JPH02120141A - Controller for four-wheel drive vehicle - Google Patents

Abstract

PURPOSE:To prevent any braking phenomenon at time of front wheels being steered at a large steering angle from occurring by controlling a center differential gear to be built in a transfer so as to be selected to a free state when a fact that a transmission has been selected to a reverse state is detected. CONSTITUTION:A four-wheel drive vehicle is provided with a transmission 3 and a transfer with a built-in center differential gear 26 in the midway of a power transmission path 11, and this center differential gear 26 is made so as to be selected to a locking state by a center differential gear selector mechanism 38. In this case, these is provided with a reverse detecting means 79 which detects the transmission 3 being selected to a reverse state. When detecting the transmission 3 being selected to the reverse state, the center differential gear mechanism 38 is controlled so as to select the center differential gear 26 to a free state by a control means 80. With this constitution, a speed difference between front and rear wheels is differentially adjusted, whereby any braking phenomenon due to internal circulating torque at a driving system is prevented from occurring.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a control device for controlling switching of a center differential between a free state and a locked state in a four-wheel drive vehicle having a center differential in a drive system.

(Prior Art) Generally, in a four-wheel drive vehicle, a sub-transmission mechanism (H/L switching mechanism) that switches the transmission ratio of power transmitted from the engine to the wheels to a low speed state or a high speed state, or A center differential switching mechanism that switches the center differential between a locked state and a free state, and in the case of a part-time four-wheel drive vehicle that can also have a two-wheel drive state, a center differential switching mechanism that switches the drive state between a two-wheel drive state and a four-wheel drive state2. A plurality of switching mechanisms, such as a /4 switching mechanism, are provided for switching various states of power transmission to the wheels.

Conventionally, as disclosed in Japanese Unexamined Patent Application Publication No. 56-138020, in a part-time four-wheel drive vehicle that can switch the drive state between a two-wheel drive state and a four-wheel drive state, in the four-wheel drive state, While the vehicle is running, the rotational speed of each wheel is detected, and when the rotational speed difference between the front and rear wheels increases to a predetermined value or more, the vehicle is assumed to be turning with a large steering angle, and the 2nd rotation speed is automatically adjusted. It has been proposed to eliminate twisting of the drive train by switching and maintaining the wheel drive state.

(Problem to be Solved by the Invention) Generally speaking, the transmission of a vehicle is often switched to the reverse state when the vehicle is moving backwards to change direction. The front wheels (steering wheels) are steered at a large steering angle.

However, when the center differential of a four-wheel drive vehicle is in a locked state, when the front wheels are steered to a large steering angle during reverse and the rotational speed difference between the front and rear wheels increases due to the inner wheel difference, the Internally circulating torque is generated due to torsion in each drive system, resulting in a so-called braking phenomenon, and as a result, there is a problem in that switching operations during reverse are troublesome.

The present invention has been made in order to eliminate such problems, and its purpose is to control the switching of the center differential in the above-mentioned four-wheel drive vehicle in relation to the forward and backward traveling states of the vehicle. The objective is to eliminate the braking phenomenon even when the front wheels are steered at a large steering angle, and to facilitate the switching operation.

(Means for Solving the Problems) In order to achieve the above object, the solving means of the present invention detects that the transmission in a vehicle is switched to a reverse state, and when the reverse is detected, the center differential is forcibly released. It is to be held fixed in a certain state.

Specifically, the four-wheel drive vehicle, which is the premise of the present invention, uses the power of the engine 1 to drive the four wheels 7a, 7, as shown in FIG.
A transmission 3 and a transfer 4 having a built-in center differential 26 are provided in the middle of the power transmission path 11 that transmits the power to the motors 10a, 10a, and 10b, and the center differential 26 can be switched to a locked state by a center differential switching mechanism 38. ), has been created.

This four-wheel drive vehicle is provided with reverse detection means 79 for detecting that the transmission 3 has been switched to the reverse state.

Further, a control means 80 is provided which receives the output of the reverse detection means 79 and controls the center differential switching mechanism 38 so that the center differential 26 is switched to a free state when the transmission 3 is in the reverse state.

(Function) With the above configuration, in the present invention, when the transmission 3 of the vehicle is switched to the reverse state, this is detected by the seven reverse detection means, and the control means receives the output signal of the detection means 79. 80 controls the center differential switching mechanism 38 to switch the center differential 2 in the transfer 4.
6 is automatically switched to the free state. In the free state of this center differential 26, the front and rear wheels 7a, 7b, 10a
.

Since the rotational speed difference between wheels 10b is adjusted by the differential J31, even if the front wheels 7a and 7b are steered at a large steering angle to change the direction of the vehicle, a braking phenomenon occurs due to internal circulating torque in the drive system. Therefore, the switching operation during reverse can be easily performed.

(Example) Hereinafter, an example of the present invention will be described based on the drawings from FIG. 2 onwards.

FIG. 2 shows the overall configuration of an embodiment in which the present invention is applied to a part-time four-wheel drive vehicle, in which 1 is an engine mounted vertically in the front of the vehicle body, 3 is an engine connected to the engine via a clutch 2. A strange J that is connected to the drive! i aircraft, this transmission 3
A transfer 4 is disposed on the rear side. This transfer 4 has 5 front propeller shafts and 5 front differentials.
It is drive-coupled to left and right front wheels 7a and 7bl via left and right front axles 6a and 6b, and to left and right rear wheels 10a and 10b via a rear propeller 1 60, a rear differential 8, and left and right rear axles 9a and 9b, respectively. and
The clutch 2, transmission 3, transfer 4, front and rear propeller shafts 59 and 60, differential 58, and axle shafts 6a and 6
b, 9a, and 9b constitute a power transmission path 11 that transmits the power of the engine 1 to the four wheels.

As shown in detail in FIG. 3, the transfer 4 includes an input shaft 12 arranged on the same axis as the output shaft (not shown) of the transmission 3, and a rear part of the input shaft 12 (not shown). an intermediate shaft 13 arranged on the same axis on the right side), a front wheel output shaft 14 arranged parallel to the side of the intermediate shaft 13 and whose front end is connected to the five front propeller shafts; A rear wheel side output shaft 15 is disposed on the same axis behind the shaft 13 and has a rear end connected to the rear propeller 60.

An auxiliary transmission RIff16 (H/L switching mechanism) is disposed at the rear end of the input shaft 12 to switch the transmission ratio of power transmitted from the engine 1 to the wheels to a low speed state or a high speed state. ing. The auxiliary transmission mechanism 16 includes a sun gear 17 rotatably supported by the input shaft 12, and spline-coupled to the front end of the intermediate shaft 13 to rotate integrally.
A plurality of pinions 18, 18 meshing with the sun gear 17
．． It consists of a planetary gear mechanism having a pinion carrier 19 that carries... and a ring gear 20 that meshes with each of the pinions 18. The ring gear 20 has an auxiliary transmission mechanism 1.
6. A clutch hub 21 rotatably supported on the rear intermediate shaft 13 is rotatably coupled to the clutch hub 21, and a sleeve 22 is spline coupled to the outer periphery of the clutch hub 21 so as to be slidable in the axial direction. There is. In addition, the clutch hub 21
First and second spline gears 23 that can mesh with the inner peripheral spline teeth of the sleeve 22 are located at the front and rear positions of the sleeve 22, respectively.
The first spline gear 23 is fixed to the transfer case 4a and cannot rotate, and the second spline gear 24 is fixed to the intermediate shaft 13 so as to be rotatable. Then, by sliding the sleeve 22 on the clutch hub 21 and selectively engaging the inner peripheral spline teeth with the first or second spline gear 23, 24, the wheels 7a, 7b, 10a, 10b A first switching mechanism 25 is configured to switch the power transmission ratio to a low speed state, a high speed state, or a neutral state. That is, when the sleeve 22 is positioned at the front low speed position (PL) and its spline teeth are engaged with the first spline gear 23, the ring gear 20 is stopped and the rotation of the input shaft 12 is controlled by the sun gear 17 and each pinion. 18
The power is transmitted to the intermediate shaft 13 via the pinion carrier 19, and the rotation is decelerated during that time, thereby setting the power transmission ratio to a low speed state. On the other hand, when the sleeve 22 is positioned at the rear high speed position (PH) and meshed with the second spline gear 24, the human power shaft 12 is directly connected to the intermediate shaft 13 via the pinion carrier 19 and the ring gear 20 so as to rotate integrally. , the rotation of the human-powered shaft 12 is not decelerated and the intermediate shaft 13 is rotated as it is.
By transmitting the power to the engine, the power transmission ratio is set to a high speed state. Furthermore, the sleeve 22 is moved to the neutral position (P
N) and the spline gears 23, 24 are not engaged, the shafts 12, 1B are separated so that the rotation of the human power shaft 12 is not transmitted to the intermediate shaft 13, and a neutral state is established.

On the other hand, a planetary gear type center differential 26 is disposed at the rear end of the intermediate shaft 13. A sun gear 27 of this center differential 26 is rotatably supported on the intermediate shaft 13, and two pinion carriers carrying each pinion 28 are connected to the sun gear 2.
7 is rotatably spline-coupled to the rear intermediate shaft 13,
The ring gear 30 is rotatably coupled to the front end of the rear output shaft 15. The boss portion of the sun gear 27 extends forward around the intermediate shaft 13, and a clutch hub 31 is rotatably connected to the front end of the extended portion 27a, and a sleeve 32 is rotatably connected to the outer periphery of the clutch hub 31. and is spline-coupled so as to be slidable in the axial direction. Also,
Third and fourth spline gears 33 and 34 that can mesh with the inner peripheral spline teeth of the sleeve 32 are disposed at the front and rear positions of the clutch hub 31, respectively, and the third spline gear 33 is rotatably integrated with the intermediate shaft 13. is fixed.

On the other hand, the fourth spline gear 34 is a drive sprocket 3 rotatably supported on the extension part 27a of the sun gear 27.
5 and is fixed to rotate integrally.

Further, a chain 37 is wound between this drive sprocket 35 and a driven sprocket 36 which is rotatably coupled to the front wheel side output shaft 14.
Thus, the rotation on the intermediate shaft 13 side is transmitted to the front width side output shaft 14. By sliding the sleeve 32 on the clutch hub 31, the inner peripheral spline teeth are selectively engaged with the third or fourth spline gears 3B and 34, respectively, thereby bringing the center differential 26 into a free state or a locked state. Alternatively, a second switching mechanism 38 is configured to switch between a two-wheel drive state or a four-wheel drive state.

That is, by this second switching mechanism 38, the sleeve 32
When positioned at the front end two-wheel drive position (P!), the pinion carrier 29 of the center differential 26 and the sun gear 2
7 to directly connect the intermediate shaft 13 and the rear wheel output shaft 15 through the center differential 26, while separating the clutch hub 31 and the fourth spline gear 34, that is, the drive sprocket 35, to connect the intermediate shaft 13 and the front wheel output shaft. By cutting off the drive connection with the shaft 14, a two-wheel drive state is established. Also,
When the sleeve 32 is positioned at the rear end four-wheel drive/center differential free position (P4F), the clutch hub 31 is engaged with the fourth spline gear 34, and the intermediate shaft 13 is connected to the drive sprocket 35 (front wheel side) via the center differential 26. It is drivingly connected to the output shaft 14) and the rear-wheel side output shaft 15 to create a four-wheel drive state, and the center differential 26 is brought into a free state by disconnecting the pinion carrier 29 and sun gear 27. Furthermore, when the sleeve 32 is positioned at the front/rear intermediate four-wheel drive/center differential lock position (P4L),
Similarly to the above, the clutch hub 31 and drive sprocket 3
The pinion carrier 29 is rotationally connected to the sun gear 27 to put the center differential 26 in a locked state. Therefore, in this embodiment, this second switching mechanism 38 constitutes a center differential switching mechanism.

The first and second switching mechanisms 25.38 of the transfer 4
The structure for switching operation will be explained with reference to FIG. 5. In the figure, three are first shift rods that are slidably supported by the transfer case 4a, and at the front end (left end in the figure) is a first shift fork 40. However, there is a pin 41 on the outer periphery of the rear end.
The cylindrical members 42 projecting from each other are fixed immovably, and the first shift fork 40 is movably engaged with the outer periphery of the sleeve 22 of the first switching mechanism 25. A second shift rod 43 is arranged parallel to the first shift rod 39 and slidably supported by the transfer case 4a.
A second shift fork 44 is immovably fixed to the shift rod 43 by a boss portion 44a at a portion corresponding to the cylindrical member 42 on the first shift rod 39.
The shift fork 44 is movably engaged with the outer periphery of the sleeve 32 of the second switching mechanism 38, and its boss portion 44
A pin 45 is provided protrudingly from a. Furthermore, a drive shaft 46 rotatably supported by the transfer case 4a is disposed between the shift rods 39 and 43.
43, and a cylindrical cam 47 is fixed to a rotating body at the front end of this drive shaft 46. The outer periphery of this cam 47 has a first cam groove 47a on its front side that engages with the pin 41 of the cylindrical member 42 on the first shift rod 39.
However, there is also a second cam groove 47 on the rear side that engages with the pin 45 of the second shift fork 44 on the second shift rod 43.
b are each formed in a spiral shape. The rear end of the drive shaft 46 is connected to the transfer case 4 as shown in FIG.
a Drive connection is made to an electric motor 48 disposed outside, and the operation of this motor 48 causes the drive shaft 46 and the cam 47 to be driven.
For example, by rotating the cam 47 at a rotation angle of 60 degrees,
Both shift rods 39 are moved by sliding the pins 4145 in each cam groove 47a, 47b in the axial direction.
43 are made to slide in relation to each other. Therefore, this shift rod 39, 43, pins 41, 45,
The cylindrical cam 47, drive shaft 46, and motor 48 switch the first and second switching mechanisms 25.38 to two-wheel drive/high-speed mode (two-wheel drive/high-speed mode).
H), 4-wheel drive/high speed/center differential free mode (4H
F), 4-wheel drive/high speed/center differential lock mode (4H
L), 4-wheel drive/low speed/center differential lock mode (4
A transfer switching mechanism 49 is configured as a switching means that is configured to switch in combination to five types of switching states: LL) and neutral mode (N).

Furthermore, as shown in FIG. 3, the left front axle shaft 6a is divided into two in the axial direction near the front differential 5,
The divided portion includes a remote freewheel mechanism 5 that prevents the rotation of the front wheels 7a and 7b, which are idle wheels (non-driving wheels) in the two-wheel drive portion, from being transmitted to the transfer 4.
It is set to 0. The remote freewheel mechanism 50 includes a sleeve 51 rotatably and slidably splined to one of the divided parts of the front axle shaft 6a, and the sleeve 51 is rotatably and slidably splined to the other divided part. Movably splined to axle 6a
disconnect. A shift fork 52 is engaged with the sleeve 51 to move it, and the shift fork 52 is connected to a shift rod 5 driven by a diaphragm device 54.
It is attached to 3. Although not shown, the diaphragm device 54 has two negative pressure chambers partitioned by a diaphragm, each of which has a negative pressure passage 55.
．． It communicates with the intake passage of the engine 1 via 56. First and second solenoid valves 57 and 58, which are normally closed, are respectively disposed in the negative pressure passages 55 and 56.
When the first solenoid pulp 57 is opened, the intake negative pressure of the engine 1 is introduced into one of the negative and positive chambers, and the sleeve 51 is moved in the direction away from the other divided portion of the axle shaft 6a. By separating the divided portion of the shaft 6a, the rotation of the front wheels 7a and 7b is transferred to the transfer 4.
prevent it from being transmitted. On the other hand, when the second solenoid valve 58 is opened, intake negative pressure is introduced into the other negative pressure chamber and the sleeve 51 is moved in the opposite direction to the above, thereby opening the divided portion of the front axle shaft 6a. It is designed to be connected as a rotation unit.

As shown in FIG. 3, the motor 48 of the transfer switching mechanism 49 and the remote freewheel mechanism 5
Both solenoid valves 57 and 58 of No. 0 are configured to be operated and controlled by a control unit 70 having a built-in CPU. This control unit 70 includes
Each detection signal of the first to fourth four mode detection switches 71 to 74, each switching signal of the 2/4 changeover switch 76 and the H/L changeover switch 77 selected and operated by the driver, and the throttle of the engine 1. A detection signal from a throttle sensor 78 that detects the opening degree θ and a switching signal from a reverse switch 79 that is turned on when the transmission 3 is switched to the bajes position are input. In this embodiment, the reverse switch 79 79 constitutes reverse detection means for detecting that the transmission 3 has been switched to the reverse state.

The first mode detection switch 71 is set to a two-wheel drive mode (
2H) in the transfer switching machine tM49.
It detects whether the shift fork 44 is shifted to the two-wheel drive position (P2) and outputs a signal at the time of the shift. Similarly, the second mode detection switch 72 detects that the first shift fork 40 is shifted to the high speed position (PH) and outputs a signal. Furthermore, the third mode detection switch 73 selects two-wheel drive/high-speed mode (2H), four-wheel drive mode (2H),
Wheel drive/high speed/center differential free motor (4HF), 4
Wheel drive/high speed/center differential lock mode (4HL) and 4-wheel drive/low speed/center differential lock mode (4L L)
This is a position switch that determines four drive modes. Further, the fourth mode detection switch 74 detects the disconnected state of the front axle shaft 6a, that is, the operating state of the remote freewheel mechanism 50, based on the movement position of the shift fork 52 of the remote freewheel mechanism 50. Although not shown in the drawings, the control unit 70 is connected to a display device, a warning lamp, and the like.

The signal processing procedure performed by the CPU in the control unit 70 will be explained with reference to FIG.

First, in the first step S1 after the start, initial setting (initialization) is performed, and in the next step S2, the above-mentioned first to
Fourth mode detection switches 71 to 74 (#1 to #4 in the figure)
(shown in simplified form). moreover,
In step S3, the first to third mode detection switches 7
It is determined whether the detection states 1 to 73 all indicate the same mode, and if the determination is No, a lamp is lit for an alarm in step S4, and then the process returns to step S2.

On the other hand, when the determination in step S3 is YES, the process proceeds to step S5, where the first and fourth mode detection switches 71
．． Determine whether the detection states by 74 are the same,
If the determination is YES here, both solenoid valves 57.5 of the remote freewheel mechanism 50 are
If the determination is NO, it is determined in step S7 whether or not the detection state of the first mode detection switch 71 is the two-wheel drive mode. When this determination is YES, the remote freewheel mechanism 50 is in a four-wheel drive state (connected state of the split portion of the front axle shaft 6a) even though the transfer 4 is in a two-wheel drive state. In order to switch to the wheel drive state, in step S8, the first solenoid valve 57 is opened, and the second solenoid valve 58 outputs a closing signal. Conversely, when the determination in step S7 is No, the transfer 4 is in a four-wheel drive state and the remote freewheel mechanism 50 is in a two-wheel drive state (the front axle shaft 6a divided portion is cut off). In order to switch to the four-wheel drive state, step S9
The first solenoid valve 57 is closed, and the second solenoid valve 58 outputs a signal to open. Then, step S6° S7. After S9, the display device is turned on in step SIO to display a display according to the mode.

Furthermore, in step Sn, the reverse switch 79
is in the ON state. In other words, it is determined whether or not the transmission 3 is selected in the reverse position, and if this determination is No in the non-reverse position, the process advances to step SI2 and the 2/4
The specified mode selected by the driver is detected based on the switching signals of the changeover switch 76 and the H/L changeover switch 77, and then the first and second switching mechanisms 25, 38 of the transfer 4 or the remote freewheel mechanism 50 In order to switch, the process moves to a switching operation subroutine in step 513, and then returns to the first step S2.

On the other hand, if it is determined in step Sll that the vehicle is in reverse mode, the process proceeds to step S14, where it is determined whether or not the detection state of the first mode detection switch 71 is two-wheel drive mode, similarly to step S7. If this determination is YES, the process returns to step S2, but if NO, the throttle opening θ detected by the throttle sensor 82 is compared with a predetermined value (50') in step S15, and the determination is θ is 50. If the answer is NO, the process proceeds to step SI6, where the drive mode is set to four-wheel drive/high speed/center differential free mode (4HF). With this mode setting, the switching operation subroutine in step S13 is executed, and the switching operation is performed. And step S+
Step 51 until switching to the same mode (4HF) at 7.
6. Repeat S17 and switch to the first step S.
Return to 2. On the other hand, the determination in step SI5 is θ≧50°
If YES, the process advances to step S18 and the drive mode is set to 4-wheel drive/low speed/center differential lock mode (4L
Set to L). With this mode setting, the above step S
The switching operation subroutine at i3 is executed to perform the switching operation. Steps S18 and 319 are repeated until the mode is switched to the same mode (4HF) in step S19, and when the mode is switched, the process returns to the first step S2.

Therefore, in this embodiment, step S in the above flow
11, SI4 to S17 receive the output of the reverse switch 79, and when the transmission 3 is in the reverse state and the four-wheel drive state is in the four-wheel drive state, and the throttle opening θ is less than the predetermined opening, the center differential 2.6 is Control means 80 for controlling the 2/4 switching mechanism 38 so as to switch to the free state
is configured.

Therefore, in the embodiment described above, the throttle opening θ of the engine 1 is detected by the throttle sensor 78 while the vehicle is running, and a signal is output from the sensor 78 to the control unit 70.

In addition, the control unit 70 determines whether the transmission 3 is operated to the reverse state based on the presence or absence of the ON signal of the seven rehabilitation switches, and when it is in the non-reverse state (forward or neutral state), the The drive mode is switched to a predetermined drive mode in response to a switching operation of the 2/4 changeover switch 76 and the H/L changeover switch 77 by a person. That is, when the changeover switches 76 and 77 are operated, the motor 48 of the transfer changeover mechanism 49 is activated to rotate the drive shaft 46, and the cam groove 47a of the cylindrical cam 47 is rotated.
, 47b move, and the first and second shift rods 39.43 slide in the axial direction in conjunction with each other. The switching mechanism 25.38 is switched and maintained in the desired drive mode. For example, when the drive mode of the vehicle is two-wheel drive/high-speed mode (2H), the first switching mechanism 25 is in the high-speed position (PH), and the second switching mechanism 25 is in the high-speed position (PH). g38 are respectively positioned at the two-wheel drive position (P:), and the two-wheel drive state is maintained. In addition, in this two-wheel drive state, the remote freewheel machine (1) 50 is in a cut-off state, and the front axle shaft 6a.

6b only rotates, and the differential case of the front differential 5, the rear-wheel side output shaft 15 of the transfer 4 drivingly connected to the differential case, etc. are stopped, and the drive loss of the engine 1 due to their rotation can be suppressed.

In addition, 4 wheel drive / high speed / center differential free moto (4HF
), the first switching mechanism 25 is in the high speed position (P)-1),
The second switching mechanism 38 is in the four-wheel drive/center differential free position (
P4F) and are maintained in a four-wheel drive state with the center differential 26 free.

Furthermore, 4-wheel drive/high speed/center differential lock mode (4 wheel drive/high speed/center differential lock mode)
HL), the first switching mechanism 25 is in the high speed position (PH),
The second switching mechanism 38 is in the four-wheel drive/center differential lock position (
PAL) and are held in a four-wheel drive state with the center differential 26 locked.

In addition, in the drive mode 4-wheel drive/low speed/center differential lock mode (4LL), the first switching mechanism 25 is in the low speed position (
PL), and the second switching mechanism 38 is positioned at the four-wheel drive/center differential lock position (PJL). This allows the vehicle to be maintained at a low speed in the four-wheel drive state with the center differential locked.

In addition, if the drive mode is 4 in which the center differential 26 is locked,
There are two wheel drive modes: 4 wheel drive/high speed/center differential lock mode (4HL) or 4 wheel drive/low speed/center differential lock mode (4L L), and 2 wheel drive/high speed mode (2H).
), there is a large change in the drive state, so in order to avoid this, the mode is first switched via four-wheel drive/high speed/center differential free mode (4HF). Further, when switching from the four-wheel drive mode to the two-wheel drive mode, the second switching mechanism 38 of the transfer 4 is first switched to the four-wheel drive position, and then the remote freewheel mechanism 50 is switched to the connected state.

On the other hand, when the transmission 3 is switched to the reverse state by the output of the ON signal of the reverse switch 79 and the throttle opening θ is small (less than 50°), the drive mode is forcibly set to the four-wheel drive/high speed/center It is switched to differential free mode (4HF) and held fixed. That is, since the center differential 26 is in a free state when the transmission 3 is in the reverse state, the front and rear wheels 7a, 7b, 10a, 10
Even if the rotational speed difference between the wheels 7a and 7b is differentially adjusted and the front wheels 7a and 7b are steered at a large steering angle to change the direction of the vehicle, no braking phenomenon occurs due to the internal circulation torque in the drive system. Therefore, switching operation during reverse can be easily performed.

Furthermore, even during the same reverse mode, the throttle opening θ is 50
When a large engine output is required at a temperature greater than The mode can be switched to 4-wheel drive/low speed/center differential lock mode (4LL). This locked state of the center differential 26 eliminates loss of engine driving force from the slipping wheels 7a, 7b, 10a, 10b, making it possible to easily escape from the stuck state.

It goes without saying that the present invention can be applied not only to part-time four-wheel drive vehicles as in the above embodiment, but also to full-time four-wheel drive vehicles.

(Effects of the Invention) As explained above, according to the present invention, it is possible to detect that the transmission in a four-wheel drive vehicle having a transfer with a built-in center differential has been switched to the reverse state, and when the transmission is reversed, the center differential is set to the free state. By keeping it fixed, the difference in rotational speed between the front and rear wheels during reverse can be differentially adjusted by the free state of the center differential, even when the front wheels are steered at a large steering angle to change direction.
It is possible to avoid the braking phenomenon caused by the internally circulating torque in the drive system, and therefore it is possible to facilitate the switching operation when reversing.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of the present invention. Figure 2 and the following drawings show embodiments of the invention. Figure 2 is a schematic plan view showing the overall configuration of the drive system, Figure 3 is a diagram showing the configuration of the control system, and Figure 4 is a diagram showing the configuration of the control system.
FIG. 5 is a skeleton diagram showing the structure of the transfer, FIG. 5 is an enlarged perspective view showing the main parts of the transfer switching mechanism, and FIG. 6 is a flowchart showing the procedure of signal processing in the control unit. DESCRIPTION OF SYMBOLS 1... Engine, 3... Transmission, 4... Transfer, 7a, 7b...-Front wheels, 10a, 10b-... Rear wheels, 11... Power transmission path, 16... Sub-transmission mechanism,
25... First switching mechanism, 26... Center differential, 38
...Second switching mechanism (center differential switching mechanism), 39...
・First shift rod, 43...Second shift rod, 4
6... Drive shaft, 47... Cam, 48... Motor,
49... Transfer switching mechanism, 50... Remote freewheel mechanism, 70... Control unit, 71-74... Mode detection switch, 7... Reverse switch (reverse detection means), 80... ...
- Control means. Representative Patent Attorney Mae 1) Hiroshi (Hariki and 2 Yu) Figure 1 Figure 5

Claims (1)

[Claims] (1) A four-wheel drive vehicle that is equipped with a transmission in the middle of a power transmission path that transmits engine power to four wheels, a transfer with a built-in center differential, and a center differential switching mechanism that switches the center differential to a locked state. a reverse detection means for detecting that the transmission has been switched to a reverse state; and a center differential switching mechanism that receives an output of the reverse detection means and switches the center differential to a free state when the transmission is in the reverse state. 1. A control device for a four-wheel drive vehicle, comprising a control means for controlling the vehicle.