JPH02120142A - Controller for four-wheel drive vehicle - Google Patents

Abstract

PURPOSE:To check any backlash noise in driving gears in an effective manner by controlling a 2/4 selector mechanism so as to be selected to a 4WD state when engine speed is less than the specified value and car speed is more than the specified value. CONSTITUTION:A four-wheel drive vehicle is provided with a transfer with a built-in 2/4 selector mechanism 38 selecting a driving state for wheels to a 2WD or 4WD state, in the midway of a power transmission path 11. In this case, there is provided with a driving state detecting means 79 which detects such a driving state that speed of an engine 1 is less than the specified value and car speed is more than the specified value. When the driving state like this is detected, the 2/4 selector mechanism 38 is controlled so as to be selected to the 4WD state by a control means 80. Mass in a driving system is increased by this selection to this 4WD state, whereby a large torque variation in the engine 1 is attenuated, thus control over any backlash noise in driving gears is promoted.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a control device for controlling a 2/4 switching mechanism in a so-called part-time four-wheel drive vehicle having a 2/4 switching mechanism.

(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, Japanese Patent Application Laid-Open No. 58-122229 discloses that in a part-time four-wheel drive vehicle that can switch the drive state between two-wheel drive state or four-wheel drive state, the engine rotational speed is When the engine speed changes at a predetermined gear position of the transmission, it is predicted that wheel slip is about to occur, and the system switches to four-wheel drive mode. , to prevent wheel slippage.

(Problem to be Solved by the Invention) Generally, when a vehicle is running, rotational fluctuations occur in the gears of the drive system due to fluctuations in the torque of the engine. It is well known that sound is generated. In particular, when the engine speed is low, the torque fluctuation per unit time becomes large, and when the gear position of the transmission is high, the engine speed and the wheel speed become close to each other. The rattle sound level increases. However, since such rattling noise is a source of noise and also has a negative effect on riding comfort, it is desirable to suppress it as much as possible.

The present invention has been made in view of the above points, and its purpose is to reduce the mass (
Focusing on the fact that the large mass (mass) is large and can attenuate fluctuations in the torque transmitted to the wheels, we developed a system that allows switching from a two-wheel drive state to a four-wheel drive state under predetermined driving conditions of the vehicle, as in the prior art described above. By doing so, it is possible to suppress an increase in the rattle noise level in the drive system.

(Means for Solving the Problems) In order to achieve the above object, the solving means of the present invention provides a solution when the engine speed of the vehicle is below a predetermined speed and the vehicle speed is above a predetermined value, or when the engine speed is a predetermined value. The system detects when the rotational speed is below the rotational speed and the gear position of the transmission is above a predetermined gear position, and switches from the two-wheel drive state to the four-wheel drive state in that operating state.

Specifically, as shown in FIG.
In the middle of the power transmission path 11 that transmits to 10a and 10b,
The drive state for wheels 7a, 7b, 10a, 10b is set to 2.
For a four-wheel drive vehicle equipped with a transfer 4 incorporating a 2/4 switching mechanism 38 that switches between a wheel drive state and a four-wheel drive state, when the rotation speed Esp of the engine 1 is below a predetermined value and the vehicle speed V is above a predetermined vehicle speed. A driving state detecting means 79 detects a certain driving state, and upon receiving the output of the detecting means 79, the 2/4 switching mechanism 38 is activated when the engine speed Esp is below a predetermined value and the vehicle speed V is above a predetermined vehicle speed. A control means 80 for controlling switching to a four-wheel drive state is provided.

Further, in the invention as set forth in claim (2), instead of the driving state in which the engine rotation speed Esp is below a predetermined value and the vehicle speed (■) is above the predetermined vehicle speed, the engine rotation speed Esp is below a predetermined value and the power transmission path 11 An operating state detecting means 79' is provided for detecting that the gear position of the transmission 3 disposed in the middle of the transmission gear is equal to or higher than a predetermined gear position. Big transmission 3
A control means 80' is provided for controlling the switching of the 2/4 switching mechanism 38 to a four-wheel drive state when the gear position of the vehicle is at a predetermined gear position or higher.

(Function) With the above configuration, in the invention according to claim (1), the engine rotation speed Esp becomes equal to or less than the predetermined value while the vehicle is running;
When the vehicle speed V becomes equal to or higher than a predetermined vehicle speed, the driving state is detected by the driving state detecting means 79, and the control means 80 receiving the outputs of the seven detecting means controls two of the transfers 4.
The /4 switching mechanism 38 is switched to the four-wheel drive state. In a driving state in which the engine speed Esp is below a predetermined value, the torque fluctuation of the engine 1 is remarkable.Moreover, when the vehicle speed V exceeds the predetermined vehicle speed, the torque fluctuation of the engine 1 directly affects the wheels IQa, 10b. However, since the mass of the drive system increases with the switch to the four-wheel drive state, the increase in mass causes large torque fluctuations in the engine 1. is damped and the wheel 7a.

7b, 10a, and 10b, thereby making it possible to effectively suppress rattling noise of the drive system gears.

Further, in the invention described in claim (2), the engine rotation speed E
When the operating state is such that sp is below a predetermined value and the gear position of the transmission 3 is above the predetermined gear position, this state is detected by the operating state detecting means 79', and the control means 80' switches the 2/4 switching mechanism 38. is switched to four-wheel drive mode.

In this operating condition, the large torque fluctuation of the engine causes the transmission 3
(wheels 10a, 10
Since this is a region where gear rattle noise is likely to occur due to transmission to gear b, the rattle noise level can be suppressed by switching to the four-wheel drive state.

(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 a part-time four-wheel drive vehicle according to an embodiment of the present invention, in which numeral 1 is an engine mounted vertically in the front of the vehicle body, and numeral 3 is an engine connected to the engine 1 via a clutch 2. A transmission 3 is connected for driving, and a transfer 4 is disposed on the rear side of the transmission 3. This transfer 4 is connected to the left and right front wheels 7 via a front propeller shaft 59, a front differential 5, and left and right front axle shafts 6a, 6b.
a, 7b, and the left and right rear wheels 10 via the rear propeller shaft 60, rear differential 8, and left and right rear axle shafts 9a, 9b.
a and 10b, respectively, and the clutch 2, transmission 3, transfer 4, front and rear propeller shafts 5
9, 60, differentials 5, 8 and axle shafts 6a, 6b, 9a
, 9b constitute a power transmission path 11 that transmits the power of the engine I to the four wheels.

As the detailed structure of the transfer 4 is shown in FIG. an intermediate shaft 13 arranged on the same axis on the right side), a front wheel side output shaft 14 arranged parallel to the side of the intermediate shaft 13 and whose front end is connected to the front propeller shaft 59; The rear wheel output shaft 15 is disposed on the same axis behind the rear wheel output shaft 15 and has a rear end connected to the rear propeller shaft 60.

A sub-transmission mechanism 16 (H/L switching mechanism) is disposed at the rear end of the input shaft 12 for switching the transmission ratio of power transmitted from the engine 1 to the wheels to a low speed state or a high speed state. has been done. This sub-transmission mechanism 16 includes an input shaft 1
2, and a plurality of pinions 18, 18 .・・・
- It consists of an idle gear mechanism having a pinion carrier 19 that carries the pinion 19, and a ring gear 20 that meshes with each of the pinions 18. The ring gear 20 has a clutch hub 21 rotatably supported on the intermediate shaft 13 behind the sub-transmission mechanism 16.
A sleeve 22 is splined to the outer periphery of the clutch hub 21 so as to be slidable in the axial direction. Further, at the front and rear positions of the clutch hub 21, first and second spline gears 23 and 24 that can mesh with the inner peripheral spline teeth of the sleeve 22 are provided.
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, the sleeve 22 is slid on the clutch hub 21, and the inner peripheral spline teeth are connected to the first or second spline gear 23. A first switching mechanism 25 is configured to selectively engage the wheels 24 to switch the power transmission ratio for the wheels 7a, 7b, 10a, and 10b to a low speed state, a high speed state, or a neutral state. That is, the sleeve 22 is positioned at the front low speed position (PL), and its spline teeth are connected to the first spline gear 23.
When the ring gear 20 is engaged, the ring gear 20 is stopped and regulated,
The rotation of the input shaft 12 is transmitted to the intermediate shaft 13 via the sun gear 17, each pinion 18, and the pinion carrier 19,
By decelerating the rotation during this time, the power transmission ratio is brought to a low speed state. On the other hand, move the sleeve 22 to the rear high speed position (P
When the input shaft 12 is positioned in position H) and engaged with the second spline gear 24, the input 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.
By transmitting the rotation of the input shaft 12 as it is to the intermediate shaft 13 without decelerating it, the power transmission ratio is brought to a high speed state. Furthermore, the sleeve 22 is moved to the front-rear center neutral position (PN
), when the input shaft 12 and the spline gears 23 and 24 are not engaged, the shafts 12 and 13 are separated from each other so that the rotation of the input shaft 12 is not transmitted to the intermediate shaft 13, and the shafts 12 and 13 are in a neutral state.

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 the center differential 26 is rotatably supported on the intermediate shaft 13, and a pinion carrier 29 supporting each pinion 28 is 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. 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.
The rotation on the intermediate shaft 13 side is transmitted to the front wheel side output shaft 14 by this. By sliding the sleeve 32 on the clutch hub 31, the inner spline teeth of the sleeve 32 are selectively engaged with the third or fourth spline gears 33, 34, respectively, thereby changing the center differential 26 into a free state or a locked state. Or a second switching mechanism 38 configured to switch between a two-wheel drive state or a four-wheel drive state (
2/4 switching mechanism).

That is, by this second switching mechanism 38, the sleeve 32
When positioned at the front end two-wheel drive position (P2),
Center differential 26 pinion carrier 29 and sun gear 27
The clutch hub 31 and the fourth
By separating the spline gear 34, that is, the drive sprocket 35, and cutting off the driving connection between the intermediate shaft 13 and the front-wheel output shaft 14, a two-wheel drive state is established. Also, move the sleeve 32 to the rear end 4-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 drivingly connected to the drive sprocket 35 (front wheel output shaft 14) and the rear wheel output shaft 15 via the center differential 26. In addition, the pinion carrier 29 and sun gear 2
7, the center differential 26 is brought into a free state. Furthermore, when the sleeve 32 is positioned at the front and rear intermediate four-wheel drive/center differential lock position (P4L), the clutch hub 31 and drive sprocket 35
and are rotationally connected to create a four-wheel drive state, and
The pinion carrier 29 is rotatably connected to the sun gear 27 to lock the center differential 26.

The first and second switching grooves 25.38 of the transfer 4
The structure for switching operation will be explained with reference to FIG. 5. In the figure, numeral 39 is a first shift rod that is slidably supported by the transfer case 4a, and a first shift fork 40 is attached to the front end (left end in the figure) of the first shift rod. , the rear end has a bin 41 on the outer periphery.
The cylindrical members 42 having protruding and recessed parts are each 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 disposed parallel to the first shift rod 39 and is slidably supported by the transfer case 4a.
A second shift fork 44 is immovably fixed to a portion of the shift rod 39 corresponding to the cylindrical member 42 by a boss portion 44a, and the shift fork 44 is connected to the second switching mechanism 38.
The pin 45 is movably engaged with the outer periphery of the sleeve 32, and a pin 45 is provided protruding from the boss portion 44a. Further, between the shift rods 39 and 43, a drive shaft 46 rotatably supported by the transfer case 4a is disposed parallel to the shift rods 39 and 43, and a cylindrical cam 47 is attached to the front end of the drive shaft 46. is fixed to a rotating body. The first shift rod 39 is attached to the front side of the outer periphery of the cam 47.
A first cam groove 47a that engages with the pin 41 of the cylindrical member 42 on the upper side and a second cam groove 47b that engages with the pin 45 of the second shift fork 44 on the second shift rod 43 on the rear side are spiral-shaped. is formed. The rear end of the drive shaft 46 is drivingly connected to an electric motor 48 disposed outside the transfer case 4a, as shown in FIG. The pin 41 in each cam groove 47a, 47b of the cam 47 is rotated at a rotation angle of
45 is moved in the axial direction while sliding, so that both shift rods 39, 43 are slid in relation to each other. Therefore, the shift rod 39, 43, pins 41, 45, cylindrical cam 47, drive shaft 46, and motor 48 switch the first and second switching mechanisms 25, 38 between two-wheel drive/high-speed mode (2H) and four-wheel drive. / High speed / Center differential lock mode (4HF), 4 wheel drive / High speed / Center differential lock mode (4HL), 4 wheel drive / Low speed / Center differential lock mode (4LL) and Neutral mode (N)
A transfer switching mechanism 49 is configured as a switching means that is configured to switch in combination with the switching state of different modes.

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,
In the divided portion, the rotation of the front wheels 7a and 7b, which are idle wheels (non-driving wheels) in the two-wheel drive state, is transferred to the transfer 4.
A remote freewheel mechanism 50 is provided to prevent transmission of the signal. 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 shaft 6
Disconnect a. A shift fork 52 for moving the sleeve 51 is engaged with the sleeve 51, and the shift fork 52
is attached to a shift rod 53 driven by a diaphragm device 54. Although not shown, the diaphragm device 54 has two negative pressure chambers partitioned by a diaphragm, each of which has a negative pressure passage 5.
5.56 to the intake passage of the engine 1. Each of the negative pressure passages 55 and 56 has a normally closed first
and second solenoid valves 57 and 58 are disposed, and when the first solenoid valve 57 is opened, intake negative pressure of the engine 1 is introduced into one negative pressure chamber, and the sleeve 51 is moved toward the axle shaft 6a. By moving the split portion away from the other split portion, the split portion of the front axle shaft 6a is separated, and rotation of the front wheels 7a, 7b is prevented from being transmitted to the transfer 4. 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 are configured to be operated and controlled by a control unit 70 containing a CPU. This control unit 70 includes
The detection signals of the first to fourth four mode detection switches 71 to 74, the detection signal of the vehicle speed sensor 75 that detects the traveling speed V (km/II) of the vehicle, and the 2/2 mode detection switches selectively operated by the driver. 4 changeover switch 76 and H/L changeover switch 77 and engine rotation speed Esp (rp
A detection signal from an engine rotation speed sensor 78 that detects 11) is input. The first mode detection switch 71
detects whether or not the second shift fork 44 in the transfer switching mechanism 49 is shifted to the two-wheel drive position (P2) in the two-wheel drive mode (2H), 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 (2nd) and outputs a signal. Furthermore, the third mode detection switch 73 selects two-wheel drive/high-speed mode (2H), four-wheel drive/high-speed/center differential free mode (4HF), four-wheel drive/high-speed/ This is a position switch that determines four drive modes: center differential lock mode (4HL) and four-wheel drive/low speed/center differential lock mode (4LL). 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 machine t1450.

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 turned on for a warning in step S4, and then the process returns to step S.

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 68 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 S11, '!' as in step S7 above! It is determined whether the detection state of the B1 mode detection switch 71 is the two-wheel drive mode or not, and when this determination is NO due to the four-wheel drive mode, the process proceeds to step S12, and the 2/4
The designated 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 2538 of the transfer 4 or the remote freewheel mechanism 50 are switched. Therefore, in step S+3, the process moves to a switching operation subroutine, and then returns to the first step S2.

In addition, in step S++ above, YE in two-wheel drive mode
If it is determined as S, the process proceeds to step S+4, where it is determined whether or not the detected vehicle speed V is within the range of 20 km/If≦V≦40 km/H. This judgment is V>20 or V>4
If the answer is No, the process proceeds to step S12, but 2
If 0≦V≦40 (YES), the process advances to step SI5, and it is determined whether the engine speed Esp is 1200 rp11 or less. Here ESp>1200
If the determination is NO, the process advances to step S12. On the other hand, if it is determined YES that Esp≦1200, the process proceeds to step SI6, and 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 513 is executed, and the switching operation is performed. Then, steps S+6.5I7 are repeated until the mode is switched to the same mode (4HF) in step SI7, and when the mode is switched, the process returns to the first step S.

Therefore, in this embodiment, step S in the above flow
14. With SI5, engine speed Esp is 1200
rpI11 (predetermined value) or less and vehicle speed V is 20
km/l! A driving state detecting means 79 is configured to detect a driving state that is greater than (a predetermined vehicle speed) and less than 40 km/It.

Also, step SI6. S+7 receives the output of the operating state detection means 79, and the engine rotation speed Esp is 12.
0Orpm or less, vehicle speed V is 20km/It≦V≦4
When the vehicle is at 0km/H, the second switching mechanism 38 (2/4 switching mechanism) is operated to set the center differential 26 in the 4-wheel drive state in order to set the drive mode to 4-wheel drive/high speed/center differential free mode (4HF). A control means 80 is configured to control switching to a free state.

Therefore, in the above embodiment, while the vehicle is running, the vehicle speed V is detected by the vehicle speed sensor 75, and the engine rotation speed Es
p is detected by the engine speed sensor 78, and the control unit 7 is sent from the sensor 75,78.
A signal is output to 0.

Then, the control unit 70 detects a driving state in which the detected vehicle speed V is 201ao/H≦V≦40 km/H and the engine rotation speed Esp is Esp≦1200 rpm. When the engine speed Esp becomes 120 Orpm or less, the torque fluctuation of the engine 1 becomes noticeable, and the vehicle speed V is 20km/H≦V≦4.
In a speed range of 0 km/II, torque fluctuations of the engine 1 are directly transmitted to the wheels, making it easy to generate rattling noise in the gears of the drive system. And when it is not in this operating state,
Since this is a region where there is no need to suppress the rattling noise of the drive system gears, the drive mode is switched to a predetermined drive mode in response to the driver's operation of the 2/4 changeover switch 76 and the H/L changeover switch 77.

That is, by switching the changeover switches 76 and 77,
The motor 48 of the transfer switching mechanism 49 operates, the drive shaft 46 rotates, and the cam grooves 47a, 4 of the cylindrical cam 47 rotate.
The pins 41° 45 engaged with the shift rods 7b move to cause the first and second shift rods 39° 43 to slide in the axial direction in conjunction with each other.
By this movement of the shift rods 39, 43, the first and second
The switching mechanism 25.38 is switched and maintained in the desired drive mode. For example, if the vehicle drive mode is 2 wheel drive/
When in the high speed mode (2H), the first switching mechanism 25
is located at the high speed position (PH), and the second switching mechanism 38 is located at the two-wheel drive position (P2), so that the two-wheel drive state is maintained. In addition, in this two-wheel drive state, the remote freewheel mechanism 50 is in a disconnected 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 (PH) and the second switching mechanism 25 is in the high speed position (PH).
The switching mechanism 38 is set to 4-wheel drive/center differential free position (P4
F), and the four-wheel drive state with the center differential 26 free is maintained.

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 (P+),
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), the second switching mechanism 38 is positioned at the four-wheel drive/center differential lock position (PAL). As a result, a low speed state is maintained in the four-wheel drive state of the center defroster.

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). Furthermore, 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, if the vehicle speed V is 20km/+1≦V≦40km/
I+, and engine speed Esp is Esp≦12
00 rpm, the driving mode is forcibly switched to the above four-wheel drive/high speed/center differential free mode (4HF) because the operating state is in a region where the rattling noise of the drive system gears is suppressed. The drive state is fixedly maintained at the four-wheel drive state. Therefore, the mass of the drive system increases with the above-mentioned change to the four-wheel drive state, and the large torque fluctuation of the engine 1 is attenuated due to the increase in mass, thereby effectively suppressing the rattling noise of the drive system gears. It is possible to reduce noise and improve riding comfort.

Incidentally, according to the inventor's experiments, the drive modes of a 4-wheel drive vehicle are 2-wheel drive/high-speed mode (2H), 4-wheel drive/high-speed/center differential free mode (4HF), and 4-wheel drive/high-speed/center differential lock. When switching to three types of modes (4HL) and determining the characteristics of the angular velocity fluctuation range of the rear propeller shaft, which transmits engine power to the rear driving wheels in a two-wheel drive state, with respect to the engine rotation speed Esp, the results are shown in Figure 8. The results shown are obtained. In that case, the engine accelerator was fully opened. The transmission was in the fourth gear position, and when the engine speed Esp was 800 rpIll, the vehicle speed V was 20 km/11, and when the engine speed was 1200 rp111, the vehicle speed V was 40 km/I+.

From this experimental result, the vehicle speed V is 20b/II≦■≦40k
m/+1, and the engine speed Esp is Esp≦
In the operating range of 1200 rpIll, the angular velocity fluctuation range of the rear propeller shaft is lower in the 4-wheel drive state than in the 2-wheel drive state, so it is possible to reduce the gear rattle noise level in the drive system in the above operating state. I see that it is possible.

In the above embodiment, the driving condition in which the rattle noise level in the drive system increases is determined when the vehicle speed V is 20km/II≦V≦40km/II≦V≦40km/
H, and the engine speed Esp is Esp≦120
Although the operating state is set at 0 rpm, other operating states may be used as shown in FIG.

That is, FIG. ), the CPU of the control unit 70
This figure shows the signal processing procedure performed by the following.

In this embodiment, although not shown, the control unit 7
In place of the detection signal of the vehicle speed sensor 75 in the above-described embodiment, a switching signal of a gear position detection switch for detecting the position of the gear position of the transmission 3 in the power transmission path 11 is input to 0.

Then, in the control unit 70, step 81
4', transmission 3 is activated based on the detection signal of the gear position detection switch.
It is determined whether the gear position has been changed to a high speed position such as 4th speed or higher, and if this determination is No, step S is performed.
12. On the other hand, if the answer is YES, the process proceeds to step SI5. Therefore, this step S
Due to I4' SIS, engine speed Esp is 1
An operating state detecting means 79' is configured to detect an operating state in which the speed is 20 Orpm or less and the gear stage of the transmission 3 is a high speed stage of the fourth speed or higher.

Also, step SI6. S+7 receives the output of the operating state detection means 79', and the engine rotation speed Esp becomes Esp.
The second switching mechanism 38 of the transfer 4 is configured to set the drive mode to 4-wheel drive/high speed/center differential free mode (4HF) when sp≦1200 and the gear is at a high speed of 4th speed or higher. A control means 80' is configured to control switching of the vehicle to a four-wheel drive state.

Therefore, in this embodiment, the engine speed E
When sp is Esp≦1200 and the gear position is at a high speed higher than 4th speed, the second switching mechanism 38 of the transfer 4 is switched to the four-wheel drive state, and the drive mode is set to four-wheel drive.
Set to wheel drive/high speed/center differential free mode (4HF). In this operating state, large torque fluctuations of the engine are transmitted to the rear wheels 10a, 10bl without being attenuated by the high speed gear of the transmission 3, and gear rattle noise is likely to occur. Since the vehicle is switched to the four-wheel drive state, the level of rattling noise can be lowered in the same manner as in the above embodiment, thereby reducing noise and improving ride comfort.

In each of the above embodiments, the drive mode is switched and maintained at 4-wheel drive/high speed/center differential free mode (4HF) in the driving state where the level of teeth rattling noise in the drive system should be suppressed. Drive/high speed/center differential lock mode (4HL
). In short, it is sufficient to switch and maintain the four-wheel drive state.

(Effects of the Invention) As explained above, according to the present invention, in a part-time four-wheel drive vehicle having a transfer with a built-in 2/4 switching mechanism, driving in which rattling noise is likely to occur in the gears of the drive system is achieved. state, that is, a driving state in which the engine speed is below a predetermined value and the vehicle speed is above a predetermined vehicle speed, or a driving state in which the engine speed is below a predetermined value and the gear position of the transmission is above a predetermined speed position. By switching the 2/4 switching mechanism to the 4-wheel drive state, the large torque fluctuations of the engine can be damped due to the increase in drive system mass caused by switching to the 4-wheel drive state, thereby reducing the rattling noise of the drive system gears. By effectively suppressing noise, it is possible to reduce noise and improve ride comfort.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of the present invention. 2 to 6 show one embodiment of the invention, FIG. 2 is a schematic plan view showing the overall configuration of the drive system, FIG. 3 is a diagram showing the configuration of the control system, and FIG.
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. FIG. 7 is a diagram corresponding to FIG. 6 in another embodiment. FIG. 8 is a characteristic diagram showing the angular velocity fluctuation characteristics of the rear propeller shaft with respect to changes in engine speed. 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 (2/4 switching mechanism), three...first shift rod, 43...second shift rod, 46...
Drive shaft, 47... cam, 48... motor, 49...
・Transfer switching mechanism (switching means), 50...Remote freewheel machine 4M, 70...Control unit, 71-74...Mode detection switch, 75.
...Vehicle speed sensor, 78...Engine speed sensor, 7
9.79'... Operating state detection means, 80.80'
...Control means, ■...Vehicle speed, Esp...Engine rotation speed.

Claims (2)

[Claims] (1) Four wheels equipped with a transfer mechanism with a built-in 2/4 switching mechanism that switches the drive state of the wheels between 2-wheel drive state and 4-wheel drive state, in the middle of the power transmission path that transmits engine power to the four wheels. In the driving vehicle, there is a driving state detection means for detecting a driving state in which the engine speed is below a predetermined value and the vehicle speed is above a predetermined vehicle speed; A control device for a four-wheel drive vehicle, comprising: control means for switching the 2/4 switching mechanism to a four-wheel drive state when the vehicle speed is higher than a predetermined vehicle speed. (2) A transmission is installed in the middle of the power transmission path that transmits the power of the engine to the four wheels, and a transfer that has a built-in 2/4 switching mechanism that switches the drive state of the wheels to a two-wheel drive state or a four-wheel drive state. In a four-wheel drive vehicle equipped with
operating state detection means for detecting an operating state in which the engine speed is below a predetermined value and the gear position of the transmission is above the predetermined speed; A control device for a four-wheel drive vehicle, comprising: control means for switching the 2/4 switching mechanism to a four-wheel drive state when the gear position of the transmission is at a predetermined gear position or higher.