JP2559770B2 - 4-wheel drive vehicle - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an improvement of a so-called part-time four-wheel drive vehicle in which a wheel drive mode can be switched between a two-wheel drive mode and a four-wheel drive mode.

(Prior Art) Generally, in a part-time type four-wheel drive vehicle of this type, in a two-wheel drive mode, the rotation of idle wheels (non-drive wheels) whose transmission of driving force is stopped is caused by the rotation of the vehicle due to running of the vehicle. The gears of the differential mechanism between the wheels and the transfer device connected to the differential mechanism rotate, and a rotation loss causes a drive loss.

Therefore, a so-called freewheel device is conventionally known in order to eliminate such drive loss. That is, this freewheel device is disclosed in, for example, Japanese Patent Application Laid-Open No. 56-13.
As disclosed in Japanese Patent No. 5320, etc., one axle shaft corresponding to the output part of the differential mechanism between the idle wheels is axially divided into two parts, and a clutch mechanism for connecting / disconnecting power transmission between the divided parts is provided. In the two-wheel drive mode, the clutch mechanism is turned off to disconnect the differential mechanism from one of the wheels, so that the differential case and the propeller shaft connected to the differential case are rotated even if the idle wheel rotates during traveling. The gears of the transfer device are prevented from rotating to prevent the rotation of the idle wheel from being transmitted to the transfer device.

(Problems to be Solved by the Invention) In a four-wheel drive vehicle equipped with this freewheel device, the actual operating state (connected state or unconnected state) of the freewheel device is changed when the drive mode is switched.
Is detected by a sensor (free wheel position sensor), and the drive mode is switched based on the output signal of the free wheel position sensor. For example,
When switching from the two-wheel drive mode to the four-wheel drive center differential free mode, the freewheel device is connected based on the fact that the freewheel position sensor outputs a lock signal that is the connection state (locked state) of the freewheel device. Is determined, and according to the determination, the mode is switched to the four-wheel drive center differential free mode.

However, if the position sensor outputs a signal different from the actual operating state of the freewheel device due to a failure of the freewheel position sensor or its output system, the following problems occur. That is, for example, when a lock signal in the freewheel connection state is output from the freewheel position sensor, it is determined that the driver may switch to the four-wheel drive center differential free mode based on the output signal. However, in that case, if a failure or the like occurs in the above freewheel position sensor, the freewheel device is switched to the four-wheel drive center differential free mode even though the freewheel device is actually in the non-connection state (free state). Therefore, the power of the engine escapes from the free wheel device in the non-connected state, and the driving force cannot be transmitted to the wheels, and a countermeasure against it is desired.

The present invention has been made in view of the above circumstances, and an object thereof is to detect an abnormal state such as a failure of the above-described freewheel position sensor, and to specify a predetermined drive mode when the abnormality occurs. Therefore, even if an abnormality occurs in the freewheel position sensor, it is properly detected to ensure the traveling ability of the vehicle.

(Means for Solving the Problems) To achieve this object, the solution of the present invention is that the output signal of the freewheel position sensor is switched from the non-connection state of the freewheel device to the connection state in the drive mode. Is only when the two-wheel drive mode is switched to the four-wheel drive mode, and in other cases, the signal change is considered to be an abnormality of the position sensor. Among the modes, switching to the four-wheel drive center differential free mode is prohibited.

Specifically, the present invention includes a transfer device that has a center differential that distributes the power input to the input shaft to the front and rear wheels, and that can switch between a two-wheel drive state and a four-wheel drive state, and a floating device during two-wheel drive. The present invention is intended for a four-wheel drive vehicle that includes a freewheel device that is provided at an output portion of a wheel-side differential mechanism that serves as a wheel and that blocks power transmission between the differential mechanism and the wheel.

A freewheel position sensor for detecting the operating state of the freewheel device is provided.

Position sensor output detecting means for detecting that the output signal of the position sensor has changed from the non-connected state (free state) of the freewheel device to the connected state (locked state) is provided.

Furthermore, receiving the output of the position sensor output detection means,
When the output signal of the position sensor changes from the non-connection state of the freewheel device to the connection state in a state other than the switching of the transfer device from the two-wheel drive state to the four-wheel drive state, the center differential free state of the transfer device is set. A prohibition means for prohibiting the switching to is provided.

(Operation) With the above configuration, in the present invention, the operating state of the freewheel device is detected by the freewheel position sensor. Then, when the output signal of this position sensor changes from the non-connection state of the freewheel device to the connection state,
This is detected by the position sensor output detecting means, and the change of the output signal of the position sensor by the prohibiting means receiving the output of the detecting means is equal to or more than the switching of the transfer device from the two-wheel drive state to the four-wheel drive state. If it is determined that the position sensor has occurred, it is considered that the position sensor is in an abnormal state, and it is prohibited to switch the center differential in the transfer device to the free state. Therefore, it is prohibited that the freewheel device is switched to the four-wheel drive center differential free mode even when the freewheel device is not actually connected, so that the power does not escape from the freewheel device and the vehicle travels accordingly. The ability can be secured.

(Example) Hereinafter, the Example of this invention is described based on drawing.

FIG. 1 schematically shows a part-time four-wheel drive vehicle according to an embodiment of the present invention, where 1 is a vehicle body of the vehicle, 2 is an engine mounted in a so-called vertical position on a front portion of the vehicle body, and 3 is a vehicle. A manual transmission for shifting the output rotation of the engine 2,
A transfer device 6 is arranged on the rear side of the transmission 3, and the transfer device 6 has front and rear wheels 4 and 4 and front and rear wheels 5 and 5 which are idle wheels in the two-wheel drive mode, respectively. They are connected via differential mechanisms 35 and 36.

The transfer device 6 includes a transfer case 7 connected to a case 3a of the transmission 3 as shown in detail in FIG.
The input shaft 8 arranged on the same axis as the output shaft 3b, the front wheel side output shaft 9 arranged on the side of the input shaft 8 in parallel with the input shaft 8, and behind the input shaft 8 (in the figure On the right side, the input shaft 8 and the rear wheel side output shaft 10 arranged on the same axis are rotatably supported. An H / L switching mechanism 11 for switching the transmission ratio of the power transmitted from the engine 2 to the wheels 4 and 5 from the high speed mode to the low speed mode is provided at the front end of the input shaft 8, that is, the end on the transmission 3 side. It is arranged. The H / L switching mechanism 11 is rotatably supported on an input shaft 8 and a plurality of pinion gears which are spline-coupled to the input shaft 8 behind the sun gear 13 so as to rotate integrally therewith. A reduction gear mechanism 12 including a planetary gear mechanism having a pinion carrier 15 carrying 14, 14, ... And a ring gear 16 meshing with each pinion 14 is provided, and the ring gear 16 is a gear 16a formed on the outer peripheral surface thereof. It is fixed to the inner surface of the transfer case 7 so as not to rotate. On the other hand, a spline gear 13a is formed on the outer periphery of the front end portion of the sun gear 13, and a spline tooth portion 15a is formed on the inner periphery of the front end portion of the pinion carrier 15. A cylindrical member 17 whose front end is spline-coupled to the output shaft 3b of the transmission 3 in a rotationally integrated manner is arranged around the front end of the input shaft 8, and the sun gear 13 is provided on the outer peripheral surface of the rear end of the cylindrical member 17. A spline tooth portion 17a having the same diameter as that of the spline tooth portion 13a is formed, and the spline tooth portion 17a has an inner peripheral spline tooth portion 18a capable of meshing with the spline tooth portion 13a of the sun gear 13 at the rear end thereof. Is slidably and rotationally integrally spline-coupled, and the sleeve
A spline tooth portion 18b capable of meshing with the spline tooth portion 15a of the pinion carrier 15 is formed on the outer peripheral surface of the rear end of the pinion carrier 15. Then, the sleeve 18 is slid on the cylindrical member 17 so that the outer peripheral spline tooth portion 18b is attached to the pinion carrier 1.
5 on the spline teeth 15a or on the inner peripheral spline teeth 18
By selectively engaging a with the spline teeth 13a of the sun gear 13, the power transmission ratio is switched to the low speed mode or the high speed mode, and the sleeve 18 is moved to the front high speed position (P _H ) as shown by the solid line in the figure. When the outer peripheral spline tooth portion 18b is meshed with the spline tooth portion 15a of the pinion carrier 15, the output shaft 3b of the transmission 3 is directly connected to the transfer input shaft 8 via the pinion carrier 15 in a rotationally integrated manner. By transmitting the rotation of the output shaft 3b to the input shaft 8 without deceleration, the power transmission ratio is set to the high speed mode. On the other hand, when the sleeve 18 is positioned at the rear low speed position (P _L ) as shown by the phantom line and the inner peripheral spline tooth portion 18a is meshed with the spline tooth portion 13a of the sun gear 13, the transmission output shaft 3b through the sun gear 13, each pinion 14 and pinion carrier 15 transfer input shaft 8
Is transmitted to the vehicle to reduce the rotation thereof, so that the power transmission ratio is set to the low speed mode.

On the other hand, a planetary gear type center differential 19 is arranged at the rear end of the transfer input shaft 8. The sun gear 20 of the center differential 19 is rotatably supported on the input shaft 8,
The pinion carrier 22 that carries each pinion 21 is a sun gear
20 is spline-coupled to the rear input shaft 8
The ring gear 23 is rotatably coupled to the rear wheel output shaft 10.

A drive sprocket 24 is rotatably supported on the input shaft 8 on the front side of the center differential 19, and is disposed between the sprocket 24 and a driven sprocket 25 which is integrally rotatably connected to the front wheel output shaft 9. Is wound around a chain 26, and the rotation of the input shaft 8 is transmitted to the front wheel output shaft 9 by the chain 26.

Further, the sun gear 20 and the ring gear 23 of the center differential 19 are respectively extended forward, and a clutch hub 27 having a spline tooth portion 27a on the outer peripheral surface is rotatably connected to the front end of the extended portion of the sun gear 20. Meanwhile, ring gear
The extended portion of 23 is rotatably supported on the outer periphery of the extended portion of the sun gear 20, and the outer periphery of the extended portion has a spline tooth portion 2 having the same diameter as the spline tooth portion 27a on the outer periphery of the clutch hub 27.
3a is formed. In addition, the drive sprocket 24
Is extended rearward, and spline teeth 24a having the same diameter as the spline teeth 27a on the outer periphery of the clutch hub 27 are formed on the outer periphery of the extension. In addition, the clutch hub 2
7, a sleeve 28 is slidably connected to each spline tooth portion 27a, 23a, 24a of the ring gear 23 of the center differential 19 and the drive sprocket 24 at its inner peripheral spline tooth portion 28a. A shift fork 30 fixed to 29 is integrally moved and locked, and the shift rod 29 is integrally connected to a control rod 31 which is moved by an electric motor 32. And
Sliding the sleep 28 by the operation of the motor 32 switches the center differential 19 to the free state, its locked state, the two-wheel drive state or the four-wheel drive state, and the sleeve 28 is the front end four-wheel drive / center differential as shown by the phantom line. Free position (P _4F )
When it is positioned at, the clutch hub 27 and the drive sprocket 24 are rotationally and integrally connected to each other to set the four-wheel drive mode, and the center diff 19 is set to a free state by disconnecting the ring gear 23 of the center diff 19 and the sun gear 20. Also, when the clutch hub 27 and the drive sprocket 24 are positioned in the four-wheel drive / center differential lock position (P _4L ) in the middle between the front and rear, the clutch hub 27 and the drive sprocket 24 are integrally connected to each other in the four-wheel drive mode, and the center differential is set. The center differential 19 is locked by connecting the ring gear 23 of 19 and the sun gear 20 to each other. Further, when the sleeve 28 is positioned at the rear-end two-wheel drive position (P ₂ ) as shown by the solid line, the ring gear 23 of the center differential 19 and the sun gear 20 are connected to each other while the center differential 19 is in the locked state. Hub 27
A drive mode switching mechanism 33 is configured to release the connection between the drive mode and the drive sprocket 24 to set the drive mode to the two-wheel drive mode.

Incidentally, as shown in FIG. 2, the drive mode switching mechanism 33 is
The switching position of is detected by the drive mode switching detection switch 34 based on the moving position of the shift rod 29.

Front and rear wheel output shafts of the transfer device 6
1, 9 and 10 are connected to the front and rear differential mechanisms 35 and 36 via front and rear propeller shafts 64 and 65, respectively, as shown in FIG. The front differential mechanism 35 includes a housing 37 as shown in detail in FIG. 3, and a differential gear mechanism 38 is rotatably supported in the housing 37.
The gear mechanism 38 is spline-coupled to respective inner ends of a differential case 39 rotatably supported by a housing 37 and left and right axle shafts 46, 46 extending in the differential case 39 in the left-right direction (vertical direction in the drawing). A pair of opposing side gears 4
0,40, a pinion shaft 41 rotatably supported by the differential case 39, and a pair of opposed pinions 42,4 fixed integrally and rotatably on the pinion shaft 41 and engaged with the side gears 40.
A ring gear 43 composed of a bevel gear is fixed to the outer periphery of the differential case 39 so as to rotate integrally therewith. A drive pinion 44 is meshed with the ring gear 43, and the drive pinion 44 is a front wheel output shaft of the transfer device 6. 9 is drivingly connected to a front propeller shaft 64 connected to the front propeller shaft 9.

Further, in the front differential mechanism 35, an axle shaft 46 and the left front wheel 4 are disposed on an extension line of an output portion, for example, an axle shaft 46 on the left side (upper side in the figure).
A joint shaft 47 connecting the and is arranged concentrically, and a portion of the joint shaft 47 facing the axle shaft 46 is formed to have a smaller diameter than the other portions. On the other hand, the outer end (right end) of the axle shaft 46 is formed to have a larger diameter than the other portions, and the end of the small diameter portion of the joint shaft 47 is fitted to the end surface of the large diameter portion so as to be relatively rotatable. A fitting recess 46a is provided. A spline tooth 46b is formed on the outer periphery of the large diameter portion of the axle shaft 46.
The outer circumference of the small diameter part of the
A spline member 48 having a spline tooth portion 48a corresponding to b on the outer circumference is fixed integrally with the rotation. Further, a sleeve 49 is slidably splined between the spline members 48a and 46b of the spline member 48 and the spline teeth portion 46b of the axle shaft 46 so that the sleeve 49 can slide. The spline member 48 and the spline tooth portions 48a, 46b of the axle shaft 46 are switched to the meshing state or the non-meshing state by the front differential mechanism 35 and the front wheels 4, 4 so as to be able to transmit power (a locked state). Alternatively, the clutch mechanism 50 is configured so as to switch to a non-connection state (free state) for cutting off the power transmission.

A fork 51 is fixed to the sleeve 48 so as to move integrally therewith. The fork 51 is fixed to one end (left end) of a shift rod 52 slidable in the same direction (left and right direction) as the sliding direction of the sleeve 48. The other end (right end) of the shift rod 52 is connected to a diaphragm device 53 as an actuator. The diaphragm device 53 is provided with the shift rod 52
, And first and second two negative pressure chambers 55 and 5 defined by the diaphragm 54.
6, and each of the above negative pressure chambers 5 as shown in FIG.
Reference numerals 5 and 56 are connected to an intake pipe (not shown) of the engine 2 via negative pressure passages 57 and 58, respectively, so that the intake negative pressure is introduced. In addition, each of the negative pressure passages 5
7,58 are normally closed first and second solenoid valves 59,6
0 is provided for each of these solenoid valves 5
When the clutch mechanism 50 is operated by the opening / closing control of 9,60 and the first solenoid valve 59 is opened, the clutch mechanism 50 is disengaged and the left axle shaft connected to the front differential mechanism 35. 46 and
By disconnecting the connection with the joint shaft 47 that is connected to the left front wheel 4, only the side gears 40 and the pinion 42 of the differential mechanism 35 are rotated when the front wheels 4, 4 (idle wheels) rotate, and the differential gears are rotated. Mechanism 35
And a drive mode switching mechanism 33 of the transfer device 6, that is, a differential case 39 of the differential mechanism 35, a front propeller shaft 6 connected to the differential case 39 via a ring gear 43 and a drive pion 44.
4. The front wheel side output shaft 9 of the transfer device 6 drivingly connected to the front propeller shaft 64 and the driven sprocket 25, the chain 26 and the drive sprocket 24 are prevented from rotating while the second solenoid valve is turned on the contrary. 60
When the is opened, the clutch mechanism 50 is put in the connected state, and the free wheel device 61 is configured so as to connect the axle shaft 46 and the joint shaft 47 in a rotationally integrated manner.

In FIGS. 2 and 3, reference numeral 62 denotes a freewheel lock detection switch for detecting that the clutch mechanism 50 of the freewheel device 61 is in the connected state (locked state) based on the moving position of the shift rod 52. , 63 are free wheel free detection switches for detecting that the clutch mechanism 50 is in the disengaged state (free state) in the same manner, and the operating state of the free wheel device 61 is detected by these both switches 62, 63. A free wheel position sensor is configured.

The operation of the electric motor 32 for controlling the drive mode switching mechanism 33 and the first and second solenoid valves 59, 60 are controlled by a controller 66 as shown in FIG. The controller 66 includes three detection switches 34, 62, 63 described above.
And a mode changeover switch 67 (2/4 changeover switch) which is mounted on a vehicle instrument panel (not shown) or the like and is changed over by the driver when the 2/4 drive mode is changed over. Has been entered. Below, the motor 32 and solenoid valves 59, 6 of the controller 66
The operation control procedure for 0 will be described in detail with reference to FIG. In addition, in the steps of the flow of FIG.
"2H" indicates a two-wheel drive mode, "4HF" indicates a center differential free four-wheel drive mode, "4HL" indicates a center differential lock four-wheel drive mode, and "H" indicates
It indicates that 6H / L switching mechanism 11 of the transfer device is a high-speed mode H / L switching mechanism 11 positions 6 to the high speed position (P _H) is positioned in the high speed position (P _H).

First, in the first step S ₁ after the start, the drive mode switching detection switch 34, the free wheel lock detection switch 62, and the free detection switch 63 are
Reading each of the ON / OFF signal (freewheel position sensor), or the mode change-over switch 67 in the next step S ₂ is being turned ON, switching from two-wheel drive mode to the four-wheel drive mode has been requested determines whether, where (when the switching from the four-wheel drive mode to the two-wheel drive mode is requested) If the decision is NO, a step S ₃ to S ₁₁
Proceed to. That is, in step S _3, 2-wheel drive mode, it is determined whether it is ongoing, the process directly proceeds to step S ₉ when the determination is YES. Also, advances to step S ₄ when the determination is NO, outputs an operation signal for switching the electric motor 32 of the transfer device 6 to the four-wheel drive mode to the two-wheel drive mode, the in step S ₅ motor
32 is operated to switch the drive mode switching mechanism 33 from the four-wheel drive state to the two-wheel drive state, and in the next step S ₆ , the drive mode switching mechanism 33 is actually driven based on the output signal of the drive mode changeover detection switch 34. After confirming that the two-wheel drive position (P ₂ ) has been switched to, the motor 32 is stopped in step S ₇ after this confirmation. The driving mode switching after completion controls the clutch mechanism 50 of the freewheel device 61 by a first solenoid valve 59 in step S ₈ in the disconnected state (OFF state of the freewheel device 61), then step Continue to S ₉ . In this step S ₉ , based on the output signal of the freewheel lock detection switch 62, it is determined whether or not the freewheel device 61 is actually switched to the non-connection state (free state),
If YES is determined here, in a state other than the case where the drive mode is switched from the two-wheel drive mode to the four-wheel drive mode,
Since the output signal of the freewheel lock detection switch 62 has switched to the ON state (the connection state of the clutch mechanism 50),
When it is considered that there is something wrong with the switch 62,
After prohibit switching to the switching clogging center differential free four-wheel drive mode to the four-wheel drive / center differential free position of the driving mode switching mechanism 33 (P _4F) in S _10, the flow returns to the first step S _1. Further, when the decision in step S ₉ is NO, the process proceeds to step S _11, and the driving mode switching mechanism 33 to the two-wheel drive position (P _2), the flow returns to step S ₁ after holding the two-wheel drive mode .

On the other hand, when the decision in step S ₂ is YES (when the switching from the two-wheel drive mode to the four-wheel drive mode is requested), the process proceeds to step S ₁₂ to S _20. That is, in step S _12, 4-wheel drive mode, it is determined whether it is ongoing, it is when the determination is YES the process proceeds to step S _18. Further, when the determination is NO Step S ₁₃
Willing, the electric motor 32 of the transfer device 6 to output an actuation signal for switching from two-wheel drive mode to the four-wheel drive mode, the driving mode switching mechanism in step S ₁₄ is operated the motor 32 to the 33 switching from two-wheel drive state to the four-wheel drive state, in the next step S _15, the drive mode changeover detection driving mode switching mechanism 33 based on the output signal of the switch 34 is actually a four-wheel drive / center differential free position ( P
_4F ) or 4 wheel drive / center differential lock position (P _4L ) after confirming that it has been switched,
In S ₁₆ , the motor 32 is stopped, and in step S ₁₇ , four-wheel drive / center differential free position (P _4L ) or four-wheel drive /
The select signal for the center differential lock position (P _4L ) is output and the process proceeds to step S ₁₈ . In step S _18, determining whether switching to the four-wheel drive / center differential free position of the driving mode switching mechanism 33 (P _4F) (switching to the center differential free four-wheel drive mode) is being banned And here
When YES is determined, the driving mode switching mechanism in step S ₁₉
33 after fixing to the 4-wheel drive / center differential lock position (P _4L), also when it is determined that NO is a driving mode switching mechanism 33 in step S ₂₀ is the selected 4-wheel drive / center differential free position (P _4F ) or 4 wheel drive / center differential lock position (P _4L ), then the first step S ₁ respectively
Return to

Therefore, in this embodiment, the signal of the freewheel lock detection switch 62 (freewheel position sensor) is changed from the non-connection state of the freewheel device 61 to the connection state by steps S ₂ and S _{9 in} the above-described flow. The position sensor output detecting means 68 is configured to detect the.

Pursuant to the steps _{S 10, S 18, S 19} , receiving an output of said position sensor output detection unit 68, the freewheel lock detection in the state other than the switching from two-wheel drive state of the transfer device 6 to the 4-wheel drive Inhibiting means 69 is configured to inhibit switching of the center differential 19 in the transfer device 6 to the free state when the signal of the switch 62 changes from the non-connection state of the freewheel device 61 to the connection state.

Therefore, in the above embodiment, when the mode changeover switch 67 is switched to change the wheel drive mode from the four-wheel drive mode to the two-wheel drive mode, the drive mode switching in the transfer device 6 is performed by the operation of the electric motor 32. Mechanism 33 has 4-wheel drive / center differential free position (P
_4F) or positioned 4-wheel drive / center differential lock position from (P _4L) to two-wheel drive position (P _2), the transfer device 6 is switched to the two-wheel drive state. Then, when it is confirmed that the transfer device 6 is actually switched to the two-wheel drive state based on the output signal of the drive mode changeover detection switch 34, the first solenoid valve 59 is thereafter turned on, The free wheel device 61 is switched to the non-connection state (free state), whereby the connection between the front differential mechanism 35 and the right front wheel 4 is cut off, and the front wheels 4, 4 (idle wheels) rotate during traveling. However, the power transmission portion between the differential case 39 of the front differential mechanism 35 and the drive mode switching mechanism 33 of the transfer device 6 is stopped and held, and the drive loss due to the rotation can be reduced.

At that time, the operating state of the freewheel device 61 is detected by the freewheel lock detection switch 62, and when the output signal of the detection switch 62 indicates the connection state of the freewheel device 61, the change is the actual transfer device 6 Since it occurred under a condition that is not possible except for the switching from the two-wheel drive state to the four-wheel drive state, it is considered that an abnormal state such as a failure has occurred in the free wheel lock detection switch 62, and the transfer device It is prohibited to switch the drive mode switching mechanism 33 in 6 to the 4 wheel drive / center differential free position (P _4F ), and in the 4 wheel drive mode, it is always 4 wheel drive / center differential lock position (P _4L ).
Fixed to. Therefore, it is restricted that the freewheel device 61 is switched to the four-wheel drive center-diff free mode even though the freewheel device 61 is not actually connected, and the power does not escape from the freewheel device 61. It is possible to effectively secure the traveling ability of the.

Although the transfer device 6 is provided with the H / L switching mechanism 11 in the above embodiment, the present invention can be applied to a four-wheel drive vehicle equipped with a transfer device without the mechanism.

(Effects of the Invention) As described above, according to the present invention, the differential mechanism on the wheel side, which is an idle wheel during two-wheel drive, and the free wheel device that shuts off power transmission to the wheel, and the transfer device having the center differential are provided. In a part-time four-wheel drive vehicle, the output signal of the freewheel position sensor that detects the operating state of the freewheel device is different from that of the freewheel device when the transfer device switches from the two-wheel drive state to the four-wheel drive state. When the position sensor determines that the position sensor is in an abnormal state when the connection state changes from the non-connection state, and prohibits the switching of the center differential in the transfer device to the free state, the free wheel device actually operates. Be switched to 4-wheel drive center differential free mode despite being unconnected. It is possible to prevent the power from escaping from the freewheel device, so that it is possible to secure the traveling ability of the four-wheel drive vehicle when the freewheel position sensor is abnormal.

[Brief description of drawings]

The drawings show an embodiment of the present invention. FIG. 1 is a schematic plan view of a four-wheel drive vehicle, FIG. 2 is an overall configuration diagram of a control system, and FIG. 3 is a cross section showing a front differential mechanism and a freewheel device. 4 and 5 are sectional views of the transfer device, and FIG. 5 is a flow chart showing the operation flow of the switching diagram. 4 ... front wheel, 5 ... rear wheel, 6 ... transfer device, 8 ...
… Input shaft, 9 …… Front wheel output shaft, 10 …… Rear wheel output shaft,
19 …… Center differential, 32 …… Motor, 33 …… Drive mode switching mechanism, 35 …… Front differential mechanism, 50 ……
Clutch mechanism, 61-free wheel device, 62-free wheel lock detection switch, 63-free wheel free detection switch, 66-controller, 68-position sensor output detection means, 69-inhibition means.

Claims (1)

(57) [Claims] 1. A transfer device having a center differential for distributing the power input to an input shaft to front and rear wheels and capable of switching between a two-wheel drive state and a four-wheel drive state, and a wheel which becomes an idle wheel during two-wheel drive. Side-wheel differential mechanism, in a four-wheel drive vehicle provided with an output portion of the differential mechanism and provided with a freewheel device for cutting off power transmission between the differential mechanism and wheels, a freewheel position sensor for detecting an operating state of the freewheel device. And a position sensor output detecting means for detecting that the output signal of the position sensor has changed from the non-connection state to the connection state of the freewheel device, and the two wheels of the transfer device receiving the outputs of the position sensor output detection means. The output signal of the position sensor changes from the non-connection state of the freewheel device to the connection state in a state other than switching from the drive state to the four-wheel drive state. Four-wheel drive vehicle, characterized in that a prohibition means for prohibiting the switching of the free state of the center differential when changed.