JPS5990788A - Rotary pump - Google Patents

Abstract

PURPOSE:To prevent occurrence of cavitation, by employing such an arrangement that a line for making a cut-off portion in the direction of rotation of a suction port is aligned with the extension of a ine passing the center of rotation of an outer rotor in a rotary pump in which a trochoid gear is used for an inner rotor. CONSTITUTION:In a housing 1, a rotary pump has an inner rotor 8 consisting of a trochoid gear to which a driving shaft is connected and an outer rotor 9 which is turned by the inner rotor 8. Further, a suction port 2 and a discharge port 3 are formed in the inner end face of the housing 1. Here, the suction port 2 is so formed that the portion of the line connecting a small arcuate surface 4 and a large arcuate surface 5 at the rear end portion (in the direction of rotation of the rotors 8, 9) of the suction port 2, i.e., a line 11 for forming a cut- off portion in the direction of rotation is aligned with an extension line X passing the center of rotation of the outer rotor 9 or a position near the same. With such an arrangement, the area S'1 of the fluid inlet portion just before a space 10 is closed can be made greater as compared with the conventional arrangements, so that it is enabled to make fluid flow into the space 10 smooth and thus to prevent occurrence of cavitation.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application This invention relates to a fundamental improvement of a rotary pump, particularly a rotary pump that employs a trochoidal gear in its inner rotor.

(b) Prior art and its problems As shown in FIG. 1, in a conventional pump using trochoidal gears, the suction port 2 and the discharge port 3, which are formed on the end face of the housing 1, both have a radius r. It is designed such that a small circular arc surface 4 and a large circular arc surface 5 having a radius R centered on the eccentric point are connected by straight lines 6 and 7 at both ends.

However, although such a shaped port poses no problem on the discharge side, it causes a major problem on the suction side. Namely, No. 1? As shown in the figure, when the space lO created by the inner rotor 8 and the outer rogue 9 approaches the closing state shown in Fig. 3, the area S between the rotor rotor and the rotor 7 in an end view
2 gradually increases, but conversely, the artificial area S1 into which the fluid flows becomes very narrow, and for this reason, when the rotor is rotated at high speed, a keet vibration phenomenon occurs, causing abnormal wear and noise.

Therefore, conventional measures to prevent the gear biting phenomenon include lowering the rotation speed of the rotor and increasing the number of teeth on the rotor to reduce the space area S in the closed state shown in Fig. 3. This means that it is impossible to measure the increase in the discharge amount per fixed time using pumps of the same size, and even if such a method is adopted, the same problem as described in "-4" still remains.

(c) Means for solving the problems This invention aims to solve the above-mentioned drawbacks by:
At least the straight line forming the cut-off part of the suction side boat is formed so that it is located at the extension of the straight line connecting to the center of rotation of the outer rotor or its vicinity, and the fluid inlet area immediately before the cut-off part between the insignia is It is expanded.

B) Embodiment The present invention will be described in detail below based on the embodiment shown in the attached FIG. 4 and the operational view of FIG. 5.

The rotary pump of the embodiment shown in Fig. 4, like the conventional pump using trochoid gears, has an inner rotor 8 connected to a drive shaft (not shown) inside the housing 1, and is driven by the rotation of the inner rotor 8. An improved suction boat 2 and a conventionally shaped discharge boat 3 are formed on the inner end surface of the housing 1.

The suction boat 2 has a small arc surface 1 at the end of the rotor in the rotational direction.
The straight line 11 that connects the large arc surface 5 and the large arc surface 5, that is, the straight line 11 that forms the cutoff section in the rotation direction, is formed on the extension line X of the straight line that passes through the rotation center O of the outer rotor and its vicinity. Due to this shape, the space created between the inner and the inner rotor 8 is closed off by the end face of the inner rotor 8 just before the space 10 reaches its maximum volume (the state shown in Figure 4). In the area defined by the trochoidal curved surface 8' of the inner rotor forming the closed chamber and the inscribed circle a of each trochoidal curved surface, a straight line, an arc, or
-Added to shapes using locoid curves, etc.

As shown in FIG. 5, in the rotary pump in which the suction boat 2 is provided with the specific straight line 11 as described above, the fluid population area 51' immediately before the space IO is closed is larger than that of the conventional human [1 area S1]. Therefore, the fluid can flow into the space 10 without any hindrance, and the cavitation phenomenon is prevented.

In addition, FIG. 6 shows another embodiment, and the straight line that creates the closed section of either the suction side boat 2 or the discharge side boat 3 is a straight line that passes through the rotation center 0 of the outer rogue or its vicinity. It is formed so that it is located on the extension line X of .

The fiIiJ arrow indicates the rotation direction, and is close to the distance between the contact points of the outer rotor and the inner rotor when the gap area created between the Aracle rotor and the inner rotor is maximized due to the above configuration, that is, the closed cut distance. but,
When the diameter of the boat is increased to be larger than the small diameter r of the boat, the desired effect of the present invention is most clearly exhibited.

(e) Effects As explained in 2, according to the present invention, the straight line 11 that forms the closing part of the suction boat is specified to increase the fluid population area before the closing of the space between the inner rotor and the outer rotor. Therefore, the cavitation phenomenon is effectively prevented, which makes it possible to increase the rotation speed of the rotor or reduce its number of teeth to increase the volume of the shut-off space. The performance of gear-based rotary pumps can be dramatically improved.

[Brief explanation of drawings]

Fig. 1 is an end view showing the suction and discharge boat shapes of a conventional pump using trochoid gears, and Figs. 2 and 3 are sectional views showing the operation of the pump adopting the boat shape of Fig. 1. , FIG. 4 is a sectional view of a rotary pump showing an example of the present invention when the inner rotor is rotated to the position shown by the chain line in FIG.
FIG. 5 is a sectional view showing the effect thereof, and FIG. 6 is an explanatory view of another embodiment. l...Housing, 2...Suction boat, 8...Discharge port 1-14...Small arc surface, 5...Large arc surface, 6, 7...Straight line, 8... Inner rotor, 8'・
... Trochoid surface, 9... Outer rogue, 10.
...Space, 11... Straight line that creates the cutoff part 11 Figure 6 Yoshi 2 Figure Yoshi 3 Figure 4

Claims (1)

[Claims] (],) In a rotary pump that uses a trochoid gear for the inner rotor, the straight line that creates the closed section in the rotational direction of the suction side port is a straight line that passes through the rotation center of the outer rotor or its vicinity. A rotary pump characterized by being formed as an extension of. (2) The rotary pump according to claim (1), wherein the distance between the closing portions is larger than the small diameter of the port.