JPH0514661B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION This invention relates to a method of controlling a four-wheel drive system including a clutch means, such as a wet type multi-disc clutch, which is involved in distributing torque between front and rear wheels.

Prior Art Among these types of four-wheel drive devices, for example, a full-time four-wheel drive device, the present applicant has applied for patent application No. 60-280662.
It has already been proposed as a No. Its basic configuration is that the output shaft of the automatic transmission is connected to the planetary carrier of the planetary gear mechanism that makes up the center differential device, and the ring gear, which is one output member, is connected to the rear wheel drive shaft. At the same time, the sun gear, which is the other output member, is connected to the front wheel output shaft via a transmission means consisting of a chain and a sprocket, and transmission is performed between any two of the planetary carrier, the sun gear, and the ring gear. It is equipped with a differential control clutch that can vary the torque capacity.

Therefore, with such a configuration, releasing the differential control clutch will cause the center differential device to perform full differential operation, and fully engaging the differential control clutch will cause the center differential to perform full differential operation. With the differential device no longer working, the rear wheel drive shaft and front wheel drive shaft are in a so-called direct connection state, and for each of these states, the differential control clutch is set to an intermediate engagement between fully engaged and fully disengaged. By adjusting the engagement force in this state, the torque distribution between the rear wheel drive shaft and the front wheel drive shaft can be appropriately set.
Therefore, in the device of the above-mentioned Japanese Patent Application No. 60-280662, by providing a control device that controls the transmission torque capacity by the differential control clutch in accordance with the input torque, as the throttle opening is increased by depressing the accelerator, The transmission torque capacity is increased (that is, the differential limit is strengthened), thereby improving running performance and handling stability in conditions that require high output.

As a method of controlling a four-wheel drive system equipped with a differential limiting device that limits the differential of the center differential device described above, there is no method other than the method of executing and canceling the differential limiting and adjusting the differential limiting capacity as needed. Therefore, a method of always performing differential limiting has been considered. In this method, in order to prohibit differential restriction when there is a large difference in tire diameter between the front and rear due to a tire blowout or chain installation, the center differential is normally set free once between starting and stopping. Learn the differential rate caused by tire diameter difference,
If the differential ratio is equal to or higher than a predetermined value, control is performed to prohibit subsequent differential limiting. In this case, if the differential ratio is less than or equal to the predetermined value, the differential restriction will not be lifted thereafter.

Problems to be Solved by the Invention However, according to the above-mentioned methods that constantly limit the differential, the differential limiting device is normally activated once to calculate the differential ratio between the front and rear wheels between starting and stopping. When the differential ratio is released and the obtained differential ratio is less than a predetermined constant value, the differential limiting capacity is changed according to the driving state while the differential limiting device remains in operation. Therefore, if differential differential is to be limited at all times, problems may arise due to steering, slippage, or uneven tire wear caused by small tire diameter differences that result in a differential ratio below the above-mentioned certain value. Due to the difference in rotational speed of the tires, the differential limiting device, which consists of a friction engagement means such as a wet clutch, remains in a low-speed slipping state, resulting in a decrease in durability due to a lack of surface lubricating oil. There was a risk that it would happen.

The present invention was made against the background of the above-mentioned circumstances, and an object of the present invention is to provide a control method that can improve the durability of clutch means that performs differential limiting and torque distribution control in a four-wheel drive system. It is.

Means for Solving the Problems In order to achieve the above object, the present invention provides a four-wheel drive system that constantly performs differential differential control, in which the clutch means is engaged at regular intervals within a range that does not impede the running of the vehicle. This method is characterized in that the clutch means involved in the distribution of torque between the front and rear wheels is kept in a non-operating state, and the clutch means is always kept in a predetermined state when the differential ratio between the front and rear wheels is below a predetermined value. When controlling a four-wheel drive device that limits differential differential by acting to have a torque capacity, it is possible to control a four-wheel drive system that operates to have a torque capacity so that the vehicle speed exceeds a predetermined constant speed when the vehicle travels for a predetermined period of time with the clutch device being applied. , and when the steering angle is below a predetermined angle and the throttle opening is below a predetermined opening, the clutch means is brought into a non-operating state, and after the non-working state continues for a predetermined period of time, the clutch is turned off. The method is characterized in that the means is brought into operation.

Further, the clutch means in this invention is a differential clutch of a center differential device that has one input member and two output members for front wheels and rear wheels, and performs differential operation between the front wheels and the rear wheels. It can be a frictional engagement means with variable transmission torque capacity to limit the operation.

Operation The method of the present invention is directed to a four-wheel drive device including a clutch means that is operated to limit the differential differential between the front and rear wheels when the differential ratio between the front and rear wheels is less than a predetermined value. When the driving time in which the means is in operation exceeds a certain time, the vehicle speed, steering angle, and throttle opening are judged. For example, the clutch means is switched to the inactive state for a predetermined period of time. Therefore, during the non-operating state, oil is supplied to the clutch means or heat generation is eliminated, so that its durability is improved. Furthermore, this non-operating state is set to supply oil to the clutch means and temporarily eliminate heat generation, and is set temporarily when the vehicle speed, steering angle, and throttle opening meet the above conditions. Since the setting is set to 1, there is no problem with the driving condition and stable driving can be maintained.

Examples The method of the present invention will be explained in detail below based on examples.

FIG. 1 is a flowchart showing an example of the method of the present invention, and the method shown here is carried out using, for example, the apparatus shown in FIGS. 2 and 3. That is, in FIG. 2, reference numeral 1 indicates an internal combustion engine, and the internal combustion engine 1 is installed vertically at the front of the vehicle. At the rear of the internal combustion engine 1, a vehicle automatic transmission 2 and a four-wheel drive transformer are installed. and a device 3 are connected in sequence.

The automatic transmission 2 for a vehicle has a hydraulic torque converter 5 of a general structure provided in a converter case 4 and a gear type transmission device 7 provided in a transmission case 6. The input member 8 of the converter 5 is connected to an output shaft (crankshaft, not shown) of the internal combustion engine 1, and the rotational power of the internal combustion engine 1 is applied to the transmission 7 via the hydraulic torque converter 5. There is. The transmission 7 is a transmission constructed using a planetary gear mechanism or the like, similar to those commonly used in the past, and is configured to be switched to a plurality of gears by a hydraulic control device 9.

Four-wheel drive transfer device 3 is full-time
It has a planetary gear type center differential device 10 for 4WD (continuous four-wheel drive), and the center differential device 10 is connected to the transmission device 7.
It has a carrier 11 as an input member to which rotational power is applied from, a planetary pinion 12 held by the carrier 11, a sun gear 13 and a ring gear 14 that mesh with the planetary pinion 12, and the ring gear 14 is connected to a rear wheel drive shaft 15. The sun gear 13 is connected to a sleeve-shaped front wheel drive intermediate shaft 16 coaxial with the rear wheel drive shaft 15 . The four-wheel drive transfer device 3 is provided with a front wheel drive shaft 17 parallel to the front wheel drive intermediate shaft 16, and the front wheel drive intermediate shaft 16 and the front wheel drive shaft 1
7 is the sprocket 1 attached to each of them.
8 and 19 are connected by an endless chain 20 that meshes with them.

The four-wheel drive transfer device 3 includes, as a differential control device, a hydraulically operated differential control clutch 2 that selectively connects a sun gear 13 and a ring gear 14.
The differential control clutch 21 is operated by a hydraulic control device 22 provided in the four-wheel drive transfer device 3.

As shown in FIG. 3, the differential control clutch 21 is a hydraulic servo-type wet multi-disc clutch, and the servo piston 37 is moved back by the servo hydraulic pressure supplied to the oil chamber 36 of the hydraulic servo device 35. 38
By moving to the right in the figure against the spring force, the sun gear 13 and ring gear 14 of the center differential device 10 are connected, and the oil chamber 36
The transmission torque capacity is proportionally increased in accordance with an increase in the servo oil pressure supplied to the servo oil pressure.

The hydraulic control device 22 includes a pressure regulator valve 40 that receives hydraulic pressure from an oil pump 39 incorporated in the vehicle automatic transmission 2 and adjusts the pressure to a predetermined hydraulic pressure. It has an electromagnetic servo hydraulic control valve 41 to which hydraulic pressure is applied from. The servo hydraulic control valve 41 has a port a connected to the oil chamber 36 of the hydraulic servo device 35, a hydraulic port b supplied with hydraulic pressure from the pressure regulator valve 40, and a drain port c. When energized, port a is communicated with hydraulic port b, while when de-energized, port a is communicated with drain port c. The servo hydraulic control valve 41 is given a pulse signal with a predetermined duty ratio from the control device 45,
As a result, the servo oil pressure control valve 41 supplies servo oil pressure of a magnitude corresponding to the duty ratio to the oil chamber 36 of the hydraulic servo device 35.

One end of a rear propeller shaft 24 is connected to the rear wheel drive shaft 15 via a universal joint 23 .

One end of a front propeller shaft 26 is connected to the front wheel drive shaft 17 via a universal joint 25 . The front propeller shaft 26 is arranged substantially parallel to the axis of the automatic transmission 2 for the vehicle, and is connected to the input shaft of the front differential device 30 by a universal joint 27 and an intermediate connecting shaft 28 at the other end. It is connected to one end of the drive pinion shaft 31. The drive pinion shaft 31 is rotatably supported by a differential case 32 integrally formed with a cast iron oil pan 29 of the internal combustion engine 1.

A drive pinion 33 made of a bevel gear is provided at the end of the drive pinion shaft 31, and the drive pinion 33 meshes with a ring gear 34 of the front differential device 30.

The hydraulic control devices 9 and 22 are electrical control devices 4
It operates based on a control signal from 5 to control the gear change of the transmission 7 and control the transmission torque of the differential control clutch 21. The control device 45 includes a microcomputer with a general structure and a counter that functions as a timer. Signals such as wheel rotation speed and brake signal are inputted. Here, the vehicle speed V is determined by any sensor that detects the rotation speed of the rear wheel drive shaft 15, the sensor that detects the rotation speed of the front wheel drive shaft 17, or the sensor that detects the rotation speed of the front wheel drive intermediate shaft 16. It may be an output signal from a sensor,
Furthermore, if the output signals of all these sensors are used, the reliability will be higher.

The control device 45 basically sends a control signal for controlling the gear change of the transmission device 7 according to a predetermined shift pattern according to the manual shift range, the vehicle speed V, and the throttle opening θ. A pulse signal with a predetermined duty ratio is outputted to the hydraulic control device 9 and to the servo hydraulic control valve 41 for controlling the transmission torque capacity of the differential control clutch 21 according to the gear position and throttle opening θ. Furthermore, during unsteady conditions such as turning or slipping, a pulse signal with a duty ratio corresponding to the unsteady condition is output to the servo hydraulic control valve 41, and when a predetermined condition is met, a pulse signal is output to the servo hydraulic control valve 41. The differential control clutch 21 is configured to cut off the current and discharge the servo hydraulic pressure to the differential control clutch 21.

Next, an example of the control method of the present invention for the above-described device will be explained. As shown in FIG. Flag is “1”
If (F=1), it is determined that the differential is being limited, and then it is determined whether or not the vehicle is in a steady running state. That is, it is determined whether the vehicle speed V is faster than a predetermined reference speed V0 (step 101), and if the determination result is "yes", it is determined whether the steering angle Θ is smaller than a predetermined reference angle Θ0. Judgment (step)
102), and if the determination result is "yes", it is determined whether the throttle opening θ is smaller than a predetermined reference opening θ0 (step 103). And if the judgment result of step 103 is "yes",
Vehicle speed V, steering angle Θ and throttle opening θ
When the conditions are met, it is determined that the running condition is steady, and then the duration of the differential restriction is determined.
It is determined whether Tm0 has passed a predetermined reference time T0 (step 104), and if the determination result is "yes", the transmission torque capacity Tc by the differential control clutch 21 is set to zero ( step
105). Specifically, this is accomplished by discharging the pressure from the oil chamber 36 of the servo device 35 by cutting off the power to the servo hydraulic control valve 41 and communicating its port a with the drain port c. Then, the flag is set to "0" and a timer is set to measure the release time of the differential control clutch 21.
Tm1 is reset to 0 (step 106) and the scanning process returns.

On the other hand, when the running condition is unsteady, that is, when the judgment result in any one of the above steps 101, 102, and 103 is "no", the transmission torque capacity Tc of the differential control clutch 21 is It is set appropriately according to the degree θ, the gear stage set in the transmission 7, and, if necessary, unsteady conditions such as the steering angle Θ and the rotational speed difference between the front and rear wheels due to slip (step 107). Specifically, this is done by the control device 45 calculating a duty ratio based on various input signals and applying a pulse signal corresponding to the obtained duty ratio to the servo hydraulic control valve 41.

Also, if the judgment result in step 104 is "no",
In other words, even if the differential limiting state in which the differential control clutch 21 is engaged does not continue until the reference time T0, the scanning process reaches step 107 and changes the transmission torque capacity Tc to the throttle opening θ and the gear position.
Alternatively, control may be performed based on the above-mentioned unsteady conditions as necessary.

On the other hand, if the differential control clutch 21 is released, that is, the decision result at step 100 is "no".
In this case, it is determined whether the time Tm1 during which the differential control clutch 21 has been released has reached a predetermined reference time T1 (step 108), and if the result of the determination is "yes", that is, the differential control clutch 21 is released. When the release duration of the dynamic control clutch 21 reaches T1, the transmission torque capacity Tc is changed as in step 107.
Settings are made based on the throttle opening θ and the gear position in the transmission 7, or, if necessary, on the above-mentioned unsteady conditions (step 109). In the following step 110, a flag is set to "1" and a timer is set to measure the engagement time of the differential control clutch 21.
Reset Tm0 to 0.

Furthermore, the judgment result of step 108 is “No”
In the case of , that is, when the continuous release time of the differential control clutch 21 has not reached the reference time T1,
The scanning process returns without any special control.

In other words, in the above control method, the running state reaches a steady state that satisfies the predetermined conditions at the time when a predetermined reference time T0 has elapsed after the differential control clutch 21 is engaged, or at the time when the reference time T0 has been exceeded. If so, the differential control clutch 21 operates for a certain period of time T1
is released, and lubricating oil is supplied. The relationship between engagement and release of the differential control clutch 21, steady/unsteady running conditions, and time is shown in FIG. 4. That is, when the engagement duration of the differential control clutch 21 reaches the reference time T0, the differential control clutch 21 is released if the vehicle is in a steady running state (in the case shown in FIG. 4).
Furthermore, if the driving state is unsteady when the engagement duration of the differential control clutch 21 reaches the reference time T0,
After that, the differential control clutch 21 is released when the steady running state is reached (in the case shown in FIG. 4), and even if there is an unsteady running state during the engagement period of the differential control clutch 21, the reference time If the vehicle is in steady running condition at the time T0 has elapsed, the differential control clutch 21 is released at that time (case 2 in FIG. 4). Therefore, even if a difference in rotational speed between the front and rear wheels occurs due to slip or uneven tire wear during driving with the differential control clutch 21 engaged, and a low-speed slipping condition occurs in the differential control clutch 21 due to this,
The temporary release provides lubricant to the differential control clutch 21 and prevents it from burning out. Furthermore, since the differential control clutch 21 is released in the above-mentioned steady running condition, it does not interfere with running.

The embodiment described above takes as an example a four-wheel drive device based on an FR vehicle (front engine rear wheel drive vehicle), but this invention is based on a FF vehicle (front engine front wheel drive vehicle). It can also be applied to a four-wheel drive device, and an example thereof will be explained with reference to FIG. In FIG. 5, an internal combustion engine 50 is placed horizontally at the front of a vehicle, and a vehicle automatic transmission 51 and a four-wheel drive transfer device 52 are connected to the internal combustion engine 50 in this order. The automatic transmission 51 for a vehicle includes a hydraulic torque converter 53 having a general structure and a transmission 18.

The hydraulic torque converter 53 includes an input member 53
It is connected to the output shaft 55 of the internal combustion engine 50 by the internal combustion engine 50 and receives rotational driving force from the internal combustion engine 50, and its output member 53b is connected to the transmission 54.

The transmission 54 may be of any conventional construction including a planetary gear arrangement and is adapted to change between a plurality of forward gears and at least one reverse gear.

Shift control of the transmission device 54 is performed by hydraulic pressure by a hydraulic control device 56.

The four-wheel drive transfer device 52 has a center differential device 57. The center differential device 57 includes a differential case 60 that is integrally equipped with an input gear 59 that meshes with an output gear 58 of the transmission 54, and a pinion shaft 61 provided in the differential case 60. A pair of differential pinions 62 that are each rotatably held and arranged opposite to each other, and a rear wheel output side gear 63 and a front wheel output side gear 64 that mesh with these differential pinions 62.
It has

The rear wheel output side gear 63 includes a rear wheel output gear 6.
5 is connected to the rear wheel output gear 65, and a rear wheel drive gear 67 of a rear wheel drive shaft 66 meshes with the rear wheel output gear 65.

A hollow front wheel drive shaft 68 is directly connected to the front wheel output side gear 64.

The four-wheel drive transfer device 52 includes a differential case 60, which is an input member of the center differential device 57, and a front wheel drive shaft 68, which is one output member of the center differential device 57. , a hydraulically operated differential control clutch 69 is provided as a differential control device connected to selectively transmit torque. The differential control clutch 69 is a servo-hydraulic wet multi-disc clutch, and its transmission torque capacity increases proportionally in response to an increase in servo oil pressure supplied to a servo-hydraulic device (not shown). ing.

The supply of servo hydraulic pressure to the hydraulic servo device is
This is performed by a hydraulic control device 70. The hydraulic control device 70 is configured to receive a pulse signal having a predetermined duty ratio from the control device 71, and supply servo hydraulic pressure having a magnitude corresponding to the duty ratio of the pulse signal.

The front wheel drive shaft 68 is connected to a differential case 73 of a front differential device 72. Front differential device 7
2 includes two differential pinions 75 that are rotatably held in the differential case 73 by a pinion shaft 74 and are arranged opposite to each other, a right side gear 76 that meshes with these differential pinions 75, and a left side gear 76 that is in mesh with these differential pinions 75. The right side gear 76 is connected to a right axle 78, and the left side gear 77 is connected to one end of a left axle 79.

The hydraulic control devices 56 and 70 operate based on control signals from an electric control device 71. The control device 71 receives signals such as vehicle speed V, steering angle Θ, throttle opening θ, manual shift position, front wheel rotation speed, rear wheel rotation speed, and brake signal, respectively, as in the above-described embodiment. ing.

The control device 71 basically sends a control signal for controlling the gear change of the transmission device 54 according to a predetermined shift pattern according to the manual shift range, the vehicle speed V, and the throttle opening θ. The output is sent to the hydraulic control device 56, and the differential control clutch 69 is output depending on the gear position and throttle opening θ.
outputs a pulse signal with a predetermined duty ratio to the servo hydraulic control valve to control the transmission torque capacity of When a predetermined condition is met, the servo hydraulic pressure control valve is deenergized and the servo hydraulic pressure to the differential control clutch 69 is discharged.

Each of the above embodiments is intended for a full-time four-wheel drive vehicle equipped with a center differential device, but the present invention is applicable to a two-wheel drive vehicle using an engagement means such as a wet multi-disc clutch. It can also be applied to part-time four-wheel drive vehicles that can be switched to four-wheel drive. Further, the clutch means in this invention is not limited to a friction clutch, but may be a viscous clutch using a viscous fluid such as silicone oil. In other words, a viscous clutch is arranged to limit the differential movement of a center differential device consisting of a differential gear mechanism, and an intermittent means for switching between operation and non-operation is provided, and by the intermittent means, the viscous clutch is If the input is cut off at regular intervals to make it inactive, the temperature rise due to continuous shearing force acting on the viscous fluid can be suppressed,
Its durability can be improved.

Effects of the invention As explained above, according to the method of this invention,
It is involved in the distribution of torque between the front and rear wheels, such as a differential limiting clutch of a center differential device or a clutch for switching between two-wheel drive and four-wheel drive, and when the differential ratio between the front and rear wheels is less than a predetermined value. Since the clutch means, which is normally in an active state, is switched to a non-active state at regular intervals during running, a wet clutch supplies lubricating oil, and a viscous clutch temporarily suppresses shearing action on viscous fluid. As a result, abnormalities such as burnout of the clutch means can be prevented and their durability can be improved.
In addition, the temporary switching of the clutch means to the inactive state is carried out during steady driving when conditions such as vehicle speed and steering angle meet preset conditions, so the durability of the clutch means can be improved without interfering with driving. You can improve your performance.

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing an example of the method of the present invention, FIG. 2 is a simplified diagram of a device targeted by the method, FIG. 3 is a simplified diagram of a control system for the differential control clutch, and FIG. FIG. 5 is a time chart showing the relationship between engagement and release of the differential control clutch, steady and unsteady running conditions, and time. FIG. 5 is a simplified diagram of another four-wheel drive device targeted by the method of the present invention. . 3,52...Four-wheel drive transfer, 10,5
7...Center differential device, 21,69
...Differential control clutch, 45, 71...Control device.

Claims (1)

[Claims] 1. A clutch means involved in distributing torque between the front and rear wheels is operated so as to always have a predetermined torque capacity when the differential ratio between the front and rear wheels is less than a predetermined value, thereby limiting the differential. In controlling the four-wheel drive system, the vehicle speed when traveling for more than a predetermined time with the clutch means in action is at least a predetermined constant vehicle speed, and the steering angle is less than a predetermined constant angle. Further, when the throttle opening is below a predetermined opening, the clutch means is brought into a non-operating state, and after the non-working state continues for a predetermined period of time, the clutch means is brought into an operating state. How to control the drive device. 2. The clutch means is used for differential operation of a center differential device which has one input member and two output members for front wheels and rear wheels, and performs differential operation between the front wheels and rear wheels. to limit the
2. The method of controlling a four-wheel drive device according to claim 1, wherein the method is a frictional engagement means having a variable transmission torque capacity.