JPH09193681A - Driving force controlling method in four wheel drive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve turning perforce of a vehicle by increasing a driving force to be distributed to a wheel on the higher wheel speed side according to the increase of a vehicle wheel speed difference and reducing a driving force to be distributed to a wheel on the lower wheel speed side in the area in which the vehicle wheel speed difference between a left wheel and a right wheel, to which a driving force is transmitted, is small. SOLUTION: In a four wheel drive V, signals from a speed sensor S1 detecting a rotational speed of a propeller shaft S, speed sensors S2 , S3 which detect rotational speeds of axles 13L, 13R of rear wheels WRL, WRR are inputted into a control unit U. In the area in which a wheel speed difference between the rear wheels WRL, WRR is small, a driving force to be distributed to a wheel on the higher wheel speed side is increased according to the increase of the wheel speed difference, while a driving force to be distributed to a wheel on the lower wheel speed side is reduced. In the area in which a wheel speed difference is large, a driving force to be distributed to a wheel on the higher wheel speed side is reduced according to the increase of the wheel speed difference, while a driving force to be distributed to a wheel on the lower wheel speed side is increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a four-wheel vehicle in which the engine driving force is directly transmitted to one of the front and rear wheels and the engine driving force is transmitted to the other front and rear wheels through a driving force varying means. The present invention relates to a driving force control method in a driving vehicle.

[0002]

2. Description of the Related Art A driving force control method in a four-wheel drive vehicle in which a part of driving force of front wheels driven by an engine is distributed to right and left rear wheels at a predetermined ratio has been conventionally known, and the present applicant has It has already been proposed by Japanese Patent Application No. 7-295762.

In the above-mentioned conventional vehicle, when the front wheels slip and the front wheel speed exceeds the rear wheel speed when the vehicle starts or suddenly accelerates, some of the driving force of the front wheels is distributed to the left and right rear wheels and the four wheels are used. It is designed to shift to the driving state. Further, when a speed difference occurs between the left and right rear wheels due to turning of the vehicle, the driving force distribution amount for the turning outer wheel is made larger than the driving force distribution amount for the turning inner wheel to improve the turning performance.

[0004]

By the way, when such a four-wheel drive vehicle travels on a road surface having a partially different friction coefficient, one of the left and right rear wheels may slip and a large left-right speed difference may occur. . In such a case, control is performed so that the wheel on the side of the road having a low friction coefficient slips greatly, so that the driving force of the slipped wheel increases and the driving force of the non-slip wheel decreases. So
It may not be possible to obtain the acceleration performance desired by the driver.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to prevent deterioration of acceleration performance when one of the left and right wheels in a four-wheel drive state slips.

[0006]

In order to achieve the above object, the present invention directly transmits the driving force of an engine to one of the front and rear wheels and drives the driving force of the engine to the other of the front and rear wheels. In a four-wheel drive vehicle that transmits via a force varying means, a wheel speed difference between the left and right wheels of the other wheel is detected, and in a region where the wheel speed difference is small, the side where the wheel speed is high in accordance with the increase of the wheel speed difference is detected. In the region where the wheel speed difference is large, the wheel speed is increased in accordance with the increase of the wheel speed difference while increasing the driving force distributed to the wheel It is characterized in that the driving force distributed to the wheel on the side is decreased and the driving force distributed to the wheel on the side where the wheel speed is low is increased.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described based on embodiments of the present invention shown in the accompanying drawings.

1 to 7 show a first embodiment of the present invention. FIG. 1 is a skeleton diagram of a power transmission device for a four-wheel drive vehicle, FIG. 2 is an overall view of a rear differential, and FIG. 3 is FIG. 2 is an enlarged view of part A of FIG. 4, FIG. 4 is an enlarged view of part B of FIG. 2, and FIG.
FIG. 6 is an enlarged view of part C of FIG.
FIG. 7 is a map for searching the rear wheel torque from the difference between the left and right speeds of the rear wheels.

As shown in FIG. 1, a four-wheel drive vehicle V has an engine E horizontally arranged at the front of a vehicle body, and an engine E of this type.
And a transmission M coupled to the right side surface of the.
The driving force of the transmission M is set to the left and right front wheels W _FL , W _FR
The power transmission system for transmitting to the transmission M is a first spur gear 2 provided on the output shaft 1 of the transmission M, a second spur gear 3 meshing with the first spur gear 2, and a bevel gear type front differential 4 driven by the second spur gear 3. And left and right axles 5 _L , 5 _R extending left and right from the front differential 4 and connected to the front wheels W _FL , W _FR .

The driving force of the power transmission system is applied to the rear wheels W _RL and W _RR.
The power transmission system for transmitting the power to the third spur gear 6 provided in the differential case of the front differential 4 and the fourth spur gear 7 meshed with the third spur gear 6.
A first bevel gear 8 that rotates integrally with the fourth spur gear 7, and a second bevel gear 9 that meshes with the first bevel gear 8.
A propeller shaft S having a second bevel gear 9 at the front end and extending rearward of the vehicle body; a third bevel gear 10 provided at the rear end of the propeller shaft S; a fourth bevel gear 11 meshing with the third bevel gear 10; Bevel gear 11 is provided with left and right rear wheels W _RL , W _RR axles 13 _L , 13 _R connected via a left hydraulic clutch C _L and a right hydraulic clutch C _R. The third bevel gear 10, the fourth bevel gear 11, and the left and right hydraulic clutches C _L , C _R constitute a rear differential 14. A hydraulic pump 15 is interposed in the middle portion of the propeller shaft S.
Left and right hydraulic clutches C _L , C _R
Engage.

The rear differential 14 has a first speed sensor S for detecting the number of revolutions of the propeller shaft S.
₁ and 2nd to detect the rotation speed of the axle 13 _L of the left rear wheel W _RL
A speed sensor S ₂ and a third speed sensor S ₃ for detecting the rotation speed of the axle 13 _R of the right rear wheel W _RR are provided.

Next, the structure of the rear differential 14 will be described in detail with reference to FIGS.

The rear differential 14 is provided with a front casing 21 and a rear casing 22 which are divided into front and rear parts. An input shaft 25 is supported by the front casing 21 via a pair of roller bearings 23, 24, and a flange 26 connected to the rear end of the propeller shaft S is spline-connected to the front end of the input shaft 25. The third bevel gear 10 is integrally formed at the rear end while being fixed by the nut 27.

Front casing 21 and rear casing 2
2 ball bearing 28_L, 28 _RRight and left through
Clutch hub 29_L, 29_RIs rotatably supported
Cage, both clutch hubs 29_L, 29_RLeft and right oil around the
Pressure clutch C_L, C_RCommon clutch outer 30
Be combined. At the left end of the clutch outer 30, the fourth
The bevel gear 11 is fixed with bolts 31 ... Therefore,
The rotation of the input shaft 25 depends on the third bevel gear 10 and the fourth bevel.
It is transmitted to the clutch outer 30 via the gear 11,
The clutch outer 30 of the clutch hub 29_L, 29_R
Rotate with.

The left output shaft 32 _L is rotatably supported on the inner circumference of the left clutch hub 29 _L , and the right output shaft 32 _R is rotatably supported on the inner circumference of the right clutch hub 29 _R. The clutch inners 33 _L and 33 _R are spline-coupled to the opposite ends of the output shafts 32 _L and 32 _R , respectively. A plurality of clutch plates 34 that are spline-fitted to the inner periphery of the clutch outer 30 and a plurality of clutch discs 35 that are spline-fitted to the outer periphery of the clutch inners 33 _L and 33 _R are alternately arranged so as to be in close contact with each other. Will be placed.

Front casing 21 and rear casing 2
Cylinder member 36 provided in 2_L, 36_RFormed into
Cylinder 36₁, 36₁Inside the annular piston 37_L,
37 _RAre slidably fitted. Left and right piston 37_L,
37_RClutch plate 3 located at the end of the pressing force of
Left and right pistons 37 to transmit to_L, 37_R
Between the clutch plates 34 and 34 and the thrust plate.
A ring 38_L, 38_R, Pressure plate 39_L,
39_RAnd pressing member 40_L, 40_RIs provided. Pressing
Member 40_L, 40_RIs the pressure plate 39_L, 39
_LLegs 40 abutting on the₁Are equipped with these
Leg 40₁… Is the clutch hub 29_L, 29 _RFormed into
Opening 29₁Play with.

Thus, the oil chambers 41 _L and 41 _R formed between the cylinders 36 ₁ and 36 ₁ and the pistons 37 _L and 37 _R are formed.
When hydraulic pressure is supplied to the pistons, the pressing force of the pistons 37 _L and 37 _R is transmitted via the thrust bearings 38 _L and 38 _R , the pressure plates 39 _L and 39 _R and the pressing members 40 _L and 40 _R , and the clutch plates 34 ... The clutch discs 35 ... Are brought into close contact with each other. As a result, the rotation of the clutch outer 30 causes the clutch inners 33 _L and 33 _{R to} rotate.
Is independently transmitted to the left and right output shafts 32 _L and 32 _R via. Left and right output shafts 32 _L, the flange 42 is formed integrally with the 32 _{R L,} 42 _R to the left and right rear wheels W _RL, W _RR axles 13 _L, 13 _R are coupled.

The first speed sensor S is attached to the mounting portion 21 ₁ provided on the front casing 21 of the rear differential 14.
₁ is attached with bolts 43. First speed sensor S ₁
Are opposed to dogs 26 _1, ... Protruding on the flange 26 of the input shaft 25, and detect the rotation speed of the propeller shaft S connected to the input shaft 25, that is, the average value of the left and right front wheel speeds.

Rear case 14 of the rear differential 14
Mounting portion 22 provided on the ring 22₁, 22₁To the second speed
Sensor S_TwoAnd the third speed sensor S_ThreeBolts 44,44
Installed with. Second speed sensor S_TwoAnd the third speed
Sensor S_ThreeIs the left and right output shaft 32 _L, 32_RFlange 42
_L, 42_RDog 42 protruding from₁Is facing ... and left
Right rear wheel W_RL, W_RRAxle 13_L, 13_RNumber of revolutions immediately
The left and right rear wheel speeds are detected respectively.

Returning to FIG. 1, the first to third speed sensors S
The signals from _{1 to} S ₃ are input to the electronic control unit U,
The electronic control unit U hydraulic clutch of the left and right on the basis of the signal C _L, and controls the engagement state of the C _R. Wire harnesses (not shown) connected to the first to third speed sensors S _{1 to} S ₃ are put together and connected to the electronic control unit U.

Next, the operation of the embodiment of the present invention having the above-mentioned structure will be described with reference to the flowchart of FIG.

[0022] First, reads the output of the first to third speed sensors S ₁ to S ₃ in step S1, a front wheel speed W _P calculated from the output of the first speed sensor S ₁ in step S2, the second
The rear wheel speed W _P ′ calculated from the outputs of the speed sensor S ₂ and the third speed sensor S ₃ is compared. The rear wheel speed W
_P ′ is calculated as an average value of the left rear wheel speed W _L calculated from the output of the second speed sensor S ₂ and the right rear wheel speed W _R calculated from the output of the third speed sensor S ₃ {W _P ′ ＝
(W _L + W _R ) / 2}.

In step S2, the front wheel speed W _P is changed to the rear wheel speed W
If not exceed _P ', the left and right hydraulic clutch C _L, C
_R is held in the disengaged state, and the vehicle enters the front-wheel drive state. On the other hand, the front wheels W _FL, if it W _FR is slipping front wheel speed W _P exceeds the rear wheel speed W _P 'in step S2, the left and right hydraulic clutch C _L, engagement C _R is a predetermined engaging force Then, the vehicle becomes a four-wheel drive state. When the vehicle V turns, the radius of the trajectory of the front wheels W _FL , W _FR exceeds the radius of the trajectory of the rear wheels W _RL , W _RR , so that the front wheel speed W _P becomes larger than the rear wheel speed W _P ′. Due to the speed difference, the left and right hydraulic clutches C _L and C _R are engaged with each other with a predetermined engaging force, and the vehicle enters the four-wheel drive state.

In these cases, the left and right hydraulic clutches C _L ,
In order to determine the engagement force of C _R , the speed difference between the left rear wheel speed W _L and the right rear wheel speed W _R is calculated in step S3, and
In step S4, a slip wheel is determined from the magnitude relationship between the left rear wheel speed W _L and the right rear wheel speed W _R. In the following step S5, the magnitudes of the left rear wheel torque T _L transmitted to the left rear wheel W _RL and the right rear wheel torque T _R transmitted to the right rear wheel W _RR by the engagement of the left and right hydraulic clutches C _L , C _R. Is searched based on the map of FIG. 7, and the electronic control unit U outputs a signal for controlling the engaging force of the left and right hydraulic clutches C _L and C _R so that the torque distribution ratio is obtained in step S6.

Thus, when the vehicle V starts or suddenly accelerates,
The left and right front wheels W to which the torque of the gin E is directly transmitted_FL, W_FR
Slips, the slip amount increases (ie
Wheel speed difference ΔW_PIncrease of the rear wheel W_RL, W_RRTotoru
Is allocated, which improves starting performance and acceleration performance.
It is planned. At this time, the left rear wheel speed W_LAnd the right rear wheel speed W _R
If they are equal, the left rear wheel torque T_LAnd right rear wheel torque T_R
Is equal to.

When the vehicle turns, the left and right rear wheels W _RL ,
The left rear wheel torque in accordance with the speed difference W _RR T _L and the right rear wheel W _RR
Is controlled.

This will be specifically described with reference to FIG.
When the vehicle is in a normal turning state, the speed difference between the left rear wheel speed W _L and the right rear wheel speed W _R is within a predetermined range regulated by the minimum turning radius of the vehicle, and the speed difference is extremely large. It never grows. For example, when the vehicle enters a left turn state, with decreasing turning radius, i.e. the torque T _R of a turning outer wheel right rear wheel W _RR with increasing lateral speed difference is increased, a turning inner left The torque T _L of the rear wheel W _RL is set to decrease, and when the left-right speed difference further increases, the torque T _R of the right rear wheel W _RR and the torque T _L of the left rear wheel W _RL are T
It is held at a constant value while maintaining _R > T _L. In this way, the turning performance of the vehicle can be improved by setting the torque of the outer turning wheel to be larger than the torque of the inner turning wheel.

When the vehicle enters the right turn state,
The turning performance of the vehicle can be improved by making the torque T _L of the left rear wheel W _RL which is the turning outer wheel larger than the torque T _R of the right rear wheel W _RR which is the turning inner wheel. In both the left turn and the right turn, the torque on the propeller shaft, which is the sum of the left rear wheel torque T _L and the right rear wheel torque T _R , is maintained at a constant value.

When a vehicle runs on a road surface or a bad road where the friction coefficient is partially different and one of the left and right rear wheels W _RL and W _RR slips, the left-right speed difference is much larger than that during normal turning. Occurs. In such a case, if the above-described torque distribution during turning is executed as it is, the rear wheels W _RL and W _RR whose speed has increased due to slip will be mistakenly recognized as the turning outer wheel, and the torque of the rear wheels W _RL and W _RR will be lost. Is increased and the torque of the rear wheels W _RL and W _RR on the side having a grip force without slippage is increased, and the acceleration performance intended by the driver may not be obtained.

Therefore, in the case of one-wheel slip, in which an extremely large left / right speed difference is generated as compared with a normal turning, the torque of the rear wheels W _RL , W _RR on the higher speed side is decreased in accordance with the increase in the left / right speed difference, By increasing the torque of the rear wheels W _RL , W _RR on the low speed side, the so-called LSD (Limited Slip Differential) function is exerted, and the rear wheels W _RL , W _RR on the side where no slip occurs As a result, more torque can be distributed to prevent deterioration of the acceleration performance of the vehicle.

Next, a second embodiment of the present invention will be described with reference to FIG.

The second embodiment is different from the first embodiment in the torque distribution of the rear wheels W _RL and W _RR when one wheel enters the slip state. That is, when one of the wheels enters the slip state, the torque of the rear wheels W _RL , W _RR on the high speed side is decreased and the torque of the rear wheels W _RL , W _RR on the low speed side is increased in the first embodiment. Therefore, the left rear wheel torque T _L and the right rear wheel torque T
There is a case where the magnitude relationship between _R is reversed, but the rear wheels W _RL rate larger side in the second embodiment, the torque of the W _RR, rear wheel speed is smaller side W _RL, with respect to the torque of W _RR By always keeping it large or equal, it is considered not to make the driver feel uncomfortable.

Although the embodiments of the present invention have been described in detail above, the present invention can be modified in various ways without departing from the scope of the invention.

For example, in the embodiment, the torque of the engine E is
Front wheel W_FL, W_FRDirectly to the rear wheel W_RL, W_RRTo hydraulic
Latch C_L, C_RAlthough it is transmitted via the
Engine E torque to rear wheel W_RL, W_RRDirectly transmitted to the front wheels
W_FL, W_FRHydraulic clutch C _L, C_RCommunicate through
It can also be applied to vehicles. Variable driving force
The means is a hydraulic clutch C_L, C_RIt is not limited to
Other means such as a switch may be used.

[0035]

As described above, according to the present invention, in a region where the wheel speed difference between the left and right wheels of the wheel, to which the driving force of the engine is transmitted via the driving force varying means, is small, the increase in the wheel speed difference is dealt with. By increasing the driving force distributed to the wheel with the higher wheel speed and decreasing the driving force distributed to the wheel with the lower wheel speed, more driving force is distributed to the outer turning wheel during normal turning. Thus, the turning performance of the vehicle can be improved. In the area where the wheel speed difference is large,
When the one wheel slips, the driving force distributed to the wheel on the higher wheel speed side is decreased and the driving force distributed to the wheel on the lower wheel speed side is increased according to the increase in the wheel speed difference. More driving force can be distributed to the wheels on the non-slip side to ensure the acceleration performance of the vehicle.

[Brief description of the drawings]

FIG. 1 is a skeleton diagram of a power transmission device for a four-wheel drive vehicle.

[Fig.2] Overall view of rear differential

FIG. 3 is an enlarged view of part A of FIG.

FIG. 4 is an enlarged view of a portion B in FIG. 2;

FIG. 5 is an enlarged view of a portion C in FIG. 2;

FIG. 6 is a flowchart illustrating an operation.

FIG. 7 is a map for searching the rear wheel torque based on the left / right speed difference between the rear wheels.

FIG. 8 is a map for searching the rear wheel torque from the left-right speed difference between the rear wheels according to the second embodiment.

[Explanation of symbols]

_CL Left hydraulic clutch (driving force varying means) _CR Right hydraulic clutch (driving force varying means) W _FL Left front wheel (one wheel) W _FR Right front wheel (one wheel) W _RL Left rear wheel (other wheel) W _RR Right rear wheel (other wheel) S ₁ 1st speed sensor S ₂ 2nd speed sensor S ₃ 3rd speed sensor U Electronic control unit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazunori Kobayashi 1-4-1 Chuo, Wako-shi, Saitama Inside Honda R & D Co., Ltd. (72) Inventor Masayuki Hikita 1-4-1 Chuo, Wako-shi, Saitama Stock Company Honda Technical Research Institute

Claims (1)

[Claims] 1. The driving force of the engine (E) is directly transmitted to one of the front and rear wheels (W _FL , W _FR ) and the other of the front and rear wheels (W _RL , W _RR ) of the engine (E). driving force driving force variation means (C _L, C _R) in the four-wheel drive vehicle for transmitting through said other wheel (W _RL, W _RR) by detecting wheel speed difference between left and right, differential wheel speed In a small region, the driving force distributed to the wheel with the higher wheel speed is increased and the driving force distributed to the wheel with the lower wheel speed is decreased according to the increase in the wheel speed difference. In a region where the wheel speed is large, the driving force distributed to the wheel with the higher wheel speed is decreased and the driving force distributed to the wheel with the lower wheel speed is increased according to the increase in the wheel speed difference. A driving force control method for a four-wheel drive vehicle.