JPH01182585A - Plastic gear pump - Google Patents

Abstract

PURPOSE:To remove an adverse effect caused by the clamping of bolts at the time of high temperature in a gear pump in which a plurality of gears provided in a case are covered with a cover by forming the bolts for fixing the cover to the case with a material having an equal thermal expansion coefficient to that of the case. CONSTITUTION:In a gear pump, e.g., a trochoid pump, a gear 3 as an inner rotor is engaged with a gear 2 as an outer rotor which is rotatably fitted in a case 1. A cover 4 for covering the gears 2, 3 is fixed to the case 1 via bolts 5. Each component 1-4 is formed with a plastic. In this structure, the bolts 5 are formed with a plastic material having the equal thermal expansion coefficient to the plastic material forming the case 1. Thereby, at the time of the high temperature of the gear pump, the bolts 5 are thermally expanded equally to the case 1 to remove an adverse effect caused by the clamping of the bolts 5.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a gear pump, and particularly to a gear pump in which each component is made of plastic.

[Conventional technology]

A plastic gear pump, such as a trochoid pump, is constructed as shown in Figs. 1 and 2, with a gear (outer rotor) 2 rotatably fitted in a case 1 and a gear 3
(Inner rotor) 3 are engaged with each other and closed by a cover 4, and each of these constituent members is made of plastic. The cover 4 is fixed to the case 1 with bolts 5.

Cover 4 of this conventional plastic trochoid pump
Steel bolts 5 were used to secure the parts.

[Problem that the invention seeks to solve]

Disadvantages of plastics include (low Bpv value, (2) large coefficient of thermal expansion, about 10 times that of steel, (3) low modulus of longitudinal elasticity, about 1/100 of that of steel, (4) poor material properties at high temperatures. However, because the coefficient of thermal expansion is particularly large, if the structural members are fixed with bolts 5 made of steel with a small coefficient of thermal expansion as in the past, as shown by the intersecting diagonal lines in Fig. 2, The periphery of the bolt 5 is affected by the tightening of the bolt 5, and even if the temperature rises, the tightening of this part remains unchanged, and the gap between the gear (outer rotor) 2, the case 1, and the cover 4 is maintained. gear (outer rotor)
2. Galling may occur.

In order to avoid being affected by the tightening of the bolts mentioned above, the bolts 5 should be tightened to the outside, away from the gear (outer rotor) 2, as shown by the imaginary line in Figure 1. In this case, the outer size of case 1 becomes large.

[Means and effects for solving the problems] The present invention has been made in consideration of the above-mentioned problems, and has the following features: It is possible to reduce the gap for the gear, improve volumetric efficiency, and reduce the external size. In this plastic gear pump, the case, gear, cover, etc. are made of plastic, and the bolts for assembling and fixing the above components have a coefficient of thermal expansion equivalent to that of the case. It is constructed of material, and when the case thermally expands due to a rise in temperature, the bolts also expand thermally in approximately the same way as the case, and there is no effect from tightening the bolts.

〔Example〕

In the present invention, the bolt 5 is made of the same material as the case 1, for example, nylon (trade name) reinforced with glass fiber.

By using the bolt 5 made of the above-mentioned plastic, its coefficient of thermal expansion is the same as that of case 1, and when the temperature rises, the bolt 5 thermally expands in the same way as case 1, and the bolt 5 is tightened. The part expands thermally at the same rate as other parts regardless of its tightening, and in case 1
The gap between the gear (outer rotor) and the gear (outer rotor) 2 does not change significantly when the temperature rises.

〔Effect of the invention〕

According to the present invention, the gap with respect to the gear (outer rotor) 2 can be reduced, and a plastic gear pump with excellent volumetric efficiency can be obtained. Further, the bolt 5 can be tightened near the gear 2, and the external size can be reduced.

[Brief explanation of the drawing]

Fig. 1 is a front view with the cover removed, and Fig. 2 is a sectional view showing the bolt tightening section. 21 is a case, 2.3 is a gear, 4 is a cover, and 5 is a bolt. Applicant Komatsu Manufacturing Co., Ltd. Representative Patent Attorney Masaaki Yonehara

Claims (1)

[Claims] A plastic gear pump in which the case 1, gears 2, 3, cover 4, etc. are made of plastic, and the bolts 5 for assembling and fixing the above components are made of a material having the same coefficient of thermal expansion as the case 1. plastic gear pump.