JPH0790709B2 - 4-wheel drive vehicle - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a four-wheel drive vehicle that controls a front-rear wheel engagement mechanism that directly connects and releases a differential limiting device between front wheels and rear wheels.

[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 adverse effects, conventionally, a lock mechanism has been provided for directly connecting the power transmission between the front wheels and the rear wheels without passing through the center differential, which requires a large driving force for acceleration or traveling on rough roads. When doing so, the center differential mechanism was manually locked and 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 31, the main transmission 32, and the auxiliary transmission 33 arranged in the automatic transmission 30, and the output thereof is the drive gear 34 and then the drive gear. It is transmitted to the front wheel drive shaft 36 via 34, and the front wheels are driven. Here, the front differential device 35 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 37 is connected via a bevel gear 38 to a center differential device 39, which is a differential mechanism between the front and rear wheels, and the center differential device 39 is connected to a rear wheel transmission device 40. Has been done. Further, a center differential lock clutch 41 is arranged in parallel with the setter differential device 39. Therefore, the hydraulic circuit 42 allows the clutch
By controlling the connection state of 41, 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. Normally, either the front wheels or the rear wheels are driven, and when the driving force of a snowy road or the like is required, the remaining wheels are directly connected to the drive shaft through a clutch via a clutch to perform two-wheel drive and four-wheel drive. Is intermittently switched.

By the way, the applicant of the present application filed a proposal for automatically preventing the tight corner braking phenomenon and the slip.
Filed under No. 60-294752. This is the frequency spectrum analysis of the signal from the torque sensor provided on the axle to select the power spectrum peak value and the frequency corresponding to the peak value, the power spectrum peak value stored in advance, the frequency corresponding to the peak value, and The center differential is controlled according to the road surface condition by comparing with a map showing the road surface condition corresponding to the vehicle speed.

[Problems to be solved by the invention]

However, the center differential is manually controlled or the two wheels-
When the four wheels are switched, it is difficult for the driver to accurately predict the road condition, and thus it is impossible to immediately respond to the road condition and there is a problem that safe and stable control cannot be performed. Further, as described above, the signal from the torque sensor provided on the axle is subjected to frequency analysis, the power spectrum peak value and the frequency corresponding to the peak value are selected, and the power spectrum peak value and the peak value stored in advance are selected. In the example in which the center differential is controlled according to the road surface condition by comparing the map showing the road surface condition corresponding to the corresponding frequency and vehicle speed, the calculation processing time required for the frequency analysis becomes longer, and the center differential is controlled. It has a problem that a response delay occurs.

The present invention solves the above-mentioned problems, and makes it possible to determine the road surface condition in a short time with a simple structure, and shorten the response delay in the control of the center differential or the switching control of the two-wheel and four-wheel systems. It is an object of the present invention to provide a four-wheel drive vehicle capable of performing the above.

[Means for solving problems]

Therefore, in the four-wheel drive vehicle of the present invention, the torque acting on the axle is detected in the four-wheel drive vehicle provided with the front and rear wheel engagement mechanism that directly connects and disengages the power transmission between the front wheels and the rear wheels. Detecting means having a torque detecting section, a vehicle speed detecting section and a vehicle longitudinal acceleration detecting section, a signal processing section for calculating an average value of each output signal of the detecting means, and corresponding to an average torque, an average vehicle speed and an average vehicle longitudinal acceleration. And a road surface state determination unit that determines the road surface state by correlating the output signal of the signal processing unit with the map of the storage unit. The output signal of the road surface state determination unit The front and rear wheel engagement mechanism is controlled by the following.

[Operation and effect of the invention]

In the four-wheel drive vehicle of the present invention, the road surface condition can be determined in a short time from the average torque, the average vehicle speed, the average vehicle longitudinal acceleration, or the correction torque, and the center differential control or the two-wheel-four-wheel drive can be performed. The response delay in the switching control can be shortened, and the stable and safe traveling state can be maintained by fully utilizing the driving force.

〔Example〕

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

FIG. 1 is a block configuration diagram for explaining one embodiment of a control system in a four-wheel drive vehicle of the present invention, FIG. 2 is a diagram for explaining a processing flow of the embodiment of FIG. 1, and FIG. FIG. 4 is a block diagram for explaining another embodiment of the control system in the four-wheel drive vehicle of the present invention, and FIG. 4 is a view for explaining the processing flow of the embodiment of FIG.

In FIG. 1, the detection means 1 has a torque detection unit 2, a vehicle speed detection unit 3 and a vehicle longitudinal direction acceleration detection unit 5. The present applicant separately proposed the torque detection unit 2 (Japanese Patent Application No. 60
No. 298302 to Japanese Patent Application No. 60-298304), a torque sensor or a magnetostrictive torque sensor that detects the rotation angle between predetermined spans of a shaft using two slit plates is used for front wheels or rear wheels. It is installed on the axle.

The signal processing unit 6 outputs the output signals T of the torque detection unit 2, the vehicle speed detection unit 3, and the vehicle longitudinal direction acceleration detection unit 5, respectively.
The average value of V and α (for example, the average value of 100 samples every 5 ms) is calculated, and the correction torque _c is calculated by subtracting the acceleration torque obtained from the average acceleration from the average torque based on the following equation.

Note that W is the vehicle weight, r is the effective diameter of the tire, and K is the inertia part equivalent weight correction coefficient.

The storage means 7 stores various road surface states R corresponding to the correction torque _c and the average vehicle speed measured in advance by actual vehicle running.
Is stored as a two-dimensional map. In this 2D map, for example, R ₁ is asphalt road, R ₂ is uneven road, R ₃
Is divided into three areas such as sand.

The road surface condition determination unit 9 determines the correction torque _c detected during traveling.
Then, the average vehicle speed is made to correspond to the two-dimensional map stored in the storage means 7, and it is determined whether the currently running road surface state is an asphalt road, an uneven road, or a sandy road.

The center differential control unit 10 sends an output signal for locking the center differential to the actuator 11 when the road surface condition currently running is uneven or sandy, and when the road surface condition is asphalt road, locks the center differential. The output signal for releasing the signal is sent to the actuator 11.

Next, the flow of the processing of the above embodiment will be described with reference to FIG. 2. First, the axial torque T, the vehicle speed V and the acceleration α are read, and the average value of the respective output signals T, V and α (for example,
The average value of 100 samples every 5 ms) is calculated, and then the correction torque _c is calculated. Correction torque _c
The average vehicle speed and the average vehicle speed are made to correspond to the two-dimensional map stored in the storage means 7, and it is determined whether the currently running road surface condition is an asphalt road, an uneven road, or a sandy land, and the current road surface is running. When the condition is uneven road or sandy road, the center differential is locked, while when the road condition is asphalt road, the center differential is unlocked.

FIG. 3 and FIG. 4 show another embodiment of the present invention. In the above embodiment, the correction torque _c was calculated in the signal processing unit 6, but in the present embodiment, the correction torque _c Instead of performing the calculation, the storage means 7 stores various road surface states R corresponding to the average torque, the average vehicle speed, and the average acceleration previously measured by the actual vehicle running as a three-dimensional map. This three-dimensional map is divided into three regions, for example, R ₁ is an asphalt road, R ₂ is an uneven road, and R ₃ is a sandy road. Then, the average torque, the average vehicle speed, and the average acceleration are made to correspond to the three-dimensional map stored in the storage means 7, and it is determined whether the currently running road surface condition is an asphalt road, an uneven road, or a sandy surface. However, it controls the center differential.

The present invention can be modified in various ways and is not limited to the above embodiments. For example, in the above embodiment,
Although it has been described that the invention is applied to a full-time four-wheel drive vehicle with a center differential, it is needless to say that it can be applied to a part-time four-wheel drive vehicle. In this case, in the former case, the clutch of the differential limiting mechanism of the center differential is controlled, whereas in the latter case, the clutch that directly connects the front wheel and the rear wheel is controlled.

Further, in each of the above embodiments, the map corresponding to the road surface state stored in the storage means 7 is not corrected, but when the determination by the road surface state determination unit 9 is incorrect, the information at that time is stored in the storage means. Alternatively, the map may be corrected by inputting the information to No. 7.

As is apparent from the above description, according to the present invention, the road surface condition can be determined in a short time from the average torque, the average vehicle speed, the average vehicle longitudinal acceleration or the correction torque, and the center differential control or 2 It is possible to reduce the response delay in the wheel-to-four-wheel switching control, and to maintain a stable and safe traveling state by fully utilizing the driving force.

[Brief description of drawings]

FIG. 1 is a block configuration diagram for explaining one embodiment of a control system in a four-wheel drive vehicle of the present invention, FIG. 2 is a diagram for explaining the flow of processing of the embodiment of FIG. 1, and FIG. FIG. 4 is a block diagram for explaining another embodiment of the control system in the four-wheel drive vehicle of the present invention, FIG. 4 is a drawing for explaining the processing flow of the embodiment of FIG. 3, and FIG. FIG. 6 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. DESCRIPTION OF SYMBOLS 1 ... Detection means, 2 ... Torque detection section, 3 ... Vehicle speed detection section, 5 ... Vehicle longitudinal acceleration detection section, 6 ... Signal processing section, 7 ... Storage means, 9 ... Road surface condition determination section , 10 …… Center differential control section, 11 …… Actuator.

Claims (4)

[Claims] 1. A four-wheel drive vehicle having front and rear wheel engaging mechanisms for directly connecting and releasing power transmission between a front wheel and a rear wheel, a torque detecting section for detecting a torque acting on an axle, and a vehicle speed detection. Section and a vehicle front-back direction acceleration detection section, a signal processing section for calculating an average value of each output signal of the detection section, and a road surface state corresponding to an average torque, an average vehicle speed, and an average vehicle longitudinal direction acceleration as a map. The front and rear wheel engagement is provided with storage means for storing and a road surface condition judging portion for judging a road surface condition by correlating an output signal of the signal processing portion with a map of the storage means. A four-wheel drive vehicle characterized by controlling a mechanism. 2. The storage means is storage means for storing, as a two-dimensional map, a correction torque obtained by correcting the average torque by the average acceleration and a road surface state corresponding to the average vehicle speed. The four-wheel drive vehicle according to the item. 3. The storage means according to claim 1, wherein the storage means is a storage means for storing a road surface state corresponding to an average torque, an average vehicle speed and an average vehicle longitudinal acceleration as a three-dimensional map. 4 wheel drive vehicle. 4. A four-wheel drive vehicle according to claim 1, further comprising a center differential mechanism capable of absorbing a difference in rotational speed between the front wheels and the rear wheels. .