JPH0436888B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a drive coupling device when front wheels and rear wheels are driven by the same engine.

In four-wheel drive vehicles where 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 the front wheels have a larger turning radius than the rear wheels when turning. As a result, torsional torque is generated between the front and rear drive shafts as they try to rotate faster, resulting in the same state as braking, resulting in the so-called tight corner braking phenomenon, resulting in poor running performance and tire wear. Therefore, a means to prevent this is necessary.

For this reason, in conventional four-wheel drive vehicles, the front and rear wheels are connected at the drive connection part using a dog clutch, etc., and when cornering, even though the rotational speeds of the front and rear wheels are different, Since the wheels rotate at a constant speed, brake torque is applied from the rear wheels to the front wheels. To reduce this phenomenon,
Japanese Patent Application Laid-Open No. 58-20521 proposes a method in which a wet multi-plate clutch is used in the connection part and the clutch is slid during cornering to absorb the difference in rotational speed between the front and rear wheels, but the transmission torque capacity is There was a risk of burnout due to burns or slips.

In view of these circumstances, the present invention was made in order to eliminate the problems that occur in the drive system due to the difference in rotational speed between the front wheels and the rear wheels during four-wheel drive driving. It is an object of the present invention to provide a four-wheel drive drive coupling device that absorbs the difference in rotational speed between rotary shafts that are drive-coupled.

A four-wheel drive drive coupling device of the present invention that achieves the above object has a first rotating shaft that transmits driving force to the front wheels of a vehicle, and a second rotary shaft that transmits driving force to the rear wheels of the vehicle.
and the first and second rotating shafts, and is driven by the difference in rotational speed between the first and second rotating shafts, and has an oil amount corresponding to the difference in rotational speed. In a four-wheel drive drive coupling device comprising a hydraulic pump that discharges a hydraulic pump, an oil passage is provided that communicates between a discharge port of the hydraulic pump and a suction port side oil passage,
The oil passage is characterized in that a flow control device is installed in the oil passage to control the flow resistance of the oil passage according to the load of the engine mounted on the vehicle.

Hereinafter, the content of the present invention will be specifically explained based on one example.

FIG. 1 shows a schematic configuration diagram of a four-wheel drive device using a four-wheel drive drive coupling device according to the present invention.

The output generated by the engine 1 is extracted as driving force from a drive gear 4 attached to an output shaft 3 of the engine 1 via a transmission 2 connected to the engine 1. 7
The driving force is transmitted to an intermediate transmission shaft 8 having a drive force, and the driving force is transmitted from one gear 7 of this intermediate transmission shaft 8 to a differential device 10 for the front wheels 9 to drive the front wheels 9.
The driving force transmitted to the front wheels 9 is directly transmitted to the first rotating shaft 11 via the gear 12, and is then transmitted to the second rotating shaft 14 via the four-wheel drive drive coupling device 13.
Furthermore, the driving force is transmitted to the differential device 17 for the rear wheels 16 via the gear mechanism 15 that changes the direction of rotation, thereby driving the rear wheels 16.

The four-wheel drive drive coupling device 13, as shown in its cross-sectional structure in FIG. 2, includes a vane pump 20, which is a hydraulic pump, and a hydraulic control circuit 21 attached thereto.
The vane pump has a rotor 20
a and a cam ring 20b, the rotor 20a
The cam ring 20b is connected to the first rotating shaft 11 to which the driving force to the front wheels 9 is directly transmitted, and the cam ring 20b is connected to the second rotating shaft 14 which transmits the driving force to the rear wheels 16.

This vane pump 20 discharges an amount of oil in proportion to its rotation speed, and pumps out an amount of oil between the rotor 20a and the cam ring 20.
When a relative rotation occurs between the first rotating shaft 11 and the second rotating shaft 14, it functions as a hydraulic pump and generates hydraulic pressure. By blocking the suction and discharge ports (which correspond to the suction and discharge ports), the rotor 20a and the cam ring 20b become like a rigid body and rotate together under the static pressure via the oil. As a result, cam ring 20
Two pump chambers are formed at diagonal positions of b, and there are four suction and discharge ports 2, which become suction ports when located on the proximal end side in the rotational direction and serve as discharge ports when located on the distal end side.
2, 23, 24, 25 are formed at diagonal positions, and the cam ring 2
The first oil passage 26 and the second oil passage 27 communicate with each other via a mechanism that allows oil to flow to the stationary side even in the rotating state of 0b.

Further, the hydraulic control circuit 21 includes check valves 28 and 28 between the first oil passage 26 and the second oil passage 27, respectively.
The oil reservoir 3 communicates with the oil reservoir 30 through the oil reservoir 29.
It is configured to form a one-way passage that only allows flow from 0, and further includes two opposing check valves 31 and 32 that allow only outflow between the first oil passage 26 and the second oil passage 27. Both oil passages 26, 2
7 are in communication, and the intermediate portions of the check valves 31 and 32 are in communication with a relief valve 33. This relief valve 33 is equipped with a spring 34 with a constant spring force, and a communication passage 35 is provided at the middle part on the side of the spring 34 to connect the oil reservoir 30 to the middle of the oil passage leading to the two check valves 28 and 29. Yes, spring 3
A check valve 36 is disposed at the top of the vane pump 20 and closes the discharge port of the vane pump 20 with a constant control pressure, and also closes the suction and discharge ports 22, 25 and 2 of the vane pump 20.
An oil passage 39 communicating both suction and discharge ports between 3 and 24,
40, and orifices 37, 38 as flow control means are interposed in the oil passages 39, 40 to perform the adjustment function of hydraulic control of the relief valve 33.

That is, the orifices 37 and 38 normally function as oil flow adjustment control means in the oil passages 39 and 40, and when the difference in rotational speed between the first rotation shaft and the second rotation shaft is small, , oil road 39,
Although oil does not flow into the inside of the relief valve 33, when the rotational speed difference increases and the discharge pressure of the vane pump 20 increases and exceeds the oil flow resistance of the orifice, the oil flows even if the set control pressure of the relief valve 33 is not reached. Road 3
Oil flows through the shafts 9 and 40, transmitting torque corresponding to the difference in rotational speed to the second rotating shaft, and adjusting the hydraulic control function of the relief valve 33.

When the hydraulic control circuit 21 is configured in this way,
Regardless of the relative rotation direction of the rotor 20a and cam ring 20b, when the difference in rotational speed between the front and rear wheels is small, the discharge pressure of the vane pump resists the flow resistance of the orifice and escapes through the oil passages 26 and 27 to the suction port. , torque corresponding to the rotational speed difference is transmitted to the rear wheels 16. On the other hand, when the difference in rotational speed between the two is large, the oil reservoir 3
communicates with the suction port. In this state, the relationship between the rotational speed difference of the front and rear wheels versus the discharge pressure when the orifice is not used (that is, when the auxiliary oil passages 37 and 38 are not used) and when it is used is shown in Figure 3. Curve a,
As shown in b, it can be seen that the discharge pressure is lower when an orifice is used (however, curve a shows the characteristic curve when an orifice is used, and curve b shows the characteristic curve when an orifice is not used.) The driving state by the four-wheel drive drive coupling device will be explained.

In a normal straight-ahead state, the effective radius of the tires of the front wheels 9 and the rear wheels 16 are the same and the slip rotational speed of the tires is small. There is no difference in rotational speed between the two and 14. Therefore, vane pump 20
Since no oil pressure is generated, drive is not transmitted to the rear wheels 16, resulting in front two-wheel drive using only the front wheels 9.

Furthermore, even when driving straight, the front wheels 9 usually slip within about 1%, even if there is no large slip as when accelerating, and this causes a difference in rotational speed. If the pressure is smaller than the flow resistance of the orifice, the vane pump discharge pressure should be changed to oil line 2.
6 and 27 to the suction port, and when the difference in rotational speed becomes large, the vane pump 20 functions to generate oil pressure corresponding to this difference in rotational speed, the rotor 20a and cam ring 20b rotate as one, and this oil pressure increases. A driving force corresponding to the pressure-receiving area of the vane is transmitted to the rear wheels 16, resulting in a four-wheel drive state. In this case, the oil flow in the vane pump 20 is
As shown in FIG. 22 and 24 serve as discharge ports to close check valves 28 and 32.
At the same time, the relief valve 33 is
(The solid line arrow in the figure indicates the flow of discharged oil,
The dashed arrows indicate the flow of suction oil).

Next, when the rotational speed of the front wheels 9 becomes very large compared to the rotational speed of the rear wheels 16, for example, when the rear wheels tend to lock up when driving on snowy roads, when accelerating suddenly, or when braking, four-wheel drive drive coupling device 13
The difference in rotational speed between the first rotating shaft 11 and the second rotating shaft 14 becomes very large, causing oil flow in the vane pump 20 as shown in FIG. 4a and generating a large hydraulic pressure. When the value is exceeded, the relief valve 33 opens against the spring 34 and the discharge port is controlled to be almost constant, resulting in a four-wheel drive state in which a constant driving force corresponding to a constant discharge pressure is transmitted to the rear wheels 16. . As a result, the rotational speed of the front wheels 9 decreases and the rotational speed of the rear wheels 16 increases, reducing the rotational speed difference, and when the front wheels 9 are in a slip state, the driving torque to the rear wheels 16 is increased. It is possible to avoid being unable to run, and when the rear wheels 16 are a little locked, the brake torque of the front wheels 9 is increased to prevent the rear wheels 16 from locking.

On the other hand, when the rotational speed of the rear wheels 16 becomes higher than the rotational speed of the front wheels 9, the relationship between the first rotational shaft 11 and the second rotational shaft 14 of the four-wheel drive drive coupling device 13 is opposite to the above case. A rotational speed difference occurs in the direction.
However, even if the difference is small and does not exceed the set value, the discharge pressure of the vane pump 20 causes the drive force to be released to the suction port through the orifice 37, thereby transmitting the driving force to the rear wheels, resulting in a four-wheel drive state.

Further, when the rotational speed of the rear wheels 16 becomes higher than the rotational speed of the front wheels 9, for example, when the brake state of the front wheels 9 becomes slightly locked, the first rotating shaft 11 of the four-wheel drive drive coupling device 13 A very large rotational speed difference occurs between the two rotating shafts 14, and in the vane pump 20, oil flows as shown in FIG. Oil reservoir 30 through
While oil is sucked in from the suction and discharge ports 23 and 25
becomes the discharge port and passes through the second oil passage 27 to the check valve 2.
9 and 31 are closed, a large oil pressure is introduced from the check valve 32 to the relief valve 33, and this oil pressure is also kept constant by the relief valve 33, and a constant driving force is transmitted to the rear wheels 16, resulting in a four-wheel drive state. becomes. As a result, the brake torque to the rear wheels 16 is increased to prevent the front wheels 9 from locking.

Further, during normal cornering, the rotational speed of the front wheels 9 is slightly higher than the rotational speed of the rear wheels 16, and the brake torque from the front wheels 9 acts, and the driving torque acts on the rear wheels 16, resulting in a four-wheel drive state. Turning is performed.

In this way, in the four-wheel drive drive coupling device 13, the discharge pressure is maintained at a constant value by the relief valve 33, and an oil passage with an orifice is provided, so that even if the rotation difference is small, the rotation difference exceeding a certain value can be prevented. When this occurs, the structure is configured to transmit torque according to the rotational speed difference to the rear wheels, and because the oil passage is blocked, the discharge pressure accumulates and increases, resulting in a large transmission even though the rotational speed difference is not that large. This eliminates the drawback that the amount of torque is transmitted to the rear wheels, and instead transmits torque to the rear wheels in proportion to the rotational difference, increasing the coupling force between the front and rear wheels and making four-wheel drive possible.

In this way, by controlling the discharge pressure in the four-wheel drive drive coupling device 13 using the relief valve 33 so that it does not exceed a certain value, when four-wheel drive mode is required in a conventional part-time four-wheel drive vehicle, Previously, the driver's operation was required, but now the system automatically switches between four-wheel drive and two-wheel drive, and a four-wheel drive state is now possible with the driving force commensurate with the difference in rotational speed between the front and rear wheels. It will be done. 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.

In the above explanation, the orifices 37 and 38 as the flow control means are explained as fixed flow resistance, but in the present invention, the flow control means interposed in the oil passages 39 and 40 is used to load the engine mounted on the four-wheel drive vehicle. It is of a variable orifice type that controls the flow resistance of the oil passages 39, 40 according to the conditions.

By using such a variable orifice as a flow control means, the following effects are produced.

When the engine load is large and the aperture is controlled to be large: When large driving force is required, four-wheel drive is activated,
Two-wheel drive is used when a small amount of driving force is sufficient, improving driving efficiency and fuel efficiency.

When driving in a tight corner, the accelerator is normally off (low load state), so the vehicle is in two-wheel drive mode and tight corner braking can be prevented. In addition, even if it is a tight corner, when it is better to apply a certain amount of driving force, such as on a snowy road, four-wheel drive can be used to achieve stable driving conditions.

Furthermore, when braking, the accelerator is normally turned off (low load) and the vehicle becomes two-wheel drive, so when an anti-skid brake device is installed, it is possible to use the one for two-wheel drive vehicles as is.

When controlling the aperture to be small when the engine load is high: By setting the maximum opening of the variable orifice to a value that allows a certain amount of flow resistance to remain, even when the engine is under high load, the rotational speed difference can be maintained at a specified level or higher. If so, it can be made into four-wheel drive. In addition, during braking, which is a low load state, the vehicle is likely to enter a four-wheel drive state, so it operates as described separately and prevents wheel locking even without installing an anti-skid brake device.

Therefore, the hydraulic control circuit 21 is equipped with a variable orifice type flow control means according to the engine load.
An example will be described based on FIGS. 5 and 6.

The four-wheel drive drive coupling device of the embodiment shown in FIG. 5 has an oil flow control device 41 having the structure shown in FIG. 5 instead of the orifices 37 and 38 in the oil passages 39 and 40 shown in FIG. Hydraulic pump 20 except for the
The configuration is the same as that shown in FIG. This flow control device 41 is arranged in each oil passage 42 that communicates between the discharge port and the suction port of the hydraulic pump, and is installed in a casing 43 arranged between the discharge port side oil path and the suction port side oil path 42. The communication hole 47 is configured to be able to be opened and closed by a needle valve 46 attached to a diaphragm 45 which can be expanded and contracted via a spring 44 depending on the magnitude of the engine (not shown) load.

In other words, as the engine torque increases,
Since the manifold negative pressure becomes smaller and the diameter of the orifice becomes smaller, the device should not be closed but left open to some extent. On the other hand, when the engine load decreases, the oil passage is opened further to increase the amount of slip on the front and rear wheels.
When the load on the engine increases, the driving force also increases, so the orifice in the oil passage should be made smaller.
It is driven by four wheels.

The device shown in FIG. 6 is a four-wheel drive drive coupling device according to the present invention.
See diagram. ) The construction of the hydraulic pump 20 is the same as that shown in FIG. 2, except that an oil flow control device 48 having the structure shown in FIG. 6 is arranged in place of the orifices 37 and 38 shown in FIG. This flow control device 48 is arranged in each sub-oil passage 42 that communicates between the discharge port and the suction port of the hydraulic pump, and is located in a casing 43 arranged between the oil passages 42 on the discharge port side and the suction port side. The transmission port 48a for transmitting the oil pump discharge pressure of the power steering of the handle, the transmission port 49 for transmitting the manifold negative pressure, and the suction side passage 42 are open, and the manifold negative pressure transmission port 49 of the casing 43 and the oil A piston 50 is disposed between the pump discharge pressure transmission ports 48a via a spring 44, and is housed so as to be movable up and down by the discharge pressure of the oil pump and the negative pressure of the manifold, and a needle valve 51 is provided at the lower end of the piston 50. , the discharge port of the oil passage 42 is arranged to be freely openable and closable.

When the flow control device 48 having this structure is used, the higher the steering angle, the higher the power steering oil pressure, so the needle valve 51 is moved backward, the oil passage is wide open, and the rotation difference between the front and rear wheels is reduced. Increase the tolerance, and when the front and rear wheels are running straight, if the rotation difference is large, torque is transmitted without allowing the rotation difference.

Also, input the manifold negative pressure into the transmission port 49,
By interlocking with the engine torque, the front and rear wheels can be switched to four-wheel drive as appropriate depending on the engine torque and the steering angle.

However, since there is a significant pressure difference between the manifold negative pressure and the power steering oil pressure, it is necessary to use a fairly strong spring 44.

In addition, means for variably restricting the flow depending on driving conditions, such as closing or opening the orifice diameter depending on the magnitude of brake oil pressure, or narrowing the orifice diameter when the accelerator is off, depending on the accelerator off operation. A similar purpose can be achieved by using

In the above embodiment, a vane pump was used as the hydraulic pump of the four-wheel drive drive coupling device, and the explanation was given on a balanced type with four suction and discharge ports, but depending on the amount of driving force transmitted, the number of suction and discharge ports It is also possible to use two unbalanced vane pumps, and other types of hydraulic pumps such as internal gear pumps, trochoid pumps, hypocycloid pumps, axial and radial plunger pumps, etc. It may be of a type in which the amount of oil discharged changes accordingly. Furthermore, the present invention is applicable not only to a type that drives the front wheels in a normal straight-ahead state but also to a type that drives the rear wheels. Furthermore, the transmission 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.

As described above in detail with the embodiments, according to the present invention, the first rotating shaft that transmits driving force to the front wheels and the second rotating shaft that transmits driving force to the rear wheels are rotated at these rotational speeds. The first rotary shaft and the second 2 The discharge port and suction port are automatically switched according to the relative rotation direction with the rotating shaft, so four-wheel drive can be achieved without any operation, making it ideal for part-time four-wheel drive vehicles in tight corners. It can eliminate problems such as braking phenomena and the complexity of driving operations, and 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, by installing a flow control means in the oil passage communicating between the discharge port and the suction port, which controls the flow resistance of the oil passage according to the load of the engine of the vehicle,
For example, it has the following effects:

() When the aperture is controlled to be large when the engine load is large: When large driving force is required, four-wheel drive is activated,
Two-wheel drive is used when a small amount of driving force is sufficient, improving driving efficiency and fuel efficiency.

When driving in a tight corner, the accelerator is normally off (low load state), so the vehicle is in two-wheel drive mode and tight corner braking can be prevented. In addition, even if it is a tight corner, when it is better to apply a certain amount of driving force, such as on a snowy road, four-wheel drive is used and stable driving conditions can be achieved.

Furthermore, when braking, the accelerator is normally turned off (low load) and the vehicle becomes two-wheel drive, so when an anti-skid brake device is installed, it is possible to use the one for two-wheel drive vehicles as is.

() When controlling the aperture to be small when the engine load is high: By setting the maximum opening of the variable orifice to a value that allows a certain amount of flow resistance to remain, the rotational speed difference can be maintained at a specified level even under high engine load conditions. If this is the case, four-wheel drive can be achieved. Furthermore, during braking, which is a low load state, the vehicle is more likely to enter a four-wheel drive state, so wheel locking can be prevented even without the use of an anti-skid brake device.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of a four-wheel drive vehicle using the four-wheel drive drive coupling device according to the present invention, and FIG. 2 is a diagram for explaining a configuration example of the four-wheel drive drive coupling device according to the present invention. A cross-sectional view, FIG. 3 is a comparison diagram of the characteristic curve of the front/rear wheel rotational speed difference versus discharge pressure between the four-wheel drive drive coupling device according to the present invention and the conventional four-wheel drive drive coupling device, and FIG. 4a and b are explanatory diagrams showing the oil flow path in the four-wheel drive drive coupling device shown in FIG. 2, respectively, and FIGS. 5 and 6 are both examples of the present invention connecting the discharge port and the suction port. FIG. 3 is a cross-sectional view of a main part showing the configuration of each example of a flow control device with variable flow resistance installed in an oil passage. In the drawing, 9 is a front wheel, 10 is a differential gear for the front wheels,
11 is a first rotating shaft, 13 is a four-wheel drive drive coupling device, 14 is a second rotating shaft, 16 is a rear wheel, 17 is a differential device for the rear wheels, 20 is a vane pump, 20a
is a rotor, 20b is a cam ring, 21 is a hydraulic control circuit, 22, 23, 24, 25 are suction and discharge ports, 2
6, 27 are the first and second oil passages, 28, 29, 3
1 and 32 are check valves, 30 is an oil reservoir, 33 is a relief valve, 37 and 38 are orifices, 39 and 4
0 is an oil passage communicating the discharge port and the suction port, 41, 4
8 is a flow control device with variable flow resistance.

Claims (1)

[Claims] 1 A first rotating shaft that transmits driving force to the front wheels of a vehicle, a second rotating shaft that transmits driving force to the rear wheels of the vehicle, and a means for connecting the first and second rotating shafts. , and a hydraulic pump that is driven by a difference in rotational speed between the first and second rotating shafts and discharges an amount of oil according to the difference in rotational speed, wherein the hydraulic pump is An oil passage communicating between the discharge port and the suction port side oil passage is provided, and a flow control means is interposed in the oil passage for controlling the flow resistance of the oil passage according to the load of the engine mounted on the vehicle. A four-wheel drive drive coupling device featuring: