JPS6189125A - Drive coupling device for four-wheel drive - Google Patents

Abstract

PURPOSE:To make a drive coupling device for four-wheel drive, miniature and lightweight, by controlling the discharged pressure of a hydraulic pump which is adapted to be driven due to the difference in rotational speed between the front wheel drive shaft and the rear wheel drive shaft, such that the drive mode is changed over between four and two wheel drive modes, and the drive power for the front and rear drive shafts are well-distributed. CONSTITUTION:A rotary shaft 11 in a differential gear unit 10 for front wheels 9 is coupled with a rotary shaft 14 in a differential gear unit 17 for rear wheels 16. This hydraulic pump 13 is driven due to the difference in speed between both rotary shafts 11, 14 and therefore, discharges oil in an amount in accordance with the speed difference. Further, the rotary shaft 14 for the rear wheel side is coupled to the output shaft 3 of an engine 1 through gears 4, 5. Further, the discharge pressure of the hydraulic pump 13 is controlled to change over the mode of drive between four and two wheel drive modes, and as well the drive power is controlled to be well-distributed to the front and rear wheels.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a four-wheel drive drive coupling device that distributes and transmits engine power transmitted to rear wheels to front wheels via a hydraulic pump.

<Prior art> In a four-wheel drive vehicle in which the front and rear wheels are driven by the same engine, there is a slight difference in the effective radius of the front and rear tires, and in the case of turning, the rolling path of the tires is slightly different. Due to the difference, the tires slip and unreasonable force is applied to the drive system, so it is necessary to provide a means to prevent this.

For this reason, conventionally, a first rotating shaft that transmits driving force to the front wheels and a second rotating shaft that transmits driving force to the rear wheels are used to transmit driving force even if there is a difference in rotational speed between the front wheels and the rear wheels. For full-time 4-wheel drive vehicles that are connected with a third differential device called a center differential, or when there is a problem with 4-wheel drive such as tight corner braking caused by cornering without a center differential installed, the driver There are part-time four-wheel drive vehicles that drive either the front wheels or the rear wheels by operating the vehicle.

<Problems to be Solved by the Invention> Since the above-mentioned full-time four-wheel drive vehicle is equipped with a center differential, it is disadvantageous compared to a part-time four-wheel drive vehicle in terms of weight, size, and cost. However, because differential rotation is possible, it may not be possible to achieve four-wheel drive when four-wheel drive is required, and there are drawbacks such as requiring a differential lock mechanism and further complicating the device. Ta.

On the other hand, part-time 4-wheel drive vehicles have 4-wheel drive and 2-wheel drive vehicles.
The driver must perform an operation to switch between wheel drive and wheel drive each time, which has the drawback of complicating driving operations.

It is an object of the present invention to eliminate the drawbacks that occur in conventional four-wheel drive vehicles and to provide a small and lightweight four-wheel drive drive coupling device.

Means for Solving Problems〉 The four-wheel drive drive coupling device according to the present invention connects a first rotating shaft that transmits driving force to the front wheels and a second rotating shaft that transmits driving force to the rear wheels. The first rotating shaft and the second rotating shaft are driven by a difference in rotational speed and are connected via a hydraulic pump that discharges an amount of oil according to the difference in rotational speed, while the rear wheels are directly driven by engine power. The invention is characterized in that an output shaft for engine power is connected to the second rotating shaft.

Function: By controlling the oil discharge pressure from the hydraulic pump, conventional part-time 4-wheel drive vehicles that required driver operation can now automatically switch between 4-wheel drive and 2-wheel drive. As the switching is performed, a four-wheel drive state is obtained in which driving force is distributed from the rear wheels to the front wheels in accordance with the difference in rotational speed between the front wheels and the rear wheels. Further, since the vehicle is made smaller and more compact by eliminating the need for a center differential, it is possible to make the vehicle smaller and more compact than a full-time four-wheel drive vehicle, and also to reduce weight and cost. Furthermore, the driving force for the rear wheels is distributed to the front wheels via a hydraulic pump, making the M! l! During sudden acceleration, the driving force distribution is greater on the rear wheels than on the front wheels, where I-force is limited by the torque capacity of the oil pump, and the vehicle weight distribution is greater on the rear wheels than on the front wheels. It is possible to obtain excellent acceleration performance when turning by hand, and excellent steering performance when turning with driving force applied to the wheels.

Embodiment Hereinafter, an embodiment of a four-wheel drive drive coupling device according to the present invention will be described based on the drawings. In this embodiment, the present invention is applied to a type of vehicle in which the engine is disposed at the front of the vehicle, as shown in FIG. 1 showing a schematic configuration.

A transmission@2 is connected to an engine 1 placed vertically, and driving force is taken out from a drive gear 4 attached to its output shaft 3 and transmitted to a second rotating shaft 14 via a driven gear 5. The signal is transmitted from the second rotating shaft 14 to the differential device 17 for the rear wheels 16, and the rear wheels 16 are driven by the engine 1 via the series of power trains described above. On the other hand, the driving force transmitted to the second rotating shaft 14 is transmitted to the first rotating shaft 11 via the four-wheel drive drive coupling device 13, and this driving force is transmitted to the differential gear for the front wheels 9. 10 and connects the front wheels 9 to the rear wheels 16 via the drive coupling device 13.
indirectly driven by the driving force of

This four-wheel drive drive coupling device 13 has a vane pump 20, which is a hydraulic pump, as shown in FIG.
The rotor 20a of the vane pump 20 is connected to the second rotating shaft 14 through which the driving force to the rear wheels 16 is directly transmitted, and the cam ring 20b drives the front wheels 9. It is connected to the first rotating shaft 11 that transmits force. The vane pump 20 as a hydraulic pump discharges an amount of oil proportional to its rotation speed, and there is a relative rotation between the rotor 20a and the cam ring 20b, that is, between the first rotation shaft 11 and the second rotation shaft 14. When relative rotation occurs, it functions as a hydraulic pump and generates hydraulic pressure, and by blocking the discharge port of the vane pump 20 (corresponding to the suction and discharge port at the tip in the direction of relative rotation), the static pressure is removed through oil. Rotor 20a and cam ring 20 due to pressure
b becomes like a rigid body and rotates together. Therefore, two pump chambers are formed at diagonal positions in the cam ring 20b, and four suction/discharge ports 22, 2 are formed, which serve as suction ports when located on the base end side in the rotational direction, and serve as discharge ports when located on the distal end side.
3, 24, and 25 are formed at approximately diagonal positions, and the suction and discharge ports 22 and 24 and the suction and discharge ports 23 and 25, which are located diagonally and have the same function, respectively, keep oil on the stationary side even when the cam ring 20b is rotating. The first oil $
26 and the second oil passage 27 are in communication. Also, a check valve 28,
An oil reservoir 30 is communicated with the oil reservoir 30 through the oil reservoir 29, and there are two opposing check valves 31 that allow only flow from the oil reservoir 30 and allow only flow out between the first oil passage 26 and the second oil passage 27. The oil passages 26 and 27 communicate with each other via the angle 32, and an intermediate portion between the two check valves 31' and 32 communicates with a relief valve 33. A communication path 35 between the oil reservoir 30 and the intermediate portions up to the two check valves 28 and 29 is provided at the intermediate portion of the relief valve 33 on the spring 34 side.
A piston 36 is provided to control the opening pressure of the U IJ-F valve 33, and the other end of the piston 36 is configured to act on a control hydraulic pressure that is duty-controlled. A solenoid valve 38 controls the constant pressure oil pressure supplied through the orifice 37 for duty control, and this solenoid valve 38 is electrically connected to a computer 39, and the engine rotation speed input to the computer is controlled by a solenoid valve 38.
The hydraulic pressure acting on the other end of the piston 36 is controlled by the rotation speed of the first rotation shaft 11, the rotation speed of the second rotation shaft 14, the throttle opening, the brake inch, and the steering angle. Note that the constant pressure oil pressure supplied through the orifice 37 is applied to the transmission 2.
In the case of an automatic transmission, the control hydraulic pressure may be used, and in the case of a manual transmission, this hydraulic pressure is secured by installing an oil pump or the like.

With such a hydraulic circuit 21, the discharge pressure always acts on the valve body of the relief valve 33 regardless of the relative rotational direction between the rotor 20a and the cam ring 20b, and the oil reservoir 30 communicates with the suction port.

The driving state of such a four-wheel drive drive coupling device will first be described in the case where the opening pressure of the relief valve 33 is kept constant only by the setting force of the spring 34.

In normal straight-ahead driving conditions, the effective radii of the tires of the front wheels 9 and rear wheels 16 are the same, and the slip rotational speed of the tires is small. There is no difference in rotational speed between them. Therefore, the vane pump 20 does not generate oil pressure, and no driving force is transmitted to the front wheels 9, resulting in two-wheel drive using only the rear wheels 16.

However, even when driving straight, the rear wheels 16 usually slip within about 1% even if there is no large slip like during acceleration, so the difference in rotational speed due to this occurs between the first rotating shaft 11 and the second rotating shaft 14. When this occurs, the vane pump 20 functions to generate oil pressure corresponding to this rotational speed difference, and the rotor 20a
and the cam ring 20b rotate together, and a driving force corresponding to this oil pressure and the pressure-receiving area of the vane is transmitted to the front wheels 9, resulting in a four-wheel drive state. Vane pump 2 in this case
As shown in FIG. 3 ta+, the flow of oil at 0 is caused by the relative rotation of the rotor 20a, and the suction and discharge ports 23 and 25 serve as suction ports, and oil is drawn from the oil reservoir 30 via the check valve 29. is sucked in, while the suction and discharge ports 22.
24 serves as a discharge port, and at the same time as the check valves 28 and 32 are closed, the air is guided to the relief valve 33 via the check valve 31. In the figure, solid line arrows indicate the flow of discharged oil, and broken line arrows indicate the flow of suction oil.

Next, when the rotational speed of the rear wheels 16 becomes very large compared to the rotational speed of the front wheels 9, for example, when the rear wheels on a snowy road slip, or when the front wheels tend to lock up during sudden acceleration or braking, , the difference in rotational speed between the first rotating shaft 11 and the second rotating shaft 14 of the four-wheel drive drive coupling device 13 becomes very large, and the vane pump 20 pumps the oil in the state shown in FIG. The flow generates a large hydraulic pressure, but when it exceeds a predetermined value, the relief valve 33 opens against the spring 34 and the discharge pressure is controlled to be almost constant, providing the front wheels 9 with a constant drive corresponding to the constant discharge pressure. It becomes a four-wheel drive state where power is transmitted. As a result, the rotational speed of the rear wheels 16 decreases and the rotational speed of the front wheels 9 increases, reducing the rotational speed difference (same function as a non-slip differential). In addition, when the front wheels 9 tend to lock, the brake torque of the rear wheels 16 is increased to prevent the front wheels 9 from locking.

Here, unlike the present invention, when the vehicle is based on a so-called front drive vehicle, which is a vehicle in which the front wheels are directly driven by the engine and the power is distributed and transmitted to the rear wheels via a hydraulic pump, it is particularly suitable for rallying, etc. The following problems occur in 4-wheel drive vehicles for competition. In other words, during sudden acceleration, load transfer occurs and the vehicle weight distribution becomes larger on the rear wheels than on the front wheels, and the amount of torque transmitted to the rear wheels is limited by the torque capacity of the hydraulic pump, so the engine torque During large sudden accelerations, the front wheels have a greater drive load than the rear wheels, causing the front wheels to slip and making it impossible to utilize engine power effectively. Furthermore, if the torque capacity of the hydraulic pump is increased to solve this problem, the hydraulic pump becomes large and disadvantageous in terms of weight and cost.

However, the present invention is based on a so-called rear-drive vehicle, which is a vehicle that directly drives the rear wheels with an engine and distributes this rear-wheel drive to the front wheels via a hydraulic pump, so there is no problem described above. Not only that, during sudden acceleration, a relatively large amount of driving force is applied to the rear wheels, where the weight distribution of the vehicle is large, so engine power is effectively utilized. Further, since only the engine torque exceeding the grip limit of the rear wheels, where slipping occurs, is transmitted to the front wheels by the hydraulic pump, the torque capacity of the hydraulic pump can be small. Figure 4 shows the practical results of the above effects. That is, similar to this embodiment, the so-called F engine is arranged in the front of the vehicle and directly drives the rear wheels.
In comparing a 4-wheel drive vehicle based on an R vehicle and a 4-wheel drive vehicle based on a so-called front-wheel drive vehicle, in which the engine is placed at the front of the vehicle and directly drives the front wheels, it is compared to a 4-wheel drive vehicle based on an FR vehicle. There is a difference as shown between the rear wheel grip limit when the maximum traction force is generated when the car is fully focused, and the front wheel grip limit when the maximum traction force is generated in first gear based on an FF car. The hydraulic pump capacity of the base model is smaller than that of the FF vehicle base model.

On the other hand, when the rotational speed of the front wheels 90 becomes very large compared to the rotational speed of the rear wheels 16, for example, when the rear wheels 16 are slightly locked in the braking state, the four-wheel drive drive coupling device 1
A very large rotational speed difference occurs between the first rotating shaft 11 and the second rotating shaft 14 of No. 3 in the opposite direction to that described above, and in the vane pump 20, oil flows as shown in FIG.
The suction and discharge ports 22 and 24 serve as suction ports, and the check valve 28
While oil is sucked in from the oil reservoir 30 through the oil reservoir 30, the suction/discharge port 23.25 becomes a discharge port, passes through the second oil passage 27, closes the check valve 29.31, and is guided from the check valve 32 to the relief valve 33, causing a large Hydraulic pressure is applied, but this oil pressure is also held constant by the relief valve 33, and a constant driving force is transmitted to the front wheels 9, resulting in a four-wheel drive state. As a result, the brake torque to the front wheels 9 is increased to prevent the rear wheels 16 from locking.

Also, at 11 o'clock in normal turning, the front wheel 90 rotation speed is slightly thicker than the rear wheel 16 rotation speed.
A four-wheel drive state is established in which brake torque is applied to the front part 6 and a slight driving torque is applied to the front part 9, and cornering is performed.

When turning with driving force applied to the wheels, four-wheel drive vehicles based on front drive vehicles, especially four-wheel drive vehicles for competitions such as rallies, have the following problems. arise. In other words, in a vehicle based on a front drive vehicle, due to the limited torque capacity of the hydraulic pump, the front wheels have a wider distribution of driving force than the rear wheels (as shown in Figure 5). In this case, a large portion of the tire grip force T of the front wheels, which are the steered wheels, is consumed as driving force, and the cornering force, C, which counters the centering force during turning, becomes small, resulting in a decrease in the grip strength of the steered wheels, resulting in a decrease in steering performance. It gets worse.

However, since the present invention is based on a rear-drive vehicle, it does not have the above-mentioned problems, and not only can it perform good high-speed turns by applying a large driving force to the wheels, but also has a so-called spin coon, which is an effective means for competitive driving. In other words, it is possible to make a sharp turn using the front wheels as a fulcrum while intentionally applying excessive engine torque to cause the rear wheels to spin and slip.

In this way, by controlling the discharge pressure of the four-wheel drive drive coupling device 13 using the relief valve 33 so that it does not exceed a certain value, when a four-wheel drive state is required in a conventional part-time four-wheel drive vehicle, Things that required operation by the driver,
Switching between four-wheel drive and two-wheel drive is automatically performed, and a four-wheel drive state is obtained with a driving force corresponding to the rotational speed difference between the front wheels and the rear wheels.

In addition, it can be made smaller and more compact than the center differential that is always installed in full-time four-wheel drive vehicles, and it also reduces weight and costs.

Next, when adjusting the opening pressure of the relief valve 33 by applying the hydraulic pressure acting on the lower end side of the piston 36 to the duty press, the discharge pressure of the vane pump 20 can be adjusted and controlled, and the driving force to the front wheels 9 can be adjusted. can be adjusted.

Therefore, as the load on the engine 1 increases, if this is detected by the throttle opening signal and the discharge pressure of the vane pump 20 is controlled to increase, the amount of driving force transmitted to the front wheels 9 in the four-wheel drive state can be increased. It can be made to run with ease.

In addition, the operation state of the foot brake is detected by the brake switch, and when the foot brake is turned on, the discharge pressure of the vane pump 20 is increased to prevent the front wheels 9 and the rear wheels 16 from locking, thereby controlling the distance. It is possible to shorten the time and obtain a stable braking condition.

Furthermore, by detecting the steering angle and controlling the discharge pressure so that the larger the steering angle becomes, the lower the discharge pressure becomes, it becomes possible to avoid corner braking phenomena and smoothly turn the vehicle. Further, the discharge pressure of the vane pump 20 can be adjusted and controlled according to the engine rotational speed and vehicle speed using each detection signal inputted to the computer to maintain a stable running condition.

In the above embodiment, a vane pump is used as the hydraulic pump of the four-wheel drive drive coupling device 13, and there are four suction and discharge ports.
Although the explanation has been made using a balanced type vane pump with two suction and discharge ports depending on the amount of driving force transmitted, it is also possible to use an unbalanced vane pump with two suction and discharge ports, and other types of hydraulic pumps such as internal gear pumps and trochoid pumps can also be used. pump.

Hypocycloid pumps, ahonyal pumps, radial plunger pumps, and the like can also be used, as long as the amount of oil discharged changes according to the difference in rotational speed. Furthermore, the engine is not limited to the front part of the vehicle; if the vehicle is based on a rear-drive vehicle, the engine may be located anywhere, such as in the center of the vehicle or at the rear of the vehicle. Furthermore, the variable logger may be either manual or automatic, and control of the relief valve is not limited to duty control using hydraulic pressure, but may be mechanically controlled.

The graph shown in FIG. 6 shows a comparison between the transmission torque of the hydraulic pump used in the present invention and the transmission torque of a known variable viscosity clutch. This variable viscosity clutch is manufactured by Harry Ferguson in the UK, and transmits torque between two shafts using silicone oil whose viscosity changes depending on temperature. When this variable viscosity clutch and a hydraulic pump are compared using ones that are approximately the same size, the hydraulic pump provides a four-wheel drive state with a lower differential rotational speed, as shown in the figure.

<Effects of the Invention> According to the present invention, a front drive car is used as a pace,
A hydraulic pump that drives a first rotary shaft that transmits driving force to the front wheels and a second rotary shaft that transmits the driving force to the rear wheels according to the rotational speed difference between them, and discharges an amount of oil according to the rotational speed difference. Since the static hydraulic pressure is used to transmit the driving force and obtain a four-wheel drive state, it eliminates problems such as corner braking phenomena and sloppy driving operations of 4-wheel drive vehicles. In addition to this, it can be made smaller and lighter than the center differential conventionally equipped on full-time four-wheel drive vehicles, and the structure is simple and inexpensive.

Furthermore, because the driving force for the rear wheels is distributed to the front wheels via the hydraulic pump, the driving force for the rear wheels is stronger than for the front wheels, where the driving force is limited by the torque capacity of the hydraulic pump. The drive force distribution is large, and the vehicle weight distribution is greater in the rear wheels than in the front wheels, making it possible to obtain excellent acceleration performance during sudden acceleration, as well as when turning with drive force applied to the wheels. It is possible to obtain outstanding dry rudder performance.

[Brief explanation of drawings]

FIGS. 1 to 3 show an embodiment of the four-wheel drive drive coupling device of the present invention, in which FIG. 1 is a schematic configuration diagram, FIG. 2 is a detailed sectional view, and FIG. An explanatory diagram of oil flow. Figure 4 is a graph comparing the traction forces of FR-based and FF-based vehicles. Figure 5 is an explanatory diagram showing the relationship between front tire grip force, driving force, and cornering force. The figure is a graph comparing the transmission torque between a hydraulic pump and a variable viscosity clutch.In the figure, 1 is the engine, 2 is the transmission, 3 is the output shaft, 9 is the front wheel, 11 is the first rotating shaft, 13 is the A drive coupling device for four-wheel drive, 14 is a second rotating shaft, 16 is a rear wheel, and 20 is a vane pump.

Claims (1)

[Claims] A first rotating shaft that transmits driving force to the front wheels and a second rotating shaft that transmits driving force to the rear wheels are driven by the rotational speed difference between the first rotating shaft and the second rotating shaft, and While connected via a hydraulic pump that discharges the appropriate amount of oil,
A drive coupling device for four-wheel drive, characterized in that an output shaft of the engine power is connected to the second rotation shaft so that the rear wheels are directly driven by the engine power.