JPH0914154A - Gear pump or motor - Google Patents

Abstract

PURPOSE: To effectively prevent suction of air at a shaft seal housing and to reliably prevent the occurrence of a problem, such as the generation of vibration and noise of a pump and the occurrence of defective delivery. CONSTITUTION: A check valve 10 opening only when a differential pressure between the internal pressure of a shaft seal housing 7 and a pressure in a low pressure chamber 8 attains a predetermined cracking pressure is located in a feedback passage 8a through which the interior of the shaft seal housing 7 and the low pressure chamber 8 are intercommunicated. Thereby, the internal pressure of the shaft seal housing 7 is reliably prevented from reduction to a value lower than a working resisting pressure and simultaneously, oil after lubrication of a bearing is properly returned to the low pressure chamber 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gear pump / motor which can be used as a fluid source for various machines including agricultural machines such as tractors and combine harvesters, general industrial machines such as table lifters and mini excavators. (Hereinafter, the hydraulic pump will be described as a representative).

[0002]

2. Description of the Related Art Taking a medium-pressure or high-pressure gear pump as an example, this gear pump has a pair of gears which are housed in mesh with each other in a hole provided in a body and side surfaces of these gears. A movable side plate having a pressure balance groove for sliding sealing, a cover for sealing the body hole, a drive shaft and a driven shaft for supporting the both gears in a bearing hole provided in the cover through the side plate. , A shaft seal housing disposed at the drive shaft penetrating end of the cover. Then, when both gears are driven to rotate in reverse synchronously via the drive shaft, the side where the teeth of both gears are separated becomes a low pressure chamber,
The side where the teeth mesh with each other becomes a high-pressure chamber, and oil is continuously transferred from the low-pressure chamber to the high-pressure chamber, at which time part of the oil is circulated in the bearing hole to self-lubricate the bearing. It is configured.

By the way, the conventional structure has a problem that the shaft seal body is apt to be deteriorated and damaged early. Specifically, the pressure-balance type movable side plate is provided with a pressure balance groove on the side surface opposite to the gear side along the high pressure region. The side surface of the gear is slid-sealed and pressure-balanced with the fluid pressure urging force from the high-pressure region, and the volume efficiency is improved. If the pressing force at that time is too strong, the sliding resistance increases, resulting in a loss in mechanical efficiency. Therefore, the pressing force is not set to a very large value. Therefore, the oil leakage through the sliding surface is scheduled to some extent from the beginning.
Further, after the oil flows through the sliding surface, it also serves as a lubricating oil that enters the bearing hole and lubricates the bearing. Therefore, there is a surface that is actively used to have a self-lubricating function. However, since the amount of oil leakage is quite large, the amount of oil that reaches the shaft seal housing via the bearing hole becomes excessive, and excessive pressure is applied to the shaft seal body, which tends to cause early deterioration and damage. Is occurring.

Therefore, conventionally, a return passage from the shaft seal housing portion to the low pressure chamber is processed so that the oil reaching the shaft seal housing is returned to the low pressure chamber.

[0005]

However, when such a return passage is provided, the pressure in the shaft seal housing becomes substantially the same as the pump suction pressure, so that the suction condition of the shaft seal body or the hydraulic circuit is good or bad. Easily affected by. For example, if the suction pressure becomes negative and the inside of the shaft seal housing falls below the lower limit of seal withstand pressure, the outside air is sucked in from the seal lip of the shaft seal body, and this air However, there is a problem in that it causes problems such as noise, vibration and defective discharge pressure.

The present invention has been made in view of the above problems, and a gear pump or motor which effectively prevents air from being sucked into the shaft seal housing without impairing the lubricating function and the recirculating function of oil. Is intended to provide.

[0007]

In order to achieve the above object, the present invention employs the following configuration.

That is, the gear pump or the motor according to the present invention includes a pair of gears that are housed in a hole provided in the body in mesh with each other, and a cover that covers the body hole.
A drive shaft and a driven shaft for bearing the both gears in a bearing hole provided in the cover, a shaft seal housing arranged at the drive shaft penetrating end of the cover, and a feedback for communicating the inside of the shaft seal housing with the low pressure chamber. A part of the oil transferred from the low pressure chamber to the high pressure chamber is circulated in the bearing hole, and is then returned to the low pressure chamber through the shaft seal housing and the return passage. The return passage may be provided with a check valve that opens only when the pressure difference between the shaft seal housing internal pressure and the low pressure chamber reaches a predetermined cracking pressure.

[0009]

With such a structure, when the gear pump is started, oil flows out from the high pressure side through the bearing hole into the shaft seal housing. At this time, depending on the suction condition, the lower the pressure in the low pressure chamber, the larger the differential pressure between the upstream side and the downstream side of the check valve. Then, when the differential pressure reaches a predetermined cracking pressure, the check valve is opened and the shaft seal housing and the low pressure chamber are communicated with each other. That is, depending on the setting of the cracking pressure, even if the pressure in the low-pressure chamber becomes a negative pressure to some extent, the check valve can be normally kept closed, and the oil that flows out from the bearing hole can seal the shaft seal. Only when the pressure in the housing becomes high, it is possible to intermittently press the check valve into the oil to open it and return it to the low-pressure chamber, which causes the shaft seal housing to be stepped down and the check valve to be closed again. it can. With this, the internal pressure of the shaft seal housing does not continue to fall below the lower limit of the withstand pressure of the shaft seal body, and the intake of air into the shaft seal housing is reliably prevented. Conversely, depending on the setting of the cracking pressure, it becomes possible to use the shaft seal body under conditions that exceed the original pressure resistance performance.

[0010]

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

As shown in FIG. 1, this gear pump comprises a body 1 and a front cover 2 which are integrally formed by a die casting method, and the inner end of a spectacle-shaped hole 11 provided in the body 1 is formed. The lid is sealed by the front cover 2 from the beginning of molding. The front cover 2 is provided with bearing holes 21 and 22 at two locations.
Bushings 21a and 22a are fitted in the. And
The first movable side plate 31 is accommodated at the inner end of the body hole 11,
After that, the drive shaft 41 to which the drive gear 4 is fixed in advance and the driven shaft 51 to which the driven gear 5 is fixed are passed through the movable side plate 31 of the bushes 21a, 22 of the front cover 2.
The gears 4 and 5 are accommodated in the body hole 11 in a meshed state with each other. Further, the other second movable side plate 32 paired with the first movable side plate 31 is arranged on the outer end face of the body 1, and in this state, the outer end face of the body 1 is covered with the rear cover 6. It's sealed. This rear cover 6 is also provided with bearing holes 61 and 62 at two locations, and bushes 61 are provided in these bearing holes 61 and 62.
a and 62a are fitted so that the drive shaft 41 and the driven shaft 52 are supported by the bushes 61a and 62a in a lid-sealed state. A shaft seal body 7a is provided at the drive shaft penetrating end of the front cover 2 to prevent the oil leaking through the inner periphery of the bush 21a from leaking to the outside.
The shaft seal housing 7 having the inside is incorporated. In addition, the movable side plates 31 and 32 described above are provided with pressure balance grooves 31a and 32a in their high-pressure-corresponding regions on their counter gear side surfaces 31b and 32b, and these pressure balance grooves 31a and 32a are provided on the gear side surfaces 31c and 32c. By introducing high-pressure oil from above, the movable side plates 31 and 32 are pressed against the side surfaces 4a and 5a of the gears 4 and 5, and as a result, the hydraulic urging force from the gears 4 and 5 is balanced with the pressure. There is. Thereby, the mechanical sliding resistance is kept at a small value, and the gear side surfaces 4a, 5a are slidably sealed to improve the volumetric efficiency.

Then, through the drive shaft 41, both gears 4, 5
2 is driven in a synchronous reverse rotation, the internal space of the body on the side where the teeth of both gears 4 and 5 gradually separate from each other becomes the low-pressure chamber 8 as shown in FIG. 2, and the internal space of the body on the side where the teeth gradually mesh with each other. The high-pressure chamber 9 is formed, and oil is continuously transferred from the low-pressure chamber 8 to the high-pressure chamber 9, and at the same time, a part of the oil is circulated to the inner periphery of the bushes 21a, 61a, 22a, 62a described above. The sliding surfaces between the bushes 21a and 61a and the drive shaft 41 and the sliding surfaces between the bushes 22a and 62a and the driven shaft 51 are self-lubricated. That is, this self-lubricating system passage is formed from the tooth groove in which high pressure oil is confined to the gear side surface 4
a, 5a and gear side surfaces 31c, 3 of the movable side plates 31, 32
The oil leaked to the sliding surface with 2c is replaced by the bushes 21a, 61
It is made to flow into the inner circumferences of a, 22a, and 62a, flow along the drive shaft 41 or the driven shaft 51, and then be returned to the low-pressure chamber 8. More specifically, in the drive shaft 41, the oil flowing along the bush 21a once reaches the shaft seal housing 7, but the oil flows into the low pressure chamber 8 in the shaft seal housing 7 in advance as shown in FIG. The return passage 8a is perforated so that oil reaching the shaft seal housing 7 can be returned to the return passage 8a.
The low pressure chamber 8 is circulated via a.

In this structure, the shaft seal housing 7 is further provided in the return passage 8a in this embodiment.
A check valve 10 is provided which opens only when the differential pressure between the internal pressure and the low pressure chamber 8 reaches a predetermined cracking pressure.

More specifically, FIG. 3 shows a cross section taken along a plane passing through the axis of the gear 4 and the center of the low pressure chamber 8, and the check valve 10 is incorporated in this cross section. A seat portion 10a mounted in the return passage 8a of the front cover 2, and a steel ball 10b arranged at a position on the low pressure chamber 8 side of the seat portion 10a and detachable from the seat portion 10a, Ball retainer 10 that guides and holds this steel ball 10b so that it can move freely.
c, and a spring 10d housed in the ball retainer 10c and elastically biasing the steel ball 10b toward the seat portion 10a.

With this structure, when the gear pump is operated, oil flows from the high pressure side into the shaft seal housing 7 through the inner periphery of the bush 21a provided in the bearing hole 21. At this time, depending on the suction condition, the low pressure chamber 8
The lower the pressure is, the larger the differential pressure between the internal pressure of the shaft seal housing 7 and the low pressure chamber 8, that is, the differential pressure between the upstream side and the downstream side of the check valve 10. Then, the differential pressure is a predetermined cracking pressure (spring pressure).
Steel ball 10b reaches the seat portion 1 when
0a is opened, the check valve 10 is opened, and the shaft seal housing 7 and the low pressure chamber 8 communicate with each other. That is, depending on the setting of the cracking pressure, the check valve 10 can be kept closed even when the pressure in the low-pressure chamber 8 becomes a negative pressure to some extent, and the oil flowing out from the bearing hole 21 causes the shaft to be closed. Only when the internal pressure of the seal housing 7 becomes high, the oil is intermittently pushed to open the check valve 10 and flow back to the low pressure chamber 8, and when the pressure inside the shaft seal housing 7 is reduced, the check valve 10 is closed again. can do. In this way, the check valve 10 does not continue to open until the internal pressure of the shaft seal housing 7 falls below the lower limit of the withstand pressure of the shaft seal body 7a, and the check valve 10 is inserted into the shaft seal housing 7 through the seal lip portion of the shaft seal body 7a. The air itself can be reliably prevented from being sucked.

Explaining the above based on a concrete design example, the shaft seal body 7a has a working pressure resistance of 3 kgf / cm ²
Assuming that -15 cmHg is used, set the cracking pressure of the check valve 10 to 1 kgf / cm ² ,
And the suction pressure of the low pressure chamber 8 is -30 cmHg (about -0.41
Considering the case where the pressure decreases to kgf / cm ² ), since the pressure limit of the shaft seal body 7a is normally exceeded, air is sucked from the seal lip portion, but in this embodiment, the shaft seal housing 7 Internal pressure is 0.59
Unless the pressure exceeds kgf / cm ² , the differential pressure does not reach 1 kgf / cm ² , so the valve 10 is not opened. Therefore,
Since no negative pressure is applied to the shaft seal main body 7a, the problem of air suction, and consequently the problems of pump vibration and noise and defective discharge pressure derived therefrom, can be effectively solved.

The specific construction of each part is not limited to the above-mentioned embodiment, and various modifications can be made without departing from the spirit of the present invention. In particular, the cracking pressure is set in consideration of the withstand pressure of the shaft seal body and the like, and is set purposely.

[0018]

As described above, the gear pump of the present invention has a structure in which the oil that reaches the shaft seal housing after being used for bearing lubrication is returned to the low pressure chamber through the return passage. A check valve is installed in the passage, and by setting the cracking pressure for this check valve, a predetermined differential pressure is secured between the shaft seal housing and the low pressure chamber, and the internal pressure of the shaft seal housing is prevented from dropping below the pressure resistance. It was done. For this reason, it is possible to effectively prevent the intake of air in the shaft seal housing without impairing the oil lubrication function and the recirculation function, and it is possible to reliably solve problems such as pump vibration, noise, and suction failure. The effect is played. Furthermore, depending on the setting of the cracking pressure, it becomes possible to use the shaft seal body under conditions that exceed the original pressure resistance performance.

[Brief description of the drawings]

FIG. 1 is an overall vertical sectional view showing one embodiment of the present invention.

FIG. 2 is a sectional view taken along line II-II in FIG.

FIG. 3 is a sectional view of a main part of the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Body 2 ... Front cover 4, 5 ... Gear 6 ... Rear cover 7 ... Shaft seal housing 8 ... Low pressure chamber 8a ... Return passage 9 ... High pressure chamber 10 ... Check valve 11 ... Body hole 21, 22, 61, 62 ... Bearing hole 41 ... Drive shaft 51 ... Drive shaft

Claims (1)

[Claims] 1. A pair of gears housed in a hole provided in a body in mesh with each other, a cover for covering the body hole, and a drive shaft for bearing both gears in a bearing hole provided in the cover. And a driven shaft, a shaft seal housing disposed at a drive shaft penetrating end of the cover, and a return passage communicating the inside of the shaft seal housing with the low pressure chamber. A structure in which a part of the transferred fluid is circulated to the bearing hole and then returned to the low pressure chamber via the shaft seal housing and the return passage, wherein the return passage has the internal pressure of the shaft seal housing and the low pressure chamber. A gear pump or a motor, wherein a check valve that opens only when a pressure difference between the gear pump and the cracking pressure reaches a predetermined cracking pressure is provided.