JPS6277230A - Automatic shifting device for 4-wheel-drive vehicle - Google Patents

Abstract

PURPOSE:To prevent a tight corner braking phenomenon, by furnishing a device to shift to the 4-wheel-drive after detecting a tire lock or its omen. CONSTITUTION:A driving force from an engine is delivered to a torque converter 1, a main transmission 2, and a sub-transmission 3, and, the output is transmitted to a frontwheel driving shaft 7 through a differential unit 6, and drives a 2-wheel running. When a braking is exercised in the 2-wheel running, and a tire lock condition or its omen is detected, a shifting clutch 13 is opened automatically to shift to the 4-wheel-drive. Therefore, a tire lock is prevented and a reduction of braking force is prevented to reduce the braking distance, while preventing a tight corner braking phenomenon, to make it possible to prevent an unreasonable force inflicted to the transmission system or abrasion of tires.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention provides a part-time four-wheel drive vehicle capable of switching between two-wheel drive and four-wheel drive to prevent tire locking. This invention relates to an automatic switching device.

[Conventional technology]

In general, part-time 4-wheel drive vehicles that can be switched between 2-wheel drive and 4-wheel drive normally drive by transmitting drive power to only the front wheels or only the rear wheels, but when driving under road conditions such as rough roads or frozen roads, or in sudden situations, It is also possible to switch to four-wheel drive based on driving conditions such as acceleration and sudden deceleration.

By the way, when braking to stop the vehicle, in the case of four-wheel drive, the front axle and rear axle are mechanically connected, so
A tire lock on only one wheel, where one wheel stops, cannot occur, but if you are driving in two-wheel drive,
Since the front axle and the rear axle rotate independently, tire lock occurs, resulting in a decrease in the coefficient of friction between the road surface and the tires, resulting in a longer control distance.

For this reason, conventionally, a so-called anti-rotation brake has been employed, which electrically detects the state of tire lock or a sign thereof and reduces the braking force to release or prevent tire lock. It also detects the brake signal and when braking,
A mechanism to prevent tire locking by switching to four-wheel drive has also been adopted [the problem that the invention aims to solve]. However, with conventional anti-lock brakes, the braking force itself is weaker than normal braking force and the braking distance is shortened. There was a problem that the length of the Furthermore, in a mechanism that detects a brake signal and switches to four-wheel drive during braking to prevent tire locking, a problem has arisen in that the vehicle is always in four-wheel drive during braking during normal driving. In other words, during four-wheel drive, the front wheels and rear wheels are directly connected via the power transmission system, so when making large turns at low speeds, the difference in rotation between the front and rear wheels cannot be absorbed, resulting in the phenomenon of tight corner braking. ,
The drawbacks were that excessive force was applied to the power transmission system and the tires wore out.

The present invention solves the above-mentioned problems, and aims at increasing braking force while preventing the phenomenon of tight corner braking, and providing a four-wheel drive system that does not apply unreasonable force to the power transmission system. The object of the present invention is to provide an automatic switching device for a vehicle.

[Means for solving problems]

To this end, the automatic switching device for a four-wheel drive vehicle of the present invention directly transmits engine power to one of the front wheels or the rear wheels, and also transfers the power from the engine to the other of the front wheels or rear wheels by operating a clutch for switching between two wheels and four wheels. In a four-wheel drive vehicle that also transmits 2
The special feature of this system is to automatically switch to four-wheel drive by detecting the state of tire lock or a sign of tire lock during braking in wheel drive.

[Action and effect of the invention]

The automatic switching device for a four-wheel drive vehicle of the present invention detects the state of tire lock or a sign of tire lock during braking in two-wheel drive and automatically switches to four-wheel drive to prevent tire lock. In addition to preventing a decrease in the braking distance and preventing the phenomenon of tight corner braking, it is possible to solve the problems of excessive force acting on the power transmission system and tire wear.

〔Example〕

Examples will be described below with reference to the drawings.

FIGS. 1 and 2 are diagrams for explaining each embodiment of the present invention, and FIG. 3 is a diagram showing a power transmission system of a part-time four-wheel drive vehicle. In the figure, A is an automatic transmission, l is a torque converter, 2 is a main transmission, 3 is a sub-transmission, 5 is a drive gear,
6 is a front differential device, 7 is a front wheel drive shaft, 9 is a propeller shaft for rear wheel drive, 10 is a bevel gear, 11 is a rear export force member, 12 is a rear wheel transmission device, 13 is a 2-wheel to 4-wheel switch This shows the clutch for use.

Generally, two-wheel drive with either front or rear wheels and n:I
If the engine is mounted on the front side of a part-time 4-wheel drive vehicle that is capable of 4-wheel drive using both transmission and transportation, the power from the engine will be transferred to automatic transmission A, as shown in Figure 3. The output is transmitted to the provided torque converter 1, main transmission 2, and auxiliary transmission 3, and the output is transmitted to the front wheels via a drive gear 5, and then a front differential 6 installed integrally with the drive gear 5. The power is transmitted to the drive shaft 7 and two-wheel drive is performed. On the other hand, a rear wheel drive propeller shaft 9 is connected to a rear export force member 11 via a bevel gear 10, and the rear export force member 11 and the drive gear 5
A rear wheel transmission device 12, which is integrally installed in 9 to drive the rear wheels, resulting in four-wheel drive. Then, the driver judges from the road surface situation, driving conditions, etc.
By operating the wheel-four-wheel switching clutch 13, two-wheel drive during normal driving or four-wheel drive driving on frozen roads or during sudden acceleration/deceleration is performed.

Furthermore, when braking in two-wheel drive driving, the system detects the state of tire lock or a sign thereof and automatically operates the two-wheel to four-wheel switching clutch 13 to switch to four-wheel drive, thereby preventing a drop in tire grip force. This shortens braking distance.

Next, a control method during braking will be explained with reference to flowcharts shown in FIGS. 1 and 2. First, the process flow will be explained using the embodiment shown in FIG. 2. (1) When the vehicle starts and runs, it is checked whether the solenoid that operates the clutch for switching between two wheels and four wheels is OFF (two-wheel drive). If NO (4-wheel drive), repeat until YES, and if YES, then process (2).

■ Check whether the foot brake is ON. N
In the case of O, the process ``■'' is performed, and in the case of YES, the process ``■'' is performed.

■ Turn off the solenoid and return to the process in ■.

■ Input the tire rotation speed S and then perform the process in ■.

(2) S#0, that is, check whether the rotational speed of the tire is 0 or near 0 (tire lock state or its precursor state a). In the case of No, return to the process of ■,
If YES, then process (2) is performed.

■ Set the solenoid to 0N (4-wheel drive) and return to process ■.

Next, the flow of processing will be explained using the embodiment shown in FIG. The processing of 0, ■, ■, and O in Figure 2 is the process of ■, ■ in Figure 1.
, ■, and ■, so the explanation will be omitted.

[Yes] Input the wheel deceleration a and brake pressure p calculated from the change in the wheel rotation speed, and then perform the process (2).

(2) Calculate the deceleration f(p) of the wheels or vehicle from the brake pressure p, and then perform the [phase] process.

Check once if @a>f(p). That is, it is determined whether the deceleration in the state of tire lock or its precursor is greater than the deceleration in normal braking. In the case of NO, the process returns to the process of @, and in the case of YES, the process of O is performed.

This switches to four-wheel drive.

As is clear from the above explanation, according to the present invention, since the state of tire lock or a sign thereof is detected and the system switches from two-wheel drive to four-wheel drive, the control is more effective than with conventional anti-lock brakes. This prevents a decrease in power and improves braking effectiveness.

In addition, because the system switches to 4-wheel drive only when the tires are locked or a sign of locking, tight corner braking does not occur and unreasonable force is applied to the power transmission system, compared to a system that always switches to 4-wheel drive when braking. This can prevent tire wear and tear.

It should be noted that the present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made. For example, in the above embodiment, the deceleration is detected based on the number of rotations of the wheels, and the state of tire lock or its precursor is detected by comparing it with the deceleration corresponding to the brake pressure. It is also possible to directly detect the deceleration of the vehicle and compare it with the deceleration corresponding to the brake pressure to detect the state of tire lock or its precursor.

Also, when calculating the deceleration corresponding to the brake pressure,
It is possible to automatically detect the vehicle weight due to occupants and calculate the deceleration from the brake pressure and vehicle weight.Furthermore, a table of deceleration corresponding to the brake pressure can be set and the actual wheel rotation speed and acceleration can be calculated. The deceleration may be compared with the deceleration detected based on the meter.

[Brief explanation of drawings]

FIGS. 1 and 2 are diagrams for explaining each embodiment of the present invention, and FIG. 3 is a diagram showing a power transmission system of a part-time four-wheel drive vehicle. A... Automatic transmission, 1... Torque converter, 2...
... Main transmission, 3... Sub-transmission, 5... Drive gear,
6... Front differential device, 7... Front wheel drive shaft, 9
... Rear wheel drive propeller shaft, 10 ... Bevel gear, 11 ... Rear export force member, 12 ... Rear wheel transmission device,
13...Clutch for switching between 2 wheels and 4 wheels. Patent Applicant Aisin Warner Co., Ltd. Agent Patent Attorney Ryukichi Abe Figure 2

Claims (3)

[Claims] (1) A two-wheel drive vehicle in which engine power is directly transmitted to one of the front wheels or the rear wheels and is also transmitted to the other of the front wheels or rear wheels by operating a clutch for switching between two and four wheels. An automatic switching device for a four-wheel drive vehicle, which detects a state of tire lock or a sign of tire lock during braking and automatically switches to four-wheel drive. (2) The automatic switching device for a four-wheel drive vehicle according to claim 1, wherein the state of the tire lock or a sign of the tire lock is detected based on the number of rotations of the wheels. (3) The state of the tire lock or the sign of the tire lock is determined by comparing the deceleration of the wheels or the vehicle with the deceleration corresponding to the brake pressure. Automatic switching device for wheel drive vehicles.