JPS61275028A - Driving force distribution controller for four-wheel drive vehicle - Google Patents

Abstract

PURPOSE:To improve the drivability of a car in the case where each effective diameter of both front and rear tires differs, by installing a function which controls each driving force distribution ratio of front and rear wheels on the basis of a revolving speed difference between these front and rear wheels. CONSTITUTION:One side revolving speed N1 of front wheels or rear wheels and the other revolving speed N2 are detected by both first and second revolving speed detecting devices 11 and 12. A compensation factor A making a speed difference DELTAN (DELTAN=N1-A.N2) is calculated by a subtracting device 13 from the revolving speed A.N2 compensated by a compensating device 17 and the other side revolving speed N2. Therefore, in case of setting tires different in specifications as well as when tire air pressure drops or when chains are set to two wheels on the one side, etc., a slip is accurately detected. And, driving force distribution is controlled via a desired value setting device 14 and a driving force distributing device 15, thus car drivability is improved.

Description

Detailed Description of the Invention (Industrial Application Field) This invention relates to a driving force distribution control device for a four-wheel drive vehicle, and particularly relates to a driving force distribution ratio between the power transmitted to the front wheels and the power transmitted to the rear wheels. This is applied to a power distribution control system that controls the power distribution based on the difference in rotational speed between the front and rear wheels.

(Prior Art) As a conventional driving force distribution control device for a four-wheel drive vehicle, there is known, for example, the one described in Japanese Unexamined Patent Publication No. 57'-2052'33. This driving force distribution control device for a four-wheel drive vehicle engages the clutch when the difference in rotational speed between the front wheels and the rear wheels is equal to or greater than a predetermined value, and applies four-wheel drive for a predetermined period of time. The clutch is protected by storing the number of times the clutch is switched, and when the number of times the clutch is switched exceeds a predetermined number, the clutch is continued to be engaged.

(Problem to be solved by this invention) However,
In such conventional driving force distribution control devices for four-wheel drive vehicles, the rotational speed difference between the front wheels and the rear wheels is detected as slip (relative rotation with respect to the road surface), and based on this detected rotational speed difference, Since the system is configured to perform switching control between two-wheel drive and four-wheel drive depending on the magnitude of slip, the difference in rotational speed between the front and rear wheels will also change when tires with different specifications are installed on the vehicle. There is a problem in that switching control between two-wheel drive and four-wheel drive cannot be performed accurately in response to slip. For example, if tempered tires are installed, if chains are installed on only one of the front and rear wheels, if the tire air pressure decreases or fluctuates, the effective diameter of the front and rear tires may change due to an imbalance in the front and rear weight distribution of the vehicle, etc. The problem is that it is not possible to accurately detect slip simply from the difference in rotational speed between the front and rear wheels, as the difference in rotational speed between the front and rear wheels also changes when the wheels are different or when the trajectories of the front and rear tires are different due to turning. There was a point.

(Means for solving the problem) A driving force distribution control device for a four-wheel drive vehicle according to the present invention includes:
This was made with the aim of solving the above-mentioned problem, and as shown in FIG.
, a second rotational speed detection means 12 that detects the rotational speed N2 of the other front wheel or rear wheel, a coasting detection means 16 that detects that the vehicle is in a straight coasting state, and a second rotational speed detection means a correction means 17 that calculates a rotation speed correction value A - N by multiplying the rotation speed Nt of the other wheel detected by the first rotation speed detection means 11 by a correction coefficient A; and a rotation speed of one wheel detected by the first rotation speed detection means 11; Subtraction means 13 that calculates the rotation speed difference ΔN between the front and rear wheels from N1 and the rotation speed correction value A - NZ calculated by the correction means 17, and subtraction when the coasting detection means 16 detects that the vehicle is in a straight coasting state. Means 13
a correction value determining means 18 that determines the correction coefficient A of the correcting means 17 so that the rotation speed difference ΔN calculated by target value determining means 14 for determining;
driving force distribution means for changing the driving force transmitted from the engine to at least one of the front wheels or the rear wheels so that the driving force distribution ratio between the front wheels and the rear wheels becomes the target driving force distribution ratio determined by the target value determining means 14; 15.

(Function) According to the driving force distribution control device for a four-wheel drive vehicle according to the present invention, when the vehicle is in a straight coasting state, the correction coefficient A is determined to make the rotational speed difference ΔN between the front and rear wheels zero, and the other Correct the rotational speed N2 of the wheels, and calculate the rotational speed difference ΔN between the front and rear wheels from the corrected rotational speed A - NZ and the rotational speed N of one wheel (ΔN = N + A-N z ).
Calculate. Therefore, for example, even if tires with different specifications are installed, the tire air pressure decreases, or tires are installed on one of the front and rear wheels, the difference in rotational speed ΔN between the front and rear wheels, that is, slippage, will be reduced. Accurate detection becomes possible, and switching control between two-wheel drive and four-wheel drive can be performed accurately in response to slippage, thereby improving the driving performance of the vehicle.

(Example) Embodiments of the present invention will be described below based on the drawings.

2 to 5 are diagrams showing an embodiment of a driving force distribution control device for a four-wheel drive vehicle according to the present invention. This embodiment is based on a front-engine, rear-wheel drive vehicle.
Shows what is applied to wheel drive vehicles.

First, to explain the outline with reference to Figure 2, 21 is an engine (engine), 22 is a transmission (transmission) assembled integrally with the engine 21, and the output shaft of the transmission 22 changes the driving force distribution between the front and rear wheels. It is connected to a rear wheel propeller shaft 24R and a front wheel propeller shaft 24F via a possible transfer (driving force distribution means) 23. The rear wheel propeller shaft 24R is connected to the rear wheel differential device 25R and the left and right axles 26RL, 26R.
Connected to the left and right rear wheels 27RL and 27RR via R,
Similarly, the front wheel propeller shaft 24F is connected to left and right front wheels 27FL and 27FR via a front wheel differential 25F and left and right axles 26FL and 26FR.

As shown in FIG. 3, in the transfer 23, an input shaft 30 connected to the output shaft of the transmission 22 is rotatably housed in a transfer case 28 formed by joining two members 28a and 28b with bolts 29. Also,
Rear export force shaft 31 connected to rear wheel propeller shaft 24R
is rotatably supported by a bearing 32. The input shaft 30 and the rear export force shaft 31 are each coaxially spline-coupled to a substantially pipe-shaped joint member 33 and connected to rotate integrally through the joint member 33. The coupling member 33 is provided with a drum 44 of a hydraulic multi-disc clutch 49 to be described later on its outer periphery, and is rotatably inserted into a cylindrical bearing holder 34 fixed to the transfer case 28 with bolts 34a. ing.

A first hollow shaft 38 is rotatably inserted into the input shaft 30 on the left side of the figure, and a second hollow shaft 39 spline-coupled with the first hollow shaft 38 is attached on the right side of the figure via a needle bearing 43. Rotatably extrapolated. The first hollow shaft 38 has a drive gear 3 meshed with a counter gear 40a on its outer periphery.
8a is integrally formed.

This counter gear 40a is integrally formed with a counter shaft 40 rotatably supported by the transfer case 28 via a bearing 41, and is integrally formed with the front wheel propeller shaft 2.
Driven gear 4 installed on the front export force shaft connected to 4F
It meshes with 2. The second hollow shaft 39 has a hub 39a that is integrally formed and projects radially outward.
A friction multi-disc clutch 49 is provided between the drum 44 and the drum 44 described above.
is installed.

The friction multi-disc clutch 49 includes a plurality of drive plates 45 spline-coupled to the inner peripheral wall of the drum 44, and a plurality of drive plates spline-coupled to the hub 39a of the second hollow shaft 39 and arranged alternately in the axial direction with the drive plates 45. A substantially annular piston 48 whose inner and outer surfaces are in liquid-tight and axially slidable contact with the plate 46 and the drum 44 and the joint member 33 to define an oil chamber 47, and which is attached to the joint member 33. A spring 53 is compressed between the retainer 52 and the piston 48 and urges the piston 48 toward the oil chamber 47. The oil chamber 47 is connected to the transfer case 28 via a first oil passage 35a formed in the joint member 33, a second oil passage 35b formed in the bearing holder 34, and a third oil passage 35c formed in the transfer case 28↓. (hydraulic bow) 35d.

In this friction multi-disc clutch 49, when high-pressure oil is supplied from the hydraulic port 35d to the oil chamber 47 via the first, second, and third oil passages 35a, 35b, and 35C, the piston 48 is moved by the elasticity of the spring 53. It moves to the left in the figure against the force to bring the drive plate 45 and the driven plate 46 into frictional contact, thereby connecting between the joint member 33 and the second hollow shaft 39, that is, between the input shaft 30 and the front export force shaft. .

Note that 30a is a first lubricating oil passage formed in the input shaft 30;
31a is a second lubricating oil passage formed in the rear export force shaft 31;
9b is a first clutch lubricating oil passage formed in the second hollow shaft 39, 39c is a second clutch lubricating oil passage formed in the hub 39a of the second hollow shaft 39, and 44a is a third clutch lubricating oil passage formed in the drum 44. The first and second lubricating oil passages 30a and 31a supply lubricating oil to the needle bearing 43, etc., and the first, second and third clutch lubricating oil passages 39b, 39c and 44a supply lubricating oil to the needle bearing 43, etc. Lubricating oil is supplied to the sliding contact portion between the drive plate 45 and the driven plate 46 of the multi-plate clutch 49. Further, 36 is a binion for speed detection.

50 is a pressure oil source that generates high pressure oil;
is connected to the aforementioned hydraulic boat 35d via a solenoid valve 54. The solenoid valve 54 has a solenoid 54a connected to the control device 51, and connects the hydraulic port 35d and the pressure oil source 50 with an opening degree according to the current value energized to the solenoid 54a and the hydraulic pressure of 35d. communicate between. That is, the solenoid valve 54 has a spool that responds to, for example, the electromagnetic force of the solenoid 54a and the oil pressure of the hydraulic boat 35d, and the movement of this spool changes the oil pressure (clutch pressure) supplied to the oil chamber 47.

The control device 51 includes a one-chip microcomputer, etc., and includes a front wheel rotation speed detector (second rotation speed detector) 55, a rear wheel rotation speed detector (first rotation speed detector) 56, and a steering angle detector 57. , a neutral switch 58, and a brake switch 59 are connected. Front wheel rotation speed detector 55
detects the rotation speed of the front export force shaft of the transfer 23 and outputs a signal indicating the rotation speed Nf of the front wheels 27FL and 27FR. Detects the rotation speed etc. of the rear wheel 27R.
A signal indicating the rotational speed Nr of L, 27RR is output. The steering angle detector 57 detects the steering angle θ and outputs a signal indicating the steering angle θ, and the neutral switch 58 detects whether the transmission 22 is operated to a neutral position and outputs a signal indicating the steering angle θ. When the brake switch 59 is in the neutral position, it outputs a logic signal T, and the brake switch 59 detects whether or not the brake pedal is depressed and is in operation, and outputs a logic signal B when the brake is operated.

The control device 51 performs arithmetic processing on input signals and controls the solenoid valve 54.
The solenoid 54a is energized. This control device 51 is
It corresponds to a subtraction means, a target value determination means, a coasting detection means, a correction means, and a correction value determination means, and also includes a steering angle detector 57,
Neutral switch 58 and brake switch 59
corresponds to coasting detection means.

Next, the effect will be explained.

This driving force distribution control device for a four-wheel drive vehicle calculates a correction coefficient A that makes the rotational speed difference ΔN between the front and rear wheels zero when the vehicle is coasting in a straight line, and adjusts the rotational speed N of the front and rear wheels to be detected.
The rotation speed difference ΔN between the front and rear wheels is determined by correcting f − and N r using the correction coefficient A, and the driving force distribution R between the front and rear wheels is controlled based on this rotation speed difference ΔN, that is, the slip. Therefore, even when tires with different specifications are installed, slip can be accurately detected and driving force distribution R can be controlled, and the driving performance of the vehicle can be improved.

The process will be explained in detail below with reference to the flowchart shown in FIG. A series of processes shown in this flowchart are repeatedly executed in the control device 51 at predetermined intervals. First, in step P1, an initial value of 1 is set for the correction coefficient A, and in subsequent steps P2 and P3, the front wheel rotation speed N [and the rear wheel rotation speed Read the wheel rotation speed Nr.

In the following step P4, the rotational speed difference ΔN between the front and rear wheels is calculated using the following equation (1).

ΔN=N r -A -N f -...-A
In the next step P, the output signal of the neutral switch 58 is used to determine the transmission 22.
If the transmission 22 is in the neutral position, proceed to step P6; if the transmission 22 is not in the neutral position, proceed to step P6. Proceed to pH.

In step P6, it is determined from the output signal of the brake switch 59 whether or not the brake is being applied. If the brake is being applied, the process proceeds to step P'll; if the brake is not being applied, the process proceeds to step P7. In step P7, it is determined from the output signal of the steering angle detector 57 whether the steering angle θ is zero, that is, whether the vehicle is in a straight-ahead state. If the vehicle is not in a straight-ahead state, the process proceeds to step P, where the vehicle If the vehicle is traveling straight, the process advances to step P8. These step P2, step P.

In step P, it is determined whether the vehicle is in a straight coasting state. In step Pa, the rotational speed difference ΔN calculated in step P4 is regarded as zero, and the next step P
In , a temporary correction coefficient A0 is calculated using the following equation (2) when the rotational speed difference ΔN is regarded as zero.

Note that addition of 1 in the denominator and numerator of formula (2) is
This is to prevent the denominator from becoming zero.

Then, in the following step P1°, the correction coefficient A is replaced with the value A0. Therefore, even if, for example, the tire air pressure changes late, it is possible to accurately calculate the rotational speed difference ΔN.

At the step pH, the rotational speed difference ΔN is a predetermined value ΔN
It is determined whether or not it is smaller than 0. If the rotational speed difference ΔN is smaller than a predetermined value ΔN0, the process proceeds to step P1°, and if the rotational speed difference ΔN is greater than or equal to the predetermined value ΔNo, the process proceeds to step PI3. In step PI2, a current value i according to the rotational speed difference ΔN is calculated based on the following formula (3), and similarly, in step P1
In step 3, a current value i according to the rotational speed difference ΔN is calculated based on the following equation (4).

i=a・ΔN・・・・
...(3) i=a・ΔN0+b・ (ΔN−ΔN,)・
(4) In these steps P1□ and PI3, as shown in FIG.
The current value to be energized, that is, the driving force distribution ratio between the front and rear wheels is determined according to the rotational speed difference ΔN. And the next step P
In step 14, the current i determined in steps P, z, and P1 is applied to the solenoid 54a of the electromagnetic valve 54. Therefore, the electromagnetic valve 54 communicates the oil chamber 47 of the friction multi-disc clutch 49 with the pressure oil source 50 at an opening degree that corresponds to the current i, and the clutch pressure P becomes a value that corresponds to the current i. As a result, the driving force transmitted to the front wheels 27FL and 27FR via the friction multi-plate clutch 7ch 49 has a value corresponding to the clutch pressure P, that is, the current i, and the driving force distribution ratio between the front and rear wheels corresponds to the rotational speed difference ΔN. controlled by

As described above, according to this driving force distribution control device for a four-wheel drive vehicle, a correction coefficient is calculated that makes the rotational speed difference ΔN between the front and rear wheels zero when the vehicle is in a straight coasting state, and from then on, this correction coefficient is Since the driving force distribution ratio between the front and rear wheels is controlled based on the rotational speed difference ΔN determined by By controlling the driving force distribution ratio based on this accurate rotational speed difference, driving performance can be improved.

The above-mentioned embodiments are applied to a part-time 4-wheel drive vehicle equipped with a transfer having a hydraulic multi-disc clutch, but it is also applicable to a part-time 4-wheel drive vehicle equipped with a transfer having a dog clutch. It goes without saying that the present invention can also be applied to drive vehicles or full-time four-wheel drive vehicles equipped with a central differential with a differential limiting device.

(Effects of the Invention) As described above, according to the driving force distribution control device for a four-wheel drive vehicle according to the present invention, when the vehicle enters a straight coasting state, a correction coefficient is newly calculated, and correction is made using this correction coefficient. The driving force distribution ratio between the front and rear wheels is controlled based on the rotational speed difference ΔN between the front and rear wheels. Therefore, if tires with different specifications are installed, or chains are installed on one of the front and rear wheels,
Even if the tire air pressure drops or fluctuates, the effective diameter of the front and rear tires differs due to an imbalance in the front and rear weight distribution of the vehicle, or the trajectory of the front and rear tires differs due to turning, it is possible to accurately calculate the rotational speed difference ΔN. This makes it possible to accurately control the driving force distribution ratio in response to slip, thereby improving the driving performance of the vehicle.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a driving force distribution control device for a four-wheel drive vehicle according to the present invention. 2 to 5 show an embodiment of the driving force distribution control device for a four-wheel drive vehicle according to the present invention, in which FIG. 2 is an overall schematic diagram, FIG. 3 is a sectional view of the main parts of the mechanism, and The figure is a flowchart, and Figure 5 is the difference in rotational speed of front and rear wheels ΔN
FIG. 3 is a diagram showing the characteristics of the current value i applied to the electromagnetic valve. 11.56...First rotation speed detection means (rear wheel rotation speed detector), 12.55...Second rotation speed detection means (front wheel rotation speed detector), 13... ...subtraction means, . 14...Target value determining means, 15...Driving force distribution means, 16...Coasting detection means, 17...Correction means, 1B... ...Correction value determining means, 21...Engine, 27F L, 27F R...Front wheel, 27RL
, 27RR... Rear wheel, 49... Friction multi-disc clutch, 51... Control device, 57... Rudder angle detector, 58... ...neutral switch, 59...
...Play Kiss Inch.

Claims (1)

[Claims] The first one detects the rotational speed of one of the front wheels or the rear wheels.
a rotational speed detection means, a second rotational speed detection means for detecting the rotational speed of the other of the front wheels or the rear wheels, and a rotational speed detected by the first rotational speed detection means and the second rotational speed detection means. a subtraction means for calculating a rotational speed difference between the front and rear wheels based on the rotational speed of the wheels; a target value determination means for determining a target driving force distribution ratio according to the rotational speed difference calculated by the subtraction means; driving force distribution means for changing the driving force transmitted from the engine to at least one of the front wheels or the rear wheels so that the driving force distribution ratio to the wheels becomes the target driving force distribution ratio determined by the target value determining means; A driving force distribution control device for a four-wheel drive vehicle, comprising: coasting detection means for detecting that the vehicle is in a straight coasting state; and correction to the rotational speed of the other wheel detected by the second rotational speed detection means. a correction means for calculating a rotational speed correction value by multiplying by a coefficient, and a rotational speed difference calculated by the subtraction means such that when it is detected by the coasting detection means that the vehicle is in a straight coasting state, the rotational speed difference calculated by the subtraction means becomes zero. A driving force distribution control device for a four-wheel drive vehicle, comprising: correction value determining means for determining a correction coefficient of the correction means.