JPS62155134A - Controller for four wheel driving - Google Patents

Abstract

PURPOSE:To fully exhibit the function of a center differential gear at all times and utilize the engine drive force so as to achieve a safe and stable traveling condition, by deciding the pavement condition accurately through the detection of a torque functioning onto an axle, thereby controlling a center differential mechanism. CONSTITUTION:A torque T functioned onto a front or rear wheel is detected by a detecting means 1. A power spectrum analyzing section 2 will perform a frequency analysis on said torque signal and select the peak level of a power spectrum and a frequency corresponding to said peak level. In a pavement condition deciding section 4, a variable V representing the condition of a vehicle at an existing state is compared with a pavement condition decision map previously stored by a memory means 3 and a center differential gear is controlled in a control section 5 to be locked or released automatically. Consequently, the pavement condition can be decided accurately while the structure of the controller is simplified, and the driving force can be fully utilized, thereby a stable and safe traveling condition can be maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a four-wheel drive control device, and in particular, the present invention relates to a four-wheel drive control device, and in particular, to absorb the turning radius of the front and rear wheels that occurs during cornering. The present invention relates to a four-wheel drive control device for a four-wheel drive vehicle equipped with a center differential for allowing rotational speed differences.

(Prior art) -J%i, the front and rear wheels of a vehicle have different turning radii when cornering.In a four-wheel drive vehicle, in order to absorb this effect and perform smooth cornering, the turning radius has to be adjusted. A mechanism has been proposed that allows a difference in rotation speed between the front wheels and the rear wheels according to the difference, that is, a center differential mechanism.

However, since this center differential has the function of distributing torque between the front and rear wheels in an equal ratio, the driving force transmission limit will be balanced to the lower value of the driving force of the front or rear wheels. . Moreover, one of the four wheels
If any wheel spins, the driving force will not be transmitted to the other three wheels. 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, this driving force cannot be sufficiently transmitted to the road surface, resulting in phenomena such as front or rear wheels slipping.

In order to prevent such negative effects, a locking mechanism is installed that directly connects the power transmission between the front wheels and rear wheels without going through the center differential. The center differential mechanism is locked using a manual switch when the driver judges the road surface condition or when the driver judges the road surface condition.The technology to automatically judge the road surface condition includes:
An example of using an ultrasonic vehicle height sensor for suspension control was presented at the Society of Automotive Engineers of Japan.

In addition, focusing on the phenomenon that tires tend to slip when the load on them decreases, it has been proposed to detect the spring load on the suspension and automatically lock the center differential mechanism.

[Problem that the invention seeks to solve]

However, when manually locking the center differential mechanism, it is difficult for the driver to accurately predict the road conditions, so the driver cannot immediately judge the road surface conditions and cannot perform safe and stable control. In addition, when detecting the spring load on the suspension and automatically locking the center differential mechanism, there are problems in that the road surface condition cannot be accurately determined, making safe and stable control impossible, and the detection mechanism becomes large. There is a point.

Furthermore, technology that uses ultrasonic vehicle height sensors to control the suspension and automatically judges road conditions,
When ultrasonic waves are reflected on the road surface, the direct waves and reflected waves interfere, making it impossible to accurately and stably judge the road surface condition.Additionally, there are problems in that the control device becomes complicated, and in the case of suspension control. Since only the cushioning properties need to be taken into account, this technique can be used only with rough judgment and control, and there are many problems in applying this technology to the control of a center differential.

The present invention solves the above problems, and by detecting the torque acting on the axle, accurately judges the road surface condition and controls the center differential mechanism, so that the center differential function is always fully utilized. It is an object of the present invention to provide a four-wheel drive control device that enables safe and stable driving by effectively utilizing engine driving force.

[Means for solving problems]

To this end, the present invention focuses on detecting the torque acting on the axle and determining the road surface condition from the detected signal. Figure 3 (a) is a waveform diagram showing the relationship between torque and time. For example, when driving on sand, the torque is large and its amplitude is large, but when driving on an asphalt road, the torque is small and its amplitude is small, and when driving on an uneven road, the torque is large and its amplitude is also large. During driving, the magnitude and amplitude of torque are between the two. That is, if the road surface condition and the torque waveform can be distinguished and corresponded to each other, the road surface condition can be determined. Therefore, when the waveform in Fig. 3 (a) is subjected to frequency analysis (FFT) by a computer, the torque waveform is expressed by the relationship between frequency and power spectrum as shown in Fig. 3 (b), and the peak value of the power spectrum PS As a result of experiments, it has been found that the road surface condition can be distinguished by the frequency f corresponding to this PS and the variable V (vehicle speed, throttle opening, or average torque) representing the vehicle condition. That is, the road surface condition R is expressed as R=F (PS, f, V), and PS, f is obtained by accumulating the actual measurement results on various road surfaces.

We succeeded in creating maps of various road surface conditions a (for example, sand, uneven roads, asphalt, etc.) within the three-dimensional coordinates of (2).

Based on the above-mentioned results, the present invention provides a detection means for detecting the torque acting on the axle of the front or rear wheels, frequency analysis of the signal from the detection means, and a power spectrum peak value and a frequency corresponding to the power spectrum peak value. The analysis means to be selected, the detection means to detect variables representing the vehicle condition, and the
A storage means for storing a power spectrum peak value, a frequency corresponding to the power spectrum peak value, and a road surface condition corresponding to a variable representing a vehicle state as a road surface condition determination map, the analysis means, and a detection means for detecting a variable representing a vehicle state. road surface condition determination means for comparing and determining a signal from the road surface condition determination map stored in the storage means, and center differential control means for locking or unlocking a center differential based on the output signal of the road surface condition determination means. It is characterized by:

[Action and effect of the invention]

The four-wheel drive control device of the present invention stores in advance the beep value of the power spectrum obtained by frequency analysis of the torque signal, the frequency corresponding to its peak value, and the value of the variable representing the vehicle state. Compare with road surface condition judgment map,
Since the center differential is controlled to automatically lock or unlock the center differential based on the judgment, it is possible to accurately judge the road surface condition, and the configuration of the control device is simple, ensuring sufficient driving force. It is possible to maintain stable and safe driving conditions by taking full advantage of this.

〔Example〕

Examples will be described below with reference to the drawings.

Fig. 1 is a diagram showing the configuration of one embodiment of the control system in the control device of the present invention, Fig. 2 is a diagram for explaining the flow of processing by the control device of the present invention, and Fig. 3 is a torque waveform and power spectrum. Figure 4 is a diagram showing the power transmission system of a four-wheel drive vehicle with a center differential to which the control device of the present invention is applied. 4 is a storage means, 4 is a road surface condition determination unit, 5 is a center differential control unit, 6 is an actuator, A is a center differential mechanism, B is a front differential mechanism, 51 is a ring gear, 52
is the front differential case, 53 is the center differential clutch, 55 is the first hollow shaft, 57 is the differential carrier, 59
is the differential pinion, 60° 61 is the side gear, 62 is the second
A hollow shaft, 63 a differential carrier, 65 a differential pinion, 66.67 a side gear, 69.70 a front wheel drive shaft, 71 a center differential case, 72 a rear wheel drive ring gear, 73 a gear, and 75 a drive pinion shaft.

Generally, in a four-wheel drive vehicle with a center differential, when the engine is rotated to the front side, the driving force transmission mechanism becomes as shown in FIG. That is, the rotation of the engine is appropriately changed in speed via an automatic transmission mechanism (not shown) and transmitted to the differential case 52 via the ring gear 51. During normal driving, the center differential clutch 5
3 is in a released state, and in this state, the rotation of the front differential case 52 is transmitted to the differential carrier 57 of the center differential mechanism A via the first hollow shaft 55, and further transmitted from the differential pinion 59 to the left and right side gears 60°61. The rotation of the left side gear 60 is transmitted to the differential carrier 63 of the front differential mechanism B via the second hollow shaft 62, and further transmitted from the differential pinion 65 to the left and right side gears 66, 67, and the left and right front wheel drive shafts 69.
70. On the other hand, the rotation of the right side gear 61 is controlled by the center differential case 71 which is spline connected to the right side gear 61.
It is further transmitted to the drive pinion shaft 75 via the rear wheel drive ring gear 72 and gear 73, and then to the left and right rear wheel drive shafts via a propeller shaft and a rear differential device (not shown).

In addition, when a large driving force is required on frozen roads, sandy roads, uneven roads, etc., or when there is a risk that the wheels may slip, the center differential clutch 53 is engaged and the center differential mechanism A is activated. Lock it. In this state, the rotation of the front differential case 52 is directly transmitted to the differential carrier 63 of the front differential mechanism B via the center differential clutch 53, and further transmitted from the differential pinion 65 to the left and right side gears 6.
6, 67 are transmitted to the left and right front wheel drive shafts respectively 69.7
0. At the same time, front differential case 5
2 and the differential carrier 63 and the hollow shaft 55.
The differential carrier 57 and left side gear 60 of the center differential device A, which are integrated through the differential gear 62, are rotated together without differential movement, and this rotation is further transmitted to the center differential case 71. This allows the rear wheel drive ring gear 7 to rotate at the same speed as the front wheel drive differential carrier 63.
2, and the left and right rear wheel drive shafts are driven.

FIG. 1 shows a block diagram of a control device that engages or releases the center differential clutch 53.
The detection means 1 detects the torque acting on the front wheel or rear wheel drive shaft and variables representing the vehicle condition (vehicle speed, throttle opening or average torque), and the power spectrum analysis section 2 detects the torque acting on the front wheel or rear wheel drive shaft, and the power spectrum analysis section 2 detects the torque acting on the front wheel or rear wheel drive shaft. Frequency analysis is performed on the shaft torque waveform as shown in Fig. 3 (b), and the relationship between frequency and power spectrum as shown in Fig. 3 (b) is determined, and then the peak value PS of the power spectrum and the frequency r corresponding to this PS are calculated. This is to select. In the storage means 3, various road surface conditions corresponding to the peaks (iPS) of the power spectrum measured in advance by actual measurements, the frequency f corresponding to the PS, and the variable ■ representing the vehicle condition are stored in three-dimensional coordinates. , that is, a road surface condition determination map is stored.Road surface condition determination section 4
corresponds and compares the current values of PS, f, and ■ with the road surface condition determination map stored in the storage means 3 to determine the current road surface condition, and the output signal is sent to the center differential control section 5. The signal is sent to control the actuator 6.

Next, the flow of processing of the control device of the present invention will be explained in a different order with reference to FIG. First, the embodiment according to the present invention shown in FIG. 2 will be described. First, the shaft torque T is read, its waveform is frequency analyzed, and the peak value PS of the power spectrum and the frequency f corresponding to that PS are selected. Next, a variable representing the vehicle state, for example, the value of vehicle speed ■ is read,
These values of ps, r, ■ correspond to the road surface condition judgment map,
The condition of the road surface can be judged by comparing. If it determines that the road surface is uneven or sandy, it outputs a signal to lock the center differential, and if it determines that the road is asphalt, it outputs a signal to unlock the center differential.

When unlocking the center differential, the engagement force of the center differential clutch may be changed to allow differential movement in the center differential device to a certain extent.

It should be noted that the present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made.

For example, in the above embodiment, the road surface condition determination map in the storage unit 3 is not corrected, but if the road surface condition is incorrectly determined, this is treated as an abnormal value of the variable representing the vehicle condition, and the PS at that time, Information on f, V, and road surface conditions may be input into the storage section 3 to correct the road surface condition determination map.

As is clear from the above description, according to the present invention, in the four-wheel drive control device of the present invention, the peak value of the power spectrum obtained by frequency analysis of the torque signal, the frequency corresponding to the peak value, and In order to control the center differential to automatically lock or unlock the center differential by comparing and determining the value of a variable representing the vehicle condition with a road surface condition determination map stored in advance, the center differential is automatically locked or unlocked. In addition to being able to make accurate judgments, the configuration of the control device is also simplified, making it possible to maintain stable and safe running conditions that fully utilize the driving force.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of one embodiment of the control system in the control device of the present invention, FIG. 2 is a diagram for explaining the flow of processing by the control device of the present invention, and FIG. 3 is a diagram showing torque waveforms and FIG. 4, which is a diagram showing a power spectrum, is a diagram showing a power transmission system of a four-wheel drive vehicle with a center differential to which the control device of the present invention is applied. 1... Detection means, 2... Power spectrum analysis section,
3... Storage means, 4... Road surface condition determination unit, 5...
Center differential control unit, 6... actuator, tuator, A
...Center differential mechanism, B...Front differential mechanism,
51... Ring gear, 52... Front differential case, 53... Clutch for center differential, 55... First hollow shaft, 57... Differential carrier, 59... Differential pinion, 60.61... Side gear , 62...
Second hollow shaft, 63... Differential carrier, 65...
・Differential gear, 66.67...Side gear, 69.
70...Front wheel drive shaft, 71...Center differential case, 72...Rear wheel drive ring gear, 73...Gear,
75...Drive pinion shaft. Applicant Aisin Warner Co., Ltd. Agent Patent Attorney Hiroki Shirai (2 others) Figure 1

Claims (2)

[Claims] (1) In a four-wheel drive control device equipped with a center differential that allows the difference in rotation speed between the front and rear wheels to absorb the difference in turning radius between the front and rear wheels that occurs during cornering,
Detection means for detecting torque acting on the axle of the front or rear wheels; analysis means for frequency-analyzing the signal from the detection means to select a power spectrum peak value and a frequency corresponding to the power spectrum peak value; and representing the vehicle condition. A detection means for detecting a variable, a storage means for storing in advance a power spectrum peak value, a frequency corresponding to the power spectrum peak value, and a road surface condition corresponding to a variable representing the vehicle condition as a road surface condition determination map, the analysis means, and the vehicle. A road surface condition determining means for comparing and determining a signal from a detecting means for detecting a variable representing the condition with a road surface condition determining map stored in the storage means, and locking or locking the center differential based on the output signal of the road surface condition determining means. A four-wheel drive control device comprising a center differential control means for releasing the center differential. (2) When the center differential is locked or unlocked, if it is detected that the judgment of the road surface condition is incorrect based on the signal from the detection means that detects the variable representing the vehicle condition, the road surface The four-wheel drive control device according to claim 1, wherein the four-wheel drive control device corrects the state determination map.