JP3327608B2 - 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 control device for a vehicle, and more particularly, to a differential device between an inter-axle differential device disposed between left and right wheels and an inter-axle differential device disposed between front and rear axles. The present invention relates to a control device for a vehicle including a differential limiting control device capable of changing a limiting force.

[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. A differential device (abbreviated as differential device; or abbreviated as differential) is provided. 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 (a so-called front differential or rear differential) is provided, and in a four-wheel drive vehicle,
In addition to the differential device between the left and right wheels, a differential device (a so-called center differential) is provided between the front wheel side and the rear wheel side.

In order to properly transmit torque to each wheel, a differential limiting device for limiting the differential by the differential device is provided, and a differential limiting force for each differential device can be changed. Providing a limit control device has conventionally been considered. For example, JP
According to Japanese Patent Application Laid-Open No. 2-166114, in a four-wheel drive vehicle, the driving force to each wheel is automatically controlled according to the running state of the vehicle by controlling the differential limiting force for each of the front, center and rear differentials. What is controlled is disclosed.

[0004]

When the differential limiting force for each differential is changed as described above, the running vehicle may have different behavior characteristics depending on the differential limiting state of each differential. It has been known. For example,
In general, when the rear differential is locked, the tendency of oversteer during turning becomes strong, and when the center differential is unlocked, the front and rear differential is allowed,
Generally, slip is likely to occur. That is, when each differential is locked / unlocked by controlling the differential limiting force for each differential, various differential limiting patterns can be obtained depending on the combination of the differential limiting forces. The vehicle's behavior characteristics (that is, running stability).

Therefore, the present invention aims to improve the running stability by controlling the input torque to the driving force transmission system according to the differential limiting state or differential limiting pattern of each differential. An object of the present invention is to provide a vehicle control device capable of improving running performance while ensuring stability.

[0006]

[0007]

SUMMARY OF THE INVENTION Therefore, a first invention of the present application is directed to an inter-wheel differential device interposed between left and right wheels and an inter-axle differential device interposed between front and rear axles. In a vehicle control device provided with a differential limiting control device capable of changing a differential limiting force, control is performed such that an input torque to a driving force transmission system is changed according to a differential limiting force applied to each of the differential devices. When the differential limiting force for the inter-axle differential is greater than the differential limiting force for the inter-wheel differential, control is performed to increase the input torque.

Further, the second invention of the present application changes the differential limiting force for the inter-wheel differential device interposed between the left and right wheels and the inter-axle differential device interposed between the front and rear axles, respectively. In a vehicle control device provided with a differential limiting control device capable of causing the differential between the wheels to be controlled, the input torque to the driving force transmission system is changed in accordance with the differential limiting force for each of the differential devices. When the differential limiting force applied to the device is larger than the differential limiting force applied to the inter-axle differential, control is exercised to reduce the input torque.

Further, a third invention of the present application is the control apparatus for a vehicle according to the first or second invention, wherein the vehicle is provided between a front differential provided between left and right front wheels and a left and right rear wheel. And a center differential interposed between the front and rear axles, and controls to change the input torque in accordance with a differential limiting pattern for these three differentials. It is a characteristic.

In a fourth aspect of the present invention, in the vehicle control device according to the third aspect, when the differential limiting force acts only on the center differential, all the differentials are different. It is characterized in that the input torque is controlled so as to be higher than the current value as compared with the case where the movement is not restricted.

Further, according to a fifth aspect of the present invention, in the vehicle control apparatus according to the third aspect, when a differential limiting force is applied only to the rear differential, all differentials are different. It is characterized in that the input torque is controlled so as to be reduced from the current value as compared with the case where the movement is not restricted.

Further, according to a sixth aspect of the present invention, in the vehicle control apparatus according to the third aspect, when the differential limiting force is acting only on the front differential, all the differentials are turned off. It is characterized in that the input torque is controlled so as to be further reduced from the current value as compared with the case where the differential limitation is not performed.

Further, according to a seventh aspect of the present invention, in the vehicle control device according to the third aspect, a differential limiting force acts on the center differential and the rear differential, and the front differential has a differential limiting force. If not, control is performed such that the input torque is increased from the current value as compared with the case where all differentials are not differentially limited.

Further, according to an eighth aspect of the present invention, in the vehicle control apparatus according to the third aspect, a differential limiting force acts on the front differential and the rear differential, and the center differential has a differential limiting force. If not, control is performed such that the input torque is further reduced from the current value as compared with the case where all differentials are not differentially limited.

According to a ninth aspect of the present invention, in the vehicle control apparatus according to the third aspect of the present invention, a differential limiting force acts on the front differential and the center differential, and the rear differential has a differential limiting force. If not, control is performed such that the input torque is increased from the current value as compared with the case where all differentials are not differentially limited.

Further, according to a tenth aspect of the present invention, in the vehicle control device according to the third aspect of the present invention, when the differential limiting force is acting on all the differentials, all the differentials are activated. It is characterized in that the input torque is controlled so as to be higher than the current value as compared with the case where the differential limitation is not performed.

[0017]

[0018]

According to the first aspect of the present invention, the input torque to the driving force transmission system is changed according to the differential limiting state of each differential. Therefore, when the behavior that affects the traveling performance and the maneuverability of the vehicle is likely to occur in the differential limited state in accordance with the differential limited state of each differential, the input torque is reduced to reduce the input torque of the vehicle. The running stability can be improved. In addition, when the above-described behavior does not particularly occur in the differential limiting state, by increasing the input torque, it is possible to improve running performance while securing running stability. In particular, when the differential between the axles has a larger differential limiting force than the differential between the wheels, that is, the differential between the front and rear is more strongly limited, and basically, slip between the front and rear wheels is less likely to occur and running stability is improved. Is ensured, the running performance can be improved by increasing the input torque.

According to the second aspect of the present invention, the input torque to the driving force transmission system is changed according to the differential limiting state of each differential. Therefore, according to the differential limiting state of each differential,
In a case where a behavior that affects the traveling performance and the maneuverability of the vehicle is likely to occur in the differential limiting state, the traveling stability of the vehicle can be improved by reducing the input torque. In addition, when the above-described behavior does not particularly occur in the differential limiting state, by increasing the input torque, it is possible to improve running performance while securing running stability. In particular, when the differential between wheels is larger in differential limiting force than the differential between axles, that is, when slip between front and rear wheels is likely to occur, and when understeer or oversteer tends to occur, the input torque is reduced. By doing so, these tendencies can be suppressed and running stability can be improved.

Furthermore, according to the third aspect of the present invention, basically, the same effects as those of the first or second aspect can be obtained. For vehicles equipped with such differential limiting patterns, if the differential limiting patterns tend to cause a behavior that affects the traveling performance and maneuverability of the vehicle, the input torque is reduced. Therefore, these behaviors can be suppressed, and the running stability of the vehicle can be improved. Further, when the above-described behavior does not particularly occur in the differential limiting pattern, by increasing the input torque,
Driving performance can be enhanced while ensuring running stability.

Further, according to the fourth invention of the present application,
Basically, the same effects as those of the third invention can be obtained. In particular, when the differential limiting force is acting only on the center differential, that is, the front and rear differentials are limited, and On the other hand, when slippage between the front and rear wheels hardly occurs and traveling stability is ensured, the traveling performance can be enhanced by further increasing the input torque.

Further, according to the fifth invention of the present application,
Basically, the same effects as those of the third invention can be obtained. In particular, when the differential limiting force is acting only on the rear differential, that is, when the oversteering tendency is likely to occur,
By further reducing the input torque, this tendency can be suppressed and running stability can be improved.

Further, according to the sixth invention of the present application,
Basically, the same effects as those of the third aspect can be obtained. In particular, when the differential limiting force is acting only on the front differential, that is, slip between the front and rear wheels is likely to occur,
When the understeering tendency is likely to occur, the driving stability can be improved by further reducing the input torque.

Further, according to the seventh invention of the present application,
Basically, the same effects as those of the third invention can be obtained. In particular, when the differential limiting force acts on the center differential and the rear differential and the front differential is free, that is, there is a tendency for oversteer to some extent. Basically, when the slip between the front and rear wheels hardly occurs and the running stability is ensured, the running performance can be enhanced by further increasing the input torque.

Further, according to the eighth invention of the present application,
Basically, the same effects as those of the third invention can be obtained. In particular, when the differential limiting force acts on the front differential and the rear differential and the center differential is free, that is, slip occurs between the front and rear wheels. If it is easy and the tendency of oversteering occurs to some extent, it is possible to improve the running stability by further reducing the input torque.

Further, according to a ninth invention of the present application,
Basically, the same effects as those of the third aspect can be obtained. In particular, when the differential limiting force acts on the front differential and the center differential and the rear differential is free, that is, understeer tends to occur to some extent. Basically, when slippage does not occur between the front and rear wheels and traveling stability is ensured, the traveling performance can be enhanced by further increasing the input torque.

Further, according to the tenth aspect of the present invention, basically the same effects as those of the third aspect can be obtained. In particular, the differential limiting force acts on all the differentials. In this case, basically, that is, when slippage between the front and rear wheels hardly occurs and running stability is ensured, the running performance can be improved by further increasing the input torque.

[0028]

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, and 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.

The differential control unit 43 receives, 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.

Each of the front, rear and center differentials 21, 22 and 20 is, for example, a 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.

[0036]

[Table 1]

Each of the above modes is controlled by the 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, and the drive is suitable for off-road running on a rough road or the like. ing. The "C mode" and the "R mode" both have characteristics between the two modes, and are selected according to the driver's preference. In each mode, each differential 2
The differential limiting forces for 1,20,22 are respectively controlled,
Although various differential limiting patterns can be obtained, in this embodiment,
This differential limiting pattern is
In addition to those obtained by the mode selection by the operation of, various different patterns can be obtained according to various conditions such as, for example, the vehicle speed, the vehicle running state, the input of the ABS signal and the brake signal, and the like. I have.

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 body speed Vsp, each wheel speed Nfl, Nfr, Nrl, Nrr
(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 obtained 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, the driving force is transmitted to the driving force transmission system in accordance with the respective differential limiting patterns obtained by changing the differential limiting forces for the front, center and rear differentials 21, 20, and 22, respectively. By changing and controlling the input torque, the running stability of the vehicle is improved, and the running stability is improved while the running stability is ensured. That is, in this embodiment,
Various differential limiting patterns can be obtained by changing the differential limiting force for each of the differentials 21, 20, and 22, respectively. Of these, eight types of differential limiting patterns as shown in Table 2 are used. Therefore, when the differential limiting pattern tends to cause a behavior that affects the traveling performance and maneuverability of the vehicle, the input torque to the drive transmission system is reduced. When no special behavior occurs, the output torque of the engine 10 is controlled to increase the input torque.

[0044]

[Table 2]

In Table 2, the differentials marked with ○ indicate the differential lock state (completely locked), and those without the mark indicate the unlocked state (completely free). In this embodiment, more preferably, each of the differentials 21 and 2
The center differential 20 has the largest differential limiting force at full lock with respect to
Is set to be large and the front differential 21 is set to be the smallest. Therefore, the center differential 20 and the other differential 2
When the differential locks 1 and 22 are simultaneously locked, the differential of the center differential 20 is most strongly limited.

Hereinafter, control of the input torque to the drive transmission system according to the differential limiting pattern will be described with reference to the flowchart of FIG. While the vehicle is running, the front, center and rear differentials 21 and 20
When the control of the differential limiting force on the differentials 21, 20 and 22 is started, first, in step # 60, the differential control unit 43 recognizes the differential limiting pattern and controls each wheel speed Nfl. , Nfr, Nrl, Nrr are read.
The differential limiting pattern is provided for each of the differentials 21 and 2
It can be recognized by reading the control current values supplied to 0 and 22, respectively.

Next, at step # 61, a driving force correction characteristic corresponding to the recognized differential limiting pattern is called, and then at step # 62, the maximum differential rotation speed Δ between the wheels.
N, that is, the difference between the maximum wheel speed and the minimum wheel speed among all the wheels is calculated. In the present embodiment, the differential control unit 43 corrects the driving force (input torque to the drive transmission system) for each differential limiting pattern, that is, the driving force correction characteristic, that is, the maximum differential rotation speed ΔN And a map that defines a correction characteristic line that defines the relationship between the driving force correction amount ΔTh and the driving force correction amount ΔTh. FIG. 11 shows an example of this map. The map shown in FIG. 11 shows correction characteristic lines S1 to S1 corresponding to the full differential limiting patterns
Although S8 is collectively displayed in one graph, it is actually provided individually for each differential limiting pattern.
The one corresponding to the differential restriction pattern recognized in step # 60 is called. Then, in step # 63, a correction value ΔTh of the driving force is calculated based on the map and the maximum differential rotation speed ΔN. In step # 64, the correction value ΔTh is added to the current driving force Tg to obtain the target driving force. T is calculated.

Next, in step # 65, the engine output torque is increased or decreased in accordance with the target driving force T. 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. In addition to a so-called mechanical throttle valve), a so-called electric throttle valve is provided, which is driven to open and close by an electric actuator, and the amount of intake air can be controlled by operating this actuator according to an electric signal. ing.

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 increase or decrease of the engine output torque in step # 65 is more preferably executed by exclusively controlling the electric throttle valve. The increase / decrease of the engine output torque in step # 65 can be executed, for example, by shifting the ignition advance angle of the engine 10 to the retard side.

When the output torque of the engine 10 is increased or decreased in step # 65, the automatic transmission is shifted in response to the change in the engine output torque in step # 66, and is thus input to the drive transmission system. The input torque is controlled to be changed. The shift change of the automatic transmission for changing and controlling the input torque in accordance with the differential limiting pattern is at least directly interfering with the actual shift operation of the driver and other controls corresponding to the driving state of the vehicle. It is executed in the range not to do. In other words, when the driver is actually performing a shift operation,
Alternatively, the above-described shift change is not performed simultaneously with the vehicle while the vehicle is running with the so-called engine brake or the anti-skid brake device is operating.

With reference to Table 1 and FIG. 11, the correction characteristic for each of the differential limiting patterns (1) to (5) will be described. The center differential 20 is locked (in other words,
The center differential 20 provided between the axles has a larger differential limiting force than the front or rear differentials 21 and 22 provided between the wheels.) Since there is no behavior characteristic that particularly adversely affects the driving performance and steering stability, it is possible to enhance running performance while ensuring running stability. Therefore, in this case, the driving force correction amount ΔTh is set to always be a value of + (plus). In the present embodiment, more preferably, when all the differentials 21, 20, and 22 are unlocked and the differential is not limited (differential limit pattern), the driving force is not corrected (correction characteristic). (See line S5), and the correction value ΔTh is 0 (zero).

In particular, in the differential limiting pattern in which only the center differential 20 is locked, there is no front-back differential, and in addition, left-right differential is allowed during turning, so that the road surface gripping force of each wheel can be sufficiently increased. Such as
This is the most advantageous in terms of running stability, and therefore, it is possible to maximize running performance (see the correction characteristic line S1). Further, in the differential limiting pattern in which all the differentials 21, 20, and 22 are locked, compared to the differential limiting pattern,
Although the road surface gripping force at the time of turning is reduced, the running stability is excellent, so that the running performance can be considerably improved (see the correction characteristic line S2). Furthermore, the front differential 21
In the differential limiting pattern in which the center differential 20 and the rear differential 22 are locked and the rear differential 22 is unlocked, the vehicle tends to understeer slightly when turning, but does not tend to oversteer. No effect (see correction characteristic line S3). Also,
Further, in the differential limiting pattern in which the center differential 20 and the rear differential 22 are locked and the front differential 21 is in an unlocked state, although a slight tendency of oversteer occurs during turning, the front and rear differential does not occur due to the fastening of the center differential 20. In addition, it is possible to slightly improve the running performance without impairing the running stability (refer to the correction characteristic line S4).

On the other hand, the center differential 20 is unlocked.
(In other words, the front or rear differentials 21 and 22 provided between the wheels have a larger differential limiting force than the center differential 20 provided between the axles.)
Since the front-rear differential is likely to occur and slip is likely to occur, and the vehicle tends to understeer or oversteer during turning, it is preferable that the input torque input to the drive transmission system be low in order to secure running stability. Therefore, in this case, the driving force correction amount ΔTh is always set to a value of − (minus).

In particular, in the differential limiting pattern in which only the rear differential 22 is locked, the tendency of oversteering tends to appear strongly during turning, so that the driving force is reduced most greatly so as not to promote this (correction characteristic line). S8
reference). In the differential limiting pattern in which the front differential 21 and the rear differential 22 are locked and the center differential 20 is in the unlocked state, although the steering tends to be over-steered, although not as much as in the differential limiting pattern, the driving force is reduced and the driving force is reduced. It is necessary to ensure stability (see the correction characteristic line S7). Further, in the differential limiting pattern in which only the front differential 21 is locked, there is no tendency to oversteer, but the center differential 20 is in the unlocked state, the front and rear differentials occur, and it is difficult to obtain sufficient running stability. Therefore, it is better to lower the driving force (see the correction characteristic line S6).

As described above, according to the present embodiment, in a vehicle provided with three differentials 21, 20, and 22 of front, center, and rear, the difference is determined according to the differential limiting pattern of these differentials. If the behavior that affects the driving performance and maneuverability of the vehicle tends to occur in the motion restriction pattern,
By reducing the input torque T to the drive transmission system from the current value Tg, these behaviors can be suppressed and the running stability of the vehicle can be improved. In addition, when the above-described behavior does not particularly occur in the differential limiting pattern, by increasing the input torque T above the current value Tg, it is possible to increase running performance while securing running stability. It is.

Although the above embodiment has been described with reference to a case of a 4WD vehicle provided with three differentials of a front differential 21, a center differential 20, and a rear differential 22, the present invention
It is not limited to such a case, and the axle differential (center differential) and 1
The present invention can also be effectively applied to a vehicle provided with only two differentials, such as a differential between wheels (for example, a rear differential). In other words, when the differential between the axles has a larger differential limiting force than the differential between the wheels, that is, the differential between the front and rear is more strongly restricted, and basically, slip between the front and rear wheels is hardly generated and the running stability is reduced. Is ensured, the running performance can be improved by increasing the input torque to the drive transmission system. On the other hand, if the differential between wheels is larger in differential limiting force than the differential between axles, that is, if slip between front and rear wheels is likely to occur, and if there is a tendency to understeer or oversteer, the input torque is reduced. By doing so, these tendencies can be suppressed and running stability can be improved.

[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 control of a driving force according to a differential limiting pattern of a differential.

FIG. 11 is a diagram illustrating an example of a map that determines a relationship between a maximum differential rotation speed and a driving force correction amount.

[Explanation of symbols]

 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 T, Tg input torque (drive) Force) ΔTh: Driving force correction value

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI F16H 48/20 B60K 17/20

Claims (10)

(57) [Claims] 1. A differential limiting control device capable of changing a differential limiting force between an inter-wheel differential device interposed between left and right wheels and an inter-axle differential device interposed between front and rear axles, respectively. A control device for a vehicle, comprising: controlling the input torque to a driving force transmission system to be changed in accordance with the differential limiting force for each of the differential devices, wherein the differential limiting force for the inter-axle differential device is A control device for a vehicle, wherein the control is performed to increase the input torque when the differential torque is larger than the differential limiting force for the inter-wheel differential device. 2. A differential limiting control device capable of changing a differential limiting force for an inter-wheel differential device interposed between left and right wheels and an inter-axle differential device interposed between front and rear axles. A control device for a vehicle, comprising: controlling to change an input torque to a driving force transmission system according to a differential limiting force to each of the differential devices; A control device for a vehicle, wherein the input torque is controlled to be reduced when the differential torque is larger than a differential limiting force for an inter-axle differential device. 3. The vehicle according to claim 1, wherein the front wheel differential is interposed between left and right front wheels, the rear wheel differential is interposed between left and right rear wheels, and an axle interposed between front and rear axles. The vehicle according to claim 1, further comprising a differential device, wherein the input torque is controlled to be changed in accordance with a differential limiting pattern for the three differential devices. Control device. 4. When the differential limiting force acts only on the inter-axle differential, the input torque is reduced from the current value as compared with the case where the differential is not limited on the full differential. 4. The control device for a vehicle according to claim 3, wherein the control is performed to increase the control value. 5. When the differential limiting force is acting only on the rear wheel differential, the input torque is reduced from the current value as compared with the case where the differential is not limited on all the differentials. 4. The control device for a vehicle according to claim 3, wherein the control is performed so as to lower the vehicle speed. 6. When the differential limiting force is acting only on the front wheel differential, the input torque is further reduced from the current value as compared with the case where the differential is not limited on all the differentials. 4. The control device for a vehicle according to claim 3, wherein the control is performed such that the vehicle is driven. 7. When a differential limiting force acts on the inter-axle differential and the rear wheel differential and the front wheel differential is not differentially limited, the differential of the full differential is The vehicle control device according to claim 3, wherein the control is performed such that the input torque is increased from a current value as compared with a case where the movement is not restricted. 8. When a differential limiting force acts on the front wheel differential and the rear wheel differential and the inter-axle differential is not differentially limited, the total differential is differential. The vehicle control device according to claim 3, wherein the control is performed such that the input torque is reduced from a current value as compared with a case where the movement is not restricted. 9. When a differential limiting force acts on the front wheel differential and the inter-axle differential and the rear wheel differential is not differentially limited, the full differential is The vehicle control device according to claim 3, wherein the control is performed such that the input torque is increased from a current value as compared with a case where the movement is not restricted. 10. When the differential limiting force is acting on the fully differential device, the input torque is increased from a current value as compared with a case where the fully differential device is not differentially limited. The vehicle control device according to claim 3, wherein the control is performed in the following manner.