JPH03213684A - Gear pump - Google Patents

Abstract

PURPOSE:To restrain reverse flow passage through a clearance between a drive gear/a driven gear and the inner face of a casing by raising pressure on the back side of the drive gear and the driven gear through use of subsidiary gears. CONSTITUTION:A back chamber 13 is formed on the suction side of a casing 1, and a part of liquid sucked from suction ports 2 is fed to this back chamber 13 with subsidiary gears 10, 11 to raise the back pressure of a drive gear 4 and a driven gear 5. Hereby, pressure difference between the suction side and the discharge side is minified, and hence reverse flow is increased not so much even if the clearance between the casing 1 and the gears increases a little. Consequently, it is unnecessary to set the clearance very small, friction loss is decreased, and increasing degree of reverse flow due to progress of wear is also minified.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a gear pump in which a pair of driving gears and driven gears that mesh with each other are housed in a casing having a liquid suction port and a liquid discharge port.

[Conventional technology]

FIG. 3 is a longitudinal cross-sectional view showing the configuration of a conventional gear pump, in which a pair of driving gears 4 and driven gears 5 that mesh with each other are housed in a casing 1 having a liquid suction port 2 and a liquid discharge port 3. . The drive gear 4 rotates together with the drive shaft 6 in the direction of the arrow, and the driven gear 5 meshing therewith is supported by the support shaft 7 and rotates in the direction of the arrow. As a result, the liquid sent from the suction port 2 fills the cutting edge space, moves along the inner surface of the casing 1 as shown by the broken line arrow, and is sent out from the discharge port 3.

[Problem to be solved by the invention]

In such a gear pump, a slight gap is provided between the tooth tips and side surfaces of the gears 4 and 5 and the inner surface of the casing 1. If this gap is large, backflow from the high pressure side (discharge side) to the low pressure side (suction side) will increase and efficiency will decrease, but if it is too small, friction loss due to liquid viscosity will increase and efficiency will also decrease. . Therefore, the above-mentioned gap is appropriately determined depending on the usage conditions (viscosity, pressure, rotation speed, pump size, etc.). However, if the viscosities of the liquids do not match, or if the gap cannot be maintained properly due to progressive wear, it is inevitable that backflow will increase and friction loss will increase, resulting in a decrease in efficiency. . When the backflow increases, gear 1
The amount of discharge per revolution decreases, and the relationship between the number of rotations and the amount of discharge becomes more likely to change due to load fluctuations. An object of the present invention is to provide a gear pump that solves the above problem by suppressing backflow due to the gap between the gear and the casing.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a gear pump in which a pair of driving gears and a driven gear that mesh with each other are housed in a casing having a liquid suction port and a liquid discharge port. and a pair of auxiliary gears that rotate in mesh with the driven gears, respectively, to form a back chamber between these four gears, and a portion of the liquid sucked from the suction port is sent to the back chamber by the auxiliary gears. It shall be structured as follows. Further, in the gear pump of the present invention, a flow path is provided for sending the liquid in the back chamber to the discharge side through a check valve.

[For use]

A back chamber is formed on the suction side within the casing, and a portion of the liquid sucked from the suction port is sent into this back chamber by an auxiliary gear to increase the back pressure of the driving gear and the driven gear. This reduces the pressure difference between the suction side and the discharge side, and even if the gap between the casing and the gear increases somewhat, backflow will not increase so much. Therefore, it is no longer necessary to set the gap extremely small, reducing friction loss and reducing the degree of increase in backflow due to progress of wear. In addition, if a flow path is provided to send the liquid in the back chamber to the discharge side through the check valve, the liquid sent to the back chamber by the auxiliary gear can be sent to the discharge side through this flow path, as if the four
It has a configuration in which liquid is transferred using two gears, and a large flow rate can be obtained.

【Example】

FIG. 1 is a longitudinal sectional view showing an embodiment of the invention. In the following embodiments, the same reference numerals are used for parts that are the same as or correspond to those in the conventional example. In the figure, a casing 1 housing a drive gear 4 driven by a motor (not shown) via a drive shaft 6 and a driven gear 5 supported by a support shaft 7 and rotated in mesh with the drive gear 4 is shown in the illustrated embodiment. In this case, the suction side is configured in a bulged shape, and the driving gear 4 and the driven gear 5 are connected to this part.
A pair of auxiliary gears 10 and 11 are housed therein, which mesh with each other, are supported by support shafts 8 and 9, and rotate in the opposite direction to the drive gear 4 and driven gear 5. Auxiliary gears 10 and 11
An arrow-shaped piston 12 is inserted between the auxiliary gears 10 and 11, and both the auxiliary gears 10 and 11 are connected to the inner surface of the casing 1 and the piston 12.
and are in contact with each other through a gap. Thereby, a back chamber 13 is formed between the four gears 4, 5, 10, and 11. As shown in the figure, two suction ports 2 are provided so as to open on the side wall surface of the casing 1. The piston 12 may be a part of the casing 1, but in the illustrated embodiment, in order to automatically adjust the gap between the piston 12 and the auxiliary gear 10. It is movably inserted. The piston 12 has an adjustment screw 1 screwed into the bottom of the cylinder 14.
5 and the auxiliary gear 6 is initially set via a spring 16. Further, the cylinder 14 and the discharge side are communicated through a pipe line 17. In such a configuration, when the drive gear 4 and the driven gear 7 rotate in the direction of the arrow, the liquid led from the suction port 2 is sent toward the discharge port 3 as shown by the broken line arrow. On the other hand, the auxiliary gears 10 and 11 are the drive gear 4 and the driven gear 5.
By rotating in the direction of the arrow opposite to , a part of the liquid from the suction port 2 is sent into the back chamber 13 as shown by the broken line arrow, and the back pressure of the driving gear 4 and the driven gear 5 is increased. This pressure increase acts to prevent the liquid from flowing back from the discharge side through the gap between the gear 4.5 and the casing 1 and the gap between their meshing surfaces, thereby reducing the flow rate. Further, this increase in back pressure acts to balance the force exerted on the drive shaft 6 and the support shaft 7 due to the pressure on the discharge side, thereby reducing the load on the bearing. Furthermore, in the configuration shown, the pressure on the discharge side is led into the cylinder 14 via the conduit 17 and pushes the piston 12 to the right in the figure. Therefore, when the load pressure increases, the piston 12 reduces the gap between it and the auxiliary gears 10 and 11 to keep the pressure in the back chamber 13 high, and when the load pressure decreases, the piston 12 has the opposite effect. That is, the pressure in the illustrated rear chamber is automatically adjusted according to the pressure on the discharge side (load side). FIG. 2 shows an embodiment in which another function is added to the embodiment of FIG. 1. That is, in FIG. 2, a flow path 18 for sending the liquid from the back chamber 13 to the discharge side is provided by piping, and although not shown, there is a flow path 18 from the discharge side to the back chamber 13.
A check valve is inserted to prevent the flow to. With this configuration, the piston 12 and the auxiliary gear 10.
By setting the gap between the rear chamber 13 and the rear chamber 11 small and keeping the pressure in the rear chamber 13 higher than that on the discharge side, the liquid sent into the rear chamber 13 by the auxiliary gear 10.11 can be guided to the discharge side through the flow path 18. can. As a result, the flow rate of the gear pump is adjusted to the driving gear 4, driven gear 5, auxiliary gears 10 and 1.
The total amount of liquid sent by the four gears of 1 is,
This is effective when a large flow rate is required in the low pressure region of the load. Furthermore, by adding a pressure regulator 19 that drives the adjusting screw 15, the flow rate can be arbitrarily adjusted by an external command.

【Effect of the invention】

According to this invention, by increasing the pressure on the back side of the driving gear and the driven gear using the auxiliary gear, it is possible to suppress the backflow through the gap between the driving gear and the driven gear and the inner surface of the casing, and to reduce the gap to an extreme level. Since it does not have to be made small, friction loss due to liquid viscosity can be reduced, and
Even if the gap increases due to progress of wear, etc., changes in flow rate due to increase in backflow or fluctuations in load can be minimized. Further, by providing a flow path for sending the liquid on the back side to the discharge side via the check valve, it is possible to construct a gear pump with a large flow rate.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of an embodiment of the present invention, FIG. 2 is a longitudinal sectional view of another embodiment, and FIG. 3 is a longitudinal sectional view of a conventional example. DESCRIPTION OF SYMBOLS 1... Casing, 2... Suction port, 3... Discharge port, 4... Drive gear, 5... Driven gear, 10.11.
...Auxiliary gear, 13...Back chamber, 18...Flow path. 1.

Claims (1)

[Claims] 1) A gear pump in which a pair of driving gears and a driven gear that mesh with each other are housed in a casing having a liquid suction port and a liquid discharge port, the driving gear and the driven gear being disposed on the suction side of the casing. A pair of auxiliary gears that mesh with each other to rotate are provided to form a back chamber between these four gears, and a portion of the liquid sucked from the suction port is sent to the back chamber by the auxiliary gears. A gear pump featuring: 2) The gear pump according to claim 1, further comprising a flow path for sending the liquid in the back chamber to the discharge side through a check valve.