JPH0761777B2 - Power transmission device for part-time four-wheel drive vehicle - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a power transmission device for a part-time four-wheel drive vehicle that can be freely switched between two-wheel drive and four-wheel drive.

2. Description of the Related Art A power transmission device for a part-time four-wheel drive vehicle generally includes a clutch that switches between two-wheel drive and four-wheel drive, and when the clutch is disengaged, it is driven without the clutch. A two-wheel drive system that achieves a two-wheel drive system by two sets of two wheels and achieves a four-wheel drive system by the two wheels of the first set and the second set of two wheels that are driven via the clutch when the clutch is engaged. A four-wheel drive switching device is provided, and a four-wheel drive system or a two-wheel system is achieved by selectively turning on and off the supply of hydraulic pressure to the clutch. In such a part-time four-wheel drive vehicle, any one of the two wheels of the first set becomes idle during four-wheel drive,
When a state occurs in which most of the wheel drive torque based on the engine output is transmitted to the two wheels of the second set via the clutch, the engine is rotated at a high speed in a low speed stage,
If a large torque is temporarily transmitted through the clutch and the torque transmission capacity of the clutch is insufficient, the clutch may slip and wear of the clutch plate may significantly increase. However, it is necessary to design the clutch of the two-wheel / four-wheel drive switching device to have a large capacity so as to cope with such an untimely state, from the viewpoint of the balance between the frequency of requiring such large capacity and the vehicle manufacturing cost. Not preferable.

In order to control the hydraulic pressure supplied to the clutch of the two-wheel / four-wheel drive switching device of the part-time four-wheel drive vehicle on the basis of the difference in rotational speed between the front wheels and the rear wheels, the hydraulic pressure supplied to the clutch is adjusted. It is possible to provide a dedicated pressure regulating valve and perform control to reduce the amount of pressure reduction by the pressure regulating valve in accordance with an increase in the rotational speed difference between the front wheels and the rear wheels. JP-A-61-249837 and JP-A-61-1939
No. 31 publication.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention As described in the above-mentioned patent publication, the hydraulic pressure supplied to the clutch of the two-wheel / four-wheel drive switching device is set according to the difference in the rotational speed between the front wheels and the rear wheels. By controlling the pressure regulator valve, a clutch engagement degree that better suits the magnitude of the driving torque to be transmitted through the clutch is achieved, and when the part-time four-wheel drive vehicle is driven in the four-wheel drive state, the front wheels are The drive torque can be appropriately distributed to the front wheels and the rear wheels according to the fluctuation of the reaction force applied to the front and rear wheels from the road surface, and the flexibility of the power transmission system during four-wheel drive can be increased. However, providing a dedicated pressure regulating valve for adjusting the hydraulic pressure supplied to the clutch of the two-wheel / four-wheel drive switching device as described in the above-mentioned patent publication increases the number of parts of the power transmission device accordingly. , Power transmission device Result in increased costs.

Further, in the structure in which the hydraulic pressure supplied to the clutch of the two-wheel / four-wheel drive switching device is regulated by the dedicated pressure regulating valve as described in the above-mentioned patent publication, the hydraulic pressure which is the original hydraulic pressure supplied to the pressure regulating valve. Is, of course, considered to be the line hydraulic pressure for operating the hydraulic servo device in the main transmission etc. included in the power transmission device of the vehicle, so the value of the original hydraulic pressure is suitable for the control of the main transmission etc. Is the value of the line hydraulic pressure regulated by the primary regulator valve that regulates the hydraulic pressure from the oil pump. Therefore, as described above, the clutch pressure of the two-wheel / four-wheel drive switching device is changed according to the difference in the rotational speed between the front and rear wheels. The purpose of achieving a flexible four-wheel drive control that adjusts the engagement pressure and adapts to the reaction force applied to the front and rear wheels from the road surface can be fully achieved, but as mentioned above, the front wheel (or rear wheel) falls into a groove or the like. I slipped In this case, in order to temporarily increase the engaging pressure of the clutch of the two-wheel / four-wheel drive changeover device when the vehicle is to be escaped from that, the hydraulic pressure for the clutch is still supplied to the pressure regulating valve. The original hydraulic pressure itself is insufficient.

The present invention has been made in consideration of the above circumstances in the prior art.
To supply a higher hydraulic pressure when a specially increased hydraulic pressure is required for the clutch without providing a dedicated pressure regulating valve for regulating the hydraulic pressure for operating the clutch of the four-wheel drive switching device. It is an object of the present invention to provide a power transmission device for a part-time four-wheel drive vehicle that can be used.

Means for Solving the Problems According to the present invention, the above-mentioned problems include a two-wheel drive system including a main transmission and a first set of two wheels that are driven without a clutch when the clutch is disengaged. And a two-wheel / four-wheel drive switching device for achieving a four-wheel drive system by the two wheels of the first group and the two wheels of the second group driven via the clutch when the clutch is engaged. In a power transmission device of a part-time type four-wheel drive vehicle, the clutch is a source hydraulic pressure for operating each hydraulic servo device of the main transmission, and a line hydraulic pressure regulated by a primary regulator valve from a discharge pressure of an oil pump is used as a source hydraulic pressure. Directly actuated, the primary regulator valve has a boost port that selectively raises the line oil pressure regulated thereby, and a boost port is provided to the boost port. Means is provided for selectively supplying hydraulic pressure, the means being adapted to supply boost hydraulic pressure to the boost port in response to a control signal instructing an increase in engagement force of the clutch. And a power transmission device for a part-time four-wheel drive vehicle.

Actions and Effects of the Invention As described above, when the clutch of the two-wheel / four-wheel drive switching device is engaged, the line hydraulic pressure regulated by the primary regulator valve is directly supplied, and it is required to increase the engaging force of the clutch. The boost hydraulic pressure is supplied to the boost port provided in the primary regulator valve only when it is turned on, and the line hydraulic pressure itself is raised by this, so it is dedicated for the clutch of the two-wheel / four-wheel drive switching device. Instead of providing a pressure regulator valve, a relatively small modification of the primary regulator valve that adds one boost port to the primary regulator valve can be accommodated, which lowers the cost of the vehicle's power transmission device by that amount. In addition, the clutch of the two-wheel / four-wheel drive switching device can be temporarily engaged with a particularly large engagement. When the resultant force is required, the line hydraulic pressure itself can be temporarily increased to engage the clutch of the two-wheel / four-wheel drive switching device with a high hydraulic pressure exceeding the line hydraulic pressure used during normal operation of the vehicle. Even when a smaller clutch having a sufficient capacity is used during normal operation of the vehicle, it is possible to temporarily achieve a higher clutch transmission torque only in the event of an emergency in which the wheel falls into a groove or the like.

Example Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows one embodiment of a vehicle power transmission device equipped with a part-time type four-wheel drive system for implementing a clutch control method according to the present invention. In the figure, reference numeral 1 denotes an automatic transmission, which has a fluid torque converter 2 of a general structure and a gear type main transmission 3 which are connected in series when viewed in a power transmission path. The input shaft 4 to the internal combustion engine 10
It is drive-connected to 0 and can be given rotational power from the internal combustion engine 100.

The main transmission device 3 is a gear-type transmission device having a general structure of four forward gears and one reverse gear, and the gear positions are switched by a control hydraulic pressure given from a hydraulic control device 10.

The output shaft 5 of the automatic transmission 1 is drivingly connected to a four-wheel drive device 15. The four-wheel drive device 15 is a two-stage switching type auxiliary transmission device.
16 and a two-wheel / four-wheel drive switching device 20.

The sub-transmission device 16 is in the direct connection stage when the clutch 17 is engaged, while in the deceleration stage when the brake 18 is engaged, so that the clutch 17 and the brake 18 are engaged and released.
In response to an instruction from the L / H position selection switch 35, the control hydraulic pressure supplied from the hydraulic control device 10 controls the switching between the direct coupling stage and the deceleration stage.

The two-wheel / four-wheel drive switching device 20 has a rear-wheel drive output shaft 22 and a front-wheel drive output shaft 23, and the rear-wheel drive output shaft 22 is directly connected to the output shaft 19 of the auxiliary transmission device 16. The output shaft 19 is always connected to the output shaft 19, while the front wheel drive output shaft 23 is the drive gear.
24, a driven gear 25, and a transmission 27 composed of an endless chain 26 stretched between the two, and a two-wheel / four-wheel switching clutch 28 so as to be selectively connected to the output shaft 19. ing. The clutch 28 is of a hydraulically actuated type and is configured to be engaged by being supplied with hydraulic pressure to a servo device (not shown) and to increase the engagement pressure in accordance with the increase in the hydraulic pressure. . The supply of hydraulic pressure to the servo device of the clutch 28 is controlled by the hydraulic control device 10.

The hydraulic control device 10 is operation-controlled by an electric signal from an electric control device 30 including a microcomputer.
The information about the throttle opening of 0, the information about the rotation speed of the rear wheel output shaft 22 from the rear wheel shaft rotation speed sensor 32, the information about the rotation speed of the front wheel drive output shaft 23 from the front wheel shaft rotation speed sensor 33, The position sensor 34 provides information about the manual shift range, the L / H position selection switch 35 provides information about the gear selection state of the auxiliary transmission 15, and the four-wheel drive selection switch 36 shows whether four-wheel drive is selected. Information is given to each, and an electric signal as a control command is output to the hydraulic control device 10 according to the information.

As shown in FIG. 2, the hydraulic control device 10 includes a hydraulic oil storage section 40, an oil pump 41 which sucks hydraulic oil from the hydraulic oil storage section and pressurizes and discharges the hydraulic oil, and an oil pump 41. And a primary regulator valve (line hydraulic pressure control valve) 42 for adjusting the hydraulic pressure of the above to a predetermined line hydraulic pressure.

The primary regulator valve 42 includes two spools 43 that are provided in the valve bore so as to be vertically movable in the figure.
And 44 and an inlet port 46 connected in the middle of the oil passage 45a
An outlet port 47 connected to the drain, outlet ports 48 and 49 connected to a converter hydraulic control valve (secondary regulator valve) not shown in the figure, and an intermediate portion of the oil passage 45a via the throttle 50. Pilot port 51 and a throttle port 52 to which a throttle hydraulic pressure control valve (not shown) is supplied with a throttle hydraulic pressure that increases in accordance with an increase in the throttle opening, that is, the accelerator pedal depression amount.
And a reverse port 53 to which the line hydraulic pressure is supplied only during reverse, a bus port 54 to which the line hydraulic pressure is selectively supplied, and a compression coil spring 55 that biases the spool 43 upward in the drawing. . The spool 43 is driven on the basis of the equilibrium relationship between the downward force in the figure given by the hydraulic pressure introduced to the pilot port 51 and the upward force in the figure exerted by the compression coil spring 55 and the spool 44. When the downward force is larger than the upward force in the figure, the communication between the inlet port 46 and the outlet port 47 and the communication degree between the inlet port 46 and the outlet port 49 are increased respectively. When the force is larger than the downward force in the figure, the two communication degrees are reduced.

As described above, the spool 43 operates to supply the oil passage 45b with a hydraulic pressure generally called a line hydraulic pressure adjusted according to the equilibrium relationship of the forces acting on the spool 43. From 45b, each hydraulic servo device of the main transmission device 3, the auxiliary transmission device 16 of the four-wheel drive device 15, and the clutch 28
Is selectively supplied to each of the hydraulic servo devices. The line hydraulic pressure increases in accordance with the increase in the throttle hydraulic pressure applied to the throttle port 52, and when the line hydraulic pressure is being supplied to at least one of the reverse port 53 and the boost port 54, the line hydraulic pressure is being supplied to these ports. The oil pressure level for the same throttle oil pressure is increased as compared to when it is not.

The boost port 54 is connected to the middle of the oil passage 45b by the oil passage 56, and the line hydraulic pressure is supplied only when the drain port 59 is closed by the valve element 58 of the electromagnetic solenoid valve 57. Solenoid solenoid valve 57 valve element 58
When the electromagnetic solenoid 60 is not energized, the spring force of the compression coil spring 61 moves upward in the figure to open the drain port 59, while the electromagnetic solenoid 60 is energized. The electromagnetic force causes the downward movement in the figure to close the drain port 59.

Therefore, when the electromagnetic solenoid 60 is energized, the line hydraulic pressure is increased as compared to when the electromagnetic solenoid 60 is not energized.

Control of energization to the electromagnetic solenoid 60 is an electric control device
According to the flow chart shown in FIG. 3, the control method according to the present invention is carried out by 30.

The routine of the flowchart shown in FIG. 3 is repeatedly executed at predetermined time intervals, and in the first step 100, information is input from various sensors.

After step 100, the routine proceeds to step 101, where the gear stage of the main transmission 3 is determined in accordance with the vehicle speed (rear wheel rotation speed), the throttle opening and the manual shift range. The shift stage of the main transmission 3 is switched and set based on the shift stage. After step 101, the process proceeds to step 102.

In step 102, the shift stage of the auxiliary transmission 16 is switched and set based on the instruction from the L / H position selection switch 35.

In step 103, it is determined whether or not the four-wheel selection switch 36 is in the on state and the four-wheel drive is selected. When four-wheel drive is selected, the process proceeds to step 104, while when four-wheel drive is not selected, step 11 is performed.
Go to 1.

In step 104, the line hydraulic pressure is supplied to the hydraulic servo device of the clutch 28. As a result, the clutch 28 is engaged, and the rotational power appearing on the output shaft 5 of the automatic transmission 1 is distributed and supplied to each of the rear wheel drive output shaft 22 and the rear wheel drive output shaft 23. As a result, the four-wheel drive state is set.

After step 104, the routine proceeds to step 105, where it is judged whether or not the flag F is 1. When the flag F = 1, go to step 109,
When the flag F = 1 is not satisfied, the routine proceeds to step 106.

In step 106, the difference ΔN in rotational speed between the front wheel rotational speed Nf and the rear wheel rotational speed Nr is detected. Step 10
After step 6, the process proceeds to step 107.

At step 107, it is judged if the rotation speed difference ΔN is larger than a predetermined value ΔN _set , for example, 10 rpm. When ΔN ≧ ΔN _set , for example, the rear wheels are in the stuck-in state and the front wheels cannot slip, and the clutch 28 is slipping. At this time, the routine proceeds to step 108. On the other hand, when ΔN ≧ ΔN _set is not established, the routine proceeds to step 110.

In step 108, the electromagnetic solenoid 60 is energized. When the electromagnetic solenoid 60 is energized, the electromagnetic solenoid valve 57 is closed to supply the line hydraulic pressure to the boost port 54 of the primary regulator valve 42, which increases the line hydraulic pressure as compared with the normal time. The generated line hydraulic pressure is supplied to the hydraulic servo device of the clutch 28. This increases the engagement pressure of the clutch 28, increases the transmission torque capacity of the clutch 28, and prevents the clutch 28 from slipping. At this time, the fluid torque converter 2 is in a stalled state.
Further, in step 108, the flag F is set to 1.

Step 109 is a step that is executed when the electromagnetic solenoid 60 is already energized and the line hydraulic pressure is being increased to increase the transmission torque capacity of the clutch 28. In this step 109, the front wheel rotation speed is It is determined whether or not Nf is a predetermined value Nfset, which is, for example, a vehicle speed of 10 km / h or more. When Nf ≧ Nfset, it means that the vehicle is running, and at this time, the large driving force is not transmitted to the clutch 28, so the routine proceeds to step 10. On the other hand, when Nf ≧ Nfset, the transmission torque capacity of the clutch 28 is continuously increased. It is reset to keep it.

In step 110, the energization of the electromagnetic solenoid 60 is stopped, and the flag F is set to zero. When the energization of the electromagnetic solenoid 60 is stopped, the electromagnetic solenoid valve 57 is opened and the supply of the line hydraulic pressure to the boost port 54 of the primary regulator valve 42 is stopped, whereby the line supplied to the servo hydraulic device of the clutch 28 is stopped. The hydraulic pressure drops to the normal value,
In response to this, the engagement pressure of the clutch 28 is reduced, and the transmission torque capacity thereof is reduced to a sufficient value under normal conditions.

Step 111 is executed when four-wheel drive is not selected, and in this step 111, the line hydraulic pressure supplied to the hydraulic servo device of clutch 28 is discharged. This releases the clutch 28 and the internal combustion engine 10
The rotational power of 0 is transmitted only to the rear wheels via the automatic transmission 1.

By performing the control in accordance with the above-described flowchart, the rear wheels that are always driven are stuck in the state of idling and cannot carry the driving force, and only the front wheels that are selectively driven can carry the driving force. Is detected due to a difference of at least a predetermined value between the rear wheel rotational speed and the front wheel rotational speed, the engagement pressure of the four-wheel drive clutch is increased as compared with the normal time, and the transmission of the clutch is thereby increased. The torque capacity increases, and even if the driving force transmitted to the front wheels under the above-described conditions becomes higher than the maximum value during normal four-wheel drive, the clutch does not cause a shortage of the transmission torque capacity, At this time, the clutch is prevented from slipping,
The durability of the clutch will be improved.

The detection that the driving force transmitted to the selectively driven wheels is larger than the maximum value during normal four-wheel drive is detected when the rotational speed difference between the rear wheel rotational speed and the front wheel rotational speed is a predetermined value or more. In addition to the above, the torque sensor 37 detects the drive torque Tf transmitted to the selectively driven wheels, for example, the front wheels, and when the front wheel drive torque Tf is a predetermined value Tfset or more, the four wheels are driven. The electromagnetic solenoid 60 of the electromagnetic solenoid valve 57 may be energized so that the line hydraulic pressure higher than usual is supplied to the hydraulic servo device of the driving clutch 28. The flow chart of the control in this case is shown in FIG.

Steps 100 to 104 in the flow chart shown in FIG. 4 are substantially the same as those in the flow chart shown in FIG. 3, and whether or not four-wheel drive is selected in step 103 When it is determined that the four-wheel drive is selected, the process proceeds to step 104, and when the four-wheel drive is not selected, the process proceeds to step 208.

At step 205, it is judged if the front wheel drive torque Tf is equal to or larger than a predetermined value Tfset. T
When f ≧ Tfset, the routine proceeds to step 206, where T
When f ≧ Tfset is not satisfied, the process proceeds to step 207.

In step 206, the electromagnetic solenoid 60 is energized to increase the line hydraulic pressure supplied to the hydraulic servo device of the clutch 28 from the normal state.

In step 207, the energization of the electromagnetic solenoid 60 is stopped, and the line hydraulic pressure supplied to the hydraulic servo device of the clutch 28 is reduced to the normal hydraulic pressure.

In step 208, the line hydraulic pressure supplied to the hydraulic servo device for releasing the four-wheel drive clutch 28 is discharged.

Also in the embodiment shown in FIG. 4, when a driving torque larger than usual is transmitted to the selectively driven front wheels, the line hydraulic pressure supplied to the hydraulic servo device of the four-wheel drive clutch increases. As a result, the engagement pressure is increased, and thereby the transmission torque capacity is increased, and the same effect as in the case of the above-described embodiment is obtained.

The wheels that are constantly driven may be the front wheels, and the wheels that are selectively driven may be the rear wheels.

In the above, the present invention has been described in detail with respect to specific embodiments, but the present invention is not limited to these, and various embodiments are possible within the scope of the present invention. It will be apparent to those skilled in the art.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a vehicle power transmission device equipped with a part-time type four-wheel drive system for implementing the clutch control method according to the present invention, and FIG. 2 is a clutch control method according to the present invention. FIG. 3 is a schematic configuration diagram showing one embodiment of a hydraulic control device used for implementing the above, and FIG. 3 and FIG. 4 are flowcharts showing the outline of the clutch control method according to the present invention. 1 …… Automatic transmission, 2 …… Fluid torque converter, 3 ……
Main transmission, 4 …… input shaft, 5 …… output shaft, 10 …… hydraulic controller, 15 …… four-wheel drive, 16 …… sub-transmission, 17 …… clutch, 18 …… brake, 19… … Output shaft, 20 …… two-wheel / four-wheel drive switching device, 22 …… rear wheel drive output shaft, 23 …… front wheel drive output shaft, 24 …… drive gear, 25 …… driven gear, 2
6 …… Chain, 27 …… Transmission, 28 …… Clutch, 30 ……
Electric control device, 31 …… Throttle opening sensor, 32 …… Rear wheel shaft speed sensor, 33 …… Front wheel shaft speed sensor, 34 …… Shift position sensor, 35 …… L / H position selection switch, 36… … Four-wheel drive selection switch, 37 …… Torque sensor, 4
0 …… Operating oil reservoir, 41 …… Oil pump, 42 …… Primary regulator valve, 43,44 …… Spool, 45a, 45b ……
Oil passage, 46 …… Inlet port, 47 …… Drain port, 48,49…
… Exit port, 50 …… Throttle element, 51 …… Pilot port, 52 …… Throttle port, 53 …… Reverse port, 54
…… Boost port, 55 …… Compression coil spring, 56 …… Oil passage, 57 …… Electromagnetic solenoid valve, 58 …… Valve element, 59 …… Drain port, 60 …… Electromagnetic solenoid, 61 …… Compression coil spring, 100 ... Internal combustion engine

Claims (1)

[Claims] 1. A two-wheel drive system comprising a main transmission and a clutch, which is driven by a first set of two wheels when the clutch is disengaged, and is driven without the clutch. Two wheels that achieve a four-wheel drive system with two wheels of a set and two wheels of a second set driven through the clutch
A power transmission device for a part-time four-wheel drive vehicle including a four-wheel drive switching device, wherein the clutch serves as a source hydraulic pressure for operating each hydraulic servo device of the main transmission device, and a primary regulator valve is used based on a discharge pressure of an oil pump. Is directly operated by the line hydraulic pressure regulated by the primary regulator valve, and the primary regulator valve has a boost port for selectively increasing the line hydraulic pressure regulated thereby, and the boost hydraulic pressure is selectively supplied to the boost port. Means for supplying boost hydraulic pressure to the boost port in response to a control signal instructing an increase in the engagement force of the clutch. Power transmission device for driving vehicle.