JPS6311435A - Four wheel drive vehicle - Google Patents

Abstract

PURPOSE:To eliminate the delay of response in the control of center differential or in the shifting control between two-wheel and four-wheel driving by judging a road surface condition in a short time, with a simple formation of an average torque, an average vehicle speed and an average vehicle front and rear direction acceleration or a correction torque. CONSTITUTION:The output signals of a torque detecting part 2, a vehicle speed detecting part 3, and a vehicle front and rear direction acceleration detecting part 5 are inputted into a signal processing part 6, in which, first, an acceleration torque obtained from an average acceleration is subtracted from an average torque to calculate a correction torque. Then, based on this correction torque and an average vehicle speed, it is judged whether a presently traveling road surface condition is an asphalt road, a rugged road, or a sandy road by a road surface condition judging part 9, referring to a two-dimensional map in a memory means 7. And, in the case of the rugged load and sandy road, an output signal for locking a center differential is sent, whereas, in the case of an asphalt road, an output signal for releasing this locking is sent from a center differential control part 10 to an actuator 11.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a four-wheel drive vehicle that controls a front and 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 you have to use the steering wheel to apply force to the tires that are trying to return, front-wheel drive vehicles tend to be less prone to tipping over. In this respect, rear-wheel drive vehicles are easier to turn, but they have the disadvantage that if the driving force is too strong, the vehicle will turn too much. Therefore, it is ideal for driving a car to drive the front and rear wheels with half and half power.
In this respect, four-wheel drive vehicles are extremely superior.

By the way, the left and right wheels of a car have different turning radii when cornering, so in order to absorb this effect and perform smooth cornering, the difference in rotation speed between the left and right wheels is absorbed according to the difference in turning radius. mechanism, namely the differential mechanism (
It has a front differential and a rear differential. This difference in turning radius also occurs between the front wheels and rear wheels, so in four-wheel drive vehicles, there is a mechanism that absorbs the difference in rotation speed between the front and rear wheels according to the difference in turning radius, that is, a center differential mechanism. A system with the following has been proposed.

However, since this center differential mechanism has the function of distributing the torque between the front wheels and the rear wheels in an equal ratio, the driving force transmission limit is balanced to the value of the lower driving force of the front wheels or the rear wheels. becomes. For example, when 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 have inferior transmitted driving force when the road surface friction coefficient is low, compared to a four-wheel drive vehicle without a center differential. For example, when a large driving force is generated, such as during acceleration, the driving force cannot be sufficiently transmitted to the road surface, and this appears as phenomena such as front or rear wheels slipping (spin).

In order to prevent such negative effects, conventionally a locking mechanism has been installed to directly connect the power transmission between the front and rear wheels without going through a center differential, which eliminates the need for large driving force when accelerating or driving on rough roads. When driving, the center differential mechanism was manually locked, and during normal driving, which did not require a large amount of driving force, the center differential was manually unlocked.

FIG. 5 is a diagram for explaining the driving force transmission mechanism of a full-time four-wheel drive vehicle with a center differential in which the engine is mounted on the front side. In this driving force transmission mechanism, power from the engine is transmitted to a torque converter 31, a main transmission 32, and an auxiliary transmission 4a33 arranged in an automatic transmission 30, and the output is transmitted to a drive gear 34, and then to a drive tooth. 34 to the front wheel drive shaft 36 to drive the front wheels.

Here, the front differential device 35 is a differential mechanism between the right and left wheels 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. Furthermore, a center differential locking clutch 41 is arranged in parallel with the center differential device 39. Therefore, by controlling the engagement state of the clutch 41 by the hydraulic circuit 42, the locking of the center differential is controlled.

In general, four-wheel drive vehicles include part-time four-wheel drive vehicles in addition to the full-time four-wheel drive vehicles described above. This normally drives either the 11 wheels or the rear wheels, and when driving power is required, such as on snowy roads, the remaining wheels are directly connected to the drive shaft via a clutch, resulting in two-wheel drive and four-wheel drive. The switching between the two is performed intermittently.

By the way, the present applicant has filed a proposal in Japanese Patent Application No. 60-294752 to automatically prevent tight corner braking phenomena and slips. This analyzes the frequency of the signal from the torque sensor installed on the axle, selects the power spectrum peak value and the frequency corresponding to that peak value, and selects the power spectrum peak value, the frequency corresponding to that peak value, and The center differential is controlled according to the road surface condition by comparing the road surface condition with a map representing the road surface condition corresponding to the vehicle speed.

[Problem that the invention seeks to solve]

However, if you manually control the center differential or
When switching between four wheels, it is difficult for the driver to accurately predict the road conditions, so there is a problem in that the driver cannot immediately respond to the road surface conditions and cannot perform safe and stable control. In addition, as mentioned above, the signal from the torque sensor installed on the axle is frequency-analyzed, the power spectrum peak value and the frequency corresponding to that peak value are selected, and the power spectrum peak value and the peak value stored in advance are used. In an example in which the center differential is controlled according to the road surface condition by comparing a map representing the road surface condition corresponding to the corresponding frequency and RLT speed, the calculation processing time required for frequency analysis becomes long, and the control of the center differential becomes difficult. The problem is that there is a delay in response.

The present invention solves the above-mentioned problems by making it possible to judge the road surface condition in a short time with a simple configuration, and shortening the response delay in center differential control or 2-wheel to 4-wheel switching control. The purpose of this project is to provide a four-wheel drive vehicle that is capable of

[Failure to solve the problem]

Therefore, the four-wheel drive vehicle of the present invention is a four-wheel drive vehicle equipped with a front and rear wheel engagement mechanism that enables direct connection and release of power transmission between the front wheels and the rear wheels. a detection means having a detection section, a vehicle speed detection section, and a vehicle longitudinal acceleration detection section; a signal processing section that calculates an average value of each output signal of the detection means; and a signal processing section that calculates an average value of each output signal of the detection means, and A storage means for storing road surface conditions as a map, and a road surface condition determination section for determining the road surface condition by making the output signal of the signal processing section correspond to the map of the storage means, and according to the output signal of the road surface condition determination section. The present invention is characterized in that the front and rear wheel engagement mechanisms are controlled.

[Action 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 using a simple configuration based on the average torque, average vehicle speed, average vehicle longitudinal acceleration, or correction torque, and the center differential control or 2-4 wheel The response delay in switching control can be shortened, and a stable and safe running state that fully utilizes the driving force can be maintained.

〔Example〕

Examples will be described below with reference to the drawings.゛Figure 1 is a block configuration diagram for explaining an embodiment of the control system in a four-wheel drive vehicle of the present invention; Figure 2 is a diagram for explaining the processing flow of the embodiment of Figure 1; FIG. 3 is a block diagram for explaining another embodiment of the control system for a four-wheel drive vehicle according to the present invention, and FIG. 4 is a diagram for explaining the processing flow of the embodiment of FIG. 3.

In FIG. 1, the detection means 1 includes a torque detection section 2, a vehicle speed detection section 3, and a vehicle longitudinal direction acceleration detection section 5. The torque detection unit 2 was proposed separately by the applicant (Japanese Patent Application No. 1983).
0-298302 to Japanese Patent Application No. 60-298304), a torque sensor or a magnetostrictive torque sensor that detects the rotation angle between a predetermined span of the shirt I using two slit plates is used to detect the rotation angle between the front wheels or Installed on the rear wheel axle.

The signal processing unit 6 outputs respective output signals T of the torque detection unit 2, vehicle speed detection unit 3, and vehicle longitudinal direction acceleration detection unit 5,
■, α (for example, the average value of 100 samples per SMS) T, ■, α are calculated, and based on the following formula, the acceleration torque found from the average acceleration α is calculated as the average torque T
TC to calculate the corrected torque TC.

Tc=T--Wrα Note that W is the vehicle weight, r is the effective diameter of the tire, and K is the inertial part equivalent weight correction coefficient.

The storage means 7 stores various road surface conditions R corresponding to the corrected torque Tc and the average vehicle speed (2) measured in advance by driving the actual vehicle as a two-dimensional map. In this two-dimensional map, for example, R1 is an asphalt road, R2 is a bumpy road,
It is divided into three areas, with R3 being sandy.

The road surface condition determination unit 9 uses the correction torque Tc detected during driving.
and the average vehicle speed (2) are made to correspond to the two-dimensional map stored in the storage means 7, and it is determined whether the road surface condition on which the vehicle is currently traveling is an asphalt road, a bumpy road, or a sandy road.

The center differential control unit 10 sends an output signal to the actuator 11 to lock the center differential when the road surface condition on which the vehicle is currently traveling is uneven or sandy, and locks the center differential when the road surface condition is asphalt. This is to send an output signal to the actuator 11 to release the .

Next, the flow of processing of the above embodiment will be explained with reference to FIG.
The average values of 100 samples per SMS) T, ■, α are calculated, and then the correction torque Tc is calculated. The correction torque TC and the average vehicle speed V are made to correspond to the two-dimensional map stored in the storage means 7, and it is determined whether the road surface condition on which the vehicle is currently traveling is an asphalt road, a bumpy road, or a sandy road; If the road surface condition on which the vehicle is currently traveling is uneven or sandy, the center differential is locked, while if the road surface condition is asphalt, the center differential is unlocked.

3 and 4 show other embodiments of the present invention. In the above embodiment, the correction torque '' was calculated in the signal processing section 6, but in this embodiment, the correction torque The calculation of 〒C is not performed, and instead, various road surface conditions R corresponding to the average torque T, average vehicle speed V, and average acceleration α measured in advance by driving the actual vehicle are stored in the storage means 7 as a three-dimensional map. .This 3D map is
For example, the road is divided into three areas: R is an asphalt road, R2 is an uneven road, and R3 is a sandy road.

Then, average torque T, average vehicle speed ■, and average acceleration α
corresponds to the three-dimensional map stored in the storage means 7, and determines whether the road surface condition currently being traveled on is asphalt, a bumpy road, or a sandy road, and controls the center differential. .

Note that the present invention can be modified in various ways and is not limited to the above embodiments. For example, in the above example,
Although the present invention has been described as being applied to a full-time four-wheel drive vehicle with a center differential, it is of course applicable 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 wheels and the rear wheels is controlled.

Further, in each of the above embodiments, the map corresponding to the road surface condition stored in the storage means 7 is not corrected, but if the judgment in the road surface condition determination section 9 is wrong, the information at that time is stored in the storage means 7. 7 to correct the map.

As is clear from the above description, according to the present invention, it is possible to determine the road surface condition in a short time using a simple configuration from the average torque, average vehicle speed, average vehicle longitudinal acceleration, or correction torque, and to control the center differential or The response delay in wheel-to-four wheel switching control can be shortened, and a stable and safe running state that makes full use of the driving force can be maintained.

[Brief explanation 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 processing flow of the embodiment of FIG. 1, and FIG. The figure is a block diagram for explaining another embodiment of the control system in a four-wheel drive vehicle of the present invention, FIG. 4 is a diagram for explaining the processing flow of the embodiment of FIG. 3, and FIG. 1 is a diagram for explaining the driving force transmission mechanism of a full-time four-wheel drive vehicle with a center differential in which the engine is mounted on the front side. 1. Detection means; 2. Torque detection section. , 3...Vehicle speed detection unit, 5...Vehicle longitudinal direction acceleration detection unit, 6...
- Signal processing unit, 7... Storage means, 9... Road surface condition determination unit, 10... Center differential control unit, 11... Actuator. Applicant Aisin Warner Co., Ltd. (1 other person) Representative Patent Attorney Hiroki Shirai (2 others) Figure 2-2, 73-

Claims (4)

[Claims] (1) In a four-wheel drive vehicle equipped with a front and rear wheel engagement mechanism that enables direct connection and release of power transmission between the front wheels and the rear wheels, a torque detection section that detects torque acting on the axle, a vehicle speed detection section and a detection means having a vehicle longitudinal acceleration detection section; a signal processing section that calculates an average value of each output signal of the detection means; and a road surface state corresponding to the average torque, average vehicle speed, and average vehicle longitudinal acceleration stored as a map. storage means; and a road surface condition determination section that determines a road surface condition by making the output signal of the signal processing section correspond to a map of the storage means, and the front and rear wheel engagement mechanism is controlled by the output signal of the road surface condition determination section. A four-wheel drive vehicle characterized by control. (2) The storage means stores the corrected torque obtained by correcting the average torque by the average acceleration and the road surface condition corresponding to the average vehicle speed.
The four-wheel drive vehicle according to claim 1, characterized in that the four-wheel drive vehicle is a storage means for storing as a dimensional map. (3) The storage means is storage means for storing road surface conditions corresponding to average torque, average vehicle speed, and average vehicle longitudinal acceleration as a three-dimensional map. wheel drive car. (4) The four-wheel drive vehicle according to any one of claims 1 to 3, further comprising a center differential mechanism that can absorb the difference in rotational speed between the front wheels and the rear wheels.