JP2005076582A - Inscribed type gear pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inscribed type gear pump capable of preventing corrosion of the inner circumferential surface of an inner rotor and the outer circumferential surface of an outer rotor, reducing slide resistance of the inner rotor to the outer rotor, and slide resistance of each rotor to a housing so as to hold down power consumption of a motor to drive a pump. <P>SOLUTION: In this inscribed type gear pump, fluid is sucked and discharged based on volume change of a pump chamber P in accordance with rotation of the inner rotor 10 having n-pieces (n≥2) of external teeth 11 and the outer rotor 20 having (n+1)-pieces of internal teeth 21 to be engaged with the external teeth 11. Fluororesin coated layers 12 and 22 are formed on the surfaces of the inner rotor 10 and the outer rotor 20. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  This invention sucks and discharges fluid by changing the volume of the pump chamber accompanying rotation of an inner rotor having n (n ≧ 2) external teeth and an outer rotor having n + 1 internal teeth meshing with the external teeth. The present invention relates to an internal gear pump.

  As an internal gear pump, a trochoid pump using a trochoidal tooth profile for an inner rotor and an outer rotor is widely known. This trochoid pump rotates the inner rotor with a motor to rotate the outer rotor meshing with the inner rotor in the same direction as the inner rotor, and the volume of the pump chamber formed between the contact portions of the rotors by this rotation. The fuel is sucked from the suction port and discharged from the discharge port, and has the advantage that the structure is relatively simple and the pump efficiency is high.

  Even in automobiles and the like, this internal gear pump is employed in a mechanism for supplying gasoline to an engine. Conventionally, the inner rotor and outer rotor constituting the internal gear pump for fuel supply are manufactured from an iron-based sintered alloy, and the surface thereof has not been particularly processed. The internal gear pump has several problems.

  First, as a first problem, gasoline may contain a slight amount of alcohol or moisture. If these cause rust on the surfaces of the inner rotor and outer rotor, between each rotor and each rotor, The sliding resistance acting between the housing and the pump increases, and the driving torque of the pump increases. As a result, the power consumption of the motor driving the pump increases. Furthermore, the on-board power supply of a car is usually a 12 volt battery, but the voltage decreases when the temperature is low, such as in winter, and the rotational force of the motor becomes weak. Therefore, the motor having a weak rotational force cannot rotate the pump having a large driving torque, and as a result, fuel is not supplied, so the engine may not start.

  As a second problem, the contact between the inner rotor and the outer rotor and the contact portion between the rotor and the housing are always sliding due to the mechanism of the inscribed gear pump, but the sliding resistance is increased. If the pump is rotated continuously for a long time, the rotor and the housing may be heated to cause seizure.

  As a third problem, the iron-based sintered alloy usually has a Vickers hardness of about 70 Hv to 130 Hv, but the contact portion between the inner rotor and the outer rotor, and the contact portion between each rotor and the housing after long-term use. The pump chamber is worn and the liquid tightness of the pump chamber cannot be maintained, and the gasoline flows into the adjacent relatively low-pressure pump chamber through the worn portion from the pump chamber where high pressure gas should be discharged, resulting in a decrease in pump efficiency. Resulting in.

As a means for solving these problems, there is one that reduces sliding resistance by forming an electroless nickel plating film layer on the inner peripheral surface of the inner rotor of the inscribed gear pump and the outer peripheral surface of the outer rotor (for example, patents) Reference 1).
JP-A-8-144964 (2nd page, FIG. 1)

  However, some foreign gasolines contain sulfur and its compounds, and some organic acids such as formic acid and acetic acid. There was a problem that the bonding gold was corroded and the sliding resistance was increased.

  The present invention has been made in view of the above circumstances, and prevents the inner peripheral surface of the inner rotor and the outer peripheral surface of the outer rotor from corroding, as well as sliding resistance between the inner rotor and the outer rotor, and each rotor. An object of the present invention is to provide an internal gear pump capable of reducing power consumption of a motor that drives the pump by reducing sliding resistance with a housing.

  In order to achieve the above object, an internal gear pump according to claim 1 of the present invention has an inner rotor having n (n ≧ 2) external teeth and n + 1 internal teeth that mesh with the external teeth. In an internal gear pump that sucks and discharges fluid by a change in volume of a pump chamber accompanying rotation with an outer rotor, a fluororesin coating layer is formed on the surfaces of the inner rotor and outer rotor It is.

  The internal gear pump according to claim 2 of the present invention is a pump accompanying rotation of an inner rotor having n (n ≧ 2) external teeth and an outer rotor having n + 1 internal teeth meshing with the external teeth. In the internal gear pump that sucks and discharges fluid by changing the volume of the chamber, a fluororesin coating layer is formed on the surface of one of the inner rotor and the outer rotor.

  The inscribed gear pump according to claim 3 of the present invention is characterized in that the fluororesin coating layer has a thickness of 1 to 30 μm.

  The inscribed gear pump according to claim 4 of the present invention is characterized in that the fluororesin coating layer is made of polytetrafluoroethylene, polytetrafluoroethylene-perfluoroalkyl vinyl ether copolymer or polytetrafluoroethylene-hexafluoropropylene copolymer. It is characterized by being composed of any one of coalescing.

  1) The internal gear pump according to claim 1 of the present invention is capable of rotating between an inner rotor having n (n ≧ 2) external teeth and an outer rotor having n + 1 internal teeth meshing with the external teeth. In the internal gear pump that sucks and discharges the fluid by the volume change of the accompanying pump chamber, a fluororesin coating layer is formed on the surfaces of the inner rotor and the outer rotor. It is difficult to corrode sulfur and its compounds contained in poor gasoline, and organic acids such as formic acid and acetic acid, and a durable internal gear pump can be formed. Further, the surfaces of the fluororesin coating layers 12 and 22 have a small coefficient of friction and can reduce the sliding resistance.

  2) The internal gear pump according to claim 2 of the present invention is capable of rotating between an inner rotor having n (n ≧ 2) external teeth and an outer rotor having n + 1 internal teeth meshing with the external teeth. In an internal gear pump that sucks and discharges fluid by a change in volume of the pump chamber, a fluororesin coating layer is formed on one of the surfaces of the inner rotor and the outer rotor. As a result, the surface of the fluororesin coating layers 12 and 22 has a small coefficient of friction and can reduce sliding resistance.

  3) The inscribed gear pump according to claim 3 of the present invention is characterized in that the fluororesin coating layer has a thickness of 1 to 30 μm. Even when the coating layer is formed on the surface, it is possible to prevent the surface of the sintered alloy from being deficient and to smooth the surface of the coating layer. In addition, the processing accuracy can be kept high while reducing the amount of fluororesin used and suppressing the cost.

  4) The inscribed gear pump according to claim 4 of the present invention is characterized in that the fluororesin coating layer is made of polytetrafluoroethylene, polytetrafluoroethylene-perfluoroalkyl vinyl ether copolymer or polytetrafluoroethylene-hexafluoropropylene. It is characterized in that it is composed of any one of the copolymers, and is extremely durable against chemicals, stable at high temperatures, and has a low surface friction coefficient. It is possible to form an internal gear pump that is hardly corroded with respect to sulfur, its compounds, and organic acids such as formic acid and acetic acid, is durable, and has low sliding resistance.

  Embodiments of the present invention will be described below in detail with reference to the drawings.

  The internal gear pump of the present invention is for supplying fuel to an automobile engine or the like. As shown in FIG. 1, reference numeral 10 denotes an inner rotor, reference numeral 20 denotes an outer rotor, reference numeral H denotes a housing, reference numeral A denotes a suction port, and reference numeral B denotes a discharge port.

  The inner rotor 10 has n (n ≧ 2) (in this embodiment, 10) external teeth 11 formed by a trochoid curve, and the outer rotor 20 has n + 1 sheets (this embodiment) formed by a trochoid curve. The example has eleven internal teeth 21.

The inner rotor 10 and the outer rotor 20 are both sintered alloys obtained by compression molding metal powder and then sintered, for example, iron-based sintered alloys having a density of 6.6 to 7.2 g / cm ^3. It is manufactured by.

  As shown in FIG. 2, fluororesin coating layers, for example, PTFE (polytetrafluoroethylene resin) coating layers 12 and 22 are formed on the surfaces of the inner rotor 10 and the outer rotor 20. In this case, the PTFE coating layers (fluororesin coating layers) 12 and 22 may be formed on the inner rotor 10 and the outer rotor 20 in any manner. For example, PTFE spray coating or molten PTFE is used. For example, the inner rotor 10 and the outer rotor 20 may be dipped in the inner part.

  In this way, since the surface of the inner rotor 10 and the outer rotor 20 is coated with PTFE, which is extremely durable against chemicals and is highly durable against chemicals, the surface of the inner rotor 10 and the outer rotor 20, sulfur and its compounds contained in poor gasoline, A durable internal gear pump that is resistant to corrosion by organic acids such as formic acid and acetic acid can be formed. Further, the surfaces of the PTFE coating layers 12 and 22 have a small coefficient of friction and can reduce sliding resistance.

  Here, if the thickness of the PTFE coating layers 12 and 22 is less than 1 μm, defects are likely to occur on the surface, and it is difficult to form the surface smoothly. In particular, 10 μm or more is required to fill the bore on the surface of the sintered alloy and form a smooth plating surface. On the other hand, if the thickness exceeds 30 μm, the surfaces of the PTFE coating layers 12 and 22 are formed smoothly, but the processing accuracy becomes low and it becomes difficult to keep the thickness of the PTFE coating layers 12 and 22 constant. This increases the cost of surface treatment. Therefore, it is preferable to form the film layers 12 and 22 to have a thickness of 1 to 30 μm. Further, the PTFE coating layer 23 on the outer peripheral surface side of the outer rotor 20 is in close contact with the housing H and slides at a speed faster than other portions of the rotor. It is preferable to form a thick 10-30 μm.

The inner rotor 10, as shown in FIG. 1, is rotatably supported in the housing H about the axis O _1, outer rotor 20 has its axial center O ₀ only e against the inner rotor 10 eccentrically The housing H is rotatably supported by the housing H while being engaged with the inner rotor 10. At this time, the tip clearance L between the inner rotor 10 and the outer rotor 20 is set to 0.020 mm to 0.080 mm. The housing H is also made of a sintered alloy, for example, an iron-based sintered alloy, like each rotor, and a PTFE (polytetrafluoroethylene resin) coating layer, for example, is formed on a sliding portion with each rotor. .

  Here, the reason why the chip clearance L is set to 0.020 to 0.080 mm is that the sliding resistance increases even if the PTFE coating layers 12 and 22 are formed at 0.020 mm or less. This is because the sliding resistance becomes smaller at 080 mm or more, but the liquid tightness of the pump chamber, and hence the pump efficiency, becomes lower.

  When the inner rotor 10 is rotated in the direction of the arrow X in the figure, the outer rotor 20 is also rotated in the direction of the arrow X along with the rotation. The volume of the pump chamber P formed at each contact portion between the outer teeth 11 of the inner rotor 10 and the inner teeth 21 of the outer rotor 20 gradually increases with rotation and rotates at the left portion of the drawing. It gradually decreases with this.

  On the side wall of the housing H in contact with the pump chamber P, there is a suction port A that opens in an arc along the pump chamber P on the side where the volume gradually increases (right side portion in FIG. 1), and the side on which the volume gradually decreases ( A discharge port B opened in an arc shape is formed along the pump chamber P in the left part of FIG.

  By being formed in this way, when the inner rotor 10 and the outer rotor 20 rotate in the direction of the arrow X, the pump chamber P whose volume gradually increases is sucked fuel from the suction port A, and the pump chamber whose volume gradually decreases. Fuel is discharged from P to discharge port B.

According to the inscribed gear pump of the present embodiment configured as described above, the inner rotor 10 and the outer rotor 20 are made of an iron-based sintered alloy having a density of 6.6 to 7.2 g / cm ³ . The surface becomes smooth with little unevenness, and the processing accuracy increases. Further, by forming PTFE coating layers 12 and 22 having a thickness of 1 to 30 μm on their surfaces, the generation of rust is prevented, and the surfaces of the inner rotor 10 and the outer rotor 20 are made of an iron-based sintered alloy base. Since the friction coefficient is smaller and smoother, the tip clearance L is set shorter than before while reducing the sliding resistance between the inner rotor 10 and the outer rotor 20 and the sliding resistance between each rotor and the housing H. can do. Accordingly, the pump driving torque is reduced, so that the power consumption of the motor driving the pump can be reduced, and the pump is driven even when the voltage of the battery that supplies power to the motor decreases and the rotational force weakens. be able to. Further, since the sliding resistance is small, even if the pump is continuously rotated for a long time, each rotor does not overheat, and seizure hardly occurs. In particular, the PTFE coating layer 12 of the inner rotor 10 and the PTFE coating layer 22 of the outer rotor 20 are formed to a thickness of 1 to 30 μm, whereas the PTFE coating layer 23 on the outer peripheral surface of the outer rotor 20 is formed to a thickness of 10 to 30 μm. In this case, it is possible to prevent the sliding resistance from increasing due to wear on the outer peripheral surface of the outer rotor 20 that is in close contact with the housing H and slides at a speed that is no longer than other portions of the rotor. .

  In the present embodiment, the fluororesin coating is formed on the surfaces of both the inner rotor and the outer rotor. However, when poor gasoline is not used for the inscribed gear pump, the inner rotor and the outer rotor. A fluororesin film may be formed on at least one of the above. Even if formed in this way, the sliding resistance can be reduced by the fluororesin coating having a small surface friction coefficient.

  Moreover, although the said embodiment demonstrated the case where polytetrafluoroethylene (PTFE) was used for the fluororesin film, for example, polytetrafluoroethylene-perfluoroalkyl vinyl ether copolymer other than polytetrafluoroethylene resin (PTFE) was used. It is of course possible to use a polymer (PFE) or a polytetrafluoroethylene-hexafluoropropylene copolymer (FEP).

  In the above embodiment, the case where the inner rotor and the outer rotor are iron-based sintered alloys has been described. Of course, it is possible to use an alloy other than the iron-based sintered alloy, such as a copper-based sintered alloy. is there.

It is a front view which shows the internal gear pump of this invention. It is a principal part enlarged view of the internal gear pump of this invention.

Explanation of symbols

10 Inner rotor
11 external teeth
12 PTFE coating layer (fluorine resin coating layer)
20 Outer rotor
21 internal teeth
22 PTFE coating layer (fluorine resin coating layer)
P Pump room

Claims (4)

An internal type in which fluid is sucked and discharged by a change in volume of a pump chamber accompanying rotation of an inner rotor having n (n ≧ 2) external teeth and an outer rotor having n + 1 internal teeth meshing with the external teeth 2. A gear pump according to claim 1, wherein a fluororesin coating layer is formed on the surfaces of the inner rotor and the outer rotor. An internal type in which fluid is sucked and discharged by a change in volume of a pump chamber accompanying rotation of an inner rotor having n (n ≧ 2) external teeth and an outer rotor having n + 1 internal teeth meshing with the external teeth 2. A gear pump according to claim 1, wherein a coating layer made of a fluororesin is formed on a surface of one of the inner rotor and the outer rotor. The inscribed gear pump according to claim 1 or 2, wherein the fluororesin coating layer has a thickness of 1 to 30 µm. 2. The fluororesin coating layer is made of either polytetrafluoroethylene, polytetrafluoroethylene-perfluoroalkyl vinyl ether copolymer or polytetrafluoroethylene-hexafluoropropylene copolymer. 4. The internal gear pump according to any one of items 3 to 3.

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