JP2007085259A - Internal gear pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a large pressure difference from occurring in right and left side-clearance parts formed between the side faces of a pump rotor and a case in an internal gear pump. <P>SOLUTION: In this internal gear pump, the housing side corner shape and cover side corner shape of a rotor chamber 3 formed in the case and the housing side outer peripheral corner shape and cover side outer peripheral corner shape of an outer rotor 5 are both set asymmetrical. The setting of the asymmetry is performed so that the corners of the outer rotor 5 are away from the case 2 on the side where the corners of the rotor chamber 3 are recessed inward and the corners of the outer rotor 5 are close to the case 2 on the side where the corners of the rotor chamber 3 are projected outward. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an internal gear type pump that enhances the effects of preventing seizure of a pump rotor and suppressing wear.

  As shown in FIG. 9, the internal gear pump is configured by housing a pump rotor 1 in a rotor chamber 3 provided in a case 2. As the pump rotor 1, a combination of the inner rotor 4 and the outer rotor 5 in an eccentric arrangement is used. When the inner rotor 4 of the pump rotor is rotated by the drive shaft 6, the outer rotor 5 is driven to rotate, and the volume change of the pumping chamber 7 formed between the inner rotor 4 and the outer rotor 5 occurs to suck and discharge fluid. Is made.

  As the case 2 of the internal gear type pump, a combination of a housing 2a and a cover 2b is employed. The housing 2a is provided with a recess for forming a rotor chamber, and the cover 2b seals the opening of the recess to create the rotor chamber 3. A suction port 8 and a discharge port 9 are also formed in the housing 2a. The suction port 8 and the discharge port 9 may also be formed on the cover 2b in order to keep the balance of pressure applied opposite to both side surfaces of the pump rotor 1.

By the way, the recess provided in the housing 2a is finished using a milling tool such as an end mill. At this time, an R surface 10 shown in FIG. 10 and a flat chamfer surface 11 shown in FIG. 11 are formed at the corner of the recess (the housing side corner of the rotor chamber 3). Further, in order to avoid interference with the R surface 10 and the chamfer surface 11, as shown in FIG. 12, chamfered portions 12 having the same specifications and the same size are formed at the left and right corners of the outer periphery of the outer rotor 5. Is done.

  FIG. 12 shows a state in which the R-side 10 is formed in the housing-side corner of the rotor chamber 3 and the outer rotor 5 in which the chamfered portions 12 are formed in the left and right corners of the outer periphery is accommodated in the rotor chamber 3. In the same figure, 13 and 14 are side clearance portions formed between both side surfaces of the outer rotor 5 and the case 2, and 15 is an outer clearance portion formed between the outer periphery of the outer rotor 5 and the case 2. Show.

  If the outer rotor 5 has a centrally symmetric shape, the direction of the outer rotor 5 when assembled in the case is lost, and the outer rotor 5 is easy to assemble. For this purpose, the chamfered portions 12 are provided at the left and right corners of the outer periphery of the outer rotor 5, respectively, and this causes the pressure balance between the left and right side clearance portions generated between the side surfaces of the pump rotor 1 and the case 2 to be lost. An undesirable situation occurs.

  In the internal gear type pump, fluid leakage from the side clearance portions 13 and 14 is inevitable. The liquid flowing into the side clearance portions 13 and 14 leaks out to the suction port 8 side via the outer peripheral rear lance portion 15 generated between the outer rotor 5 and the case 2. At this time, the side clearance portion 13 side has an R surface 10 that enters the inside, so the outflow resistance of the liquid is large. If the pump rotor 1 is pressed against the cover 2b due to the pressure difference in the side clearance portion, troubles such as seizure of the rotor and acceleration of wear may occur. The pressure difference between the side clearance portions 13 and 14 tends to be particularly large when the size of the outer peripheral clearance portion is larger than that of the side clearance portion, and the possibility of rotor seizure increases.

The following Patent Document 1 mentions prevention of seizure and wear of the rotor. In the technique of this document, grooves are formed on both sides of the inner rotor and both sides of the outer rotor, and hydraulic pressure is introduced into the grooves from the pumping chamber, and the pump rotor is pushed away from both the housing and the cover by the hydraulic pressure. . In this way, the seizure and wear of the rotor are prevented, but even in this structure, it is considered that a hydraulic pressure difference due to a difference in the outflow resistance of the liquid occurs in the left and right side clearance parts. It becomes easy to generate | occur | produce the said malfunction by being pressed.
JP 2000-192889 A

  In the internal gear type pump, the present invention prevents a large pressure difference from being generated in the left and right side clearance portions formed between both side surfaces of the pump rotor and the case, and thereby the left and right side clearance portions. It is an object of the present invention to prevent the pump rotor from being pressed against the case by the pressure difference and to suppress the seizure and wear of the pump rotor.

  In order to solve the above problems, in the present invention, the housing-side corner shape and the cover-side corner shape of the rotor chamber and the housing-side outer periphery corner shape and the cover-side outer periphery corner shape of the outer rotor are both set asymmetrically. Also, the asymmetrical shape of the corner shape is set so that the corner of the rotor chamber escapes from the case on the side where the corner of the rotor chamber enters, and the corner of the outer rotor approaches the case on the side where the corner of the rotor chamber escapes outside. Do. And the pump rotor comprised combining an outer rotor with an inner rotor in the said rotor chamber is accommodated, and an internal gear type pump is comprised.

  As the housing-side corner of the rotor chamber, a corner having an R surface and a chamfer surface that enter the inside, and a corner formed with a recess that escapes to the outside can be considered. Further, as the cover-side corner of the rotor chamber, a right-angled corner or a corner formed with a recess that escapes to the outside can be considered.

On the other hand, corners on the outer periphery of the outer rotor may be right-angled corners with no chamfered corners, corners with chamfered corner edges, or corners with different chamfering amounts or chamfered shapes. The size of the gap between the case and the outer rotor at the left and right outer peripheral corners is adjusted.
In this way, the corner of the rotor chamber escapes from the case on the side where the corner of the rotor chamber enters so that the pressure balance of the left and right side clearance portions formed between the both sides of the pump rotor and the case can be maintained. On the side where the corner of the chamber escapes outside, the corner of the outer rotor approaches the case.

As a specific combination example of the rotor chamber and the outer rotor,
(1) An inward entry portion is formed in the housing side corner, the cover side corner is a right angle corner, a chamfered portion is formed in each of the housing side outer periphery corner and the case side outer periphery corner. Combination of outer rotor with chamfer dimension larger than chamfer dimension of cover side outer periphery corner,
(2) A rotor chamber in which a relief recess is formed in the housing side corner, the cover side corner is a right angle corner, and a chamfered portion is formed in the cover side outer periphery corner, and the housing side outer periphery corner is an outer corner in which there is no chamfered portion. Combinations of rotors are conceivable, and either of them can be used to achieve the object of the invention.

  The present invention can be expected to have a particularly great effect in a pump having a larger outer clearance than the side clearance and a rotational speed of 3000 rpm or less.

  The left and right corner shapes of the rotor chamber may be asymmetrical due to processing restrictions, etc., and at this time, in this invention, the outer corner shape of the outer rotor is asymmetrical due to the difference between the left and right corner shapes. Prevents the pressure balance from breaking in the left and right side clearances.

  The rotor chamber and outer rotor have asymmetrical corner shapes on the housing side and cover side of the case (hereinafter referred to as the left and right corner shapes), and the outer rotor corner is the case on the side where the corner of the rotor chamber enters. When the outer rotor corner is on the side where the outer corner of the rotor chamber escapes, the outer rotor corner is close to the case, and the gap between the outer rotor and the case at the left and right corners and the liquid outflow resistance are large. There is no difference. For this reason, the pressures on the left and right side clearances are balanced or reduced to a negligible level, and the rotor is no longer pressed against the case due to the pressure difference between the left and right side clearances. The undesirable situation is avoided.

  In addition, the internal gear type pump in which the dimension of the outer periphery clearance portion formed between the outer periphery of the outer rotor and the case is larger than the left and right side clearance portions formed between the both side surfaces of the outer rotor and the case, A pressure difference is likely to occur in the left and right side clearances. Further, when the rotational speed is 3000 rpm or less, the pressure difference between the left and right side clearance portions tends to be larger than the rotational speed of 3000 rpm or more. Therefore, the present invention is particularly effective for a pump having a larger outer clearance than the side clearance and a rotational speed of 3000 rpm or less.

  An embodiment of an internal gear pump according to the present invention will be described with reference to FIGS. As shown in FIG. 1, the internal gear pump of the present invention has a pump rotor 1 in which an inner rotor 4 having n teeth and an outer rotor 5 having (n + 1) teeth are combined in an eccentric arrangement. 2 is housed in the rotor chamber 3 provided in FIG.

  As shown in FIG. 2, the case 2 includes a housing 2 a in which a concave portion that becomes the rotor chamber 3 is formed on one side surface, and a cover 2 b that seals the entrance of the concave portion. A suction port 8 and a discharge port 9 are formed in the housing 2a and the cover 2b, respectively. The corner of the recess provided in the housing 2a, that is, the housing side corner of the rotor chamber 3 is provided with an R surface 10 (or the chamfer surface 11 of FIG. 11), while the cover side corner of the rotor chamber 3 is It is formed in a right angle corner.

  Chamfered portions 12 </ b> R and 12 </ b> L are provided on the housing-side outer periphery corner (the right outer periphery corner in FIG. 2) and the cover-side outer periphery corner of the outer rotor 5, respectively. The chamfered portion 12L is small in size. On the other hand, the chamfered portion 12R is a large chamfered portion, and the chamfered portions 12R and 12L are the portions narrowed by the R surface 10 in which the gap in the corner portion between the outer rotor 5 and the housing 2a enters the inside. It is compensated by the dimensional difference.

  Therefore, the outflow resistance of the liquid between the right side clearance portion 13 and the outer peripheral clearance portion 15 in FIG. 2 generated between the outer rotor 5 and the housing 2a, and the left side clearance portion 14 and the outer periphery in FIG. The liquid outflow resistance with the clearance 15 is approximated, and the pressure of the side clearances 13 and 14 is balanced, or the pressure difference between the side clearances 13 and 14 is reduced to a negligible level. The pump rotor 1 will not be pressed tightly against the cover 2b due to the hydraulic pressure difference of the side clearance portion.

  FIG. 3 shows another combination example of the corner shape of the rotor chamber 3 and the outer rotor 5. Even in the structure in which the recess 16 for relief is provided in the housing side corner of the rotor chamber 3 in place of the R surface 10 and the chamfer surface in place of the R surface 10 in FIG. 2, a corner that avoids stress concentration can be formed by machining. it can. In this case, since the case escapes to the outside, the outer peripheral corner of the outer rotor 5 on the housing side is either a corner without a chamfered portion or the chamfering amount is reduced. Since the cover side corner of the rotor chamber 3 is a right angle corner like the conventional product, the cover side outer periphery corner of the outer rotor 5 may be provided with a chamfered portion 12 similar to the conventional one.

  Note that the relief recess 16 provided in the housing side corner of the rotor chamber 3 may be formed by recessing the outer peripheral side of the corner of the rotor chamber 3 as shown in FIG. Further, the chamfered portion 12 on the outer periphery of the outer rotor is a chamfered portion 12A with an R surface as shown in FIG. 5 or a chamfered portion 12B with a step as shown in FIG. There is no problem.

  A prototype (invention product) and a comparison product of the internal gear pump of this invention were prepared. Each of the prototype and the comparative product is configured by housing a pump rotor, which is a combination of an inner rotor having seven teeth and an outer rotor having eight teeth, in a rotor chamber of the case. In both the prototype and the comparative product, the pump rotor has an outer diameter of φ80 mm and a thickness of 15 mm. The prototype has the structure of FIG. 1 in which a rotor chamber having a left-right asymmetric corner and an outer rotor having a left-right asymmetric outer periphery corner are combined, while a comparative product has a rotor chamber having a left-right asymmetric corner. The structure shown in FIG. 12 is combined with an outer rotor having a symmetrical outer peripheral corner. The dimensions of the side clearance part were 0.03 mm on the housing side, 0.02 mm on the cover side, and the dimension of the outer peripheral clearance part was 0.06 mm.

  The prototype and the comparative product are operated under the discharge pressures of 1 MPa, 2 MPa, 3 MPa, rotation speeds of 1500 rpm, 2000 rpm, and 3000 rpm, respectively, and the pressure of the left and right side clearance portions on the discharge side, that is, the pressure of the housing side clearance portion The pressure at the cover side clearance was measured. The results are shown in FIGS.

  FIG. 8 shows the measurement data of the comparative product. When the discharge pressure is 1 MPa, there is no significant difference in the pressure between the left and right side clearance portions. However, when the discharge pressure is 2 MPa, when the rotational speed is 1500 rpm, a pressure difference exceeding 500 kPa is generated in the pressure of the left and right side clearance portions. Further, when the discharge pressure becomes 3 MPa, a very large pressure difference is generated between the left and right side clearance portions at the rotation speeds of 1500 rpm and 2000 rpm.

  On the other hand, as shown in FIG. 7, the prototype has a pressure difference of 500 kPa or less between the left and right side clearance sections under any of the discharge pressures of 1 MPa, 2 MPa, 3 MPa, the rotational speed of 1500 rpm, 2000 rpm, and 3000 rpm. It is suppressed. From this test result, when the left and right corner shapes of the rotor chamber are asymmetric, the left and right outer peripheral corner shapes of the outer rotor are also asymmetric, and the size of the gap between the outer rotor and the case at the left and right corner portions is averaged. It can be clearly seen that it is effective to adjust in the direction of the movement.

Side view showing an example of the internal gear pump of the present invention with the cover of the housing removed 1 is a cross-sectional view of the internal gear pump of FIG. 1 taken along line X-X in FIG. Sectional drawing which shows the other example of the internal gear type pump of this invention Sectional drawing which shows the example of a position change of the recessed part for relief provided in the housing side corner of a rotor chamber Sectional drawing which shows the other example of the outer periphery corner shape of an outer rotor Sectional drawing which shows the further another example of the outer periphery corner shape of an outer rotor The figure which shows the measurement data of the pressure difference of the side clearance part of the invention Figure showing the measurement data of the pressure difference in the side clearance part of the comparative product Sectional view showing the outline of the internal gear pump Sectional drawing which shows an example of the housing side corner shape of a rotor chamber Sectional drawing which shows the other example of the housing side corner shape of a rotor chamber The figure which shows the corner shape of the rotor chamber and outer rotor outer periphery of the conventional internal gear type pump

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pump rotor 2 Case 2a Housing 2b Cover 3 Rotor chamber 4 Inner rotor 5 Outer rotor 6 Drive shaft 7 Pumping chamber 8 Suction port 9 Discharge port 10 R surface 11 Chamfer surface 12, 12R, 12L, 12A, 12B Chamfer 13,14 Side clearance 15 Outer clearance 16 Relief recess

Claims (4)

  The housing-side corner shape and cover-side corner shape of the rotor chamber provided in the case, and the outer-side housing-side outer corner shape and the cover-side outer corner shape of the outer rotor are set asymmetrically. The outer rotor corner escapes from the case on the inward side, and the outer rotor corner approaches the case on the side where the rotor chamber corner escapes, and the outer rotor is combined with the inner rotor. An internal gear pump in which a pump rotor to be stored is housed in the rotor chamber.   The housing side corner is formed with an inward entry, the cover side corner is a right angle corner, and the chamfered portion is formed in each of the housing side outer periphery corner and the case side outer periphery corner. The internal gear type pump according to claim 1, further comprising an outer rotor that is made larger than a chamfer dimension of the cover-side outer peripheral corner.   The housing side corner has a relief recess, the cover side corner has a right angle corner, the cover side outer corner has a chamfered portion, and the housing side outer corner has a chamfered outer rotor. The internal gear pump according to claim 1.   The dimension of the outer periphery clearance part formed between the outer periphery of an outer rotor and a case is larger than the dimension of the left and right side clearance part formed between both side surfaces of the outer rotor and the case. The internal gear pump according to any one of the above.

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