JPH01314630A - Front/rear wheel drive car - Google Patents

Abstract

PURPOSE:To make effective use of engine brake at the time of using other types of braking by making the coefficient of friction against grounded road surfaces different between right and left wheels, and thereby making a clutching means connecting the respective driving force transfer systems of the front and rear wheels disengaged only when the vehicle brake is applied. CONSTITUTION:A power unit 11 is connected with a front differential gear 12F, and is concurrently connected with a rear differential gear 12R via a propel ler shaft 15. And a transfer clutch 18 is arranged to the propeller shaft 15. In addition, the transfer clutch 18 is controlled by a controller 17 based on respective detected signals by respective revolution speed sensors 16L and 16R provided for a right and left front wheel 14FL and 14FR, and a brake sensor 19. In this case, when the respective coefficients of friction of the right and left front wheels 14FL and 14FR against grounded road surfaces are different each other, and when the vehicle brake is applied, control is assumed in such a way that the transfer clutch 18 is disengaged.

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention relates to a front and rear wheel drive vehicle that can run by driving both front wheels and rear wheels. The present invention relates to a front and rear wheel drive vehicle that improves braking performance by disconnecting the drive power transmission system between the front and rear wheels during different braking operations.

(Prior Art) In front-wheel drive vehicles, the drive power transmission system to the front wheels and the drive power transmission system to the rear wheels are generally connected via a transfer clutch such as a hydraulic clutch or a dog clutch. The driving force distribution ratio between the front and rear wheels is controlled according to driving conditions such as braking.

Conventionally, as this type of front and rear wheel drive vehicle, for example,
The one described in Japanese Patent No. 9-188731 is known. This front and rear wheel drive vehicle has a transfer clutch interposed in series with a device similar to a differential between the front and rear wheel drive power transmission systems, and this device is automatically shut off when the vehicle is braked.

(Problem to be Solved by the Invention) However, in the conventional front and rear wheel drive vehicle as described above, the drive power transmission system of the front and rear wheels is disconnected during braking regardless of the road surface condition. There is a problem in that one of the front wheels or the rear wheels is separated from the engine and becomes free, making it impossible to obtain a sufficient engine braking effect.

This invention has been made in view of the above problems, and only when it is particularly required to disconnect the front and rear drive power transmission systems during braking, the front and rear drive power transmission systems are disconnected, and the other The purpose is to effectively utilize engine braking when braking.

(Means for Solving the Problems) The present invention provides a front and rear wheel drive vehicle in which a drive power transmission system to the front wheels and a drive power transmission system to the rear wheels are connected via a clutch means. In addition to detecting the difference in the coefficient of friction of the road surface that is in contact with the ground, the braking state of the vehicle is also detected, and when the friction coefficients of the road surface that the left and right wheels are in contact with are different and the vehicle is in the braking state, the clutch means is released. The main point is to

(Function) The front and rear wheel drive vehicle according to the present invention has a problem in that the drive power transmission system of the front and rear wheels is disconnected only when braking on a road surface where the friction coefficients of the road surfaces on which the left and right wheels contact are different. In this case, the drive power transmission system for the front and rear wheels is not separated,
A sufficient engine braking effect can be obtained. When braking is performed on a road surface where the friction coefficients of the road surfaces on which the left and right wheels contact are different, the drive power transmission systems for the front and rear wheels are disconnected, thereby improving the safety of the vehicle.

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

1 and 2 show a front and rear wheel drive vehicle according to an embodiment of the present invention, with FIG. 1 being a schematic diagram of a power transmission system, and FIG. 2 being a flowchart.

In FIG. 1, reference numeral 11 denotes a power unit in which an engine and a transmission are assembled together, and the output shaft of this power unit 11 is connected to a front differential 12F. The front differential 12 has axles 13FL and 13FR on the left and right, and the left and right front wheels 1 are connected to each other via the axles 13FL and 1.3FR.
4FL and 14FR, and is also connected to a propeller shaft 15 at the rear, through which it is connected to a rear differential 12R. The front differential 12F allows the power of the engine to be differentially distributed to the left and right front wheels 14FL and 14FR.
The power of the engine is transmitted to the propeller shaft 15. Axles 13FL and 13FR each have a front wheel of 14FL.
, 14FR are provided with rotational speed sensors 16L and 16R for detecting rotational speeds WFL and WFR, and these rotational speed sensors 16L and 16R are connected to a controller 17, which will be described later.

A transfer clutch 18 made of a hydraulic multi-plate clutch, a dog clutch, or the like is interposed on the propeller shaft 15. The rear differential 12R has axles 13RL and 13RR connected to its left and right sides, respectively.
4RL.

14RR. This rear differential 12R is composed of a viscous coupling having a differential limiting function and also functions as a center differential, between the left and right rear wheels 14RL and 14RR and between the front and rear wheels 14FL.

The differential is limited according to the rotational speed difference between 14FR, 14RL, and i4RR. In addition, a transfer clutch 18 is attached to the propeller shaft 15 as a center differential.
It is also possible to provide a differential mechanism such as a viscous coupling in series.

The controller 17 is composed of a microcomputer and the like, and is connected to the brake sensor 19 that detects the braking state together with the aforementioned transfer clutch 18 and rotational speed sensor 16L116R. Brake sensor 1
Reference numeral 9 includes a stroke switch that detects the stroke of the brake pedal or an acceleration sensor that detects acceleration in the longitudinal direction, and outputs a signal representing braking of the vehicle to the controller 17. The controller 17 calculates and processes the signals output from each of the above-mentioned sensors 16L and 16R119,
The fastening force of the transfer latch 18 is controlled according to the result of this calculation.

In this front and rear wheel drive vehicle, the microcomputer of the controller 17 repeatedly executes a series of processes shown in the flowchart of FIG. 2 to control the transfer clutch 18. First, in step P1, the transfer clutch 18 is engaged, and then in step P2, the rotational speed WFL of the left and right front wheels 14FL, 14FR is determined from the output signals of the respective rotational speed sensors 16L, 16H.

Load WFR. Then, in step P3, the absolute value of the difference between the rotational speeds WFL and WFR is △W-(△W=lW
It is determined whether FL-WFR+) exceeds a predetermined value K, that is, whether the friction coefficients of the road surface that the left and right front wheels 14FL and 14FH touch are different. This step P
In step 3, when it is determined that the absolute value ΔW is less than or equal to a predetermined value, the process from step P1 is repeated again, and
If it is determined that the absolute value ΔW exceeds the predetermined value K, the processing from step P4 onwards is performed. Note that the above-mentioned predetermined value can also be set as a function of the steering angle by detecting the steering angle.

In step P4, it is determined whether the vehicle is in a braking state based on the output signal of the brake sensor 19, and if the vehicle is not in a braking state, the process from step P1 is repeated; If so, the transfer clutch 18 is released in step P5. And step P5
After the process, step P4 is performed again, and the transfer clutch 18 is maintained in the disengaged state while the vehicle is in the braking state.

As mentioned above, in the front and rear wheel drive vehicle of this embodiment,
When the rotational speed difference △W between the left and right front wheels 14FL and 14FR exceeds a predetermined value, it is determined that the friction coefficients of the road surfaces in contact with the left and right front wheels 14FL and 14FR are different, and it is determined that the vehicle is in a braking state. Only, transfer clutch 1
Separate 8. Therefore, when braking on a road surface with a different friction coefficient between the front wheels 14FL and 14FR, the transfer clutch 18 disconnects the rear wheels 14RL and 14RR from the front wheels 14FL and 14FR and the power unit 11, improving vehicle stability. I can figure it out. And front wheel 1
During braking on a road surface where the friction coefficients of the ground contact surfaces of 4FL and 14FR are equal, the transfer clutch 18 maintains the connected state, and the rear wheels 14RL and 14RR are connected to the front wheels 14FL and 14FR.
Since the 4FR and the power unit 11 are connected, a sufficient engine braking effect can be obtained.

In addition, in the above-mentioned example, the front wheel 14FL.

Rotational speed sensors 16L and 16R are provided on the 14FR side, and the front wheel 14FL is determined by the rotational speed difference between the front wheels 14FL and 1'4F'R.
, to determine the difference in the friction coefficient of the ground contact surface of 14FR,
When the rear differential 12R is a normal differential mechanism that does not have a differential limiting function, the rear wheel is 14RL.

A rotational speed sensor may be provided on the 14RR side, and the difference in the friction coefficient of the road surface can also be detected by providing sensors for detecting road surface conditions such as ultrasonic sensors on the left and right wheels.

(Effects of the Invention) As explained above, according to the front and rear wheel drive vehicle according to the present invention, the drive power transmission system to the front wheels and the rear In order to disconnect the drive power transmission system to the wheels, it is used during other braking.
Engine braking can be used effectively, and high stability can be achieved when braking on road surfaces with different friction coefficients for the left and right wheels.

[Brief explanation of the drawing]

1 and 2 show a front and rear wheel drive vehicle according to an embodiment of the present invention, in which FIG. 1 is a schematic diagram of a power transmission system, and FIG. 2 is a flowchart. 11...Power unit 12F...Float differential 12R...
Rear differential 14FL, FR...Front wheels 14RL, RR...Rear wheels 15...Propeller shafts 16L, 16R...Rotational speed sensor 17...Controller 1 Transfer clutch (clutch means) 1
9...Brake sensor patent application person Honda Motor Co., Ltd. representative
Person Patent attorney 2 1) Customer - Immediate question Patent attorney
Kuni Ohashi Production volume Patent attorney Small
Yama Yu1771

Claims (1)

[Scope of Claims] 1. In a front and rear wheel drive vehicle in which a driving force transmission system to the front wheels and a driving force transmission system to the rear wheels are connected via a clutch means, the coefficient of friction of the road surface that the left and right wheels contact and detects the braking state of the vehicle, and disengages the clutch means when the friction coefficients of the road surfaces in contact with the left and right wheels are different and the vehicle is in the braking state. Front and rear wheel drive vehicle. 2. The front and rear wheel drive vehicle according to claim 1, wherein the difference in the coefficient of friction of the road surface that the left and right wheels touch is determined by detecting a rotational speed difference between the left and right wheels. .