JPH03288022A - Drive coupling device for four wheel drive - Google Patents

Abstract

PURPOSE:To promote temperature fall of working fluid to realize quick return to normal conductive character by providing a constraining means which is installed on an engaging piston, deformed in response to that when the working fluid reaches a second temperature lower than a first temperature which constrains returning action produced on the engaging piston, following release of receiving pressure. CONSTITUTION:When working fluid in a hydraulic pump 3 rises in temperature and reaches to a first temperature, an energizing means 70 is deformed in responding thereto, a control spool 7 in a first oil chamber 5 formed to a casing moves, generated oil pressure of the hydraulic pump is induced into a second oil chamber 6 formed to the casing as well, an engaging piston 8 in the second oil chamber is slided by reception of this oil pressure to engage with a part of a rotor, relative rotation between the rotor and the casing is suppressed, and the transmission of driving force between both is ensured, while the temperature fall of the working fluid is promoted. When the temperature of the working fluid becomes lower than a second temperature by this promotion of temperature fall, the engaging piston is returned with release of deformation by a constraining means 9, and transmission of driving force is resumed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention transmits driving force from one of the front and rear wheels to the other using the hydraulic pressure generated by a hydraulic pump configured between the two wheels. The present invention relates to a drive coupling device for four-wheel drive.

[Conventional technology]

Drives by transmitting the engine's driving force to both the front and rear wheels 4
Wheel drive vehicles have been in the spotlight as vehicles that can realize stable driving regardless of road conditions, natural conditions such as weather, and driving conditions. Recent four-wheel drive vehicles are equipped with a drive coupling device that has the function of distributing driving force to both wheels according to the difference in rotational speed between the front and rear wheels, so that four-wheel drive can be achieved virtually all the time. Full-time four-wheel drive vehicles have become mainstream, and one type of drive coupling device uses hydraulic pressure generated by a hydraulic pump. This is achieved by housing a rotor designed to rotate in conjunction with one of the front and rear wheels in a casing designed to rotate in conjunction with the other, and then using a hydraulic pump (e.g. vane pump) to create a rotor that rotates in conjunction with the other wheel. A relative rotation corresponding to the rotational speed is generated between the rotor and the casing, and hydraulic pressure is generated inside the hydraulic pump. The hydraulic pressure generated at this time corresponds to the magnitude of the relative rotation and acts between the rotor and the casing to suppress this relative rotation, so this hydraulic pressure is used as a medium to move from one of the front and rear wheels to the other. A driving force corresponding to the rotational speed difference between the two wheels is transmitted, and a desired four-wheel drive state is realized.

[Problem to be solved by the invention]

Now, in this drive coupling device, since not only the rotor but also the casing rotates, it is difficult to supply hydraulic oil for the hydraulic pump from the outside, and there is a gap between the casing and the cylindrical body fitted on the outside of the casing. An oil tank is formed which rotates integrally with the casing, and the oil sealed in the oil tank is circulated and used as hydraulic oil for the hydraulic pump. However, since the internal volume of the oil tank is limited due to the miniaturization of the entire device, for example, when driving on mountain roads or snowy roads, a state where a large rotational speed difference occurs between the front and rear wheels may occur for a long period of time. Under such conditions that continue for a long period of time, the temperature of the hydraulic oil inevitably rises, resulting in a problem of volumetric expansion and viscosity reduction of the hydraulic oil.

The former problem, that is, the volumetric expansion of hydraulic oil, can be solved by U.S. Pat.
As disclosed in No. 250662, etc., the volumetric fat is absorbed by deformation of a diaphragm disposed inside the oil tank or movement of a piston member disposed inside the oil tank or a part of the hydraulic pump. Although various effective proposals have been made and have already been put into practical use, such as providing a volumetric fat absorption mechanism that increases the volumetric fat absorption, it is impossible to directly solve the latter problem, that is, the decrease in viscosity of hydraulic fluid. As the viscosity decreases, the pressure characteristics of the hydraulic pump deteriorate, resulting in a problem in that the transmission characteristics deteriorate during driving.

As mentioned above, the temperature of the hydraulic fluid increases when a particularly strong four-wheel drive condition is required, such as when driving on mountain roads or snowy roads, and it is necessary to eliminate the decrease in transmission characteristics caused by the decrease in viscosity. is important. For example, if this deterioration of transmission characteristics is left untreated, snow accumulates.

If one of the front or rear wheels becomes idling due to running into a sand puddle, etc. (a so-called stuck condition), sufficient driving force is not transmitted to the other wheel that maintains grip, resulting in a stuck condition. It becomes difficult to escape quickly. In addition, the continuation of the deterioration of characteristics will cause the temperature of the hydraulic oil to rise further,
In addition to causing new problems such as the occurrence of cavitation on the suction side of the hydraulic pump, which inhibits the normal operation of the drive coupling device, the volumetric expansion of the hydraulic fluid due to temperature rise exceeds the absorption limit of the volume change absorption mechanism. There was even a risk that the hydraulic oil sealed in the oil tank might leak to the outside.

The present invention has been made in view of the above circumstances, and is capable of compensating for the decrease in transmission characteristics when the temperature of the hydraulic oil increases, thereby making it possible to maintain a four-wheel drive state, and also to reduce the temperature of the hydraulic oil. It is an object of the present invention to provide a four-wheel drive drive coupling device that promotes temperature reduction and quickly returns to normal transmission characteristics.

[Means to solve the problem]

The four-wheel drive drive coupling device according to the present invention includes a hydraulic pump in which a rotor that rotates in conjunction with one of the front and rear wheels is housed in a casing that rotates in conjunction with the other, and hydraulic oil that circulates within the hydraulic pump. In a four-wheel drive drive coupling device that connects front and rear wheels using hydraulic pressure generated in response to relative rotation between the rotor and the casing, the four-wheel drive coupling device is formed on a part of the casing; A first oil chamber into which the hydraulic pressure generated by the hydraulic pump is introduced and a second oil chamber arranged in parallel thereto are arranged within the first oil chamber, and movement within the oil chamber causes the first oil chamber to flow into the first oil chamber. a control spool that communicates or cuts off communication between the second oil chambers; and a control spool that is attached to the control spool and deforms in response to the reaching of the first temperature of the hydraulic oil, so that the communication side of the control spool is connected to the communication side of the control spool. a biasing means for biasing movement; and a biasing means for biasing the movement;
an engagement piston that is disposed in an oil chamber, receives hydraulic pressure introduced from the first oil chamber and slides, and engages a portion of the rotor to suppress the relative rotation; and the engagement piston. is attached to the hydraulic fluid and deforms in response to the temperature when the hydraulic fluid reaches a second temperature lower than the first temperature, and causes a return movement that occurs in the engagement piston as the received pressure is released. It is characterized by comprising a restraining means for restraining.

[Effect]

In the present invention, the temperature of the hydraulic oil of the hydraulic pump rises and the first
When the temperature reaches , the biasing means is deformed in response to this, and the control spool in the first oil chamber formed in the casing moves, and the hydraulic pump is transferred to the second oil chamber also formed in the casing. The generated hydraulic pressure is introduced, and the engagement piston in the second oil chamber slides and engages a part of the rotor due to the received pressure of this hydraulic pressure, suppressing the relative rotation between the rotor and the casing, and creating a gap between the two. It secures the transmitted driving force and promotes cooling of the hydraulic oil. When the temperature of the hydraulic oil falls below the first temperature due to the acceleration of this temperature drop, the control spool moves in the opposite direction due to the deformation of the biasing means being released, and the first oil chamber and the second oil chamber are connected to each other. When the communication is cut off and the temperature of the hydraulic oil falls below the second temperature, the engagement piston returns to its original position by releasing the deformation of the restraint means, and the release of the engagement causes the drive to be driven using the pressure generated by the hydraulic pump as a medium. Force transmission is resumed.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on drawings showing embodiments thereof. FIG. 1 is a longitudinal sectional view of a four-wheel drive drive coupling device (hereinafter referred to as the device of the present invention) according to the present invention.

The device of the present invention has an input shaft 1 that rotates in conjunction with one of the front and rear wheels.
and the output shaft 2 which rotates in conjunction with the other, both shafts 1.2
A hydraulic pump is constructed that generates oil pressure according to the rotational speed difference between the front and rear wheels, that is, the rotational speed difference between the front and rear wheels, and under normal conditions, the driving force is transmitted from the human power shaft 1 to the output shaft 2 using the generated oil pressure as a medium. As the hydraulic pump, for example, a vane pump 3 as shown in the figure is used.

This vane pump 3 has a rotor connected to an output shaft 2 as described below, housed inside a casing connected to an input shaft 1 as described later, so as to be able to rotate coaxially therewith. The casing of the vane pump 3 has a thick-walled hollow disc-shaped cam ring 31 on both sides of a short cylindrical cam ring 31 having a circular outer periphery and an inner periphery formed by distributing a plurality of recesses evenly distributed around the circular periphery. A pressure plate 32 having a hollow shape and a side plate 33 having a hollow disc shape are respectively positioned coaxially, and a plurality of screws ( These are integrally connected by fixing bolts 34, 34, . . . (only one is shown). The input shaft 1 is indicated by 2 in the figure.
As shown by the dotted chain line, the side plate 33 is hollow, and for connection with the human power shaft l, the outer surface of the side plate 33 has a short cylinder having a large number of engagement teeth 36, 36, . . . on its outer periphery. A shaped connecting portion 35 is coaxially protruded. The connection is made by fitting one end of the input shaft 1 onto the connection part 35, and connecting the engagement teeth 10, 10, . . . formed inside the end with the engagement teeth 36, 36... The casing of the vane pump 3 rotates about its axis in conjunction with the rotation of the output shaft 2.

On the other hand, the rotor of the vane pump 3 includes a short cylindrical rotor body 30 having approximately the same length as the cam ring 31, and a hollow rotor shaft 4 that is a rotation axis of the rotor body 30. Rotor body 3
As is well known, the coil spring 3 includes a plurality of grooves having a predetermined depth in the radial direction and equally spaced in the circumferential direction, and a rectangular flat plate-shaped vane 30a housed in each of these grooves so as to be able to move forward and backward.
It has a structure in which it is biased outward in the radial direction at 0b,
It is stored inside the cam ring 31. The rotor shaft 4 is
It is fitted into the hollow portions of the pressure plate 32 and the side plate 33 and is supported coaxially therewith.
The rotor body 30 is spline-coupled between both supporting positions. As a result, the rotor main body 30 is located inside the cam ring 31 coaxially therewith, and is surrounded on both sides by a pressure plate 32 and a side plate 33 at a position corresponding to the recess on the inner periphery of the cam ring 31. It forms multiple pump chambers.

The output shaft 2 shown by the two-dot chain line in the figure is fitted into the hollow portion of the rotor shaft 4, and both are coaxially connected by spline. Therefore, the rotor body 30 rotates in conjunction with the rotation of the output shaft 2, and there is a gap between the input shaft 1 and the output shaft between the cam ring 31 and the rotor body 30, that is, between the casing of the vane pump 3 and the rotor. 2, that is, between the front and rear wheels, a relative rotation occurs corresponding to the rotational speed difference between the front and rear wheels, and hydraulic pressure is generated in the pump chamber as described below.

A thin-walled cylindrical body 37 is fitted on the outside of the casing in such a manner that it almost entirely surrounds the casing, and the vane pump 3
The hydraulic oil is sealed in an oil tank T formed in an annular shape between the inner periphery of the cylindrical body 37 and the outer periphery of the casing. The pressure plate 32 includes a pair of check valves 41 and 42 that are formed radially inward with one end open in the oil tank T and allow flow only in the same direction.
A plurality of (only one shown) oil passages 40° 40 . . . are formed in parallel along the middle of the oil passages. These oil passages 40
, 40... are communicated with the pump chamber between the pair of check valves 41, 42, and the bottoms of the storage grooves of the vanes 30a, 30a... are communicated at their respective tips, and the It functions as a suction oil passage or a discharge oil passage depending on the direction of relative rotation between the casing and the rotor. Further, the hollow portion of the pressure plate 32 passes through the pressure plate 32 in the radial direction, and is communicated with the oil tank T through a return oil passage (not shown) that is provided with a throttling means in the middle.

As a result, a rotational speed difference occurs between the front and rear wheels, and a relative rotation occurs between the rotor and the casing of the vane pump 3, that is, between the rotor body 30 and the cam ring 31 at a speed corresponding to this rotational speed difference. When this occurs, hydraulic oil flows into each pump chamber formed between the two from the oil tank T via the oil passages 40 communicating with each other on the upstream side in the relative rotation direction, and
This inflowing oil is sealed between adjacent vanes 30a, 30a, rotated by the rotation of the rotor main body 30, and pressurized, and the oil communicates with each pump chamber on the downstream side in the relative rotation direction. is discharged into the oil passage 40, and the oil passage 40
The flow flows radially inward inside the vanes 30a, 30a...
The oil is introduced into the bottom of the storage groove, and is further refluxed to the oil tank T via the reflux oil path. The oil introduced into the bottom of the storage groove is applied to each vane 30a by the biasing force of the coil spring 30b.
, 30a, . Due to this circulation of the hydraulic oil, there is a flow resistance inside each pump chamber in response to the magnitude of the relative rotation, against the flow path resistance in this circulation path, mainly the flow path resistance in the throttling means of the return oil path. Corresponding hydraulic pressure is generated and acts between the rotor body 30 and the cam ring 31 to prevent relative rotation between the two. Through this hydraulic pressure, the input shaft 1 connected to the latter is connected to the output shaft 2 connected to the former. A driving force corresponding to the difference in rotational speed between the front and rear wheels is transmitted to the front and rear wheels.

In this way, the circulation of the hydraulic oil between the oil tank T and each pump chamber is performed by repeatedly increasing and decreasing the pressure, so the difference in rotational speed between the front and rear wheels is large, and the difference between the rotor body 30 and the cam ring 3 If a state in which a large relative rotation occurs continuously between As a result, the transmission characteristics of the driving force performed as described above deteriorate. In the device of the present invention, compensating means for compensating for this reduction in transmission characteristics is configured in a circumferential cross section of the pressure plate 32 that is different from that in FIG. 1.

FIGS. 2 and 3 are enlarged sectional views showing the structure of this compensating means, which is a feature of the apparatus of the present invention. The compensation means includes a first oil chamber 5 and a second oil chamber formed in the pressure plate 32.
It comprises an oil chamber 6, and a control spool 7 and an engagement piston 8 disposed in the oil chambers 5 and 6, respectively. As shown in the figure, the first oil chamber 5 is formed by liquid-tightly closing the open end of a circular hole formed with an appropriate depth in the radial direction from the outer periphery of the pressure plate 32 by screwing a screw cap 50. The chamber has a circular cross section, and the vanes 30a, 30a, . . .
The hydraulic pressure generated by the vane pump 3 is introduced into the first oil chamber 5 through the pressure guiding hole 51. The control spool 7 is a cylindrical member having an outer diameter equal to the inner diameter of the first oil chamber 5 and is slidably fitted into the oil chamber 5, and is located on the inner back side of the first oil chamber 5. A coil spring 70 and a coil spring 71 are sandwiched between the end face and the end face of the screw cap 50, and both springs 70.
71 slides in the axial direction of the first oil chamber 5.

One coil spring 71 on the screw cap 50 side is made of ordinary spring steel and expands and contracts due to external force acting on it, while the other coil spring 70 contracts and contracts at room temperature as shown in FIG. It is a shape memory alloy spring that deforms and expands as shown in FIG. 3 when it reaches a predetermined temperature. Therefore, the control spool 7 moves in response to the temperature of the hydraulic oil introduced into the first oil chamber 5, and is biased by the coil spring 71 when the temperature of the hydraulic oil is below the predetermined temperature. As shown in FIG. As shown in the figure, it is displaced toward the screw cap 50 side. Temperature at which the coil spring 70 deforms (first temperature)
T is set at a temperature at which a decrease in the pressure characteristics of the vane pump 3 due to a decrease in the viscosity of the hydraulic oil becomes a problem, for example, around 150°C.
This is achieved by making the shape memory alloy.

On one side of the first oil chamber 5 configured as described above, a large diameter portion 3 extending radially through the pressure plate 32 is provided.
8a and a short small-diameter portion 38b inside, the second oil chamber 6 fits the engagement piston 8 into the circular hole 38, and the second oil chamber 6 has a small-diameter portion 38b inside thereof. The opening end is liquid-tightly closed by screwing a screw cap 60 , and it is formed between the screw cap 60 and the engagement piston 8 in parallel with the first oil chamber 5 . The first oil chamber 5 and the second oil chamber 6 communicate with each other through a communication hole 52, and the open end of the communication hole 52 on the first oil chamber 5 side The control spool 7 is closed. On the outer periphery of the control spool 7, a narrow annular groove 72 and a wide annular groove 73 are arranged in parallel at an appropriate distance apart in the axial direction, and the control spool 7 is located on the inner back side of the first oil chamber 5. , the opening end of the communication hole 52 into the oil chamber 5 coincides with the annular groove 72 , and conversely, when the communication hole 52 is located on the side of the lid 50 , the opening end of the communication hole 52 coincides with the annular groove 73 . None to match each other. Annular: a7
2 is connected to the inside of the control spool 7, whereas
The annular groove 73 is not communicated with the inside of the control spool 7, and when the control spool 7 is in the former sliding position, the second oil chamber 6 communicates with the communication hole 52 and the annular groove 72 as shown in FIG. The internal pressure of the core oil chamber 5, that is, the hydraulic pressure generated by the vane pump 3 is introduced into the second oil chamber 6, and when the control spool 7 is in the latter sliding position, Second
The oil chamber 6 has a communication hole 52 and an annular groove 73 as shown in FIG.
, and communicates with the oil tank T formed on the outside of the pressure plate 32 as described above through the communication hole 53 arranged in parallel on the radially outer side of the communication hole 52. The internal pressure of tank T is introduced.

The engagement piston 8 has a short large diameter cylindrical part 8a that fits in the large diameter part 38a, and a long small diameter cylindrical part 8b that fits in the small diameter part 38b, and a smaller diameter cylindrical part 8b on both sides of the short large diameter cylindrical part 8a that fits in the large diameter part 38a. Short cylindrical stopper portions 8c are coaxially connected to each other, and the tip of the small diameter cylindrical portion 8b is opposed to the outer peripheral surface of the rotor shaft 4 supported inside the pressure plate 32. be. Furthermore, the engagement piston 8 is biased in opposite directions in the radial direction of the pressure plate 32 by the internal pressure of the second oil chamber 6 and the spring force of a coil spring 80 interposed between the circular hole 38. There is no sliding movement depending on the coverage between the two. The second oil chamber 6 is in communication with the oil tank T, and when the internal pressure of the oil chamber 6 is low, the engagement piston 8 is pressed radially outward by the spring force of the coil spring 80. As shown in FIG. 2, the end face of the stopper portion 8c is in contact with the end face of the screw M2O, but the second oil chamber 6 is in communication with the first oil chamber 5; When the hydraulic pressure generated by the vane pump 3 is introduced, the engagement piston 8 is pressed by this introduced hydraulic pressure, and
It slides radially inward against the biasing force of the coil spring 80, and at this time, the tip of the small diameter cylindrical portion 8b protrudes into the hollow portion of the pressure plate 32, and the fitting formed on the outer peripheral surface of the rotor shaft 4 It fits into the matching hole 4a as shown in FIG. Thereby, the pressure plate 32 and the rotor shaft 4, in other words, the casing of the vane pump 3 and the rotor are directly connected via the engagement piston 8.

Now, this engaging piston 8 is attached with a restraining means 9 for restraining the sliding movement that occurs as described above.

The restraining means 9 shown in FIGS. 2 and 3 has a large diameter cylindrical portion 8a.
The O-ring 9b is wound around the outside of the deformable ring 9a and comes into elastic contact with the inner periphery of the large diameter portion 38a of the circular hole 38. FIG. 4 is a plan view for explaining the operation of the restraint means 9. As shown in this figure, the deformable ring 9a is a shape memory alloy ring having an annular shape with a notched portion. The notch is tightly wrapped around the bottom of the annular groove formed in the cylindrical portion 8a, but as it reaches a predetermined temperature, it deforms to increase the width and diameter of the notch as shown on the right side. There is nothing like that. As a result of this deformation, the O-ring 9b is pushed outward to the outside of the large-diameter cylindrical portion 8a, but this overhang is restrained by the inner periphery of the large-diameter portion 38a of the circular hole 38, and the deformed ring 9
If the aforementioned deformation occurs in the O-ring 9b, the large diameter portion 3
The engagement piston 8 is strongly pressed against the inner periphery of the engagement piston 8a, and the above-mentioned sliding movement of the engagement piston 8 is restricted due to the sliding resistance between the two. The temperature at which the deformation ring 9a is deformed, that is, the temperature (second temperature) at which the restraint operation of the restraint means 9 is caused, is the temperature at which the shape memory alloy coil spring 71 disposed inside the first oil chamber 5 is deformed. , lower than the first temperature T1 at which the control spool 7 slides outward in the radial direction, and at which a decrease in the pressure characteristics of the vane pump 3 due to a decrease in the viscosity of the hydraulic oil hardly becomes a problem, for example, around 80 degrees Celsius. It is set. This is achieved by making the deformable ring 9a made of a Ni-Ti type shape memory alloy.

Furthermore, the restraint force generated by the restraint means 9 is determined by the shape setting of the deformation ring 9a after deformation and the selection of the material of the O-ring 9b, etc. The restraint force generated by the restraint means 9 is determined by the radially inward force generated on the engagement piston 8 due to the internal pressure of the second oil chamber 6. Sliding, that is, sliding in the direction in which the fitting occurs with the fitting hole 4a is not restricted, but sliding outward in the radial direction caused by the spring force of the coil spring 80, that is, return operation from the fitted state. The size is set to restrict only the

In the device of the present invention having the above configuration, as described above, the temperature of the hydraulic oil increases due to the circulation between each pump chamber of the vane pump 3 and the oil tank T, and exceeds the first temperature T. In response to the temperature of the hydraulic oil introduced into the oil chamber 5, the coil spring 70 made of a shape memory alloy expands, and the control spool 7 is displaced toward the screw cap 50 as shown in FIG.

As a result of this displacement, the first oil chamber 5 and the second oil chamber 6 are communicated with each other through the communication hole 52, and as a result, the hydraulic pressure generated by the vane pump 3 is introduced into the second oil chamber 6. The engagement piston 8, which is arranged at The pressure plate 32 and the rotor shaft 4, that is, the casing of the vane pump 3 and the rotor are directly connected.

This direct connection ensures the transmission of sufficient driving force from the input shaft 1 to the output shaft 2, and also completely suppresses the relative rotation between the casing and the rotor, resulting in activation due to the stoppage of circulation. The temperature of the oil is accelerated. 2nd oil chamber 6
, even before communicating with the first oil chamber 5, the communication hole 53
Low-pressure hydraulic oil is introduced into the oil tank through the communication hole 52, and when this hydraulic oil reaches the second temperature T2, which is lower than the first temperature T1, the temperature is The sliding movement of the engaging piston 8 is restrained due to the deformation of the deformable ring 9a made of shape memory alloy, but as mentioned above, this restraining force is caused by the hydraulic pressure introduced from the first oil chamber 5. It does not have a size that can restrict the sliding movement that occurs in the engagement piston 8 due to the received pressure, and the casing and rotor can be directly connected without any problem.

Now, as the temperature of the hydraulic oil decreases due to the direct connection, the temperature of the hydraulic oil becomes lower than the first temperature T1, the coil spring 70 contracts, and the spring force of the other coil spring 71 causes the control spool 7 to move to the first temperature T1. As a result of the displacement to the bottom side of the oil chamber 5, the second oil chamber 6 is communicated with the oil tank T, and the internal pressure of the core oil chamber 6 is reduced. At this time, the engagement piston 8 is biased radially outward by the spring force of the coil spring 80, but while the temperature of the hydraulic oil exceeds the second temperature T2, the restraining means 9 exerts a restraining force. This restraining force is generated between the casing of the vane pump 3 and the rotor via the engagement piston 8 because it has a magnitude sufficient to resist the spring force of the coil spring 80. The directly connected state is maintained as it is, and the temperature of the hydraulic fluid is further reduced. Then, as the temperature of the hydraulic oil falls to below the second temperature T2, the deformable ring 9a returns to its original state (the state shown on the left side of FIG. 4), and the restraining force of the restraining means 9 is removed. , the engagement piston 8 slides radially outward and engages the fitting hole 4.
Due to the separation of the small diameter cylindrical portion 8b from a, the vane pump 3
between the casing and the rotor, that is, the input shaft 1 and the output shaft 2
The direct connection between the vane pump 3 and the vane pump 3 is released, and thereafter the driving force is transmitted between the two through the hydraulic pressure generated in each pump chamber of the vane pump 3.

As described above, in the device of the present invention, the temperature of the hydraulic oil circulating within the vane pump 3 is the first temperature T.

As soon as the casing and rotor of the vane pump 3 are engaged with each other via the engagement piston 8, the pressure characteristics of the vane pump 3 decrease as the oil temperature increases, resulting in a decrease in the transmission characteristics from the input shaft 1 to the output shaft 2. Even if this occurs,
This reduction is compensated for by the engagement. Further, in this engaged state, the temperature of the hydraulic oil reaches the second level due to the operation of the restraining means 9.
Since the temperature of the hydraulic oil is maintained until the temperature drops to the temperature T2 of The temperature can be quickly lowered to T2, and the normal transmission characteristics can be quickly restored using the hydraulic pressure generated by the vane pump 3 as a medium.

FIGS. 5 and 6 are enlarged sectional views of main parts showing other embodiments of the apparatus of the present invention. In FIG. 5, the engagement piston 8
A friction plate 8d is fixed to the tip of the small-diameter cylindrical portion 8a, and a friction plate 4b is provided around the entire outer circumference of the rotor shaft 4 that is aligned with this fixed position, so that the engagement piston 8 slides inward in the radial direction. The friction plate 8d is pressed against the friction plate 4b by motion, and the engagement state between the casing and the rotor is obtained by the frictional force generated between the two. Also, in Figure 6, the first
Similar to the coil spring 70 that biases the control spool 7 in the oil chamber 5, a shape memory alloy coil spring 9C that biases the engagement piston 8 radially inward is provided, and the engagement is caused by deformation of the coil spring 9c. The structure is such that the returning movement of the mating piston 8 is restricted. In this case, the O-ring 8b wound around the large-diameter cylindrical portion 8a only functions as a means for sealing the second oil chamber 6.

〔effect〕

As described in detail above, in the device of the present invention, when the temperature of the hydraulic oil of the hydraulic pump rises to reach the first temperature, the control spool in the first oil chamber moves in response to this, and the control spool moves in the second oil chamber. The hydraulic pressure generated by the hydraulic pump is introduced, and the engagement piston in the second oil chamber slides due to the received pressure of this hydraulic pressure, so that an engaged state is obtained between the casing of the hydraulic pump and the rotor, and the relationship between the two is established. A sufficient transmission driving force can be ensured, and a decrease in transmission characteristics caused by a decrease in the pressure characteristics of the hydraulic pump due to an increase in the temperature of the hydraulic oil can be reliably compensated for. Further, the engagement suppresses the relative rotation between the casing and the rotor, stopping the circulation of the hydraulic oil, and promoting the temperature drop of the hydraulic oil, which is restrained until the temperature drops below the second temperature. As a result of the movement of the means restricting the return movement of the engagement piston,
The present invention has excellent effects, such as maintaining the engaged state and quickly returning to normal transmission characteristics using the pressure generated by the hydraulic pump.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing the overall configuration of the device of the present invention, FIGS. 2 and 3 are enlarged sectional views showing an embodiment of the characteristic parts of the device of the present invention, and FIG. 4 is the return operation of the engaging piston. 5 and 6 are enlarged sectional views showing other embodiments of the characteristic parts of the device of the present invention. 1... Human power shaft 2... Output shaft 3... Vane pump 4... Rotor shaft 5... First oil chamber
6...Second oil chamber 7...Control control spool 8
...Engaging piston 9...Restraint means 30...
・Rotor body 31...Cam ring 32...Pressure plate 33...Side plate T...
Oil tank patent applicant Koyo Seiko Co., Ltd.

Claims (1)

[Claims] 1. A hydraulic pump is constructed by housing a rotor that rotates in conjunction with one of the front and rear wheels in a casing that rotates in conjunction with the other;
In a four-wheel drive drive coupling device that connects front and rear wheels using hydraulic oil circulating in the hydraulic pump and hydraulic pressure generated in response to relative rotation between the rotor and the casing, one of the casings is connected to the front and rear wheels. a first oil chamber, into which the hydraulic pressure generated by the hydraulic pump is introduced, and a second oil chamber installed in parallel with the first oil chamber; a control spool attached to the control spool that communicates or cuts off communication between the first and second oil chambers by the movement of the hydraulic fluid; a biasing means for biasing the movement of the spool toward the communication side; and a biasing means disposed in the second oil chamber, which slides when receiving hydraulic pressure introduced from the first oil chamber, and is configured to move a portion of the rotor. an engagement piston that is attached to the engagement piston to engage with the hydraulic fluid to suppress the relative rotation; A drive coupling device for four-wheel drive, comprising a restraining means for deforming and restraining a return movement occurring in the engagement piston upon release of the received pressure.