JP2007120465A - Pump rotor and internal gear type pump using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an internal gear type pump capable of restraining meshing noise and tooth hitting noise of a pump rotor, and capable of reducing noise and vibration caused by the meshing noise or the tooth hitting noise. <P>SOLUTION: At least one of an inner rotor 2 and an outer rotor 3 is formed by a sintered material having the porosity of 17% or more, and the pump rotor 4 wherein the inter rotor 2 and the outer rotor 3 are eccentrically arranged and combined is housed in a casing 5 having a suction port 6 and a discharge port 7, and the internal gear type pump 1 is obtained. In the sintered material having the enhanced porosity, impact noise is attenuated compared to the one in the sintered material having the low porosity (high density), and damping performance of sound is also enhanced, and thereby, noise and vibration of the pump having the rotor can be reduced. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a pump rotor configured by combining an inner rotor and an outer rotor and an internal gear type pump using the pump rotor. More specifically, the engagement noise and the tooth contact noise between the inner rotor and the outer rotor are reduced, and the engagement noise is reduced. The present invention relates to a pump rotor that reduces noise and vibration during pump operation caused by tooth contact noise, and an internal gear pump using the pump rotor.

  Internal gear pumps are widely used as oil pumps for car engines and automatic transmissions. This internal gear type pump employs a pump rotor in which an inner rotor having external teeth and an outer rotor having internal teeth are combined in an eccentric arrangement, and tooth engagement noise and tooth contact noise are generated when the rotor rotates. .

  Since the meshing sound and the tooth contact sound cause the noise and vibration of the pump, it is desired to be as small as possible.

In order to meet the demand, Patent Document 1 below discloses that a shaft mounting portion on which the rotating shaft of the inner rotor is mounted is made of a high-strength, high-density sintered material, and an outer peripheral portion meshing with the outer rotor has a lower density than the shaft mounting portion. Disclosed are internal gear type oil pumps each formed of a vibration-damping sintered material. Further, in Patent Document 2, the inner rotor is a sintered forged rotor, the density of the outer peripheral portion meshing with the outer rotor of the inner rotor is 7.7 g / cm ³ or more, and the density of the inner peripheral portion having the center hole is 6. Disclosed is a sintered forged rotor for gear pumps of 6 to 7.6 g / cm ³ .

  As a material for the pump rotor, a sintered material by powder metallurgy is generally widely used as an inexpensive industrial product. Patent Documents 1 and 2 also employ the sintered material. However, the oil pump disclosed in Patent Document 1 is sintered with higher density on the inner peripheral side where the rotating shaft of the inner rotor is mounted than on the outer peripheral side. The material is made of a material to suppress noise and vibration, and since two types of materials are used for one rotor, the inner rotor has a composite structure, resulting in a reduction in productivity and an increase in cost.

In the rotor disclosed in Patent Document 2, the outer peripheral side of the inner rotor is formed of a sintered material having a higher density than the inner peripheral side on which the rotating shaft is mounted. Since the difference is applied by controlling the amount of compression during forging, the number of manufacturing steps is increased as compared with a single material. In addition, since this rotor is made of a sintered material having a density higher than that of a general sintered material, the portion that generates a meshing sound and a tooth contact sound is effectively reduced. Is estimated to be difficult.
Japanese Utility Model Publication No. 5-77587 JP-A-6-50269

  An object of the present invention is to reduce the noise and vibration of the internal gear pump caused by the meshing sound and the tooth contact sound by suppressing the meshing sound and the tooth contact sound of the pump rotor.

  In order to solve the above problems, in the present invention, at least one of the inner rotor and the outer rotor constituting the pump rotor is formed of a sintered material having a porosity of 17% or more. The pump rotor is housed in a casing having a suction port and a discharge port to constitute an internal gear type pump.

  The present invention is preferably applied to a pump rotor in which an inner rotor having n teeth and an outer rotor having (n + 1) teeth are combined, or an internal gear pump using the pump rotor. It can also be applied to an internal gear type pump having one or more teeth. In both types of pumps, if both the inner rotor and the outer rotor are formed of a sintered material having a porosity of 17% or more, a better effect can be obtained with respect to noise and vibration reduction.

  A sintered material having a porosity of 17% or more employed as a rotor material is an alloy in which at least one metal element selected from Ni, Mo, and Mn is added to an Fe—Cu—C-based material. What is formed with a powder and what is formed with the powder of the alloy which added at least 1 sort (s) of the metal element chosen from Ni, Mo, Mn, and Cr to the Fe-C type material are preferable.

  In this invention, the porosity of the sintered material constituting the rotor is increased to reduce the meshing noise and the tooth contact noise between the inner rotor and the outer rotor. Sintered materials with low porosity emit a loud sound when they collide with each other, but as the porosity increases, the impact sound becomes dull and the sound attenuation performance increases. Therefore, in the pump rotor of the present invention in which the porosity of the material is larger than that of the conventional one, the meshing noise and the tooth contact noise are smaller than those of the conventional product, and the noise and vibration of the pump using this are reduced.

  The lower limit of the porosity of the sintered material characterizing the present invention is 17%. Generally, the porosity of the sintered material employed in the pump rotor is around 10%, so 17% can be said to be a considerably large porosity. As the porosity increases, the noise and vibration reduction effect increases. However, if the porosity exceeds 25%, powder molding becomes difficult, so the upper limit of the porosity seems to be 25%.

  Next, as a sintered material for a rotor of an internal gear type pump, generally, an Fe-Cu-C-based material or an Fe-C-based material is used, but both increase strength and teeth when the porosity is increased. The surface hardness decreases. If this makes it impossible to meet the required pump specifications and usage conditions, measures will be taken to increase the strength of the material. Specifically, at least one metal element selected from Ni, Mo, and Mn is 1.5 to 5.0% by weight with respect to the Fe—Cu—C-based material. In this range, Mo is added in a range of 0.2 to 1.5%, and Mn is added in a range of 0.3 to 1.0%. In addition, at least one metal element selected from Ni, Mo, Mn, and Cr, with respect to Fe-C materials, Ni is in a range of 1.0 to 3.0% by weight. , Mo is added in a range of 0.5 to 2.5%, Mn is added in a range of 0.3 to 1.0%, and Cr is added in a range of 0.5 to 1.5%. Addition of the alloy element can compensate for a decrease in strength and a decrease in tooth surface hardness due to an increase in porosity.

  1 and 2 show an embodiment of a pump rotor and an internal gear pump according to the present invention. The illustrated internal gear pump 1 comprises a pump rotor 4 by combining an inner rotor 2 having n teeth (n = 9 in the figure) and an outer rotor 3 having (n + 1) teeth. The rotor 4 is configured to be accommodated in a casing 5 having a suction port 6 and a discharge port 7.

  The inner rotor 2 and the outer rotor 3 are arranged eccentrically so that the outer teeth 2a and the inner teeth 3a mesh with each other. In the present invention, at least one of the inner rotor 2 and the outer rotor 3 is formed of a sintered material having a porosity of 17 to 25% to reduce meshing noise and tooth contact noise. The other rotor may be a forged or cast material machined or the like, but it is better to combine both the inner rotor 2 and the outer rotor 3 with a sintered material having a porosity of 17 to 25% and combine them. The effect can be expected.

  Reference numeral 8 in FIGS. 1 and 2 denotes a rotating shaft, and the inner rotor 2 is fixed to the rotating shaft 8. When the inner rotor 2 is rotated by driving the rotary shaft 8, the outer rotor 3, which is a driven gear, is also rotated, and a volume change of the pumping chamber 9 formed between the rotors 2 and 3 occurs to suck in liquid. Discharge is made.

  At this time, the meshing portions of the teeth 2a and 3a of the inner rotor 2 and the outer rotor 3 rub against each other, and the phenomenon in which the teeth 2a and 3a strike each other due to the rotation of the rotating shaft 8 occurs. No. 1 is such that at least one of the inner rotor 2 and the outer rotor 3 is formed of a sintered material having a higher porosity than the conventional one, so that it is difficult for sound to be generated and the performance of attenuating the generated sound is high. Therefore, compared with a conventional pump in which the rotor is formed of a sintered material having a low porosity, the meshing sound and the tooth contact sound are reduced, and the noise and vibration caused by the meshing sound and the tooth contact sound are reduced.

  A rotor with a porosity of 17% or more is a Fe-Cu-C-based material having a Cu content of 1.0 to 2.5 wt% and a C content of 0.2 to 1.2 wt%. Ni, Mo, Mn sintered alloy having a composition added with at least one metal element selected from Ni, Fe-C based material having a C content of 0.2 to 1.2 wt%, Ni It is preferable to form a sintered alloy having a composition to which at least one metal element selected from Mo, Mn, and Cr is added. These sintered alloys can compensate for a decrease in strength and a decrease in tooth surface hardness due to an increase in porosity by increasing the strength of the alloy with an additive element. The Fe-Cu-C-based material has a sufficient effect of adding Ni, Mo, and Mn with Ni being 1.5 wt% or more, Mo being 0.2 wt% or more, and Mn being 0.3 wt% or more. In addition, Ni is added at 5.0 wt% or less, Mo is 1.5 wt% or less, and Mn is 1.0 wt% or less to suppress the cost increase. For the same reason, the Fe-C material is Ni in the range of 1.0 to 3.0 wt%, Mo is in the range of 0.5 to 2.5 wt%, Mn is in the range of 0.3 to 1.0 wt%, Cr Is in the range of 0.5 to 1.5 wt%.

The results of tests conducted to confirm the effects of the present invention are described below. The test first examined the correlation between the porosity of the sintered material and the sound decay time.
After molding the powder having the composition shown in Table 1 at a molding pressure that gives a predetermined porosity, 1130 ° C.
A hollow disk test piece having an outer diameter of 60 mm, an inner diameter of 10 mm, and a thickness of 10 mm was prepared. The obtained test piece was suspended with a sewing thread so as to be able to freely vibrate, and a 3/8 inch bearing steel ball was suspended from a certain height by rolling an inclined surface with an inclination angle of 45 ° ( It was made to collide with the end face of the disk from a right angle direction. The impact sound generated at this time is measured with a sound level meter at a fixed distance from the test piece, and the time change of the noise level is recorded. The time until the noise level is attenuated to 70% from the maximum noise level at the beginning of the collision ( Table 1 and FIG. 3 show the results of measuring 70% decay time for each test piece.

  The shorter the attenuation time, the higher the noise (vibration) attenuation performance, and the more effective the material is against noise and vibration.

  In any material, it can be seen that the decay time is rapidly shortened at a porosity of 17% or more, and the damping effect is high.

Next, using a sintered material having a composition of Fe-2 wt% Cu-1 wt% C, a pump rotor (invention product) in which the porosity of the inner rotor and outer rotor was about 17% was prepared. In addition, a pump rotor (conventional product) in which the porosity of the inner rotor and the outer rotor is about 10% (density is about 7.0 g / cm ³ ) was also made using the same material. Inventive and conventional pump rotors are housed in casings to form internal gear pumps. These pumps are operated under the conditions of rotational speed: 1750 rpm and discharge pressure: 0.3 MPa to generate vibration. As a result of the measurement, the vibration of the inventive pump was smaller than the vibration of the conventional pump as shown in FIG.

  An inner rotor having a porosity of about 20% was prepared using a sintered material having the composition shown in Table 2, and the strength (tensile strength) and tooth surface hardness of each rotor were examined. The results are also shown in Table 2.

  As can be seen from this test result, a sintered alloy having a composition in which at least one metal element selected from Ni, Mo and Mn is added to an Fe—Cu—C based material, or an Fe—C based material The inner rotor formed of a sintered alloy having a composition in which at least one metal element selected from Ni, Mo, Mn, and Cr is added to the Fe-Cu-C type or Fe It is higher than a rotor made of a general sintered material of -C type, and the decrease in strength and tooth surface hardness due to an increase in porosity can be compensated by increasing the strength of the material.

Sectional drawing which shows an example of the internal gear type pump of this invention Sectional view along line XX in FIG. Chart showing the results of investigating the correlation between porosity and generated sound of sintered materials Chart showing vibration comparison results of the pumps of the invention and conventional products

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal gear type pump 2 Inner rotor 2a External tooth 3 Outer rotor 3a Internal tooth 4 Pump rotor 5 Casing 6 Intake port 7 Discharge port 8 Rotating shaft 9 Pumping chamber

Claims (5)

  A pump rotor in which at least one of an inner rotor and an outer rotor is formed of a sintered material having a porosity of 17% or more, and the inner rotor and the outer rotor are arranged eccentrically.   The pump according to claim 1, wherein an inner rotor having n teeth and an outer rotor having (n + 1) teeth are combined, and both the inner rotor and the outer rotor are formed of a sintered material having a porosity of 17% or more. Rotor.   The sintered material having a porosity of 17% or more is formed of an alloy powder obtained by adding at least one metal element selected from Ni, Mo, and Mn to a Fe-Cu-C-based material. The pump rotor according to 1 or 2.   The sintered material having a porosity of 17% or more is formed of an alloy powder in which at least one metal element selected from Ni, Mo, Mn, and Cr is added to an Fe-C-based material. The pump rotor according to 1 or 2.   An internal gear pump constructed by housing the pump rotor according to any one of claims 1 to 4 in a casing having a suction port and a discharge port.

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