the generation of the previous pulse at the same time when the interrupt is generated to the acceptance of the interrupt. That is, the processing time is constant, but the processing waiting time differs depending on the processing state of the main routine at the time of the interruption, which causes a detection error.

The detection error is an error that occurs regardless of the pulse input cycle of the wheel speed signal. Therefore, the shorter the cycle, that is, the higher the vehicle speed, the greater the influence of the detection error. On the other hand, when there is no detection error or the detection error is small, the wheel speeds of the drive wheels should be obtained by averaging the left and right wheel speeds evenly.

Therefore, in consideration of the above points, when the vehicle speed is high at which the influence of the detection error increases, the weight of the wheel speed detected by the cycle measuring device with high accuracy is increased, and the influence of the detection error is small. By determining the wheel speeds as equal weights on the left and right at the vehicle speed, it is possible to secure detection accuracy as high as possible even when the wheel speeds are obtained by software processing.

[0023]

As described above, according to the present invention, the wheel speed of one wheel on the drive wheel side, which requires relatively small wheel speed detection accuracy, is determined by software processing, while the influence of the detection error is reduced. When the vehicle speed increases, the weight of the wheel speed on the side detected with high accuracy by the cycle measuring device is increased and the wheel speed of the driving wheels is determined by the weighted average. Even if a small number of inexpensive CPUs are used, the detection accuracy as high as possible can be secured, and the control performance based on the wheel speed detection can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing constituent functions of the present invention.

FIG. 2 is a diagram showing a configuration of an embodiment of the present invention.

FIG. 3 is a time chart showing a count value reading operation of the cycle measuring apparatus according to the embodiment.

FIG. 4 is a time chart showing a count value reading operation by software processing.

FIG. 5 is a flowchart showing a wheel speed detection routine.

FIG. 6 is a diagram showing a weight of a weighted average for similarly detecting a wheel speed on the drive wheel side.

[Explanation of symbols]

 1 engine 3A front wheel (left side) 3B front wheel (right side) 7A rear wheel (left side) 7B rear (right side) 8a-8d wheel speed sensor 10 CPU 10a-10a cycle measuring device

Claims (1)

[Claims] 1. A left and right driving wheel that is driven by constantly transmitting an engine driving force, and a left and right non-driving wheel that is in a non-driving state when the engine driving force is disconnected at least during a predetermined operation. A wheel speed signal generating means for generating a pulse for each predetermined rotation angle is provided, the wheel speed of each wheel is detected from the pulse generation cycle of each wheel speed signal, and the left and right wheels are respectively separated on the driving wheel side and the non-driving wheel side. In a wheel speed detecting device for processing a wheel speed detection value to detect a representative wheel speed, for each of the left and right non-driving wheels and one of the left and right driving wheels, a pulse is output from the corresponding wheel speed signal generating means. It is equipped with a high-precision reading unit that reads and stores the input time at the same time as inputting, and a low-precision reading that stores the time read after the software processing is completed by interrupting the other driving wheel due to the generation of a pulse. On the other hand, for the driving wheels, the wheel speeds of the left and right wheels are averaged, and when the vehicle speed is high, the weights of the detection values on the wheel side read by the high-accuracy reading means are read by the low-accuracy reading means. A wheel speed detecting device comprising: an averaging processing unit configured to detect a value obtained by performing weighted averaging processing by making the weight smaller than the weighting of the detection value on the side as a representative wheel speed.