JPH04278834A - Two-wheel drive-four-wheel drive control method - Google Patents

Abstract

PURPOSE:To avoid danger and prevent the generation of the tight corner brak ing phenomenon in case of the sharp advance to a low mu value road, in the two-wheel drive-four-wheel drive selection control for a transfer device. CONSTITUTION:In ordinary traveling, the traveling is performed always in the two-wheel drive, while if the revolution difference between the front and rear wheels becomes over a certain value, switching to the four-wheel drive is performed, and the four-wheel drive state is maintained for a certain time.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to two types of transfer devices.
The present invention relates to a wheel drive-four wheel drive switching control method.

0002

2. Description of the Related Art Among hydraulic multi-disc switching type transfer devices for four-wheel drive vehicles, there is one in which switching between 2WD and 4WD is performed using a manual two-wheel drive (2WD)-four-wheel drive (4WD) switch. In other words, when the 2WD shift position switch is manually turned on, the solenoid valve is turned on, hydraulic pressure is drained, the shift valve is inactive and the oil passage is closed, line pressure is not supplied to the wet multi-disc clutch mechanism, and the 2WD shift position switch is turned on. Become a position.

[0003] Also, when the 4WD lock position switch is manually turned on, the solenoid valve is turned off.
The shift valve operates to open the oil passage, and line pressure is supplied to the wet multi-disc clutch mechanism, setting it to the 4WD position.

0004

[Problems to be Solved by the Invention] However, in such a conventional 2WD-4WD switching control method, two
There is a problem in that when the vehicle suddenly enters a low-μ road while driving in WD, it is not possible to immediately switch to 4WD, which poses a danger. Furthermore, there is a problem in that tight corner braking occurs when a small corner is made at low speed while driving in 4WD.

The present invention has been made in view of these conventional problems, and is designed to avoid danger and prevent the occurrence of tight corner braking when suddenly entering a low μ road. It is an object of the present invention to provide a 2WD-4WD switching control method that can prevent this.

[0006]

[Means for Solving the Problems] In order to achieve the above object, the present invention always runs in two-wheel drive during normal driving,
When the rotational difference between the front wheels and the rear wheels exceeds a certain value, the system switches to four-wheel drive and maintains the four-wheel drive state for a certain period of time.

[0007]

[Operation] In the present invention, 2WD is always used during normal driving.
Since the vehicle travels at 4WD and switches to 4WD only when the rotational difference between the front and rear wheels exceeds a certain value, it is possible to prevent danger when the road surface changes when the vehicle suddenly enters a low-μ road. Since the vehicle always travels in 2WD, tight corner braking can be prevented even when making small corners at low speeds.

[0008] Also, once you switch to 4WD,
In order to prevent repetition of switching between 2WD and 4WD, 4WD is maintained for a certain period of time, so it is possible to prevent switching shock from occurring. In addition, always 4WD
It can also improve fuel efficiency.

[0009]

Embodiments Hereinafter, embodiments of the present invention will be explained based on the drawings. 1 to 4 are diagrams showing an embodiment of the present invention. First, to explain the transfer device, in FIG.
1 to 3 are casings, and these casings 1 to 3
A main drive shaft 4 to which driving force from the engine is transmitted and a main shaft 5 extending toward the propeller shaft are each rotatably supported by bearings.

A main drive gear 7 that meshes with a counter gear 6 is integrally formed on the main drive shaft 4, and the counter gear 6 further includes a low speed gear that is relatively rotatably mounted on the main shaft 5 via a needle bearing. 8, and the rotational force of the main drive shaft 4 is transmitted to the low speed gear 8 via the main drive gear 7 and the counter gear 6. 9 is a hub fitted to the main shaft 5 with a spline, and a coupling sleeve 10
are slidably engaged.

As shown, a coupling sleeve 10
When is in the neutral position, the main shaft 5 does not rotate because the rotational force of the main drive shaft 4 is not transmitted. On the other hand, when the coupling sleeve 10 is moved and engaged with the clutch gear 7a of the main drive gear 7, the rotational force of the main drive gear 7 is transmitted to the main shaft 5 via the coupling sleeve 10 and the hub 9.
The main shaft 5 rotates at high speed.

On the other hand, when the coupling sleeve 10 is moved and engaged with the clutch gear 8a of the low speed gear 8, the rotational force of the main drive gear 7 causes the counter gear 6, the low speed gear 8, the coupling sleeve 10 and the hub 9 to is transmitted to the main shaft 5 via the counter gear 6.
The main shaft 5 is rotated at a low speed with the reduction ratio set at .

Reference numeral 11 denotes a wet multi-disc clutch mechanism for performing 2WD-4WD switching and variable torque control. a hub 15 integrally formed with the drive sprocket 14; a plate 16 splined to the hub 15;
It is composed of a piston 17 that presses a piston 16.

A chain 19 is installed between the drive sprocket 14 and the driven sprocket 18, and a chain 19 is installed between the driven sprocket 18 and the front drive shaft 20.
is integrally formed. front drive shaft 20
are rotatably supported by the casings 1 and 2 via bearings 21 and 22. 23 is a first oil pump provided on the main shaft 5, and the first oil pump 23 is driven by the main shaft 5. The first oil pump 23 supplies piston operating pressure to the piston liquid chamber 24 and supplies lubricating oil to the oil passage 25 .

A second oil pump 26 is separately attached to the casing 2, and the second oil pump 26 is driven by a DC motor 27. As shown in the hydraulic circuit of FIG. As a result of the operation, each discharge pressure is supplied from the oil passages 30 and 31 to the regulator valve 34 and the shift valve 35 via the one-way valves 32 and 33. The regulator valve 34 adjusts each discharge pressure to the line pressure, and the shift valve 35 switches the line pressure.

When the solenoid valve 36 is on, the hydraulic pressure is drained, the shift valve 35 closes the oil passage 37, and line pressure is not supplied to the wet multi-disc clutch mechanism 11.
This will be the WD position. When the solenoid valve 36 is turned off, the shift valve 35 operates to supply line pressure to the wet multi-disc clutch mechanism 11 from the oil passage 37, resulting in the 4WD rigid position.

The solenoid valve 36 is controlled on and off by a CPU 38 consisting of a microcomputer.
As shown in FIG. 3, the CPU 38 includes a 2WD shift position switch 39 and a 4WD lock position switch 4.
0, each turn on from the low shift position switch 41,
The off signal, each rotation speed signal from the rear wheel rotation sensor 42, the front wheel rotation sensor 43, and the ABS operation signal are inputted. The CPU 38 controls the solenoid valve 36 and the DC motor 27 based on these signals.

Next, the control method will be explained. FIG. 1 is a flowchart showing the control method. In Figure 1, first,
In step S1, the above-mentioned signals are input as data, in step S2 it is determined whether the low shift position switch 41 is on, and in step S3 it is determined whether the 2WD shift position switch 39 is off.

When the low shift position switch 41 is off and the 2WD shift position switch 39 is on, the solenoid valve 36 is turned on in step S6 to set 2WD. When the low shift position switch 41 is on and the 2WD shift position switch 39 is off, it is determined in step S4 whether the ABS signal is on, and when the ABS signal is on, the solenoid valve 36 is turned on in step S6. When the ABS signal is off, the 4WD lock position switch 40 is turned off in step S5.
is on.

When the 4WD lock position switch 40 is on, the solenoid valve 36 is turned off in step S15 to select 4WD, and when the 4WD lock position switch 40 is off, the solenoid valve 36 is turned on in step S6 to select 2WD. do. Next, step S7
The rotation difference ΔN between the front wheels and the rear wheels is calculated in step S8, and it is determined in step S8 whether or not the rotation difference ΔN exceeds a certain value C (for example, 100 rpm).

[0021] When the rotational difference ΔN exceeds the constant value C, step S
When the ABS signal is off at step 9 and the 2WD shift position switch 39 is off at step S10, it is determined that there is a risk of slipping on a low μ road, and the time t is set at step S11.
, and in step S12, the time t becomes a constant time T(
For example, t
When ≧T, the constant value C is increased by 100 rpm in step S13.
m, and when T>t, the constant value C is set to 0 in step S14, the solenoid valve 36 is turned off in step S15 to set 4WD, and 4WD is maintained for a certain period of time T.

Note that when the rotational difference ΔN is less than the constant value C in step S8, when the ABS signal is on in step S9, or when the 2WD shift position switch 39 is on in step S10, the time t is changed in step S16. 0
Then, in step S17, the constant value C is set to 100 rpm, and the process returns. In this way, during normal driving, the vehicle always travels in 2WD, and only when entering a low μ road, switches to 4WD, so it is possible to prevent danger from occurring when the road surface suddenly changes.

Furthermore, once the vehicle is switched to 4WD, the 4WD state is maintained for a certain period of time, so it is possible to prevent repetition of switching from 2WD to 4WD, and the occurrence of a switching shock. In addition, since the vehicle always runs in 2WD, tight corner braking does not occur even when cornering at low speeds. Furthermore, since the vehicle always runs in 2WD, fuel efficiency can be improved.

[0024]

[Effects of the Invention] As explained above, according to the present invention, the driver always drives in 2WD and switches to 4WD only when suddenly entering a low μ road, etc., thereby reducing the risk of danger during sudden changes in the road surface. It is also possible to prevent the occurrence of tight corner braking.

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing one embodiment of the present invention.

FIG. 2 is a diagram showing a transfer device.

FIG. 3 is an explanatory diagram of CPU input/output.

FIG. 4 is a diagram showing a hydraulic circuit.

[Explanation of symbols]

1 to 3...Casing 4...Main drive shaft 5...Main shaft 6...Counter gear 7...Main drive gear 7a...Clutch gear 8...Low speed gear 8a...Clutch gear 9...Hub 10...Coupling sleeve 11...Wet type multi-plate clutch mechanism 12...Drums 13, 16...Plate 14...Drive sprocket 15...Hub 17...Piston 18...Driven sprocket 19...Chain 20...Front drive shaft 21, 22...Bearing 23...First oil pump 24...Piston liquid chamber 25...Oil passage 26...Second oil pump 27...DC motor 28...Oil reservoir 29...Oil strainer 30, 31...Oil passages 32, 33...One-way valve 34...Regulator valve 35...Shift valve 36...Solenoid valve 37...Oil passage 38...CPU 39...2WD shift position switch 40...4WD lock position switch 41...Low shift position switch 42...Rear wheel rotation sensor 43...Front wheel rotation sensor

Claims (1)

[Claims] Claim 1: During normal driving, the vehicle always runs in two-wheel drive, and when the rotation difference between the front wheels and rear wheels exceeds a certain value, it switches to four-wheel drive and maintains the four-wheel drive state for a certain period of time. Characteristic two-wheel drive-four-wheel drive control method.