JPS6127729A - Control device for four-wheel-drive speed change gear - Google Patents

Abstract

PURPOSE:To make it possible to eliminate a manual change-over operation from a two- wheel-drive condition to a four-wheel-drive condition by a driver, by enabling the change-over operation from the two-wheel-drive condition to the four-wheel-drive condition to be automatically carried out when any racing condition occures on the drive side during two-wheel-drive running. CONSTITUTION:An electronic control device 500 which automatically changes over the running condition of a vehicle from a two-drive-wheel condition to a four-wheel-drive condition in accordance with the running condition of the vehicle, is composed of an output shaft rotational speed sensor 510 for detecting the rotational speed of a speed meter driven gear 402, an actual vehicle speed detecting sensor 520 such as, for example, a Doppler radar for detecting an actual vehicle speed, an input/output port for receiving the outputs of both sensors and for delivering an output signal to a switch circuit 540, a comparator circuit 530 consisting of a CPU, a RAM and a ROM and the above-mentioned switch circuit 540. If any wheel on the drive side slips when the two- wheel-drive condition is selected through a manual change-over switch 550, the difference between an vehicle speed detected by the output shaft rotational speed sensor 510 and an actual vehicle speed detected by the actual vehicle speed sensor 520 exceeds a predetermined value, and therefore, the switch circuit 540 is energized to engage a clutch, thereby the four-wheel-drive condition is turned to be effective.

Description

[Detailed Description of the Invention] Field E] The present invention is a control device for a four-wheel drive transmission that automatically switches from a drive state of either front wheels or rear wheels to a four-wheel drive state according to driving conditions. Regarding.

[Prior Art] Conventionally, in a part-time four-wheel drive vehicle, if the drive wheels slip during two-wheel drive driving, the driver's experience has made it difficult to switch from two-wheel drive to four-wheel drive. Since this was done manually, it was difficult to generate appropriate driving force for all drivers. When the vehicle is idling, a switching lever must be operated to switch from two-wheel drive to four-wheel drive, making the switching operation difficult. In addition, in order to solve the above problem, a method has been proposed that detects the idling state of the front wheels based on the difference between the front and rear wheel rotation speeds and automatically switches from two-wheel drive to four-wheel drive. When the front wheels and rear wheels spin in the same way depending on the conditions, accurate control is difficult because the slip on the drive shaft cannot be detected.

[Object of the Invention] An object of the present invention is to detect slippage of the drive shaft during driving with the front or rear wheels and automatically switch from the front or rear wheel drive state to another drive state. The present invention provides a control device for a wheel drive transmission.

[Structure of the Invention] A control device for a four-wheel drive transmission according to the present invention includes a transmission;
A four-wheel drive switching device that can switch between wheel drive and four-wheel drive;
In a control device for a four-wheel drive transmission, the control device includes an electronic control device that inputs vehicle running conditions, and a shift control device that controls the transmission and a four-wheel drive switching device, wherein the shift control device Alternatively, the vehicle is configured to include means for detecting slippage of one of the rear wheels in a two-wheel drive state, and to switch to a four-wheel drive state when the slippage exceeds a certain level.

[Effects of the Invention] The four-wheel drive transmission control device of the present invention having the above configuration has the following effects.

B) Accurately senses the idle state of the drive shaft when driving in two-wheel drive with the front or rear wheels, automatically selects and drives the four-wheel drive state, and generates appropriate driving force. can.

(Example) When the drive shaft is idling when driving in two-wheel drive, the system automatically selects and drives from two-wheel drive to four-wheel drive, so the driver is not bothered. Freed from manipulation.

[Embodiment] A control device for a four-wheel drive transmission according to the present invention will be described based on an embodiment shown in the drawings.

Figure 1 is a schematic diagram of a main transmission and a four-wheel drive sub-transmission of a known 4-speed automatic transmission with three forward speeds and one reverse speed, and Figure 2 is a schematic diagram of a four-speed automatic transmission with three forward speeds and one reverse speed.
The cross section of the sub-transmission for wheel drive is very rough.

1 is a main transmission which is an automatic transmission; 10 is a four-wheel drive sub-transmission connected to the rear part of the main transmission 1 (right side in Figure 2); 2;
3 is the output shaft of the main transmission 1 and the input shaft of the auxiliary transmission eJ10; 3 is the first output shaft of the auxiliary transmission 10 arranged in series behind the input shaft 2 (right side in FIG. 2); 110 is a governor valve 1c fixed to the input shaft 2; 4 is a planetary gear set; a sun gear 41 spline-fitted to the rear of the input shaft 2; and a planetary gear 42 meshing with the sun gear 41.
, a ring gear 43 that meshes with the planetary gear 42, and a carrier 44 that rotatably holds the planetary gear 42 and is connected to the tip of the first output shaft 3 of the sub-transmission 10. 5 is a brake for engaging the ring gear 43 with the transformer 71 case 94, and 50 is the oil pressure of the brake 5, which is composed of a cylinder 18A formed in the transfer case 18 and a piston 51 installed in the cylinder 18A. It's a servo. 1 is carrier 44
This clutch is operated by a hydraulic servo 70, which is composed of a cylinder 11 connected to a cylinder 11 and a piston 72 installed in the cylinder 71.The clutch is arranged on the gear transmission side of the planetary gear set 4, and is connected to the sun gear 41 and the carrier. 4
4. 8 is a clutch for connecting and connecting the first output shaft 3 connected to the carrier 44 and the sleeve 9 connected to one sprocket 12 of the transmission mechanism for driving the second output shaft 17 of the auxiliary transmission 10 to be described later; A hydraulic servo 80 is composed of a cylinder 81 welded to a sleeve 9 rotatably held within the transfer cases 19 and 20, and a piston 82 mounted within the cylinder 81. 17 is a second output shaft of the sub-transmission 10 arranged parallel to the first output shaft; 14 is a sprocket 12 that is spline-fitted to the sleeve 9; and a sprocket 15 that is spline-fitted to the second output shaft 17. and a transmission mechanism consisting of a chain 16 stretched between these sprockets.

Inside the extension housing 400 at the rear of the sub-transmission 10 (on the right side in the figure) is a speedometer drive gear 401 provided on the output shaft to detect the rotational speed of the output shaft 3.
A speedometer drive gear 402 driven by the speedometer drive gear 401 is provided.

A parking gear 73 is provided around the outer circumferential side of the hydraulic cylinder 11 of the clutch 7, and when the shift lever of the automatic transmission is selected to the parking position, a pawl 74 engages with the parking gear 73 to fix the first output shaft 3. do.

90 is the oil pan of the automatic transmission, 200 is the sub-transmission 10
Clutch 1.8 and brake 5 hydraulic servo 70.
A hydraulic control device supplies and discharges hydraulic pressure to and from 80 and 50, and 92 is an oil pan of the hydraulic control II device 1200. Pressure oil supplied to the hydraulic servos 70.80 and 50 of the clutch 7.8 and the brake 5 is supplied from the oil pan 90 to the hydraulic control device 200 via a pipe 95 attached to the automatic transmission case 93 and transfer case 94. guided through.

This auxiliary transmission 10 is attached to an automatic transmission 1fiT mounted on an internal combustion engine E of a vehicle, as shown in FIG.
The output shaft 3 is connected to a rear wheel drive propeller shaft C,
The second output shaft 17, which is the other output shaft, is used while being connected to the propeller shaft B for driving the front wheels.

During normal driving, the line pressure supplied to the hydraulic control device of the automatic transmission is supplied to the hydraulic servo 70 to engage the clutch 7, and the hydraulic servos 50 and 80 are discharged to release the brake 5 and clutch 8. As a result, the sun gear 41 and carrier 44 of the planetary gear set 4 are connected, and power is transmitted from the input shaft 2 to the first output shaft 3 for rear wheel drive at a reduction ratio of 1, resulting in a two-wheel drive ratio for the rear wheels. At this time, the power from the input shaft 2 is transmitted from the carrier 44 to the first output shaft 3 via the clutch 7 without going through the gears 41, 42, 43, so no load is applied to the tooth surfaces of each gear. ,
Gear life increases. If 4-wheel drive is required during this 2-wheel drive mode, operate the manual shift lever or switch located on the driver's seat, etc., and activate the hydraulic control system @200 of the sub-shift @io. When line pressure is gradually supplied to the hydraulic servo 80 and the clutch 8 is smoothly engaged, the first output shaft 3 and the sleeve 9 are connected.
Power is also transmitted to the front wheels via the transmission mechanism 14, second output shaft 17, and propeller shaft B, and the power is transmitted from the input shaft 2 to the first output shaft 3 for driving the front wheels and the second output shaft 17 for driving the rear wheels at a reduction ratio of 1. A four-wheel drive ratio is obtained in which transmission is performed.

When an increase in output torque is required, such as on a steep slope during four-wheel drive, the hydraulic pressure to the hydraulic servo is controlled by the inhibitor valve 240 and the downshift timing valve 260, gradually supplying line pressure to the hydraulic servo 50 and appropriate The hydraulic pressure of the hydraulic servo 70 is discharged at the appropriate timing, the brake 5 is gradually engaged, and the clutch 7 is smoothly released. As a result, sun gear 41 and carrier 44 are released, ring gear 43 is fixed, and the power is decelerated from input shaft 2 via sun gear 41, planetary gear 42, and carrier 44 to first output shaft 3 and second output shaft. 17, and a four-wheel drive ratio state with large torque is obtained. Table 1 shows the engagement and disengagement of the brake 5, clutches 7 and 8 of the sub-shift ll110 and the running state of the vehicle.

Table 1 In Table 1, ◯ indicates the engaged state of the friction engagement element, and × indicates the released state. The reduction ratio λ is the ratio of the number of teeth between the sun gear 41 and the ring gear 43 of the planetary gear mechanism, and the value of the reduction ratio is the reduction ratio −(1+λ)/λ−3 when λ is 0.5.
, 0.

FIG. 4 shows a hydraulic control system for a four-wheel drive automatic transmission.

Reference numeral 100 in the figure is an example of a main transmission hydraulic control device of a known automatic transmission with three forward speeds and one reverse speed.
03, the oil pressure is regulated to a predetermined oil pressure (line pressure), and the oil passage 10
Guided by 4. Pressure oil guided to oil passage 104 is guided to 1-2 shift valve 106 and 2-3 shift valve 107 via manual valve 105.

A throttle valve 108 generates oil pressure (throttle pressure) in an oil passage 109 according to the throttle opening degree.

110 is a governor valve, which has oil pressure (governor pressure) depending on the vehicle speed.
is occurring in the oil passage 111.

The 1-2 shift valve 106 and the 2-3 shift valve 107 are
Oil passage 112.1 in relation to the magnitude of the throttle pressure and governor pressure supplied from oil passage 109 and oil passage 111.
13 and 114, and controls the supply and discharge of pressure oil to the hydraulic servos CI, 02, B1, B2, and B3 of the clutch and brake.

In this embodiment, at the first forward speed, the hydraulic servo C
Pressure oil is supplied to 1, and at the second forward speed, hydraulic servo C
Pressure oil is supplied to hydraulic servos C1, C2, and B2 during the third forward speed, and pressure oil is supplied to hydraulic servos C2 and B3 during reverse movement.

The sub-transmission hydraulic control device 200 of the sub-transmission 10 includes a first solenoid valve 210, a second solenoid valve 220, a switching valve 230, an inhibitor valve 240, and a drainage path for direct coupling engagement pressure via the inhibitor valve 240. a first oil passage 201 that connects to a frictional engagement element for direct connection to a downshift timing valve 2601 provided in 201, that is, a hydraulic servo 70 of a clutch 7;
Hydraulic servo 5 for deceleration frictional engagement element, ie brake 5
0, a third oil path 203 that connects to the hydraulic servo 80 of the four-wheel drive friction damage element, that is, the clutch 8, and a fourth oil path that connects the predetermined oil chambers of the switching valve 230 and the inhibitor valve 240. Check valves 310.320.33 provided in the oil passage 204 and the 1.2.3 oil passage, respectively.
0, line pressure oil passage 104 and orifice 340, 35
It is composed of an oil passage 205 for the first solenoid pressure and an oil passage 206 for the second solenoid pressure.

The 1.2 solenoid valves 210 and 220 have a moving core 211.221 and a solenoid 212.222, respectively.
, spring 213.223, opening 214.224,
Consists of oil drain port 215.225, solenoid 212.2
When 22 is energized, the moving core 211.221 is moved upward in the drawing to open the opening 214.224, and the pressure oil in the oil passage 205.206 separated from the line pressure oil passage 104 by the orifice 340.350 is drained. Ejected from 215.225. '/L//When the id 212.222 is de-energized, the moving core 211.221 is
13. The opening 214 is moved downward in the drawing by 223,
224 is opened to generate high-level solenoid oil pressure (line pressure) in oil passages 205 and 206.

The inhibitor valves 240 include three first and second valves from the bottom in the figure.
, a third spool 241, 242, 243, and the third spool 241 has a sleeve-like land 245 with a spring 244 on its lower end and two lands 246.2.
47, a lower end oil chamber 248, and a sleeve-shaped land 245.
and an intermediate oil chamber 249 between lands 246 and 247.
250, an oil chamber 251 between the first spool 241 and the second spool 242, an oil chamber 252 between the second spool 242 and the third spool, and an upper end oil chamber 253 are formed. In the inhibitor valve 240, when the first spool 241 is set upward in the drawing, the lower end oil chamber 248 communicates with the governor pressure oil passage 111 via the oil port 254A of the sleeve-shaped land, and the intermediate oil chamber 249 communicates with the line pressure. Oil passage 104 and second oil passage 20
2, the intermediate oil chamber 250 constantly communicates the first oil passage 201 and the drain oil passage 256, and when the first spool 241 is set downward in the figure, the lower end oil chamber 248 is connected to the oil port of the sleeve-shaped land. 254A, the intermediate oil chamber 249 communicates with the second oil passage 202 and the oil drain port 255, and the intermediate oil chamber 250 communicates with the line pressure oil passage 104 and the first oil passage 201. ing. In addition, the oil chamber 251 is always connected to the governor pressure oil passage 11.
1, the oil chamber 252 is always in communication with the fourth oil passage 204, and the upper end oil chamber 253 is always in communication with the oil passage 206.

The switching valve 230 has a spool 231 with a spring 232 installed in front and three lands at the bottom in the drawing, and includes, from the bottom in the drawing, a lower end oil chamber 233, a first intermediate oil chamber 234, a second intermediate oil chamber 235, An upper end oil chamber 236 is formed. In the switching valve 230, when a high level solenoid pressure is applied to the upper end oil chamber 236 to which the first solenoid pressure oil passage 205 is connected, the spool 231 moves downward in the drawing, Line pressure oil passage 104 and third oil passage 2
03 is connected to supply line pressure to the hydraulic servo 80 of the clutch 8, and the fourth oil passage 204 and the oil drain port 237 having an orifice 239 are communicated via the first intermediate oil chamber 234, and the inhibitor valve is When the pressure in the oil chamber 252 is exhausted and the solenoid pressure applied to the upper end oil chamber 236 changes to a low level, the spool 231 is moved upward in the drawing by the spring 232, and line pressure oil is released through the first intermediate oil chamber 234. The passage 104 and the fourth oil passage 204 are connected to supply line pressure to the oil chamber 252 of the inhibitor valve, and the second intermediate oil chamber 2
35, the third oil passage 203 and drain oil r:+238 are communicated with each other, and the pressure of the hydraulic servo 80 is discharged.

The downshift timing valve 260 has a spool 261 provided with a spring 262 and two lands in the lower part of the drawing, and includes a lower end oil chamber 263, an intermediate oil chamber 264, and an upper end oil chamber 265 from the lower part in the drawing. has been done. In the downshift timing valve 260, a lower end oil chamber 263 is always in communication with the deceleration oil passage 202, an upper end oil chamber 265 is always in communication with the line pressure oil passage 104, and an intermediate oil chamber 264 is always in communication with the drain oil passage 207 and It communicates with an oil drain port 266 provided with an orifice 267 for slowly discharging pressure, and also communicates with an oil drain port 268 for quickly discharging pressure when the spool 261 is set upward in the figure. In addition, spool 261
is set upward in the figure when the line pressure applied to the upper end oil chamber 265 is less than the set value (that is, the throttle opening is small) and is weaker than the spring load of the spring 262, or when the lower end oil chamber 263 is applied with a brake. This is when the engagement pressure of 5 is introduced.

Operate the manual shift in the driver's seat to select H2 or H4, □
Or, when the L4 range is set, the 1.2 solenoid valve 210.22
0 is ON and OFF controlled, and each frictional engagement element is operated by hydraulic oil selectively sent from the hydraulic control device 200 of the sub-transmission 1@10 to each hydraulic servo 50, 70.8p, and the sub-transmission 10 is each gear change state (1" 2 or H4 or above,
4). Furthermore, when the first solenoid valve 210 is turned on due to the hydraulic circuit configuration as described above, the sub-transmission 10
is set to H2.

The operation of solenoid valves 210 and 220 is as shown in Table 2. ON means energized, and OFF means not energized.

Zarani A is the shift position of sub-transmission 1io, B is sub-transmission 1
This is a gear shift state of 0.

Table 2 The operation of the sub-transmission 10 in each shift setting range will be explained.

(A>When the shift position is in the H2 range, it is determined that there is no slippage in the drive wheels, and the sub-transmission 10 is in H2 (two-wheel drive state), the first solenoid valve 210 → ON the second solenoid valve 220 → Since it is OFF, the line pressure is transferred from the oil passage 104 to the orifice 34.
0 to the oil passage 205, but is drained by the energized first solenoid valve 210, and is drained from the upper end oil chamber 236.
Therefore, in the switching valve 230, the spool 231 is set upward in the drawing by the spring 232, and the line pressure is applied to the oil chamber 252 through the oil passage 104, the oil chamber 234, and the fourth oil passage 204, and the inhibitor valve second spool 242 of
And the first spool 241 is set at the lower side in the figure. Therefore, the line pressure is
01 and a check valve 310 to the hydraulic servo 70 of the clutch 7.

Further, the oil pressure of the hydraulic servos 80 and 50 is drained from oil drain ports 238 and 255, respectively. Therefore, the sub-transmission 10 becomes H2 (two-wheel drive directly connected state).

(B) If the shift position is in the H2 range and it is determined that slippage has occurred in the drive wheels, or if the shift position is in the H4 range and the sub-transmission 10 is in H4 (4-wheel drive direct connection state), the first The solenoid valve 210 → OFF and the second solenoid valve 220 → OFF, so the line pressure is transferred from the oil passage 104 to the orifice 34.
0 to the oil passage 205, but the first solenoid valve 2
10 is de-energized, the oil is output to the upper end oil chamber 236, and the spool 231 of the switching valve 230 is set to the lower side in the figure. Therefore, the line pressure is the oil passage 104, the second intermediate oil chamber 23
5. The oil is introduced into the hydraulic servo 80 of the clutch 8 via the third oil passage 203 and the check valve 330. On the other hand, the line pressure is also guided from the oil passage 104 through the orifice 350 to the oil passage 206, but since the second solenoid valve 220 is de-energized, it is output to the upper end oil chamber 253, and the inhibitor valve 240 is , first spools 243, 242, and 241 are set at the bottom in the figure.

Therefore, line pressure is introduced into the hydraulic servo 70 of the clutch. Further, the oil pressure of the hydraulic servo 50 is drained from the oil drain port 255. Therefore, the sub-transmission 10 becomes H4 (four-wheel drive directly connected state).

(C) When the shift position is in the L4 range, the vehicle speed is above the set value, and H4 (four-wheel drive direct connection state) is selected, the first solenoid valve 210 → OFF and the second solenoid valve 220 - +ON are turned on, so the line pressure is Orifice 34 from oil passage 104
0 to the oil passage 205, but the first solenoid valve 2
10 is not energized, the upper end oil chamber 236 is inputted, and the switching valve 230 is set so that the spool 231 is positioned at the lower side in the figure. Line pressure is therefore introduced into the hydraulic servo 80 of the clutch 8. On the other hand, line pressure is also guided from the oil passage 104 through the orifice 350 to the oil passage 206, but is drained by the energized solenoid valve 220 and is not input to the upper end oil chamber 253 of the inhibitor valve 240. Also oil chamber 25
No line pressure is input to 2 either. Since the governor pressure is input to the oil chamber 251 here, the second and third spools 24
2.243 moves upward in the drawing, and since the governor pressure is above the set value, the spring load of the spring 244 is overcome and the first spool 241 is set downward in the drawing. Line pressure is therefore introduced into the hydraulic servo 70 of the clutch 1. Further, the oil pressure of the hydraulic servo 50 is drained from the oil drain port 255. Therefore, the sub-transmission 10 becomes H4 (four-wheel drive directly connected state).

(D) When the shift position is in the L4 range, the vehicle speed is below the set value, and the vehicle is in L4 (4-wheel drive deceleration state), the first solenoid valve 210 → OFF and the second solenoid valve 220 → ON, so the line pressure is Orifice 34 from oil passage 104
0 to the oil passage 205, but the first solenoid valve 2
10 is not energized, the upper end oil chamber 23G is inputted, and the switching valve 230 is set so that the spool 231 is positioned downward in the figure. Line pressure is therefore introduced into the hydraulic servo 80 of the clutch 8. On the other hand, line pressure is also guided from the oil passage 104 through the orifice 350 to the oil passage 206, but is drained by the energized solenoid valve 220 and is not input to the upper end oil chamber 253 of the inhibitor valve 240. Also oil chamber 25
Do not input line pressure to 2 either. Since the governor pressure is input to the oil chamber 251 here, the 2.3rd spool 242.2
43 moves upward in the figure, and since the governor pressure is below the set value, the first spool 241 is held in the upward position GCmR in the figure by the force of the spring 244, and enters the lower end oil chamber 248 through the cuff 254A of the sleeve. Governor pressure input.

Therefore, line pressure is introduced to the hydraulic servo 50 of the brake 5 via the oil passage 104, the oil chamber 249, the second oil passage 202, and the check valve 320. The oil pressure of the hydraulic servo 70 is controlled by the direct connection oil passage 201, the second intermediate oil chamber 250, and the drain oil passage 2.
07. Middle oil chamber 2 of downshift timing valve 260
64 and drains from drain ports 266 and 268. Therefore, the sub-transmission 10 becomes L4 (four-wheel drive deceleration state).

Also, the first spool 241 of the inhibitor valve 240 is connected to the oil chamber 2.
Since the areas of the upper and lower end surfaces facing the oil chamber 51 and the lower end oil chamber 248 are the same, when the governor pressure is introduced into both the oil chamber 251 and the lower end oil chamber 248 by moving upward in the figure.

Even if the governor pressure (vehicle speed) increases, the spring 244 does not move downward as shown in the figure, unless the manual shift is set to the H2 range or H4 range and line pressure is introduced into the oil chamber 252 or the upper end oil chamber 253. The load remains set at the upper position shown in the diagram. Therefore, manual shift is L4
Once the vehicle speed (governor pressure) is set in the range and becomes 14 below a predetermined value, L4 is maintained even if the vehicle speed (governor pressure) increases.

A shift control device for a four-wheel drive automatic transmission will be explained based on the block diagram and circuit diagram shown in FIGS. 5 and 6.

The electronic control device 500, which automatically switches from a two-wheel drive state to a four-wheel drive state depending on the driving situation, detects the rotation speed of a speedometer driven gear 402 (in FIG. 2) provided in the extension housing 400. An output shaft rotation speed sensor 510, an actual vehicle speed detection sensor 520 that detects the actual vehicle speed using a Doppler radar, etc., an input/output port that is an input port from these and an output port to the switch circuit 540, and a central processing unit. bag mcp
u, a comparison circuit 530 consisting of a random access memory RAM and a read-only memory ROM, and a switch circuit 540 that operates in response to the output of the comparison circuit 530.

FIG. H7 shows a flowchart illustrating the operation of the comparison circuit 530.

First, the rotation speed of the speedometer driven gear 402 is read from the output shaft rotation speed sensor 510 (531
), the rotation speed read in (531) is converted into vehicle speed (■1) (532). Next, the actual vehicle speed (vl) is read from the actual vehicle speed sensor 520 (533).

It is determined whether the difference between the vehicle speed (■1) converted from the rotation speed of the speedometer driven gear 402 and the actual vehicle speed (vl) is greater than or equal to a set value (534). YES (Vehicle speed (
vl) and the actual vehicle speed (vl)>, the manual changeover switch 550 is set to H in the switch circuit 540.
Provide support so that the 2 (two-wheel drive) position and the solenoid valve 210 are de-energized (535), and then return. If No (when the difference between the vehicle speed (vl) and the actual vehicle speed (vl) is less than the set value), support is provided to the switch circuit 540 so that the 112 position of the manual changeover switch 550 and the solenoid valve 210 are energized. ku'536)
, then return.

It is provided at the shift position of the auxiliary transmission 10, and is connected to the storage battery 6 of the vehicle.
When the manual changeover switch 550 connected to 20 selects H2 (2-wheel drive 1Ill), the solenoid valve 210
is energized by the storage battery 620, releases the clutch 8,
The vehicle is in two-wheel drive. At this time, if a wheel on the drive shaft slips and the difference in vehicle speed detected by the output shaft rotation speed sensor 510 and the actual vehicle speed detection sensor 520 exceeds a predetermined value, the switch circuit 540 is activated and the solenoid valve 210 is activated. Then, the storage battery 620 is de-energized, the clutch 8 is engaged, and the vehicle is placed in a four-wheel drive state.

The set value of the difference in vehicle speed is set to a value larger than the difference that occurs when turning when the drive wheels of the vehicle are not slipping: to avoid a difference in driving force when turning.

In this example, a hydraulic control device was used as the speed change control device, but
In addition, the present invention may be applied to an automatic transmission that uses an electromagnetic magnet or the like to electrically operate a fork shifter that changes gears in a transmission having a subshaft such as a synchronous mesh type or a constant mesh type transmission. Further, the set value of the difference in vehicle speed may be set according to the steering angle of the steering wheel.

[Brief explanation of drawings]

Fig. 1 is a skeletal diagram of a four-wheel drive automatic transmission, Fig. 2 is a sectional view of a four-wheel drive sub-transmission, Fig. 3 is a schematic diagram showing the vehicle power transmission system, and Fig. 4 is a forward Automatic gear shifting 1←
FIG. 5 is a block diagram of the transmission control device, FIG. 6 is an electric circuit diagram of the transmission control device, and FIG. 7 is a flowchart showing the operation of the comparison circuit. In the figure: 1... Main transmission 5... Brake which is a frictional engagement element for deceleration 7... Clutch which is a frictional engagement element for direct coupling 8... Clutch which is a frictional engagement element for four-wheel drive 10...4-wheel drive sub-shift ill 50.70
．． 80... Hydraulic servo 100... Main transmission hydraulic control device @104... Line pressure oil path 105... Manual valve 111... Governor pressure oil path 200... Sub-transmission hydraulic control device 201 ...First oilway 202...
-Second oil passage 203...Third oil passage 204...Fourth oil passage 210...First solenoid valve 220...Second
Solenoid valve 230...Switching valve 240...Inhibitor valve Fig. 1 Fig. 3 Fig. 6 Fig. 7

Claims (1)

[Scope of Claims] 1) A transmission, a four-wheel drive switching device capable of switching between two-wheel drive and four-wheel drive, and an electronic control device that inputs vehicle driving conditions; In a control device for a four-wheel drive transmission comprising a shift control device that controls a drive switching device, the shift control device controls the sliding of the drive wheels when one of the front wheels or the rear wheels is in a two-wheel drive state. 1. A control device for a four-wheel drive transmission, characterized in that the control device has a means for detecting the amount of slippage, and switches to a four-wheel drive state when the slippage exceeds a certain level. 2) The means for detecting the slippage of the driving wheels includes means for detecting the actual vehicle speed and the rotational speed of the driving wheels, and detects a difference of more than a certain value between the actual vehicle speed and the rotational speed of the driving wheels. 2. The control device for a four-wheel drive transmission according to claim 1, wherein when this occurs, it is determined that slippage has occurred in the drive wheels.