JPH04187883A - Trochoid gear pump - Google Patents

Abstract

PURPOSE:To permit noiseless and non-vibrating motion by equipping the tooth space surface of an outer rotor with a sliding area against a cylindrical inner rotor provided in parallel to the rotor shaft axis and with an inclined surface expanding to the outside provided extendedly from the sliding area toward one of the end face. CONSTITUTION:A tooth space surface 6 of an outer rotor 2 is composed of a sliding area 6a against an inner rotor 1 and an inclined surface 6b. The sliding area 6a is of a cylindrical surface having a curvature conforming almost to the manoeuvering envelope near the minimum point 8 (the point where a space chamber 5 becomes the minimum capacity) of an addendum of the inner rotor 1, and is formed with a certain width from one end face 2a of the outer rotor 2. Therefore the addendum 4 of the inner rotor 1 results in opposing to the sliding area 6a through a small clearance at the minimum point 8. Because the inclined surface 6b is provided so as to expand to the outside from the sliding area 6a to the other end face 2b, a certain size of end face opening portion 9 is left in the space chamber 5 even when the inner rotor addendum 4 is at the minimum point 8 causing to reduce the velocity of fluid going in and out thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a trochoid gear pump or motor, and more particularly to a gear tooth profile for a trochoid gear pump or motor that can achieve high efficiency and low noise operation.

[Conventional technology]

As for the tooth profile of a trochoid gear pump or motor, the tooth profile of the outer rotor (internal gear) is formed based on a plurality of circular arc cross-sectional tooth profiles, and the tooth profile of the inner rotor (external gear) is a trochoid curve created using the circular arc cross-sectional tooth profile of the outer rotor as a standard. Generally, it is formed based on Further, the mutually adjacent arc cross-sectional tooth profiles of the outer rotor are connected by a smooth curve to form a tooth groove portion. The shape of the tooth surfaces of the inner rotor and the outer rotor is a three-dimensional shape in which the respective tooth profile curves are translated in parallel in the direction of the rotation axis to give thickness. That is, the inner circumferential surface of the outer rotor and the outer circumferential surface of the inner rotor are both constituted by cylindrical curved surfaces extending parallel to the rotation axis (perpendicular to each rotor end surface).

FIG. 6 shows an example of a trochoid gear pump using a conventional tooth profile.

In the figure, 1 is an inner rotor, 2 is an outer rotor, and a plurality of internal teeth 3 having an arcuate cross section are formed on the inner peripheral surface of the outer rotor. Further, the inner rotor 1 is formed with external teeth 4 having a trochoidal tooth profile created by the arcuate teeth 3 of the outer rotor 2 as both the inner and outer rotors rotate. Therefore, the tooth surface 4 of the inner rotor 2
rotates while always maintaining contact with the tooth surface 3 of the outer rotor 2, and an interdental space 5 defined by these contact points a and a' is formed between both rotors. The volume of these interdental chambers 5 increases and decreases as the rotor rotates in the direction indicated by the arrow in the figure.
Fluid is sucked in and discharged. During suction and discharge, fluid flows into and out of the interdental space 5 from the end face of the rotor in a direction along the rotation axis.

[Problem to be solved by the invention]

In the conventional example shown in FIG. 6, the arcuate teeth 3 of the outer rotor 2 are connected by a tooth groove surface 6 that is continuous with the cylindrical surface of the tooth 3 and extends parallel to the rotation axis. Since the tooth groove surface 6 does not participate in the meshing between the tooth surface 3 and the tooth surface 4 that define the interdental space 5 (FIG. 6 a', a'), it can have a relatively free shape.
In the conventional example shown in the figure, the inner rotor 1 is in a state where the teeth 4 are most deeply inserted into the tooth grooves 6 (the state where the volume of the interdental space 5 is the minimum).
A relatively large clearance (see FIG. 6, FIG. 7) is maintained between the tips of the teeth 4 and the tooth groove surface 6 of the outer rotor 2. This is achieved by keeping the opening area of the outer rotor end face of the interdental space 5 large to a certain extent even at the point where the interdental space 5 reaches its minimum volume (hereinafter referred to as the "minimum point"), thereby preventing the suction and discharge of fluid into the interdental space 5. This is to ensure smooth operation.

However, when a relatively large clearance is provided between the inner rotor tooth tip and the outer rotor tooth groove at the minimum point as described above, the outer rotor 2 rotates with a certain degree of freedom in the radial direction relative to the inner rotor 1. become,
There is a problem in that the rotor rattles, resulting in an increase in vibration and noise, and an accompanying decrease in the durability of the rotor.

In order to solve the problem caused by the rattling of the rotor, as shown in FIG. Techniques are being taken to reduce the clearance. In this case, the tooth groove surface 6 of the outer rotor 2 has a shape similar to the shape of the tip of the tooth 4 of the inner rotor 1, so an extremely small clearance can be maintained even at the minimum point, and radial play of the outer rotor 2 can be prevented. Can be suppressed. However, on the other hand, when the tooth profile is formed in this manner, the end surface opening area of the interdental chamber 5 becomes extremely small at the minimum point, and the velocity of fluid flowing in and out of the interdental chamber 5 becomes extremely large before and after the minimum point. As a result, strong squish and cavitation tend to occur near the minimum point, which may cause problems such as rotor erosion and noise.

As described above, in the case of trochoid gear pumps and motors, countermeasures for preventing vibration of the rotor and preventing occurrence of cavitation, etc., are required, and it has been difficult to solve both problems at the same time.

In view of the above problems, the present invention aims to provide a trochoid gear pump or motor that can simultaneously solve the problems of cavitation occurrence and rotor vibration.

[Means to solve the problem]

According to the present invention, in a trochoid gear pump or motor comprising an outer rotor having arcuate teeth on its inner circumferential surface and an inner rotor having teeth having a trochoidal tooth profile created by the tooth profile of the arcuate teeth, the inner circumferential surfaces of the outer rotor are mutually The tooth groove surface smoothly connects the arcuate teeth adjacent to each other, and the tooth groove surface has a sliding part with the inner rotor, which is a cylindrical surface extending parallel to the rotor rotation axis. A trochoid gear pump or motor is provided, comprising: a radially outwardly expanding inclined surface extending from the sliding portion toward at least one end surface of the outer rotor.

[For production]

As mentioned above, the sliding part formed on a part of the tooth groove surface of the outer rotor performs relative sliding motion while maintaining a small clearance with the tooth tips of the inner rotor near the minimum point during rotation, so that it slides in the radial direction of the outer rotor. movement of the rotor is suppressed, and vibrations caused by rattling of the rotor are reduced.

In addition, the wall surface of the tooth groove surface that continues from the sliding part to the outer rotor end face is formed to expand outward as it approaches the end face, so the end face opening area of the interdental space is relatively large even near the minimum point. is maintained, and the flow rate of fluid into and out of the interdental space does not increase rapidly near the minimum point.

〔Example〕

FIG. 1 shows an embodiment of the present invention.

The figure shows a trochoid gear pump, and the same reference numerals as in FIGS. 6 and 7 indicate the same components.

In this embodiment, the shape of the tooth surface 4 of the inner rotor 1 and the shape of the tooth surface 3 of the outer rotor 2 are the same as those of the conventional example shown in FIGS. 6 and 7.

However, in this embodiment, the shape of the tooth groove surface 6 of the outer rotor 2 is not a simple cylindrical surface as in the conventional examples shown in FIGS. 6 and 7, but has a shape as shown in FIG. 2. FIG. 2 is a partially enlarged perspective view showing the tooth groove section cut along a plane including the rotation axis.

The tooth groove surface 6 of this embodiment is composed of a sliding portion 6a with respect to the inner rotor and an inclined surface 6b. The sliding portion 6a is a cylindrical surface having a curved shape that substantially matches the motion envelope near the minimum point of the tooth tip of the inner rotor 1, and is formed to have a constant width from one end surface 2a of the outer rotor 2. Further, the inclined surface 6b is provided to be inclined so as to expand outward from the sliding surface 6a to the other end surface 2b of the outer rotor 2, and both the sliding surface 6a and the inclined surface 6b are provided on both sides in the circumferential direction. It is formed to smoothly connect to the cylindrical surface forming the arc teeth 3 of the outer rotor.

As mentioned above, since the sliding surface 6a approximately corresponds to the motion capsule line near the minimum point of the tooth tip of the inner rotor 1, the tooth tip 4 of the inner rotor 1 is small at the minimum point 8 as shown in FIG. The sliding surface 6a faces the sliding surface 6a through the rear clearance. Therefore, the movement of the outer rotor 2 in the radial direction is restricted and play is suppressed to a minimum, allowing smooth rotation without vibration.

Furthermore, even when the inner rotor tooth tip 4 is at the minimum point, the inclined surface 6b expands outward, so the interdental space 5 remains with an end face opening of a certain size (indicated by the shaded area 9 in Fig. 1). The flow rate of fluid in and out is reduced.

FIGS. 4(A) and 4(B) schematically show fluid velocity changes just before the minimum point of the conventional tooth profile and the tooth profile of the present invention.

FIG. 4(A) shows the change in flow velocity in the rotor thickness direction in the interdental space 5 in the case of the conventional tooth profile shown in FIG.

In the conventional example, the tooth groove surface of the outer rotor 2 is similar to that of the inner rotor 1.
The cross-sectional area of the interdental chamber 5 is constant in the rotor thickness direction. In this state, when the inner rotor 1 approaches the outer rotor 2 as shown in FIG. do. Therefore, the flow velocity within the interdental chamber increases as it approaches the opening end of the interdental chamber.

FIG. 5(A) shows the ratio of the rate of change dV/dt of the volume V of the interdental chamber 5 near the minimum point to the area of the opening end of the interdental chamber in the tooth profile of the conventional example shown in FIG. 7, that is, in the axial direction at the opening end. These are the results of calculations for the tooth profile that constitutes the average flow velocity U, and the vertical axis of the figure is the flow velocity made dimensionless by rotation speed, rotor size, etc.
The horizontal axis represents the rotation angle starting from the minimum point position of a specific tooth of the inner rotor. The figure shows that the number of teeth on the inner rotor is 6.
The figure shows a combination in which the outer rotor has seven teeth.

As can be seen from Fig. 5 (A), immediately after the minimum point, the interdental space 5
The velocity of fluid flowing into the interdental space 5 becomes extremely large, and conversely, the velocity of fluid flowing out from the interdental space 5 becomes extremely large just before the minimum point.

When converted into a trochoid gear pump, etc. actually used in automobile hydraulic equipment, this flow velocity exceeds several hundred meters and seven seconds, causing cavitation during suction and strong squish during discharge, resulting in discharge pulsation, noise, and even cavitation erosion. may occur.

On the other hand, FIG. 4(B) shows the change in flow velocity in the rotor thickness direction in the interdental space 5 of the tooth profile (FIGS. 1 and 2) according to the present invention. In this embodiment, the tooth groove surface 6 of the outer rotor 2
is composed of a sliding part 6a formed parallel to the tip of the tooth surface 4 of the inner rotor 1 and an inclined surface 6b that expands outward, so the speed increase at the inclined surface 6b is gradual and the gap between the teeth is The flow velocity at the end of the room does not increase to that extent.

The maximum value of the flow velocity at the opening end of the interdental chamber is the inner rotor 1
It is determined by the area of the opening end of the interdental chamber (shaded area 9 in FIG. 2, hereinafter referred to as "minimum opening end area") when it reaches the minimum point position. It has been found that sufficient effects can be obtained even if this minimum opening end area is extremely small. For example, in FIG. 5(B), the minimum opening end area is 1% of the interdental space mouth end area (maximum opening end area) at the point where the interdental space 5 has the maximum volume.
It shows the average axial flow velocity U at the open end calculated under the same conditions as in Figure (A).

As can be seen from the figure, the flow velocity around the minimum point is significantly reduced by leaving only 1% of the maximum opening end area. Therefore, by setting the tooth profile shape as described above, it is possible to prevent squish and cavitation from occurring near the minimum point.

As can be seen from FIG. 4(B), the smaller the width (axial length) of the sliding portion 6a of the tooth groove surface 6, the greater the flow velocity reduction effect.On the other hand, when considering the rotor vibration suppression effect, It is necessary to make it as large as possible.

Therefore, the width of the sliding part 6a is 1710 to 1/ of the rotor thickness.
It is preferable to set it to about 2.

In the above embodiment, the sliding portion 6a is provided on one end surface side of the outer rotor 2, but as shown in FIG. A similar effect can also be obtained by a structure in which two inclined surfaces 6b and 6b' are provided on both sides of the rotor 6a, respectively, each expanding toward the end surface of the outer rotor 2.

Further, in the above embodiment, the shape of the sliding portion 6a is set to have a cross-sectional shape that substantially matches the motion envelope of the tip of the tooth surface 4 of the inner rotor 1. Any shape that can maintain a sufficiently small clearance with the tip of tooth No. 1 is sufficient; for example, a combination of cylindrical surfaces may be used.

〔Effect of the invention〕

As described above, the present invention provides a sliding portion on the tooth groove surface of the outer rotor of a trochoid gear pump or motor to suppress rotor play, and an inclined surface to ensure the minimum end face opening area of the interdental space, thereby reducing vibration. It has the effect of preventing both cavitation and enabling smooth movement of hydraulic equipment without noise or pulsation.

Furthermore, since the inclined surface provided on the tooth groove surface of the outer rotor is shaped to smoothly connect to the arc teeth of the outer rotor, there is no disadvantage in terms of strength such as a notch effect.
There is no sudden change in shape, and there is no disadvantage compared to conventional products in terms of cost and quality when manufacturing methods such as sintered metal are used.

[Brief explanation of drawings]

FIG. 1 is a plan view of an embodiment of the present invention, FIG. 2 is a partially enlarged perspective view of the same embodiment, and FIG. 3 is a second embodiment of another embodiment of the present invention.
Figures similar to Figure 4 (A) (B), Figure 5 (A) (B)
) are the fluid discharge of the conventional example and the embodiment of the present invention, respectively;
The drawings showing the suction speed, FIGS. 6 and 7 are plan views showing conventional tooth profiles. 1... Inner rotor, 2... Outer rotor,
3... Arc tooth, 4... Trochoid tooth surface, 5... Interdental space, 6... Tooth groove surface, 6a.
...Sliding part, 6b...Slanted surface.

Claims (1)

[Claims] 1. A trochoid gear pump or motor comprising an outer rotor having arcuate teeth on its inner circumferential surface, and an inner rotor having teeth having a trochoidal tooth profile created by the tooth profile of the arcuate teeth, wherein the inner circumferential surface of the outer rotor has the arcuate teeth adjacent to each other. A part of the tooth groove surface includes a sliding part with the inner rotor consisting of a cylindrical surface extending parallel to the rotor rotation axis, and a sliding part with the inner rotor. A trochoid gear pump or motor, comprising: an inclined surface extending radially outward from the outer rotor toward at least one end surface of the outer rotor.