JP2006242119A - Pump rotor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pump rotor of improved seizing resistance while maintaining volume efficiency. <P>SOLUTION: Pump rotors 20, 30 used for an internal gear pump 10 transferring liquid by sucking and delivering liquid by volume change of a cell C formed between tooth flanks 21a, 31a of the both rotors 20, 30 when the both rotors mesh and rotate, are formed out of Fe-Cu-C based sintered material and have density of 6.6 g/cm<SP>3</SP>or more and 7.1 g/cm<SP>3</SP>or less. One end surfaces 20a, 30a facing a suction port 51 and a delivery port 52 of both end surfaces 20a, 20b, 30a, 30b crossing rotation axis lines O1, O2 at right angles are ground and another end surfaces 20a, 30a and opposite side another end surfaces 20b, 30b are not ground. Ten point height of irregularities Rz of one end surfaces 20a, 30a is smaller than that of another end surfaces 20b, 30b. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pump rotor used in an internal gear pump that sucks and discharges fluid by changing the volume of a cell formed between tooth surfaces of an inner pump rotor and an outer pump rotor.

  Conventionally, this type of pump rotor has been widely used for internal gear pumps such as automotive lubricating oil pumps and automatic transmission oil pumps (see, for example, Patent Document 1 below). The internal gear pump includes an inner pump rotor formed with outer teeth, an outer pump rotor formed with inner teeth meshing with the outer teeth, a suction port for sucking fluid, and a discharge port for discharging fluid When the two rotors mesh with each other and rotate, the fluid is sucked and discharged by the volume change of the cell formed between the tooth surfaces of the two rotors. .

  The two rotors are housed inside the casing in a state where one end surface orthogonal to the rotation axis thereof faces the suction port and the discharge port, and when these rotors are engaged and rotated, Are in sliding contact with both end surfaces orthogonal to the rotation axis of both rotors and the outer peripheral surface of the outer pump rotor.

Such an inscribed gear pump is generally disposed between a supply destination (for example, a cylinder head) of a fluid (for example, a lubricating oil) and an oil pan in which the fluid is stored, and the inscribed gear pump is a strainer. It is set as the structure connected with the oil pan via. When the inscribed gear pump is driven, the fluid in the oil pan is supplied from the strainer to the inside of the inscribed gear pump, and as described above, the fluid is sucked and discharged by the volume change of the cell as described above. By doing so, fluid is supplied to the cylinder head or the like.
JP 11-343985 A

  By the way, when the internal gear pump is driven and fluid is sucked from the suction port toward the one end surface, the other end surface opposite to the one end surface is caused by the fluid pressure of the fluid. Therefore, there is a possibility that seizure may occur on the other end face of the pump rotor while the inscribed gear pump is repeatedly used.

  In particular, when the internal gear pump is restarted, there is little or no fluid inside the pump, so that the other end surface of the pump rotor contacts the inner surface of the casing in a substantially unlubricated state. In addition, there is a possibility that the possibility of causing the seizure may be increased because the fluid pressure at the time of restart is in sliding contact with the inner surface being strongly pressed against the inner surface.

  The present invention has been made in view of such problems, and an object thereof is to provide a pump rotor having improved seizure resistance.

In order to solve the above problems, a pump rotor according to the present invention includes an inner pump rotor formed with external teeth, an outer pump rotor formed with internal teeth that mesh with the external teeth, and fluid is sucked. A suction port and a casing formed with a discharge port for discharging fluid, and by sucking and discharging fluid by a change in volume of cells formed between the tooth surfaces of both rotors when both rotors mesh and rotate. In a pump rotor used for an inscribed gear pump for conveying a fluid, the pump rotor is formed of a Fe-Cu-C-based sintered material and has a density of 6.6 g / cm ³ or more and 7.1 g / cm ³ or less. Of the end faces orthogonal to the rotation axis, one end face facing the suction port and the discharge port is a ground face, and the other end face opposite to the one end face is non-polished. Is a surface, said one end face is characterized in that the ten-point average roughness Rz is smaller than the end face of the other.

  According to this invention, since the other end surface is a non-grinding surface, when driving the inscribed gear pump, a part of the fluid is held in a minute hole opened in the non-grinding surface, In other words, a part of the fluid can be infiltrated into the surface layer portion of the non-ground surface. Further, since the other end face has a ten-point average roughness Rz larger than that of the one end face facing the suction port and the discharge port, the other end face holds more fluid than the one end face. It becomes possible. As described above, when the inscribed gear pump is driven, the lubricity between the inner surface of the casing and the other end surface can be improved more than between the inner surface of the casing and the one end surface.

  Accordingly, when the inscribed gear pump is driven to suck the fluid from the suction port toward the one end surface, the other end surface is strongly pressed against the inner surface of the casing by the fluid pressure of the fluid. Even in such a case, good lubricity is ensured between the other end surface and the inner surface of the casing, and seizure can be prevented from occurring on the other end surface.

  On the other hand, even when the inscribed gear pump is stopped after being driven, a part of the fluid is held in a minute hole opened in the non-grinding surface as described above, and the other end surface is A part of the fluid can be infiltrated into the surface layer portion. Therefore, when this inscribed gear pump is restarted after being stopped, a part of the fluid is oozed out of the hole and acts as a lubricating oil between the inner surface of the casing and the other end surface. Is possible. As a result, even if the other end surface of the pump rotor is strongly pressed against the inner surface of the casing by the fluid pressure at the time of restart, it is possible to interpose lubricating oil between the end surface and the inner surface. Thus, the occurrence of seizure can be reliably suppressed.

  Further, since the one end face facing the suction port and the discharge port is a ground surface, the flatness of the one end face, the dimensional accuracy of the tooth width of the pump rotor (size in the rotational axis direction), and the It becomes possible to ensure the same variation in the clearance between the one end face and the inner face of the casing. Thus, by making the other end surface a non-grinding surface, the fluid in the cell leaks between the both end surfaces of the pump rotor and the inner surface of the casing when the inscribed gear pump is driven, so that the volume efficiency is improved. It is possible to suppress the decrease to the minimum.

Moreover, since the pump rotor is formed of Fe-Cu-C-based sintered material with a density of 6.6 g / cm ³ or more and 7.1 g / cm ³ or less, the fracture strength of the pump rotor and It becomes possible to ensure the necessary minimum surface pressure strength. Here, the pump rotor is formed by molding a green compact, firing it, further sizing it, and then grinding the surface corresponding to the one end face. However, since the rotor is made of the material and the density, at the time of the sizing process, the intersecting ridge line portion between the both end surfaces and the tooth surface of the pump rotor is crushed, and the chamfering amount of the ridge line portion is reduced. It becomes possible to suppress the increase. This makes it possible to prevent the fluid in the cell from leaking from the intersecting ridge line portion between the both end surfaces and the inner surface of the casing when the inscribed gear pump is driven. The cell partitioned by the tooth surface and the inner surface of the casing can be provided with high liquid tightness.

  Here, the intersecting ridge line portion between the other end surface and the tooth surface has a rising amount from the other end surface in the rotational axis direction of 0.01 mm or less and is directed from the tooth surface in the radial direction. It is desirable that the protruding amount be 0.05 mm or less.

  In this case, since the intersecting ridge portion is formed with the rising amount and the protruding amount, in the internal gear pump having this pump rotor, the intersecting ridge portion can be brought into contact with the inner surface of the casing. . As a result, the other end surface side of the cell is partitioned by the intersecting ridge line portion, the tooth surface, and the inner surface of the casing, so that when the internal gear pump is driven, the fluid in the cell is It is possible to reliably suppress leakage between the end surface and the inner surface of the casing. That is, since the other end surface is a non-ground surface and its flatness is reduced, the fluid in the cell leaks from the gap between the other end surface and the inner surface of the casing, and the internal gear pump A decrease in volumetric efficiency can be minimized.

In addition, by setting the rising amount within the above range, the inner edge of the other end surface is liable to be unevenly worn because the intersecting ridge line portion is in sliding contact with the inner surface of the casing in a limited manner. It is possible to avoid shortening the life of the contact gear pump.
In addition, by setting the protrusion amount within the range, it is possible to avoid that the intersecting ridge line portions are in contact with each other in the external teeth and the internal teeth, but the other portions are not in contact with each other during the meshing. It becomes possible. Thereby, each said cell can be divided reliably in the circumferential direction, and it can avoid that volumetric efficiency falls.

Furthermore, it is desirable that the outer peripheral surface of the outer pump rotor is a non-ground surface and the ten-point average roughness Rz is larger than that of the one end surface.
In this case, when the internal gear pump is driven and stopped after the driving, the outer peripheral surface of the outer pump rotor that is slidably in contact with the inner surface of the casing is also made to hold the fluid in the same manner as the other end surface. And seizure can be prevented from occurring on the outer peripheral surface.

  According to this invention, the seizure resistance of the pump rotor can be improved while maintaining the volumetric efficiency.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
The inscribed gear pump 10 shown in FIG. 1 meshes with each outer tooth 21 (n + 1), with an inner side pump rotor 20 formed with n (n is a natural number, n = 9 in the present embodiment) outer teeth 21. ) The outer side pump rotor 30 in which the inner teeth 31 of 10 sheets (in this embodiment) are formed, and the drive shaft 60 inserted into the mounting hole 22 formed in the inner side pump rotor 20, which are The casing 50 is housed inside.

Then, when the drive shaft 60 is rotated around the axis O1, the rotational driving force is transmitted to the mounting hole 22, the inner pump rotor 20 is also rotated around the axis O1, and the rotor 20 is further rotated. The rotational driving force is transmitted to the outer pump rotor 30 when the outer teeth 21 mesh with the inner teeth 31, and the rotor 30 is rotated about the axis O2.
At this time, both the rotors 20 and 30 are provided on the inner surface 50a of the casing 50 and both end surfaces in the direction of the rotation axes O1 and O2 of the rotors 20 and 30, in other words, both end surfaces 20a, 20b and 30a orthogonal to the rotation axes O1 and O2. 30b and the outer peripheral surface 30d of the outer pump rotor 30 are rotated while being in sliding contact with each other.

  Here, a plurality of cells C are formed between the tooth surfaces 21 a and 31 a of the inner side pump rotor 20 and the outer side pump rotor 30 along the rotational direction of the rotors 20 and 30. Each cell C is individually partitioned by contacting the outer teeth 21 of the inner side pump rotor 20 and the inner teeth 31 of the outer side pump rotor 30 on the front side and the rear side in the rotational direction of the rotors 20 and 30, respectively. In addition, both side surfaces are partitioned by an inner surface 50a of the casing 50, thereby forming an independent fluid transfer chamber. The cell C rotates with the rotation of the rotors 20 and 30 and repeats the increase and decrease in volume with one rotation as one cycle.

  The casing 50 is provided with a suction port 51 that communicates with the cell C when the volume increases, and a discharge port 52 that communicates with the cell C when the volume decreases, and the fluid sucked into the cell C from the suction port 51 Is conveyed with the rotation of the rotors 20 and 30 and discharged from the discharge port 52.

  Here, both the rotors 20 and 30 of the present embodiment are Fe-C-Cu based sintered materials containing at least 1 wt% to 4 wt% Cu and at least 0.2 wt% to 1.0 wt% C. For example, Fe-0.7C-2.0Cu or Fe-0.8C-1.5Cu-4.0Ni-0.5Mo is formed. For Cu, if it is less than 1%, the solid solution strengthening (hardness and strength) of Fe is insufficient, and if it exceeds 4%, expansion during sintering increases, making it difficult to form a rotor with high precision. Become. Regarding C, if it is less than 0.2%, solid solution strengthening (hardness and strength) to Fe becomes insufficient, and if it exceeds 1.0%, the fluidity of the powder at the time of powder molding decreases, It becomes difficult to make the density uniform over the entire area.

The rotors 20 and 30 have a density of 6.6 g / cm ³ or more and 7.1 g / cm ³ or less, and have both end faces 20a, 20b, 30a, and 30b orthogonal to the rotation axes O1 and O2. Of these, one end surface 20a, 30a facing the suction port 51 and the discharge port 52 is a ground surface, and the other end surface 20b, 30b opposite to the one end surface 20a, 30a is a non-ground surface. The end faces 20a and 30a have a ten-point average roughness Rz smaller than the other end faces 20b and 30b. In the present embodiment, the outer peripheral surface 30d of the outer pump rotor 30 is also a non-ground surface, like the other end surfaces 20b, 30b, and the ten-point average roughness Rz than the one end surfaces 20a, 30a. Has been increased.

  The ten-point average roughness Rz of the one end face 20a, 30a is 0.8 μm or more and 6.3 μm or less, and the ten-point average roughness of the other end face 20b, 30b and the outer peripheral face 30d of the outer pump rotor 30 is set. The thickness Rz is 4 μm or more and 10 μm or less. Within this numerical range, the one end face 20a, 30a has a ten-point average roughness Rz than the other end face 20b, 30b and the outer peripheral face 30d of the outer pump rotor 30. It has been made smaller. The rotors 20 and 30 have a porosity of 10% to 20%.

  In the present embodiment, the variation in the distance (tooth width) R1 between the both end faces 20a, 20b and 30a, 30b in each of the rotors 20, 30 is in the entire area of each end face 20a, 20b, 30a, 30b. , Within a range of 0.03 mm to 0.08 mm. As described above, the gap (side clearance) between the one end surfaces 20a, 30a of the rotors 20, 30 and the surface 50a of the casing inner surface 50a where the suction port 51 and the discharge port 52 are formed is the one side. It is set as the structure settled in the range of 0.06 mm or more and 0.14 mm or less over the whole end surface 20a, 30a.

  Furthermore, in this embodiment, in each of the rotors 20 and 30, the intersecting ridge line portions 20c and 30c between the other end surfaces 20b and 30b and the tooth surfaces 21a and 31a are rotated from the end surfaces 20b and 30b. The rising amount Y in the O1 and O2 directions is 0.01 mm or less, and the protruding amount Z in the radial direction from the tooth surfaces 21a and 31a is 0.05 mm or less. In other words, each of the intersecting ridge portions 20c and 30c has the rising amount Y and the protruding amount Z within the above ranges, and the inner side pump rotor 20 is projected radially outwardly in a curved shape. No. 30 is configured to be convex in a curved shape inward in the radial direction.

  Next, the manufacturing method of the inner side pump rotor 20 and the outer side pump rotor 30 comprised as mentioned above is demonstrated. Both rotors 20 and 30 both compress and mold powder to form a green compact, and then sinter the green compact, and then size it, and further, a surface corresponding to the one end face 20a or 30a. It is obtained by removing the flash generated in the whole after grinding only. First, a method for forming the green compact will be described.

  The main part of the powder molding apparatus 100 for forming the green compact is shown in FIGS. In these figures, reference numeral 110 is an upper punch, reference numeral 120 is a lower punch, reference numeral 130 is a core rod, reference numeral 140 is a die, reference numeral 150 is a shoe box, and reference numeral 160 is a measuring means for measuring the distance between both punches (lower dead center correction). Linear scale), P is a raw material powder.

  The die 140 is provided with a molding hole, and the core rod 130 is arranged at the center of the molding hole. A cylindrical space formed between the forming hole and the core rod 130 is closed by a cylindrical lower punch 120 fitted from below and a cylindrical upper punch 110 fitted from above, and the cavity 100a. It is said. The raw material powder P is pressurized in the cavity 100a to form a green compact Z1 (FIG. 8) along the shape of the cavity 100a.

  The shoe box 150 in which the raw material powder P is filled in the cavity 100a is formed in a box shape with the lower surface opened, and is reciprocated back and forth (left and right in the figure) with the lower surface in contact with the upper surface of the die 140. The The shoe powder 150 is supplied with raw material powder P from a hopper (not shown), and advances to the position shown in FIG. 5 to be positioned on the cavity 100a, thereby holding the raw material powder P held therein. Is dropped into the cavity 100a and filled.

  The upper punch 110 is fixed to an upper punch holding member 110A that is held movably up and down with respect to the base 100b via the frame 170, and can move up and down integrally with the upper punch holding member 110A. . The upper punch holding member 110A to which the upper punch 110 is fixed is mechanically driven up and down by a mechanism (primary driving device) such as a crank mechanism, a knuckle press, or a cam mechanism to lower the upper punch 110 to the bottom dead center. Thus, the raw material powder P filled in the cavity 100a can be pressurized.

  The lower punch 120 is fixed to the lower punch holding member 120A, and can be moved up and down integrally with the lower punch holding member 120A by a piston 181 of a fluid pressure cylinder (secondary drive device) 180 fixed to the base 100b. It has become. Between the lower punch 120 (lower punch holding member 120A) and the base 100b, a filling amount correction linear scale 161 for detecting the position of the lower punch 120 with respect to the base 100b is attached. The control unit 190 that receives the detection signal from the filling amount correcting linear scale 161 controls the flow rate in the fluid pressure cylinder 180 so that the piston 181, that is, the lower punch 120 can be moved to an arbitrary position. It has become.

The bottom dead center correcting linear scale (measuring means) 160 is attached between the upper punch holding member 110A and the lower punch holding member 120A, and the distance between the upper punch holding member 110A and the lower punch holding member 120A, that is, the upper punch A measurement value obtained by measuring the distance between 110 and the lower punch 120 is output as a signal. A target value is set in advance in the control unit 190 to which this signal is input, and the flow rate in the fluid pressure cylinder 180 can be controlled so that the measured value becomes this target value. The target value is a value at which the thickness of the cavity 100a becomes the molding target thickness between the upper punch 110 and the lower punch 120.
The control unit 190 also receives a shoebox position detection signal output from a shoebox position detection sensor (not shown) and indicating the position of the shoebox 150.

Next, a method for forming the green compact using the powder molding apparatus 100 configured as described above will be described.
First, at the time of pressure molding, the upper punch 110, the lower punch 120, and the die 140 are respectively arranged at initial positions.
[Filling process]
The shoe box 150 is advanced (advance process), opened on the cavity 100a as shown in FIG. At this time, the shoe box 150 advances from the rear (right side in FIG. 5) to the front (left side in FIG. 5) and moves to the position shown in FIG. 5, so that the shoe box 150 is first opened on the rear side of the cavity 100a. Open to the front side. Therefore, the cavity 100a faces the opening of the shoe box 150 for a long time on the rear side, and the raw material powder P is filled more densely toward the rear side.

  Next, as shown in FIG. 6, the lower punch 120 is raised with respect to the die 140 at the initial stage of the retracting process while retracting the shoe box 150 from the cavity 100a (withdrawing process). That is, the shoe box 150 is moved backward to scrape off the excess raw material powder P placed on the die 140 and the core rod 130 by the front wall portion of the shoe box 150. The wall portion is located in front of the cavity 100a. By raising the lower punch 120 after retreating from the side, a part of the raw material powder P filled in the rear side of the cavity 100a is pushed up onto the die 140 and simultaneously scraped off by the shoe box 150, and is caused to enter the cavity 100a. The amount of the raw material powder P to be filled is corrected at the front and rear portions. Thereby, the volume of the raw material powder P is large on the front side of the cavity 100a, and the volume of the raw material powder P is small on the rear side of the cavity 100a.

  Further, as shown in FIG. 7, after the shoe box 150 is completely retracted from the cavity 100a, the raised lower punch 120 is lowered with respect to the die 140 and returned to the initial position. Thus, the raw material powder P on the front side of the cavity 100a pushed up on the die 140 is returned to the inside of the cavity 100a (inside the die 140), and the filling height of the raw material powder P in the cavity 100a is greatly increased on the front side. Smaller on the side.

That is, since the raw material powder P is dropped from the shoe box 150 into the cavity 100a by natural fall, the raw material powder P is filled in a larger amount toward the rear side of the cavity 100a facing the opening of the shoe box 150 for a long time. It will be. Therefore, when the whole is filled at the same height, a larger amount of the raw material powder P is filled toward the rear side of the cavity 100a, and the density of the green compact obtained by pressure-molding the filled raw material powder P is as follows. It becomes non-uniform.
On the other hand, in the present embodiment, the filling height of the raw material powder P is high on the low density front side and low on the high density rear side, thereby eliminating the uneven filling amount due to the advancing and retreating direction of the shoe box 150. The raw material powder P is uniformly filled in the entire cavity 100a.

[Punch drive process]
FIG. 8 shows the process of pressure molding performed by driving the upper and lower punches.
(Primary driving process)
First, as shown in FIG. 8A, with the lower punch 120 fixed, the upper punch 110 is lowered to the bottom dead center (mechanical movement limit position) to compress the raw material powder P in the cavity 100a. In this apparatus, the upper punch 110 is designed to descend to the ideal bottom dead center. However, the punch 110 cannot actually reach the ideal bottom dead center due to bending of the apparatus or the like.

  The ideal bottom dead center of the upper punch 110 is formed so as to form a cavity 100a having a thickness that is, for example, about 1 mm larger than the molding target thickness of the green compact with the lower punch 120 fixed at the initial position. Is set. In other words, even if the apparatus does not bend or stretch and the upper punch 110 is lowered to the ideal bottom dead center, the thickness of the cavity 100a is larger than the molding target thickness, and the pressure is smaller than the molding target thickness. The powder is not molded.

(Secondary drive process)
Next, as shown in FIG. 8B, with the crank that mechanically drives the upper punch 110 stopped and the upper punch 110 fixed at the bottom dead center, the fluid pressure cylinder 180 is driven to move the lower punch 120 to the initial position. The thickness of the cavity 100a is raised until the molding target thickness is reached. The movement of the lower punch 120 at this time is performed by feeding back a measurement value obtained by the bottom dead center correcting linear scale 160.

  That is, the control unit 190 that has received the detection signal from the filling amount correction linear scale 161 controls the flow rate of the fluid pressure cylinder 180 and measures the distance between the punches 110 and 120 with the bottom dead center correction linear scale 160. Then, the control unit 190 drives and controls the fluid pressure cylinder 180 to raise the lower punch 120 until the value reaches the molding target thickness.

  At this time, the upper punch 110 may be slightly pushed up by raising the lower punch 120, but the lower punch 120 is raised by feeding back the measured value of the distance between the two punches 110, 120. The lower punch 120 is driven until the thickness reaches the forming target thickness, and the lowering deficiency of the upper punch 110 is corrected, and the thickness of the green compact can be set as the target value.

8C, the upper punch 110 is raised, the core rod 130 and the die 140 are lowered with respect to the lower punch 120, and the formed green compact Z1 is extracted from the die 140. In addition, the lower punch 120 raised in the secondary driving process is returned to the initial position to prepare for forming the next green compact.
As described above, it is possible to obtain the green compact Z1 molded to a target thickness at a uniform density throughout.

  Next, the green compact Z1 is fired. At this time, since the green compact Z1 is formed with a uniform density throughout the whole, both end faces 20a, 20b of the pump rotors 20, 30 are formed. , 30a and 30b can be suppressed to a minimum such that the flatness thereof is undulated. Thereafter, sizing is performed by a well-known method to correct the undulation of the surface corresponding to the both end faces 20a, 20b, 30a, 30b, and then only the surface corresponding to the one end face 20a, 30a. The pump rotors 20 and 30 are formed by grinding, and then removing the flash generated throughout.

  As described above, according to the pump rotors 20 and 30 according to the present embodiment, since the other end surfaces 20b and 30b are non-ground surfaces, when the internal gear pump 10 is driven, FIG. As shown in FIG. 2, a part B2 of the fluid is held in the minute hole B1 opened in the other end face 20b, 30b, so that a part of the fluid is formed on the surface layer portion of the other end face 20b, 30b. It becomes possible to soak B2. Further, since the other end surfaces 20b and 30b have a ten-point average roughness Rz larger than the one end surfaces 20a and 30a facing the suction port 51 and the discharge port 52, the other end surfaces 20b and 30b. It is possible to hold more fluid than the one end face 20a, 30a. As described above, when the inscribed gear pump 10 is driven, the lubricity between the inner surface 50a of the casing 50 and the other end surface 20b, 30b can be improved between the inner surface 50a of the casing 50 and the one end surface 20a, 30a. Can also be improved.

  Therefore, when the inscribed gear pump 10 is driven and fluid is sucked from the suction port 51 toward the one end face 20a, 30a, the other end face 20b, 30b is moved to the casing by the fluid pressure of the fluid. 50, even when it is strongly pressed against the inner surface 50a, good lubricity is ensured between the other end surface 20b, 30b and the inner surface 50a of the casing 50, and the other end surface 20b, It is possible to suppress the occurrence of seizure in 30b.

  On the other hand, even when the inscribed gear pump 10 is stopped after being driven, a part B2 of the fluid is held in the minute hole B1 opened in the other end face 20b, 30b as described above. In addition, it is possible to soak a part B2 of the fluid into the surface layer portions of the other end surfaces 20b and 30b. Therefore, when the inscribed gear pump 20 is stopped and restarted, a part B2 of the fluid is oozed out of the hole B1, and the inner surface 50a of the casing 50 and the other end surfaces 20b and 30b It becomes possible to act as lubricating oil. Accordingly, even if the other end surfaces 20b and 30b are strongly pressed against the casing inner surface 50a by the fluid pressure at the time of restart, lubricating oil is interposed between the end surfaces 20b and 30b and the inner surface 50a. Therefore, the occurrence of seizure can be reliably suppressed.

  In particular, in the present embodiment, the outer peripheral surface 30d of the outer pump rotor 30 that is in sliding contact with the inner surface 50a of the casing 50 is also a non-ground surface similar to the other end surfaces 20b and 30b. In the same manner as the other end surfaces 20b and 30b, it becomes possible to hold a part B2 of the fluid during the driving and after the driving, and seizure occurs on the outer peripheral surface 30d. It can also be suppressed.

  Further, since the one end face 20a, 30a facing the suction port 51 and the discharge port 52 is a ground surface, the flatness of the one end face 20a, 30a, the tooth width of the pump rotor 20, 30 (rotation axis) Dimensional accuracy in the O1 and O2 directions) and variations in clearance between the one end face 20a, 30a and the inner face 50a of the casing 50 can be ensured to the same extent as the current one. Thus, the other end surfaces 20b and 30b are non-ground surfaces, so that the both end surfaces 20a, 20b, 30a and 30b of the pump rotors 20 and 30 and the inner surface 50a of the casing 50 are driven when the internal gear pump 10 is driven. In the meantime, it is possible to minimize the leakage of the fluid in the cell C and the decrease in volumetric efficiency.

Moreover, since the pump rotors 20 and 30 are made of Fe-Cu-C-based sintered material and have a density of 6.6 g / cm ³ or more and 7.1 g / cm ³ or less, the pump rotor 20 , 30 can be ensured to the minimum necessary strength, and at the time of the sizing, the intersecting ridge portions 20c, 30c of the rotors 20, 30 and the one end face 20a, 30a It is possible to suppress the intersection ridge line portions formed by the tooth surfaces 21a and 31a from being crushed and increasing the amount of chamfering of these intersection ridge line portions 20c and 30c. Thereby, when the inscribed gear pump 10 is driven, the fluid in the cell C leaks between the both end surfaces 20a, 20b, 30a, 30b and the casing inner surface 50a from the intersecting ridge portions 20c, 30c and the like. The cell C partitioned by the intersecting ridge line portions 20c, 30c and the like, the tooth surfaces 21a, 31a, and the casing inner surface 50a can be provided with high liquid tightness.

  By the way, the one end face 20a, 30a subjected to the grinding process has a ten-point average roughness Rz smaller than that of the other end face 20b, 30b, and as shown in FIG. 30a, the hole B1 that was opened before the grinding process is closed is closed and the volume of the space is reduced, so that the function of holding a part B2 of the fluid is It will be lower than the end faces 20b, 30b.

  However, when the inward gear pump 10 is driven, if fluid is sucked from the suction port 51 toward the one end face side 20a, 30a, both the rotors 20, 30 are caused by the fluid pressure at this time. The end surfaces 20b and 30b are pressed against the inner surface 50a of the casing 50, and the end surfaces 20a and 30a are moved by the side clearance in the directions of the rotation axes O1 and O2 so as to be separated from the inner surface 50a of the casing 50. It becomes like this. Therefore, by grinding the one end face 20a, 30a, the function of holding the part B2 of the fluid of the one end face 20a, 30a is lower than that of the other end face 20b, 30b. Even so, it can be said that this hardly affects the seizure resistance of the rotors 20 and 30.

  In particular, in the present embodiment, the other end surfaces 20b and 30b are not ground, and the intersecting ridge portions 20c and 30c are not chamfered during the sizing process, and the rotation axis O1 from the other end surfaces 20b and 30b, In the inscribed gear pump 10, since the rising amount Y in the O2 direction is 0.01 mm or less and the protruding amount Z in the radial direction from the tooth surfaces 21a and 31a is 0.05 mm or less. The intersecting ridge portions 20c and 30c can be brought into contact with the casing inner surface 50a. As a result, the cell C is partitioned on the other end face 20b, 30b side by the intersecting ridge line portions 20c, 30c, the tooth surfaces 21a, 31a, and the casing inner surface 50a. Sometimes, it becomes possible to reliably prevent the fluid in the cell C from leaking between the other end face 20b, 30b and the casing inner face 50a. That is, since the other end surfaces 20b and 30b are non-ground surfaces and the flatness thereof is lowered, the fluid in the cell C leaks from the gap between the other end surfaces 20b and 30b and the casing inner surface 50a. Thus, the volumetric efficiency of the inscribed gear pump 10 can be minimized.

  In addition, when the rising amount Y is set in the range, the intersecting ridge line portions 20c and 30c are slidably contacted with the casing inner surface 50a in the other end surfaces 20b and 30b, thereby the inner surface 50a. Therefore, it is possible to avoid that the wear of the internal gear pump 10 is shortened.

  Further, by setting the protrusion amount Z within the above range, the crossed ridge line portions 20c and 30c abut on each other at the outer teeth 21 and the inner teeth 31 at the time of meshing, but the other portions do not abut. It becomes possible to avoid that. Thereby, each said cell C can be divided reliably in the circumferential direction, and it can avoid that volumetric efficiency falls.

  Furthermore, in this embodiment, since both rotors 20 and 30 are formed based on the green compact Z1 formed by the powder molding apparatus 100 shown in FIGS. 5 to 8, the green compact Z1 is spread over the entire area. It becomes possible to form a uniform density, and when the green compact Z1 is fired, the surfaces corresponding to both end faces 20a, 20b, 30a, 30b of the pump rotors 20, 30 swell, etc. It is possible to minimize the decrease in the flatness. Accordingly, even if the other end surfaces 20b and 30b are not ground, it is possible to minimize the flatness of the other end surfaces 20b and 30b from being reduced, and the other end surfaces 20b and 30b It is possible to prevent the fluid in the cell C from leaking between the casing inner surface 50a and the volumetric efficiency of the inscribed gear pump 10 from being lowered.

Among the effects described above, a verification test was conducted on the seizure resistance of the formed pump rotor.
There are two types of test pieces to be used for this test: Cu having a grinding process after the sizing process and a test piece not having a grinding process after the sizing process, each having a Cu content of 1.5 wt% to 2.5 wt% and a C content of 0. .6 wt% to 0.75 wt%, at least 5 types of Fe—C—Cu based sintered material formed into a disk shape, and each of these types differed in density and surface roughness Rz (total 10 Prepared).

  And each seizure load was measured about these test pieces. Here, the seizure resistance load means that the test piece is arranged on the surface of a plate-like test material (surface roughness 3.2 Rz) made of FC material, and each contact surface of the test piece and the test material. The test piece is rotated around its axis at a peripheral speed of about 3.1 m / s while supplying lubricating oil. In this process, a load was applied stepwise to the test piece in the thickness direction, and the load when seizure occurred on the contact surface of the test piece was measured. Then, the load was divided by the area of the contact surface of the test piece, and this value was used as a seizure resistance load.

The results are shown in FIG. As a result, when the density of the material is 6.6 g / cm ³ or more and 7.1 g / cm ³ or less and the ten-point average roughness Rz is 4 μm or more and 10 μm or less, the seizure load is improved. It was confirmed that it would be possible.

The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.
For example, the number of teeth of the external teeth 21 and the internal teeth 31 is not limited to the above embodiment. Further, although the configuration in which the intersecting ridge line portions 20c and 30c are respectively convex in the curved shape is shown, chamfering may be performed if C (the chamfering amount) is 0.2 mm or less during the sizing process. Furthermore, in the said embodiment, although the outer peripheral surface 30d of the outer side pump rotor 30 showed the structure made into the non-grinding surface similarly to said other end surface 20b, 30b, this outer peripheral surface 30d is the said one end surface 20a, A ground surface similar to 30a may be used.

Further, instead of the powder molding apparatus 100 shown in FIGS. 5 to 8, the following configuration may be adopted.
This will be described with reference to FIG. The CNC press apparatus 201 shown in this figure has a configuration in which a die 205 having a cavity 200a filled with a raw material powder P and an upper punch 208 are driven up and down, and a lower punch 209 is always fixed.

  The die 205 is attached to a lower slider 203 that slides in the lower guide 202 via a lower ram 204, and is moved up and down by driving of a driving means (not shown) such as a ball screw mechanism. A lower punch 209 fixed to the fixing plate 213 is disposed below the die 205 so as to fit into the cavity 200a from below.

  Above the lower punch 209, an upper punch 208 that can be put into and out of the cavity 200a is disposed coaxially facing the lower punch 209. The upper punch 208 is attached to an upper guide 210 that slides in the upper slider 206 through an upper ram 207 including a hydraulic piston 222 and a hydraulic cylinder 201 to which an upper punch plate 223 is attached. The upper slider 206 is connected via a link mechanism 211 to a crankshaft 212 that is rotated by a drive motor M (primary drive device). The drive motor M is a servo motor that is driven and stopped in accordance with a program stored in the computer (control unit) 220.

The upper ram 207 has a hydraulic cylinder 221 fixed to the upper guide 210 and a hydraulic piston 222 attached to the upper punch plate 223. The hydraulic cylinder 221 is provided with a hydraulic pressure supply port 221a, and hydraulic pressure is supplied from a hydraulic unit 226 (secondary drive device) via a hydraulic pressure supply pipe 225 connected thereto. The hydraulic pressure is controlled by a hydraulic servo valve 224 provided in the hydraulic pressure supply pipe 225 and driven by the computer 220.
That is, the entire upper ram 207 is driven up and down by a drive motor (primary drive device) M, and the hydraulic piston 222 is driven up and down by a hydraulic unit (secondary drive device) 226.

  Further, the apparatus 201 measures the distance between the upper punch plate 223 and the fixed plate 213 between the upper punch plate 223 to which the upper punch 208 is fixed and the fixed plate 213 to which the lower punch 209 is fixed. The linear scale (measuring means) 214 is provided. The measured value of the linear scale 214 is transmitted to the computer 220, and the computer 220 calculates the drive signal of the drive motor M and the drive signal of the hydraulic servo valve 224 based on the measured value, and outputs them. Yes.

A method for manufacturing a green compact using the CNC press apparatus 201 configured as described above will be described.
[Punch drive process]
Prior to the pressure molding, the upper punch 208, the lower punch 209, and the die 205 are arranged at initial positions in advance.

(Primary driving process)
With the lower punch 209 and the die 205 fixed, the upper ram 207 is lowered to the bottom dead center (mechanical movement limit position), and the cavity 200a filled with the raw material powder P is closed.

(Secondary drive process)
When the crank angle reaches 180 ° at which the upper ram 207 reaches the bottom dead center, the computer 220 stops the drive motor M that mechanically drives the upper ram 207, and the lowering of the upper punch 208 due to the lowering of the upper ram 207 is stopped. . The hydraulic servo valve 224 is driven simultaneously with the lowering stop of the upper ram 207, and the hydraulic cylinder 221 is hydraulically operated until the measured value from the linear scale 214 reaches a set value (a value at which the thickness of the cavity 200a becomes the molding target thickness). To lower the hydraulic piston 222, that is, the upper punch 208. Further, simultaneously with lowering the upper punch 208 by hydraulic pressure, the die 205 is lowered by half of the lowering stroke of the upper punch 208, whereby the raw material powder P in the cavity 200a is pressed from both the upper and lower sides, and a uniform pressure is applied. Is received and compressed to a uniform density in the vertical direction.

When the measured value of the linear scale 214 becomes the set value, the hydraulic servo valve 224 is controlled by the computer 220, the hydraulic piston 222 is raised, the upper punch 208 is raised, the rotation of the drive motor M is restarted, and the upper ram 207 is restored. At the same time, the upper punch 208 is raised and the die 205 is lowered. Thereby, the green compact molded to the molding target thickness is extracted from the die 205 (cavity 200a) and placed on the lower punch 209.
Even in the manner described above, a green compact molded to a molding target thickness with a uniform density throughout can be obtained.

  A pump rotor with improved seizure resistance while maintaining volumetric efficiency can be provided.

It is a section top view of an internal gear pump which has a pump rotor shown as one embodiment concerning the present invention. FIG. 2 is a cross-sectional view of the inscribed gear pump shown in FIG. FIG. 3 is an enlarged view of part A of the inscribed gear pump shown in FIG. 2. (A) An enlarged cross-sectional view of the outer peripheral surface of the outer pump rotor, the other end surface of the outer pump rotor, or the other end surface of the inner pump rotor shown as one embodiment according to the present invention, (b) the outer pump It is an expanded sectional view of one end surface of a rotor or one end surface of an inner side pump rotor. It is sectional drawing which shows one Embodiment of the principal part of the powder molding apparatus for forming the pump rotor shown in FIG. 1, and demonstrates a filling process. FIG. 6 is a view showing a lower punch raising process in a shoe box retracting process in the powder molding apparatus shown in FIG. 5. It is sectional drawing which shows the principal part of the powder shaping | molding apparatus of the state which lowered the lower punch from the state shown in FIG. 6, and the filling of the raw material powder was completed. FIG. 5 to FIG. 7 show the main part of the powder molding apparatus, wherein (a) a mechanical driving process for lowering the upper punch to the bottom dead center, (b) lower punch until the cavity thickness reaches the molding target thickness. It is sectional drawing which shows the adjustment process to raise, (c) the process of extracting the shape | molded green compact from die | dye. It is a figure which shows the result of having verified the effect of the pump rotor shown as one Embodiment which concerns on this invention. FIG. 3 shows another embodiment of the main part of a powder molding apparatus for forming the pump rotor shown in FIG. 1. FIG.

Explanation of symbols

10 Inscribed gear pump 20 Inner side pump rotor (pump rotor)
20a, 30a One end face 20b, 30b The other end face 20c, 30c Crossing ridge line part 21 External tooth 21a External tooth face 30 Outer side pump rotor (pump rotor)
30d Outer surface of outer pump rotor 31 Internal tooth 31a Internal tooth surface 50 Casing 51 Suction port 52 Discharge port C Cell Y Rise amount Z Projection amount

Claims (3)

An inner pump rotor formed with outer teeth, an outer pump rotor formed with inner teeth meshing with the outer teeth, a casing formed with a suction port for sucking fluid and a discharge port for discharging fluid A pump rotor used in an internal gear pump that conveys fluid by sucking and discharging fluid by volume change of cells formed between tooth surfaces of both rotors when both rotors are engaged and rotated.
It is formed of a Fe-Cu-C-based sintered material and has a density of 6.6 g / cm ³ or more and 7.1 g / cm ³ or less, and the suction port and One end surface facing the discharge port is a ground surface, the other end surface opposite to the one end surface is a non-ground surface, and the one end surface has a ten-point average roughness Rz than the other end surface. A pump rotor characterized in that is made small. The pump rotor according to claim 1,
The intersecting ridge line portion between the other end surface and the tooth surface has a rising amount of 0.01 mm or less from the other end surface in the rotation axis direction and a protrusion amount in the radial direction from the tooth surface. A pump rotor characterized by being 0.05 mm or less. The pump rotor according to claim 1 or 2,
An outer peripheral surface of the outer pump rotor is a non-ground surface, and the ten-point average roughness Rz is larger than that of the one end surface.

Images