JPH0533738Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement of a gear pump in which a pair of gears mesh and rotate externally in an internal chamber of a casing.

In this type of external gear pump, both sides of the gear are generally suppressed by casing walls or fixed side plates, and as the gear rotates, liquid is trapped in the gap between the tooth valley and the inner wall of the casing. is pumped out to the discharge side of the pump. However, for this type of gear pump, a spur gear with an involute tooth profile is usually used from a manufacturing standpoint, and since the meshing ratio of the gears is greater than 1, there is always a period in which the two sets of teeth are meshing. Therefore, part of the liquid on the discharge side is trapped in the gap between both teeth and returned to the suction side. This confined liquid compresses and expands due to changes in the confined volume as the gear rotates, resulting in large pressure changes. In other words, the pressure of the liquid trapped at the beginning of tooth-to-tooth meshing increases, causing an increase in shaft load, bearing load, shaft power, and decrease in discharge amount, and at the final stage of meshing, the pressure decreases.
It also causes cavitation. In addition, the pressure of the liquid sandwiched between the teeth increases almost linearly from the suction side to the discharge side, so the lateral thrust acting on the circumferential surface of the gear causes the gear shaft to move toward the discharge side. This force is pushed toward the suction side, increasing the axial load or bearing load, and this force becomes larger as the discharge force becomes higher.

In order to avoid the occurrence of harmful factors or inconveniences as mentioned above, conventionally relief grooves were provided on the casing wall or side plate of the gear side facing the discharge side and suction side.
Countermeasures have been taken by providing movable side plates combined with elastic members, and by making load-bearing parts such as shafts and bearings larger and more rigid. However,
All of these countermeasures not only require a lot of workmanship, have complex structures, increase costs, and increase in size, but also have the drawbacks of reducing shaft power and improving pump performance itself. However, we were not necessarily satisfied with this point.

The present invention aims to eliminate the above-mentioned drawbacks and inconveniences, and to provide a pressure-balanced external gear pump that is simple in structure, highly efficient, and versatile at a low cost.

The pressure-balanced gear pump according to the present invention is a gear pump in which a pair of gears mesh and rotate externally in an internal chamber of a casing, and includes both side surfaces of the pair of gears and an end wall surface of the internal chamber facing each side. Each chamber between the two sliding valve plates is made of synthetic resin with good sliding properties mixed with an appropriate amount of carbon fiber, and is formed into a shape and size that matches the cross-sectional shape and dimensions of that chamber. ~4 pieces each
The gear is loaded with a slight gap left, and both the drive shaft and driven shaft of the gear are inserted into the through holes of these sliding valve plates, and each chamber section is opened by the action of the hydraulic pressure in the internal chamber. It is characterized in that the sliding valve plate is configured to be able to automatically slide forward and backward relative to the side surface of the gear.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings showing an example of its implementation.

In FIGS. 1 and 2, 1 is a casing of an external spur gear pump, in which an end wall 1A and a peripheral wall 1B are integrally formed, and a bearing body 2 is connected to the open side 1C with bolts. A gear 5 on the drive shaft 4 side and a gear 7 on the driven shaft 6 side are disposed in an internal chamber 3 of the casing, which has a roughly figure-8 cross section, in a state of external contact and meshing. 2 and is supported by a bearing 8 in a sealed state. The drive shaft 4 is rotationally driven by an electric motor (not shown) connected to the shaft end projecting outward from the bearing body 2, and the gears 5 and 7 are rotationally driven by the drive shaft 4. Then, the liquid introduced into the internal chamber 3 from the suction port 9 of the casing 1 is confined in the wall surface of the internal chamber 3, that is, the space formed by the inner wall surface of the peripheral wall 1B and the valleys of the teeth, and is not compressed. It is pressed and sent out from the discharge port 10.

In the illustrated example, the pair of gears 5,
7 and the end wall surfaces 11A and 11B of the internal chamber 3 facing each other.
A and 3B are each loaded with four sliding valve plates 12 with a shape and dimensions that match the cross-sectional shape and dimensions of these chambers, leaving a slight gap, and these sliding valve plates is the through hole 12', 1
2', and by inserting both shafts of the drive shaft 4 of the gear 5 and the driven shaft 6 of the gear 7 into these through holes, they are respectively supported so as to be able to slide slightly in the axial direction. ing.

As will be described later, the sliding valve plate 12 is operated by constantly receiving the hydraulic pressure in the internal chamber 3, especially the discharge pressure on the discharge side, so it is subject to the fluid load and the accompanying mechanical pressure. It must have sufficient mechanical strength to withstand the physical load, as well as good responsiveness to operate effectively against pressure changes, and
In order to be able to handle liquids with various chemical properties, they are required to have high chemical resistance. Taking these demands into consideration, we conducted various experiments and found that a synthetic resin that is lightweight, strong, wear-resistant, and chemical resistant, and also has sliding properties, compression properties, and heat resistance. , especially fluororesins, such as tetrafluoroethylene (C ₂
It has been found that very good results can be obtained by producing a copolymer of F ₄ ) and ethylene (C ₂ H ₄ ) mixed with an appropriate amount (for example, 15 to 25%) of carbon fiber.

In the figure, 13 is a fluororesin seal ring member made of a combination of a ring having an X-shaped cross section and an O-ring fitted into its outer peripheral groove, and 14 is a fluororesin packing plate.

In the present invention configured as described above, the gears 5 and 7 are rotationally driven by the drive shaft 4, and the liquid is sucked into the internal chamber 3 from the suction port 9 and sent out from the suction side to the discharge side. Then, the pressurized liquid flows into the chamber portions 3A, 3B through the slight gap between the side surfaces of the gears 5, 7 and the sliding valve plate 12 adjacent thereto, and also flows into the chamber portions 3A, 3B. Between each sliding valve plate 1 and the adjacent sliding valve plate 12,
2, between each sliding valve plate 12 and each shaft 4, 6, between the end wall surfaces 11A, 11B and the sliding valve plate 12 adjacent thereto.
and between each sliding valve plate and the inner wall piece of the peripheral wall 1B, and forms a liquid film there.
The gear-side sliding valve plate 12 receives pressure from the sliding valve plate 12 behind it and the liquid film, and is pressed against the side surfaces of both gears 5 and 7 via the liquid film.

Next, the liquid sandwiched between the teeth is compressed, and as the pressure increases, a part of the pressurized liquid moves against the sliding valve plate 12 on the side of the gear and the liquid film. Since the air is forced to flow into the chamber portions 3A and 3B that communicate with the suction side and the discharge side, large pressure changes are prevented from occurring, and therefore, increases in shaft load, bearing load, shaft power, etc. This can prevent the occurrence of cavitation. Furthermore, when the discharge pressure increases due to the continuous rotation of the gears, the pressure liquid on the discharge side is transferred to the discharge side portions of the slide valve plates 12 on both sides of the gears 5 and 7, that is, the second In the figure, it first acts on the right half part, and pushes this part in the direction away from the side surface of the gear against the liquid film, that is, in the direction of the end wall surfaces 11A and 11B, pushing it open and into the chamber parts 3A and 3B. Forced inflow, then acts on the suction side part, slidingly displaces the entire part in the direction away from the gear side surface, and flows from this chamber part to the suction side of the internal chamber 3 communicating with this, so that the suction side A relatively rapid drop in pressure is prevented by the action of this discharge pressure, and harmful pressure differences between the discharge side and the suction side are prevented. Therefore, as a result, the lateral thrust acting around the gear from the discharge side to the suction side is greatly reduced, so even if the discharge pressure increases, the shaft load, bearing load, etc. will increase proportionally. Things like that will no longer be the case.

In the illustrated example, the sliding valve plate 12 has chamber portions 3A, 3
There are four discs each in B, but depending on the size of the gear pump, the thickness of the sliding valve plate, and other conditions, even if the number is two or three each, the same effect as described above can be achieved. It is something that can be played. However, it has been found through experiments that the operation becomes unstable when there are five or more of each type. However, when the sliding valve plate 12 is made of reinforced synthetic resin such as fluororesin mixed with an appropriate amount of carbon fiber, it is difficult to slide due to the properties of the material described above, especially its excellent sliding properties. Since the valve operating plate 12 can function as a pressure regulating valve that can operate easily and effectively against pressure changes and has good responsiveness, the above-mentioned effects are further enhanced. 7
moves in the axial direction under the axial thrust and a group of sliding valve plates 12 is pressed against the end wall surface 11A or 11B.
acts to push back against the axial thrust. In this case, in addition to the sliding valve plate 12 having good sliding properties, the liquid film present on the contact surface between the side surface of the gear and the adjacent sliding valve plate acts as a lubricating liquid. , and the pressure acts to push back the adjacent sliding valve plate, so the contact friction between them is extremely small. Therefore, the amount of heat generated by contact between the two is extremely small, and the high speed rotation of the gears 5 and 7 is not hindered.

In addition, the total clearance that should be left between one side of the gears 5 and 6, the end wall surface 11A or 11B of the chamber portion 3A or 3B opposite thereto, and the plurality of sliding valve plates 12 loaded between these two surfaces. The numerical value varies depending on the size of the pump, the volume of the chamber parts 3A and 3B, the thickness or number of sliding valve plates 12, etc., but according to experiments, the distance between the side surface of the gear and the end wall surface is In the case of 8 mm, the total clearance (this approximately corresponds to the size of the gap between the side surface of the gear and its adjacent sliding valve plate when a group of sliding valve plates is biased toward the end wall) is 0.1 to 0.5 mm. It has been found that the degree is appropriate in terms of reducing leakage from the side of the gear.

In this way, the present invention not only solves the drawbacks and inconveniences mentioned at the beginning, but also provides a highly efficient and versatile pressure-balanced external cylinder that can be operated while maintaining a high discharge pressure. This makes it possible to provide a type gear pump at a low cost, and it is particularly suitable for implementation in a small external type gear pump.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional side view of a gear pump that is an embodiment of the present invention, FIG. 2 is a sectional view taken along line A--A in FIG. 1, and FIG. 3 is an end view of a sliding valve plate. In the drawings, 1 is the casing, 3 is the internal chamber,
3A and 3B are chamber parts, 4 is a drive shaft, 5 is a drive gear, 6 is a driven shaft, 7 is a driven gear, 11A and 11
B is an end wall surface of the internal chamber, and 12 is a sliding valve plate.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) In a gear pump of the type in which a pair of gears mesh and rotate externally in an internal chamber of a casing, both sides of the pair of gears and the ends of the internal chamber opposite to these sides, respectively. In each room between the walls,
Two to four sliding valve plates each are made of synthetic resin with good sliding properties mixed with an appropriate amount of carbon fiber and have a shape and dimensions that match the cross-sectional shape and dimensions of the chamber. At the same time, the driving shaft and the driven shaft of the gear are respectively inserted into the through holes of these sliding valve plates, and each chamber part is slid by the action of the hydraulic pressure in the internal chamber. A pressure balanced gear pump characterized in that the valve plate is configured so that it can automatically slide forward and backward relative to the side surface of the gear. (2) The pressure balanced gear pump according to claim 1, wherein the synthetic resin is a fluororesin.