JPH0215699Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a drive coupling device for a four-wheel drive vehicle in which front wheels and rear wheels are driven by the same engine.

The drive coupling device for a four-wheel drive vehicle according to the present invention includes a hydraulic pump interposed between a first rotating shaft connected to the front wheel side and a second rotating shaft connected to the rear wheel side, so that the front wheel or the rear wheel If there is a difference in rotational speed between the first rotating shaft and the second rotating shaft, such as in a slipping state, the oil discharged from the hydraulic pump is regulated, and the static pressure inside the hydraulic pump is used to control the first rotating shaft. This system rigidly connects the drive and the second rotating shaft to automatically achieve four-wheel drive, but it has the following problems like the drive coupling device for general four-wheel drive vehicles. .

In other words, by driving both the front and rear wheels, a four-wheel drive vehicle has extremely high acceleration performance and the ability to travel on roads with a small coefficient of friction (mud, snow, etc.), but when driving at high speeds, the front wheels Due to the slight difference in the effective diameter of the tires between the front and rear wheels, the collision of the gear train between the front and rear wheels, etc., the difference in rotational speed between the front and rear wheels, which was originally slight, has become so large that it cannot be ignored, and as a result, the rotational speed has increased. The brakes were applied to the wheels that rotated faster by the slower wheels, and the efficiency of transmitting driving force to each wheel deteriorated.

The present invention was devised in view of the above-mentioned conventional problems, and its purpose is to provide a drive coupling device for four-wheel drive vehicles that automatically eliminates the problems that occur when driving at high speeds in four-wheel drive mode. do.

The configuration of the present invention that achieves the above object includes a first rotating shaft connected to the front wheels of the vehicle, a second rotating shaft connected to the rear wheels of the vehicle, and the first rotating shaft and the second rotating shaft connected to the front wheels of the vehicle. A drive coupling device for a four-wheel drive vehicle comprising a hydraulic pump coupled to each other and driven by a rotational speed difference between both rotating shafts and discharging an amount of oil according to the rotational speed difference, the discharge port side of the hydraulic pump. An auxiliary oil passage that communicates between the passage and the suction port side passage and is provided with a variable throttle, and a control means that controls the variable throttle to reduce the throttle amount as the traveling speed of the vehicle increases. It is characterized by having

Hereinafter, one embodiment of the present invention will be described based on the drawings. FIG. 1 is a schematic configuration diagram showing the drive system of a four-wheel drive vehicle as an embodiment of the present invention, FIG. 2 is a cross-sectional view of a hydraulic pump of the device of this embodiment, and FIG. 3 is a longitudinal sectional view thereof. FIGS. 4a, b, and c are sectional views of the variable aperture section of the device of this embodiment, and FIG. 5 is a graph explaining the operation.

As shown in FIG. 1, a transmission 2 is connected to an engine 1 placed horizontally, and driving force is taken out from a drive gear 4 attached to an output shaft 3 of the engine 1, and is transmitted to both ends of the engine via an idle gear 5. 6, 7 is transmitted to an intermediate transmission shaft 8.

Then, the driving force is transmitted from one gear 7 of this intermediate transmission shaft 8 to the differential device 10 for the front wheels 9 to drive the front wheels 9, while the driving force transmitted to the front wheels 9 is directly transmitted to the first rotation. The power is transmitted to the shaft 11 via the gear 12, and further to the four-wheel drive drive coupling device main body 13, which is a vane pump type coupling mechanism.

The driving force that has passed through the four-wheel drive drive coupling device main body 13 is transmitted to the second rotating shaft 14, and is transmitted to the rear wheel 16 via a gear mechanism 15 that changes the direction of rotation. The driving force is transmitted to the differential device 17 to drive the rear wheels 16.

As shown in FIGS. 2 and 3, this four-wheel drive drive coupling device body 13 is composed of a vane pump VP as a hydraulic pump and a hydraulic circuit 21 attached thereto, and a rotor 19 of the vane pump VP.
is the first rotating shaft 11 that transmits the driving force to the front wheels 9.
The cam ring portion 20a, the annular plate 20b, and the output side plate 20c, which constitute the casing 20, are connected to the second rotating shaft 14 that transmits driving force to the rear wheel 16.

This vane pump VP as a hydraulic pump has
A large number (8 in this case) of holes 19b are formed at equal intervals in the circumferential direction on the outer circumferential surface 19a of the rotor 19, and each of the large number of holes 19b is provided on the inner circumferential surface of the cam ring portion 20a. A vane 18 that can be slidably contacted with 20d is fitted.

Further, the vane pump VP discharges an amount of oil proportional to its rotation speed, and there is a relative rotation between the rotor 19 and the cam ring part 20a, that is,
When 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 discharge ports of the vane pump VP (corresponding to the suction and discharge ports 22 to 25 at the tip of the vane 18 in the relative rotational direction with respect to the casing 20), the rotor 19 and the cam ring portion 20a are connected to each other by the static pressure through the oil. It becomes like a rigid body and rotates as one.

Therefore, two pump chambers 36 and 37 are formed at diagonal positions between the cam ring part 20a and the rotor 19, and when it is located on the base end side in the rotational direction, it becomes a suction port, and when it is located on the distal end side, it becomes a discharge port. Four suction/discharge ports 22 to 25 serving as outlets are formed at substantially diagonal positions, and the diagonally positioned suction/discharge ports 22, 24 and suction/discharge ports 23, 25, each having the same function, are connected to the cam ring. The first oil passage 26 and the second oil passage are connected through a mechanism that allows oil to flow even when the portion 20a is in rotation.
It is communicated with the oil passage 27.

Moreover, between the first oil passage 26 and the second oil passage 27,
The oil reservoir 30 is communicated with each other through the check valves 28, 29, 29', and only the flow from the oil reservoir 30 to each oil passage 26, 27 is allowed, and the first oil passage 26 and the second oil passage 27 two opposing check valves 31 that allow only outflow between the
Both oil passages 26 and 27 communicate with each other via a check valve 32, and an intermediate portion between these two check valves 31 and 32 is connected to an oil passage 40.
It communicates with the relief valve 33 via.

Through the middle part of the relief valve 33 on the spring 34 side, there is a connection between the oil reservoir 30 and the check valve 29' and the two check valves 28 and 29.
A communication path 35 is provided.

With such a hydraulic circuit 21, the discharge pressure always acts on the valve body of the relief valve 33, regardless of the relative rotation direction between the rotor 19 and the cam ring portion 20a, and the oil reservoir 30 communicates with the suction port. become.

Further, an auxiliary oil passage 38 is provided which communicates the oil passage 26 connected to the suction discharge port 24 and the oil passage 27 connected to the suction discharge port 23.
An auxiliary oil passage 39 is provided that communicates the oil passage 26 connected to the suction and discharge port 25 with the oil passage 27 connected to the suction discharge port 25. Each vehicle is provided with a variable aperture M whose aperture diameter increases as the traveling speed increases. The variable throttle M is a spool 4 that is slidably housed in a case 45 in which sub passages 38 and 39 are formed.
6 and a spring 47 that always presses the spool 46 to close the sub passages 38 and 39.
For example, the spool 46 may be controlled by a control means that generates a known acting force corresponding to the traveling speed, such as centrifugal force generated by rotating the case 45 in accordance with the traveling speed or governor pressure of a vehicle equipped with an automatic transmission. It is moved against the spring 47, and the sub passage 38,
The diameter of 39 is made variable. Note that 48 in FIG. 4 is a passage for opening the inside of the case 45 to the outside air and allowing movement of the spool 46, but when applying governor pressure to the spool 46 as described above, this governor pressure This will be the introduction route for

According to the drive coupling device for a four-wheel drive vehicle configured as described above, there is a rotational speed difference between the front wheels 9 and the rear wheels 16 (between the first rotation shaft 11 and the second rotation shaft 14). If there is no oil pressure generated in the vane pump VP, no driving force is transmitted to the rear wheels 16,
It is two-wheel drive using only the front wheels 9.

However, in a situation where the front wheels 9 normally slip within about 1% even if there is no large slip, such as when the vehicle is accelerating straight ahead, the rotational speed difference due to this is the first.
When the rotational speed difference is generated between the rotational shaft 11 and the second rotational shaft 14, the vane pump VP functions to generate oil pressure corresponding to this rotational speed difference, and the rotor 19 and the cam ring part 20a rotate as one. A driving force is transmitted to the rear wheels 16 in accordance with this oil pressure and the pressure-receiving area of the vane, resulting in a four-wheel drive state.

In this case, the oil flow in the vane pump VP is caused by the relative rotation of the rotor 19 (see symbol A in FIG. 2), and the suction and discharge ports 22, 24
serves as a suction port and oil is sucked in from the oil reservoir 30 via the check valve 28, while the suction and discharge port 2
3 and 25 serve as discharge ports and check valves 29 and 31
At the same time as the valve is closed, oil is introduced to the relief valve 33 via the check valve 32 and the oil passage 40, and the flow of this discharged oil is blocked by the relief valve 33. As a result, the pressure inside the vane pump VP increases, and the rotor 19 and the cam ring portion 20a rotate together as described above.

In FIG. 2, 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 front wheels 9 becomes much higher than the rotational speed of the rear wheels 16, for example, when the front wheels slip on a snowy road, or when the rear wheels tend to lock up during sudden acceleration or braking, , a first rotating shaft 11 connected to the four-wheel drive drive coupling device main body 13
The rotational speed difference between the rotational speed and the second rotating shaft 14 becomes very large.

As a result, in the vane pump VP, an oil flow as shown in Fig. 2 occurs and a large hydraulic pressure is generated, but when a predetermined value is exceeded, the relief valve 33 opens against the spring 34 and the discharge pressure becomes almost constant. A four-wheel drive state is established in which a constant driving force corresponding to a constant discharge pressure is transmitted to the rear wheels 16.

This reduces the rotational speed difference that causes the rotational speed of the front wheels 9 to decrease and the rotational speed of the rear wheels 16 to increase (same function as a non-slip differential).
I come to do it.

In this way, when the front wheel 9 is in a slip state, the rear wheel 1
In addition, when the rear wheels 16 tend to lock up, the brake torque of the front wheels 9 is increased to prevent the rear wheels 16 from locking up.

On the other hand, if the rotational speed of the rear wheels 16 becomes very large compared to the rotational speed of the front wheels 9, for example, if the brake state of the front wheels 9 becomes a little locked, the first A very large rotational speed occurs between the rotating shaft 11 and the second rotating shaft 14 in the opposite direction to that described above.

As a result, in the vane pump VP, an oil flow occurs in the opposite direction to the oil flow shown in FIG. 2, the suction and discharge ports 23 and 25 become suction ports, and the check valve 2
Oil is sucked in from the oil reservoir 30 through the oil reservoir 30 through the oil reservoir 30 through the oil passages 9 and 29', and the suction and discharge ports 22 and 24 serve as discharge ports, passing through the second oil passage 26, closing the check valves 28 and 32, and transferring the oil from the check valve 32 to the relief valve. A large hydraulic pressure guided to the rear wheels 16 is applied, but this hydraulic pressure is also held 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.

Then, the brake torque to the rear wheels 16 is increased to prevent the front wheels 9 from locking.

In this way, the four-wheel drive drive coupling device main body 13
By controlling the discharge pressure so that it does not exceed a certain value using the relief valve 33, conventional part-time four-wheel drive vehicles that require operation by the driver when four-wheel drive is required can be removed. , automatic switching between four-wheel drive and two-wheel drive is performed, and a four-wheel drive state is obtained with a driving force according to the rotational speed difference between the front wheels 9 and the rear wheels 16.

By the way, the device of the present invention is equipped with sub passages 38 and 39, and as mentioned above (see FIG. 4),
Due to the relationship between the spring constant of the spring 47, the weight and diameter of the spool 46, and the acting forces (centrifugal force, governor pressure, etc.), the diameters of the sub passages 38 and 39 gradually change from zero as the running speed increases due to the variable throttle M. becomes larger and the amount of aperture is reduced. [In this example, the traveling speed
Diameter 0 mm at 20 km/h (Fig. 4 a), traveling speed 60
km/h, diameter 2mm (Figure 4 b), traveling speed 100km/h
h and a diameter of 3 mm (Fig. 4c)]. In other words, sub passage 3
When a difference in rotational speed occurs between the first rotating shaft 11 and the second rotating shaft 14 due to a change in the diameters of the vane pumps 8 and 39, the discharge oil pressure of the vane pump VP changes depending on the running speed as shown in FIG. When the traveling speed is high, the discharge oil pressure does not increase much until the rotational speed becomes relatively high, resulting in a two-wheel drive state. Therefore, in this high-speed running state, a difference in rotational speed between the first rotating shaft 11 and the second rotating shaft 14 occurs due to the difference in the effective tire diameters of the front and rear wheels, the backtexturing of the gear train, etc. However, this is within an acceptable range, and the deterioration in driving force transmission efficiency caused by four-wheel drive is eliminated.

On the other hand, when the running speed is low, even if the difference in rotational speed is relatively small, the discharge oil pressure increases and four-wheel drive is activated. The system quickly responds to wheel slippage and switches to four-wheel drive, achieving extremely high acceleration and all-terrain performance.

Generally speaking, the so-called tight corner braking phenomenon, which is a phenomenon in which braking is applied to the wheels due to the difference in rotational distance between the front and rear wheels when attempting to make a sharp turn during low-speed driving with four-wheel drive, is explained, for example, by power steering. Spool 4 for operating hydraulic pressure
In this case, the diameters of the sub passages 38 and 39 may be increased to put the vehicle in a two-wheel drive state. In addition, in the above embodiment, a balanced vane pump with four suction and discharge ports was used as the hydraulic pump, but the hydraulic pump has two suction and discharge ports.
unbalanced vane pumps and other types of hydraulic pumps, such as internal gear pumps, trochoid pumps,
Hypocycloid pumps, axial pumps, radial plunger pumps, and the like can be used as long as the amount of oil discharged changes depending on the rotational speed difference. Further, as a valve mechanism for regulating the flow of oil discharged from the vane pump VP, in addition to the above-mentioned relief valve 33, other well-known mechanisms such as a solenoid valve whose duty is controlled or opened/closed by a computer can be used.

As explained above, according to the present invention, as the traveling speed of the vehicle increases, the auxiliary passage that communicates the discharge port side passage and the suction side passage of the hydraulic pump that transmits driving force to the front wheels and the rear wheels. Since a variable throttle is provided to reduce the throttle amount, the vehicle does not needlessly switch to four-wheel drive when traveling at high speed without large slips, and it is possible to prevent deterioration of the driving force transmission efficiency.

[Brief explanation of drawings]

Fig. 1 is a schematic configuration diagram showing a drive system of a four-wheel drive vehicle as an embodiment of the present invention, and Fig. 2 is a cross-sectional view of a hydraulic pump provided in a drive coupling device as an embodiment of the present invention. , FIG. 3 is a longitudinal sectional view thereof, FIGS. 4 a, b, and c are sectional views of the variable aperture portion, and FIG. 5 is a graph explaining the operation. In the drawing, 9 is a front wheel, 11 is a first rotating shaft, 14 is a second rotating shaft, 16 is a rear wheel, 19 is a rotor, 20 is a casing, 22, 23, 24, 25 are discharge and suction ports, and 33 is a relief valve. , 38, 39 are sub passages,
VP is a vane pump, and M is a variable throttle.

Claims (1)

[Scope of utility model registration request] A first rotating shaft connected to the front wheel side of the vehicle, a second rotating shaft connected to the rear wheel side of the vehicle, and a second rotating shaft connecting the first rotating shaft and the second rotating shaft and adjusting the rotational speed difference between the two rotating shafts. A drive coupling device for a four-wheel drive vehicle comprising a hydraulic pump that is driven by a hydraulic pump and discharges an amount of oil according to a rotational speed difference, the hydraulic pump having a discharge port side passage and a suction port side passage connected to each other, and A four-wheel drive vehicle comprising: an auxiliary oil passage provided with a variable throttle; and a control means for controlling the variable throttle to reduce the throttle amount as the vehicle speed increases. drive coupling device.