JPH0790706B2 - 4-wheel drive vehicle with slip prevention function - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a four-wheel drive vehicle having a slip prevention function of preventing slip by controlling the degree of engagement of front and rear wheel engagement mechanisms.

[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 a slip (idling) of the front wheels or the rear wheels when the driving force cannot be sufficiently transmitted to the road surface when a large driving force is generated such as 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 that case, the center differential mechanism was manually locked, and the lock was manually unlocked during normal running that does not require a large driving force.

FIG. 5 is a diagram for explaining a drive 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 21, the main transmission 22, and the auxiliary transmission 23 arranged in the automatic transmission 20, and the output thereof is the drive gear 24 and then the drive gear. It is transmitted to the front wheel drive shaft 26 via 24, and the front wheels are driven. Here, the front differential mechanism 25 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 27 is connected via a bevel gear 28 to a center differential mechanism 29, which is a differential mechanism between the front and rear wheels, and the center differential mechanism 29 is coupled to a rear wheel transmission device 30. Has been done. Further, a center differential lock clutch 31 is provided in parallel with the center differential mechanism 29.
Are arranged. Therefore, the hydraulic circuit (pressure regulating solenoid)
By controlling the engagement state of the clutch 31 by 32, the locking of the center differential is controlled.

In general, as a four-wheel drive vehicle, there is a part-time four-wheel drive vehicle without a center differential as opposed to a full-time four-wheel drive vehicle with a center differential as described above. Normally, either the front wheels or the rear wheels are driven, and when the driving force on the snowy road is required, the remaining wheels are directly connected to the drive shaft via a clutch or the like so as to drive the two-wheel drive and the four-wheel drive. And is switched intermittently.

As a conventional method for preventing slippage in a four-wheel drive vehicle, for example, in a part-time four-wheel drive vehicle, Japanese Patent Laid-Open No. 58-18 is available.
As proposed in Japanese Patent No. 0325, the number of rotations of the wheel is detected, and when abnormal rotation is shown, it is judged as slip and 2
There are those that switch from four-wheel drive to four-wheel drive, and some full-time four-wheel drive vehicles lock the center differential mechanism.

[Problems to be solved by the invention]

However, there are various problems in the conventional method of detecting the number of revolutions and determining the slip.

For example, in the above-mentioned conventional method, the driving force exceeds the road frictional resistance to cause slippage, and an abnormal change in the number of revolutions is detected only when the rotation is in an abnormal state. Since control is performed, control is delayed, and maneuverability deteriorates if the front and rear wheel engagement mechanisms are engaged after the abnormal state and the slip state continues or the driving force suddenly increases. . in this way,
After the rotation becomes abnormal, it takes time to return the rotation to normal. Moreover, the rotational speed also changes due to the tire air pressure and steering, so the limit of the change in the rotational speed that is judged to be abnormal must be set to a considerably high value, which causes a response delay.

The present invention solves the above problems and provides a four-wheel drive vehicle having a slip prevention function capable of eliminating a response delay and a delay in returning from an abnormal state to a normal state. To aim.

[Means for solving problems]

Therefore, in the four-wheel drive vehicle having the slip prevention function of the present invention, by controlling the degree of engagement, the differential limitation between the front wheels and the rear wheels can be controlled from direct connection to release through the slip region. In a four-wheel drive vehicle having an engagement mechanism, an engagement means for driving the front and rear wheel engagement mechanism at a set degree of engagement, an input side torque detection means for detecting an input side torque, and a road surface transmission torque for detecting a road surface transmission torque. A detection means and a control means for setting the degree of engagement and controlling the engagement means are provided, and the control means has reference data, obtains a slip torque from the input side torque and the road surface transmission torque, and sets the degree of engagement from the slip torque. It is characterized by doing.

[Operation and effect of the invention]

In the four-wheel drive vehicle having the slip prevention function of the present invention, the slip torque is obtained from the input side torque and the road surface transmission torque, so that the occurrence state of slip can be accurately and early detected. Therefore, by setting the degree of engagement from the slip torque and controlling the engagement means to drive the front and rear wheel engagement mechanism, the engagement means can be controlled before an abnormal change in the number of revolutions, and slip can be prevented in advance. It can be prevented.

〔Example〕

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

FIG. 1 is a diagram showing a configuration of an embodiment of a control system for a four-wheel drive vehicle having a slip prevention function according to the present invention, and FIG. 2 is a diagram for explaining an example of a processing flow by an electronic control unit. is there.

In FIG. 1, 1 is a throttle sensor, 2 is a vehicle speed sensor, 3 is a shift stage detection unit, 4 is a front wheel torque sensor, 5 is an A / D conversion circuit, 6 is a waveform shaping circuit, 7 is a counting circuit, and 8 is an electronic device. A control unit, 9 is a solenoid drive circuit, 10 is a pressure adjusting solenoid, 11 is an A / D conversion circuit, and 12 is a hydraulic sensor. The electronic control unit 8 is, for example, a computer control unit such as a CPU (arithmetic processing unit) having a built-in memory such as a RAM or a ROM for storing a control program, a map for obtaining an input torque and a map for obtaining a duty ratio of a solenoid, and a memory. The signals of various sensors are read while referring to the map stored in the table, the slip torque is calculated from the input torque and the road surface transmission torque, and the hydraulic pressure (duty ratio) of the hydraulic clutch is set (continuous or stepwise).
The solenoid drive circuit 9 to drive the pressure regulating solenoid 10
To control. In the case of a full-time four-wheel drive vehicle with a center differential, the pressure regulating solenoid 10 controls engagement of the center differential lock clutch, and thereby limits the differential mechanism. The gear shift stage detection unit 3 reads a control signal from the shift control device in the case of an automatic transmission, or an engagement hydraulic pressure signal used in a shift stage, and reads a shift lever position in the case of a manual transmission. is there.
The oil pressure sensor 12 and the A / D conversion circuit 11 are
Is a feedback circuit for controlling to a predetermined hydraulic pressure set by the electronic control unit 8.

The present invention is to detect the slip from the torque by the control system, determine the degree of engagement of the clutch which is the front and rear wheel engagement mechanism, and control the limitation of the differential mechanism. Therefore, first, the relationship between torque and slip will be described. The torque balance between the normal transmission (T / M) output torque, which is the input torque, and the road surface transmission torque can be expressed by T ₀ = T _r + T _Loss + Iφ.

Where T ₀ : T / M output torque T _r : Road surface transmission torque T _Loss : Transmission loss I: Drive system inertia moment φ: Drive system angular acceleration, road surface transmission torque T _r =
It becomes the vehicle running resistance (air resistance, rolling resistance, acceleration resistance). Further, the drive system angular acceleration φ is very slow because it coincides with the vehicle acceleration, and the term of Iφ becomes small. On the other hand, in the slip state, the road surface transmission torque T _r is determined by the road surface friction resistance μ (T _r = μ · W: W is the vehicle weight), and the excess torque of the T / M output torque T ₀ is all used in Iφ and slips. Happens.

From these things, in the present invention, the input side torque detecting means and the road surface transmission torque detecting means are used, and when the difference exceeds the reference value, it is judged that there is a possibility of slippage and the differential limiting mechanism is operated.

Next, the flow of processing by the electronic control unit will be described with reference to FIG.

First, each signal of the throttle opening, the vehicle speed, and the gear is input a predetermined number of times (4 times), and the respective signals are averaged (to).

Then, the address is determined by each of the above signals, and the value T ₀ of the output torque (input side torque) is read from the output torque map of the memory (,).

Subsequently, it detects the actual torque T _Front of the front wheel by the front wheel torque sensor as road-surface transmitting torque, the scheduled distribution torque T _0f = T _0/4 of the front wheels is calculated from the output torque values T _0, the front wheels of the scheduled distribution torque T calculating a slip torque T _x = T _0f -T _Front from actual torque T _Front of _0f and the front wheel (~).

When the slip torque T _x is obtained, the address is determined from this slip torque T _{x, the} solenoid duty ratio is read from the duty ratio map in the memory, and this value is used as the target value to compare with the current oil pressure by the oil pressure sensor to reach the target oil pressure. Drive the solenoid (~).

FIG. 3 is a diagram showing an example of an output torque map, and FIG. 4 is a diagram showing an example of a duty ratio map. As shown in FIG. 3, the output torque map sets the output torque corresponding to each value of the throttle opening, the shift speed, and the vehicle speed (engine speed). An output torque map corresponding to each value of (engine speed) may be provided for each shift speed, and the output torque map may be selected according to the shift speed. Further, the duty ratio map sets the duty ratio corresponding to the value of the slip torque as shown in FIG.

The present invention can be modified in various ways and is not limited to the above-mentioned embodiments. For example, although the front and rear wheel engagement mechanism is applied to the full-time type four-wheel drive vehicle with the center differential in the above-described embodiment, the invention can be similarly applied to a part-time type four-wheel drive vehicle. In this case, the front and rear wheel engagement mechanism is a mechanism that can control the differential limitation between the front wheel and the rear wheel from direct connection to release through the slip area. A center clutch that directly connects the 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.

Maps as reference data shown in FIGS. 3 and 4 are
You may prepare several according to the difference of driving conditions. The relationship between each value of the throttle opening, the shift speed, and the vehicle speed (engine speed) and the output torque changes depending on the season such as summer and winter, the difference in outside air temperature, the travel distance, the number of years of travel, and the like. Therefore, a plurality of output torque maps corresponding to these conditions may be stored in a memory, and the output torque map may be selected by switching a switch, a temperature sensor, or a signal of a traveling distance counter. Similarly, if the frictional resistance of the road surface changes, such as on snowy roads, rainy roads, jari roads, asphalt roads, etc., the value of slip torque also changes.
A plurality of duty ratio maps may be stored in the memory in correspondence with the frictional resistance of each of these road surfaces, and the duty ratio map may be selected according to the condition of the road surface.

As is apparent from the above description, according to the present invention, the torque balance between the input side torque and the road surface transmission force torque is checked, so that the accuracy of slip detection becomes high, and moreover, depending on the state at the initial stage of slip, Since the operation mechanism of the front and rear wheels is limited, the slip can be prevented in advance, and the unstable maneuverability due to the occurrence of the slip can be avoided.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of a control system for a four-wheel drive vehicle having a slip prevention function according to the present invention, and FIG. 2 is a diagram for explaining an example of a processing flow by an electronic control unit, FIG. 3 is a diagram showing an example of an output torque map, FIG. 4 is a diagram showing an example of a duty ratio map, and FIG. 5 is a full-time type with a center differential 4 with an engine mounted on the front side.
It is a figure for demonstrating the drive force transmission mechanism of a wheel drive vehicle. 1 ... Throttle sensor, 2 ... Vehicle speed sensor, 3 ...
… Gear shift detection unit, 4 …… Front wheel torque sensor, 5
...... A / D conversion circuit, 6 ...... waveform shaping circuit, 7 …… count circuit, 8 …… electronic control unit, 9 …… solenoid drive circuit, 10 …… pressure adjusting solenoid, 11 …… A / D conversion circuit , 1
2 ... Oil pressure sensor.

Front Page Continuation (72) Inventor Mitsuru Tatsuta 10 Takane, Fujii-cho, Anjo City, Aichi Prefecture, within Aisin Warner Co., Ltd. (56) Reference JP-A-61-249837 (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. Engaging means for driving the front and rear wheel engagement mechanism with the applied engagement degree, input side torque detecting means for detecting the input side torque, road surface transmission torque detecting means for detecting the road surface transmitting torque, and engaging means for setting the engagement degree. And a slip prevention function characterized in that the control means has reference data, the slip torque is obtained from the input side torque and the road surface transmission torque, and the engagement degree is set from the slip torque. 4-wheel drive vehicle. 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. A four-wheel drive vehicle with functions. 3. A four-wheel drive vehicle having a slip prevention function according to claim 1 or 2, wherein the control means has a plurality of reference data according to a running condition. 4. The reference data sets the input torque corresponding to the values of the throttle opening, the vehicle speed, and the respective signals of the shift speed obtained from the input torque detecting means. A four-wheel drive vehicle having the slip prevention function according to any one of items 1 to 3. 5. The slip prevention function according to any one of claims 1 to 4, wherein the reference data sets an engagement degree corresponding to a slip torque. 4-wheel drive vehicle. 6. A four-wheel drive vehicle having a slip prevention function according to any one of claims 1 to 5, wherein the degree of engagement is set by the drive duty ratio of the engagement means.