JP3290227B2 - Vehicle control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a differential control system in which a differential limiting force for a control device of a vehicle, particularly a differential device interposed between left and right wheels or between front and rear axles is obtained by engaging a clutch. The present invention relates to a control device for a vehicle having a motion restriction device.

[0002]

2. Description of the Related Art As is well known, in a vehicle such as an automobile, when an output of an engine is transmitted to a wheel side, for example, when the vehicle turns, a difference in rotation speed occurs between the wheels due to a difference in wheel locus. In order to prevent the occurrence of tire slip and to ensure sufficient maneuverability of the vehicle, the rotational speed difference is mechanically generated by a differential action in the power transmission system from the engine to each wheel side. There is provided a differential device (differential device) that can be absorbed.
That is, in order to absorb the rotational speed difference between the left and right front wheels in a front wheel drive vehicle and between the left and right rear wheels in a rear wheel drive vehicle, a differential for front wheels or rear wheels is used. A device (so-called front differential or rear differential) is provided, and in the case of a four-wheel drive vehicle, in addition to the differential between the left and right wheels, a differential is also provided between the front and rear wheels. A device (a so-called center differential) is provided.

Further, as a differential limiting device for limiting the differential by the differential device in order to properly transmit torque to each wheel, for example, an electromagnetic type multi-plate clutch is engaged to reduce the differential limiting force. What you get is known. In this type of differential limiting device, the clutch engagement force, that is, the differential limiting force can be controlled to a desired level by appropriately controlling the current supplied to the electromagnetic multi-plate clutch.

[0004] When limiting the differential by the engagement force of the multi-plate clutch as described above, it is required to increase the clutch engagement force as the differential rotation (slip) generated between the wheels or the axle increases. However, especially when this slip is excessive, up to the maximum capacity of the clutch (that is, until the clutch engagement force reaches the maximum value)
It is necessary to increase the fastening force and maintain this fastening state. In such a case, the temperature rise on the clutch surface of the friction plate becomes abrupt, and in the worst case, seizure may occur.

To solve this problem, see, for example,
Japanese Patent Application Laid-Open No. 12918 discloses a differential lock device in which the throttle valve opening is reduced when a predetermined time has elapsed after the control current of the electromagnetic multi-plate clutch has reached a maximum value. According to this device, the throttle valve opening decreases when a certain period of time elapses after the control current of the electromagnetic multi-plate clutch reaches the maximum value (that is, the clutch engagement force becomes the maximum value) regardless of the accelerator pedal depression amount. As a result, the engine output is reduced and the input torque to the differential device is reduced, so that it is possible to prevent the seizure of the clutch when excessive slip occurs.

[0006]

Incidentally, in a friction clutch such as the above-mentioned multi-plate clutch, the longer the service period of the friction clutch is, the more the friction plate deteriorates, and the more the degree of deterioration of the friction plate becomes, the more the seizure is likely to occur. Are known. Therefore, if the clutch has been used for a certain period of time or more and its friction plate has deteriorated to a certain degree,
If an excessive slip occurs and the input torque to the device is reduced after a certain period of time after the clutch engagement force reaches the maximum value as in the conventional case, the load on the clutch is reduced before the load is reduced. There is a possibility of burning in.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a control apparatus for a vehicle which can more effectively prevent the seizure of the clutch when an excessive slip occurs even when the friction plate of the clutch is deteriorated to some extent. It was done as.

[0008]

For this reason, the first invention of the present application is designed to obtain a differential limiting force on a differential device provided between left and right wheels or between front and rear axles by engaging a clutch. A control device for a vehicle having a differential limiting device, comprising: detecting means for detecting a degree of deterioration of a friction plate of the clutch, and reducing input torque to the differential device according to a detection result of the detecting means. Control is performed as described above.

According to a second aspect of the present invention, in the vehicle control apparatus according to the first aspect, the detecting means detects the degree of deterioration of the friction plate of the clutch based on the cumulative traveling distance of the vehicle. It is characterized by doing.

Further, according to a third aspect of the present invention, in the vehicle control device according to the first aspect, the detecting means includes a friction plate for the clutch based on a cumulative value of absorbed energy when the clutch is engaged. The feature is to detect the degree of deterioration of.

[0011]

According to the first aspect of the present invention, the degree of deterioration of the friction plate of the clutch is detected by the detection means, and if the friction plate is deteriorated, the differential is determined in accordance with the degree of deterioration. Since the input torque itself to the device can be reduced,
The more the degree of deterioration of the friction plate, the lower the clutch engagement force can be limited. That is, it is possible to more effectively prevent the seizure of the clutch when an excessive slip occurs, and to enhance the reliability of the device when the clutch is used for a long time. In addition, by limiting the input torque to the differential according to the degree of deterioration of the friction plate, it is possible to prevent the driving wheels from idling in a meaningless manner even when an excessive slip occurs. (Road surface friction coefficient) It can also contribute to ensuring the stability of the behavior of the vehicle when traveling on a road or the like.

Further, according to the second aspect of the present invention, basically, the same effects as those of the first aspect can be obtained. In particular, when detecting the degree of deterioration of the friction plate of the clutch, Normally, the degree of deterioration can be relatively easily detected because the detection is performed based on the cumulative traveling distance of the vehicle having a positive correlation with the number of clutch operations.

Further, according to the third aspect of the present invention, basically the same effects as in the first aspect can be obtained. In particular, when detecting the degree of deterioration of the friction plate of the clutch, Since the detection is performed based on the accumulated value of the absorbed energy at the time of engagement of the clutch having a closer correlation with the degree of deterioration, the degree of deterioration can be detected with higher accuracy.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention applied to, for example, a four-wheel drive type automobile will be described in detail with reference to the accompanying drawings. FIG. 1 is an overall configuration diagram schematically showing an overall configuration of a driving force transmission system of an automobile according to the present embodiment. As shown in FIG. 1, in the automobile, the automobile is connected to an output side of an engine 10. Transmission 1
1 is connected to the transfer 12
Have front and rear propeller shafts 13 and 1
4 are connected to one end.

The front end of the front propeller shaft 13 is connected to a front axle 15 via a front differential 21 (hereinafter abbreviated as front differential). The output of the engine 10 is transmitted from the transmission 11 and the transfer 12 to the front axle 15. Front propeller shaft 13, front differential 21, and front axle 1
5 sequentially transmitted to the left and right front wheels 16. The rear end of the rear propeller shaft 14 is connected to a rear axle 17 via a rear differential 22 (hereinafter abbreviated as a rear differential). The output of the engine 10 is transmitted from the transmission 11 and the transfer 12 The power is transmitted to the left and right rear wheels 18 via the shaft 14, the rear differential 22, and the rear axle 17 in order.

The front differential 21 includes left and right front wheels 1
When a rotational speed difference is generated between the front wheels 16, 16, the difference between the rotational speeds is mechanically absorbed when the output of the engine 10 transmitted through the propeller shaft 13 is transmitted to the front wheels 16, 16. This controls the torque distribution to the front wheels 16. The rear differential 22 includes left and right front wheels 1.
When a rotational speed difference is generated between the rear wheels 18 and 18, the rotational speed difference is mechanically absorbed when the output of the engine 10 is transmitted to the rear wheels 18 and 18 via the propeller shaft 14. It controls the torque distribution to each rear wheel 18. Further, the transfer 12 includes the front wheel 1
A center differential 20 (hereinafter abbreviated as a center differential) is provided to control the torque distribution between the 6, 16 side and the rear wheels 18, 18 side.

Wheel speed sensors 30 for detecting the wheel speeds of the respective wheels are provided in the vicinity of the respective wheels 16, 16, 18, and 18. The detection signals (wheel speed signals) of the respective wheel speed sensors 30 are: Are input to a control unit 41 for an anti-skid brake device (hereinafter, referred to as an ABS control unit). In addition, the engine 10 includes:
A throttle sensor 32 for detecting the throttle opening of the engine 10 is attached. A detection signal (throttle opening signal) of the throttle sensor 32 is input to an engine control unit 40. Further, a brake switch 31 for detecting ON / OFF of a brake is provided on the front side of the vehicle. A detection signal (brake signal) of the brake switch 31 is input to a differential control unit 43. The differential control unit 43 is connected with a manual switch 44 and a battery 45 for selecting a differential lock mode, which will be described later.

In the differential control unit 43, in addition to the brake signal from the brake switch 31, a throttle opening signal from the throttle sensor 32, and whether the anti-skid brake device from the ABS control unit 41 is operating. An ABS signal indicating whether or not the wheel switch is present, a wheel speed signal of each of the wheels 16, 16, 18, and 18, and a mode signal from the manual switch 44 are input. In the differential control unit 43, based on these input signals, each of the front, rear and center differential 2
The control current values to be supplied to 1, 22, and 20 are calculated and supplied. The differential limiting force (locking force) of each of the differentials 21, 22, and 20 is controlled according to the supplied control currents (front differential current, rear differential current, and center differential current).
The differential control unit 43
Thereafter, an ABS prohibition signal can be output to the ABS control unit 41.

The front, rear and center differentials 21, 22 and 20 are, for example, center differential 2
Taking the example of 0 as an example, an electromagnetic type multi-plate clutch 50 as shown in FIG. 2 is provided, and the locking force of the center differential 20 is controlled by the engaged state of the multi-plate clutch 50. In the case of the center differential 20, the clutch 50 may be of any other type as long as it can limit the differential between the front propeller shaft 13 and the rear propeller shaft 14.

The multi-plate clutch 50 includes a clutch plate 51 formed by combining a plurality of inner disks and outer disks, and an actuator 52 for applying a pressing force to the clutch plate 51. In addition, 53 is a bearing, 54 is a transmission member for transmission connection to one propeller shaft, and 55 is a transmission member for transmission connection to the other propeller shaft. The actuator 52 is configured such that the armature 57 presses the clutch plate 51 by a magnetic force generated when the solenoid 56 is energized. In the electromagnetic multi-plate clutch 50, the current flowing through the solenoid 56 and the pressing force for frictionally engaging the clutch plate 51.
(That is, the torque generated by the electromagnetic multi-plate clutch 50) is in a proportional relationship, so that the differential rotation speed of the center differential 20 can be continuously changed by increasing or decreasing the current.
The front differential 21 and the rear differential 22 are also provided with electromagnetic multi-plate clutches having the same configuration as described above.

Here, the front and the rear in each differential lock mode selected by the manual switch 44 are described.
Center and rear differentials 21, 20, and 2
Table 1 shows an example of the control contents of No. 2. In the "control contents" column of Table 1, the supply current to the electromagnetic multi-plate clutch of the differential device is 0 (zero) in the case of "unlock", and the maximum current in the case of "complete lock". Value current is supplied.

[0022]

[Table 1]

Each of the above modes is controlled by a manual switch 44.
By operating the, the driver can arbitrarily select, for example, in the "A mode", the front differential 21 is in the unlocked state, so that the driveability is less affected and the operability is excellent. It is suitable for on-road running on ordinary roads such as urban areas. On the other hand, in the “F mode”, since all the differentials 21, 20, and 22 are in the completely locked state, the operability is reduced, but the driveability is excellent. Are suitable. The "C mode" and the "R mode" both have characteristics between the two modes, and are selected according to the driver's preference.

Next, the control of the current supplied to the electromagnetic multi-plate clutch 50 of each differential device by the differential control unit 43 will be described.
When the control is started, first, based on the input signals from the respective wheel speed sensors 30, the left and right front and rear wheels 16, 16, 18, 1
Eight wheel speeds Nfl, Nfr, Nrl, Nrr are calculated. By comparing the calculated values with each other, it is possible to know whether or not any of the wheels is slipping. Also,
From the wheel speeds Nfl, Nfr, Nrl, Nrr, the vehicle speed and the differential rotation speed of each of the differentials 20, 21, 22 can be calculated. Body speed Vsp and differential speed ΔN of center differential 20
The subroutine for calculating the differential rotation speed ΔNr of the rear differential 22 is shown in FIGS. 3, 4 and 5, respectively.

As shown in the flowchart of FIG. 3, when calculating the vehicle speed Vsp, each wheel speed Nfl, Nfr, Nrl, Nrr is calculated.
(Step # 10), and these wheel speeds Nfl, Nfr,
The minimum value of Nrl and Nrr is defined as the vehicle speed Vsp (step # 11). As shown in the flowchart of FIG. 4, when calculating the differential rotation speed ΔNc of the center differential 20, the respective wheel speeds Nfl, Nfr, Nrl, Nrr are input (step #).
20) Based on this input value, a differential rotation speed ΔNc of the center differential 20, which is a rotation difference between the front wheel side and the rear wheel side, is calculated (step # 21). Further, as shown in the flowchart of FIG. 5, when calculating the differential rotation speed ΔNr of the rear differential 22, the left and right rear wheel speeds Nrl and Nrr are input (step #).
30) Based on the input value, a differential rotation speed ΔNr of the rear differential 22, which is a rotation difference between the left and right rear wheels, is calculated (step # 31). The differential rotation speed ΔNf of the front differential 21
Is calculated using the same formula as that for the rear differential 22,
The operation can be performed by replacing rl and Nrr with Nfl and Nfr, respectively.

Next, each differential 2 determined as described above
According to the differential rotation speeds of 0, 21, and 22, each differential 20, 21,
The control current value to be supplied to the solenoid 56 of the electromagnetic multi-plate clutch 50 is calculated. First, an example of calculating the control current value of the center differential 20 will be described. FIG.
FIG. 4 is a flowchart showing a routine for setting a center differential current at the time of auto mode control. As shown in this figure, first, a center differential current Ic is set in step # 40. The center differential current Ic is obtained from the center differential differential speed △ Nc and the throttle opening TVO.
Figure 7 is graph showing the relationship between the current value I ₁ and the center differential differential speed △ Nc, 8 current value I ₂ and the throttle opening TV
FIG. 3 is a diagram showing a relationship with O. That is, when either the center differential differential rotation speed △ Nc or the throttle opening TVO reaches the maximum current value Imax, the center differential current Ic is
"Ic = Imax" is set. When both the center differential rotation speed ΔNc and the throttle opening TVO are equal to or smaller than the maximum current value Imax, the current value I ₁ and the current value I
₂ , a center differential current Ic is determined using a predetermined arithmetic expression.

Next, in step # 41, it is determined whether or not the center differential current Ic is the maximum current value Imax. If the center differential current Ic is different from the maximum current value Imax, that is, if the center differential current Ic is smaller than the maximum current value Imax, the process proceeds to step # 41. In step # 42, "Ic = Ic" is set. At this time, the center differential 20 is in the intermediate locked state, and when "Ic = 0", is in the unlocked state. If the center differential current Ic is the maximum current value Imax, a timer is set in step # 43,
In step # 44, the center differential current Ic is set to "Ic = Im
ax ”. At this time, the center differential 20 is completely locked. Thereafter, the timer is counted up in step # 45, and it is determined in step # 46 whether a predetermined time has elapsed. That is, when the center differential differential rotation speed △ Nc suddenly increases due to a slip or the like, the center differential 20 is kept in a completely locked state for a predetermined time.

Next, an example of calculating the control current value of the rear differential 22 will be described. FIG. 9 is a flowchart showing a rear differential control current value setting routine during the automatic mode control. The rear differential control current value setting routine is basically the same as the above-mentioned center differential control current value setting routine. That is, as shown in FIG.
0, the rear differential current Ir is similarly set, and in step # 51, it is determined whether or not the rear differential current Ir is the maximum current value Imax. If the rear differential current Ir is smaller than the maximum current value Imax, the process proceeds to step # 52. = Ir ”. At this time, the rear differential 22 is in the intermediate lock state, and when "Ic = 0", is in the unlock state. If the rear differential current Ir is the maximum current value Imax, a timer is set in step # 53, and in step # 54, the rear differential current Ir is set to "Ic = Imax". At this time, the rear differential 22 is completely locked. next,
In step # 54, the timer is counted up,
In step # 56, it is determined whether a predetermined time has elapsed. That is, when the rear differential differential speed △ Nr suddenly increases due to slippage or the like, the rear differential 22 is kept in a completely locked state for a predetermined time.

In this embodiment, in order to prevent seizure of the electromagnetic multi-plate clutch 50 when excessive differential rotation (slip) occurs between wheels or axles, a friction plate (clutch plate) of the clutch 50 is provided. 51, the degree of deterioration is detected,
The input torque to the differential device is reduced according to the degree of deterioration. That is, in the present embodiment, although not specifically illustrated, more preferably,
In the differential control unit 43,
For each electromagnetic multi-plate clutch 50, there is provided a calculation circuit capable of calculating a cumulative absorption energy (that is, a cumulative value of the absorption energy when each multi-plate clutch 50 is engaged) which will be described in detail later. The engine output is reduced on the basis of this, and the input torque to the differential device is reduced.

Hereinafter, the calculation of the accumulated absorbed energy and the control of the input torque to the differential device will be described.
The case of the center differential 20 will be described with reference to the flowchart of FIG. During traveling of the vehicle, differential rotation occurs between the front and rear axles 15, 17 depending on the traveling state,
When the operation of the center differential 20 and the control of the differential limiting force for the center differential 20 are started, the absorption energy calculation circuit of the electromagnetic multi-plate clutch 50 for generating the differential limiting force is activated. The total cumulative absorbed energy Ep of the multi-plate clutch 50 in the past is calculated.
This past total accumulated energy Ep is calculated based on the new vehicle state (time: t
= 0) to the present (time: t = Tg), the multi-plate clutch 50 frictionally engages (fastens) its clutch plate 51.
The total energy absorbed by the center differential 20 is detected when the differential limiting force of the center differential 20 acts, that is, when the center differential current Ic is supplied to the solenoid 56 of the multi-plate clutch 50, and the differential is detected. The amount represented by the product of the rotational speed ΔNc and the clutch engagement force Fc is
Can be obtained by integrating over the time range (Tg) in which the belt was actually fastened.

Next, in step # 61, more preferably, the accumulated value of the energy absorbed by the multi-plate clutch 50 between the time before the specified time Th (for example, Th = 1 hour) and the present time, that is, The accumulated absorbed energy Eh within a specified time range up to the time is calculated. With this operation value Eh,
It is possible to know the amount of energy absorbed by the clutch 50 within a specified time range up to the present, and it can be used as a guide, for example, to know the temperature rise state of the clutch plate 51 and the like. Further, in step # 62, more preferably, the current absorbed energy Eg is calculated. Actually, the present absorption energy Eg may be actually obtained by integrating the current ΔNc · Fc in an extremely short time range including the current time Tg. Alternatively, the current value of ΔN · Fc may be used as a reference value indicating the current level of absorbed energy.

In this embodiment, the differential control unit 43 supplies the calculated values Ep, Eh, and Eg obtained as described above and the amount of decrease in the input torque input to the center differential 20 (that is, the required amount of torque reduction). Fc1 (Ep), fc2
(Eh), a map defining fc3 (Eg) is provided,
The amount of decrease in the input torque to the center differential 20 is determined based on these maps and the above-described calculated values Ep, Eh, and Eg. An example of each of the above maps is shown in FIGS.
3 is shown. That is, for the calculated values Ep, Eh, and Eg, the required amounts fc1 (Ep) and fc2 (E
h) and fc3 (Eg) are obtained, and the total value Qt of the required torque-down amounts (total torque-down required amount) is calculated based on the required torque-down amounts fc1 (Ep), fc2 (Eh) and fc3 (Eg). Is calculated (step # 63).

Next, in step # 64, the engine output torque is reduced according to the total torque down request amount Qt. Although not specifically shown in the vehicle according to the present embodiment, the intake system of the engine 10 is driven to open and close in conjunction with the depression operation of an accelerator pedal, and a normal throttle valve (the opening degree of which is controlled) is controlled. (So-called mechanical throttle valve)
In addition, a so-called electric throttle valve is provided, which is driven to open and close by an electric actuator and can control the amount of intake air by operating this actuator in accordance with an electric signal.

In this embodiment, for example, the mechanical throttle valve is used as a main throttle valve, and the electric throttle valve is used as an auxiliary throttle valve. In this way, by providing the two throttle valves in the engine intake passage and controlling the amount of intake air with the two throttle valves, the output characteristics of the engine 10 can be more finely controlled than in the case where control is performed only with the mechanical throttle valve. Further, the output characteristics of the engine 10 can be changed according to the driving state of the vehicle. In other words, by providing such an electric throttle valve, the throttle opening characteristic (engine output characteristic) with respect to the accelerator pedal depression amount can be freely set by the electric signal processing, and even if the accelerator pedal depression amount is the same. The engine output can be changed within the range of the opening characteristic of the electric throttle valve. The engine output torque reduction in step # 64 is more preferably performed exclusively by controlling the electric throttle valve. Note that the engine output torque reduction in step # 64 can also be executed by, for example, shifting the ignition advance angle of the engine 10 to the retard side.

When the output torque of the engine 10 is decreased in step # 64, the automatic transmission is shifted up in step # 65 in response to the torque reduction.
Thus, the input torque input to the center differential 20 is reduced, and the load on the electromagnetic multi-plate clutch 50 is reduced. The shift-up of the automatic transmission for reducing the load on the clutch 50 in accordance with the degree of deterioration of the clutch plate 51 is at least directly performed by a driver's actual shift operation or other control corresponding to the driving state of the vehicle. Is performed in a range that does not interfere with That is, when the driver is actually performing a gearshift operation, or while driving with the so-called engine brake applied, or while the anti-skid brake device is operating, the above-mentioned upshifting is performed. It is not executed at the same time.

As described above, according to the present embodiment, the degree of deterioration of the friction plate 51 (clutch plate) of the clutch 50 is detected by the above-mentioned clutch absorbed energy calculation circuit.
When the clutch plate 51 is deteriorated, the input torque itself to the differential device 20 (center differential) can be reduced according to the degree of deterioration. The force Fc can be limited low. That is, the seizure of the clutch 50 when the excessive slip ΔNc occurs can be more effectively prevented, and the reliability of the device when used for a long period of time can be improved. In addition, by limiting the input torque to the center differential 20 according to the degree of deterioration of the clutch plate 51, it is possible to prevent the driving wheels from idling in a meaningless manner even when an excessive slip occurs. (Road surface friction coefficient) It can also contribute to ensuring the stability of the behavior of the vehicle when traveling on a road or the like.

In particular, in this embodiment, when detecting the degree of deterioration of the clutch plate 51 of the clutch 50, the degree of deterioration is detected based on the accumulated absorbed energy Ep, Eh of the clutch 50 which has a closer correlation with the degree of deterioration. As a result, it is possible to detect the degree of deterioration with higher accuracy.

In the above embodiment, when detecting the degree of deterioration of the clutch plate 51 of the clutch 50, the clutch 50
Although the detection is performed based on the two types of accumulated absorption energies Ep and Eh, the detection may be performed based on a calculated value of one of the accumulated absorption energies. Further, instead of being based on the accumulated absorption energies Ep and Eh, the detection may be usually made based on the accumulated traveling distance of the vehicle having a positive correlation with the number of times of operation of the clutch 50. That is, a map that defines a torque-down request function fc4 (Lp) that determines the relationship between the past total cumulative traveling distance Lp of the vehicle and the decrease in the input torque input to the center differential 20 is provided to the differential control unit 43 (FIG. 14). When the vehicle is running, a differential rotation occurs between the front and rear axles 15 and 17, and when the operation of the center differential 20 and the control of the differential limiting force on the center differential 20 are started, the vehicle is driven. While calculating the total accumulated traveling distance Lp, based on the calculated value Lp and the above map,
The amount of decrease in the input torque to the center differential 20 may be determined, and the output torque of the engine 10 may be decreased according to the amount of decrease.

As described above, when the degree of deterioration of the clutch plate 51 of the clutch 50 is detected based on the cumulative traveling distance Lp of the vehicle, the clutch 5
The detection of the degree of deterioration can be simplified as compared with the case where detection is performed based on the accumulated absorption energies Ep and Eh of 0.

The calculated value of the cumulative running distance Lp of the vehicle is combined with the calculated value of at least one of the cumulative absorbed energy Ep and Eh of the clutch 50, and the clutch plate 51 of the clutch 50 is determined based on these calculated values. When detecting the degree of deterioration, for example, the degree of deterioration is detected, various measures can be taken in order to achieve both simplification and maintenance of accuracy.

In each of the above-described embodiments, basically, the case where the seizure of the clutch provided in the center differential 20 is prevented is intended. Needless to say, the present invention can also be effectively applied to a case in which seizure of a clutch provided on the rear differential 21 or the rear differential 22 is prevented.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram schematically showing an overall configuration of a driving force transmission system of an automobile according to an embodiment of the present invention.

FIG. 2 is an explanatory sectional view showing an example of an electromagnetic multi-plate clutch provided in a differential of the automobile.

FIG. 3 is a flowchart showing a subroutine for calculating a vehicle body speed of the automobile.

FIG. 4 is a flowchart showing a subroutine for calculating a differential rotation speed of a center differential of the automobile.

FIG. 5 is a flowchart showing a subroutine for calculating a differential rotation speed of a rear differential of the vehicle.

FIG. 6 is a flowchart illustrating a center differential current setting routine during auto mode control.

FIG. 7 is a graph showing an example of a relationship between a current value and a differential speed of a center differential.

FIG. 8 is a graph showing an example of a relationship between a current value and a throttle opening.

FIG. 9 is a flowchart showing a routine for setting a rear differential current during auto mode control.

FIG. 10 is a flowchart illustrating detection of the degree of deterioration of the friction plate of the clutch of the center differential and control of input torque to the center differential.

FIG. 11 is a diagram illustrating an example of a map that determines a relationship between past total accumulated absorbed energy and a required amount of torque down.

FIG. 12 is a diagram showing an example of a map that determines the relationship between the total accumulated absorbed energy within a specified time range and the required amount of torque down.

FIG. 13 is a diagram showing an example of a map that determines the relationship between the current absorbed energy and the required amount of torque down.

FIG. 14 is a diagram illustrating an example of a map that determines a relationship between a cumulative traveling distance of a vehicle and a required amount of torque reduction.

[Explanation of symbols]

 Reference Signs List 15 front axle 16 front wheel 17 rear axle 18 rear wheel 20 center differential (center differential) 21 front differential (front differential) 22 rear differential (rear differential) 43 differential control unit 50 electromagnetic multi-plate clutch 51 Clh plate Eh: Cumulative absorbed energy within a specified time range Ep: Total cumulative absorbed energy in the past Lp: Cumulative running distance of the vehicle Qt: Total torque down required

Claims (3)

(57) [Claims] 1. A control device for a vehicle having a differential limiting device in which a differential limiting force for a differential device interposed between left and right wheels or between front and rear axles is obtained by engaging a clutch. A control unit for detecting the degree of deterioration of the friction plate, wherein the control unit controls the input torque to the differential device to decrease in accordance with a detection result of the detection unit. 2. The vehicle control device according to claim 1, wherein said detecting means detects a degree of deterioration of the friction plate of the clutch based on an accumulated traveling distance of the vehicle. 3. The apparatus according to claim 1, wherein said detecting means detects a degree of deterioration of a friction plate of said clutch based on a cumulative value of absorbed energy when said clutch is engaged.
The control device for a vehicle according to any one of the preceding claims.