JPH051397B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a gear pump that rotates by meshing with each other an internal gear and an external gear that have tooth surfaces formed by a trochoidal curve.

<Prior art> First, a conventional gear pump will be explained with reference to FIG. 1. This gear pump has a driven gear 1,
The driven gear 1 has inward meshing teeth 3, and the driven gear 2 has a drive gear 2.
Outer meshing teeth 4, the number of which is one less than the inward meshing teeth 3, are formed on the outer surface. The inward meshing teeth 3 have tooth surfaces 3a and 3b formed by a trochoidal curve formed by a well-known method as disclosed in JP-A No. 57-79290, and the outward meshing teeth 4 have contours that mesh with these tooth surfaces 3a and 3b. It has tooth surfaces 4a and 4b.

The outward meshing teeth 4 correspond to the bottoms of the internal meshing teeth 3 of the driven gear 1 on the left side of FIG. The configuration is such that they are mutually sealed.

Therefore, by rotating the drive gear 2 together with the rotating shaft 9, the volumes of the pump chambers 5 and 6 are increased and decreased, and fluid is sucked and discharged through the suction and discharge ports 8 corresponding to the pump chambers 5 and 6. .

However, in such a conventional gear pump, the top portion 3c of the inward meshing tooth 3 is constituted by a trochoid curve similar to that of the gear pump disclosed in JP-A-57-79290, or a curve similar thereto, and the top portion 3c of the outward meshing tooth 4 4c is the top portion 3 of the inward meshing tooth 3;
It was formed by the curve created at c or a curve similar to it.

In the conventional gear pump in which the entire top portion 4c of the outward meshing tooth 4 is formed in an arc shape, when the outward meshing tooth 4 rotates to the A position or the B position, the top portion 3c of the internal meshing tooth 3 and the outer meshing tooth 4 approaches the top 4c. Therefore, if there is play in the fitting portion between the rotating shaft 9 and the drive gear 2, or if there is a manufacturing error in the tooth profile shape of the inward meshing teeth 3 or the outward meshing teeth 4, the top portion 3c of the inward meshing teeth 3, There was a problem in that contact noise was generated due to interference between the tops 4c of the outward meshing teeth 4.

<Structure of the Invention> The present invention has been made to solve such conventional problems, and includes a sealing point that contacts and seals the top of the inwardly meshing tooth on the outwardly meshing tooth of the drive gear, and a tooth of the outwardly meshing tooth. A circular arc portion having a smaller radius than the generating curve connecting the meshing starting points of the surfaces or its approximate circular arc is formed at the center of the top thereof, and between this circular arc portion and the meshing starting point of the tooth surface, the end of the circular arc portion and the meshing starting point are formed. The structural feature is that a straight line portion is formed that connects the two sections straightly.

<Operation> Since the present invention has the above configuration, when the driven gear and the drive gear are driven to rotate, a large clearance is created between the tops of the inwardly meshing teeth and the tops of the outwardly meshing teeth in areas other than those where sealing is required. can be secured. This makes it possible to prevent the top from coming into contact with each other and the resulting noise.

<Examples> Examples of the present invention will be explained below based on the drawings. Figure 2 shows an embodiment in which the gear pump of the present invention is applied to an automobile oil pump.
0 is the cylinder block of an automobile engine, 11
12 is a rotating shaft (crankshaft), and 12 is a pump housing fixed to the cylinder block 10. A lid 3 is fixed to the pump housing 12, and a driven gear 14 and a drive gear 15 are rotatably housed in a space formed between the pump housing 12 and the inward meshing teeth 3.

As shown in FIG. 3, the driven gear 14 has inward meshing teeth 16 formed at equal intervals in the circumferential direction, and the drive gear 15 has outer meshing teeth 17, which are one less in number than the inward meshing teeth 16. has been done.
This inward meshing tooth 16 is similar to the conventional one.
The outward meshing tooth 17 has a tooth surface 17a having a contour that meshes with the tooth surface 16a, 16b of the inward meshing tooth 16. ,1
7b, and these tooth surfaces 17a and 17b transmit the rotation of the drive gear 15 to the driven gear 14 while sequentially moving the meshing point within the meshing range L from the tooth bottom to the meshing start points P1 and P3. There is.

And the outward meshing teeth 17 of this drive gear 15
corresponds to the bottom of the inward meshing teeth 16 of the driven gear 14 on the left side of FIG. It's summery.

In a gear pump having such a configuration, the present invention is characterized by the shape of the top portion 30 of the outward meshing teeth 17. That is, the top portion 20 of the inward meshing teeth 16 is formed in a trochoidal curve similar to that of the gear pump disclosed in Japanese Patent Laid-Open No. 57-79290, or a curve similar to the trochoidal curve. On the other hand, the top part 30 of the outward meshing tooth 17 has a circular arc part 30a at its center that has a radius R1 and contacts the top part 20 of the inward meshing tooth 16 at the sealing point P1 (there may be a slight gap). It consists of straight portions 30b and 30c extending straight toward engagement starting points P2 and P3 of surfaces 17a and 17b.

The radius R1 of this arcuate portion 30a is set smaller than the radius R2 of the arcuate portion in the conventional gear pump shown by the dotted line in FIG. Also, the straight part 3
0b and 30c are also retracted rearward from the conventional arcuate portion where the entire apex is an arc, as indicated by the dotted line in FIG. 4, and therefore contact between the two at position A or position B can be prevented.

Note that the arcuate portion 30a and the straight portions 30b, 30
The joints with c and the joints between the straight portions 30b, 30c and the tooth surfaces 17a, 17b are connected by appropriate circular arcs, and the joints are corrected so that they do not form acute angles.

Further, the shape of the bottom of the inward meshing tooth 16 of the driven gear 14 is formed in such a shape that a slight clearance is secured between the bottom of the inward meshing tooth 16 and the top portion 30 of the external meshing tooth 17.

<Effects of the Invention> As described above, the gear pump of the present invention has a circular arc portion at the top of the external gear of the drive gear whose radius is smaller than the radius of the curve created by the inward meshing teeth or the circular arc approximating the curve. A straight part is formed in the center and between this circular arc part and the meshing start point of the tooth surface, and a straight part is formed that connects the end of the circular arc part and the meshing start point straight, so that sealing is not required. There is no contact between the tops of the inwardly meshing teeth and the outwardly meshing teeth, which has the advantage of preventing noise generation.

[Brief explanation of drawings]

FIG. 1 is an overall view of a conventional gear pump, FIG. 2 is a sectional view showing an embodiment of the gear pump of the present invention, and FIG.
The figure is an enlarged cross-sectional view taken along the line -- in FIG. 2, and FIG. 4 is an enlarged view showing the relationship between the inward meshing teeth and the outward meshing teeth. 14...driven gear, 15...drive gear, 1
6...Inward meshing tooth, 17...Outward meshing tooth, 20...Top part, 30...Top part, 30a...Circular arc part, 30a, 30
c...Straight line portion, P1...Seal point, P2, P3...Meshing start point.

Claims (1)

[Claims] 1. A driven gear and a drive gear, the driven gear is formed with inward meshing teeth having a tooth surface formed of a trochoidal curve, and the drive gear is formed with outward meshing teeth formed of a trochoidal curve and meshing with the inward meshing teeth. In the gear pump, the outward meshing teeth of the drive gear have a circular arc portion formed at the center of the top thereof with a radius smaller than the radius of the curve created by the internal meshing teeth or an arc approximating the curve, and the circular arc portion A gear pump characterized in that a straight portion is formed between the mesh start point of the tooth surface and the mesh start point of the tooth surface to connect the end of the circular arc portion and the mesh start point in a straight line.