JP4061847B2 - Gear pump - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a circumscribed gear pump that performs pumping action by rotation of a pair of gears that mesh with each other.
[0002]
[Prior art and problems to be solved by the invention]
Conventionally, gear pumps have been used in various industrial fields because they can have a large capacity while having a simple structure.
As a structure of this type of gear pump, a pair of side plates are fitted into a cavity (cavity) inside a housing to define a gear chamber, and a pair of gears meshing with each other are accommodated inside the gear chamber. In general, the support shaft is supported by a support hole formed in each side plate, and a working fluid suction chamber and a discharge chamber are formed inside the gear chamber with the meshing position of both gears interposed therebetween.
[0003]
Since it is necessary to completely separate the discharge pressure and the suction pressure inside the gear pump, the outer periphery of the gear and the inner peripheral surface of the main body cylinder corresponding to the cavity facing this (hereinafter also referred to as the inner peripheral surface of the cavity for convenience) The pressure is divided at each of the contact portions, the sliding portions between the side surfaces of the gear and the side surfaces of the side plates opposed to the contact portions.
Specifically, the side plate is structured to float in the axial direction, and the pressure in the gear chamber is guided to a part of the back surface of the side plate (corresponding to a region partitioned by a substantially 3-shaped rubber seal). Yes. When a high pressure is generated in the gear chamber, the side plate is pressed against the side surface of the gear due to the difference in pressure receiving area on both side surfaces of the side plate. Further, when a low pressure is generated, the side plate is pressed against the gear side by the elastic repulsive force of a rubber seal having a substantially 3 shape that presses the back surface of the side plate.
[0004]
First, with reference to FIG. 7A, which is a schematic diagram, a case will be described in which each gear rotates in the normal rotation direction (that is, rotates forward). In the figure, white arrows indicate the flow of oil, and solid arrows indicate the direction of force received by the gears 73 and 74 due to internal pressure. The alternate long and short dash line indicates the cavity inner peripheral surface 76 before use.
At the time of forward rotation, the pressure on the discharge port 71 side becomes higher than the pressure on the suction port 72 side, but the gears 73 and 74 are loosely fitted to the inner peripheral surface 76 of the cavity that forms the double body of the housing 75. Therefore, the gears 73 and 74 that have received the internal pressure are biased toward the suction port 72 by an amount corresponding to the internal gap S of the bearing 77 that supports the support shafts 73a and 74a, so that the outer circumferences of the gears 73 and 74 are A region around the suction port 72 in the cavity inner peripheral surface 76 is brought into contact with the cavity inner peripheral surface 76.
[0005]
That is, the housing 75 generates an interference area 78 (hatched area in the figure) with the gears 73 and 74 and is scraped off by the gears 73 and 74. The scraped trace 79 is called a gear track. It is out. The high pressure on the discharge port 71 side and the low pressure on the suction port 72 side are partitioned through contact portions between the gears 73 and 74 corresponding to the interference area 78 and the housing 75.
On the other hand, although not shown, a seal for the drive shaft for driving the drive side gear is used which has an excellent sealing property equivalent to an oil seal, and communicates with the suction port side as the internal pressure of this seal. By securing the pressure of the suction port through the oil passage, the seal is prevented from receiving an excessive differential pressure.
[0006]
In such a gear pump, there is no problem when the gears 73 and 74 are rotating in the normal direction as shown in FIG. However, there is a case where the gear is reversely rotated due to some mistake, for example, when the motor is installed with the wrong polarity when assembled. In this case, as shown in FIG. 7 (b), the gears 73 and 74 are biased toward the discharge port 71 side where the pressure is low, and the gear track 81 is formed with the interference zone 80 with respect to the cavity inner peripheral surface 76. become. The low pressure on the discharge port 71 side and the high pressure on the suction port 72 are partitioned through a contact portion corresponding to the interference zone 80, and the high pressure of the suction port 72 is loaded into the seal of the drive shaft. As a result, the seal may be damaged.
[0007]
Therefore, when the internal pressure of the seal becomes high, it is possible to open the high pressure via an oil passage with a valve (check valve or relief valve) communicating with the discharge port on the low pressure side. . However, the addition of the valve structure increases the size and the manufacturing cost.
The present invention has been made in view of the above problems, and an object of the present invention is to provide a gear pump that is capable of preventing problems during reverse rotation while being small and inexpensive.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides an external gear pump including a pair of meshing gears housed in a cavity of a housing. at least the discharge port side portion of the peripheral surface, Ri Oh provided thinned portion for avoiding interference with the addendum orbital circle of the gear during reverse rotation, by the thinned portion is provided, the gears When the gear rotates in reverse, a gap is formed between the tooth tip raceway circle of each gear and the inner peripheral surface of the main body cylinder so that the low pressure on the discharge side and the high pressure on the suction port side are not partitioned from each other. In addition, a contact area is not formed between the tooth tip raceway circle of each gear and the inner peripheral surface of the main body cylinder .
[0009]
In the present invention, even if the gear is rotated in the reverse direction and the gear is pushed to the discharge port side where the pressure is low, the contact area between the gear and the inner peripheral surface of the main body cylinder is not formed. can do. Since it is only necessary to provide a meat theft, there is no increase in size and the cost does not increase.
Furthermore, by increasing the bearing clearance of the gear support shaft, it is possible to increase the amount of leakage due to the meat stealing portion, and to reliably prevent pressure increase during reverse rotation.
[0010]
Also, the pair of gears includes a driving gear and a driven gear, when the seal for sealing between the shaft insertion hole of the support shaft and the housing of the drive gear is provided, the reverse rotation gears In this case, the contact area is not formed between the tooth tip raceway circle of each gear and the inner peripheral surface of the main body cylinder by the action of the meat stealing portion, so that it is possible to prevent pressurization that damages the seal. it can.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Preferred embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a sectional view of a gear pump according to an embodiment of the present invention, and FIG. 2 is a sectional view taken along the line II-II in FIG. 3 is a cross-sectional view taken along line III-III in FIG. 1, and FIG. 4 is a cross-sectional view taken along line IV-IV.
Referring to FIG. 1, in this gear pump, both sides of a main body cylinder 2 having a cavity 1 having an oval cross section penetrating through a central portion thereof are closed by a pair of cover plates 3 screwed so as to cover the entire surface thereof. A housing 4 is provided. Inside the housing 4, a gear chamber 6 is defined between a pair of side plates 5 and 5 made of aluminum alloy that are fitted from both sides of the cavity 1. A pair of drive gear 7 and driven gear 8 are arranged. Reference numeral 9 denotes a seal which is accommodated in the annular groove of the lid plate 3 and is interposed between the lid plate 3 and the main body cylinder 2 to seal the gear chamber 6. A seal 10 is housed in the housing groove of the side plate 5 and partitions the space between the opposing side plate 5 and the cover plate 3 in the gear chamber 6 into a low pressure side and a high pressure side region.
[0012]
The support shafts 7a and 8a of the drive gear 7 and the driven gear 8 are respectively positioned on the arc centers of the arcs on both sides of the gear chamber 6 having an oval cross section, and are laid in parallel to each other. That is, the support shafts 7a and 8a are supported at both ends by support holes 11 and 12 as bearings formed in pairs on the side plates 5, respectively.
One support shaft 7a supported by the pair of support holes 11 is extended to the outside through one lid plate 3, and is driven to rotate by a driving force from a motor (not shown) transmitted to the extended end. It constitutes an axis. A drive gear 7 is attached to the support shaft 7a so as to be integrally rotatable inside the gear chamber 6. An oil seal 13 is disposed at a portion where the support shaft 7a penetrates the cover plate 3.
[0013]
The other support shaft 8 a supported by the pair of support holes 12 constitutes a driven shaft having a shaft end in the support hole 12 of each side plate 5. A driven gear 8 is attached to the support shaft 8 a inside the gear chamber 6. When the driven gear 8 is mounted on the support shaft 8a, the rotation around the axis may be restricted or the rotation around the axis may be allowed. The driven gear 8 meshes with the drive gear 7 in a plane including the axis of both the support shafts 7a, 8a, and with the support shaft 8a (or the support shaft 8a) as the drive gear 7 driven by the support shaft 7a rotates. It is designed to follow and rotate (without rotation).
[0014]
In FIG. 2, the rotation direction of the drive gear 7 and the driven gear 8 interlocked with this is indicated by arrows. The rotation directions of the gears 7 and 8 are predetermined and rotate in opposite directions. A state in which the gears 7 and 8 are rotating in a predetermined rotation direction is referred to as normal rotation. A suction chamber 14 is formed on the rotation direction side, and a discharge chamber 15 is formed on the counter-rotation direction side on both sides of the meshing position of both gears 7 and 8. The suction chamber 14 and the discharge chamber 15 are respectively connected to a suction destination and a discharge destination (not shown) outside the housing 4 through a suction port 16 and a discharge port 17 that open to corresponding positions of the main body cylinder 2. .
[0015]
As will be described in detail later, the feature of the present embodiment is that, as shown in FIG. 6B, the inner peripheral surface 18 of the cavity 1 facing the tooth tip circles 7b and 8b of the gears 7 and 8, respectively. The meat stealing portion 19 for avoiding interference with the tooth tip race circles 7b and 8b of the gears 7 and 8 at the time of reverse rotation is provided at least on the discharge port side.
In FIG. 3, a clearance groove 20 extending to the suction chamber 14 side and a clearance groove 21 extending to the discharge chamber 15 from the meshing position of both the gears 7 and 8 are formed on the gear side surface 5 a of the side plate 5. These escape grooves 20 and 21 prevent the occurrence of so-called confinement in which fluid is confined in a closed region formed by each side plate 5 and each meshing gear tooth at the meshing position of both gears 7 and 8. Is. Both escape grooves 20, 21 are provided so as to avoid the meshing center position of both gears 7, 8, and a predetermined distance is secured between them. This is to prevent both the escape grooves 20 and 21 from communicating with each other because the suction chamber 14 side and the discharge chamber 15 side are communicated with each other and cannot perform the pump function. The gear side surface 5a is formed with a communication groove 22 for communicating the support holes 11 and 12 with the suction chamber 14 side.
[0016]
On the other hand, in FIG. 4, the above-described seal 10 is accommodated in a substantially 3-shaped seal groove on the opposite-gear side surface 5 b of the side plate 5, and the side plates 5 facing each other with the seal 10 as a boundary. And the cover plate 3 is partitioned into a low-pressure side space communicating with the suction chamber 14 side and a high-pressure side space communicating with the discharge chamber 15 side. As described above, the low-pressure working fluid and the high-pressure working fluid act as back pressure on the side opposite to the gear side surface 5b, which is the back surface of the side plate 5, in a state of being partitioned by the seal 10, and this acts on the side plate 5. Since the load is applied according to the discharge pressure, the gap between the side plate 5 and the both gears 7 and 8 is maintained with high accuracy. As a result, the pump efficiency at high pressure can be maintained high. Further, a pair of communication grooves 23 are formed in the counter gear side surface 5b to communicate the support holes 11 and 12 with the suction chamber 14 in the low pressure side space.
[0017]
With such a configuration, the working fluid introduced into the suction chamber 14 through the suction port 20 is received between the teeth of the drive gear 7 and the driven gear 8 facing the suction chamber 14, and is rotated by the rotation of both the gears 7 and 8. These are conveyed in a sealed state between each tooth and the inner peripheral surface of the main body cylinder 2, and sent out to the discharge chamber 15. The drive gear 7 and the driven gear 8 that have finished feeding to the discharge chamber 15 are directed toward the suction chamber 14 through the meshing positions of the two gears 7 and 8, and receive the working fluid in the suction chamber 14 again to discharge the discharge chamber. Sends out to the 15 side.
[0018]
On the other hand, referring to FIG. 5 which is a partially broken exploded perspective view of the main part of the gear pump, the sliding surfaces between the support holes 11 and 12 and the respective support shafts 7a and 8a are separated from the suction chamber 14 on the low pressure side. The working fluid is circulated. That is, since the spiral grooves 11b and 12b are formed in the inner peripheral surfaces 11a and 12a of the support holes 11 and 12, the side surfaces 5a of the side plate 5 are rotated by rotating the support shafts 7a and 8a. The working fluid on the suction chamber 14 side is introduced into the support holes 11 and 12 through the communication groove 22 (or 23) formed in (or 5b), and is formed on the other side surface 5b (or 5a) of the side plate 5. Then, the air is returned to the suction chamber 14 through the communication groove 23 (or 22). Note that the spiral grooves 11b and 12b of the support holes 11 and 12 are all formed in the same direction, and both the gears 7 and 8 rotate in the reverse direction. Therefore, in FIG. 1 and FIG. The working fluid is introduced into the holes 11 and 12 from the non-gear side surface 5b of the side plate 5 (indicated by white arrows in FIG. 5), and into the lower right and upper left support holes 11 and 12, the side plate The working fluid is introduced from the gear side surface 5a (shown by a solid arrow in FIG. 5).
[0019]
Next, referring to FIG. 6A, which is a schematic diagram, the relationship between the inner peripheral surface 18 of the cavity 1 and the tooth tip circles 7b and 8b of the gears 7 and 8 when the gears 7 and 8 rotate in the forward direction. explain. At the time of forward rotation of the gear, the gears 7 and 8 that have received the internal pressure are biased toward the suction port 16 by an amount corresponding to the internal gap S of the bearings 11 and 12 that support the support shafts 7a and 8a. 8 tooth tip circles 7b, 8b form a contact region 24 around the suction port 16 on the inner peripheral surface 18 of the cavity 1, and a high pressure on the discharge port 17 side and a low pressure on the suction port 16 side through the contact region 24. And will be partitioned. This state is the same as in the prior art.
[0020]
If the gears 7 and 8 are rotated in the reverse direction, as shown in FIG. 6B, the gears 7 and 8 are pushed toward the discharge port 17 where the pressure is low (in the figure, black Since the meat stealing portion 19 is provided, no contact area is formed between the tooth tip circles 7 b and 8 b of the gears 7 and 8 and the inner peripheral surface 18 of the cavity 1. Therefore, it is possible to prevent the boosting that damages the seal 13. Moreover, since it is only necessary to provide the meat stealing portion 19, there is no increase in size and the cost does not increase.
[0021]
As the meat stealing portion 19, referring to FIG. 6 (b), providing a clearance amount B of 0.1 mm or more between the tooth tip circles 7 b and 8 b corresponding to the reverse rotation ensures a leakage amount. Therefore, it is preferable for suppressing the pressure increase. For example, it may be about 1 to 2 mm.
In addition, by increasing the bearing clearance S between the support shafts 7a and 8a of the gears 7 and 8, it is possible to increase the amount of leakage due to the meat stealing portion 19, and to reliably prevent pressure increase during reverse rotation.
[0022]
Further, as shown in FIG. 6A, the meat stealing portion 19 is formed so as to start from the intersection of the discharge port 17 and the inner peripheral surface 18 of the main body cylinder 2 . The center angle A of the gear corresponding to the area where the meat stealing portion 19 is formed is a contact area between the tooth tip circles 7b and 8b of the gears 7 and 8 and the inner peripheral surface 18 of the main body cylinder 2 during forward rotation. In order to secure 24, at least the rotation angle of the gears 7 and 8 requires an angle corresponding to one pitch (for example, about 30 °) .
[0023]
The meat stealing portion 19 may be molded simultaneously with the casting of the main body cylinder 2 or may be milled after molding.
The present invention is not limited to the above embodiment, and various modifications can be made within the scope of the present invention.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a gear pump according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view taken along the line II-II in FIG. 1, with hatching omitted.
3 is a cross-sectional view taken along line III-III in FIG.
4 is a cross-sectional view taken along line IV-IV in FIG.
FIG. 5 is a partially broken exploded perspective view of a main part of the gear pump.
FIGS. 6A and 6B are schematic diagrams showing the relationship between the gear tip circle and the inner circumference of the cavity during forward and reverse rotations of the gear, respectively.
FIGS. 7A and 7B are schematic views showing the relationship between the tooth tip circle of the gear and the inner circumference of the cavity when the gear of the conventional gear pump is rotated forward and backward, respectively.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Cavity 2 Body cylinder 3 Cover plate 4 Housing 5 Side plate 6 Gear chamber 7 Drive gear 8 Drive gear 7a, 8a Support shaft 7b, 8b Tooth tip track circle 10 Seal 11, 12 Support hole 11a, 12a Inner peripheral surface (bearing)
16 Suction port 17 Discharge port 18 Inner peripheral surface 19 Meat stealing part A Center angle

Claims (2)

In a circumscribed gear pump comprising a pair of meshing gears housed in a cavity of a housing,
Meat stealing to avoid interference with the gear tip orbit circle of each gear during reverse rotation at least on the discharge port side portion of the inner peripheral surface of the main body cylinder corresponding to the cavity facing the gear tip orbit circle of each gear Has a section,
By providing the meat stealing portion, when each gear rotates in the reverse direction, a low pressure on the discharge side and a high pressure on the suction port side are generated between the tooth tip raceway circle of each gear and the inner peripheral surface of the main body cylinder. A gear pump characterized in that gaps are formed so as not to be separated from each other and no contact area is formed between the tooth tip circle of each gear and the inner peripheral surface of the main body cylinder. In Claim 1 , the pair of gears includes a drive gear and a driven gear,
A gear pump characterized in that a seal is provided for sealing between a support shaft of the drive gear and a support shaft insertion hole of the housing.

Images