JPH0344581Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a four-wheel drive system for a vehicle in which front wheels and rear wheels are driven by the same engine via a hydraulic pump.

<Conventional technology> A four-wheel drive system for a vehicle uses the same engine to simultaneously drive the front wheels and rear wheels. Since the driving force and braking force are transmitted from the rear wheels to the road surface, the vehicle's sudden starting performance and sudden braking performance are excellent.

The applicant has already developed the following four-wheel drive system for vehicles that can automatically transmit drive torque to the front and rear wheels when necessary and exhibit the excellent performance described above. Proposed. That is, a hydraulic pump is 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 when the front wheel or rear wheel slips, the first rotating shaft and the second rotating shaft The discharge of hydraulic pressure generated by the hydraulic pump is regulated when a rotational speed difference (differential) occurs between the first and second rotating shafts using the static pressure within the hydraulic pump. It is rigidly connected and automatically achieves four-wheel drive.

<Problems to be solved by the invention> Even with the previously proposed vehicle four-wheel drive system described above, the so-called cornering braking phenomenon occurs, similar to a general four-wheel drive system that constantly transmits drive torque to the front and rear wheels. There was a problem that this occurred. In other words, when a vehicle turns, a difference in track length occurs between the front and rear wheels, creating a differential between the front and rear wheels, but in four-wheel drive, this differential is inhibited and the rotational speed is reduced. A phenomenon occurred in which a wheel with a faster rotation speed was braked by a wheel with a slower rotation speed.

An object of the present invention is to provide a four-wheel drive system for a vehicle that improves the previously proposed system described above and prevents the so-called cornering braking phenomenon while maintaining the performance of four-wheel drive.

<Means for Solving the Problems> The four-wheel drive system for a vehicle of the present invention has a first rotary shaft connected to the front wheels of the vehicle, a second rotary shaft connected to the rear wheels of the vehicle, and a rotatable four-wheel drive system of the present invention. The rotor has a casing supported by and connected to either the first rotating shaft or the second rotating shaft, and a rotor connected to the other rotating shaft and rotatably housed in the casing. a hydraulic pump that is driven by a rotational speed difference between a first rotating shaft and the second rotating shaft and discharges an amount of oil according to the rotational speed difference; an oil passage on a discharge port side and an oil passage on a suction port side of the hydraulic pump; and a variable throttling mechanism that detects a change in the amount of oil discharged from the hydraulic pump and throttles the flow path of the auxiliary oil path as the change in the amount of oil discharged increases. Features.

<Operation> When a rotational speed difference (differential) occurs between the front wheels and the rear wheels, a state is created in which driving torque is transmitted to the front wheels and the rear wheels respectively via the hydraulic pump. In this case, when there is no sudden differential change between the front and rear wheels and the amount of oil discharged from the hydraulic pump is constant or changing slowly, the amount of oil determined by the auxiliary oil passage is determined by the amount of oil at the outlet depending on this amount of oil discharged. The oil is allowed to flow from the side oil passage to the suction port side oil passage, and a relatively small differential between the front and rear wheels that occurs when the vehicle turns is allowed to prevent the so-called cornering braking phenomenon from occurring. On the other hand, during sudden acceleration or sudden braking, when the amount of oil discharged from the hydraulic pump changes rapidly, the flow path of the auxiliary oil passage is throttled in response to this change, reducing the pressure from the discharge side oil passage to the suction side oil passage. It controls the flow of oil and transmits almost equal drive torque to the front and rear wheels.

<Example> An example of the present invention will be described based on the drawings.
FIG. 1 is a configuration diagram showing the drive system of a vehicle to which the four-wheel drive device of this embodiment is applied, FIG. 2 is a configuration diagram showing the four-wheel drive device of this embodiment with a hydraulic pump in a cross section Figure 3 is a vertical cross-sectional view of the hydraulic pump, and Figure 4 is a vertical cross-sectional view of the hydraulic pump.
The figure is a sectional view of the variable diaphragm mechanism, FIG. 5 is a sectional view taken along the - arrow in FIG. 4, and FIG. 6 is a graph for 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 signal is transmitted to the shaft 11 via the gear 12 and further to the four-wheel drive device 13.

The driving force via this four-wheel drive device 13 is transmitted to a second rotating shaft 14,
The driving force is transmitted to a differential device 17 for the rear wheels 16 via a gear mechanism 15 that changes the direction of rotation, and drives the rear wheels 16.

As shown in FIGS. 2 and 3, this four-wheel drive device 13 is composed of a vane pump VP as a hydraulic pump and a hydraulic circuit 21 attached thereto.
A rotor 19 of the vane pump VP is connected to a first rotating shaft 11 that transmits driving force to the front wheel 9, and a cam ring portion 2 that constitutes a casing 20
0a, the annular plate 20b, and the output side plate 20c are connected to the second rotating shaft 14 that transmits driving force to the rear wheel 16.

In this vane pump VP, a large number (10 holes 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 with a cam ring. A vane 18 that can be slidably contacted with the inner circumferential surface 20d of the portion 20a 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 27 at the tips of the vanes 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, there are three pump chambers 28, 29, 3 at equal intervals between the cam ring part 20a and the rotor 19.
0 is formed, and six suction and discharge ports 22 to 27, which are the suction port when located on the proximal side in the rotational direction and the discharge port when located on the distal side in the rotational direction, are formed at approximately equal intervals, and are identical to each other. Functional suction and discharge ports 22, 24, 26 and suction and discharge ports 23, 25, 2
7 are in communication with the first oil passage 31 and the second oil passage 32 via a mechanism that allows oil to flow even when the cam ring portion 20a is in rotation.

Moreover, between the first oil passage 31 and the second oil passage 32,
An oil reservoir 35 is communicated via check valves 33 and 34, respectively, and oil passages 31 and 35 are connected from the oil reservoir 35 to each oil passage 31,
32 is allowed, and the first oil passage 3
Both oil passages 31 and 32 are communicated with each other through two opposing relief valves 36 and 37 that allow only outflow. Note that these relief valves 36 and 37 each have a spring 36.
a, 37a, and is biased to a normally closed state, and opens when hydraulic pressure exceeding a certain level is applied, which exceeds this biasing force.

With such a hydraulic circuit 21, the discharge pressure always acts on the relief valves 36 and 37 regardless of the relative rotational direction between the rotor 19 and the cam ring part 20a, and the oil reservoir 35 communicates with the suction port. Become.

Further, an auxiliary oil passage 38 is provided that communicates an oil passage 31 connecting the suction and discharge ports 22, 24, and 26 with an oil passage 32 that connects the suction and discharge ports 23, 25, and 27. As shown in FIGS. 4 and 5, a variable throttle mechanism M is provided whose throttle diameter decreases as the change in the amount of oil discharged from the vane pump VP increases. The variable throttle mechanism M of this embodiment is such that its throttle diameter decreases as the amount of oil discharged from the vane pump VP increases.

The variable throttle mechanism M includes a pair of pistons 40 and 41 that are slidably housed in a case 39 in which an auxiliary oil passage 38 is formed, with a gap serving as a flow passage around the periphery.
A pair of springs 44 and 45 that bias the respective pistons 40 and 41 to form gaps 42 and 43 that serve as flow paths between the stepped portion 39a of the case 39 and the pistons 40 and 41, respectively, and the respective pistons 40. , 41, and a pair of annular stoppers 46, 47 for preventing the piston 4 from coming off.
When the springs 44 and 45 of 0 and 41 act from the opposite ends, the piston 4 moves according to the magnitude of this oil pressure.
When the gaps 42, 43 between 0, 41 and the stepped portion 39a are narrowed, and this oil pressure, that is, the amount of circulating oil increases rapidly, the gaps 42, 43 are temporarily further narrowed in response to this change. It's summery. Therefore, when there is no differential between the front wheels 9 and the rear wheels 16 and the vane pump VP does not function, the gaps 42, 4
3 both have a certain opening degree, and when the differential is a certain amount and the amount of oil discharged from the vane pump VP is constant, the gaps 42 and 43 open to an opening degree corresponding to this discharge oil pressure. When the differential is gradually changed and the amount of oil discharged from the vane pump VP is gradually changed, the gaps 42 and 43 are also gradually changed to the opening degree corresponding to this discharge oil pressure, and the vehicle When the differential changes rapidly and the amount of oil discharged from the vane pump VP increases rapidly, such as during sudden acceleration or sudden braking, the gaps 42 and 43 adjust the amount of increase according to the magnitude of this change. Temporarily narrowed down to the above.

According to the four-wheel drive device configured as described above, between the front wheels 9 and the rear wheels 16 (first rotating shaft 11
If there is no rotational speed difference (differential) between the second rotary shaft 14 and the second rotating shaft 14, no hydraulic pressure is generated in the vane pump VP, and no driving force is transmitted to the rear wheels 16.
It is two-wheel drive using only the front wheels 9. Also, when the vehicle is turning, a differential is generated between the front wheels 9 and the rear wheels 16, but if the amount of differential does not change significantly due to sudden acceleration or braking, this differential will generate a differential in the vane pump VP. Hydraulic pressure passes through the auxiliary oil passage 38 to the first
Most of the problem is eliminated by the pressure oil flowing between the oil passage 31 and the second oil passage 32, maintaining the same two-wheel drive condition as described above, and achieving smooth turning without cornering braking.

On the other hand, if the front wheels 9 slip on a snowy road, or if the rear wheels 16 lock up during braking, the front wheels 9 may
When the rotational speed of the vane pump VP becomes relatively large, a hydraulic pressure corresponding to this rotational speed difference is generated in the vane pump VP. In this case, the hydraulic pressure exceeds the flow capacity of the sub passage 38, and the rotor 19 and the cam ring part 2
0a rotates integrally like a rigid body via pressure oil, and the driving torque to the front wheels 9 is also transmitted to the rear wheels 16, resulting in a four-wheel drive state. In this case, as shown in FIG. 2, in which the flow of discharged oil is shown by a solid line arrow and the flow of suction oil is shown by a broken line arrow, the flow of oil in the vane pump VP is caused by the relative rotation of the rotor 19.
The suction and discharge ports 23, 25, and 27 function as suction ports, and oil is sucked in from the oil reservoir 35 through the check valve 34, while the suction and discharge ports 22, 24, and 26 function as discharge ports, and the check valve 33 is closed. At the same time, oil is guided to the relief valves 36, 37, and the flow of this discharged oil is blocked by the relief valves 36, 37. This increases the pressure inside the vane pump VP, causing
As described above, the rotor 19 and the cam ring portion 20a rotate together. Here, the rotation speed of the front wheel 9 becomes much larger than that of the rear wheel 16, and the vane pump
When the hydraulic pressure generated at VP exceeds a predetermined value, the relief valve 36 opens against the spring 36a to control the discharge hydraulic pressure to be approximately constant, and transmits a driving torque corresponding to the constant discharge hydraulic pressure to the rear wheels 16. The vehicle is in four-wheel drive mode. As a result of the above, the rotational speed of the front wheels 9 decreases and the rotational speed of the rear wheels 16 increases, reducing the rotational speed difference (same function as a non-slip differential). In this state, the driving torque to the rear wheels 16 is increased and the vehicle becomes unable to run, and when the rear wheels 16 are slightly locked, the brake torque of the front wheels 9 is increased to prevent the rear wheels 16 from locking. do.

On the other hand, 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 connected to the four-wheel drive device 13 A very large rotational speed is generated in the opposite direction to the above-mentioned direction between the rotational shaft 14 of No. This allows vane pump VP
In this case, an oil flow occurs in the opposite direction to the oil flow shown in FIG. Suction and discharge ports 23, 25, 2
7 becomes a discharge port and closes the check valve 34 via the second oil passage 32, and when hydraulic pressure exceeding a predetermined value acts on the relief valve 37, this hydraulic pressure is also discharged from the relief valve 37.
A constant driving force is transmitted to the rear wheels 16, resulting in a four-wheel drive state.

As described above, the amount of torque transmitted between the front wheels 9 and the rear wheels 16 is gradually increased in accordance with the increase in the rotational speed difference between the front wheels 9 and the rear wheels 16, and this rotational speed difference reaches a certain value. In this case, the two-wheel drive state and the four-wheel drive state are automatically switched with the characteristic that the transmitted torque is approximately constant (as shown by the dotted line in FIG. 6).

By the way, when suddenly accelerating or braking, the front wheel
When a sudden change in the differential amount occurs between the vane pump VP and the rear wheel 16, that is, a sudden increase in the amount of oil discharged from the vane pump VP, the auxiliary oil passage 38 flow path is throttled according to the magnitude of this change. . Therefore, front wheel 9 and rear wheel 1
Even if there is a slight difference in rotational speed between the rotor 19 and the cam ring portion 20a of the vane pump VP, the rotor 19 of the vane pump VP and the cam ring portion 20a rotate together through pressure oil, resulting in four-wheel drive. In other words, as shown by the solid line in Figure 6, the above characteristics result in the shift to four-wheel drive being earlier;
Excellent sudden acceleration performance and sudden braking performance are effectively demonstrated in four-wheel drive mode.

The variable throttling mechanism M shown in the above embodiment throttles the flow path of the auxiliary oil passage 38 not only according to changes in the amount of oil discharged from the vane pump VP but also according to the amount of oil discharged. The detection is made to operate the actuator, thereby operating the variable throttle provided in the auxiliary oil passage 38.
The flow path throttling control may be performed only in response to changes in the amount of discharged oil. In the above embodiment, a balanced vane pump with six suction and discharge ports was used as the hydraulic pump. , hypocycloid pumps, axial and radial plunger pumps, etc., which can change the amount of oil discharged depending on the rotational speed difference, can be used. In addition, as a valve mechanism for regulating the flow of oil discharged from the vane pump VP, the relief valve 36,
In addition to 37, other known valves such as a solenoid valve whose duty is controlled or whose opening/closing is controlled by a computer may be used.

<Effects of the invention> According to the four-wheel drive system for a vehicle of the present invention, it is possible to effectively prevent the cornering braking phenomenon while maintaining the excellent performance of four-wheel drive, especially rapid acceleration performance and sudden braking performance. can.

[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, FIG. 4 is a sectional view of the variable diaphragm mechanism, FIG. 5 is a sectional view taken along the - arrow in FIG. 4, and FIG. 6 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, 26, 2
7 is a discharge suction port, 36 and 37 are relief valves, 38
is a sub passage, VP is a vane pump, and M is a variable throttle mechanism.

Claims (1)

[Scope of utility model registration request] A first rotation shaft connected to the front wheel side of the vehicle, a second rotation shaft connected to the rear wheel side of the vehicle, and a rotary shaft rotatably supported and connected to either the first rotation shaft or the second rotation shaft. and a rotor connected to the other rotating shaft and rotatably housed in the casing, the first rotating shaft and the second rotating shaft are connected to each other.
a hydraulic pump that is driven by a rotational speed difference with a rotating shaft and discharges an amount of oil according to the rotational speed difference; and an auxiliary oil passage that communicates an oil passage on a discharge port side and an oil passage on a suction port side of the hydraulic pump. , a variable throttle mechanism that detects a change in the amount of oil discharged from the hydraulic pump and throttles the flow path of the auxiliary oil passage as the change in the amount of oil discharged increases. Device.