JP2936163B2 - Power transmission device for four-wheel drive vehicle - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power transmission device for a four-wheel drive vehicle which is configured to be able to drive a front wheel and a rear wheel by a common engine.

[0002]

2. Description of the Related Art As one type of power transmission device for a four-wheel drive vehicle, a front wheel axle is directly connected to an engine, and a rear wheel axle is connected to the front wheel axle via a hydraulic clutch. A pump connects the hydraulic clutch to the hydraulic oil chamber of the hydraulic clutch and supplies the discharge oil generated according to the rotational speed difference between the two axles, thereby achieving the drive connection between the front wheel and the rear wheel. Things are known. In such a power transmission device, a device for lubricating a hydraulic clutch using discharge oil of a hydraulic pump has already been proposed by the present applicant (see Japanese Utility Model Laid-Open No. 4-41126). In this type, when there is a rotation speed difference between the front and rear wheels and the discharge oil of the hydraulic pump is supplied to the operating hydraulic chamber of the hydraulic clutch, a part of the discharge oil is lubricated through an orifice or a relief valve. The hydraulic clutch is lubricated by guiding the hydraulic clutch to a lubricating portion of the hydraulic clutch.

[0003]

By the way, in the above conventional apparatus, when the hydraulic oil is supplied to the working hydraulic chamber and the hydraulic clutch is slid and engaged, the heat generated is conducted through the orifice or the relief valve. However, when the vehicle shifts to a steady running state and there is no rotation speed difference between the front and rear wheels, the supply of hydraulic oil to the hydraulic chamber of the hydraulic clutch and the lubrication of the hydraulic clutch Supply of the lubricating oil is stopped. However, even when the hydraulic clutch is disengaged, the temperature is still in a considerably high temperature state. Therefore, even when the hydraulic clutch is disengaged, supply of lubricating oil is continued to cool the hydraulic clutch. Is desirable.

The present invention has been made in view of the above-mentioned circumstances, and in the power transmission device for a four-wheel drive vehicle, lubricating oil is supplied to the hydraulic clutch regardless of the engagement state of the hydraulic clutch to promote lubrication. The purpose is to do.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention relates to one of the front and rear drive wheels driven directly by a prime mover and the other front and rear drive wheel driven by a hydraulic clutch. A power transmission device for a four-wheel drive vehicle, comprising: a first hydraulic pump driven in conjunction with the one drive wheel; and a second hydraulic pump driven in conjunction with the other drive wheel. A first connecting oil passage connecting a discharge port of the first hydraulic pump and a suction port of the second hydraulic pump, and a second connecting oil connecting a discharge port of the second hydraulic pump and a suction port of the first hydraulic pump. In a power transmission device for a four-wheel drive vehicle, comprising: a first connection oil passage and a hydraulic supply oil passage connecting a first connection oil passage to an operating hydraulic chamber of a hydraulic clutch; Between the cut-off position that blocks communication and the communication position that allows communication. A switchable shutoff valve is provided, the shutoff valve is urged to the shutoff position by an urging means, and the shutoff valve is pressed against the urging means by using a discharge oil pressure from a discharge port of the second hydraulic pump as a pushing oil pressure. And a lubricating oil passage for guiding pressure oil for generating the pushing hydraulic pressure to a lubricating portion of a hydraulic clutch is provided.

[0006]

Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1 and 2 show a first embodiment of the present invention. FIG. 1 is a schematic diagram of a power transmission device for a four-wheel drive vehicle.
FIG. 2 is a hydraulic circuit diagram thereof.

As shown in FIG. 1, the output of an engine E mounted on the front part of a four-wheel drive vehicle is input to a front-wheel-side differential 2 through a transmission 1, and the output of the differential 2 is output. Is transmitted to the left and right front wheels Wf via the drive shaft 3.
The output of the engine E input to the differential device 2 is input to a power transmission device described below via a bevel gear device 4, and the output of the power transmission device is output via a bevel gear device 5 to a rear-wheel-side differential device. The output of the differential device 6 is further transmitted to the left and right rear wheels Wr via the drive shaft 7.

The power transmission device is a first hydraulic pump Pf driven by an input shaft 8 extending from the bevel gear device 4 on the front wheel side.
A second hydraulic pump Pr driven by an output shaft 9 connected to the bevel gear device 5 on the rear wheel side; and a wet-type multi-plate that transmits and blocks a driving force between the input shaft 8 and the output shaft 9. It is composed of a hydraulic clutch C of a mold type and a hydraulic circuit described later for controlling the hydraulic clutch C.

Next, the configuration of the hydraulic circuit will be described with reference to FIG. The first hydraulic pump Pf is composed of a trochoid pump, and has a first port 10 that becomes a discharge port when the vehicle moves forward and a suction port when the vehicle moves backward, and a second port 11 that becomes a suction port when the vehicle moves forward and becomes a discharge port when moving backward.
And The second hydraulic pump Pr is also made of a trochoid pump, and has a third port 12 which becomes a suction port when the vehicle moves forward and becomes a discharge port when moving backward, and a fourth port 12 which becomes a discharge port when moving forward and becomes a suction port when moving backward.
And a port 13. The discharge amount per rotation of both hydraulic pumps Pf and Pr is set so that the second hydraulic pump Pr is slightly (for example, 2.5%) larger than the first hydraulic pump Pf. Then, the first port 10 and the third port 12 are connected via the first connection oil passage 14,
The second port 11 and the fourth port 13 are connected to the second connection oil passage 15.
Connected via Note that the discharge directions of the two hydraulic pumps Pf and Pr, which are trochoid pumps, are determined by their rotational directions. Therefore, the discharge directions are reversed when the vehicle moves forward and when the vehicle moves backward. The two hydraulic pumps Pf, Pr in FIG.
Arrows indicate the ejection direction at the time of forward movement, respectively.

The hydraulic clutch C has a clutch outer 41 fixed to the input shaft 8 and a clutch inner 42 fixed to the output shaft 9 coaxially and rotatably fitted to the rear end of the input shaft 8. A plurality of clutch plates 43 slidably supported by splines formed on the inner periphery of the clutch outer 41, and a plurality of clutches slidably supported by splines formed on the outer periphery of the clutch inner 42. The plate 44 is overlapped so as to be able to abut against each other.

A clutch piston 47 is slidably fitted in a clutch cylinder 46 formed in a casing 45. Pressure oil for driving the clutch piston 47 is supplied to the right side of the clutch piston 47. A working hydraulic chamber 16 is formed. Also, clutch piston 4
A pressure plate 48, which is pressed by the clutch piston 47 and abuts the clutch plates 43 and 44 with each other, is slidably supported on the left side surface of the switch 7.

The working hydraulic chamber 16 of the hydraulic clutch C is connected to the first connecting oil passage 14 via a third connecting oil passage 17, and the operating hydraulic chamber 16 and the second connecting oil passage 15 are connected to a fourth connecting oil passage 15. The connection is made via a connection oil passage 18. Third connecting oil passage 17
Is provided with a first one-way valve 19 that allows only the flow of oil from the first connection oil passage 14 to the working hydraulic chamber 16, and the fourth connection oil passage 18 is provided with a second connection oil passage 15 from the second connection oil passage 15. Second one-way valve 20 that allows only oil flow to working hydraulic chamber 16
Is interposed. An oil tank 2 is provided between the oil tank 21 and the first connection oil passage 14 and the second connection oil passage 15.
A third one-way valve 22 that allows only the flow of oil from 1 to the first connection oil passage 14 and a fourth one-way valve 23 that allows only the flow of oil from the oil tank 21 to the second connection oil passage 15 Are respectively provided.

Above the working hydraulic chamber 16 of the hydraulic clutch C
A choke-type throttle 24 is provided at the flow position. Also activated
The orifice type throttle 25 and the first
One relief valve 26 is provided in series and the orifice
The downstream side of the mold throttle 25 and the first relief valve 26 is the output shaft 9.
Oil passage 9 formed inside₁Connected to. Oil passage 9 ₁
Are a plurality of oil holes 9 penetrating the output shaft 9 in the radial direction._TwoThrough
The lubricating portion 27 of the hydraulic clutch C, that is, the clutch plate 4
In the inner space of the clutch outer 41 in which
Communicate. At the rear end of the input shaft 8, a plurality of oil holes 50₁
A cylindrical oil guide 50 with a bottom is integrally formed.
The oil guide 50 is provided in the oil hole 9 of the output shaft 9._TwoAround the
It is provided so as to cover with a predetermined gap.

When the clutch piston 47 of the hydraulic clutch C swings due to the eccentric rotation of the input shaft 8 and the output shaft 9, the first relief valve 26 supplies air from the lubricating portion 27 of the hydraulic clutch C to the working hydraulic chamber 16. Has the function of preventing backflow.

Between the upstream position of the choke type throttle 24 and the downstream position of the orifice type throttle 25, a second relief valve 28 for regulating the upper limit of the hydraulic pressure transmitted to the working hydraulic chamber 16 is provided.
Is interposed. The second relief valve 28 is provided with a thermoswitch 51 for forcibly opening the second relief valve 28 when the oil temperature rises.

The second connecting oil passage 15 has a spool 3 urged rightward by a spring 30 inside the housing.
1, a spool valve 32 is provided. When the spool 31 is at the right position shown in the drawing,
The communication and the port 33 ₁ and the port 33 ₂ with communication is cut off between the port 33 ₃ and the port 33 _4,
When the spool 31 is moved to the left position against the spring 30, and port 33 ₃ and the port 33 ₄ is communicated with the communication between the port 33 ₁ and the port 33 ₂ by the spool 31 is cut off. Between the port 33 ₁ and port 33 _4, together with the fifth one-way valve 34 which allows only the flow of oil from port 33 ₄ to port 33 ₁ is provided, and the port 33 ₂ and the port 33 ₃ between the sixth one-way valve 35 which allows only the flow of oil from port 33 ₂ to port 33 ₃ it is provided.

Therefore, when the vehicle moves forward, that is, when the fourth port 13 of the second hydraulic pump Pr is discharging oil, the spool 31 moves to the left position and the second connecting oil passage 15
When the first connecting oil path 14 are connected by communication with the port 33 ₃ and the port 33 _4. Also, when the vehicle is traveling backward, that is, when the second port 11 of the first hydraulic pump Pf is discharging oil, the spool 31 is at the right position shown in FIG.
A connecting oil path 15 and the first connecting oil path 14 are connected by the communication between the port 33 ₁ and the port 33 _2.

[0019] When the spool 31 of the spool valve 32 is in the right position, the lubricating oil passage fifth port 33 ₅ communicates with the port 33 ₃ by the spool 31 is cut off is interposed a seventh one-way valve 52 53 communicates with the oil passage 9 ₁ of the output shaft 9 via the.

Next, the operation of the embodiment of the present invention will be described.

When the vehicle starts moving forward, the driving force of the engine E is transmitted to the front wheels Wf via the transmission 1, the differential device 2 and the drive shaft 3, and the driving force is transmitted to the differential device 2
Is transmitted to the first hydraulic pump Pf through the bevel gear device 4 and the input shaft 8 to drive the first hydraulic pump Pf.
At this time, the hydraulic clutch C is in the disengaged state and the output shaft 9
The second hydraulic pump Pr connected to is in a stopped state.
Therefore, the oil sucked into the second port 11 of the first hydraulic pump Pf from the oil tank 21 via the fifth one-way valve 34 is discharged from the first port 10 to the first connection oil passage 14. At this time, the third one-way valve 22 of the fifth connecting oil passage 36
Is closed, the entire amount of oil discharged to the first connecting oil passage 14 flows into the third connecting oil passage 17, where it is blocked by the second one-way valve 20, and the first one-way valve 19 and the choke type The oil is supplied to the operating hydraulic chamber 16 of the hydraulic clutch C via the orifice 24.

When the hydraulic clutch C is engaged as described above, the rear wheel Wr is driven via the output shaft 9, the bevel gear device 5, the differential device 6, and the drive shaft 7, and is connected to the output shaft 9. The second hydraulic pump Pr rotates. As a result, the discharge oil of the first hydraulic pump Pf is sucked into the second hydraulic pump Pr via the first connection oil passage 14 according to the increase in the rotation speed of the rear wheel Wr, and the discharge oil of the second hydraulic pump Pr is discharged. port 33 while shifted leftward the spool 31 of the spool valve 32 against the spring 30 _3, 33 ₄ and the fifth one-way valve 3
4 through the first hydraulic pump Pf. The hydraulic pressure acting on the working hydraulic chamber 16 of the hydraulic clutch C, that is, the engaging force of the hydraulic clutch C automatically changes according to the difference between the discharge amount of the first hydraulic pump Pf and the suction amount of the second hydraulic pump Pr. When the rotational speed difference between the front and rear wheels becomes substantially zero, for example, when the vehicle travels at a constant forward speed, the hydraulic pressure does not act on the operating hydraulic chamber 16 of the hydraulic clutch C, and the torque distribution to the rear wheels Wr is interrupted. It is. In the forward traveling state at a constant speed, the discharge amount of the second hydraulic pump Pr is slightly higher than the discharge amount of the first hydraulic pump Pf, as described above. the spool 31 is moved to the left against the spring 30, the excess oil discharged from the second hydraulic pump Pr via the third one-way valve 22 of the port 33 _3, 33 ₄ and the fifth connecting oil path 36 second The fluid flows back to the third port 12 of the hydraulic pump Pr.

In the above-described forward traveling at a constant speed, the first
The discharge oil of the hydraulic pump Pf and the second hydraulic pump Pr is
When circulating through the connection oil passage 14 and the second connection oil passage 15, the discharge oil of the second hydraulic pump Pr causes the spool 31 of the spool valve 32 to move leftward against the spring 30,
Second connecting oil path between the fourth port 13 and port 33 ₃ 1
5, a hydraulic pressure corresponding to the urging force of the spring 30 is generated.
As a result, the air sucked into the oil circulating from the side clearances of the rotors of the two hydraulic pumps Pf and Pr is compressed by this hydraulic pressure and is sequentially discharged from the side clearances near the fourth port 13 of the second hydraulic pump Pr. Therefore, air does not stay in the circulating oil. As a result, after that, when the rotational speed difference occurs between the front wheel Wf and the rear wheel Wr, and the discharge amount (suction amount) difference between the first and second hydraulic pumps Pf, Pr occurs, the hydraulic pressure rises due to the stagnant air. The inconvenience that the delay and, as a result, the response of the hydraulic clutch C is delayed is reliably prevented.

When there is a difference between the discharge amounts (suction amounts) of the first and second hydraulic pumps Pf and Pr, the hydraulic pressure corresponding to the set load of the first relief valve 26 is applied to the operating hydraulic chamber 16 of the hydraulic clutch C. Acts immediately. After the first relief valve 26 is opened, it is determined by the difference between the discharge amounts of the first and second hydraulic pumps Pf and Pr, the pressure drop characteristics of the orifice type throttle 25 and the choke type throttle 24, the viscosity of oil, and the like. The hydraulic pressure acts on the working hydraulic chamber 16 of the hydraulic clutch C. Since the upper limit of the hydraulic pressure is limited by the set load of the second relief valve 28, the upper limit of the transmission torque of the hydraulic clutch C is adjusted by appropriately setting the set load of the second relief valve 28. Can be.

The amount of oil passing through the choke throttle 24 is affected by the viscosity of the oil. When the viscosity of the oil increases in a low temperature state, the amount of oil flowing through the choke throttle 24 decreases. The amount of oil passing through the working hydraulic chamber 16 and the orifice type throttle 25 also decreases. At this time,
The amount of pressure drop generated before and after the orifice-type throttle 25 is proportional to the square of the amount of oil passing through the orifice-type throttle 25.
, The amount of pressure drop at the upstream choke type throttle 24 increases accordingly. As a result, the oil pressure acting on the working oil pressure chamber 16 in a low temperature state, that is, the pressure obtained by subtracting the pressure drop by the choke type throttle 24 from the pressure set by the second relief valve 28 becomes small. Therefore, even if the friction coefficient increases due to an increase in the viscosity of the oil, the pressing force of the clutch disk by the hydraulic pressure decreases by that much, so that the increase in the engagement force of the hydraulic clutch C at low temperatures is prevented as a whole. On the other hand, in a high-temperature state, the viscosity of the oil decreases and the friction coefficient decreases. In this case, however, the amount of pressure drop by the choke-type throttle 24 decreases conversely, and the operating hydraulic chamber 1 of the hydraulic clutch C
Since the hydraulic pressure acting on the hydraulic clutch 6 is increased, the pressing force of the clutch disk is increased by that amount, and a decrease in the engaging force of the hydraulic clutch C is prevented.

The oil discharged from the working hydraulic chamber 16 of the hydraulic clutch C through the orifice type throttle 25 and the first relief valve 26 when the vehicle starts moving forward and when the vehicle is rapidly accelerated, From the upstream position to the second relief valve 28
The discharged oil through, supplied from the oil passage 9 ₁ and oil holes 9 _second output shaft 9 to the lubrication portion 27 of the hydraulic clutch C,
Therefore scattered radially outward by centrifugal force from the oil hole 50 ₁ of the oil guide 50 to rotate relative to the output shaft 9, a plurality of oil grooves 42 ₁ formed in the axial direction on the peripheral surface of the clutch inner 42
To lubricate the clutch plates 43 and 44 evenly. The oil that has lubricated the clutch plates 43 and 44 returns to the oil tank 21 through an oil passage (not shown).

As described above, since the hydraulic oil is not supplied to the working hydraulic chamber 16 of the hydraulic clutch C when the vehicle is traveling forward at a constant speed, the lubricating oil is supplied to the lubricating portion 27 of the hydraulic clutch C via the working hydraulic chamber 16. Will not be supplied. However, a predetermined oil pressure is generated when the oil discharged from the fourth port 13 of the second hydraulic pump Pr moves the spool 31 of the spool valve 32 leftward against the spring 30 when the vehicle is traveling at a constant forward speed. Excess oil is discharged to the second connecting oil passage 15 due to a difference in discharge amount per rotation of the two hydraulic pumps Pf and Pr, and a part of the surplus oil is generated when the spool valve 32 is opened. is supplied from the lubricating oil passage 53 in the pressure in the oil passage 9 ₁ of the output shaft 9, from which the oil hole 9 ₂
To the lubrication unit 27 of the hydraulic clutch C. In this way, even during forward traveling at a constant speed in which the hydraulic clutch C is disengaged, it is possible to supply lubricating oil to the lubricating portion 27 of the hydraulic clutch C to effectively lubricate the clutch plates 43 and 44. This makes it possible to prevent overheating of the hydraulic clutch C.

The seventh one-way valve 5 provided in the lubricating oil passage 53
2 exhibits the following functions. That is, when a negative pressure is generated in the second connecting oil passage 15 when the vehicle starts moving forward or suddenly accelerates, the air sucked from the lubricating portion 27 of the hydraulic clutch C causes the lubricating oil passage 53, the fifth port 33 ₅ , It is possible to prevent the first hydraulic pump Pf from being sucked through the fourth port 33 ₄ , the fifth one-way valve 34 and the second connecting oil passage 15.

When only the front wheel Wf steps on a road surface having a low friction coefficient during a forward traveling at a constant speed, or when the vehicle is suddenly accelerated, the front wheel Wf may transiently slip. In such a state, the discharge amount of the first hydraulic pump Pf connected to the input shaft 8 exceeds the suction amount of the second hydraulic pump Pr connected to the output shaft 9, and the third one-way valve 22 is closed. As a result, the communication between the first connection oil passage 14 and the second connection oil passage 15 via the fifth connection oil passage 36 is blocked, so that the hydraulic clutch C is engaged and the rear wheel Wr The drive torque is distributed.

When a braking force is applied to the wheels, the distribution of the braking force between the front and rear wheels is generally set higher on the front wheel Wf side than on the rear wheel Wr side.
Locks first. In addition, since the engine brake from the constant speed operation acts only on the front wheel Wf, the rotational speed of the front wheel Wf transiently becomes lower than that of the rear wheel Wr in this case as well. In such a case, the discharge amount of the second hydraulic pump Pr exceeds the suction amount of the first hydraulic pump Pf, and excessive oil is discharged to the second connecting oil passage 15. Further, when the front wheel Wf is completely locked, the first hydraulic pump Pf stops and only the second hydraulic pump Pr rotates.
The total amount of oil discharged from the hydraulic pump Pr becomes excessive. However, this excessive discharge oil is supplied to the port 33 of the spool valve 32.
_3, flows back to the third port 12 of the second hydraulic pump Pr via the third one-way valve 22 of the port 33, _fourth and fifth connecting oil path 36. Thus, the rotation speed of the rear wheel Wr is
Since the hydraulic pressure based on the difference between the discharge amounts of the first and second hydraulic pumps Pf and Pr does not act on the operating hydraulic chamber 16 of the hydraulic clutch C even when the rotation speed exceeds f, the hydraulic clutch C is maintained in the disengaged state. As a result, the transmission of the braking force from the front wheel Wf to the rear wheel Wr is prevented, so that the distribution of the braking force between the front and rear wheels does not change.

Since the hydraulic clutch C is not engaged during the forward braking of the vehicle, the oil that has passed through the first relief valve 26 does not lubricate the hydraulic clutch C. However, as in the case of the above-mentioned traveling at a constant forward speed of the vehicle, a part of the discharge oil of the second hydraulic pump Pr is supplied to the hydraulic clutch C via the spool valve 32 and the lubricating oil passage 53, and the lubricating portion 27 Is performed without any problems.

When the vehicle moves backward, the rotation directions of the first and second hydraulic pumps Pf and Pr are both reversed, and the relationship between the discharge port and the suction port is opposite to the above.

That is, when the rotation speed of the front wheel Wf becomes larger than the rotation speed of the rear wheel Wr at the time of reverse start or rapid reverse acceleration, the discharge amount of the first hydraulic pump Pf exceeds the suction amount of the second hydraulic pump Pr. Therefore, a hydraulic pressure is generated in the second connecting oil passage 15. At this time, the spool 3 of the spool valve 32
1 is held at a position shown in the figure by a spring 30, and the second connecting oil is determined by the difference between the discharge amount from the second port 11 of the first hydraulic pump Pf and the suction amount from the fourth port 13 of the second hydraulic pump Pr. The oil discharged to the passage 15 is blocked from flowing into the fifth connecting oil passage 36 by the fourth one-way valve 23 and the fifth one-way valve 34 as described above, and flows into the fourth connecting oil passage 18. Then, the hydraulic clutch C passes through the second one-way valve 20 and is blocked by the first one-way valve 19 and supplied to the operating hydraulic chamber 16 of the hydraulic clutch C, and the hydraulic clutch C is engaged to distribute the driving torque to the rear wheel Wr. Is done. When the rotation speed of the rear wheel Wr increases and the vehicle enters a reverse constant speed traveling state, the first hydraulic pump P
f and the rotation speed of the second hydraulic pump Pr are the same,
Since the discharge amount per rotation of the second hydraulic pump Pr is larger than the discharge amount per rotation of the first hydraulic pump Pf,
Oil corresponding to the difference is supplied to the first connection oil passage 14.
As a result, the front wheel W
Torque is distributed from the f side to the rear wheel Wr side.

In the reverse traveling state at constant speed, the load of the spring 30 of the spool valve 32 does not act on the oil circulating in the circulation oil passage composed of the first connection oil passage 14 and the second connection oil passage 15. However, since the reverse constant speed traveling state generally does not continue for a long time, both hydraulic pumps Pf and Pr
The suction of air from the side clearance of the rotor and the stop of the supply of the lubricating oil to the hydraulic clutch C do not substantially pose a problem.

During reverse braking, the first hydraulic pump Pf
Is lower than that of the second hydraulic pump Pr,
A hydraulic pressure is generated in the first connection oil passage 14 due to a difference between a discharge amount from the third port 12 of the second hydraulic pump Pr and a suction amount from the first port 10 of the first hydraulic pump Pf. At this time, since the third one-way valve 22 is closed, the third connecting oil passage 17 is closed.
The hydraulic clutch C is engaged via the first one-way valve 19 of
The braking force of the front wheel Wf is transmitted to the rear wheel Wr.

When the vehicle described above moves backward, the first
Since the second port 11 of the hydraulic pump Pf is a discharge port and the fourth port 13 of the second hydraulic pump Pr is a suction port, the spool 31 of the spool valve 32 is always held at the right position shown in the figure. At this time, spool 3
1 is locked to the left position, the first hydraulic pump Pf
Discharge pressure from the second port 11 is blocked by the fifth one-way valve 34 acts on the port 33 ₁ of the spool valve 32, spool 31 that the lock is pushed back to the right position, which is the normal position of the. At this time, even if the lock of the spool 31 is not released, the hydraulic pressure generated in the second connecting oil passage 15 is released from the second relief valve 28 via the fourth connecting oil passage 18, so that the first hydraulic pump Pf No excessive load is applied to the

Next, a second embodiment of the present invention will be described with reference to FIGS.

As is apparent from comparison with the first embodiment shown in FIG. 1, the second embodiment shown in FIG.
r, an oil passage connecting the fourth port 13 and the fifth connection oil passage 36, a fourth one-way valve 23 interposed in the oil passage, and a seventh one-way valve 52 interposed in the lubrication oil passage 53. And the first relief valve 26 downstream of the orifice type throttle 25 are eliminated. Even if the fourth one-way valve 23, the seventh one-way valve 52 and the first relief valve 26 are eliminated, the function of the power transmission device is maintained as described below. Hereinafter, the reason will be described. (1) Fourth one-way valve 23 As described in the first embodiment, the fourth one-way valve 23
When the vehicle starts reversely or when the vehicle reversely accelerates rapidly, the rotational speed of the front wheel Wf becomes higher than the rotational speed of the rear wheel Wr, the discharge amount of the first hydraulic pump Pf exceeds the suction amount of the second hydraulic pump Pr, and the second connection is established. To prevent the oil blocked by the spool valve 32 from escaping to the fifth connecting oil passage 36 through the sixth one-way valve 35 when the oil pressure is generated in the oil passage 15 and to engage the hydraulic clutch C. It is arranged in.

In the second embodiment, the fourth one-way valve 23 itself is eliminated, and the oil passage in which the fourth one-way valve 23 is interposed is also eliminated, so that the fourth port 13 of the second hydraulic pump Pr and Since the communication between the fifth connecting oil passages 36 is blocked, the oil generated in the second connecting oil passages 15 does not escape to the fifth connecting oil passages 36 at the time of reverse start or reverse rapid acceleration. .

Further, even if the fourth one-way valve 23 is abolished, no inconvenience occurs at the time of reverse traveling at a constant speed and the reverse braking for the following reasons. When traveling at constant reverse speed When traveling at constant reverse speed, the second port 11 of the first hydraulic pump Pf
From the port 3 to the second connecting oil passage 15
3 ₁ , the port 33 ₂ and the sixth one-way valve 35 through the second
It is sucked into the fourth port 13 of the hydraulic pump Pr. At this time, since the capacity of the second hydraulic pump Pr is slightly larger than the capacity of the first hydraulic pump Pf, in the first embodiment, the insufficient oil is removed from the oil tank 21 through the fourth one-way valve 23 through the fourth one-way valve 23. It was supplied to the fourth port 13 of the hydraulic pump Pr. However, it is the fourth one-way valve 23 and the oil passage is discontinued, shortage of oil oil tank 21 from the fifth connecting oil path 36, the fifth one-way valve 34, ports 33 _1, port 33 ₂ and The second hydraulic pump P passes through the sixth one-way valve 35
Since it is sucked into the fourth port 13 of r, no trouble occurs. During reverse braking During reverse braking, since the rotation speed of the second hydraulic pump Pr exceeds that of the first hydraulic pump Pf, the second hydraulic pump Pr
Of the oil supplied to the fourth port 13 of FIG. The shortage of oil is supplied from the oil tank 21 to the fifth connecting oil passage 36, the fifth one-way valve 34, and the port without passing through the fourth one-way valve 23, as in the case of the above-described backward constant speed traveling. 3
3 ₁ , the port 33 ₂ and the sixth one-way valve 35 through the second
It is sucked into the fourth port 13 of the hydraulic pump Pr. (2) Seventh one-way valve 52 As described in the first embodiment, the second hydraulic pump Pf is used when the vehicle in which the hydraulic oil is not supplied to the operating hydraulic chamber 16 of the hydraulic clutch C is driven at a constant forward speed and when the vehicle is braked forward. Discharges the spool valve 32 to be opened, and is supplied from the lubricating oil passage 53 to the lubricating portion 27 of the hydraulic clutch C. The seventh one-way valve 52 allows the air sucked from the lubricating portion 27 of the hydraulic clutch C to flow through the lubricating oil passage when a negative pressure is generated in the second connecting oil passage 15 when the vehicle starts moving forward or accelerates rapidly. The first hydraulic pump Pf is prevented from being sucked into the first hydraulic pump Pf via the 53, the fifth port 33 ₅ , the fourth port 33 ₄ , the fifth one-way valve 34, and the second connecting oil passage 15. However, since the spool valve 32 supplements its function for the following reasons, the seventh one-way valve 52 can be eliminated. At the time of forward start and forward rapid acceleration When the second hydraulic pump Pr is stopped at the beginning of forward start and oil is not discharged from the fourth port 13, the spool urged rightward by the spring 30. 31 because closing the ports 33 _5, air backflow from the lubricating oil passage 53 even abolished the seventh one-way valve 52 does not occur. The second hydraulic pump Pr at the later stage of forward start and at the time of rapid forward acceleration
Since but the oil is discharged from the fourth port 13 is rotated, the spool 31 is port 33 ₅ opens moved to the left, but the air back flow from the lubricating oil passage 53 by the discharge pressure from the fourth port 13 is generated do not do. At the time of forward constant speed traveling and forward braking, at the time of forward constant speed traveling and forward braking, the second hydraulic pump P
r from the fourth port 13, the lubricating oil passage 53
Backflow of air from the air does not occur. During reverse during reverse travel, the spool 31 of the spool valve 32 by the biasing force of the discharge pressure and the spring 30 from the second port 11 of the first hydraulic pump Pf closes the port 33 _5, the air backflow from the lubricating oil passage 53 Does not occur. (3) First relief valve 26 As described in the first embodiment, the first relief valve 2
Reference numeral 6 has a function of preventing air from flowing back from the lubricating portion 27 to the working hydraulic chamber 16 when the clutch piston 47 of the hydraulic clutch C swings. The orifice type throttle 25 has the following structure. As a result, the first relief valve 2
6 can be abolished.

As shown in FIG. 4, the orifice type throttle 25
Is the first orifice 25 ₁ on the upstream side (the working hydraulic chamber 16 side)
And consists of the downstream side (the lubrication unit 27 side) the second orifice 25 ₂ which the. Upstream oil passage 54 ₁ and the downstream-side oil passage 54 ₂ sandwiching the second orifice 25 ₂ is formed with a step to be slightly lower than the upstream oil passage 54 ₁ is the downstream side oil passage 54 _2, The second orifice 25 ₂ has an air reservoir 55 formed on the upper wall of the upstream oil passage 54 ₁ and the downstream oil passage 5.
4 opened in the wall vicinity of the upper _two.

[0042] Thus, the air from the lubrication unit 27 of the hydraulic clutch C is also passed through the second orifice 25 _2, entering the working hydraulic pressure chamber 16 is blocked by trapped air reservoir 55 defined therein .

[0043] Figure 5 shows a modification of the orifice type throttle 25, the upstream-side oil passage 54 sandwiching the second orifice 25 _2
1 and downstream oil passage 54 _2, the downstream oil passage 54 ₂ is formed with a step to be slightly lower than the upstream side oil passage 54 _1, the second orifice 25 ₂ upstream oil passage 54
₁ Open near the lower wall.

[0044] Thus, the air from the lubrication unit 27 of the hydraulic clutch C can not pass through the second orifice 25 _2, entering the working hydraulic pressure chamber 16 is prevented.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments, and various design changes can be made.

For example, in the embodiment, the front wheel Wf is directly driven by the engine E, and the front wheel Wf and the rear wheel Wr are connected via the hydraulic clutch C to achieve the four-wheel drive state. On the contrary, it is also possible to directly drive the rear wheel Wr by the engine E.

[0047]

As described above, according to the present invention, the shutoff valve provided in the second connecting oil passage is biased to the shutoff position by the biasing means, and the discharge hydraulic pressure from the discharge port of the second hydraulic pump is reduced. Since the shutoff valve can be pushed to the communication position against the urging means as the pushing oil pressure, and the pressure oil for generating the pushing oil pressure is guided to the lubricating portion of the hydraulic clutch via the lubricating oil passage, Even when there is no rotational speed difference between the front and rear drive wheels and both hydraulic pumps do not generate hydraulic pressure for engaging the hydraulic clutch, it is possible to lubricate the hydraulic clutch with the pressure oil generating the pushing hydraulic pressure. it can.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a power transmission device of a four-wheel drive vehicle.

FIG. 2 is a hydraulic circuit diagram of the power transmission device according to the first embodiment.

FIG. 3 is a hydraulic circuit diagram of a power transmission device according to a second embodiment.

FIG. 4 is an enlarged view of an orifice type throttle.

FIG. 5 is a view showing a modified example of the orifice type aperture stop.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 1st port (discharge port) 11 2nd port (suction port) 12 3rd port (suction port) 13 4th port (discharge port) 14 1st connection oilway 15 2nd connection oilway 16 Working hydraulic chamber 17th 3 connection oil passage (hydraulic supply oil passage) 27 lubrication unit 30 spring (biasing means) 32 spool valve (shutoff valve) 53 lubrication oil passage C hydraulic clutch E engine (motor) Pf first hydraulic pump Pr second hydraulic pump Wf Front wheel (one driving wheel) Wr Rear wheel (the other driving wheel)

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Kentaro Arai 1-4-1 Chuo, Wako-shi, Saitama Pref. Honda Technical Research Institute Co., Ltd. (56) References JP-A-5-8650 (JP, A) (58) Surveyed field (Int.Cl. ⁶ , DB name) B60K 17/348 F16D 43/284

Claims (1)

(57) [Claims] The vehicle has one of front and rear drive wheels (Wf) directly driven by a prime mover (E) and the other front and rear drive wheels (Wr) driven by a hydraulic clutch (C). A power transmission device for a wheel drive vehicle, wherein the first hydraulic pump (Pf) is driven in conjunction with the one drive wheel (Wf), and is driven in conjunction with the other drive wheel (Wr). A second hydraulic pump (Pr), a first connecting oil passage (14) connecting a discharge port (10) of the first hydraulic pump (Pf) and a suction port (12) of the second hydraulic pump (Pr), A second connecting oil passage (15) connecting the discharge port (13) of the second hydraulic pump (Pr) and the suction port (11) of the first hydraulic pump (Pf), and a first connecting oil passage (14). A hydraulic supply oil passage (17) for connecting the hydraulic clutch (C) to an operating hydraulic chamber (16). In the power transmission device for a four-wheel drive vehicle, the shut-off valve can be switched between a shut-off position for cutting off the communication of the second connecting oil passage (15) with the second connecting oil passage (15) and a communicating position for allowing the communication. (32) and the shut-off valve (32)
To the shut-off position by the urging means (30), and the urging means (30) using the discharge oil pressure from the discharge port (13) of the second hydraulic pump (Pr) as the pushing oil pressure. ), And a lubricating oil passage (53) for guiding pressure oil for generating the pushing hydraulic pressure to the lubricating portion (27) of the hydraulic clutch (C) is provided. A power transmission device for a four-wheel drive vehicle.