JPH0891077A - Four wheel drive controller for vehicle - Google Patents

Abstract

PURPOSE: To provide a device which prevents the traveling stability and the performance of a power train system from being impaired, by preventing the directly connected four-wheel driving state from being caused, when a special diameter wheel is installed. Such as in the case where a small diameter wheel for emergency is installed. CONSTITUTION: The detection value ΔVW of the wheel speed difference between the front and rear wheels and the threshold value ΔVW0 which is previously set according to the pseudo car speed VFF are compared, and if it is judged that the vehicle is in a directly connected four wheel drive state prohibition region, the directly connected four wheel drive state prohibition signal SN (S121) is outputted, and the front wheel side torque distribution instruction value is set to the value outside the directly connected four-wheel driving state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses one of the front and rear wheels of a vehicle as a main driving wheel and the other as a sub driving wheel, and distributes the driving force between the front and rear wheels corresponding to the main driving wheel and the sub driving wheel. The present invention relates to a control device for a four-wheel drive vehicle, which can be changed according to a selected drive mode or a deviation in rotational speeds of front and rear wheels corresponding to main drive wheels and auxiliary drive wheels.
The present invention relates to a four-wheel drive control system for a vehicle, which is compatible with vehicles equipped with wheels of different diameters.

[0002]

2. Description of the Related Art Conventional four-wheel drive vehicles include a part-time four-wheel drive vehicle in which a two-wheel drive mode and a four-wheel drive mode can be selected by operating a lever or a switch when necessary, and a main drive. There is a full-time four-wheel drive vehicle in which the driving force distribution between the front and rear wheels corresponding to the wheels and the auxiliary drive wheels is automatically changed and controlled.

In a part-time four-wheel drive vehicle, when the two-wheel drive mode is selected, the drive force distribution to the auxiliary drive wheels is "0" (the drive force distribution to the main drive wheels is "1".
When the four-wheel drive mode is selected, for example, when the rotation speed of the main drive wheels becomes higher than the rotation speed of the auxiliary drive wheels when the four-wheel drive mode is selected, "50%" distribution of driving force to auxiliary drive wheels
(Drive power distribution to the main drive wheels is set to "50%") to establish a direct drive four-wheel drive state. Further, in a full-time four-wheel drive vehicle, the driving force distribution between the front and rear wheels corresponding to the main drive wheel and the auxiliary drive wheel is distributed according to the deviation of the rotational speeds of the front and rear wheels corresponding to the main drive wheel and the auxiliary drive wheel. Is continuously changed from the two-wheel drive state to the direct-coupled four-wheel drive state.

Further, a two-wheel drive mode, an automatic four-wheel drive mode (as in the case of the full-time four-wheel drive vehicle, a mode in which the driving force distribution between the front and rear wheels is automatically changed and controlled), and a directly connected four-wheel drive mode. There are also four-wheel drive vehicles in which the selection of drive modes can be selected by operating levers or switches. Various devices are known as devices that are mounted on such a four-wheel drive vehicle and that can change the driving force distribution between the front and rear wheels corresponding to the main driving wheels and the auxiliary driving wheels stepwise or continuously. ing. Among them, for example, a drive force transmission system between the front and rear wheels, a variable torque clutch mechanism capable of variably controlling the transmission torque by variably controlling the fastening force,
Some include a differential device with a limiting mechanism (so-called limited slip center differential mechanism), and the distribution of the driving force to the front and rear wheels is adjusted by adjusting the transmission torque by these mechanisms. Among them, the variable torque clutch is currently mainly of a fluid type or an electromagnetic type. Among them, the fluid type variable torque clutch is a solenoid type by controlling a fluid pressure to a clutch piston. The variable torque clutch variably controls the frictional contact force between the clutch plates by controlling the current value to the proportional electromagnetic solenoid to control the engagement force thereof, thereby controlling the transmission torque.

Then, in each of the four-wheel drive vehicles described above,
The main drive wheel is changed from the state where the main drive wheel and the sub drive wheel are allowed to rotate at different speeds due to the selection of the direct drive four wheel drive mode by the driving vehicle and the automatic shift to the direct drive four wheel drive state. In some cases, the auxiliary drive wheel and the auxiliary drive wheel are directly connected to each other and rotate at the same speed. For example, in a part-time four-wheel drive vehicle, as a result of selecting the four-wheel drive mode in order to improve running performance, a transition from the two-wheel drive state to the direct-coupled four-wheel drive state is made, and a full-time four-wheel drive vehicle. In the above, when the vehicle escapes from the muddy state, for example, the limited slip center differential mechanism is used to shift to the direct drive four-wheel drive state.

[0006]

However, when the diameter of at least one of the four wheels mounted on the vehicle is smaller than the diameter of the other wheels, such as when an emergency wheel is mounted. Therefore, it is necessary to allow a wheel having a small diameter to rotate at a faster speed than other wheels without setting the direct-drive four-wheel drive state. That is, in such a state where the wheels with different diameters are mounted, when the main drive wheel and the auxiliary drive wheel are directly connected and both axles rotate at the same speed in the direct-coupled four-wheel drive state, the diameter that should rotate fast is small. On the wheels
The braking force acts relatively due to the difference in the rotational peripheral speed with the other wheels, whereby the cornering force changes from the concept of the friction circle, and the running state of the vehicle becomes unstable. In addition, if the vehicle is continuously driven in the four-wheel drive mode with the wheels with different diameters attached, the speed difference between the wheels that follow the road and the speed difference between the wheels that are rotated by the axle is transmitted to the powertrain system. Therefore, the load on the power train system becomes large, which is not preferable.

The present invention has been made by paying attention to the problems of the prior art as described above. When the different-diameter wheels as described above are mounted, the direct drive four-wheel drive state is not set, so that the running stability and the power train are improved. An object of the present invention is to provide a four-wheel drive control system for a vehicle in which system performance is not impaired.

[0008]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned conventional problems, the inventors of the present invention obtained the following knowledge and completed the respective inventions of the present invention. That is, in the conventional four-wheel drive vehicle, the driving force distribution of the main and auxiliary drive wheels is
In the case of a full-time four-wheel drive vehicle and by selecting the above-mentioned automatic four-wheel drive mode, for example, a value corresponding to the front-rear wheel rotational speed difference, and by selecting the direct-coupled four-wheel drive mode, for example, 50%: 5
The main drive wheel: the sub drive wheel = 100%: 0 is set to 0% by selecting the two-wheel drive mode, and the control signal corresponding to the set value is output to the transmission torque variable adjustment means to be the control signal. Accordingly, the driving force from the engine is distributed to the main and auxiliary drive wheels. Therefore, in order to prevent the direct-drive four-wheel drive state when the different-diameter wheel is mounted as described above, a different-diameter wheel mounting determination means for detecting the different-diameter wheel mounting state is provided, and the different-diameter wheel mounting determination means is used. When the state is determined, the driving force distribution of the main and auxiliary drive wheels is set to a value other than 1: 1.

Further, in a vehicle that is not in the direct four-wheel drive state, if the wheels with different diameters are mounted, the difference in rotational speed between the front and rear wheels becomes large. I thought I could do it. However, when the vehicle is turning or when the braking force or the driving force is applied to the wheels, the rotational speed difference between the front and rear wheels becomes large even if the wheels with different diameters are not mounted. It is more accurate when the judgment is made. Further, when the vehicle with the different-diameter wheels mounted starts to move in the direct-coupled four-wheel drive state by selecting the changeover switch or the like, the difference in rotational speed between the front and rear wheels does not occur. Therefore, in such a case, when determining whether the different-diameter wheel is mounted based on the difference in rotational speed between the front and rear wheels, the drive force distribution between the main and auxiliary drive wheels is changed to one in which the main drive wheel is larger than the auxiliary drive wheel. Then, it is necessary to determine whether the different-diameter wheels are mounted after the main driving wheels and the sub driving wheels are allowed to rotate at different speeds.

A four-wheel drive control system for a vehicle according to a first aspect of the present invention based on such knowledge, as shown in the basic configuration diagram of FIG. 1, uses one of the front and rear wheels of the vehicle as a main drive wheel and the other As a sub-driving wheel, a driving force distribution adjusting unit that distributes the driving force from the engine to the main driving wheel and the sub-driving wheel according to a control signal, and a driving mode detecting unit that detects the selected driving mode, A drive that sets the driving force distribution between the main and auxiliary drive wheels based on at least the driving mode detection value from the driving mode detection unit, and outputs a control signal according to the set value to the driving force distribution adjustment unit. In a four-wheel drive control device for a vehicle, which includes a force distribution control means, it is determined whether or not at least one wheel of all wheels mounted on the vehicle has a different diameter wheel mounting state that is different from the diameters of the other wheels. Different diameter wheels In addition to the arrival determination means, the drive force distribution control means sets the drive force distribution between the main and auxiliary drive wheels to not 1: 1 based on the different diameter wheel attachment detection value from the different diameter wheel attachment determination means. It is characterized in that it is provided with a directly connected four-wheel drive state prohibiting means for setting.

A four-wheel drive control system for a vehicle according to a second aspect of the present invention is the four-wheel drive control system for a vehicle according to the first aspect, wherein the different-diameter wheel mounting determining means is the main drive wheel and the sub drive. It is characterized in that the different-diameter wheel mounting state for the vehicle is judged based on the difference in rotational speed between the front and rear wheels corresponding to the wheels. Further, claim 3
As shown in the basic configuration diagram of FIG. 2, the four-wheel drive control system for a vehicle according to claim 2 is the four-wheel drive control system for a vehicle according to claim 2, wherein the drive force distribution adjusting means is provided between the main and sub drive wheels. A direct connection four-wheel drive state detecting means for detecting a direct-connection four-wheel drive state in which the driving force distribution state is 1: 1 is provided, and
The driving force distribution control means, when the direct connection four-wheel drive state is detected by the direct connection four-wheel drive state detecting means,
A driving force distribution changing unit that changes the driving force distribution between the main and auxiliary driving wheels to one in which the main driving wheels are larger than the auxiliary driving wheels, and that outputs a control signal according to the changed value to the driving force distribution adjusting unit; The different-diameter wheel mounting determination means determines the different-diameter wheel mounting state on the vehicle after the driving force distribution is changed by the driving force distribution changing means.

[0012]

In the four-wheel drive control system for a vehicle according to claim 1,
As shown in the basic configuration diagram of FIG. 1, in a four-wheel drive vehicle in which one of the front and rear wheels of the vehicle is the main drive wheel and the other is the auxiliary drive wheel, the drive force distribution adjusting means such as the variable torque clutch is used. In accordance with a control signal from the driving force distribution control means, the driving force from the engine is distributed to the main driving wheels and the auxiliary driving wheels. Since the control signal corresponds to the driving force distribution set on the basis of at least the driving mode detection value from the driving mode detecting means, in the normal time, the When the automatic four-wheel drive mode is selected, for example, the value depends on the front-rear wheel rotation speed difference, when the direct-coupled four-wheel drive mode is selected, for example, 50%: 50%, and when the two-wheel drive mode is selected, the main drive wheel: the auxiliary drive wheel = The driving force is distributed at 100%: 0.

However, when the vehicle is equipped with the different-diameter wheels, this is detected by the different-diameter wheel attachment determining means for determining the different-diameter wheel attachment state (specifically, for example, as in claim 2). On the basis of the rotational speed difference between the main and auxiliary drive wheels, for example, when the rotational speed difference is larger than a predetermined value for a predetermined time or more, it is determined that the wheels with different diameters are mounted, and the drive is performed. In the direct connection four-wheel drive state prohibiting means of the force distribution control means, the driving force distribution between the main and auxiliary driving wheels is set to not 1: 1 and a control signal according to the set value is output to the driving force distribution adjusting means. . for that reason,
Even when the direct-coupled four-wheel drive mode is selected, or when the driving force distribution according to the front-rear wheel rotation speed difference and the like when the full-time four-wheel drive vehicle and the automatic four-wheel drive mode are selected is 1: 1. However, main drive wheel: sub drive wheel = 50%: 50%
It is prohibited that the driving force is distributed to other than the above, and the direct connection four-wheel drive state is set (that is, the transition to the direct connection four-wheel drive state or the continuation of the direct connection four-wheel drive state).

As a result, the directly connected four-wheel drive state is not achieved when the wheels with different diameters are mounted, so that wheels with smaller diameters are allowed to rotate faster than wheels with larger diameters when the wheels with different diameters are mounted. Further, in the four-wheel drive control system for a vehicle according to the third aspect, particularly, the different-diameter wheel mounting determination means is made based on the rotational speed difference between the main and auxiliary drive wheels, and the four-wheel drive state is directly connected. It is applied when the vehicle starts in.

Further, in this device, as shown in the basic configuration diagram of FIG. 2, the direct connection four-wheel drive state detecting means makes the drive force distribution state between the main and auxiliary drive wheels by the drive force distribution adjusting means 1: 1. When the direct drive four-wheel drive state in is detected, in the driving force distribution changing means of the driving force distribution control means,
The driving force distribution between the main and auxiliary driving wheels is changed so that the main driving wheels are larger than the auxiliary driving wheels, and a control signal according to the changed value is output to the driving force distribution adjusting means. As a result, the vehicle is shifted to a drive state that is not direct four-wheel drive (for example, an automatic four-wheel drive state in which the drive force distribution state between the main and sub drive wheels is not 1: 1), and the main drive wheel and the sub drive wheels are separated. Since rotation at a speed of 5 is allowed, if a wheel with a different diameter is mounted, for example, the state in which the difference in rotation speed is larger than a predetermined value continues for a predetermined time or longer. Therefore, after changing the driving force distribution by the driving force distribution changing means,
The different-diameter wheel mounting determination means shown in FIG. 2 can determine whether the different-diameter wheel is mounted, for example, as described above, based on the rotational speed difference between the main and auxiliary driving wheels.

Further, as in the case of claim 1, in the direct connection four-wheel drive state prohibiting means of the driving force distribution control means, the driving force distribution between the main and auxiliary driving wheels is not set to 1: 1. A control signal according to the set value is output to the driving force distribution adjusting means. Therefore, the direct drive four-wheel drive mode was selected when the vehicle started, so the main drive wheel: the sub drive wheel = 50
%: Even if the driving force distribution is 50%, continuation of the direct-coupled four-wheel drive state is prohibited and main driving wheels: sub-driving wheels = 50% if different-diameter wheels are installed. : 50
The driving force is distributed to other than%. This allows a wheel with a smaller diameter to rotate at a faster speed than a wheel with a larger diameter when the wheels with different diameters are mounted.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a four-wheel drive control system for a vehicle according to the present invention will be described below with reference to the accompanying drawings. FIG.
It is a schematic block diagram which shows the four-wheel drive control system of the vehicle which concerns on this Example. The device of this embodiment is a four-wheel drive vehicle based on the FR (front engine / rear drive) system, and the driving force distribution is as follows: main drive wheel (rear wheel): auxiliary drive wheel (front wheel) = 100%: Two-wheel drive mode fixed at 0,
Auto four-wheel drive mode in which the driving force distribution is automatically set to a value according to the front-rear wheel rotation speed difference, and direct connection four in which the driving force distribution is fixed to main driving wheels: sub driving wheels = 50%: 50% The wheel drive mode can be selected by operating a changeover switch (not shown), and a sub transmission is provided so that the shift position of the sub transmission can be selected by operating a lever (not shown).

As can be seen from FIG. 3, the four-wheel drive control system for a vehicle in this embodiment is a rotary drive source, that is, an engine 10 as an engine, and front left wheel to rear right wheel 12F.
A drive force transmission system 14 capable of changing and controlling a drive force distribution ratio to L to 12RR, and a drive force distribution control device 15 controlling the drive force distribution by the drive force transmission system 14 are provided. The driving force transmission system 14 shifts the driving force from the engine 10 at a selected gear ratio, and the driving force from the transmission 20 to the front wheels 12FL, 12FR and the rear wheels 12R.
The transfer 22 is divided into L and 12RR. Then, in the driving force transmission system 14, the front wheel side driving force divided by the transfer 14 is applied to the front wheel side output shaft 2
4, front wheels 12FL, 12FR via front differential gear 26 and front wheel side drive shaft 28
On the other hand, the rear wheel side driving force is transmitted to the propeller shaft (rear wheel side output shaft) 30, the rear differential gear 3
2 and the rear wheel side drive shaft 34, the rear wheel 12
It is transmitted to RL and 12RR. Therefore, the FR of this embodiment
In the base four-wheel drive vehicle, the rear wheels 12RL and 12RR serve as the main driving wheels, and the front wheels 12FL and 12FR serve as the sub driving wheels. Of course, the transmission 20 may be an automatic transmission.

FIG. 4 shows the internal structure of the transfer 22. As can be seen from FIG. 4, the input shaft 42 and the first output shaft 44 which are coaxially butted in the transfer casing 40. The input shaft 42 has a radial bearing 46 on the front casing 40a.
The first output shaft 44 is rotatably supported by the rear casing 40b and is rotatably supported by the rear casing 40b via a radial bearing 48 so as to be relatively rotatable. The second output shaft 54 is rotatably supported in parallel with the input shaft 42 and the first output shaft 44 through bearings 50 and 52 arranged in the front casing 40a and the rear casing 44b, respectively. There is. The input shaft 4
2 is connected to the output shaft 56 of the transmission 20, and the first output shaft 44
Is connected to the rear wheel side output shaft 30, and the second output shaft 54 is connected to the front wheel side output shaft 24.

The input shaft 42 and the first output shaft 44 have an auxiliary transmission mechanism 58 and a variable torque distribution mechanism (two-wheel drive mechanism) for switching between two-wheel drive and four-wheel drive to adjust the transmission torque to the front wheels. And a four-wheel drive switching mechanism) 60. The sub-transmission mechanism 58 includes a planetary gear mechanism 62 and a meshing clutch type high / low speed switching mechanism 64 coaxially arranged on the planetary gear mechanism 62.

The planetary gear mechanism 62 includes a sun gear 62a formed on the outer periphery of the input shaft 42 and a front casing 40.
It is composed of an internal gear 62b fixed inside a, a pinion gear 62c that meshes with the sun gear 62a and the internal gear 62b, and a pinion carrier 62d that rotatably supports the pinion gear 62c.

The high / low speed switching mechanism 64 includes a plurality of key grooves and inner teeth 64b provided on the outer circumference of the first output shaft 44.
_It is formed at the outer peripheral position of the input shaft 42 which is slidable in the axial direction by spline connection with ₁ and has a shift sleeve 64b having outer teeth 64b ₂ on its outer periphery and an inner tooth 64b ₁ of the shift sleeve 64b. High speed shift gear 64c and the outer teeth 64b _{2 of the} shift sleeve 64b.
And a low speed shift gear 64d formed on the inner peripheral portion of the pinion carrier 62d that can be meshed with.

FIG. 5 is an enlarged view of the portion relating to the high / low speed switching mechanism 64 in FIG. 4, and according to the high / low speed switching mechanism 64, as shown by the solid line in the upper half sectional view of FIG. When the shift sleeve 64b to the high-speed shift position symbol H is slid, the internal teeth 64b ₁ of the shift sleeve 64b is adapted to the gear 64c meshes with the high-speed shift. Further, as shown in the lower half sectional view of FIG. 5, when the shift sleeve 64b slides to the low speed shift position indicated by the symbol L, the outer teeth 64b ₂ of the shift sleeve 64b come into mesh with the low speed shift gear 64d. ing. Further, as indicated by the chain double-dashed line in the upper half sectional view of FIG. 5, when the shift sleeve 64b moves to the neutral position of the symbol N, the shift sleeve 64b
The inner teeth 64b ₁ and the outer teeth 64b ₂ are designed not to mesh with any gear.

Returning to FIG. 4, the torque distribution changing mechanism 6 is described.
0 is a wet multi-plate friction clutch (hereinafter, simply referred to as “friction clutch” or simply “clutch”) 66 that changes the driving force distribution ratio for the front and rear wheels according to the supplied hydraulic pressure.
A first sprocket 68 rotatably arranged on the first output shaft 44, and a second sprocket coaxially connected to the second output shaft 54.
A sprocket 70 and first and second sprockets 60,
It is composed of a chain 72 wound between 70.

The friction clutch 66 includes the first sprocket 6
8, a clutch drum 66a coupled to the clutch drum 66a, a friction plate 66b splined to the clutch drum 66a, a clutch hub 66c splined to the outer circumference of the first input shaft 44, and a clutch hub 66c integrally coupled to the clutch hub 66c. The friction disc 66d disposed between the friction plates 66b and the first output shaft 44
A rotary member 66e disposed on the outer circumference of the clutch plate 66b for abutting the friction plate 66b and the friction disc 66d by axial movement toward the clutch drum 66a side; An engaging pin 66k, a clutch piston 66g mounted on the inner wall of the rear casing 40b and movable in the axial direction, and a thrust bearing 66f for transmitting the axial movement of the clutch piston 66g to the rotating member 66e. , A cylinder chamber 66h formed between the inner walls of the clutch piston 66g and the rear casing 40b
And a return spring 66j that applies an urging force to the rotating member 66e toward the clutch piston 66g.

When the clutch pressure P _C is supplied to the input port 74 formed in the rear casing 40b that communicates with the cylinder chamber 66h from the hydraulic pressure supply device 16 described later, the clutch pressure is generated in the cylinder chamber 66h to generate the clutch pressure. The piston 66g moves to the left side in FIG. 4, the movement of the clutch piston 66g is transmitted to the rotating member 66e via the thrust bearing 66f, and the friction plate 66b and the friction disc 66d, which are separated from each other, move to the friction disc 66d. The contact is caused by the movement, and the fastening force corresponding to the clutch pressure Pc due to the frictional force is applied. As a result, the rotational driving force of the first output shaft 44 has a predetermined torque distribution ratio according to the engagement force of the friction clutch 66, and the first sprocket 68, the chain 72, and the second sprocket 7
It is adapted to be transmitted to the second output shaft 54 via 0.

Further, when the supplied clutch pressure Pc decreases and the urging force of the return spring 66j moves the rotating member 66e and the clutch piston 66g to the right side in FIG. 4, the friction plate 66b and the friction disc 66d are separated from each other. The rotational driving force of the first output shaft 44 is not transmitted to the second output shaft 54. Further, the first sprocket 68, the four-wheel drive gear 80 on the outer circumference of the shift sleeve 64b side is provided, the shift sleeve 64d to the low speed position L in Fig. 5 described above is moved, the external teeth 64b ₂ and slow The structure is such that the four-wheel drive gear 80 meshes with the internal teeth 64b _{1 as} well as meshes with the shift gear 64d. As a result, the shift sleeve 64b
Also, the four-wheel drive gear 80 moves the first output shaft 4 at the low speed position L.
4 and the second output shaft 54 are compulsorily coupled to each other to form a dog clutch. That is, when the low speed position L is selected by the transmission lever, the torque is always distributed to the front wheels to drive four wheels.

The shift sleeve 64b of the high / low speed switching mechanism 64 of the meshing clutch type has a fork (Fig. 4) manually operated by an auxiliary transmission lever (not shown).
Reference numeral 84 indicates a slide movement to the high speed shift position H, the neutral position N or the low speed shift position L via the fork end portion). Here, inside the front casing 40a, a high speed shift position sensor 86 that detects that the shift sleeve 64b has slid to the high speed shift position H, and a low speed that detects that the shift sleeve 64b has slid to the low speed shift position L. A shift position sensor 88 is provided. The detection signal S _H of the high speed shift position sensor 86 and the detection signal S _L of the low speed shift position sensor 88 are input to the controller 18, which will be described later, at any time.

FIG. 6 is a block diagram showing a circuit configuration of the hydraulic pressure supply device 16 for controlling the operation of the friction clutch 66. The hydraulic pressure supply device 16 is a forward / reverse rotation type main pump 100 that is directly connected to an input shaft 56 that is connected to an output side of the transmission 20 and is rotationally driven, and the main pump 100.
A forward rotation type sub-pump 104, which is arranged in parallel with and is rotationally driven by the electric motor 102 as a power source, is used as a hydraulic source. These main pump 100 and sub pump 104
The strainer 106 from the hydraulic oil in the oil tank 105.
a, 108a, and the discharge side pipe 106b,
Discharge to 108b. The oil element 11 is connected to the converging pipe 110a that converges the pipes 106b and 108b.
2 is connected, and a relief passage 116 having the other end connected to the lubrication system 114 side is connected to the upstream side (main pump 100 and sub pump 104 side) of the oil element 112. Further, a line pressure regulating valve 118 is connected to the downstream side (transfer 22 side) of the oil element 112, and pipes 110b, 1b branching from the converging pipe 110a.
The input sides of the electromagnetic switching valve 120, the clutch pressure adjusting valve 122, and the pressure reducing valve 124 are connected to 10c and 110e, respectively. The output side of the clutch pressure adjusting valve 122 is connected to the input side of a pilot switching valve 126 that supplies the clutch pressure Pc to the transfer 22 when the pilot pressure from the electromagnetic switching valve 120 is supplied, and the output of the pressure reducing valve 124. The input side of the duty control solenoid valve 128 is connected to the side.

A temperature sensor 130 for detecting the temperature of the hydraulic oil is provided in the oil tank 105, and a predetermined value is set when the hydraulic pressure reduced by the line pressure regulating valve 118 is a treatment value A ₂ or more. A hydraulic switch 132 that outputs a hydraulic pressure detection signal S _A2 and a hydraulic switch 134 that outputs a predetermined hydraulic pressure detection signal S _A3 when the clutch pressure Pc output from the switching valve 126 is a predetermined value A ₃ or more are provided. These detection signals are output to the controller 18, which will be described later. And this hydraulic pressure supply device 1
6 is arranged inside the transfer 22 in an actual vehicle. The main pump 100 that sucks the hydraulic oil from the oil tank 105 is, as shown in FIG.
The sub pump 104 is connected to the first output shaft 44 via the gear 136 a and the second gear 136 b, and is connected to the electric motor 102 externally attached to the transfer casing 40.

Next, the detailed structure and operation of each of the components of the hydraulic pressure supply device 16 will be described mainly based on the block diagram of FIG. Main pump 1 for normal rotation drive
00 sucks hydraulic oil from the oil tank 105 through the strainer 106a connected to the end of the suction pipe 106c, and the sub pump 104 also passes through the strainer 108a connected to the end of the suction pipe 108c.
Suction hydraulic oil from 05. Then, the converging pipe 110a
Check valves 106d and 108d are inserted in the discharge pipes 106b and 108b of the respective pumps connected to the pump, and a bypass passage 140 is provided between the discharge pipe 106b of the main pump 100 and the suction pipe 108c of the sub pump 104. Are connected. The bypass passage 140 is composed of a bypass pipe 140a and three check valves 140b inserted in the bypass pipe 140a. When the discharge pipe 160b is in a negative pressure state, the check valve 140b opens. Then, the working oil becomes a communication passage through which the hydraulic oil flows in the direction of the broken line arrow.

The relief passage 116 connected to the convergent pipe 110a upstream of the oil element 112 has a relief pipe 116a whose other end is connected to the lubricating system 114 side.
The relief pipe 116a is composed of two check valves 116b with springs. Then, when the filter of the oil element 112 is clogged and the pressure on the upstream side of the oil element 112 becomes equal to or higher than a predetermined pressure, the check valve 116b is opened, and the hydraulic fluid flows in the direction of the dashed arrow. Become.

The line pressure regulating valve 118 is constituted by an internal pilot and pressure reducing valve of the spring type, an input port 118 _A to connect to the convergence pipe 110a side, the lubrication system 11
A spool is slidably arranged in a tubular valve housing having internal pilot ports 118 _P1 and 118 _P2 to which primary pressure and secondary pressure are supplied via an output port 118 _B connected to the four side and a fixed throttle. A return spring 118a for urging the spool toward one end is provided. Then, the main pump 100 or the sub pump 1
The supply pressure P _L increased by 04 is the line pressure regulating valve 118.
The pressure is reduced to a predetermined pressure and supplied to the electromagnetic switching valve 120, the clutch pressure adjusting valve 122, and the pressure reducing valve 124. The hydraulic oil flowing out from the output port 118 _B when the pressure reduction is set is returned to the lubricating system 114.

The clutch pressure adjusting valve 122 is composed of an internal pilot valve, an external pilot valve, and a spring type pressure regulating valve, and is connected to the pipe 110c in the input port 1.
22 _A , an output port 122 _B connected to the pilot switching valve 126, an internal pilot port 122 _P1 to which the secondary pressure is supplied as a pilot pressure via a fixed throttle, and an external pilot port to which the control pressure is supplied from the duty control valve 128. A spool is slidably disposed in a tubular valve housing having 122 _P2, and a return spring 122a that biases the spool toward one end is disposed. The clutch pressure adjusting valve 122 is the duty control valve 12
When the pilot control pressure from 8 is not supplied, the communication passage between the input port 122 _A and the output port 122 _B is closed and the secondary pressure is not output. Further, when the pilot control pressure from duty control valve 128 is supplied, spool secondary pressure corresponding to the pilot control pressure from the output port 122 _B is movement control is output as the clutch pressure Pc.

The pressure reducing valve 124 is an internal pilot and
It is composed of a ring type constant secondary pressure type pressure reducing valve.
Input port 124 that connects to the pipe 110e_A, Du
Output port 124 connected to the control valve 128_BOut
Force port 124_BSecondary pressure from the pie
Internal pilot port 124 supplied as lot pressure
_PAnd the drain port 124_HCylindrical valve howe with
The spool is slidably installed in the housing,
The return spring 124a that biases the
It is set up. And the internal pilot port 124_P
The spool is set in position by the pilot pressure supplied to
Is controlled to move to the input port 124_AFrom
The supplied primary pressure is the control pressure that has been adjusted to a predetermined pressure.
And then supplied to the duty control valve 128.
There is.

Further, the duty control valve 128 is arranged at the position of 3 ports and 2 positions, and the input port 128 _A connected to the pressure reducing valve 124 side, the drain port 128 _D connected to the drain side, and the clutch pressure adjusting valve 122. Output port 128 to connect with external pilot port 122 _P2
And _B, and a return spring 127a, a normal position 128b spool disposed within the valve causes communication between the output port 128 _B and the drain port 128 _D,
The input port 128 _A and the output port 128 _B is a valve which is controlled to move the operating position 128c to communicate. Then, when the exciting current i ₀ having a required duty ratio is supplied from the controller 18 to the solenoid 128 d, the section return spring 128 in which the exciting current i ₀ is in the ON state.
Normal position 128b to working position 128c against a
By controlling the movement of the spool, the pilot control pressure according to the duty ratio is output to the clutch adjustment valve 122. Therefore, when the pilot control pressure is supplied to the external pilot port 122 _P2 from the duty control solenoid valve 128, the clutch pressure adjusting valve 122 outputs the clutch pressure Pc corresponding to the pilot control pressure, and accordingly, the friction clutch. The clutch engagement force of 66 is controlled to distribute the drive torque to the front wheels according to the clutch pressure P _C.

Further, the spring offset type solenoid operated directional control valve 120 is arranged at the position of 3 ports and 2 ports, and the input port 120 _A to which the line pressure is supplied and the pilot directional control valve 12 are provided.
6 has an output port 120 _B connected to the external pilot port 126 _P1 and a drain port 120 _D connected to the drain side, and the spool disposed inside the valve blocks the input port 120 _A and the output port. Normal position 120b for communicating 120 _B with the drain port 120 _D
And an operating position 1 in which the input port 120 _A and the output port 120 _B communicate with each other and the drain port 120 _D shuts off.
20c is a valve whose movement is controlled. When the controller 18 outputs the exciting current i ₁ to the solenoid 120d, the electromagnetic switching valve 120 receives the exciting current i _1.
Return spring 120 while the
The spool is controlled to move against the position a, and the operating position is 120c.
Therefore, the pilot control pressure is supplied to the external pilot port 126 _P1 of the pilot switching valve 126. When the exciting current i ₁ from the controller 18 is turned off, it is returned to the normal position 120b by the pressing force of the return spring 120a, and the external pilot port 12
The pilot control pressure supplied to 6 _P1 is extinguished through the drain port 120 _D.

FIG. 7 is a sectional view showing the state of the pilot switching valve 126 in the two-wheel drive mode and the four-wheel drive mode. As can be seen from FIG. 7, the pilot switching valve 126 includes an input port 126 _A to which the secondary pressure is supplied from the clutch pressure regulating valve 122, an output port 126 _B to supply the secondary pressure to the transfer 22, and an electromagnetic switching valve. external pilot port 126 _P1 which 120 of the solenoid 120d is controlled pressure is supplied when in the energized state, into the cylindrical valve housing 126i having a drain port 126 _H, spool 126e is disposed slidably, this Spool 1
Return spring 126a for urging 26e toward one end
Is a valve provided with. The control pressure from the external pilot port 126 _P1 is applied to the return spring 126
It is supplied in the same direction as the pressing force of a.

Then, the pilot switching valve 126
The pool 126e is the external pilot port 126._P1To
If the pilot control pressure is not supplied, input port 1
26 _AAnd output port 126_BAre cut off, and the output
Heart 126_BIs the drain port 126_D2W communicating with
The movement is controlled to the D mode position 126b.
(Left half cross-sectional state in FIG. 7). Further, the electromagnetic switching valve 120
Of the solenoid 120d is turned on.
And the spool 120a is controlled to move to the operating position 120c.
External pilot port 126_P1To pilot control pressure
Is supplied to the input port 126_AAnd output port 126_B
Is controlled to move to the 4WD mode position 126c where
(The right half cross-sectional state of FIG. 7).

As described above, by driving the pilot switching valve 126 with the pilot control pressure from the electromagnetic switching valve 120, the spool 126e can be driven with a high pilot control pressure, and the sliding passage of the spool 126e is dusted. Even when chips or the like are attached and the sliding resistance of the spool 126e is high, the sliding of the spool 126e can be ensured.

Here, FIG. 8 shows the solenoid 128d of the duty control valve 128 in the hydraulic pressure supply device 16.
The duty ratio D of the exciting current i ₀ supplied to the friction clutch 66 and the pressure supplied to the friction clutch 66 (corresponding to the “clutch pressure Pc”).
FIG. 9 is a characteristic diagram showing the correlation with, and as can be seen from FIG. 8, the clutch pressure Pc that increases parabolically in accordance with the increase of the duty ratio D is output from the pilot switching valve 126 to the friction clutch 66. Then, a predetermined frictional force is generated between the friction plate 66b and the friction disc 66d according to the clutch pressure Pc supplied from the hydraulic pressure supply device 16 to the friction clutch 66, and the engagement force due to the generated frictional force is generated. Thus, the driving torque is distributed and transmitted to the rear wheel side and the front wheel side.

Here, FIG. 9 is a characteristic diagram showing the correlation between the supply pressure Pc to the friction clutch 66 and the transmission torque ΔT to the front wheels. As can be seen from FIG. 9, the transmission torque to the front wheels is shown. ΔT linearly changes according to the supply pressure (corresponding to the “clutch pressure”) Pc to the friction clutch 66. That is, in this transfer 22, the distribution ratio of the torque to the front and rear wheels is (0: 100 to 50 :) depending on the duty ratio D of the exciting current i _0.
(Up to 50) can be changed continuously, specifically the duty ratio D
_{When the} clutch pressure P ₁ is supplied at _1, 0: 100
%, And the clutch pressure P ₂ is supplied at the duty ratio D ₂ , resulting in 50%: 50%. When the duty ratio is D ₁ or less, the friction plate 66b of the friction clutch 66 is driven by the clutch pressure P ₁ or less.
And the friction disc 66d are in pressure contact with each other,
The driving force is not transmitted to the front wheels.

On the other hand, returning to FIG. 3, the driving force distribution control is performed.
The device 15 includes a front wheel side rotation sensor 17F and a rear wheel side rotation sensor.
The sensor 17R and these rotation sensors 17F and 17R
A rotary sensor that outputs an alarm signal when it is not operating normally.
Sensor alarm switch 19 and the changeover switch
Drive mode switch 21 for detecting the selected drive mode
Is supplied to the clutch 66 from the hydraulic pressure supply device 16.
Where the clutch supply pressure Pc is equivalent to direct drive four-wheel drive
Fixed value A₁When the above is the case, the predetermined hydraulic pressure detection signal S _A1Output
Hydraulic switch 23 and the high-speed shift position sensor described above
86 and the slow shift position sensor 88 and their sensors.
To the hydraulic pressure supply device 16 based on the detection signal from the
The exciting current i₀, I₁And the controller 18 that outputs
I have it. In this example, the same controller
18, the hydraulic pressure supply device 16 can maintain a predetermined hydraulic pressure.
It is also designed to control the performance, so that
Necessary for the oil temperature sensor 130 and the hydraulic switch 13
2 and 134 are installed, and detection from these sensors is performed.
Motor control signal S based on output signal_MController 18
Output to the hydraulic supply device 16 from
It

Further, as can be seen from FIG. 3, in the vehicle of this embodiment, the indicator for indicating to the driver the drive state currently being performed by the selection of the changeover switch or the result of the control by the control device. 25, and an alarm device 27 that indicates, as a result of the control by the control device, that the determination of prohibition of the directly connected four-wheel drive state is made by blinking a lamp or sound. Further, an alarm device 29 is provided to alert the driver by flashing a lamp or making a sound when the predetermined hydraulic pressure is not maintained even by the hydraulic control based on the oil temperature sensor 130 and the hydraulic switches 132 and 134.

The front wheel side rotation sensor 17F and the rear wheel side rotation sensor 17R are individually provided at predetermined positions of the front wheel side output shaft 16 and the rear wheel side propeller shaft 22, and the rotation speed of each axis is determined by an optical system or It is configured to be detected by an electromagnetic method, and the peripheral speed of the wheel, that is, the wheel speed, is individually output to the controller 18 as front and rear wheel rotation detection values nF and nR by a pulse signal or a sine wave signal corresponding thereto. . Here, as the front wheel side rotation sensor 17F and the rear wheel side rotation sensor 17R, for example, those described in Japanese Patent Application Laid-Open No. 1-195126 previously proposed by the present applicant can be diverted.

The drive mode switch 21 outputs the drive mode M selected by the changeover switch. If the selected drive mode is the two-wheel drive mode, M = 2, and if it is the automatic four-wheel drive mode. M = AUTO
4. In the direct drive four-wheel drive mode, a signal indicating M = LOCK4 is output. FIG. 10 shows the controller 18 in detail. As can be seen from FIG.
The controller 18 controls the hydraulic pressure in response to a microcomputer 7 for performing the driving force distribution control, a microcomputer 8 for performing the above-described predetermined hydraulic pressure holding control, and a control signal CS ₀ from the microcomputer 7. The solenoid 128d of the duty ratio control valve 128 in the supply device 16 is turned on / off in response to a drive circuit 31a for supplying an exciting current i ₀ having a required duty ratio D and a control signal CS ₁ from the microcomputer 7. The electric motor 102 of the hydraulic pressure supply device 16 is responsive to the drive circuit 31b that supplies the current i ₁ to the solenoid 120d of the electromagnetic switching valve 120 in the hydraulic pressure supply device 16 and the motor control signal S _M from the microcomputer 8. The chopper control of the electric motor 1
Motor drive circuit 103 for controlling the speed of 02 to a speed according to the motor control signal S _M.

The microcomputer 7 has an input interface circuit 7a having an A / D conversion function for reading the detection signals from the sensors 19, 17F, 17R, 21, 23, 86 and 88 as respective detection values, and a predetermined circuit. Arithmetic processing unit 7b for performing arithmetic operation / control processing for driving force distribution control in accordance with the program, and ROM, RAM
A storage device 7c such as the above, and a front wheel side torque distribution command value T ₂ obtained by the arithmetic processing unit 7b, and a control signal CS for achieving a clutch pressure P _C according to the front wheel side torque distribution command value T _{2. And} an output interface circuit 7d having a D / A conversion function for outputting a control signal CS ₁ indicating whether or not to output the clutch pressure P _C. That is, the control signal CS ₁ is output when the front wheel side torque distribution command value T ₂ obtained by the arithmetic processing unit 7b is not "0", and the front wheel side torque distribution command obtained by the arithmetic processing unit 7b is output. If the value T ₂ is "0" or the front wheel side torque distribution command value T ₂ is not output, it is not output.

In addition, the exciting current i ₀ supplied to the solenoid 128d of the duty control valve 128 shown in FIG. 8 described above.
Characteristic diagram showing the correlation between the duty ratio D and the supply pressure to the friction clutch 66 (corresponding to the "clutch pressure Pc"),
A table corresponding to the characteristic diagram showing the correlation between the supply pressure Pc to the friction clutch 66 and the transmission torque ΔT to the front wheels shown in FIG. 9 is stored in the storage device 7c as fixed data. Thus, the front wheels side torque distribution command value T ₂ obtained by the arithmetic processing unit 7b, in the output interface circuit 7d, are converted to transmission torque ΔT to the front wheel side in accordance with the front wheel torque distribution command value T _2, the The transmission torque ΔT to the front wheels is based on the characteristic of FIG.
The clutch pressure P _C is converted into _C , and the clutch pressure P _C is converted into the duty ratio D based on the characteristic of FIG. 8, and the control signal CS ₀ indicating the duty ratio D is output to the drive circuit 31a.

Further, the microcomputer 8 has an input interface circuit 8a having an A / D conversion function for reading the detection signals from the sensors 130, 132 and 134 as respective detection values, an arithmetic processing unit 8b, and an RO.
Storage device 8c such as M and RAM, and the arithmetic processing device 8b
The output interface circuit 8d having a D / A conversion function for outputting the electric motor rotation speed command value M ₂ obtained in step 1) as, for example, an analog voltage signal S _M.

Then, in the microcomputer 7 of the controller 18, FIGS. 14 and 15 which will be described later in detail.
The rotation sensor alarm switch 19
Detection signals S _FF and S _FR from the front wheel rotation detection value nF from the front wheel rotation sensor 17F, the rear wheel rotation sensor 1
Rear wheel rotation detection value nR from 7R, drive mode switch 6
Drive mode detection value M (2, AUTO4, or LOCK4) from 0, detection signal S from the hydraulic switch 23
_The front wheel torque distribution command value T ₂ is set and set based on A ₁ , the high speed shift position detection signal S _H from the high speed shift position sensor 86, and the low speed shift position detection signal S _L from the low speed shift position sensor 88. The control signals CS ₀ and CS ₁ according to the front wheel side torque distribution command value T ₂ are output to the drive circuits 31a and 31b, and the direct connection four-wheel drive state prohibition signal S _N is output to the alarm device 27. At the same time, the drive state signal S _K indicating the drive state currently being performed is output to the indicator 25.

Then, the drive circuit 31a converts the control signal CS ₀ , which is an analog signal output from the microcomputer 7, into an exciting current having a duty ratio D indicated by the control signal CS ₀ and outputs the exciting current, for example. The pulse width modulation circuit is provided, and the exciting current i ₀ having the duty ratio D corresponding to the front wheel side torque distribution command value T ₂ is output to the solenoid 128d of the duty control solenoid valve 128.

Further, the drive circuit 31b is the microphone.
Control signal CS output from computer 7₁The electric
Current that can excite the solenoid 120d of the magnetic switching valve 120
Value I _KExciting current i₁And convert this into the solenoid operated directional control valve 1
It outputs to the solenoid 120d of 20. Where this fruit
The microcomputer 8 of the controller 18 of the embodiment is used.
That is, the calculation process, that is, the hydraulic pressure supply device 16,
The control for enabling the supply of pressure is, for example, not shown.
With the hydraulic calculation 132, the convergent piping 1
Line pressure P on the downstream side of the oil element 112 of 10a
_LWhen it is detected that is below the set value,
To control the discharge pressure (oil amount) from the sub-pump 104
The oil temperature detection value S from the oil temperature sensor 130_YAccording to
Control signal S indicating the rotational speed command value set by_MCalculate
By supplying this to the motor drive circuit 103.
Control the rotation speed of the electric motor 102 to supply hydraulic pressure.
Line pressure P output from device 16_LMaintained at the specified pressure
To do. Also, along with this, for example,
The line pressure from the switch 132 is the set hydraulic pressure A₂Is over
Detection signal S that informs that_A2Is not output,
Alternatively, the line pressure is set from the hydraulic switch 134 to the hydraulic pressure A.₃
Detection signal S notifying that the above has been reached_A3Is output
If not, the control pulse signal S_MBy electric moo
From the sub pump 104
Control to increase the discharge pressure (oil amount) is performed.
The detection signal S_A2, S_A3Is output
If not, determine that an abnormality has occurred in the hydraulic pressure supply device 16.
An alarm detection signal S is sent to the alarm device 29._UOutput the lamp
For example, blinking or sounding calls attention to the driver.

Next, the basic principle of the arithmetic processing performed by the microcomputer 7 of the controller 18 of this embodiment, that is, the driving force distribution control will be described. In this embodiment, as described above, the two-wheel drive mode, the automatic four-wheel drive mode, the three-stage switching of the direct four-wheel drive mode is possible by operating the switch, the drive force distribution in each drive mode, Normally, when the two-wheel drive mode is selected, the rear wheels: front wheels = 100%: 0 are fixed, and when the automatic four-wheel drive mode is selected, the value is automatically set to a value according to the front and rear wheel rotation speed difference. When the four-wheel drive mode is selected, the rear wheels are fixed to the front wheels = 50%: 50%.

Specifically, when the automatic four-wheel drive mode is selected
Is the rotational speed difference ΔV between the front and rear wheels._WAfter the main drive wheel
Average rear wheel speed obtained from the average rotational speed of the wheels 2RL, 2RR
Degree (rear wheel rotation detection value nR), the front wheel 2 that is the auxiliary drive wheel
Average front wheel speed obtained from average rotational speeds of FL and FR (front
The wheel rotation detection value nF) is subtracted, and based on the equation (1),
Calculate, ΔV_W= NR-nF (1) This calculated front-rear wheel speed difference ΔV_WDepending on the normal time
Between the driving performance of a four-wheel drive vehicle and the turning performance of a rear-wheel drive vehicle.
Shown in Fig. 11 for the purpose of compatibility and improvement of steering stability.
As described above, the front-rear wheel speed difference ΔV_WIs a predetermined value ΔV_W1(>
0), the front wheel side torque distribution command value T₂To "50"
And the front-rear wheel speed difference ΔV_WIs a predetermined value ΔV _W2(<0)
If there is, the front wheel side torque distribution command value T₂Is set to "15"
Then, the front-rear wheel speed difference ΔV_WIs greater than or equal to "0" and is predetermined
Value ΔV_W1If the following is true, the front wheel side torque distribution command value T₂To
Calculated by the following equation (2a), the front-rear wheel speed difference ΔV_W
Is equal to or less than “0” and a predetermined value ΔV_W2If it is above, the front wheel
Side torque distribution command value T₂Is calculated by the following equation (2b)
I am doing it.

T ₂ = k ₁ · ΔV _W ··· (2a) T ₂ = k ₂ · ΔV _W ··· (2b) However, when the different-diameter wheels are mounted as described above, the front and rear wheels are in a direct-coupled four-wheel drive state. Rotation at the same speed is not preferable because the running stability is lowered and the power train system is loaded as described above. However, it is necessary to select the direct drive four-wheel drive state with a switch or to automatically switch to the direct drive four-wheel drive state (for example, to obtain straight running stability). If the vehicle speed is low, the traveling stability may be reduced and the load on the powertrain system may be suppressed to a low level as described above. In vehicles that are not in the direct-coupled four-wheel drive state, if different-diameter wheels are installed, the rotational speed difference between the front and rear wheels will increase. You can

Therefore, in this embodiment, the rotational speed difference between the front and rear wheels, specifically, the rear wheels 2RL, 2 which are the main driving wheels.
From the average rear wheel speed (rear wheel rotation detection value nR) obtained from the average rotation speed of the RR, subtract the average front wheel speed (front wheel rotation detection value nF) obtained from the average rotation speed of the front wheels 2FL and FR that are the auxiliary drive wheels. Then, the front-rear wheel speed difference ΔV _W is calculated based on the equation (1), and the front-rear four-wheel drive state prohibition threshold ΔV _W0 of the front-rear wheel speed difference ΔV _W corresponding to the vehicle speed is shown.
A front-rear wheel speed difference threshold curve is created in advance, the threshold value ΔV _W0 is set according to the vehicle speed from this vehicle speed-front-rear wheel speed difference threshold curve, and the calculated front-rear wheel speed difference value ΔV _W and the set threshold value ΔV _W
By comparing with _W0 , it is decided whether or not to prohibit the direct drive four-wheel drive state.

Then, specifically, assume a case where a different diameter wheel is mounted by mounting an emergency wheel having only one wheel having a smaller diameter than the other wheels. In this case, the front-rear wheel speed difference ΔV _W Is larger than “0”, there is a small-diameter wheel (emergency wheel) on the rear wheel, so the calculated value Δ of the front-rear wheel speed difference is Δ.
When V _W is equal to or greater than the threshold value ΔV _W0, it is determined that the direct-coupling four-wheel drive state is prohibited, and if the front-rear wheel speed difference ΔV _W is “0” or less, there is a small-diameter wheel (emergency wheel) attached to the front wheel. ,
When the calculated value ΔV _W of the front-rear wheel speed difference is less than or equal to the threshold value ΔV _W0, it is determined that the direct-coupling four-wheel drive state is prohibited.

Here, as the vehicle speed-front and rear wheel speed difference threshold curve, when the front and rear wheel speed difference ΔV _W is larger than “0”, the graph shown in FIG. 12 is shown, and the front and rear wheel speed difference ΔV _W is “0”. In the following cases, the graph shown in FIG. 13 is used. Such a vehicle speed-front and rear wheel speed difference threshold curve uses, for example, a diameter difference between the different-diameter wheel and another wheel as a parameter, and a front and rear wheel speed difference ΔV _W accompanying a change in vehicle speed (pseudo vehicle speed) in a two-wheel drive state. Of the front-rear wheel speed difference ΔV _W ＞
In the case of 0 and ΔV _W <0, the wheel diameter difference between the wheels with different diameters is examined when the vehicle speed is low, considering the deterioration of running stability due to the attachment of wheels with different diameters and the degree of load on the powertrain system. The allowable value is set to be small when the allowable value is large and the vehicle speed is high.

If it is determined that the direct-coupling four-wheel drive state is prohibited, when the direct-coupling four-wheel drive mode is selected in the two-wheel drive state, the front wheel side torque command value T ₂ is kept in order to keep the two-wheel drive state. Is set to “0” as it is, and when the direct four-wheel drive mode is selected in the automatic four-wheel drive state in which the torque is distributed according to the front and rear wheel speed difference, or as described above, the front and rear four-wheel drive mode is selected. When the front wheel side torque command value T ₂ set according to the wheel speed difference ΔV _W is “50”, the front wheel side torque command value T ₂ is set to a predetermined value B less than “50”.
It was decided to set it to (upper limit).

On the other hand, when the vehicle with the different diameter wheels mounted is started in the direct-coupled four-wheel drive state by selecting the changeover switch or the like, the difference in the rotational speed between the front and rear wheels as described above does not occur.
Therefore, in this case, in the same manner as described above, in order to determine whether the different-diameter wheels are mounted based on the rotational speed difference between the front and rear wheels, the driving force distribution between the main and auxiliary driving wheels is changed to a value other than 1: 1. Therefore, it is necessary to determine whether the different-diameter wheels are mounted after the front and rear wheels are allowed to rotate at different speeds. However, for the purpose of determining whether or not the wheels with different diameters are mounted, it is necessary to shift from the directly connected four-wheel drive state to the state where the driving force distribution between the main and auxiliary drive wheels is not 1: 1 (for example, automatic four-wheel drive). As described above, it is not preferable in that it will deviate from the direct-drive four-wheel drive state that is made based on the necessity, and it should be done carefully.

Therefore, in this embodiment, the vehicle speed is equal to or higher than a predetermined value (for example, 60 km / h) and the fluctuation is within a predetermined range (for example, ± 3.5 km / h) for a predetermined time t ₁ ( Only when the continuous operation is continued for, for example, 10 seconds or more, the direct connection four-wheel drive state is changed to the automatic four-wheel drive state for the purpose of determining the attachment of the different diameter wheels.
That is, in the high speed range where the vehicle speed is, for example, 60 km / h or more, the difference between the front and rear rotational speeds due to the turning trajectory difference is, for example, 0.2 k.
Since it is as small as less than m / h, its influence can be excluded. Also, during acceleration / deceleration, the slip ratio of the wheels increases and the difference in rotational speed between the front and rear wheels increases, so it is not possible to accurately determine whether or not the wheels with different diameters are mounted.
If the fluctuation is within ± 3.5 km / h for 10 seconds at m / h or more, the acceleration fluctuation width is within 0.01 G and it can be assumed that the vehicle is running at a constant speed. _{By using W} , it is possible to accurately determine whether the wheels with different diameters are mounted.

Here, as a concrete method for judging that the state in which the fluctuation range of the vehicle speed is within the predetermined range has continued for the predetermined time t ₁ or more, in this embodiment, the vehicle speed detection value at a certain sampling time (specific a reference value V _FFK pseudo vehicle speed V _FF) described later, the reference value V _FF predetermined variation value from _K [Delta] V _FF
A value obtained by subtracting (3.5 km / h) is set as a minimum value, and a value obtained by adding the same fluctuation value ΔV _FF to the reference value V _FFK is set as a maximum value. It was decided to check whether or not the state in which _FF was entered continued for a predetermined time t ₁ or longer. Then, if the vehicle speed detected value V _FF before the predetermined time t ₁ elapses becomes outside the range, and update sets the vehicle speed detection value V _FF to reference value V _FFK, within the range based on the new reference value V _FFK Further, the state in which the vehicle speed detection value V _FF sampled after that is included in the predetermined time t
It was decided to repeat this until _one or more was continued.

Even when the direct drive four-wheel drive state is changed to the automatic four-wheel drive state, the response of the clutch mechanism, the command torque filtering, the time required to achieve a predetermined hydraulic pressure, and the power including the wheels are obtained. Since the difference in rotational speed between the front and rear wheels does not occur immediately due to the train inertia or the like, it is necessary to determine whether or not the different diameter wheels are mounted after a lapse of a predetermined time in consideration of such a response delay. Therefore, in this embodiment, after the above-described automatic four-wheel drive transition condition (vehicle speed and its variation condition) is satisfied in the direct-coupling four-wheel drive state, the torque on the front wheel side changes from the value in the direct-coupling four-wheel drive state to the automatic four-wheel drive state. The front wheel side torque command value T ₂ is set to a predetermined value A ₀ so as to change to the minimum torque value in the wheel drive mode (A ₀ : front wheel side torque command value for achieving the minimum torque). After a lapse of a predetermined time t ₂ (for example, 3 seconds) in which the filtering time and the power train inertia elimination time are taken into consideration, it is determined that the different-diameter wheels are mounted based on the front-rear wheel speed difference ΔV _W.

Further, the determination of such different-diameter wheel mounting is as follows.
Normally, while the ignition switch is ON to OFF
It may be performed once, but in this embodiment,
As described above, the pre-created vehicle speed-front and rear wheel speed difference (direct connection
Four wheel drive status prohibited) Threshold ΔV _W0From curve to front according to vehicle speed
Threshold ΔV_W0Is set, and the calculated value of the front and rear wheel speed difference ΔV_WWhen
Threshold ΔV_W0Prohibits direct-drive four-wheel drive by comparison with
In order to determine whether or not
Even if it is once determined to be absent, the threshold Δ
V_W0When the direct connection four-wheel drive state is prohibited due to change in
There is also.

Therefore, when it is determined that the vehicle speed is outside the direct-coupling four-wheel drive state prohibition region, the vehicle speed is a predetermined value (V which will be described later).
_{It was} decided to continue the judgment as long as it was _FF2 ) or above. Then, when it is determined that the vehicle is in the direct-coupled four-wheel drive state prohibition region, if the determination continues for a predetermined time t ₃ (for example, 5 minutes), the fact is notified to the driver by blinking the fail lamp. After that, the control for determining whether or not the vehicle is in the directly-coupled four-wheel drive state prohibition region is ended. As a result, the front / rear wheel speed difference ΔV _W is on the side of the direct-connection four-wheel drive state prohibition region from the threshold value ΔV _W0 due to causes other than the attachment of wheels with different diameters (for example, due to turning, braking, driving, etc.). It is prevented from being judged. Then, the vehicle speed is set to a predetermined value smaller than the predetermined value (V _FF2 ) (V which will be described later) so that the control is started again after the ignition switch is turned off.
_When it is less than _FF1 ), the direct connection four-wheel drive status prohibition status is released.

In this embodiment, the four wheels obtained by the following equation (3) are obtained from the rear wheel rotation detection value nR corresponding to the average rear wheel speed and the front wheel rotation detection value nF corresponding to the average front wheel speed. The pseudo vehicle speed V _FF corresponding to the average value of is used as the vehicle speed. V _FF = 1/2 (nR + nF) (3) When the rotation sensors 17F, 17R on at least one of the front wheel side and the rear wheel side are not operating normally, the control is accurately performed. Since it is not performed, the control is not performed when at least one of the fail signals S _FF and S _FR of the respective rotation sensors is transmitted.

Further, it is determined whether the vehicle to be controlled is already in the direct-coupled four-wheel drive state by the hydraulic switch 23.
From the above, it is determined whether or not the predetermined hydraulic pressure detection signal S _A1 indicating that the clutch supply pressure Pc has become equal to or greater than the predetermined value A ₁ indicating the direct connection four-wheel state (front wheel side torque distribution T ₂ = 50) is output. I decided to do it. And in this example,
In consideration of the above, the first arithmetic processing for determining whether or not the direct drive four-wheel drive state is prohibited, and the front wheel side torque distribution command for distributing the driving force between the front and rear wheels The value T ₂ is determined by at least the drive mode detection value M from the drive mode switch (in addition to this when M = AUTO4, the detection value of the front and rear wheel rotation speed difference), and the progress and result of the first arithmetic processing. (As described above, T ₂ = 0,5
0, A ₀ , B, k ₁ · ΔV _W , k ₂ · ΔV _W ) The second arithmetic processing for setting and outputting is performed in parallel.

Incidentally, the drive state signal S _K indicating the drive state currently being performed is set by another calculation process or the like. When the four-wheel drive state is changed to the automatic four-wheel drive state, the drive state signal S _K is changed to the direct drive four-wheel drive state inhibition signal S _N by the first arithmetic processing shown in FIG. It will be changed to one that indicates the state of automatic four-wheel drive.

Next, based on such a basic principle, it is determined whether or not the vehicle has a different diameter wheel (emergency small diameter wheel) attached to the vehicle, and the vehicle is directly connected when the direct connection four-wheel drive state prohibition region is brought about. The microcomputer 70 of the controller 58 is used to perform control not to set the four-wheel drive state.
14 for the first arithmetic processing performed in FIG.
Each will be described according to the flowchart of FIG.

These calculation processes are the same in the predetermined cycle Δ.
This is executed as a timer interrupt process for each T _S (for example, 10 msec), and in the first calculation process shown in FIG. 14, the control flag F ₁ indicates that the directly connected four-wheel drive state is prohibited due to the attachment of the different diameter wheels. F means that it has been made
The direct four-wheel drive state prohibited ₁ = 1, it executes the release of the F ₁ = 0 in the direct four-wheel drive state capable or direct four-wheel drive state prohibited. Further, the control flag F ₂ is the reference value V used for determining whether the fluctuation range of the vehicle speed satisfies the predetermined condition.
_FFK is meant a state in which the updated set, the reference value V _FFK updated set at F ₂ = 1, to perform the reference value V _FFK update unset by F ₂ = 0. Further, the control flag F ₃ means a state in which the directly connected four-wheel drive state is shifted to the automatic four-wheel drive state for the determination of the different-diameter wheel attachment, and F ₃ = 1 is used for the different-diameter wheel attachment determination. When the auto four-wheel drive state is F ₃ = 0, the release from the auto four-wheel drive state for determining the different-diameter wheel mounting is executed. Further, the control flag F ₄ means that the condition for the determination of the different-diameter wheel attachment is satisfied and the determination of the different-diameter wheel attachment is started, and the determination start of the different-diameter wheel attachment is started with F ₄ = 1. , F ₄ = 0, a condition check for determining whether or not a different-diameter wheel is mounted is executed.

Furthermore, each of the predetermined times t₁, T₂, T₃
The measurement of each type consists of count values.
Man₁, N₂, N₃Is used, and the reference value V
_FFKN is set to a certain value for n₁・ ΔT_S
Is calculated for a predetermined time t ₁Compared with different diameter wheels
Auto four-wheel drive from directly connected four-wheel drive state for installation judgment
N is the elapsed time since the transition to the state₂・ ΔT_SCalculated by
This is the predetermined time t₂Direct drive four-wheel drive compared to
The time during which the determination of prohibition continues is n₃・ ΔT_SCalculated by
This is the predetermined time t₃Compared to.

In the first arithmetic processing shown in FIG. 14,
First, in step S100, the high speed shift position sensor 86
The high speed shift position detection signal S _H from
Moreover, it is determined whether or not the low speed shift position detection signal S _L from the low speed shift position sensor 88 is output, the high speed shift position detection signal S _H is output, and the low speed shift position detection signal S _L is output. If not, step S10
1a, and if not (that is, the low speed shift position detection signal S _L is output and the high speed shift position detection signal S _H is not output), step S101b
Move to

[0073] At step S101a, the front wheel speed sensor 17F, the fail signal S _FF for the rear wheel rotation sensor 17R, it is determined whether or not S _FR is not output together, either fail signal S _FF, S _{If FR is} also not output, the process proceeds to step S102, and if not (that is, if one of the fail signals S _FF and S _FR is output), the process proceeds to step S101b.

In step S101b, the control flag F ₄ is set to "0", and then the process returns to the main program. In step S102, the front wheel rotation sensor 1
Front wheel rotation detection value nF from 7F and rear wheel rotation sensor 1
The rear wheel side rotation detection value nR from 7R is read. Next, the process proceeds to step S103, and the front wheel side rotation detection value nF and the rear wheel side rotation detection value nR read in step S102 are read.
From the above, the pseudo vehicle speed V _FF is calculated according to the equation (3).

Next, in step S104, it is determined whether or not the pseudo vehicle speed V _FF calculated in step S103 is equal to or greater than a preset predetermined value V _FF1 (for example, a value corresponding to 50 km / h). If it is determined that the pseudo vehicle speed V _FF is equal to or higher than the predetermined value V _FF1 , the process proceeds to step S105, otherwise (that is, if V _FF <V _FF1 ).
Control goes to step S106.

In step S105, it is determined whether or not the pseudo vehicle speed V _FF calculated in step S103 is equal to or greater than a preset predetermined value V _FF2 (for example, a value corresponding to 60 km / h), and If the pseudo vehicle speed V _FF is equal to or higher than the predetermined value V _FF2 , the process proceeds to step S107, and if not (that is, if V _FF <V _FF2 ), the process proceeds to step S101b.

In step S106, the control flag F
_After setting ₁ to "0", the process proceeds to step S101b. In step S107, the control flag F ₁
Is not "1", and if F ₁ ≠ 1, the process proceeds to step S108, and if not (that is, F 1).
_{If 1} = 1), the process proceeds to step S101b.

[0078] In the step S108, the from the hydraulic switch 23 is judged whether or not a predetermined oil pressure detection signal S _A1 is output, the process proceeds to step S109 if not predetermined fluid pressure detection signal S _A1 is output, Otherwise (that is, if the predetermined hydraulic pressure detection signal S _A1 is output), the process proceeds to step S110. Step S11
At 0, it is determined whether the control flag F ₄ is "1", and if F ₄ = 1 then the process proceeds to step S112 and F ₄
If ≠ 1, the process proceeds to step S111.

In step S109, the control flag F
₄ is set to "1" and the process proceeds to step S112. In step S112, in step S10
Based on the front wheel side rotation detection value nF from the front wheel rotation sensor 17F and the rear wheel side rotation detection value nR read from the rear wheel rotation sensor 17R read in 2, the front-rear wheel speed difference ΔV _{W is} calculated according to the equation (1). To calculate.

Next, the routine proceeds to step S113, where the front-rear wheel rotational speed difference ΔV _W calculated at step S110.
Is greater than “0”, and if ΔV _W > 0, the process proceeds to step S114, and if not (ie, ΔV _W ≦ 0), the process proceeds to step S115.
12 shows a vehicle speed (pseudo vehicle speed V _FF ) _-front and rear wheel speed difference threshold curve when ΔV _W > 0 in step S114.
From the graph, the front and rear wheel speed difference threshold ΔV _W0 corresponding to the pseudo vehicle speed V _FF calculated in step S103 is set, and then the process proceeds to step S116.

In step S116, the front / rear wheel speed difference calculation value ΔV _W calculated in step S110 is set to the front / rear wheel speed difference threshold ΔV _W set in step S114.
It is determined whether it is _W0 or more, and if the front and rear wheel speed difference calculation value ΔV _W is not less than the front and rear wheel speed difference threshold ΔV _W0 , the process proceeds to step S117, and if not, step S118.
Move to

In step S118, the counter n ₃
Is reset to "0", and then step S101b
Move to In step S117, the counter n ₃
After adding “1” to, the process proceeds to step S119. In step S119, the count value n ₃ of the counter n ₃ is multiplied by the sampling time ΔT _S to calculate the time during which the determination of prohibition of the direct drive four-wheel drive state is continued, and the calculated time is a predetermined value t ₃ It is determined whether or not the above is true, and if n ₃ · ΔT _S ≧ t ₃ , the process proceeds to step S120, and if not, the process returns to the main program.

In step S120, the counter n ₃
Is reset to "0". Next, the process proceeds to step S121, and the direct connection four-wheel drive state prohibition signal S _N is output. Then control proceeds to step S122, the control flag F ₁ is set to "1", the process proceeds to step S101b.

On the other hand, in the step S115, ΔV _W
From the graph of FIG. 13 showing the vehicle speed (pseudo vehicle speed V _FF ) _-front and rear wheel speed difference threshold curve when ≦ 0, the above step S103
Front and rear wheel speed difference threshold Δ according to the pseudo vehicle speed V _FF calculated in
After setting V _W0 , the process _proceeds to step S123. In step S123, the front-rear wheel speed difference calculation value ΔV _W calculated in step S110 is set to the step S1.
15 determines whether a less wheel speed difference threshold value [Delta] V _W0 before and set in the step S117, if the front and rear wheel speed difference calculating value [Delta] V _W is wheel speed difference threshold value [Delta] V _W0 less longitudinal
If not, the process proceeds to step S118.

[0085] In step S111, the control flag F ₂ is determined whether or not "1", the control flag F ₂ is shifted to "1" unless the step S124, the otherwise (i.e. Step S if F ₂ = 1)
Move to 125. In step S124, the pseudo vehicle speed V _FF calculated in step S103 is set to the reference value V _FFK of the pseudo vehicle speed and stored in the RAM of the storage device 7c.

Next, the process proceeds to step S216, the control flag F ₂ is set to "1", and then step S127.
Move to In step S125, the storage device 7c
After reading the latest reference value V _FFK stored in the RAM, the process _proceeds to step S127. In the step S127, a variation range of the pseudo vehicle speed V _FF is set based on the following equation (4) from the pseudo vehicle speed reference value V _FFK set in the step S124 or read in the step S125: V _FFK- ΔV _FF ) ≦ V _FF ≦ (V _FFK + ΔV _FF ) ... (4) It is determined whether the pseudo vehicle speed V _FF calculated in step S103 is within the variation range. Then, if the pseudo vehicle speed V _FF is within the fluctuation range, the process proceeds to step S128, and if not, the step S129.
Move to

In step S128, the counter n ₁
Is incremented by 1, and the process proceeds to step S130. In the step S130, the count value n of the counter n _1
1 is multiplied by the sampling time ΔT _S to calculate the time during which the reference value V _FFK continues to be set to a certain value, and it is determined whether or not the calculated time is equal to or greater than the predetermined value t ₁ . n
_{If 1} · ΔT _S ≧ t ₁ , the process proceeds to step S131,
If not, the process proceeds to step S101b.

In step S131, the counter n ₁
Is reset to "0". Next, the process proceeds to step S132, and the control flag F ₂ is reset to "0". Then control proceeds to step S133, is set to "1" to the control flag F _3. Then control proceeds to step S134, adds "1" to the counter n _2.

Next, in step S135, the count value n ₂ of the counter n ₂ is multiplied by the sampling time ΔT _S to change from the direct connection four-wheel drive state to the automatic four-wheel drive state for determining the different-diameter wheel attachment. The elapsed time after the transition is calculated, and it is determined whether the calculated time is equal to or greater than the predetermined value t ₂ and if n ₂ · ΔT _S ≧ t ₂ , step S1
36, and if not, the above step S101b.
Move to

In step S136, the counter n ₂
Is reset to "0". Then, after the process proceeds to step S137, and resets the control flag F ₃ "0",
Then, the process proceeds to step S109. On the other hand, in step S129, the counter n ₁ is reset to “0”,
Then, the process proceeds to step S138.

In step S138, the pseudo vehicle speed V _FF calculated in step S103 is updated and set to the reference value V _FFK of the pseudo vehicle speed and stored in the RAM of the storage device 70c, and then the process proceeds to step S139. Step S
At 139, the control flag F ₂ is set to "1", and then the process proceeds to step S101b.

In the second arithmetic processing shown in FIG. 15, the drive mode detection value M from the drive mode switch 60 is first read in step S201. Next, the process proceeds to step S202, and if the drive mode detection value M read in step S201 is "AUTO4", the process proceeds to step S203, otherwise (that is, M =
If 2 or LOCK4), the process proceeds to step S204.

In step S203, the front wheel rotation detection value nF from the front wheel rotation sensor 17F and the rear wheel rotation detection value nR from the rear wheel rotation sensor 17R are read. Next, in step S205, the front / rear wheel speed difference ΔV _W is calculated from the equation (1). Next, step S206.
Then, the front wheel side torque distribution command value T ₂ is set according to the front / rear wheel speed difference ΔV _W calculated in step S205 from the characteristic shown in FIG. Next, in step S207, it is determined whether the control flag F ₁ of the first arithmetic processing shown in FIG. 14 is “1”, and F ₁ =
If it is 1, the process proceeds to step S208, and if not, the process proceeds to step S209.

In step S208, it is determined whether or not the front wheel torque distribution command value T ₂ set in step S206 is equal to or greater than the predetermined value B (upper limit value less than 50), and if T ₂ ≧ B. If so, the process proceeds to step S210, and if not, the process proceeds to step S211. In the step S209, it is determined whether the control flag F ₃ of the first arithmetic processing shown in FIG. 14 is "1", the process proceeds to step S212 if F ₁ = 1, otherwise Then, the process proceeds to step S211.

In step S210, the front wheel side torque distribution command value T ₂ is set to the predetermined value B, and then the process proceeds to step S211. In step S212, the front wheel side torque distribution command value T ₂ is set to the predetermined value A ₀ (command value for achieving the initial torque of the automatic four-wheel drive), and then the process proceeds to step S211.

On the other hand, in step S204, it is determined whether or not the drive mode detection value M read in step S201 is "2". If M = 2, the process proceeds to step S213, and otherwise. If so, the process proceeds to step S214. At step S213, the front-wheel side torque distribution instruction value T ₂ after setting "0", the step S
The processing moves to 211.

In step S214, it is determined whether or not the control flag F ₁ of the first arithmetic processing shown in FIG. 14 is "1", and if F ₁ = 1 then the process proceeds to step S215a. If not, the process proceeds to step S215b.
In step S215a, the latest drive mode previous value M ₀ stored in the RAM of the storage device 7c is read, and then the process proceeds to step S217.

In step S217, it is determined whether or not the drive mode previous value M ₀ read in step S215 is "2". If M ₀ = 2, the process proceeds to step S213. Otherwise, the step S20
Move to 3. In step S215b, it is determined whether the control flag F ₄ of the first arithmetic processing shown in FIG. 14 is "1", and if F ₄ = 1 then the process proceeds to step S215a. If not, step S216
Move to

In step S216, it is determined whether or not the control flag F ₃ of the first arithmetic processing shown in FIG. 14 is "1", and if F ₃ = 1 then the process proceeds to step S212. If not, the process proceeds to step S218.
In step S218, the front wheel side torque distribution command value T
_After setting ₂ to "50", the process proceeds to step S211.

Then, in the step S211, the steps S206, S210, S212, S213, S
The front wheel side torque distribution command value T ₂ set in any of 218 is output. Then, the process proceeds to step S219,
Drive mode detection value M read in step S201
Is stored in the RAM of the storage device 7c as the drive mode previous value M ₀ , and then the process returns to the main program.

The front wheel torque distribution set in this way
Minute command value T₂Is the output interface of the microcomputer 7.
By the face circuit 7d, the front wheel side torque distribution command value
T₂Clutch pressure P according to_CDuty ratio D to achieve
Signal CS consisting of an analog voltage value indicating₀Converted to
The control signal CS₀Is input to the drive circuit 31a,
T₂If ≠ 0, the control signal CS is sent to the drive circuit 31b.₀Is in
I will be forced. Along with this, in the drive circuit 31a, the control
Signal CS₀Excitation current i with duty ratio D ₀Before
Of the duty control solenoid valve 128 in the hydraulic pressure supply device 16
Output to the solenoid 128d. Also the drive circuit
In 31b, the control signal CS₀Is excited when is input
Flow i₀Of the electromagnetic switching valve 120 in the hydraulic pressure supply device 16.
Output to the solenoid 120d, and control signal CS₀But
When not input, exciting current i ₁Is not output.

As a result, the front wheel side output torque command value T ₂ ≠
In the case of 0, the input port 120A of the electromagnetic switching valve 120
Passed to the output port 120B are communicated, the pilot selector valve 126 is turned right side half-section the state of FIG. 7, the adjusting pressure from the clutch pressure regulating valve 122 is supplied to the external pilot port 126 _P1 of the pilot switching valve 126, the adjustment The pressure can be supplied to the clutch 66. In this case, the duty control solenoid valve 128 has the return spring 128a.
Against this, the spool moves from the normal position 128b to the operating position 128c, and the control pressure corresponding to the control signal CS ₀ is applied to the external supply port 122 of the clutch pressure adjusting valve 122.
_{Since the} control pressure is output to _P2 , the clutch pressure adjusting valve 1
22 is output to the external supply port 122 _P2 , so that the adjustment pressure of the clutch pressure adjustment valve 122 is applied to the control signal CS.
_The pressure is controlled to a value according to ₀ , and the adjustment pressure from the clutch pressure adjustment valve 122 via the pilot switching valve 126 (that is, the supply pressure Pc to the clutch according to the front wheel side torque distribution command value T ₂ ) is applied to the clutch 66. Supplied.

This clutch supply pressure Pc is the hydraulic pressure supply device 1.
6 is supplied to the input port 74 in the transfer 22. According to the supplied clutch supply pressure Pc, the friction plate 66b and the friction disc 66d make frictional contact as described above, and the frictional contact force is generated. The driving torque (driving force) drives and rotates the clutch hub 66c of the clutch 66, and the driving torque (driving force) is transmitted to the front wheel side drive shaft 24 through the gear train, and further, through the power transmission system. Front wheel 12F
The rear wheels 12RL, 1 are transmitted to the L, 12FR.
The transmission driving force to the 2RR is reduced by that amount, and
In the second arithmetic processing shown in 5, the four-wheel drive state in which the desired torque distribution is achieved is achieved.

On the other hand, the front wheel side output torque command value T₂= 0
If the control signal CS₁Is not output,
Input port 120A and output port 120B of the exchange valve 120
And the pilot switching valve 126 is not connected to the left side of FIG.
The side half cross section is reached, and the external power switch of the pilot switching valve 126
Ilot port 126_P1The clutch pressure regulating valve 122
The adjusting pressure from the clutch 6 is not supplied without being supplied.
6 cannot be supplied. In this case, the duty control
The magnetic valve 128 has a duty ratio D₁Control equivalent to
Signal CS₀Is input, the spool is in the normal position.
Stop at 128b or move from operating position 128c to normal position
128b, the clutch pressure P _CIs P₁With
Then, the adjustment pressure of the clutch pressure adjustment valve 122 is also adjusted to the front wheel side.
Luk distribution command value T₂The value is not controlled according to.

Therefore, in this case, since the hydraulic pressure is not supplied from the hydraulic pressure supply device 16 to the input port 74 in the transfer 22, the friction plate 66b and the friction disc 66d do not come into frictional contact with each other as described above. As a result, the driving torque (driving force) is not transmitted to the front-wheel-side drive shaft 24, resulting in a two-wheel drive state.

At the same time, the set drive state signal S
_K is output to the indicator 25 via the output interface circuit 7d, and the actual drive state is displayed by the display data according to the output drive state signal S _K. Also, if it is determined that the direct drive four-wheel drive state is prohibited,
The direct-coupled four-wheel drive state prohibition signal S _N is output to the alarm device 27 via the output interface circuit 7d, and the blinking of the lamp or the sound is emitted, so that the direct-coupled four-wheel drive state is prohibited for mounting the wheels of different diameters. The driver is informed that he is there.
If the direct-drive four-wheel drive state is changed to the automatic four-wheel drive state for the determination of the different-diameter wheel mounting and the direct-connection four-wheel drive state is prohibited as a result of the determination, the direct-couple four-wheel drive state prohibition signal Since S _N is also output to the indicator 25 and the display data indicating the automatic four-wheel drive state is selected,
The driver is informed that the automatic four-wheel drive mode has been entered.

Next, the operation of the four-wheel drive control system for a vehicle of this embodiment, which is carried out by the arithmetic processing shown in FIGS. 14 and 15, will be described. First, in the four-wheel drive vehicle of this embodiment, the emergency small-diameter wheel is mounted on the rear wheel that is the main drive wheel, and the pseudo vehicle speed V _FF is applied while the vehicle runs at a constant speed on the high μ road in the two-wheel drive mode. It is assumed that the vehicle speed becomes equal to or higher than the predetermined value V _FF2 , and the driver selects the direct connection four-wheel drive mode by operating the changeover switch at this time. At this time, the front and rear wheel side rotation sensors 17F,
17R is assumed to be operating normally.

In this case, since the two-wheel drive state and the operation of the auxiliary transmission lever are not performed at the time of operating the changeover switch, the shift sleeve 64b in the auxiliary transmission mechanism 58 is not operated.
Is in the high speed position H. Therefore, in step S100 of the first arithmetic processing shown in FIG. 14, the high speed shift position sensor 86 outputs the high speed shift position detection signal S _H and the low speed shift position sensor 88 outputs the low speed shift position detection signal S _L. It is determined that it has not been output. Further, since neither of the fail signals S _FF and S _FR is output, the process proceeds from step S101a to step S102 and the front wheel rotation detection value nF and the rear wheel rotation detection value nR are read, and in step S103, the above (3) is performed. The pseudo vehicle speed V _FF is calculated according to the formula. Then, the pseudo vehicle speed V _FF is equal to or more than the predetermined value V _{FF1 in} step S104, and the pseudo vehicle speed V _FF is greater than or equal to the predetermined value V _FF1 in step S10.
It is determined in step 5 that the value is equal to or more than the predetermined value V _FF1 , and step S
To 107.

Then, at the first sampling when the condition for enabling the determination of the different-diameter wheel mounting is established, if it is not determined that the four-wheel drive state is prohibited, the process proceeds from step S107 to step S108. Since the predetermined hydraulic pressure detection signal S _A1 is not output from the hydraulic switch 23 unless the hydraulic pressure A ₁ necessary for the direct-coupled four-wheel drive state is achieved at that time,
From step S108 to step S109, the control flag F ₄ indicating that the different-diameter wheel mounting determination is started is set to "1". It should be noted that if it takes time for the above conditions to be satisfied, and if the hydraulic pressure A ₁ required for the direct drive four-wheel drive state is achieved with the detection of M = LOCK4 before F ₄ = ₁ is reached, the predetermined hydraulic pressure is set. The detection signal S _A1 is output from the hydraulic switch 23, and the process proceeds from step S108 to step S110 to step S111, in the same manner as when the direct-coupling four-wheel drive mode is selected from the time of start to be described later. It is determined whether or not different-diameter wheels are mounted by shifting from the state to the automatic four-wheel drive state.

If F ₄ = 1 is set in step S109, the process proceeds to step S113 via step S112. In this case, since the small diameter wheel is attached to the rear wheel, ΔV _W > 0 in step S113. The determination is made in step S11.
4, the threshold value ΔV _W0 is set according to the pseudo vehicle speed V _FF from the characteristics shown in FIG. 12, and the calculated value ΔV _W of the front and rear wheel speed difference is compared with the threshold value ΔV _W0 in step S116. Here, if ΔV _W ≧ ΔV _W0 according to the diameter difference between the small-diameter wheel and the other wheels and the pseudo vehicle speed V _FF , it is determined that the vehicle is in the direct-coupling four-wheel drive state prohibition region, and the process proceeds to step S117. Until the elapsed time n ₃ · ΔT _S from the start of the different-diameter wheel mounting determination in step S119 becomes equal to or longer than the predetermined time t, F ₄ = 1
As it is, the process returns to the main program from step S119, and as long as the above conditions are satisfied, the different diameter wheel mounting determination is performed as described above.

If F ₄ = 1 then F ₁ is always
= 0, so long as F ₄ = 1 is satisfied, steps S214, S215b, S215 in the second calculation process shown in FIG.
a, S217, S213, and then step S2
At 11, T ₂ = 0 is output. In addition, if it is determined that the vehicle is out of the direct-coupling four-wheel drive state prohibited area during this period, step S
From step 116 to step S118a, F ₄ = 0 is set and F ₁ = 0 is returned to the main program. For example, since the pseudo vehicle speed V _FF does not increase, it is continuously determined that the vehicle is out of the direct-coupling four-wheel drive state prohibition region. Then, in the second arithmetic processing shown in FIG. 15, steps S215b, S216, and S218 are performed.
, The front wheel side torque distribution value T ₂ = 50 that achieves the direct-coupled four-wheel drive state is output in step S211, or a threshold value Δ that becomes a severe value due to an increase in the pseudo vehicle speed V _FF or the like.
Based on V _W0 , it is again determined whether or not the vehicle is in the directly connected four-wheel drive state prohibition region.

Then, it is in the direct-connection four-wheel drive state prohibited area.
The judgment is a predetermined time t₃If the above continues, step S119
From S120 to counter n₃Is reset to "0"
Then, in step S121, the direct connection four-wheel drive state prohibition signal S_N
Is output, and the control flag F is output in step S122.₁But
Set to "1", control flag in step S101b
F _FourIs reset to "0".

Accordingly, in the second arithmetic processing shown in FIG. 15, since the drive mode detection value M read in step S201 is "LOCK4", step S202,
From S204 to step S214, step S2
In step S14, the control flag F ₁ is determined to be "1"
215a is reached, and the drive mode previous value M read here is read.
_{Since 0} is “2”, the process proceeds from step S217 to S213, where the front wheel side torque distribution command value T ₂ is set to “0”, and T ₂ = 0 is output in step S211.

As a result, as described above, the control signal CS ₀ corresponding to the front wheel side torque distribution command value T ₂ of "0" is input to the drive circuit 31a, and the control signal CS ₁ is input to the drive circuit 31b. Therefore, the exciting current i ₀ having a duty ratio corresponding to the front wheel side torque distribution command value T ₂ = 0 is output toward the solenoid 128d, and the exciting current i ₁ is not output from the drive circuit 31b. Along with this, the electromagnetic switching valve 120 and the pilot switching valve 12 as described above.
6, the duty control solenoid valve 128, and the clutch pressure adjusting valve 122 are in a state of keeping the clutch supply pressure Pc at P ₁ or less according to the front wheel side torque distribution command value T ₂ = 0. As a result, as described above, the friction plate 66b and the friction disc 66d are not in frictional contact with each other, and the driving torque (driving force) is not transmitted to the front wheel side drive shaft 24. Is selected, the two-wheel drive state continues.

At the same time, the direct connection four-wheel drive state prohibition signal S _N is sent to the alarm device 2 via the output interface circuit 7d.
7 and the alarm device 27 blinks a lamp or emits a sound, so that the driver is informed that the directly connected four-wheel drive state is prohibited due to the mounting of the wheels with different diameters. Further, the drive state signal S _K indicating that the vehicle is in the two-wheel drive state is output to the indicator 25, and the indicator 25 displays “2WD”.

Next, in the four-wheel drive vehicle of this embodiment, the emergency small-diameter wheels are mounted on the front wheels, which are auxiliary drive wheels, in the automatic four-wheel drive mode (the torque distribution to the front wheel side is direct connection four-wheel drive). While the vehicle is traveling at a constant speed on a high μ road in a state where the wheel drive state is less than 50%), the pseudo vehicle speed V _FF becomes a vehicle speed corresponding to the predetermined value V _FF2 or more, and at this time, the driver operates the changeover switch. It is assumed that the direct connection four-wheel drive mode is selected by operation. At this time, the rotation sensors 17F and 17R on the front and rear wheels are assumed to be operating normally. Further, the sub transmission 58 is in the high-speed shift position, and it is assumed that the sub transmission lever is not switched when the direct connection four-wheel drive mode is selected.

In this case, step S100 of FIG.
, It is determined that the high speed shift position sensor 86 is outputting the high speed shift position detection signal S _H and the low speed shift position sensor 88 is not outputting the low speed shift position detection signal S _L , and the fail signals S _FF , S are detected. _{Since FR} is not output together, step S1 is performed as in the above case.
01a through step S102 to step S103
And the pseudo vehicle speed V _FF calculated here is calculated in step S1.
04 is determined to be a predetermined value V _FF1 or more and step S105 a predetermined value V _FF1 or more, leading to a step S107.

Also in this case, as in the above case,
In this way, at the time of the first sampling when the condition for enabling the determination of the different-diameter wheel attachment is satisfied, if it is not determined that the four-wheel drive state is prohibited, steps S107 to S108.
At this point, the hydraulic pressure A ₁ required for the direct drive four-wheel drive state
Since the predetermined oil pressure detection signal S _A1 is not output from the oil pressure switch 23 unless the above condition is achieved, steps S108 to S108 are performed.
At 109, the control flag F ₄ indicating that the different-diameter wheel mounting determination is started is set to "1". It should be noted that if it takes time for the above conditions to be satisfied, and if the hydraulic pressure A ₁ required for the direct drive four-wheel drive state is achieved with the detection of M = LOCK4 before F ₄ = ₁ is reached, the predetermined hydraulic pressure is set. The detection signal S _A1 is output from the hydraulic switch 23, and step S1
From step 08 to step S111 through step S110, in the same way as when the direct-coupled four-wheel drive mode is selected from the time of starting, which will be described later, a different diameter due to the transition from the direct-coupled four-wheel drive state to the automatic four-wheel drive state. It is determined that the wheels are mounted.

When F ₄ = 1 is set in step S109, the process proceeds to step S113 via step S112. In this case, since the small diameter wheel is attached to the front wheel, it is determined in step S113 that ΔV _W ≦ 0. Step S11
5, the threshold value ΔV _W0 is set according to the pseudo vehicle speed V _FF from the characteristic shown in FIG. 13, and the calculated value ΔV _W of the front and rear wheel speed difference is compared with the threshold value ΔV _W0 in step S123. Here, if ΔV _W ≦ ΔV _W0 according to the radial difference between the small diameter wheel and the other wheels and the pseudo vehicle speed V _FF , it is determined that the vehicle is in the direct-coupling four-wheel drive state prohibition region, and the process proceeds to step S117. Until the elapsed time n ₃ · ΔT _S from the start of the different-diameter wheel mounting determination in step S119 becomes equal to or longer than the predetermined time t, F ₄ = 1
As it is, the process returns to the main program from step S119, and as long as the above conditions are satisfied, the different diameter wheel mounting determination is performed as described above.

If F ₄ = 1 then F ₁ is always
= 0, so long as F ₄ = 1 is satisfied, steps S214, S215b, S215 in the second calculation process shown in FIG.
a, S217, and S203, in that order, and the automatic four-wheel drive state is maintained by the subsequent processing. If it is determined during this period that the vehicle is out of the direct-coupling four-wheel drive state prohibition region, the process proceeds from step S116 to step S118 and F
₄ = 0 and the program returns to the main program with F ₁ = 0. For example, since the pseudo vehicle speed V _FF does not increase, it is continuously determined that the vehicle is out of the direct-coupling four-wheel drive state prohibition region. In the above calculation processing, the front wheel side torque distribution value T ₂ = 50 that achieves the direct-coupled four-wheel drive state is output as described above, or the threshold value ΔV _W0 becomes a severe value due to an increase in the pseudo vehicle speed V _FF , etc. It is determined whether or not the vehicle is in the direct-coupling four-wheel drive state prohibition region.

Then, it is in the direct-coupled four-wheel drive state prohibited area.
The judgment is a predetermined time t₃If the above continues, step S119
From S120 to counter n₃Is reset to "0"
Then, in step S121, the direct connection four-wheel drive state prohibition signal S_N
Is output, and the control flag F is output in step S122.₁But
Set to "1", control flag in step S101b
F _FourIs reset to "0".

Accordingly, in the second arithmetic processing shown in FIG. 15, since the drive mode detection value M read in step S201 is "LOCK4", step S202,
From S204 to step S214, step S2
In step S14, the control flag F ₁ is determined to be "1"
215a is reached, and the drive mode previous value M read here is read.
_{Since 0} is "AUTO4", steps S217 to S are executed.
At 203, the front and rear wheel speed difference ΔV _W is calculated in step S205 from the front wheel rotation detection value nF and the rear wheel rotation detection value nR read in here, and the front and rear wheel speed difference is calculated in step S206 according to the characteristic of FIG. The front wheel side torque distribution command value T ₂ is set according to ΔV _W , and the process proceeds to step S207. Here, since F ₁ = 1 is reached, the process proceeds from step S207 to S208, and the front wheel side torque distribution command value T ₂ set in step S206 indicates the direct drive four-wheel drive state.
If it is "0", the process goes to step S210 and T ₂ = B (5
Is set to an upper limit value of less than 0), the process proceeds to step S211, and if T ₂ ≠ 50 in step S206, the process directly proceeds to step S211 and T ₂ = B in step S211.
Alternatively, T ₂ less than 50 set in step S206 is output.

As a result, as described above, the control signal C having the voltage value corresponding to the front wheel side torque distribution command value T ₂ (<50).
Since S ₀ is input to the drive circuit 31a and the control signal CS ₁ is input to the drive circuit 31b, the drive circuit 31a outputs
The exciting current i ₀ corresponding to the duty ratio according to the front wheel side torque distribution command value T ₂ (<50) is the solenoid 1 of the duty control solenoid valve 128 in the hydraulic pressure supply device 16.
28d, and the solenoid 12 of the electromagnetic switching valve 120 in the hydraulic pressure supply device 16 is output from the drive circuit 31b.
An exciting current i ₁ corresponding to the current value I _k is output toward 0d. Accordingly, as described above, the electromagnetic switching valve 120, the pilot switching valve 126, the duty control electromagnetic valve 128, and the clutch pressure adjusting valve 122 respond to the front wheel side torque distribution command value T ₂ (<50). The state in which the clutch supply pressure Pc is supplied from the pilot switching valve 126 to the clutch 66 is maintained. As a result, as described above, the friction plate 66b and the friction disk 66d are brought into frictional contact with a force corresponding to the supplied clutch supply pressure Pc, and the drive torque (driving force) corresponding to the frictional contact force is applied. Clutch hub 6 of clutch 66
6c is driven and rotated, and its driving torque (driving force) is transmitted to the front wheel side drive shaft 24 via a gear train, and further, the front wheels 12FL, 1 are transmitted via the power transmission system.
Since it is transmitted to 2FR, the rear wheels 12RL, 12RR
The driving force transmitted to the vehicle is reduced by that amount, and the automatic four-wheel drive state other than the direct-coupling four-wheel drive is maintained according to the front wheel side torque distribution command value T ₂ (<50).

At the same time, the direct connection four-wheel drive state prohibition signal S _N is sent to the alarm device 2 via the output interface circuit 7d.
7 and the alarm device 27 blinks a lamp or emits a sound, so that the driver is informed that the directly connected four-wheel drive state is prohibited due to the mounting of the wheels with different diameters. Further, a drive state signal S _K indicating that the vehicle is in the automatic four-wheel drive state is output to the indicator 25, and the indicator 25 displays “AUTO4WD”.

Next, in the four-wheel drive vehicle of this embodiment, the direct connection four-wheel drive mode is selected from the time of starting with the emergency small diameter wheels mounted on the front wheels, which are the auxiliary drive wheels, and the high μ
It is assumed that the pseudo vehicle speed V _FF becomes a vehicle speed equivalent to the predetermined value V _FF2 or more while traveling on a road at a constant speed. At this time, the rotation sensors 17F and 17R on the front and rear wheels are assumed to be operating normally. Further, the sub transmission 58 is in the high-speed shift position, and it is assumed that the sub transmission lever is not switched when the direct connection four-wheel drive mode is selected.

In this case, step S100 of FIG.
, It is determined that the high speed shift position sensor 86 is outputting the high speed shift position detection signal S _H and the low speed shift position sensor 88 is not outputting the low speed shift position detection signal S _L , and the fail signals S _FF , S are detected. _{Since FR} is not output together, step S1 is performed as in the above case.
01a through step S102 to step S103
And the pseudo vehicle speed V _FF calculated here is calculated in step S1.
04 is determined to be a predetermined value V _FF1 or more and step S105 a predetermined value V _FF1 or more, leading to a step S107.

Also in this case, as in the above case,
In this way, at the time of the first sampling when the condition for enabling the determination of the different-diameter wheel attachment is satisfied, if it is not determined that the four-wheel drive state is prohibited, steps S107 to S108.
Leading to. However, in this case, since the vehicle is traveling in the direct-coupling four-wheel drive mode, the hydraulic pressure A ₁ required for the direct-coupling four-wheel drive state has been achieved at this point, so the predetermined hydraulic pressure detection signal S _A1 is transmitted to the hydraulic switch 23. Is output from
Step S11 through Step S108 to S110
In step S111, S124 to S139, it is determined whether or not it is possible to shift to the automatic four-wheel drive state for the purpose of the different-diameter wheel mounting determination, and then the shift is made to the automatic four-wheel drive state. After the shift, the elapse of a predetermined time t ₂ sufficient for the difference between the front and rear wheels is determined, and then the determination of the different diameter wheel mounting as described above is performed in the automatic four-wheel drive state.

That is, the pseudo vehicle speed V_FFVariation is within a predetermined range
Within (± ΔV_FF) Is a predetermined time t₁More than consecutive
In this case, the process goes from step S130 to step S131.
F in step S133₃= 1, and with this
The steps S216 to S216 in the second calculation process shown in FIG.
212, where the lowest level of auto four-wheel drive mode
Luc A₀Front wheel side torque distribution command value T indicating₂Is set
Then, in step S211, T₂= A₀Is output. this
Causes the excitation current i output from the drive circuit 31a.
₀But T₂= A₀Control signal C having a duty ratio corresponding to
S₀The above-mentioned hydraulic pressure supply device 1
6, the duty control solenoid valve 128, the solenoid switching valve 120,
For the pilot switching valve 126 and the clutch pressure adjusting valve 122
Than T₂= A ₀The clutch supply pressure Pc corresponding to
The minimum torque of the automatic four-wheel drive mode is supplied to the
Ku A₀Are distributed to the front wheels.

When the predetermined time t ₂ elapses in this state, the process proceeds from step S135 to step S136, F ₃ = 0 is set in step S137, then step S109 is reached, and F ₄ = 1 is set as described above. Then, the determination of the different-diameter wheel mounting is performed in the automatic four-wheel drive state. Then, if the result of the determination is that the direct-coupling four-wheel drive state is prohibited, F ₁ = 1 is established. Therefore, similarly to the above, the front wheel torque distribution command value T ₂ based on the front and rear wheel speed difference ΔV _W set in step S206.
There its value is less than 50, T ₂ at step S206
= 50 is set, T ₂ = B (5
Since the front wheel torque distribution command value T _{2 of} less than 50 is output in step S211, the automatic four-wheel drive state is set.

At the same time, the direct connection four-wheel drive state prohibition signal S _N is sent to the alarm device 2 via the output interface circuit 7d.
7 and the alarm device 27 blinks a lamp or emits a sound, so that the driver is informed that the directly connected four-wheel drive state is prohibited due to the mounting of the wheels with different diameters. Further, a drive state signal S _K indicating that the vehicle is in the automatic four-wheel drive state is output to the indicator 25, and the indicator 25 displays “AUTO4WD”.

As described above, in this embodiment, when it is determined in the running vehicle that the front / rear wheel speed difference detection value is in the directly connected four-wheel drive state prohibition region due to the attachment of the different-diameter wheels, it is determined that there is a predetermined time or more. Does not change from the other drive state to the direct drive four-wheel drive state, the drive state up to that point is continued, and when it is in the direct drive four-wheel drive state, it shifts to the automatic four-wheel drive state. Therefore, it is possible to reduce a decrease in traveling stability and an increase in load on the powertrain system which are caused by the direct-drive four-wheel drive state when the wheels having different diameters are mounted. Further, since the control is not performed when each rotation sensor of the front and rear wheels is not operating normally, the determination of the directly connected four-wheel drive state prohibition area accompanying the mounting of the different-diameter wheel is accurately performed, It is possible to avoid meaningless prohibition of the direct drive four-wheel drive state.

In particular, in this embodiment, even if the wheels with different diameters are mounted, the direct connection four-wheel drive state is not prohibited in all cases, but the vehicle speed is changed considering the necessity of the direct connection four-wheel drive state. The threshold value ΔV _W0 of the front-rear wheel speed difference ΔV _W , which is set accordingly, sets the directly connected four-wheel drive state prohibition region when the wheels with different diameters are mounted. Therefore, this device avoids a decrease in running stability and an increase in the load on the powertrain system that accompany a direct-drive four-wheel drive state when the wheels with different diameters are installed, and when the degree is considered to be small. Can be said to be a more practical device because it is allowed to be in the directly connected four-wheel drive state even when the wheels with different diameters are attached.

From the above, this embodiment is characterized by claims 1 to
It can be seen that the vehicle four-wheel drive control device according to No. 3 is embodied, and steps S102, S112 to S120, and S123 in the first calculation process shown in FIG.
Front wheel side rotation sensor 17F and rear wheel side rotation sensor 17R
Together with this, the different-diameter wheel mounting determination means of claims 1 to 3 is configured. Further, step S121 in the first arithmetic processing shown in FIG. 14 and steps S214, S215a, S207, S20 in the second arithmetic processing shown in FIG.
8, S210 corresponds to the direct connection four-wheel drive state prohibiting means of claims 1 to 3. Further, step S108 in the first calculation process shown in FIG. 14 constitutes the direct-coupling four-wheel drive state detecting means in claim 3 together with the hydraulic switch 23. Further, step S133 in the first arithmetic processing shown in FIG. 14 and steps S216, S209, S212 in the second arithmetic processing shown in FIG. 15 correspond to the driving force distribution changing means in claim 3. Further, the drive mode switch 21 and step S201 in the second arithmetic processing shown in FIG. 15 constitute the drive mode detecting means of claims 1 to 3. Further, the controller 18 is defined by claim 1
3 corresponds to the driving force distribution control means, and the transfer 22 and the hydraulic pressure supply device 16 correspond to the driving force distribution adjusting means of claims 1 to 3.

Although the four-wheel drive vehicle based on the rear-wheel drive vehicle has been described in detail in the above embodiment, the four-wheel drive control device for a vehicle according to the present invention is applied to this type of four-wheel drive vehicle. However, the present invention is not limited to this, and the clutch mechanism of the transfer may be controlled in a four-wheel drive vehicle based on a front-wheel drive vehicle. And in this case,
The above-mentioned front-rear wheel speed difference ΔV _{W is set} to ΔV _W = nF−nR, and step S2 in the second calculation process shown in FIG.
It suffices to change the characteristic of FIG. 11 used in 06 to a characteristic corresponding to this and perform the calculation.

Further, in the above-mentioned embodiment, only the vehicle provided with the auxiliary transmission in the transfer has been described in detail, but the four-wheel drive control system of the present invention can be applied to the vehicle not provided with such an auxiliary transmission. It can be deployed in the same way. Further, in the above-described embodiment, the case where the hydraulic friction clutch is used as the clutch mechanism has been described, but the clutch mechanism applicable to the four-wheel drive control system for a vehicle according to the present invention is not limited to this, and the electromagnetic friction clutch is used. It may be a clutch or the like.

Further, in the above embodiment, the case where the microcomputer is applied as the controller has been described, but instead of this, an electronic circuit such as an arithmetic circuit and a comparator may be combined.

[0137]

As described above, according to the four-wheel drive control system for a vehicle according to the present invention (that is, claim 1), when the wheels of different diameters are mounted, such as when the emergency wheels are mounted. For example, when it is determined by the different-diameter wheel attachment determining means as in claim 2 that the different-diameter wheel is attached based on the difference in rotation speed between the front and rear wheels, the direct-connection four-wheel drive state is determined by selecting the drive mode. Even if it is selected, the direct drive four-wheel drive state does not occur, so it is possible to avoid the deterioration of running stability and the powertrain system performance that would occur due to the direct drive four-wheel drive state with different diameter wheels attached. .

Particularly, according to the four-wheel drive control system for a vehicle according to the third aspect, the difference in rotational speed between the front and rear wheels can be achieved even if the wheels with different diameters are mounted, such as when the vehicle starts in the direct-coupled four-wheel drive state. Since the driving force distribution changing means causes a difference in the rotational speeds of the front and rear wheels when no occurrence occurs, even in such a case, the different diameter wheel mounting determination means according to claim 2 causes a difference. It is determined whether the radial wheels are mounted. Therefore, the device becomes more effective in an actual vehicle in which various cases are expected.

[Brief description of drawings]

FIG. 1 is a basic configuration diagram showing a four-wheel drive control system for a vehicle according to the present invention.

FIG. 2 is a basic configuration diagram showing a four-wheel drive control system for a vehicle according to claim 3 of the present invention.

FIG. 3 is a schematic configuration diagram showing an embodiment of a four-wheel drive control system for a vehicle according to the present invention.

FIG. 4 is a schematic configuration diagram showing an internal structure of a transfer that constitutes a driving force transmission system of the four-wheel drive control system for the vehicle shown in FIG.

5 is a schematic configuration diagram for explaining a high / low speed switching mechanism of the auxiliary transmission in the transfer of FIG.

6 is a block diagram showing a circuit configuration of a hydraulic pressure supply device that controls the operation of a friction clutch in the transfer shown in FIG.

FIG. 7 is a cross-sectional view showing a state of a pilot switching valve which constitutes the hydraulic pressure supply device in a difference between two-wheel drive and four-wheel drive.

FIG. 8 is a characteristic diagram showing a correlation between a command current to a solenoid of a duty control solenoid valve and a supply pressure to a friction clutch in the hydraulic pressure supply device.

FIG. 9 is a characteristic diagram showing a correlation between a supply pressure to a friction clutch and a transmission torque to a front wheel side in the transfer.

10 is a schematic configuration diagram showing the inside of a controller that constitutes the driving force distribution control device of the four-wheel drive control system for the vehicle shown in FIG. 3. FIG.

FIG. 11 is a graph showing a characteristic of a front wheel-side torque distribution command value that is normally set in the controller of the driving force distribution control device according to a front-rear wheel speed difference.

FIG. 12 is a graph showing front / rear wheel speed difference-pseudo vehicle speed characteristics for setting a threshold value of the front / rear wheel speed difference in which the directly connected four-wheel drive state is prohibited in the controller of the driving force distribution control device. It is used when the detected value of the speed difference is larger than "0".

FIG. 13 is a graph showing front / rear wheel speed difference-pseudo vehicle speed characteristics for setting a threshold value of front / rear wheel speed difference in which a directly connected four-wheel drive state is prohibited in the controller of the driving force distribution control device. It is used when the detected value of the speed difference is "0" or less.

FIG. 14 is a flowchart showing a procedure of a first arithmetic processing performed by one microcomputer in the four-wheel drive control system of the embodiment.

FIG. 15 is a flowchart showing a procedure of second arithmetic processing performed by one microcomputer in the four-wheel drive control system of the embodiment.

[Explanation of symbols]

 10 engine (engine) 12FL, 12FR front left wheel, front right wheel (auxiliary drive wheel) 12RL, 12RR rear left wheel, rear right wheel (main drive wheel) 14 drive force transmission system 15 drive force distribution control device 16 hydraulic power supply device (drive) Force distribution adjusting means) 14 Transfer (driving force distribution adjusting means) 24 Front wheel side output shaft 26 Front wheel side differential gear 28 Front wheel side drive shaft 30 Propeller shaft 32 Rear wheel side differential gear 34 Rear wheel side drive shaft 66 Clutch 17F Front wheel side rotation Sensor (different diameter wheel mounting determination means) 17R Rear wheel side rotation sensor (different diameter wheel mounting determination means) 18 Controller 31a, 31b Drive circuit 21 Drive mode switch (drive mode detection means) 7 Microcomputer (driving force distribution control means)

Claims (3)

[Claims] 1. A drive for distributing a driving force from an engine to a main drive wheel and a sub drive wheel in accordance with a control signal by using one of front and rear wheels of a vehicle as a main drive wheel and the other as a sub drive wheel. Force distribution adjusting means, drive mode detecting means for detecting the selected drive mode, and based on the drive mode detection value from at least the drive mode detecting means, set the drive force distribution between the main and auxiliary drive wheels, And, in a four-wheel drive control device for a vehicle, comprising a driving force distribution control means for outputting a control signal according to the set value to the driving force distribution adjusting means, at least one of all wheels mounted on the vehicle. A wheel with a different diameter is installed, which determines a different-diameter wheel mounting state in which the diameter of the wheel is different from the diameters of the other wheels, and the driving force distribution control means has a different diameter from the different-diameter wheel mounting determining means. car A four-wheel drive control device for a vehicle, comprising direct-connection four-wheel drive state prohibiting means for setting the driving force distribution between the main and auxiliary drive wheels to not 1: 1 based on the mounting detection value. . 2. The different-diameter wheel mounting determination means determines the different-diameter wheel mounting state on the vehicle based on a difference in rotational speed between front and rear wheels corresponding to the main driving wheel and the auxiliary driving wheel. The four-wheel drive control system for a vehicle according to claim 1, wherein: 3. A direct-coupling four-wheel drive state detecting means for detecting a direct-coupling four-wheel drive state in which the driving force distribution state between the main and auxiliary driving wheels by the driving force distribution adjusting means is 1: 1, and the driving force is provided. The distribution control means, when the direct-connection four-wheel drive state detection means detects the direct-connection four-wheel drive state, changes the driving force distribution between the main and auxiliary drive wheels to one in which the main drive wheel is larger than the auxiliary drive wheel. And a driving force distribution changing means for outputting a control signal according to the changed value to the driving force distribution adjusting means, wherein the different-diameter wheel attachment determining means is configured to change the driving force distribution by the driving force distribution changing means, 3. The four-wheel drive control system for a vehicle according to claim 2, wherein the four-wheel drive control system for a vehicle determines a mounting state of wheels having different diameters.