JP2628882B2 - Transmission torque control device for four-wheel drive vehicle - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention electronically controls the magnitude of a transmission torque transmitted from a power plant via a predetermined torque transmission path between front and rear wheels of a vehicle. The present invention relates to a transmission torque control device for a four-wheel drive vehicle.

(Prior Art) Some of the transmission torque control devices for a four-wheel drive vehicle as described above include, in the middle of the torque transmission path, each of them according to the rotation speed difference between the torque input side rotation speed and the torque output side rotation speed. There is a type in which a so-called fluid torque transmitting means such as a wet clutch or a viscous coupling in which the amount of torque transmitted to wheels changes is provided. Such a fluid torque transmitting means generally 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. (See FIG. 3). In the case of wet clutches, they are fastened by the pressure of the fluid, whereby a predetermined amount of torque is transmitted via the friction plate on the input side and the friction plate on the output side. On the other hand, in the case of a viscous coupling, for example, US Pat. No. 3,760,922 or JP-A-60-1
As disclosed in the specification and drawings of 72764, a hole of a predetermined size or a slit is formed in an annular plate as a friction plate, and a predetermined amount of air is introduced into a viscous fluid. A viscous clutch is formed, or the auxiliary output shaft of the transaxle is connected to two pairs of front and rear wheels (a pair of left and right front wheels and a pair of right and left rear wheels) via the viscous clutch. When the rotational speed difference between the sides is equal to or more than a predetermined value, a constant torque transmission (fastening) is performed as necessary so that a four-wheel drive state can be realized.

By the way, when the above-mentioned fluid transmission means is interposed between the front and rear wheels of the vehicle, if the output torque of the power plant itself fluctuates, the front and rear wheels are accordingly changed.
The rotational speed difference between the rear wheels also fluctuates. Therefore, if the fastening force (hydraulic value) between the friction plates of the torque transmitting means is arbitrarily changed based on the rotational speed difference, the transmitted torque itself can always be arbitrarily adjusted. You can do it. However, in the control of the amount of transmission torque based on such a change in the fastening force, the relative speed difference between the friction plates is small in a region where the rotation speed difference is small, so that friction contact between the friction plates in a stable dynamic friction state is obtained. As a result, the fastening force is not proportional to the transmission torque amount, and therefore, the control of the torque transmission amount may become unstable. The region where the rotation speed difference is small means an operation region where the rotation speed difference between the front and rear wheels is smaller than a predetermined reference value. Therefore, for example, the torque transmission characteristic is now the fourth.
Considering the case where control is performed as shown by a curve T = f (Δn) in the figure, a slight rotation difference occurs even when the vehicle does not need to transmit torque, for example, when traveling straight, and the rotation speed difference Δn becomes smaller than the rotation speed difference Δn. In a region smaller than Δno corresponding to the reference value, it is preferable to originally set the fastening force of the clutch friction plate to zero to inhibit torque transmission to the rear wheels in order to reduce the frequency of use of the device itself and improve reliability. . In this region, a so-called stick-slip phenomenon occurs because the frictional plates are not in a stable frictional contact state as described above, that is, the static frictional state and the dynamic frictional state are alternately repeated alternately between the frictional plates, As a result, a smooth torque transmission state cannot be realized. For this reason, in the low rotation speed difference region as described above, a relatively wide dead band region is fixedly set in consideration of the stick-slip phenomenon based on the predetermined rotation speed difference Δno, and the set dead band region is automatically set. In order to release the clutch, the torque transmission amount of the hydraulic torque transmission means is controlled to be zero.

(Problems to be Solved by the Invention) However, as described above, when the dead zone area for releasing the fluid clutch is always fixedly set with a constant reference rotation speed difference, the following problems occur. Occurs.

That is, although the stick-slip phenomenon as described above generally occurs in a low rotation speed difference region equal to or less than a predetermined reference rotation speed difference as described above, when the speed of change of the rotation speed difference itself is originally high. Naturally, the occurrence situation differs between late and late. For example, according to inspection and research conducted by the inventor of the present application, it has been found that the stick-slip phenomenon is relatively unlikely to occur when the change speed of the rotation speed difference is generally large even if the rotation speed difference itself is small. Therefore, originally, when the change speed of the rotation speed difference (the rotation speed difference change rate) is large, the reference rotation speed difference that partitions the dead zone described above is smaller than when the change speed is small. , May be lower.

However, if the dead zone in which the torque transmission control is prohibited is fixedly set to a constant value as described above without any consideration of the rate of change of the rotational speed difference as described above, the torque transmission amount Is forced to a state of zero, that is, a vehicle having a four-wheel drive system is forced to be in a two-wheel drive state more than necessary, thereby obtaining the safe and good running characteristics inherent in a four-rate drive vehicle. The possible operating area is narrowed.

(Means for Solving the Problems) The present invention has been made for the purpose of solving the above-described problems, and has the following means for solving the above problems. I have.

That is, a fluid torque transmission means for arbitrarily transmitting the torque generated from the power plant to the front wheel side or the rear wheel side,
A torque transmission amount control unit that controls a torque transmission amount of the fluid type torque transmission unit; a rotation speed difference detection unit that detects a rotation speed difference between the front wheel side and the rear wheel side; Rotation speed difference change rate detection means for detecting the change rate of the rotation speed difference between the front and rear wheels detected by the rotation speed difference detection means. The torque transmission amount of the fluid torque transmission unit is controlled, and the control amount of the torque transmission amount control unit is set to zero in a low rotation speed difference region where the rotation speed difference detected by the rotation speed difference detection unit is equal to or less than a predetermined difference. A dead zone area setting means for changing the dead zone width set by the dead zone area setting means in accordance with the rotation speed difference change rate detected by the rotation speed difference change rate detection means. It is way.

(Operation) According to the problem solving means of the present invention, first, a hydraulic torque transmitting means for arbitrarily transmitting torque generated from a power plant to a front wheel side or a rear wheel side, and a torque transmitting amount of the hydraulic torque transmitting means. , A rotational speed difference detecting means for detecting a rotational speed difference between the front wheel side and the rear wheel side, and detecting a rate of change of the rotational speed difference between the front wheel side and the rear wheel side. Rotation speed difference change rate detection means, and the torque transmission amount control means based on the rotation speed difference between the front and rear wheels of the vehicle detected by the rotation speed difference detection means. Is controlled.

Further, in the above configuration, in addition to the above, in a low rotation speed difference region in which the rotation speed difference detected by the rotation speed difference detection unit is equal to or less than a predetermined rotation speed difference, a dead zone region setting for setting the control amount of the torque transmission amount control unit to zero is set. Means for varying the dead zone width set by the dead zone setting means in accordance with the rotation speed difference change rate detected by the rotation speed difference change rate detection means.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to FIGS. 1 to 6.

FIG. 2 and FIG. 3 show the overall system and the configuration of main parts of a transmission torque control device for a four-wheel drive vehicle according to the first embodiment of the present invention.

First, in FIG. 2, reference numeral 10 denotes a power plant, which comprises an engine, a transmission, and the like. And the power plant
A front-side propeller shaft 14 is connected to the output shaft 12 via a predetermined gear train 13, and a hydraulic-type torque-changing-force variable clutch 15 such as the above-described viscous clutch, which is a hydraulic torque transmission means. The rear-side propeller shaft 16 is connected via the. The front side propeller shaft 14 is connected to a front wheel 18 via a final gear unit 17. Also, the rear side propeller shaft
16 is connected to a rear wheel 20 via a final gear unit 19.

In this manner, a front-wheel-side torque transmission path of the four-wheel drive vehicle of the present embodiment from the power plant 10 to the front wheel 18 via the output shaft 12, the gear train 13, the propeller shaft 14, and the final gear unit 17 is formed, In addition, a rear-wheel-side torque transmission path to the rear wheel via the power plant output shaft 12, the hydraulic variable clutch 15, and the final gear unit 19 of the power plant 10 is formed.

Then, by changing the pressure of the hydraulic oil applied to the hydraulic-type engagement force variable clutch 15 to change the amount of transmission torque (clutch engagement force) of the clutch 15, the front wheel
The torque distribution ratio between the 18 side and the rear wheel 20 side is adjusted.

Next, the configuration and operation of the hydraulic control system of the hydraulic engagement force variable clutch 15 will be described with reference to FIG. As shown in FIG. 3, the hydraulic oil in the oil tank 21 is:
After being sucked up by the oil pump 22, the oil is discharged at a predetermined pressure, and is supplied to the working oil chamber 15a of the above-mentioned hydraulic-type engagement force variable clutch 15 via an electromagnetically-controlled hydraulic control valve 23. Thereby, the pressure of the working oil supplied to the inside of the working oil chamber 15a of the hydraulic fastening force variable clutch 15 is adjusted. That is, in other words, the engagement force between the friction plates 15b of the hydraulic engagement force variable clutch 15 is controlled.

The input side (interface circuit) of the torque control unit 24 is connected to, for example, a vehicle speed sensor 25, a steering angle sensor 26, a rotational speed difference sensor 27, and the like. First, the vehicle speed sensor 25 detects the vehicle speed V of the vehicle and outputs a vehicle speed signal Sv corresponding to the vehicle speed. The steering angle sensor 26 detects a steering angle of the vehicle and outputs a steering angle signal Sα corresponding to the detected steering angle value α. The rotational speed difference sensor 27 detects a rotational speed difference between the torque input side and the output side of the hydraulic variable clutch 15, that is, a rotational speed difference Δn between the front side and rear side propeller shafts 14 and 16, and detects the rotational speed. The difference signal SΔn is output. In this case, the vehicle speed sensor
As 25, for example, it is convenient to use a rotation speed sensor that detects the rotation speed of the front-side propeller shaft 14. The rotation speed difference Δn is calculated by connecting a rotation speed sensor for detecting the rotation speed of the rear side propeller shaft 16 to the torque control unit 24, and based on the output value of this sensor, the torque control unit 24 The calculation may be performed within.

The torque control unit 24 first calculates a predetermined control current value i from a control map stored in advance using the above three signals, the vehicle speed signal Sv, the steering angle signal Sα, and the rotation speed difference signal SΔn. The calculated value of the applied current i is supplied and applied to the hydraulic control valve 23.

In the present embodiment, needless to say, the control current value i and the control hydraulic pressure P by the hydraulic control valve 23 are in a proportional relationship, and the control hydraulic pressure P and the transmission torque amount Tr by the hydraulic engagement force variable clutch 15 Are also proportional.
In this embodiment, a desired transmission torque characteristic with respect to the above-described change in the rotational speed difference Δn as shown in FIG. 4 can be obtained by the change in the value of the control current value i.

That is, as shown in FIG. 4, when the actual rotation speed difference Δn between the front and rear wheels is equal to or larger than a predetermined reference value Δno indicating a stable torque transmission characteristic in terms of the operation characteristics of the control system itself. The transmission torque amount Tr is controlled along the curve T = f (Δn) (in the region), and the transmission torque amount Tr is basically set to zero (0) in a dead zone region less than the predetermined reference value Δno.

Next, the transmission torque control operation of the present embodiment performed by the torque control unit 24 according to the flowchart of FIG. 5 will be described.

First reads the input signal Sv of the sensors described above in step S _1, S.alpha, the SΔn respectively.

Then the rate of change of the rotational speed difference Δn between the rear wheel 20 and the wheel 18 advances to step S ₂ (changing speed) DΔn (DΔn =
dΔn / dt).

The process proceeds to step S ₃ is followed on its, the calculated value DΔn
A reference value (threshold) Δno for partitioning the dead zone (region where Tr = 0, i = 0) is set in accordance with. As a result, the torque characteristic T = f (Δn) in FIG. 4 is, for example, any of the three arbitrary characteristics (a) to (c) having different dead zone region widths as shown in FIG. Crab is shifted. Then, the following torque control is performed based on the characteristics.

That is, when the setting of the dead zone area Δno is completed,
Then the process proceeds to step S _4, in step S _4, the actually detected rotational speed difference Δn between the front and rear wheels has is set by the characteristics of FIG. 6 above reference value Δno (Δno ₁ ~Δno ₃
) Is determined.

Then, as a result, in the case of NO (negative determination) is then target transmission torque Tr so as to prohibit the torque transmission as already mentioned the routine proceeds to step S ₆ correspondingly and sets the Tr = 0 The control current i supplied to the hydraulic control valve 23
Is controlled to i = 0. As a result, in this state, the engagement force of the hydraulic engagement force variable clutch 15 becomes zero, and the clutch 15 is eventually released.

On the other hand, in the case of YES (affirmative determination) in step S _4, the torque of FIG. 4 only as parameters rotational speed difference Δn between usual the front and rear wheels moved toward the step S ₅ unlike the The target torque is set so that the torque Tr on the characteristic T = f (Δn) is obtained, and the hydraulic control valve is set.
23, the corresponding applied current i (i = Tr) is supplied.

(Effect of the Invention) As described above, the transmission torque control device for a four-wheel drive vehicle of the present invention includes a fluid torque transmission unit that arbitrarily transmits the torque generated from the power plant to the front wheels or the rear wheels. A torque transmission amount control unit for controlling a torque transmission amount of the fluid type torque transmission unit; a rotation speed difference detection unit for detecting a rotation speed difference between the front wheel side and the rear wheel side; and a front wheel side and a rear wheel side. And a rotation speed difference change rate detecting means for detecting a change rate of a rotation speed difference between the front wheel and the rear wheel detected by the rotation speed difference detecting means. Controlling the torque transmission amount of the fluid type torque transmission means, and controlling the torque transmission amount control means by the torque transmission amount control means in a low rotation speed difference region where the rotation speed difference detected by the rotation speed difference detection means is equal to or smaller than a predetermined difference. Is set to zero, and the dead zone width set by the dead zone setting unit is made variable according to the rotation speed difference change rate detected by the rotation speed difference change rate detection unit. It is characterized by the following.

That is, in this configuration, first, a hydraulic torque transmitting means for arbitrarily transmitting the torque generated from the power plant to the front wheel side or the rear wheel side, and a torque transmitting amount controlling means for controlling the torque transmitting amount of the hydraulic torque transmitting means A rotation speed difference detecting means for detecting a rotation speed difference between the front wheel side and the rear wheel side,
A rotation speed difference change rate detecting means for detecting a change rate of a rotation speed difference between the front wheel side and the rear wheel side, and a speed difference between the front and rear wheels of the vehicle detected by the rotation speed difference detection means; The torque transmission amount of the torque transmission means is controlled by the torque transmission amount control means on the basis of the rotational speed difference.

Further, in the above configuration, in addition to the above, in a low rotation speed difference region in which the rotation speed difference detected by the rotation speed difference detection unit is equal to or less than a predetermined rotation speed difference, a dead zone region setting for setting the control amount of the torque transmission amount control unit to zero is set. Means for varying the dead zone width set by the dead zone setting means in accordance with the rotation speed difference change rate detected by the rotation speed difference change rate detection means.

Therefore, according to the configuration of the present invention, it is possible to arbitrarily change the width of the dead zone region depending on the magnitude of the rate of change of the rotational speed difference, based on the rotational speed difference between the front and rear wheels, This has the advantage that the four-wheel drive area can be expanded accordingly.

[Brief description of the drawings]

FIG. 1 is a diagram corresponding to claims of the present invention, and FIG. 2 is a schematic block diagram showing a configuration of a torque transmission path of a basic system in a transmission torque control device for a four-wheel drive vehicle according to an embodiment of the present invention. FIG. 3 is a hydraulic circuit diagram showing a specific structure of a hydraulic control unit in the hydraulic system shown in FIG. 2, FIG. 4 is a basic torque map used in the embodiment of the present invention, and FIG. FIG. 6 is a flowchart showing the torque control operation of the embodiment, and FIG. 6 is a correction torque map used in the control operation of FIG. 10 Power plant 12 Power plant output shaft 13 Gear train 14 Front propeller shaft 15 Hydraulic coupling force variable clutch 16 Rear propeller shaft 18 Front wheel 20 Rear wheel 23 …… Hydraulic control valve 24 …… Torque control unit

Claims (1)

(57) [Claims] 1. A hydraulic torque transmitting means for arbitrarily transmitting a torque generated from a power plant to a front wheel side or a rear wheel side;
A torque transmission amount control unit that controls a torque transmission amount of the fluid type torque transmission unit; a rotation speed difference detection unit that detects a rotation speed difference between the front wheel side and the rear wheel side; Rotation speed difference change rate detection means for detecting the change rate of the rotation speed difference between the front and rear wheels detected by the rotation speed difference detection means. The torque transmission amount of the fluid torque transmission unit is controlled, and the control amount of the torque transmission amount control unit is set to zero in a low rotation speed difference region where the rotation speed difference detected by the rotation speed difference detection unit is equal to or less than a predetermined difference. A dead zone area setting means for changing the dead zone width set by the dead zone area setting means in accordance with the rotation speed difference change rate detected by the rotation speed difference change rate detection means. Transmission torque control device for a four-wheel drive vehicle, characterized in that as.