JPH0538960A - Power transmission control device for vehicle - Google Patents

Abstract

PURPOSE:To prevent a tire slip and improve the fuel consumption performance by providing a control means capable of changing a differential limiting characteristic, and reducing the differential limiting quantity of a center differential gear at the normal travel time by this control means so as to reduce travel resistance, whereas increasing the above-mentioned differential limiting quantity in a power mode. CONSTITUTION:A four-wheel drive vehicle is provided with an automatic transmission 2, differential limiting mechanism EMCD, a center differential gear 3 and a power train P, and the automatic transmission 2 can select out of plural travel modes. The respective differential limiting mechanisms of a center differential gear 3, a front differential gear 7 and a rear differential gear 12 are current-controlled by the output current of a differential limiting controller 20. When a power mode or a hold mode is selected by the automatic transmission 2, the differential limiting quantity of the rear differential gear 12 is controlled to be large at the low output time of an engine, small at the medium output time, and large at the high output time. At the decelerating time by an engine brake, fuel consumption at the medium output time of the engine is improved while maintaining travel stability, and a tire slip at the high output time is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle power transmission control device provided with a differential limiting mechanism capable of varying a differential limiting amount.

[0002]

2. Description of the Related Art Output from a transmission of a vehicle is transmitted to a front wheel drive system and a rear wheel drive system via a center differential device (hereinafter referred to as "center differential"), and to the front wheel drive system and the rear wheel drive system. There is known a four-wheel drive vehicle in which a differential limiting mechanism is provided in the center differential in order to transmit and selectively directly connect the front wheel drive system and the rear wheel drive system.

In the four-wheel drive vehicle disclosed in Japanese Unexamined Patent Publication No. 62-244717, the center differential differential limiting mechanism is controlled in accordance with the wheel rotation speed and the gear stage of the transmission, and the vehicle is controlled. This prevents the occurrence of the tight brake phenomenon when the vehicle is turning at low speed and the tire slip when starting.

By the way, recent automatic transmissions for automobiles are
It is possible to select between the economy mode, which gives priority to fuel efficiency and quietness, and the power mode, which gives priority to acceleration and which shifts the shift line to a higher speed side than the economy mode. In some cases, a hold mode for prohibiting the automatic shift and holding a predetermined shift stage is provided for the operation. Also, in a four-wheel drive vehicle,
Conventionally, in addition to the main transmission, by changing the gear ratio, a high speed running mode (Hi) and a low speed running mode (Lo)
Many are equipped with an auxiliary transmission that can be selected from.

[0005]

However, in the case of a four-wheel drive vehicle capable of selecting various driving modes as described above, if the control of the differential limiting mechanism of the center differential is not appropriate, the fuel efficiency may be deteriorated. However, there is a problem in that the running stability is hindered when running with engine braking.

Therefore, the present invention makes it possible to improve the fuel efficiency and the running stability of a vehicle having various driving modes by appropriately setting the differential limiting characteristics of the differential limiting mechanism. An object is to provide a power transmission control device designed.

[0007]

That is, according to the present invention,
When the power mode and the hold mode are selected in the automatic transmission, and when the low travel mode Lo is selected in the auxiliary transmission, the center differential is set to be locked so as to solve the above problem.

[0008]

According to the present invention, since the differential limiting amount of the center differential is reduced during normal traveling, traveling resistance is reduced and fuel consumption characteristics are improved. Further, in the power mode or the hold mode, since the differential limit amount of the center differential is increased, it is possible to prevent tire slip at the time of sudden start, and to secure running stability at low speed using the engine brake. ..

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, a four-wheel drive vehicle includes an engine 1, an automatic transmission 2, a transfer device 4 including a center differential 3 having an electromagnetic clutch type differential limiting mechanism (EMCD) and an auxiliary transmission. The power train P has the following structure, and the torque input to the center differential 3 is distributed and output to the front wheel side propeller shaft 5 and the rear wheel side propeller shaft 6. The automatic transmission 2 is
The economy mode, the power mode, and the hold mode can be selected.

The torque of the front wheel propeller shaft 5 is input to a front differential 7 equipped with an electromagnetic clutch type differential limiting mechanism (EMCD), further transmitted to a left front wheel 9 via a left front axle shaft 8, and It is adapted to be transmitted to the right front wheel 11 via the right front axle shaft 10. On the other hand, the torque of the rear wheel side propeller shaft 6 is the electromagnetic clutch differential limiting mechanism (EMC).
D) is input to the rear differential 12, and further transmitted to the left rear wheel 14 via the left rear axle shaft 13 and to the right rear wheel 16 via the right rear axle shaft 15. Center differential 3,
The electromagnetic clutch differential limiting mechanism (EMCD) provided in each of the front differential 7 and the rear differential 12 is configured to control each differential limiting amount by the current output from the differential limiting amount controller 20. ..

The differential limiting amount controller 20 is a digital controller composed of a microcomputer, and is detected by a throttle sensor 21 provided for a throttle valve (not shown) in the intake passage of the engine 1. Brake switch 22 provided for a throttle opening signal TVO and a brake pedal (not shown)
Brake ON / OFF signal generated by the transmission 2
A mode signal output from the mode selection switch 23 provided in the vehicle, a signal output from the Hi-Lo changeover switch 30 of the auxiliary transmission, and an ABS controller 24 for controlling the antilock brake system (ABS). The ABS operation signal or the like is input to the differential limiting amount controller 20.

Further, the left front axle shaft 8
The front left wheel speed (rotational speed) NfL detected by the first rotation speed sensor 25 provided for the right front wheel speed (detected by the second rotation speed sensor 26 provided for the right front axle shaft 10 ( Rotation speed) NfR,
Third provided on the left rear axle shaft 13
The left rear wheel speed (rotation speed) NrL detected by the rotation speed sensor 27 and the right rear wheel speed (rotation speed) NrR detected by the fourth rotation speed sensor 28 provided for the right rear axle shaft 15 are respectively represented. The signal is AB
Differential limiting amount controller 2 via S controller 24
It is designed to be input to 0. The differential limiting amount controller 20 uses these signals as input information by a method described later, and uses the center differential 3, the front differential 7, and the rear differential 12.
The respective differential limiting mechanisms are current-controlled to improve the running stability, fuel efficiency, etc. of this four-wheel drive vehicle. The differential limiting force controller 20 is provided with an operating knob 29 capable of selecting four control modes of an auto mode Auto, a center differential lock mode C, a rear differential lock mode R, and a front differential lock mode F.

FIG. 2 is a flowchart showing a routine for calculating the vehicle body speed Vsp. In step S1, four wheel speeds (rotational speeds) NfL, NfR, NrL and NrR are input. Then, in step S2, the minimum value of the four wheel speeds is defined as the vehicle body speed Vsp.

The characteristic operation of the power transmission control system in this embodiment is shown in the characteristic diagrams of FIGS. 3 to 5 and the flow chart of FIG.

FIG. 3 shows the vehicle speed V in the automatic mode.
It is a figure which shows three-dimensional relation of sp, throttle opening TVO, and control current value I of center differential 3 of three persons. In FIG. 3, when the throttle opening TVO increases from zero, the control current value I is zero until it reaches a certain value. The range in which the control current value I is zero is expanded as the vehicle body speed Vsp increases. After that, the control current value I increases in proportion to the increase of the throttle opening and reaches the maximum value Imax.
Is shown in.

Further, in FIG. 3, a case where the power mode is selected in the automatic transmission 2 or a case where the low speed traveling mode Lo is selected in the auxiliary transmission is shown by a solid line, and the economy mode is selected in the automatic transmission 2. The case where the high speed traveling mode Hi is selected in the sub transmission or the case where the sub transmission is selected is indicated by a broken line. That is, in the power mode or the low speed traveling mode Lo, the region in which the control current value I is zero is reduced as compared with the economy mode or the high speed traveling mode Hi, and the differential limiting amount of the center differential 3 is increased. There is.

FIG. 4 shows the throttle opening T in the automatic mode during normal running when the vehicle speed Vsp is constant.
In the map showing the relationship between VO and the control current value Ic of the center differential 3 (or the control current value Ir of the rear differential 12), Ic = 0 (or Ir = 0) is set while the throttle opening TVO is equal to or less than α. , Throttle opening TVO
In the region between α and A, Ic (or Ir) increases in proportion to the increase in TVO and reaches the upper limit value Imax. When Ic (or Ir) reaches Imax, the center differential 3 (or rear differential 12)
Are fully locked and the differential is stopped.

FIG. 5 shows a map showing the throttle opening TVO and the control current value Ir of the rear differential 12 in the hold mode in comparison with FIG. In the hold mode, the center differential control current value Ic is set to Imax.

In FIG. 5, the throttle opening TVO is α and β.
In the region between the throttle opening TVO and β, B is set as Ir = 0 only in the region between
Ir increases in proportion to the decrease of O and reaches a predetermined value Ih. That is, in the hold mode, the differential limiting amount of the rear differential 12 is controlled to be large when the engine output is low, small when the engine output is high, and large when the engine output is high. As a result, it is possible to improve fuel efficiency at the time of engine output and prevent tire slip at the time of high output, while maintaining running stability in a decelerated state using the engine brake.

FIG. 6 is a flowchart showing the above control operation. First, in step S11, the output of the mode switch 23 is input, and in the next step S12, it is checked whether the hold mode is set. Then, in the hold mode, Ic is set to Imax in step S13, and Ir is set as shown in FIG.
The map value of. In modes other than the hold mode, Ic and Ir are set to the map values of FIG. 4 in step S14.

[Brief description of drawings]

FIG. 1 is a system configuration diagram of a power transmission system of a four-wheel drive vehicle including a power transmission control device according to the present invention.

FIG. 2 is a flowchart of a vehicle body speed calculation routine.

FIG. 3 is a diagram three-dimensionally showing a relationship between a vehicle body speed, a throttle opening, and a control current value of a center differential.

FIG. 4 is a map showing a relationship between a throttle opening and a center differential control current value during normal traveling.

FIG. 5 is a map showing a relationship between a throttle opening and a rear differential control current value in a hold mode.

FIG. 6 is a flowchart for determining a control current value.

[Explanation of symbols]

 1 engine 2 transmission 3 center differential 4 transfer device 7 front differential 9 left front wheel 11 right front wheel 12 rear differential 14 left rear wheel 16 right rear wheel 20 differential limit controller 21 throttle sensor 22 brake switch 23 mode selection switch 24 ABS controller 25 28 Revolution sensor

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yu Shiraishi 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Motor Corporation

Claims (7)

[Claims] 1. A differential device having a differential limiting mechanism, control means for changing the differential limiting characteristic of the differential limiting mechanism, and running mode selecting means for selecting a plurality of running modes. A power transmission control device for a vehicle, wherein the control means changes the differential limiting characteristic in accordance with selection of the traveling mode. 2. The vehicle includes an automatic transmission capable of selecting a hold mode in which automatic shift is prohibited and a predetermined shift speed is held, and the control means sets a differential limit amount in the hold mode. 2. The power transmission control device according to claim 1, wherein the differential limiting characteristic is changed so as to be increased more than in other traveling modes. 3. The vehicle comprises an auxiliary transmission capable of switching a speed ratio between a high speed traveling mode and a low speed traveling mode, and the control means controls the differential limiting amount of the auxiliary transmission in the low speed traveling mode. 2. The power transmission control device according to claim 1, wherein the differential transmission characteristic is changed so as to be increased more than in the high speed traveling mode. 4. The vehicle is provided with an automatic transmission capable of selecting a first traveling mode in which fuel consumption is prioritized and a second traveling mode in which acceleration is prioritized, and the limiting means is provided in the second traveling mode. The power transmission control device according to claim 1, wherein the differential limiting characteristic is changed so as to increase the differential limiting amount as compared with that in the first traveling mode. 5. The plurality of traveling modes include a traveling mode in which the differential limiting amount is small when the engine load is low and a traveling mode in which the differential limiting amount is large when the engine load is low. 1. The power transmission control device according to 1. 6. The running mode in which the differential limiting amount is large when the engine load is low is a running mode in which the differential limiting amount is small when the engine is under medium load and the differential limiting amount is large when the engine is under heavy load. The power transmission control device according to claim 5. 7. A center differential in a traveling mode in which the vehicle is configured to transmit power from a transmission to a front wheel drive system and a rear wheel drive system via a center differential device, and in a traveling mode in which the differential limiting amount is increased. The power transmission control device according to any one of claims 2 to 4, wherein the device is locked and the rear wheel differential device is controlled according to a predetermined differential limiting characteristic.