JPH07217677A - Vehicular transmission torque control device - Google Patents

Abstract

PURPOSE:To provide a vehicular transmission torque control device capable of transmitting torque to each wheel so as to obtain an optimum torque distribution ratio in accordance with a running state. CONSTITUTION:A control unit 24 selects one control characteristic line, instructed by a selection signal Ss, from three prestored control characteristic lines using a rotating speed difference signal SDELTAn, computes a control current from the selected control characteristic line using the rotating speed difference signal SDELTAn, and feeds the computed current (i) to a hydraulic control valve 23. In this example, the control current (i) and control oil pressure P by the control valve 23 are in the proportional relationship, and the control oil pressure P and transmission torque quantity TOUT by a clutch 15 are also in the proportional relationship. The characteristic is thereby changed according to a specified running condition by the above-mentioned control.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle transmission torque control device for controlling a torque distribution ratio transmitted from a power plant to front and rear wheels via a torque transmission path.

[0002]

2. Description of the Related Art In a transmission torque control device of this type, a wet clutch, a viscous coupling, etc., whose transmission torque amount changes in accordance with a difference between a torque input speed and an output speed in the middle of a torque transmission path. There is one in which the torque transmitting means of is inserted. The torque transmission means has a structure in which a plurality of friction plates connected to the rotation shaft on the torque input side and a plurality of friction plates connected to the rotation shaft on the torque output side are alternately arranged. Here, in the wet clutch, the friction member between the input and output sides is fastened by a fluid pressure such as hydraulic pressure, and a fixed torque is transmitted according to the fastening force.
Therefore, by controlling the fastening force, that is, the fluid pressure, it is possible to control the amount of torque transmitted through the wet clutch. On the other hand, in the Viscos coupling, as an example thereof is disclosed in the specification of U.S. Pat. No. 3,760,922, an annular plate, which is a friction plate, is arranged in a viscous fluid to form a viscous fluid. The torque is transmitted by the shearing force of 1., and a predetermined torque transmission characteristic can be obtained by changing the area of the opening formed in the plate.

[0003]

In selecting the torque transmission characteristics of such torque transmission means, it is necessary to select the optimum one according to the traveling state. For example, in the case where the torque transmission means is interposed between the front and rear wheels, it is necessary to determine the torque ratio distributed between the front and rear wheels according to the running state. As an example, when driving on snowy roads where road surface resistance is low, the rear wheels tend to slip more easily.If the same torque distribution is used as when driving on normal dry roads, the torque is transmitted to the rear wheels. The generated torque is not effectively used as the driving force of the vehicle, which is not preferable. Further, it is known that the torque distribution ratio affects the steering characteristics of the vehicle. For example, when the drive distribution amount of the front wheels is larger than the drive distribution amount of the rear wheels, the reaction force against the lateral force at the time of turning is larger in the rear wheels than in the front wheels, so the front wheels are larger than the rear wheels. Excessive slip causes steering characteristics to become understeer, improving stability. However, on the other hand, the turning ability is impaired. Therefore, it can be suitable for high speed running where stability is required and for snowy roads where the friction coefficient of the road surface is small, but at low and medium speeds and mountain roads, the turning performance is low, making it difficult to ride. .

On the other hand, when the drive distribution amount of the front wheels is smaller than the drive distribution amount of the rear wheels, oversteer occurs, and conversely, in the state where the turning ability is required, suitable maneuverability can be obtained. Yes, but in driving conditions where safety is required,
It becomes a difficult car to drive. The present invention has been made in view of the above points, and it is an object of the present invention to provide a transmission torque control device for a vehicle that can transmit torque to each wheel so that an optimum torque distribution ratio is obtained according to a running state. To aim.

[0005]

In order to achieve the above object, in the transmission torque control device for a vehicle according to the present invention, the torque distribution ratio between the front and rear wheels is provided in the torque transmission path from the power plant to the wheels. Torque transmitting means for transmitting the torque from the power plant to the wheels so as to be changeable and controllable, characteristic setting means for setting the front and rear wheel torque distribution ratio control characteristics corresponding to the rotational speed difference between the front and rear wheels, and the front and rear wheels. Rotational speed difference calculating means for calculating the rotational speed difference, traveling state detecting means for detecting the traveling state of the vehicle, and a signal representing the rotational speed difference from the rotational speed difference calculating means is input and transmitted to the wheels. A control means for controlling the torque transmission means to control the torque, the control means is configured to determine the characteristic setting means from the rotation speed difference between the front wheels and the rear wheels obtained from the rotation speed difference calculation means. The torque distribution ratio determining means for determining the torque distribution ratio of the front and rear wheels based on the set torque distribution ratio control characteristic, and the front and rear wheels determined by the torque distribution ratio determining means by inputting the signal from the running state detecting means. And a torque distribution ratio changing means for changing the torque distribution ratio with respect to the rotational speed difference in accordance with the detected traveling state of the vehicle.

Due to the above-mentioned structure, it is possible to perform suitable torque distribution corresponding to the difference in the rotational speeds of the front and rear wheels. Therefore, the relationship between the slip states of the front and rear wheels can be favorably maintained, so that suitable running performance and steering characteristics can be provided. Further, since the torque distribution ratio of the front and rear wheels is changed based on the difference in rotational speed between the front and rear wheels according to the running state, the slip state of the front and rear wheels can be maintained at a suitable value according to the running state, which further improves the running performance. Can provide steering characteristics.

[0007]

Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 to 4 show an embodiment of the present invention in which a fluid torque transmitting means is inserted between the front and rear wheels of a four-wheel drive vehicle. In FIG. 1, reference numeral 10 indicates a power plant, and the power plant 10 includes an engine, a transmission and the like. A front side propeller shaft 14 is connected to an output shaft 12 of the power plant 10 via a gear train 13, and a rear side propeller shaft 16 is connected via a hydraulic variable clutch 15 which is a fluid type torque transmitting means. It is connected. The front side propeller shaft 14 is connected to the left and right front wheels 8 via a final gear unit 17. The rear propeller shaft 16 is connected to the left and right rear wheels 20 via a final gear unit 19. In this way, from the power plant 10 to the output shaft 1
2, a torque transmission path is formed to reach the front wheels 18 via the gear train 13, the propeller shaft 14 and the final gear unit 17, and torque transmission to the rear wheels via the output shaft 12, the clutch 15 and the final gear unit 19. A path is formed. Then, the torque distribution ratio of the front and rear wheels is adjusted by changing the pressure of the hydraulic oil applied to the clutch 15 and changing the amount of transmission torque of the clutch 15.

Next, referring to FIG. 2, the clutch 15 will be described.
The hydraulic control system will be described. As shown in the figure, the hydraulic oil in the oil tank 21 is sucked up by the pump 22, discharged at a predetermined pressure, and passed through the hydraulic control valve 23.
It is supplied to the hydraulic oil chamber 15a of the clutch 15. The hydraulic control valve 23 is controlled by the control unit 24, whereby the pressure of the hydraulic oil to the hydraulic oil chamber 15a of the clutch 15 is adjusted. That is, the fastening force between the friction plate 15b connected to the front side propeller shaft 14 of the clutch 5 and the friction plate 15c connected to the rear side propeller shaft 16 is controlled. A vehicle speed sensor 25, a steering angle sensor 26, a speed difference sensor 27, a selection switch 28 and the like are connected to the input side of the control unit 24. The vehicle speed sensor 25 detects the vehicle speed and outputs a vehicle speed signal S _v corresponding to the vehicle speed. The steering angle sensor 26 detects a steering angle and outputs a steering angle signal Sα corresponding to the detected value. Speed difference sensor 27, the rotational speed difference between the torque input side and the output side, i.e. to detect the rotational speed difference delta _n between the front end and rear propeller shafts 14 and 16, and outputs a speed difference signal SΔ _n. The selection switch 28 is for selecting the transmission torque characteristic of the hydraulic clutch 15. In this example, as shown in FIG. 3, the road surface condition (dry,
Wet and snow) 3 control lines f determined according to
_{It has A} , f _B , and f _C , and one of them can be manually selected via the switch 28. Therefore, the switch 28 outputs the selection signal S _s indicating the selected control line. The vehicle speed sensor 2
As 5, a rotation speed sensor that detects the rotation speed of the front side propeller shaft 14 can be used. Further, the rotation speed difference Δ _{n is} calculated by connecting the rotation speed sensor for detecting the rotation speed of the rear side propeller shaft 16 to the control unit 24 without using the speed difference sensor 25, and controlling based on this sensor output value. You may make it calculate in a unit.

In this example, in view of the fact that the rotational speed difference between the front and rear wheels fluctuates as the output torque of the power plant fluctuates, the fastening force is changed on the basis of this rotational speed difference, whereby the transmission torque amount T By adjusting _OUT , torque is distributed between the front and rear wheels at a predetermined distribution ratio. Further, the torque distribution ratio is determined according to the road surface condition (dry, wet, snow). In order to distribute the torque according to these defined distribution ratios, the curve f _A ,
The transmission torque amount T _OUT is controlled according to different transmission torque control characteristics represented by f _B and f _C. That is, the control unit 24 uses the rotational speed difference signal Esuderuta _n, selects one control characteristic line indicated by three control characteristic lines stored in advance by the selection signal S _S, the rotational speed difference signal Esuderuta
_{From the} selected control characteristic line, control current i
Is calculated, and the calculated current i is supplied to the hydraulic control valve 23. In this example, the control current i and the control oil pressure P by the control valve 23 are in a proportional relationship, and the control oil pressure P and the clutch 1
The transmission torque amount T _OUT due to 5 is also in a proportional relationship. Therefore, by such control, the curve f _{A of} FIG.
Transmission torque characteristics indicated by f _B and f _C can be obtained. Next, the change control operation of the transmission torque characteristic will be described with reference to the flowchart shown in FIG. First, in step ST1, read input signal SΔ _{n, S} S. Step ST2
In step S1, it is determined whether the control characteristic I _S indicated by the selection signal S _S is dry (I _S = 3), wet (I _S = 2) or snow (I _S = 1).
In the case of dry, the process proceeds to step ST5 and the curve f _{C of} FIG.
Transmission torque control is performed according to the characteristic represented by (Δ _n ). Similarly, in the case of wet and snow, the process proceeds to steps ST4 and ST3, respectively, and the transfer torque control is performed according to the characteristics indicated by the curves f _B (Δ _n ) and f _A (Δ _n ).

Here, as shown by these curves f _A , f _B and f _C , wet (f _B ) is more wet than snow (f _A ) and dry (f _B ) than wet (f _B ). f _C ) has a larger transmission torque amount T _OUT for the same rotation speed difference Δ _n . Therefore, if the driver selects the characteristic line f _A via the selection switch 28 when traveling on a snowy road (snow condition) with low road surface resistance,
The torque transmission to the rear wheel side where slippage is likely to occur is suppressed, and the generated torque can be effectively utilized as the forward force.
Further, when traveling on a dry road surface (dry state) where road surface resistance is high, if the characteristic line f _C is selected, the amount of torque transmitted to the rear wheel side can be increased, and therefore a torque shortage state occurs on the rear wheel side. Can be avoided. Further, when traveling on a road surface (wet state) wet with rainwater or the like, a characteristic line f _B having a torque transmission characteristic intermediate between those characteristic lines f _A and f _C described above.
Should be selected. Next, in step ST6,
It determines whether or not the rotational speed difference delta _n is greater than the value delta _n2 a predetermined. Further, in step ST7, it determines smaller or not than the value rotational speed difference delta _n is a predetermined Δ _n1 (<Δ _n2). If a negative decision in both steps, since the rotational speed difference delta _n is within the proper range (between delta _n1 and delta _n2), the transmission torque control by the characteristic line T _r that is currently selected is the proper Is. Therefore, this characteristic line T
Control by _r is continued.

However, when the rotational speed difference Δ _n is larger than the value Δ _n2 , the flow proceeds from step ST6 along the flow of "YES", and the selected characteristic line _Tr is transferred to the rear wheel side. Change to the characteristic line on the side of increasing. More specifically, the case and if the value delta _n is greater rotational speed of the rear wheels extremely small with respect to the front wheel, such a state, even though the road surface resistance is large, the amount of torque transfer commensurate therewith Occurs when the rear wheel is not engaged. Therefore, in order to eliminate such insufficient torque of the rear wheels,
More torque needs to be transmitted to the rear wheels. Steps ST8 to ST12 are steps for changing the characteristic line _Tr . First, in step ST8, it is determined which of the current control characteristics I _S is. In this example,
Since the control is performed based on the three characteristic lines, when dry (I _S = 3) is selected, there is no transmission torque to the rear wheel that is higher than this characteristic line. , Step ST8 follows the flow of "YES", and the dry state (I _S = 3) is maintained as it is. If not, steps ST9 and ST10 are executed, and the rotation speed difference Δ _n is _equal to or larger than the value Δ over the predetermined time t1.
It is determined whether the state is larger than _n2 . This time t
When it becomes 1 or more, the process proceeds from step ST9 to step ST11, and the control characteristic I _S is changed to the control characteristic on the side where the amount of transmission torque is large for the same rotational speed difference. Thereafter, the characteristic line T corresponding to the changed control characteristic I _S
Torque transmission control is performed according to _r .

On the other hand, when the rotational speed difference Δ _n is smaller than the value Δ _n1 , the process proceeds from step ST7 along the flow of "YES", and the selected characteristic line T _r is transferred to the rear wheel side. Change to the characteristic line on the side of decreasing. In this case, the road surface resistance is small, and as a result, a large amount of slippage occurs on the rear wheel side. In such a state, even if a large torque is transmitted to the rear wheels, the driving force cannot be effectively obtained. Therefore, in order to avoid such unnecessary torque transmission, it is necessary to reduce the amount of torque transmission to the rear wheels. In steps ST13 to ST17, this characteristic line _Tr
Is a step of change control. First, step ST13
At, it is determined which control characteristic I _S is present. In this example, the control is performed based on the three characteristic lines. Therefore, when Snow (I _S = 1) is selected, the torque transmitted to the rear wheels is smaller than this characteristic line. There is nothing, so from step ST13, "YE
Follow the flow of "S" and continue to snow (I _S = 1)
Hold the state of. Otherwise, step ST
14, ST15 is executed to determine whether or not the rotational speed difference Δ _n is smaller than the value Δ _n1 for a predetermined time t1 or more. When the time t1 or more is reached, the process proceeds from step ST14 to step ST16 and the control characteristic I
_S is changed to the control characteristic on the side where the amount of transmitted torque is small for the same rotational speed difference. After that, the torque transmission control is performed according to the characteristic line T _r corresponding to the changed control characteristic I _S.

As described above, according to this example, proper torque distribution can be always performed according to the road surface condition. In addition, in the above-described embodiment, a case has been described in which there are three control characteristic lines and a hydraulic clutch is interposed between the front and rear wheels, but the present invention is not limited to this. It is only necessary to have a plurality of control characteristic lines, and a torque transmitting means such as a hydraulic clutch may be arranged between the left and right wheels. Also,
Although the case of changing the control characteristic according to the road surface state has been described, it may have a plurality of control lines according to other parameters indicating the running state and may be changed according to the parameter. Further, in the above example, each control characteristic is manually selected by the selection switch, but it is also possible to use a selection means configured to automatically select a determined control characteristic at the start of traveling. Of course.

[0014]

As is apparent from the above description, in the present invention, since the torque distribution ratio of the front and rear wheels is controlled based on the difference in the rotational speed of the front and rear wheels, the relationship between the slip states of the front and rear wheels is preferable. Therefore, it is possible to provide suitable running performance and steering characteristics. Furthermore, since the torque distribution ratio of the front and rear wheels based on the difference in the rotational speed of the front and rear wheels is changed according to the running characteristics, the slip state of the front and rear wheels can be maintained at a suitable value according to the running state, which further improves the running performance. In addition, it has a practically excellent effect that the steering characteristics can be obtained.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing an example in which the present invention is applied to a four-wheel drive vehicle,

2 is a configuration diagram mainly showing a hydraulic control system in the example of FIG.

FIG. 3 is a characteristic diagram showing a transmission torque amount with respect to a rotational speed difference,

4 is a flowchart showing an example of a control operation in the example of FIG.

[Explanation of Codes] 10 Power Plant, 12 Output Shaft 14 Propeller Shaft 15 Clutch 17 Final Gear 23 Hydraulic Control Valve 24 Control Unit

Claims (1)

[Claims] 1. A torque transmission means for transmitting torque from a power plant to a wheel so as to change and control a torque distribution ratio of front and rear wheels, the torque transmission means being provided in a torque transmission path from the power plant to the wheels, and the front and rear wheels. Characteristic setting means for setting the front and rear wheel torque distribution ratio control characteristics corresponding to the rotational speed difference, rotational speed difference calculating means for calculating the rotational speed difference between the front wheels and the rear wheels, and traveling state detecting means for detecting the traveling state of the vehicle. And a control means for controlling the torque transmission means to control a transmission torque to the wheel by inputting a signal representing the rotation speed difference from the rotation speed difference calculation means, the control means comprising: A torque distribution for determining the torque distribution ratio of the front and rear wheels based on the torque distribution ratio control characteristics set by the characteristic setting means from the rotational speed difference between the front wheels and the rear wheels obtained from the speed difference calculation means. A signal from the ratio determining means and the traveling state detecting means is input, and the torque distribution ratio with respect to the rotational speed difference between the front and rear wheels determined by the torque distribution ratio determining means is changed according to the detected traveling state of the vehicle. A transmission torque control device for a vehicle, comprising: a torque distribution ratio changing means.