JPH0118417Y2 - - Google Patents

Description

[Detailed explanation of the idea]

a. Field of Industrial Application The present invention relates to four-wheel drive vehicles, and in particular, it is possible to switch between four-wheel drive and two-wheel drive using a hydraulic clutch, and to pump hydraulic fluid by operating the hydraulic clutch pedal or brake pedal. Regarding four-wheel drive vehicles. b. Prior Art In conventional four-wheel drive vehicles that can be switched from four-wheel drive to front-wheel drive (or rear-wheel drive), a dog clutch is disposed inside the transmission, and this dog-clutch connects the rear wheels (or front wheels). ) is connected to one end of the propeller shaft that drives the When the dog clutch is engaged, four-wheel drive (hereinafter referred to as "4WD") is established, and when the dog clutch is disengaged, front-wheel drive or rear-wheel drive (hereinafter referred to as "2WD") is established. By the way, a four-wheel drive vehicle like this is called 4WD.
The following problems have been pointed out when cornering. That is, when cornering, a steering brake is generated due to the difference between the inner and outer wheels of the front and rear wheels, and this brake torque acts on the dog clutch as an excessive force. As a result, it becomes difficult to separate the movable flange of the dog clutch from the fixed flange, and there is a possibility that switching from 4WD to 2WD may not be possible. In order to overcome these problems, the applicant of the present application has proposed a four-wheel drive vehicle in which a hydraulic clutch is disposed in the middle of the propeller shaft. However, in this four-wheel drive vehicle, the oil pump that pumps hydraulic oil to the hydraulic clutch is driven by a propeller shaft, so no oil pressure is generated when the vehicle is stopped or driving at extremely low speeds. For this reason
There were cases where the vehicle could not start in 4WD. In other words, if the hydraulic pressure of the hydraulic clutch is drained and the vehicle is switched to 2WD to eliminate the steering brake phenomenon during cornering, and the vehicle is stopped immediately after that, the hydraulic clutch may not be able to engage due to insufficient hydraulic pressure. It became impossible to start using 4WD. In order to deal with this problem to some extent, it is possible to maintain a constant hydraulic pressure using a combination of a pressure accumulator and a check valve, but as the hydraulic pressure of the hydraulic clutch is repeatedly drained, the pressure of the pressure accumulator may drop. This will not solve the fundamental problem. c. Purpose of the invention The present invention was devised to effectively solve the problems described above, and its purpose is to stop the vehicle immediately after draining the hydraulic pressure of the hydraulic clutch and switching to 2WD. The purpose of the present invention is to provide a four-wheel drive vehicle that can start using 4WD again even when the vehicle is in use. d Structure of the invention The gist of the invention is to transmit the output of the engine located at the front or rear of the vehicle body to the rear wheels or front wheels via a propeller shaft located along the lower surface of the vehicle body. In the four-wheel drive vehicle, (a) a hydraulic clutch disposed at an intermediate portion of the propeller shaft, and (b) a first oil driven by the propeller shaft to pump hydraulic fluid to the hydraulic clutch. a pump; (c) a variable pressure regulating valve disposed in the hydraulic oil pressure feeding path and setting the maximum pressure in the pressure feeding path according to a 2WD or 4WD selection signal; and (d) a clutch pedal or brake. A four-wheel drive vehicle is provided, each comprising a second oil pump that is driven by a pedal and that pumps hydraulic oil to the hydraulic clutch. e Example An example of the present invention will be described below based on the drawings. Figures 1 and 2 schematically show the power transmission system of a four-wheel drive vehicle, in which 1 is a horizontal engine, 2 is a transmission, 3 is a front wheel, and 4 is a horizontally mounted engine. The rear wheel 5 is a final reduction gear. A pair of front wheel drive shafts 6 protrudes from both left and right sides of the transmission 2, and the front wheels 3 are driven by the drive shafts 6. Further, a rear wheel drive shaft 7 protrudes from the rear end of the transmission 2, and this shaft 7 is connected to the final reduction gear 5 by a propeller shaft 8 disposed along the lower surface of the vehicle body. ing. The propeller shaft 8 is composed of a front propeller shaft 8a and a rear propeller shaft 8b, and a disc-type hydraulic clutch 9 is interposed between the two propeller shafts 8a, 8b. When this hydraulic clutch 9 is connected, the driving force of the shaft 7 is transmitted to the final reduction gear 5 via the propeller shafts 8a and 8b, and the rear wheels 4 are driven by the pair of rear wheel drive shafts 10 of the final reduction gear 5. It is becoming more and more common. Note that the first
In the figure and FIG. 2, 20 indicates a universal joint. The hydraulic clutch 9 is attached to the lower surface of the bottom plate 11 of the vehicle body, as shown in FIG. Specifically, a groove 12 for inserting the propeller shaft 8 through the bottom plate 11 is formed along the front-rear direction, and a pair of left and right support plates 13 protruding horizontally are fixed to the edges of the groove 12. There is. On the other hand, the support plate 1 is attached to the housing 14 of the hydraulic clutch 9.
A pair of left and right flange portions 14a extending above 3
An elastic body 15 is provided between the pair of flange portions 14a and the support plate 13 to absorb vibrations, shocks, and the like. In FIG. 3, reference numeral 16 designates cooling fins formed in the housing 14 of the hydraulic clutch 9. In this way, since the hydraulic clutch 9 is interposed in the intermediate portion of the propeller shaft 8, a free space can be formed around the transmission 2, and the degree of freedom in design can be improved. Also hydraulic clutch 9 and transmission 2
Since it is possible to increase the distance between
The flow of cooling air to the hydraulic clutch 9 is not obstructed by the transmission 2 or the like, thereby increasing the cooling effect of the hydraulic clutch 9. The internal structure of the hydraulic clutch 9 is as shown in FIG. In the figure, 21 is an input side disk;
22 is an output side disk, and 23 is a piston. The input side disk 21 is connected to the front propeller shaft 8a, and the output side disk 22 is connected to the rear propeller shaft 8b. When a predetermined hydraulic pressure is applied to the piston 23, the input side disk 21 and the output side disk 22 are pressed against each other, and power is transmitted between the front and rear propeller shafts 8a, 8b. Also within the housing 14 of the hydraulic clutch 9 are:
A first oil pump 24 for driving the piston 23 is provided. The impeller 24a of the first oil pump 24 is fixed to the front propeller shaft 8a, so that the first oil pump 24 is driven only while the vehicle is running. On the other hand, an oil tank 25 is attached to the lower part of the housing 14 of the hydraulic clutch 9, and hydraulic oil exclusively used for the hydraulic clutch 9 is stored in the tank 25. And this hydraulic oil is in the suction pipe 26
The oil is sucked into the first oil pump 24 through the oil pump 24. As described above, in the four-wheel drive vehicle according to the present invention, the exclusive oil tank 25 is attached to the hydraulic clutch 9, so the piping is short, the structure is simple, and the cost of the device can be reduced. A valve unit 28 is housed within the oil tank 25. This valve unit 28 is composed of a pressure regulating valve 29, a variable pressure regulating valve 30, and check valves 38 and 39, as shown in FIG. It has come to be controlled by For details, see Oil Pump 2
A check valve 38 is provided in the middle of a discharge pipe 37 extending from the piston cylinder 36 to the piston cylinder 36, and a pressure regulating valve 29 is connected to the upstream side of the check valve 38. When the rotational speed of the first oil pump 24 increases and its discharge pressure exceeds a predetermined pressure, a part of the hydraulic oil is returned to the oil tank 25 by the action of the pressure regulating valve 29, and the hydraulic oil is supplied. Designed to maintain constant pressure. Further, a variable pressure regulating valve 3 is provided on the downstream side of the check valve 38.
0 and a check valve 39 are connected to each other, and a second oil pump 40 is further connected to the check valve 39. The variable pressure regulating valve 30 is controlled by a predetermined external signal.
This external signal includes, for example, a constant 2WD signal by manual operation, a constant 4WD signal, and a part-time signal automatically generated by a steering sensor.
It includes a 4WD signal, and the variable pressure regulating valve 30 is configured to operate as shown in the table below in response to these signals.

[2WD driving]

In this case, the 2WD signal by manual operation is transmitted to the variable pressure regulating valve 30 as an external signal,
This signal causes the variable pressure regulating valve 30 to open as the set pressure decreases. When the variable pressure regulating valve 30 opens, the pressure in the piston cylinder 36 decreases,
The piston 23 of the hydraulic clutch 9 is indicated by the arrow a in FIG.
direction, and the pressed state between the input side disk 21 and the output side disk 22 is released. As a result,
Power transmission from the front propeller shaft 8a to the rear propeller shaft 8b is cut off, and 2WD driving is always performed using the front wheels 3. [4WD driving] In this case, a 4WD signal by manual operation is transmitted to the variable pressure regulating valve 30 as an external signal,
This signal causes the variable pressure regulating valve 30 to close due to an increase in the set pressure. When the variable pressure regulating valve 30 is closed, the pressure in the piston cylinder 36 increases,
This pressure causes the piston 23 of the hydraulic clutch 9 to
moves in the direction of arrow b in FIG. 5, and the input side disk 21 and the output side disk 22 are pressed together. As a result, power is transmitted from the front propeller shaft 8a to the rear propeller shaft 8b, and the front and rear wheels 3, 4
4WD driving is done. [Cornering] When cornering in 4WD, steering torque is generated between the front and rear propeller shafts 8a, 8b due to the difference in rotation between the front and rear wheels 3, 4.
This steering brake phenomenon is detected by a steering sensor or the like, and this detection signal is transmitted to the variable pressure regulating valve 30 as an external signal, and this signal causes the variable pressure regulating valve 30 to temporarily open due to a decrease in the set pressure. . When the variable pressure regulating valve 30 is temporarily opened, power transmission from the front propeller shaft 8a to the rear propeller shaft 8b is cut off, and 2WD running using the front wheels 3 is temporarily performed, similar to the above-mentioned 2WD running. Therefore, it is possible to eliminate steering torque and perform smooth cornering. [When stopping immediately after cornering]
4WD start] In this case, the pressure in the piston cylinder 36 of the hydraulic clutch 9 remains reduced due to the opening of the variable pressure regulating valve 30 during cornering.
Also, since propeller shaft 8 is stopped, the first
The oil pump 24 is also stopped, and the hydraulic clutch 9 cannot be connected in this state.
Unable to start in 4WD. However, since the four-wheel drive vehicle according to the present invention is equipped with the second oil pump 40, 4WD starting is possible by driving this second oil pump 40. That is, when the clutch pedal 41 or the brake pedal 42 is depressed several times, hydraulic oil is forced into the piston cylinder 36, and this pressure causes the piston 23 of the hydraulic clutch 9 to move in the direction of arrow b in FIG. The input side disk 21 and the output side disk 22 are pressed together. As a result, the front propeller shaft 8a
Power can be transmitted from the rear propeller shaft 8b to the rear propeller shaft 8b, and a 4WD start is performed by connecting the start clutch in the transmission 2. Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment and can be modified in various ways. For example, in the above embodiment, the torque capacity of the hydraulic clutch 36 is switched between 0% and 100% by the variable pressure regulating valve 30.
If the set pressure of the variable pressure regulating valve 30 is made to change continuously in response to the magnitude of steering torque, etc., the torque capacity of the hydraulic clutch 9 can be reduced to zero.
Can be changed continuously from % to 100%,
It becomes possible to use a four-wheel drive vehicle as a so-called part-time and full-time 4WD. f. Effects of the invention As mentioned above, this invention enables the hydraulic oil to be pumped to the hydraulic clutch by the second oil pump driven by the clutch pedal or the brake pedal, so it is possible to stop the vehicle immediately after cornering. Even if the pressure in the piston cylinder of the hydraulic clutch remains low, the second oil pump is driven by operating the clutch pedal or the brake pedal, thereby pumping hydraulic oil to the piston cylinder. Since the hydraulic clutch can be engaged, it is possible to start again in 4WD. Further, the torque capacity of the hydraulic clutch is controlled to increase or decrease by increasing or decreasing the set pressure of a variable pressure regulating valve disposed in the hydraulic oil pressure feeding path to the hydraulic clutch using a predetermined external signal.
2WD driving and 4WD driving can be used selectively as needed, and if a detection signal from a steering sensor, etc. is used as the above-mentioned predetermined external signal, automatic control will be applied when a steering brake phenomenon occurs due to cornering. The vehicle can be switched to 2WD mode for smooth cornering. In addition, the torque capacity of the above hydraulic clutch should be increased from 0% to
It can also be changed continuously up to 100%, making it possible to use a four-wheel drive vehicle as a so-called part-time and full-time 4WD.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention, in which Fig. 1 is a schematic plan view showing the power transmission system of a four-wheel drive vehicle, Fig. 2 is a side view of Fig. 1, and Fig. 3 is a hydraulic diagram. FIG. 4 is a schematic diagram of the construction of the hydraulic clutch, and FIG. 5 is a hydraulic circuit diagram of a control means for controlling the torque capacity of the hydraulic clutch. 1...Engine, 2...Transmission,
3...Front wheel, 4...Rear wheel, 5...Final reduction gear, 8...
...Propeller shaft, 8a...Front propeller shaft, 8b...Rear propeller shaft, 9...Hydraulic clutch, 15...Elastic body, 16...Cooling fin, 21...Input side disk, 22...Output side disk , 23... Piston, 24... First oil pump, 25... Oil tank, 26... Suction pipe, 28... Valve unit, 29... Pressure regulating valve, 30... Variable pressure regulating valve (control means ), 36
...Piston cylinder, 37...Discharge pipe, 38,
39...Check valve, 40...Second oil pump, 41...Clutch pedal, 42...Brake pedal, 44...Clutch, 45...Brake.

Claims (1)

[Claims for Utility Model Registration] The output of an engine disposed at the front or rear of the vehicle body is transmitted to the rear wheels or front wheels via a propeller shaft disposed along the underside of the vehicle body. In a four-wheel drive vehicle, (a) a hydraulic clutch disposed at an intermediate portion of the propeller shaft; (b) a first hydraulic clutch disposed on the engine side of the propeller shaft for pumping hydraulic fluid to the hydraulic clutch;
an oil pump; (c) a variable pressure regulating valve disposed in the pressure-feeding path for the hydraulic oil and setting the maximum pressure in the pressure-feeding path according to a 2WD or 4WD selection signal; (d) a clutch pedal. or a second oil pump that is driven by a brake pedal and pumps hydraulic oil to the hydraulic clutch.