JPH09189352A - Charge pump for HST transmission - Google Patents

Abstract

(57) Abstract: In a configuration in which a charge pump driven by an input shaft of an HST transmission is installed on one surface of a center section inside a housing, a spring that regulates a charge relief pressure is a corrugated plate type. However, if the spring constant is relatively large and the mounting length during assembly varies, the relief setting pressure will be different. SOLUTION: A coil spring 26 is arranged between a pump case 10 accommodating a charge pump 11 and an inner surface of a housing to bring the pump case into close contact with one surface of a center section 5 so that a discharge port of the charge pump is provided on one surface of the center section. While communicating with the opened hydraulic oil supply port 5c, the pump case is made unrotatable around the input shaft and movable in the axial direction of the input shaft 3 by the locking means provided between the pump case and the center section. In addition, the extended end portion 3a of the input shaft is fitted into the pivot hole 10c provided in the pump case so that the radial force of the pump case is received by the input shaft.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charge pump support mechanism having a charge relief function in an HST transmission.

[0002]

2. Description of the Related Art A charge pump for replenishing hydraulic fluid is urged closely toward one surface of a center section installed in a housing of an HST transmission, and charging is performed by an input shaft of the HST transmission penetrating the center section. The structure for driving the pump is the same as that of the applicant of the present invention.
The technique described in Japanese Patent No. 6 is known. In this technology, the pump case that accommodates the charge pump is elastically supported by a spring arranged between the lower surface of the pump case and the inner bottom surface of the housing without using bolts, etc. By closely urging the lower horizontal part of the lower part of the lower part, a charge pump with a self-charge relief function is constructed.

[0003]

In the prior art as described above, a pin is erected on the upper surface of the pump case and locked to the lower surface of the horizontal portion of the center section, whereby the pump case rotates around the input shaft. It is disabled, the communication between the discharge port and the hydraulic oil supply port is maintained well, and the input shaft can be moved in the axial direction during the relief operation. On the other hand, when the charge pump is driven by the input shaft, the radial force generated in the pump case will be received by the above-mentioned pin, but since it acts as a shearing force on the pin, it may be cut off. A tough and highly rigid material had to be used, leaving room for improvement in this respect. In addition, the above-mentioned spring that regulates the charge relief pressure is a corrugated ring type, and the spring constant is relatively large, and if the mounting length varies during assembly, the relief setting pressure will be There was also the problem of being different.

[0004]

The present invention is configured as follows to solve the above problems. The charge pump according to claim 1, wherein the charge pump 11 for replenishing hydraulic oil driven by the input shaft 3 of the HST transmission is installed on one surface of the center section 5 inside the housing of the HST transmission. The coil spring 26 is disposed between the pump case 10 accommodating the pump housing 11 and the inner surface of the housing so that the pump case 10 can be moved to the center section 5.
The discharge port of the charge pump 11 is brought into close contact with one surface of the center section 5 to communicate with the hydraulic oil supply port 5c opened on one surface of the center section 5, while the locking means provided between the pump case 10 and the center section 5 Is configured to be non-rotatable around the input shaft 3 and movable in the axial direction of the input shaft 3, and the extended end portion 3a of the input shaft 3 is fitted into a pivot hole 10c provided in the pump case 10 so that the pump The radial force of the case 10 is received by the input shaft 3.

In the second aspect, the charge pump 11 driven by the input shaft 3 of the HST transmission is set to the HS
In the configuration installed on one surface of the center section 5 inside the housing of the T-type transmission, the charge pump 11
The coil spring 26 is disposed between the pump case 10 that accommodates the charge pump 11 and the inner surface of the housing, and the pump case 10 is closely attached to one surface of the center section 5 to charge the charge pump 11.
The discharge port of the pump is connected to the hydraulic oil supply port 5c opened on one surface of the center section 5, while the pump case 1
The locking means provided between 0 and the center section 5 makes the pump case 10 unable to rotate around the input shaft 3,
In addition, it is configured to be movable in the axial direction of the input shaft 3, and one end side of the pump case 10 is slidably fitted into a recess 5k provided on one surface of the center section 5 so that the radial force of the pump case 10 is applied to the center section. It was accepted in 5.

In the third aspect, the charge pump 11 driven by the input shaft 3 of the HST transmission is HS
In the configuration installed on one surface of the center section 5 inside the housing of the T-type transmission, the charge pump 11
The coil spring 26 is disposed between the pump case 10 that accommodates the charge pump 11 and the inner surface of the housing, and the pump case 10 is closely attached to one surface of the center section 5 to charge the charge pump 11.
The discharge port of the pump is connected to the hydraulic oil supply port 5c opened on one surface of the center section 5, while the pump case 1
The locking means provided between 0 and the center section 5 makes the pump case 10 unable to rotate around the input shaft 3,
In addition, the protrusion 10k or the protrusion that is configured to be movable in the axial direction of the input shaft 3 and is positioned on the virtual axis of the input shaft 3 on one of the surfaces of the pump case 10 and the housing that face each other. 2k is provided, and a recess 2n or a pivot hole 10c is provided on the other surface, and the projections 10k and 2k and the recess 2n or the pivot hole 10c are slidably fitted therein so that the radial force of the pump case 10 is accommodated in the housing. It was made to be accepted by.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the structure of an embodiment of the present invention shown in the accompanying drawings will be described. FIG. 1 is an overall front sectional view of a hydrostatic transmission, FIG. 2 is an enlarged sectional view of an essential part of a charge pump showing a first embodiment of the present invention, FIG. 3 is an exploded perspective view of the charge pump for the center section, and FIG. FIG. 5 is an enlarged sectional view of an essential part of a charge pump showing a second embodiment of the present invention, FIG. 5 is a rear view of a pump case similarly installed in the center section, and FIG. 6 is an essential part of a charge pump showing a third embodiment of the present invention. Enlarged sectional view, FIG.
FIG. 8 is an enlarged cross-sectional view of an essential part of a charge pump showing a fourth embodiment of the present invention, FIG. 8 is an enlarged sectional view of an essential part of a charge pump showing a fifth embodiment of the present invention, and FIG. FIG. 10B is a rear view of the pump case showing the detent means of the pump case with respect to the section, FIG. 10B is a rear view of the pump case showing another detent means of the pump case with respect to the center section, and FIG. 10 is a sixth embodiment of the present invention. FIG. 11 is an enlarged cross-sectional view of the main part of the charge pump showing an example, FIG. 11 is a front view of the same pump case, and FIG. A sectional view, FIG. 13 is an exploded perspective view of the charge pump with respect to the center section, and FIG. 14 is an enlarged view of the main part of the check valve housed in the pump case. Sectional view, FIG. 15 is a plan sectional view of the center section.

The construction of the hydrostatic transmission will be described with reference to FIG. The housing is configured by joining an upper half case 1 and a lower half case 2 at a horizontal joint surface. A hydrostatic transmission is housed in this housing, and the working oil is filled in the housing as an oil reservoir. Inside the upper half case 1, an L-shaped center section 5 having a horizontal portion and a vertical portion in a side sectional view is fixed by bolts 6 ... A pump mounting surface 20 is formed on the upper surface of the horizontal portion of the center section 5, and the pump mounting surface 20 is formed.
In addition, a cylinder block 16 that constitutes an axial piston type hydraulic pump P is rotatably installed.
In the plurality of cylinder holes formed in the cylinder block 16, the pistons 13, 13, ...
It is urged by and is inserted freely. The piston 1
The thrust bearing held by the movable swash plate 8 is in contact with the head portion of No. 3.

The input shaft 3 serving as a pump shaft is engaged with the rotation center position of the cylinder block 16. The input shaft 3
The rotation axis extends along the vertical direction, the upper end side is supported by the upper half case 1, and the lower end side is supported by the pump mounting surface 20 of the center section 5. The upper end side of the input shaft 3 extends further upward and protrudes outside the upper half case 1. An input pulley (not shown) is fixedly mounted on the upper end of the input shaft 3, and power is input from an engine or the like via the belt.

A motor mounting surface 21 is formed on the side surface of the vertical portion of the center section 5. The motor mounting surface 2
1, a cylinder block 17 constituting an axial piston type hydraulic motor M is rotatably installed. In the plurality of cylinder holes formed in the cylinder block 17, the pistons 14, 14, ...
・ It is pushed in by and is inserted freely. The heads of the pistons 14, 14 ... Contact the thrust bearings held by the fixed swash plate 9. The fixed swash plate 9 is sandwiched and fixed between the upper half case 1 and the lower half case 2.

The motor shaft 4 is engaged with the rotation center position of the cylinder block 17. A bearing portion for supporting one end side of the motor shaft 4 is formed on a joint surface between the upper half case 1 and the lower half case 2. Motor shaft 4
The other end side of is supported by the motor mounting surface 21 of the center section 5. Further, a pair of left and right axles (not shown) is housed in the housing. A gear 25 is provided on the motor shaft 4, and the gear 25 is linked to the axle via a power transmission mechanism such as a gear. The tip of the motor shaft 4 projects outward from the housing,
A brake disk 15 for braking the axle is fixedly mounted on the motor shaft 4.

A pair of oil passages 5a and 5b are bored in parallel in the center section 5, each of which has a pair of kidney ports open to the pump mounting surface 20 and a pair of openings to the motor mounting surface 21. Cylinder block 16 of the hydraulic pump P by communicating with the kidney port of
And a cylinder block 17 of the hydraulic motor M constitute a closed circuit for circulating the working oil. Check valves C and C for replenishing hydraulic oil are provided at the open ends of the oil passages 5a and 5b, respectively.

A hydraulic oil supply port 5c is opened on the lower surface of the horizontal portion of the center section 5 and communicates with the discharge side of the charge pump 11 described later. The hydraulic oil supply port 5c communicates with the oil passage 5d in the center section 5,
The oil passage 5d communicates with the oil passage 5e reaching the inlet port of the check valve C.C. The open end of the oil passage 5d is closed by a sleeve 6a having an insertion hole for the bolt 6. The sleeve 6a functions as a blind plug for closing the open end of the oil passage 5d.

The movable swash plate 8 is interlocked with a gear shift operation tool such as a lever or a pedal mounted on a traveling vehicle. When the movable swash plate 8 is tilted from the neutral position to the left and right, the hydraulic pump P discharges it. By changing the amount and direction of the oil to be supplied and sending the hydraulic oil to the hydraulic motor M through the closed circuit of the center section 5, it is possible to obtain a stepless output rotation of the motor shaft 4 of the hydraulic motor M. HST
Constitutes a variable speed transmission.

As shown in FIG. 15, the check valves C and C are provided with push pins 33 and 33 for opening the inlet side and the outlet side thereof to the oil reservoir. The tip end of is opposed to the bypass operation body 22 by being biased by the spring of the center section 5 and protruding outward in parallel. The bypass operating body 22 has a long hole 2
2a is opened, a cam pin 34 is inserted into the elongated hole 22a, the cam pin 34 is fixed to the operation shaft 35, and the operation shaft 35 has an upper end protruding outside the housing to fix the bypass lever 23. . Therefore, when the vehicle is towed or the like, when the bypass lever 23 is rotationally operated, the bypass operating body 22 is pressed through the cam pin 34, and the push pins 33, 33 are pushed in to open and close the check valves C, C. The circuit is opened in the housing to allow free rotation of the hydraulic motor.

A pump case 10 accommodating a charge pump 11 is installed on the lower surface of the horizontal portion of the center section 5 opposite to the pump mounting surface 20. The pump case 10 is formed by molding a sintered metal material. A recess is formed on the upper surface of the pump case 10,
A trochoid type charge pump 11 for replenishing oil is housed in the closed circuit. The charge pump 11 comprises an inner rotor 11a and an outer rotor 11b, the outer periphery of the outer rotor 11b is rotatably guided by the inner surface of the pump case 10, and the inner rotor 11a meshing with the inner teeth of the outer rotor 11b is the outer rotor 11b. It is located inside. The thickness dimension of the inner rotor 11a and the outer rotor 11b is set to be larger than the depth dimension of the recess of the pump case 10 (a).

The inner rotor 11a is slidable in the axial direction with respect to the pin 36 attached to the lower end of the input shaft 3 protruding from the lower surface of the horizontal portion of the center section 5.
Further, the charge pump 11 is provided with a groove portion 11k for relatively non-rotatably engaging, the rotation shaft center of the charge pump 11 is oriented in the vertical direction, and the charge pump 11 is driven by the input shaft 3. An intake port is formed on one side of the meshing portion of the inner rotor 11a and the outer rotor 11b, and a discharge port is formed on the other side. The discharge port faces the hydraulic oil supply port 5c and communicates with each other. However, the charge pump is not limited to the trochoid pump type described above, and may be a gear pump type or a vane pump type.

A coil spring 26 is interposed between the lower surface of the pump case 10 and the inner bottom surface of the lower half case 2 so that the end surfaces of the inner rotor 11a and the outer rotor 11b of the pump case 10 are at the center section 5. It is attached in a floating state by being urged so as to be in close contact with the lower surface of the horizontal part. The biasing force of the coil spring 26 defines the pump discharge pressure of the charge pump 11. That is,
When the pressure in the discharge port of the charge pump 11 becomes equal to or higher than the predetermined biasing force of the coil spring 26, the pump case 1
0 moves downward along the axial direction of the input shaft 3 together with the inner rotor 11a and the outer rotor 11b, and a gap is generated between the end surface of the inner rotor 11a and the outer rotor 11b and the lower surface of the horizontal portion of the center section 5, The discharge port of the charge pump 11 is opened in the oil sump in the housing so that pressure oil of a predetermined value or more is discharged.
The pump case 10 and the coil spring 26 are configured to function as a charge relief valve.

In order to accommodate the pump case 10,
An annular oil filter 12 having an inner diameter larger than the outer diameter of the pump case 10 is disposed between the lower surface of the horizontal portion of the center section 5 and the inner bottom surface of the lower half case 2.
That is, the oil filter 12 is formed by molding a porous material into an annular shape and a size enough to cover the entire pump case 10, and a sealing material 12a is formed on each of the annular end portions.
・ 12b is put on. The inside and outside of the oil filter 12 are partitioned by bringing one sealing material 12a into close contact with the lower surface of the horizontal portion of the center section 5 and the other sealing material 12b into close contact with the inner bottom surface of the lower half case 2. A suction port 10 a communicating with the suction port of the charge pump 11 is opened on the lower surface of the pump case 10 and communicates with the inside of the oil filter 12.

The present invention is applied to the pump case 10 which is installed in a floating state by the coil spring 26 on the lower surface of the horizontal portion of the center section 5 as described above, without being fixed by bolts.

Next, a first embodiment of the present invention will be described with reference to FIGS. That is, a plurality of (two in this embodiment) guide pins 27, 27 are provided on the lower surface of the horizontal portion of the center section 5, while the guide pins 27, 27 can be fitted to the outer peripheral portion of the pump case 10. By forming the concave portions 10e, 10e, the locking means of the pump case 10 is configured, and while allowing the pump case 10 to move in the axial direction, the mounting position of the pump case 10 with respect to the center section 5 is about the axis of the input shaft 3. Of the charge pump 11 to the hydraulic oil supply port 5c.
The communication state of the discharge port is always maintained in good condition.

Further, since a force in the radial direction is generated in the pump case 10 when the charge pump 11 is driven,
In order to receive the radial force, the pump case 10
A pivot hole 10c is provided at the same axial center position as the input shaft 3 on the lower surface of the, and the extended end portion (lower end portion) 3a of the input shaft 3 extended into the pivot hole 10c is slidably fitted, While allowing the pump case 10 to move in the axial direction, the radial force thereof is received by the center section 5 via the input shaft 3. In addition, the pump pin 1 is attached to the guide pin 27 for preventing the pump case 10 from rotating around.
Since a radial force (bending stress) of 0 does not act, a simple one having relatively low rigidity can be used.

A second embodiment shown in FIGS. 4 and 5 will be described.
In this embodiment, since the radial force generated in the pump case 10 is directly received by the center section 5,
On the lower surface of the horizontal part of the center section 5, the pump case 10
The recess 5k having substantially the same shape as that of the pump case 10 is provided.
The upper surface side of the is slidably fitted inside the recess 5k. It is the guide pin 27 which is erected on the upper surface of the pump case 10 to prevent the rotation of the pump case 10, and the tip end thereof is slidably inserted into the hole provided on the lower surface of the horizontal portion of the center section 5. Further, when the pump case 10 performs a relief operation, in order to return the relief oil discharged from the discharge port of the charge pump 11 from the recess 5k to the oil sump, the inner peripheral surface of the recess 5k of the center section 5 and the pump case 10 are separated. Oil groove 5s and oil groove 10 on the outer peripheral surface, respectively.
s is provided.

In the third embodiment shown in FIG. 6, a protrusion 2k is integrally erected at a position on the inner bottom surface of the lower half-split case 2 on the same axial center as the input shaft 3, and on the lower surface of the pump case 10. The housing is configured to be slidably fitted into the formed pivot hole 10c so that the pump case 10 can slide in the axial direction while the housing receives the radial force generated in the pump case 10. The detent of the pump case 10 is
The same guide pin 27 as that described in the first embodiment is used.

In the fourth embodiment shown in FIG. 7, a protrusion 10k is provided on the lower surface of the pump case 10 at a position coaxial with the input shaft 3 and provided on the inner bottom surface of the lower half case 2. The pump case 10 is slidably fitted in the recess 2n.
While being axially slidable, the housing receives the radial force. Pump case 10
The detent is a guide pin 27 similar to that of the first embodiment.
It is done by.

In the fifth embodiment shown in FIGS. 8 and 9 (a), the input shaft 3 is slid in a pivot hole 10c formed in the lower surface of the pump case 10, as in the case of the first embodiment described above. By being freely inserted, the radial force of the pump case 10 is received by the center section 5 via the input shaft 3. The first detent structure of the pump case 10
Instead of the guide pins 27 of the embodiment, a protrusion 5m is integrally formed at one place on the lower surface of the horizontal portion of the center section 5, and is slidably engaged with a recess 10e provided on the outer peripheral portion of the pump case 10. It has stopped. As shown in FIG. 9B, a pair of protrusions 5m are integrally provided on the lower surface of the horizontal portion of the center section 5 at a predetermined interval, while the protrusion 10n is provided on the outer peripheral portion of the pump case 10. Projected integrally,
The rotation of the pump case 10 may be prevented by locking the protrusion 10n between the protrusions 5m.

In the sixth embodiment shown in FIGS. 10 and 11, a cylindrical projection 10p is integrally erected on the upper surface of the pump case 10 and an engaging hole 5p provided on the lower surface of the horizontal portion of the center section 5. It is slidably fitted in the pump case 1
The rotation of 0 is stopped. The radial force generated in the pump case 10 is received by the center section 5 from the pivot hole 10c formed in the lower surface of the pump case 10 via the extended end 3a of the input shaft 3 as in the case of the first embodiment. .

In the embodiment shown in FIGS. 12 and 13,
The rotation stop of the pump case 10 and the reception of the radial force have the same structure as in the sixth embodiment. Then, the oil filter 1 is attached to the bottom wall of the lower half case 2.
While the opening 2a having a size larger than the outer shape of 2 is provided,
Sealing material 12 fitted on the lower edge of the oil filter 12
The outer dimension of b is set larger than the opening 2a,
The opening 2a is closed by detachably attaching it to the outer surface of the bottom of the lower half case 2. Thus, the oil filter 12 can be easily taken out of the housing simply by unmounting the seal material 12b during maintenance and inspection. Since the lower end side of the coil spring 26 is in contact with the bottom surface of the seal material 12b, when the oil filter 12 is taken out, the coil spring 26 also comes off, and the bias to the pump case 10 is released. Here, a snap ring 50 is attached to the extended end portion 3a of the input shaft 3,
A gap is formed between the retaining ring 50 and the lower surface of the pump case 10 to allow the sliding displacement of the pump case 10 due to the relief operation described above.
As a result, even if the urging force on the pump case 10 is released, the pump case 10 is received by the retaining ring 50 after being dropped by the above-mentioned gap, so that the state in which the protrusion 10p is fitted in the engagement hole 5p is maintained. Therefore, there is no fear that the charge pump 11 will fall off the input shaft 3 and be disassembled.

When the traveling vehicle is stopped with the engine stopped on a sloping ground, if the axle drive is equipped with a hydraulic transmission, the charge pump also stops and the closed circuit is replenished with hydraulic oil. Is not done. Here, since a rotational force that tends to go down the slope is applied to the hydraulic motor by a load equivalent to the vehicle weight, the hydraulic motor acts as a pump to circulate the hydraulic oil in the closed circuit. , If the closed circuit is full of hydraulic oil,
Due to the neutral hydraulic pump blocking its circulation, the hydraulic motor will not rotate.

However, since the hydraulic oil in the closed circuit is under the pressure generated in the hydraulic motor, with the passage of time, the sliding parts of the pistons housed in the cylinder block and the cylinder block are Leakage through the rotary sliding surface with the center section, etc., and when negative pressure eventually occurs in the closed circuit, minute air in the oil expands,
The hydraulic motor freely rotates and the vehicle runs out of control. In order to prevent this runaway phenomenon (free wheel), the pump case 10 of the charge pump 11 is provided with an auxiliary oil passage 10y that communicates between the discharge port of the charge pump 11 and the oil sump. 10y is provided with a check valve 31 that opens only when the closed circuit has a negative pressure so that oil can be supplied through the auxiliary oil passage 10y.

That is, as shown in FIG. 14, the auxiliary oil passage 10 communicating with the discharge port is formed on the lower surface of the pump case 10.
y is provided as an opening, and a hard ball 31a is provided in the auxiliary oil passage 10y.
The check valve 31 is configured by inserting the cylindrical body 45 accommodating therein from above. The cylindrical body 45 is formed to have a bottom by press working, and an opening 45a for communicating the inside of the oil filter 12 and the auxiliary oil passage 10y is formed at the center of the bottom.
Is provided, and the inner peripheral edge of the opening 45a is provided with a hard sphere 31a.
Of the seat surface. A plurality of protrusions are provided in the radial direction on the peripheral edge of the upper end of the cylindrical body 45, and one of the protrusions is bent inward of the cylindrical body 45 so that the hard sphere 31a does not come out of the cylindrical body 45. There is. The other of the protrusions is bent to the outside of the cylindrical body 45 to allow the pump case 10
The cylindrical body 45, which is locked to the side surface of the groove of the charge pump 11 and receives the discharge pressure of the charge pump 11, has the auxiliary oil passage 10y of the pump case 10.
It prevents you from getting out. The other of the protrusions is bent outward and locked to the inner peripheral surface of the auxiliary oil passage 10y to prevent the cylindrical body 45 from slipping out toward the inner rotor 11a and the outer rotor 11b.

When the vehicle is stopped on a slope with the engine stopped with the movable swash plate 8 in the neutral position and negative pressure occurs in the closed circuit, the oil filter in the housing is filled with oil. The clean hydraulic oil filtered by 12 receives the negative pressure and receives the hard ball 3 of the check valve 31.
By separating 1a from the seat surface of the opening 45a of the cylindrical body 45, the discharge port when the charge pump 11 is stopped, and the hydraulic oil supply port 5c in the center section 5,
The low pressure side of the check valves C, C is opened via the oil passages 5d, 5e, and the leaked amount is replenished into the closed circuit. Therefore, the closed circuit is always filled with hydraulic oil, and the hydraulic motor M is not rotated, so that the free wheel is not generated.

[0033]

As described above, the present invention has the following advantages. Firstly, the pump case 10 for accommodating the charge pump 11 is installed on one surface of the center section 5 in a floating state in which it is biased in close contact with the coil spring 26 without being fixed by bolts. Is a coil spring 2
When the urging force of 6 or more is exceeded, the pump case 10 together with the charge pump 11 is automatically separated from the one surface of the center section 5 against the coil spring 26. As a result, a part of the pressure oil discharged from the charge pump 11 can be leaked from between the charge pump 11 and the center section 5, and the pressure oil functions as a charge relief valve. Therefore, it is not necessary to specially configure the charge relief valve inside the center section 5, and it can be manufactured at low cost.

Secondly, the coil case 2 is used as a spring for bringing the pump case 10 into close contact with one surface of the center section 5 so that the discharge port of the charge pump 11 communicates with the hydraulic oil supply port 5c opened on the one surface of the center section 5.
6 is used. The spring constant of the coil spring 26 is
Since it is smaller than the conventional corrugated annular spring, even if there is a slight error in the mounting length during assembly, it is possible to minimize variations in individual relief setting pressures and make it easy to manage. be able to.

Third, the charge pump 1 is driven by the input shaft 3.
The radial force generated in the pump case 10 when the drive shaft 1 is driven is stable and reliable in the input shaft (Claim 1), the center section (Claim 2), or the housing (Claim 3). Can be accepted. Therefore, the rotation around the input shaft 3 of the pump case is prevented, and the discharge port of the charge pump 11 and the center section 5 are prevented.
In order to maintain the communication state with the hydraulic oil supply port 5c, the radial force of the pump case 10 does not act on the locking means provided between the pump case 10 and the center section 5, and the rigidity is not so strong. The pump case 10 can be surely and smoothly moved and guided in the axial direction of the input shaft 3 even if the locking means is made of a material having a small diameter and low cost.

[Brief description of the drawings]

FIG. 1 is an overall front sectional view of a hydrostatic transmission.

FIG. 2 is an enlarged cross-sectional view of a main part of the charge pump showing the first embodiment of the present invention.

FIG. 3 is an exploded perspective view of the charge pump for the center section.

FIG. 4 is an enlarged sectional view of a main part of a charge pump showing a second embodiment of the present invention.

FIG. 5 is a rear view of the pump case also installed in the center section.

FIG. 6 is an enlarged cross-sectional view of the main parts of the charge pump showing the third embodiment of the present invention.

FIG. 7 is an enlarged cross-sectional view of a main part of a charge pump showing a fourth embodiment of the present invention.

FIG. 8 is an enlarged sectional view of a main part of a charge pump showing a fifth embodiment of the present invention.

FIG. 9 (a) is a rear view of the pump case showing the rotation stopping means of the pump case with respect to the center section,
FIG. 6B is a rear view of the pump case showing another rotation stopping means of the pump case with respect to the center section.

FIG. 10 is an enlarged sectional view of a main part of the charge pump showing the sixth embodiment of the present invention.

FIG. 11 is a front view of the pump case.

FIG. 12 is an enlarged cross-sectional view of a main part of a charge pump in which an oil filter is disposed and the charge pump can be inserted and removed without dropping the charge pump from the housing.

FIG. 13 is an exploded perspective view of the charge pump for the center section.

FIG. 14 is an enlarged cross-sectional view of a main part of a check valve housed in a pump case.

FIG. 15 is a plan sectional view of a center section.

[Explanation of symbols]

 P hydraulic pump M hydraulic motor 1 upper half case 2 lower half case 2k protrusion 2n recess 3 input shaft 5 center section 5k recess 5m protrusion 10 pump case 10c pivot hole 10e recess 10k protrusion 11 charge pump 27 guide pin

Claims (3)

[Claims] 1. A structure in which a charge pump 11 for replenishing hydraulic oil driven by an input shaft 3 of an HST type transmission is installed on one surface of a center section 5 inside a housing of the HST type transmission. A coil spring 26 is arranged between the pump case 10 accommodating the oil and the inner surface of the housing to bring the pump case 10 into close contact with one surface of the center section 5 to open the discharge port of the charge pump 11 on the one surface of the center section 5. While being connected to the replenishment port 5c, the locking means provided between the pump case 10 and the center section 5 makes it unrotatable around the input shaft 3 and movable in the axial direction of the input shaft 3. At the same time, the extended end portion 3a of the input shaft 3 is fitted into the pivot hole 10c provided in the pump case 10 to A charge pump for an HST type transmission, characterized in that the input shaft 3 receives the radial force of. 2. A pump case for accommodating the charge pump 11 in a configuration in which a charge pump 11 driven by an input shaft 3 of an HST transmission is installed on one surface of a center section 5 inside a housing of the HST transmission. A coil spring 26 is disposed between the housing 10 and the inner surface of the housing, the pump case 10 is brought into close contact with one surface of the center section 5, and the discharge port of the charge pump 11 is opened on the one surface of the center section 5.
While being communicated with the pump case 10, the locking means provided between the pump case 10 and the center section 5 is used to
Is configured to be non-rotatable around the input shaft 3 and movable in the axial direction of the input shaft 3, and the center section 5
A charge pump for an HST transmission, wherein one end side of a pump case 10 is slidably fitted into a recess 5k provided on one surface to receive the radial force of the pump case 10 at the center section 5. 3. A pump case for accommodating the charge pump 11 in a structure in which a charge pump 11 driven by an input shaft 3 of an HST transmission is installed on one surface of a center section 5 inside a housing of the HST transmission. A coil spring 26 is disposed between the housing 10 and the inner surface of the housing, the pump case 10 is brought into close contact with one surface of the center section 5, and the discharge port of the charge pump 11 is opened on the one surface of the center section 5.
While being communicated with the pump case 10, the locking means provided between the pump case 10 and the center section 5 is used to
Is configured to be non-rotatable around the input shaft 3 and movable in the axial direction of the input shaft 3, and one of the surfaces of the pump case 10 and the housing facing each other of the input shaft 3 is configured to be movable. A protrusion 10k or a protrusion 2k located on the virtual axis is provided, and a recess 2n or a pivotal support hole 10c is provided on the other surface, and the respective protrusions 10k and 2k and the recess 2n or the pivotal support hole 1
0c is slidably fitted to receive the radial force of the pump case 10 in the housing.
Charge pump for ST type transmission.