JPH03279024A - Power transmission device for vehicle - Google Patents

Abstract

PURPOSE:To ensure an easy turn at the beginning of a turning operation, and improve the stability of a forward travel at the end of the turning operation by providing a means for detecting a steering condition, and a control means to reduce a differential limiting force for limiting a differential operation between wheels at the start of a steering operation, and to increase the aforesaid force at the end of the steering operation. CONSTITUTION:The engagement condition of a clutch 16 or the degree of limiting a differential operation is controlled by changing variously the value of a lock signal LCK for controlling the degree of opening of a hydraulic control valve 19. The signal LCK has a value of 1 or 0. It is assumed that a steering wheel 21 is at a neutral position and locked thereat in a travel. In this case, when the steering wheel 21 is operated in a direction off the neutral position, the signal LCK is turned to zero for weakening a differential limiting force for ensuring an easy steering operation. When it is detected that the steering wheel 21 is begun to be returned toward the neutral position, the signal LCK is turned to 1 for locking a center differential gear.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a power transmission device for a vehicle such as a four-wheel drive vehicle, and in particular, to a power transmission device for a vehicle such as a four-wheel drive vehicle. For example, it relates to improving straightness when turning and improving steering stability.

(Prior art) As a prior art related to a vehicle having such a differential limiting mechanism that limits the differential between wheels, for example,
There is No. 118936. Here, a locking mechanism is provided on the differential, and the wheels are normally driven in a differential state, and the differential is unlocked during turning operations to facilitate turning operations.

(Problems to be Solved by the Invention) According to this technology developed by Utsukushiki Sho, the differential is completely unlocked during the turning operation. It is true that this control has the effect of unlocking the differential at the beginning of a turn, making it easier to generate a differential between the wheels, and making the turning operation easier. However, if we consider the case where the turning operation is a lane change, we can see that at the end of the turning operation, the vehicle returns to driving in a straight line. stability should be pursued.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to propose a power transmission system for a vehicle that facilitates turning at the beginning of a turn and improves straight-line stability at the end of the turn.

(Means and operations for achieving the object) The configuration of the present invention for achieving the above object is provided in a power transmission device for a vehicle that controls the transmission of power to the wheels by limiting the differential between the wheels. , means for detecting the steering condition, and control for controlling the differential limiting force that limits the differential between the wheels at the start of steering to be small and to increase the differential limiting force at the end of steering. It is characterized by comprising means.

That is, since the control means reduces the differential limiting force that limits the differential between the wheels at the start of steering, turning becomes easier. Furthermore, since the differential limiting force is controlled to increase at the end of steering, straight-line stability is increased.

(Example) With reference to the attached drawings, two examples to which the present invention is applied will be described below.
Two (first and second embodiments) will be explained. The first embodiment is a four-wheel drive vehicle in which torque is transmitted to the front and rear four wheels via a center differential, and when the center differential is locked, a multi-plate clutch is used to secure the front and rear propeller shafts. This is an embodiment applied to a type of four-wheel drive vehicle.

On the other hand, in the second embodiment, the center differential is not installed,
In principle, the vehicle is rear-wheel drive, but if necessary, engine output is transmitted to the front wheels to provide four-wheel drive.

Figure 1 is a diagram schematically showing a driving force transmission system of a four-wheel drive vehicle according to a first embodiment. In the figure, 1 is an engine and a transmission, 3 is a center differential, 6 is a front wheel differential, and 7 is a rear wheel differential. The output of the engine 1 is transmitted to a center differential 3 via a drive shaft 2. A signal G indicating the current shift position is sent from the engine/transmission 1 to the controller 18. The front wheel driving force is transmitted to the front wheel differential 6 via the propeller shaft 4, and further,
The power is transmitted to the left and right front wheels 9.8 via a left front drive shaft 13 and a right front drive shaft 12, respectively.

21 is a steering wheel, the steering angle θ of which is detected by a sensor 22;

On the other hand, the engine torque for the rear wheels is transmitted to the rear wheel differential 7 via the center differential 3 and the rear wheel propeller shaft 5, and furthermore, the left rear wheel drive shaft 15 is transmitted to the left and right rear wheels 11.10, respectively.
．． The power is transmitted via the right rear wheel drive shaft 14.

The front wheel propeller shaft 4 and the rear wheel propeller shaft 5 are connected by a hydraulically driven multi-plate clutch 16. The oil pressure within the clutch 16 is adjusted by controlling the opening ratio of the oil pressure control valve 19. That is, the locked state of the front wheel propeller shaft 4 and the rear wheel blower shaft is controlled according to the value of the lock signal LCK that controls the aperture ratio.

In this embodiment, the engagement state of the clutch 16, that is, the degree of restriction of the differential operation, is controlled by varying the value of LCK. Signal LCK takes a value from O to 1. As the value approaches 1, the clutch becomes more firmly engaged and the differential approaches a more restricted state. Also, when LCK is small and close to 0, the engagement state of the clutch becomes looser and the differential approaches a free state (in this free state,
Torque distribution according to the loads on the front wheels and rear wheels is generated by the center differential 3 and transmitted to the front wheels and rear wheels, respectively.

In the figure, 20a, 20b, 20c, 20d
is a sensor that detects the rotational speed of the wheels, and these four wheel speeds (VFII, Vrt, Vllll, VI
IL) The CD average value is used as the vehicle speed in this embodiment.

FIG. 2 is a flowchart explaining the control procedure of the first embodiment. In step S2, the locked state of the center differential is checked. This can be determined by whether the controller 18 itself outputs the signal LCK, which governs the clutch engagement force, as "1" or as '0'.

Now, assume that the steering wheel 21 is in the neutral position and the vehicle is traveling in a locked state. In this case, the process advances to step S4 to check whether there is a change in the steering angle in the positive direction. Here, using FIG. 3, the direction of change in the steering angle θ, as referred to in this embodiment, will be defined.

In FIG. 3, when the steering wheel 21 rotates away from the neutral position, there is a change in the steering angle in the direction of r plus 1, and when the steering wheel 21 approaches the neutral position (rotating in the direction),
Assume that there is a change in the steering angle in the direction of r minus 1.

As long as no change in the positive direction is detected in step S4, that is, as long as the steering wheel 21 is not operated away from the neutral position, the control repeats the loop of steps S2 and S4.

When it is detected in step S4 that there is a change in the steering angle in the positive direction, that is, when the steering wheel 21 is operated in a direction away from the neutral position, it means that the steering wheel is turned to the left or right from the straight-ahead state. . In such a case, it means that the vehicle has intentionally deviated from straight driving to change lanes, for example, so in step S6, in order to weaken the differential limiting force to facilitate steering, LCK= Set to 0. In step S8, a change in the steering angle θ in the negative direction is waited for. That is, in order to return the steering wheel 21 to the neutral position, it is checked whether the steering wheel has started to be returned toward the neutral position. Until the steering wheel 21 begins to return toward the neutral position, the process returns from step S8 to step S6, and the center differential continues to be in the free state.

In the loop of step S6 → step S8, when it is detected that the steering wheel 21 has begun to return to the neutral position, in step SIO, the steering wheel 21 is turned down to lock the center differential.
Let CK=1. Then, the process returns to step S4 and waits for an operation such as a lane change to be started again.

(Thus, according to the first embodiment, the locked state is maintained until a turn is made, and when the turn is started, the center differential 3 is freed to improve steering performance. The free state is maintained until the steering wheel 21 is turned back. When the steering wheel 21 is turned back, the center differential 3 is changed to the locked state and straight-line stability is ensured.

FIG. 4 shows the change in the steering angle θ ((b) in FIG. 4) and the change in the signal LCK ((C in FIG. 4) when the steering angle θ of the steering wheel 21 changes as shown in (a). )) is shown in a timing chart.

! The first embodiment of the jJJL row pursues straight-line stability when returning the steering wheel by controlling the limit of the differential of the center differential. In this second embodiment, switching between two-wheel drive and four-wheel drive is performed in response to steering wheel operation. Considering that four-wheel drive has excellent straight-line stability, it is the first
As in the embodiment, when the steering operation being performed is an operation to return to the neutral position, the two-wheel drive is switched to the four-wheel drive.

FIG. 5 schematically shows the entire second embodiment, and in this figure, the same parts as in the embodiment of FIG. 1 are given the same numbers.

30 is a fluid clutch similar to the clutch in FIG. The rear propeller shaft 5 is constantly driven by power from the engine/transmission 1. In this state, the vehicle is in two-wheel drive. Then, when the signal LCK becomes 1'' and is input to the control valve 19, the engagement force of the clutch 30 becomes maximum, and the torque of the propeller shaft 5 is transmitted to the propeller shaft 4.In this state, the four-wheel drive It is.

FIG. 6 is a flowchart illustrating the control procedure of the second embodiment. In step S20, it is determined whether the vehicle is in a two-wheel running state or a four-wheel running state. This is controller 18
This can be determined by whether the signal LCK, which governs the clutch engagement force, is output as 1 or 0.

Now assume that the vehicle is in a locked state, that is, the vehicle is traveling in four-wheel drive. In this case, the process advances to step S22 to check whether there is a change in the steering angle in the positive direction. The definition of the direction of change in the steering angle θ in the second embodiment is the same as in the first embodiment.

While no change in the positive direction is detected in step S22, that is, while the steering wheel 21 is not operated so as to deviate from the neutral position, the control is performed in step S20 and step S22.
Repeat the loop.

When it is detected in step S22 that there has been a positive steering angle change, that is, when the steering wheel 21 is operated in a direction away from the neutral position, it means that the steering wheel is turned to the left or right from a straight-ahead state. do. In such a case, it means that the vehicle has intentionally deviated from straight driving to change lanes, for example, so in step S24, LCK=0 is set in order to switch to two-wheel drive to facilitate steering.
Make it. In step S26, a change in the steering angle θ in the negative direction is waited for. That is, in order to return the steering wheel 21 to the neutral position, it is checked whether the steering wheel has started to be returned toward the neutral position. The process returns from step S8 to step S6, and the two-wheel drive state continues until the steering wheel 21 begins to be returned toward the neutral position.

When it is detected in the loop from step S24 to step S26 that the steering wheel 21 has begun to be returned to the neutral position, LCK is set to 1 in step S10 in order to set the vehicle to four-wheel drive and ensure straight-line performance. And step S
The process returns to step 22 and waits for operations such as changing lanes to be started again.

Thus, according to the second embodiment, the four-wheel drive state is maintained until a turn is made, and once the turn is started, the vehicle shifts to two-wheel drive to improve steering performance.

Two-wheel drive is then maintained until the steering wheel 21 is turned back. When the steering wheel 21 is turned back, the state is changed to four-wheel drive, and straight-line driving is emphasized.

The present invention can be modified in various ways without departing from the spirit thereof.

In the above two embodiments, when the steering starts to return after turning, the LCK is set to "1" and the clutch is set to 16.30.
The fastening force was maximized. However, the present invention is not limited to this embodiment. Since the control valve 19 can linearly control the opening ratio, when the steering wheel starts returning after turning, LCK may be set to an intermediate value such as 0.8, for example.

In the above two embodiments, an embodiment with a center differential (first embodiment) and an embodiment in which the vehicle is normally rear-wheel drive but changes to four-wheel drive as needed (second embodiment) have been described. but,
The present invention is not limited to this, but can also be applied to a vehicle as shown in FIG. 7, for example. In this modified vehicle, the engine/transmission output is directly transmitted to the front propeller shaft 4. However, the rear propeller shaft 5 is connected to the output of the transmission 1 via a clutch 40. Therefore, the vehicle is normally front-wheel drive, and when the steering wheel starts returning after turning, the valve 19 is activated and the clutch 40 is engaged, resulting in four-wheel drive.

(Effects of the Invention) As explained above, the present invention provides a means for detecting a steering state and a means for detecting a steering state in a power transmission device for a vehicle that controls the transmission of power to the wheels by limiting the differential between the wheels. When starting the rudder, reduce the differential limiting force that limits the differential between the wheels (
The present invention is characterized in that it includes a control means for controlling the differential limiting force to increase at the end of steering.

That is, the control means reduces the differential limiting force that limits the differential between the wheels at the start of steering, making turning easier. Since it is controlled so that it becomes larger, straight-line stability increases.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of the first embodiment of the present invention, FIG. 2 is a flowchart showing the control procedure of the first embodiment, FIG. 3 is a diagram explaining the definition of the steering change direction, and FIG. 5 is a block diagram showing the configuration of the second embodiment according to the present invention. FIG. 6 is a flowchart showing the control procedure of the second embodiment.
A timing chart for explaining the operation, and FIG. 7 are diagrams for explaining the present invention in detail. In the diagram, 1...engine/transmission, 2...output shaft, 3...
Center differential, 4... Front wheel propeller shaft, 5...
Rear wheel propeller shaft, 6... Front wheel differential, 7... Rear wheel differential, 8.9.10.11... Wheels, 12.13,
14゜15...Wheel drive shaft, 16...Multi-plate clutch, 17...Oil pipe, 18...Controller, 1
9...Pressure control valve, 20 a, 20
b, 20 c, 20 d...wheel speed sensor, 2
1... Steering, 22... Rudder angle sensor.

Claims (1)

[Claims] (1) In a vehicle power transmission system that controls the transmission of power to the wheels by limiting the differential between the wheels, there is a means for detecting the steering state and a means for detecting the differential between the wheels at the start of steering. 1. A power transmission device for a vehicle, comprising: control means for controlling a differential limiting force that limits the differential limiting force to be small and increasing the differential limiting force at the end of steering.