JPH0790705B2 - 4-wheel drive vehicle with slip prevention control - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to four wheels with slip prevention control for detecting and comparing rotational accelerations of front and rear wheels to control the degree of engagement of front and rear wheel engaging means to prevent slip. Driven vehicles.

[Conventional technology]

Generally, when driving a car, front-wheel drive has better straight-line stability than rear-wheel drive, but when cornering,
Since the tires that are going to return have to apply force with the steering wheel, there is a tendency for the wheels to be difficult to bend when driving with front wheels. In that respect, the rear-wheel drive is more likely to bend, but if the driving force is too strong, it has the drawback of overturning. Therefore, it is ideal for driving a car to drive with front and rear wheels at half-power.
In that respect, the four-wheel drive vehicle is extremely excellent.

By the way, since the turning radii of the left and right wheels of the automobile are different during cornering, this effect is absorbed, and in order to perform smooth cornering, the difference in rotational speed between the left and right wheels is absorbed according to the difference in turning radius. A mechanism, that is, a differential mechanism (front differential, rear differential) is provided. Since this difference in turning radius also occurs between the front wheels and the rear wheels, in a four-wheel drive vehicle, a mechanism that absorbs the difference in rotation speed between the front wheels and the rear wheels according to the difference in turning radius, that is, a center differential mechanism. The one with is proposed.

However, since this center differential mechanism has a function of distributing the torques of the front wheels and the rear wheels in an equal ratio, the driving force transmission limit should be balanced with the lower value of the driving force of the front wheels or the rear wheels. Becomes For example, if one of the front wheels spins, drive energy escapes there,
The driving force of the rear wheels becomes extremely small. For this reason,
A four-wheel drive vehicle with a center differential may be inferior to a four-wheel drive vehicle without a center differential in transmission driving force when the road surface friction coefficient is low. This appears as a phenomenon such as the front wheels or the rear wheels slipping (idling), in which the driving force can be sufficiently transmitted to the road surface when a large driving force is generated, for example, during acceleration.

In order to prevent such an adverse effect, conventionally, a lock mechanism that directly connects the differential limitation between the front wheels and the rear wheels without using a center differential is provided, and a large driving force is required such as when accelerating or traveling on a rough road. In this case, the center differential mechanism was locked by means, and the lock was manually released during normal running that does not require a large driving force.

FIG. 4 is a diagram for explaining a driving force transmission mechanism of a full-time four-wheel drive vehicle with a center differential in which an engine is mounted on the front side. In this drive force transmission mechanism, the power from the engine is transmitted to the torque converter 41, the main transmission 42, and the auxiliary transmission 43 arranged in the automatic transmission 40, and the output thereof is the drive gear 44 and then the drive gear. It is transmitted to the front wheel drive shaft 46 via 44, and the front wheels are driven. Here, the front differential mechanism 45 is a differential mechanism between the right wheel and the left wheel of the front wheels. On the other hand, the rear wheel drive propeller shaft 47 is connected via a bevel gear 48 to a center differential mechanism 49 which is a differential mechanism between the front and rear wheels, and the center differential mechanism 49 is coupled to a rear wheel transmission device 50. Has been done. Further, the center differential lock clutch 51 is arranged in parallel with the center differential mechanism 49.
Are arranged. Therefore, the hydraulic circuit (pressure regulating solenoid)
By controlling the engagement state of the clutch 51 by 52, the locking of the center differential is controlled.

Generally, as a four-wheel drive vehicle, there is a part-time four-wheel drive vehicle in addition to the full-time four-wheel drive vehicle. This is because there is no center differential, normally either the front wheels or the rear wheels are driven, and when the driving force of the snow road etc. is required, the remaining wheels are directly connected to the drive shaft via a clutch etc. The drive and the four-wheel drive are intermittently switched.

By the way, conventionally, a technique for preventing slippage by four-wheel drive has been proposed in, for example, Japanese Patent Application Laid-Open No. 58-180325. This is applied to a part-time four-wheel drive vehicle to utilize the acceleration to prevent slip, and detects the rotational angular acceleration of the drive wheels during two-wheel drive to detect the vehicle speed and load (throttle opening). Is determined based on the determination reference value that takes into account the driving force when the change occurs, the automatic switching from two-wheel drive to four-wheel drive is performed. Specifically, the driving force is determined by both the vehicle speed and the load, and in response to each driving force having a different degree of slip occurrence, the slip reference is corrected to determine the occurrence of slip. is there.

[Problems to be solved by the invention]

However, the acceleration (driving force) varies with the same vehicle and load depending on the traveling state of the vehicle such as climbing and descending slope.
Further, the engine output of the vehicle at the same throttle opening also changes with time and season. Therefore, the above-mentioned conventional technique has a problem in that the reference value of the slip limit cannot be uniquely determined and accurate slip detection cannot be performed.

The present invention is to solve the above-mentioned problems, and is capable of slip detection with a simple configuration and with high accuracy, and it is possible to prevent slip by controlling the degree of engagement of front and rear wheel engagement mechanisms. An object is to provide a four-wheel drive vehicle with control.

[Means for solving problems]

Therefore, the four-wheel drive vehicle with slip prevention control of the present invention is
In a four-wheel drive vehicle having a front and rear wheel engagement mechanism in which a differential limitation between a front wheel and a rear wheel can be controlled from direct connection to release through a slip region by controlling an engagement degree,
Engagement means for driving the front and rear wheel engagement mechanism at the set engagement degree, acceleration detection means for detecting rotational acceleration of the front wheels and rear wheels, and comparing the rotational accelerations of the front and rear wheels to set the engagement degree. It is characterized in that a control means for controlling the combining means is provided.

[Operation and effect of the invention]

In the four-wheel drive vehicle with slip prevention control according to the present invention, by comparing the rotational accelerations of the front wheels and the rear wheels, the slip can be detected with high accuracy and the slip prevention control can be quickly performed. In other words, the rotational acceleration of the wheels is extremely different between when the slip occurs and when the vehicle body is accelerated without slipping.Therefore, a comparison result of the rotational acceleration of the front wheels and the rear wheels is obtained according to the degree of slip. Accordingly, the differential mechanism corresponding to the slip state can be restricted early.

〔Example〕

 Hereinafter, embodiments will be described with reference to the drawings.

FIG. 1 is a diagram for explaining one embodiment of a slip prevention control device for a four-wheel drive vehicle of the present invention, FIG. 2 is a block diagram showing a specific functional configuration example of the control device, and FIG. 3 is control It is a figure for explaining an example of solenoid oil pressure setting by a device.

In FIG. 1, 1 is a front wheel speed sensor, 2 and 5 are noise elimination circuits, 3 and 6 are waveform shaping circuits, 4 is a rear wheel speed sensor, 7 is a control device, 8 is a solenoid drive circuit, 9 is a solenoid, 10 Is an A / D conversion circuit, and 11 is a hydraulic pressure sensor. The control device 7 is, for example, a CPU with a built-in memory.
(Calculation processing device), reads signals from the front wheel speed sensor 1 and the rear wheel speed sensor 4, obtains the rotational acceleration ratio of the front and rear wheels, obtains the solenoid duty ratio from this acceleration ratio, and controls the solenoid drive circuit 8. To do. Noise elimination circuits 2, 5 and waveform shaping circuits 3, 6
Is a signal processing circuit that removes noise and waveform-shapes a rectangular wave so that the signals of the front wheel speed sensor 1 and the rear wheel speed sensor 4 can be processed by the control device 7. The oil pressure sensor 11 and the A / D conversion circuit 10 are feedback circuits for controlling the solenoid 9 to a predetermined oil pressure set by the control device 7.

Next, a specific configuration and processing of the control device will be described with reference to FIG.

In FIG. 2, 21 is a rectangular wave signal input section from the front wheel speed sensor, 22 and 25 are cycle measuring sections, 23 and 26 are averaging processing sections, 24 is a rectangular wave signal input section from the rear wheel speed sensor, 27 Is an acceleration ratio or difference calculation unit, 28 is an address conversion unit, 29 is a solenoid duty ratio reading unit, 30 is an oil pressure setting map storage unit, 31 is an oil pressure signal supply unit, 32 is a duty ratio determination unit, and 33 is a solenoid drive unit. Indicates.

First, when a rectangular wave signal is input from the front wheel speed sensor 1 and the rear wheel speed sensor 4 shown in FIG. 1 through the noise removal circuits 2, 5 and the waveform shaping circuits 3, 6, the cycle measurement units 22 and 25 perform cycle measurement. Then, in the averaging processing units 23 and 26, the change amount Δ of each cycle over n cycles is performed.
The averaging process is performed for S = (S _ti −S _ti−1 ) / t. That is, this average value is the average acceleration α _f , α for n cycles.
_r .

When the accelerations α _f and α _r for the front and rear wheels are calculated,
The acceleration ratio or difference calculation unit 27 calculates the ratio α _f / α _r or the difference α _f −α _r , and the address is converted from this to read the solenoid duty ratio from the hydraulic pressure setting map storage unit 30.

In the hydraulic pressure setting map, for example, as shown in FIG. 3, the hydraulic pressure is 0 when the acceleration ratio in which the front and rear wheels have the same acceleration is near 1,
The hydraulic pressure is set to gradually increase as the acceleration ratio increases and, conversely, decreases. That is, the hydraulic pressure is controlled so that the coupling between the front wheels and the rear wheels is strengthened as the acceleration ratio deviates from 1. The rate of change with respect to the acceleration ratio may be a straight line or another function curve. Further, when slipping, the acceleration ratio has a value that deviates from 1 to some extent, so a dead zone of a predetermined width ΔW may be set near the acceleration ratio of 1. The same applies when the map is set based on the difference in acceleration.

When the solenoid duty ratio is read from the map, the hydraulic signal is controlled according to the duty ratio (for example, 30%) to drive the solenoid.

Normally, when traveling on a low friction road, front and rear wheels rarely exceed the grip limit at the same time due to variations in load distribution and friction coefficient, and when slipping at the same time, slipping will be reduced even if the center differential is locked. Has no effect. Further, when a slip occurs, the tires and the drive mechanism are accelerated as compared with the case where the vehicle body is accelerated without slipping, so that the rotational acceleration of the wheels becomes extremely high. From this, as in the present invention, two of the vehicle speed sensor and the front and rear wheel speed sensors are used to compare the rate of change per unit time, and the degree of slip is judged to determine the hydraulic pressure within the range of 0% to 100%. Slip can be effectively prevented by operating the differential limiting mechanism of the center differential while changing it in multiple stages.

The present invention can be modified in various ways and is not limited to the above-mentioned embodiments. For example, the above embodiment has been described by applying the front and rear wheel engagement mechanism to a full-time type four-wheel drive vehicle with a center differential, but it is also applicable to a part-time type four-wheel drive vehicle. The front and rear wheel engagement mechanism in this case is a mechanism that can control the differential limitation between the front and rear wheels from direct connection to release through the slip area by controlling the degree of engagement. The latter is a center clutch that directly connects the front and rear wheels. Specifically, it is not limited to the hydraulic clutch, and any electromagnetic type or any other device that can control the degree of engagement may be used.

As is clear from the above description, according to the present invention, a throttle sensor or the like is not required, and slip can be accurately and easily detected only by a speed sensor. Also, since the degree of engagement of the front and rear wheel engagement mechanism can be adjusted from the initial stage of slip occurrence depending on the occurrence state, it is possible to give a smooth change in the degree of engagement, and suddenly engage and disengage the front and rear wheels in the slip occurrence state. It is possible to avoid the phenomenon of popping out due to the mechanism directly connecting the front and rear wheels. Therefore, the runnability and operability can be improved.

[Brief description of drawings]

FIG. 1 is a diagram for explaining one embodiment of a slip prevention control device for a four-wheel drive vehicle of the present invention, FIG. 2 is a block diagram showing a specific functional configuration example of the control device, and FIG. 3 is control FIG. 4 is a diagram for explaining an example of solenoid hydraulic pressure setting by the device, and FIG. 4 is a diagram for explaining a driving force transmission mechanism of a full-time four-wheel drive vehicle with a center differential in which an engine is mounted on the front side. 1 ... front wheel speed sensor, 2 and 5 ... noise elimination circuit, 3 and 6 ... waveform shaping circuit, 4 ... rear wheel speed sensor, 7 ... control device, 8 ... solenoid drive circuit, 9
…… Solenoid, 10 …… A / D conversion circuit, 11 …… Hydraulic sensor, 21 …… Square wave signal input from front wheel speed sensor, 22 and 25 …… Period measurement, 23 and 26 …… Averaging processing Section, 24 ... Rectangular wave signal input section from rear wheel speed sensor, 27 ... Acceleration ratio or difference calculation section, 28 ... Address conversion section, 29 ... Solenoid duty ratio reading section, 30 ...
… Hydraulic setting map storage, 31 …… Hydraulic signal supply, 32…
… Duty ratio determination unit, 33 …… Solenoid drive unit.

Front Page Continuation (72) Inventor Mitsuru Tatsuta 10 Takane, Fujii-cho, Anjo City, Aichi Prefecture, within Ishin Warner Co., Ltd. (56) Reference JP-A-55-72420 (JP, A) JP-A-61-295134 ( JP, A)

Claims (6)

[Claims] 1. A four-wheel drive vehicle having a front-rear wheel engaging mechanism, wherein a differential limitation between a front wheel and a rear wheel can be controlled from a direct connection to a release through a slip region by controlling an engagement degree. Engagement means for driving the front and rear wheel engagement mechanism at the engaged degree, acceleration detection means for detecting the rotational accelerations of the front and rear wheels, engagement by setting the degree of engagement by comparing the rotational accelerations of the front and rear wheels A four-wheel drive vehicle with an anti-slip control, comprising control means for controlling the means. 2. A slip prevention according to claim 1, which is a four-wheel drive vehicle having a center differential mechanism for absorbing a difference in turning radius of front and rear wheels in parallel with a front and rear wheel engaging mechanism. 4-wheel drive vehicle with control. 3. The slip prevention according to claim 1 or 2, wherein the control means is provided with reference data of an engagement degree corresponding to a comparison value of rotational accelerations of the front wheels and the rear wheels. 4-wheel drive vehicle with control. 4. The four-wheel drive vehicle with slip prevention control according to claim 3, wherein the comparison value is a ratio of rotational accelerations of the front wheels and the rear wheels. 5. The four-wheel drive vehicle with slip prevention control according to claim 3, wherein the comparison value is a difference in rotational acceleration between the front wheels and the rear wheels. 6. The four-wheel drive vehicle with slip prevention control according to any one of claims 1 to 3, wherein the degree of engagement is set by the drive duty ratio of the engagement means.