JP2004203287A - Vehicle differential rotation control device - Google Patents

Abstract

An object of the present invention is to make it possible to efficiently control the rotational speed ratio of right and left wheels over a wide range and with a simple configuration.
A left and right output shafts (10L, 10R) of a differential device (2) are connected to pump shafts of left and right hydraulic pumps (3L, 3R), respectively, and further connected to left and right axles (11L, 11R) via the pump shafts. . The discharge port of the left hydraulic pump 3L communicates with the suction port of the right hydraulic pump 3R via the hydraulic passage 15, and the discharge port of the right hydraulic pump 3R and the suction port of the left hydraulic pump 3L are hydraulically connected. It communicates via a passage 16. Then, the controller 50 sets the target rotational speed ratio of the left and right wheels during traveling, and varies the pump displacement so that the left and right hydraulic pumps 3L and 3R operate as pumps and motors so as to achieve the target rotational speed ratio. , And efficiently controls the rotational speed ratio of the left and right wheels over a wide range.
[Selection diagram] Fig. 1

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a differential rotation control device for a vehicle that can arbitrarily control a rotation speed ratio between left and right wheels.
[0002]
[Prior art]
BACKGROUND ART Conventionally, various types of devices for distributing torque to left and right wheels of a vehicle have been devised and put into practical use. A typical example is to provide a coupling between the left and right wheels that can variably control the transmission torque capacity, and to control the coupling to adjust the torque movement and the amount of torque movement. Multi-plate clutches are widely used.
[0003]
Such devices are disclosed in, for example, Japanese Patent No. 2641724 and Japanese Patent No. 2826580. In the devices disclosed in these patent documents, a mechanical type that transmits power from a power source to left and right wheels is used. A gear pair for forcibly making the left and right shafts differential is installed separately from the differential device, and the amount of torque transfer between the left and right wheels by the gear pair is adjusted by a hydraulic multi-plate clutch.
[0004]
[Patent Document 1]
Japanese Patent No. 2641724 [0005]
[Patent Document 2]
Japanese Patent No. 2,826,580
[Problems to be solved by the invention]
However, in the devices disclosed in Patent Literature 1 and Patent Literature 2, the controllable upper limit of the rotational speed ratio of the left and right wheels is determined by the gear ratio of the gear pair, and the controllable width is limited by the mechanical configuration. Will be done. Furthermore, in order to operate the hydraulic multi-plate clutch, a hydraulic circuit including a hydraulic pump and various pressure regulating valves and various hydraulic control valves is required to supply the operating hydraulic pressure, which complicates the structure and reduces energy loss. There is a problem that this causes an increase.
[0007]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a differential rotation control device for a vehicle capable of efficiently controlling the rotation speed ratio of right and left wheels over a wide range with a simple configuration. .
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides two hydraulic pumps which are respectively connected to left and right axles, and at least one of which is a variable displacement pump, communicates a discharge port and a suction port of each of the two hydraulic pumps. The two hydraulic passages forming a closed circuit and the pump displacement of the variable displacement pump are varied to operate the two hydraulic pumps reversibly with a pump and a motor. Means for controlling the rotation speed ratio.
[0009]
The two hydraulic pumps can be connected between the left and right output shafts of the differential device for distributing power from the power source and the left and right axles, respectively, to control the rotational speed ratio of the drive wheels, and By connecting the left and right driven wheels to the respective axles, the rotational speed ratio of the driven wheels can be controlled.
[0010]
When applied to the drive wheels, by connecting to the left and right output shafts of the differential device via a transmission mechanism, the piping length of the hydraulic passage is reduced, and the pump efficiency and reliability are further improved. be able to.
[0011]
The two hydraulic passages are desirably connected to the reserve tank via relief passages provided with valves that open outside the set pressure range, thereby preventing cavitation in the hydraulic passages and protecting the device. can do.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 to 5 relate to a first embodiment of the present invention, FIG. 1 is an explanatory diagram showing a configuration of a differential rotation control device applied to driving wheels, and FIG. 2 is an explanatory diagram of a variable displacement hydraulic pump. 3 is a characteristic diagram showing the relationship between the left and right wheel rotational speed ratio and the displacement of the left and right pumps, FIG. 4 is an explanatory diagram showing the configuration of a differential rotation control device with a shortened hydraulic passage, and FIG. 5 is applied to driven wheels. It is an explanatory view showing a configuration of a differential rotation control device.
[0013]
The differential rotation control device according to the present invention controls the rotational speed ratio between the left and right wheels by using two hydraulic pumps (motors) that perform a pump and a motor operation reversibly with at least one being a variable displacement type. Can be arbitrarily distributed, and FIG. 1 shows an example in which the present invention is applied to driving wheels. In the figure, reference numeral 1 denotes a power transmission shaft for transmitting a driving force transmitted from an engine (not shown) via a transmission, and a differential device 2 is connected to the power transmission shaft 1. And a differential rotation control device 4 mainly including the hydraulic pumps 3L and 3R.
[0014]
The differential device 2 has a well-known mechanical configuration, and a crown gear 7 fixedly provided outside a rotatable differential case 6 meshes with a drive pinion gear 5 coupled to a rear end of the power transmission shaft 1. The side gears 9, 9 are engaged with the pinion gears 8, 8, which are supported by the differential case 6 and rotate integrally. The left and right output shafts 10 </ b> L, 10 </ b> R are fixedly attached to the side gears 9, 9, and extend left and right through the differential case 6.
[0015]
The left and right output shafts 10L and 10R of the differential device 2 are connected to the pump shafts of the left and right hydraulic pumps 3L and 3R, respectively, and further connected to the left and right axles 11L and 11R via the pump shafts. Left and right drive wheels 12L, 12R are fixedly mounted on the shaft ends of the left and right axles 11L, 11R.
[0016]
The left and right hydraulic pumps 3L and 3R include, for example, vane pumps and piston pumps, and at least one of them is a variable displacement pump, and the discharge port and the suction port of each other are connected by a hydraulic passage forming a closed circuit. That is, the discharge port of the left hydraulic pump 3L communicates with the suction port of the right hydraulic pump 3R via the hydraulic passage 15, and the discharge port of the right hydraulic pump 3R and the suction port of the left hydraulic pump 3L communicate with each other. They are communicated via a passage 16.
[0017]
FIG. 2 shows a configuration example of the hydraulic pumps 3L and 3R. In FIG. 2, both of them are variable displacement hydraulic pumps using a vane pump in which a rotor 21 having a vane 20 rotates in a circular cam ring 22. . In this variable displacement hydraulic pump, the amount of eccentricity of a cam ring 22 with respect to the center of rotation of a rotor 21 serving as a pump shaft is varied by an actuator 23. For example, the rotation of an actuator 23 such as a motor is supported by a fulcrum 22a of the cam ring 22. Is converted into a swinging operation centering on the displacement of the pump, the displacement (discharge volume) of the pump can be varied.
[0018]
The actuators 23 of the left and right hydraulic pumps 3L, 3R are connected to a controller 50 mainly composed of a microcomputer or the like, and are driven and controlled by a signal from the controller 50. Various parameters representing the vehicle driving state such as the steering angle of the steering wheel, the front and rear wheel speeds, the accelerator opening, the engine speed, the longitudinal acceleration, and the lateral acceleration are input to the controller 50. A control target value (target rotation speed ratio) for the rotation speed ratio of the left and right wheels during traveling is set based on any one or a plurality of the parameters, and the actuators 23, 23 are controlled so as to achieve the target rotation speed ratio. Variably controls the displacement of the pump via
[0019]
That is, while the vehicle is traveling, the hydraulic pumps 3L and 3R rotate at the same speed as the wheels (the drive wheels 12L and 12R or the driven wheels 12'L and 12'R). Assuming that VL is the displacement of the left wheel and NL is the rotation speed of the left wheel, the discharge flow rate QL of the hydraulic pump 3L is expressed by the following equation (1). Similarly, assuming that the displacement volume per rotation of the right hydraulic pump 3R is VR and the rotation speed of the right wheel is NR, the discharge flow rate QR of the hydraulic pump 3R is expressed by the following equation (2).
QL = VL × NL (1)
QR = VR × NR (2)
[0020]
Here, since the left hydraulic pump 3L and the right hydraulic pump 3R are configured such that their respective discharge ports and suction ports are connected by closed-circuit hydraulic passages 15 and 16, the left and right hydraulic pumps 3L and 3L are connected to each other. The relationship (QL = QR) that the discharge flow rates of the 3Rs are the same holds, and the following formula (3) holds from the above formulas (1) and (2).
VL × NL = VR × NR (3)
[0021]
Then, when the equation (3) is modified with respect to the rotational speed ratio NR / NL of the left and right wheels, the following equation (3 ′) is obtained. As shown in FIG. A characteristic in which the left and right wheel rotational speed ratio NR / NL changes linearly can be obtained.
VL / VR = NR / NL (3 ′)
[0022]
Therefore, when the displacement of one of the left and right hydraulic pumps is increased by a predetermined ratio, the opposite hydraulic pump acts as a motor, and the rotational speed of the opposite wheel can be increased at the same ratio. That is, by variably controlling the displacement of the pump, one axle 11L or 11R can be decelerated, while the other axle 11R or 11L can be increased in speed and relatively rotated via the differential device 2 to achieve power transmission. The driving force transmitted from the shaft 1 and distributed to the left and right by the differential device 2 can be arbitrarily redistributed to the left and right axles 11L and 11R in accordance with the rate of the acceleration / deceleration.
[0023]
As described above, one of the left and right hydraulic pumps 3L and 3R may be a variable displacement hydraulic pump and the other may be a fixed displacement hydraulic pump. Is variable in terms of control width and control adaptability, and it is desirable that both the left and right hydraulic pumps 3L and 3R be variable displacement hydraulic pumps.
[0024]
In the above-described differential rotation control device 4, a series of simple controls are used to control the vehicle from running on a slippery road surface to running with normal torque distribution via the differential device 2, and to control the understeer and oversteer to follow the steering angle. It is possible to run with a turning radius that is reduced.
[0025]
For example, if the vehicle is to be started while the right drive wheel is on ice, the right drive wheel will slip with only the normal differential device 2 and the vehicle cannot easily move forward. In such a case, the differential rotation control device 4 according to the present invention is added, and the controller 50 controls the left and right hydraulic pumps 3L and 3R so that the displacements thereof become equal, thereby forcibly equalizing the rotation speeds of the left and right wheels. (NL = NR; see equation (3) above), and the differential lock state can be easily achieved.
[0026]
In this differential lock state, if even the right driving wheel is likely to slip even slightly, the pressure in the hydraulic passage 16 connecting the discharge port of the right hydraulic pump 3R and the suction port of the left hydraulic pump 3L increases, At the same time as applying a brake to the rotation of the right drive wheel by the pump action of the hydraulic pump 3R, the left hydraulic pump 3L acts as a motor to generate a torque to increase the rotation of the left drive wheel. By this action, the right drive wheel can be prevented from slipping and the torque can be reliably transmitted to the left drive wheel, so that a smooth start and stable running can be achieved.
[0027]
Further, for example, when the front wheels slip and the front wheels inflate to the outside of the curve during the left turn, and understeer is likely to occur, the left and right hydraulic pumps 3L, 3R are adjusted to the target turning radius. Is controlled so as to maintain the displacement volume ratio VL / VR. In this control state, when understeer is likely to occur, the rotation speed of the left wheel tends to increase, so the pressure in the hydraulic passage 15 connecting the discharge port of the left hydraulic pump 3L and the suction port of the right hydraulic pump 3R is increased. And a counterclockwise yaw moment that suppresses understeer is generated between the left and right rear wheels. By this action, understeer can be suppressed, and stable running can be ensured.
[0028]
As described above, by controlling the displacement of the pump using a variable displacement hydraulic pump, the rotation speed can be controlled to an arbitrary rotation speed ratio. In addition, when the actual rotation speed ratio deviates from the target rotation speed ratio, the target rotation speed ratio can be controlled. The hydraulic torque automatically acts in the direction approaching the rotation speed ratio. In other words, in the technology in which torque is controlled as in a conventional device using a hydraulic clutch and a gear pair, feedback control for increasing or decreasing the torque is necessary in order to set the rotation speeds of the left and right wheels to the target rotation speed. In the differential rotation control device 4 according to the present invention, feedback control is not required, and a wide control range and stable traveling control can be realized with an extremely simple configuration.
[0029]
In addition, between the two hydraulic pumps, the differential rotational energy flows from the pump whose rotation is to be reduced to the pump whose rotation is to be increased, so that the external energy is transferred as in a conventional device using a hydraulic clutch and a gear pair. Energy loss is smaller and efficiency can be improved as compared with what is needed.
[0030]
In this case, the left and right hydraulic pumps 3L, 3R are not arranged in series between the output shafts 10L, 10R of the differential device 2 and the axles 11L, 11R, and as shown in FIG. The gears may be arranged in parallel with the differential device 2 via a transmission mechanism such as a gear train 13L, 13R fixed to the 10R or a chain. That is, by combining the two hydraulic pumps 3L and 3R in one place, the piping length of the hydraulic passages 15 and 16 can be shortened, so that the pump efficiency and reliability can be further improved. , 3R can be expected to further improve the reliability and maintainability of the apparatus.
[0031]
FIG. 1 shows an example in which the differential rotation control device 4 is applied to the driving wheels. However, when the differential rotation control device 4 is applied to the driven wheels, the differential device 2 becomes unnecessary as shown in FIG. The pump shafts of the hydraulic pumps 3L, 3R are connected to the axles 11'L, 11'R of 'L, 12'R. Also in this case, similarly, the shortening of the piping length of the hydraulic passages 15 and 16 and the independent modularization of the hydraulic pumps 3L and 3R become easy, and it is expected that the pump efficiency, reliability, and maintainability are further improved. it can.
[0032]
Next, a second embodiment of the present invention will be described. FIG. 6 is an explanatory diagram showing a protection circuit of the differential rotation control device according to the second embodiment of the present invention.
[0033]
When the displacements of the variable displacement hydraulic pumps 3L and 3R are suddenly changed, the pressure in the oil passage rapidly rises / falls, and cavitation may occur. Therefore, in the second embodiment, a protection circuit against a sudden change in pressure in the oil passage is added.
[0034]
That is, as shown in FIG. 6, a hydraulic passage 15 communicating the discharge port of the left hydraulic pump 3L and the suction port of the right hydraulic pump 3R is provided via two relief passages 15a and 15b provided in parallel. A pressure regulator valve 31 which is connected to the reserve tank 30 and opens when the pressure in the hydraulic passage 15 exceeds a predetermined set pressure is interposed in one of the relief passages 15a, and in the other relief passage 15b, A charge valve 32 that opens when the pressure in the hydraulic passage 15 drops below a predetermined set pressure is provided.
[0035]
The same applies to the hydraulic passage 16 that communicates the discharge port of the right hydraulic pump 3R and the suction port of the left hydraulic pump 3L. A pressure regulator valve 31 that is connected to the reserve tank 30 and opens when the pressure in the hydraulic passage 16 exceeds a predetermined set pressure is interposed in one of the relief passages 16a, and in the other relief passage 16b. A charge valve 32 that opens when the pressure in the hydraulic passage 16 falls below a predetermined set pressure is provided.
[0036]
That is, parallel relief passages 15a and 15b, in which pressure regulator valves 31 and charge valves 32 are interposed, are provided in two oil passages, that is, hydraulic passages 15 and 16 connecting the left and right hydraulic pumps 3L and 3R, respectively. A protection circuit is formed by adding parallel relief passages 16a and 16b interposed with the charge valve 32 and connecting to the reserve tank 30, and the displacement of the pump is suddenly changed so that one oil passage becomes high pressure and the other oil passage becomes high pressure. When the oil pressure of the oil passage becomes negative, the pressure regulator valve 31 opens to release the pressure to the reserve tank 30 when the pressure exceeds the set pressure on the high pressure side, and the charge valve 32 decreases when the pressure becomes lower than the set pressure on the negative pressure side. Opens to supply hydraulic oil from the reserve tank 30 side.
[0037]
As a result, even when the displacement of the pump is suddenly changed, the pressure in the hydraulic passages 15 and 16 can be maintained within an appropriate range to prevent cavitation and protect the system. Not only that, an excessive differential torque due to a sudden change in pressure can be limited, and the stability of the system can be improved. Further, the pressure in the hydraulic passages 15 and 16 can be maintained within an appropriate range even when the volume of the working oil changes due to a temperature change, and the operation reliability can be improved even when the environmental conditions change. Can be.
[0038]
【The invention's effect】
As described above, according to the present invention, it is possible to control the rotational speed ratio of the left and right wheels over a wide range and efficiently with a simple configuration, and to improve the reliability of the device.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a configuration of a differential rotation control device applied to a drive wheel according to a first embodiment of the present invention; FIG. 2 is an explanatory diagram of a variable displacement hydraulic pump; FIG. FIG. 4 is a characteristic diagram showing the relationship between the left and right wheel rotational speed ratios and the displacement ratio of the left and right pumps. FIG. 4 is an explanatory diagram showing the configuration of a differential rotation control device in which a hydraulic passage is shortened. FIG. 6 is an explanatory diagram showing a configuration of a differential rotation control device applied to a driving wheel. FIG. 6 is an explanatory diagram showing a protection circuit of the differential rotation control device according to the second embodiment of the present invention.
2 Differential devices 3L, 3R Hydraulic pump 4 Differential rotation control devices 11L, 11R Axles 15, 16 Hydraulic passages 15a, 15b, 16a, 16b Relief passage 30 Reserve tank 50 Controller

Claims (5)

Two hydraulic pumps respectively connected to the left and right axles, at least one of which is a variable displacement pump;
Two hydraulic passages that form a closed circuit by communicating the discharge port and the suction port of the two hydraulic pumps with each other;
Means for varying the pump displacement of the variable displacement pump to reversibly operate the two hydraulic pumps and the motor and to control the rotational speed ratio of the left and right axles to an arbitrary rotational speed ratio. A differential rotation control device for a vehicle, comprising: 2. The differential rotation control of a vehicle according to claim 1, wherein the two hydraulic pumps are respectively connected between left and right output shafts of a differential device for distributing power from a power source and the left and right axles. apparatus. 2. The vehicle differential according to claim 1, wherein the two hydraulic pumps are respectively connected via a transmission mechanism to left and right output shafts of a differential device for distributing power from a power source to the left and right axles. Rotation control device. 2. The differential rotation control device for a vehicle according to claim 1, wherein the two hydraulic pumps are connected to respective axles of left and right driven wheels. 5. The fuel tank according to claim 1, wherein the two hydraulic passages are respectively connected to a reserve tank via a relief passage provided with a valve that opens outside a set pressure range. The differential rotation control device for a vehicle according to any one of the preceding claims.

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