JPH0421709Y2 - - 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 driving force and braking force are transmitted from the rear wheels to the road surface, the vehicle's sudden acceleration and 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 for a vehicle 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; and a hydraulic pressure on a discharge port side and an oil path on a suction port side of the hydraulic pump. The vehicle is characterized by comprising: a sub-oil passage that communicates with the sub-oil passage; and a variable throttling mechanism that detects acceleration in the forward and backward directions of the vehicle and throttles the passage of the sub-oil passage as the acceleration increases.

<Function> The amount of oil determined by the auxiliary oil path is allowed to flow from the oil path on the discharge port side of the hydraulic pump to the oil path on the suction port side, allowing for a relatively small differential between the front and rear wheels that occurs when the vehicle turns. Prevent cornering brake phenomenon from occurring. On the other hand, during sudden acceleration or sudden braking, where the acceleration in the forward and backward direction of the vehicle increases, the flow of the auxiliary oil passage is throttled to reduce the flow of pressure oil from the oil passage on the discharge port side of the hydraulic pump to the oil passage on the suction port side. It controls 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, and FIG. 5 is a graph explaining the action.

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 through check valves 33 and 34, respectively, and the oil passages 31,
Both oil passages 31 and 32 are connected via two opposing relief valves 36 and 37 that allow only flow to 32 and allow only outflow between the first oil passage 31 and the second oil passage 32. are being communicated. Note that these relief valves 36 and 37 are each connected to a spring 3.
6a and 37a are biased to the normally closed state,
It is designed to open when a certain level of hydraulic pressure that exceeds this biasing force is applied.

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 FIG. 4, a variable aperture mechanism M is provided whose aperture diameter becomes smaller as the acceleration in the forward and backward directions of the vehicle increases. The variable throttle mechanism M includes a spool 40 that is slidably housed in a case 39 in which an auxiliary oil passage 38 is formed, and a spool 40 that is biased from both ends of the spool 40 to maintain the spool 40 at a neutral position. A pair of springs 41, 4 that open at a predetermined aperture
2, and this spool 40 is arranged so as to be able to slide back and forth in the direction of travel of the vehicle in response to the acceleration and deceleration of the vehicle. Therefore, the spool 40 is in the neutral position during normal running of the vehicle where no acceleration occurs in the forward or backward direction of travel, allowing the flow of a predetermined amount of pressure oil or less in the auxiliary oil passage 38; Like spool 4
When an acceleration that exceeds the biasing force of the springs 41 and 42 acts on the spool 40, the spool 40 moves according to the magnitude of this acceleration and narrows the flow path of the auxiliary oil passage 38 to reduce or reduce the amount of pressure oil flowing through the auxiliary oil passage 38. The oil passage 38 is shut off.

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 vane pump VP 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. Furthermore, when the vehicle is turning, a slight differential occurs between the front wheels 9 and the rear wheels 16, but this slight differential occurs when there is no large acceleration forward or backward in the direction of travel due to sudden acceleration or sudden braking. The hydraulic pressure generated in the vane pump VP due to the movement is canceled by the pressure oil flowing between the first oil passage 31 and the second oil passage 32 through the auxiliary oil passage 38, maintaining the same two-wheel drive state as described above, and cornering. Smooth turning without braking phenomena is achieved.

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 oil pressure exceeds the flow capacity of the auxiliary oil 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), causing the front wheels 9 to slip. In this case, it is possible to avoid the situation where the drive torque to the rear wheels 16 is increased and the vehicle cannot 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, 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. 5).

By the way, when acceleration occurs in the vehicle forward and backward in the traveling direction, such as during sudden acceleration or sudden braking, the flow path of the auxiliary oil passage 38 is narrowed depending on the magnitude of this acceleration. Therefore, even if there is a slight difference in rotational speed between the front wheels 9 and the rear wheels 16, the rotor 19 and cam ring portion 20a of the vane pump VP rotate together through pressure oil, resulting in four-wheel drive. Ru. That is, with the above characteristics, as shown by the solid line in FIG. 5, the timing of switching to four-wheel drive becomes earlier, and excellent rapid acceleration performance and sudden braking performance due to the four-wheel drive state are effectively exhibited.

The variable throttle mechanism M shown in the above embodiment detects the acceleration of the vehicle using the spool 40 that moves inertia, but as shown in FIG. Branched into 38b,
One oil passage 38a is provided with a fixed throttle 45, and the other oil passage 38b is provided with a normally open valve operated by a solenoid.
A position switching valve 46 may be provided, and the switching valve 46 may be opened and closed by operating this solenoid based on an output signal of a known acceleration sensor 47 that detects acceleration in the longitudinal direction of the vehicle. In addition, 48 in the figure
is a control circuit provided between the acceleration sensor 47 and the solenoid. Even with this configuration, the auxiliary oil passage 38 is damaged due to acceleration.
is the flow path resistance determined by both oil paths 38a and 38b or the flow path resistance determined only by the oil path 38a.Similarly to the above embodiment, when the acceleration becomes larger than a predetermined value, the flow path of the auxiliary oil path 38 is constricted and early It will be equipped with four-wheel drive. In addition to the above-mentioned means, various means for detecting acceleration can be used, such as one that utilizes changes in the rotational speed of the wheels. Further, in the above embodiment, a balanced vane pump with six suction and discharge ports was used as the hydraulic pump, but an unbalanced vane pump with two suction and discharge ports, other types of hydraulic pumps, such as internal gear pumps, etc. It is possible to use any type of pump such as a trochoid pump, hypocycloid pump, axial or radial plunger pump, which can change the amount of oil discharged depending on the difference in rotational speed. In addition to the relief valves 36 and 37, other known valve mechanisms for regulating the flow of oil discharged from the vane pump VP, such as solenoid valves whose duty is controlled or opened/closed by a computer, can be used.

<Effects of the invention> According to the four-wheel drive device 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 the sudden acceleration performance and sudden braking performance. can.

[Brief explanation of the drawing]

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 graph explaining the operation, and FIG. 6 is a schematic configuration diagram showing another aspect of the variable diaphragm mechanism. 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 an auxiliary oil 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 within 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 four-wheel drive device for a vehicle, comprising: a variable throttle mechanism that detects acceleration in the forward and backward directions of the vehicle and throttles the flow path of the auxiliary oil path as the acceleration increases.