JP2019039315A - Internal gear type pump - Google Patents

Abstract

To provide an internal gear type pump that can meet both request for lowering torque and request for increasing pump efficiency.SOLUTION: In an internal gear type pump, a pump rotor including an inner rotor with a tooth number n and an outer rotor with a tooth number n+1 is assembled into a pump case. The internal gear type pump meets a condition of D/L≥5.0, where D represents an outer diameter of the pump rotor and L represents the whole length of the pump rotor.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an internal gear pump having a pump rotor composed of an inner rotor and an outer rotor having a single tooth difference, and more specifically, an internal gear that exhibits high pump efficiency when used in a low rotation range. It relates to a pump.

  An internal gear pump mounted on a vehicle tends to reduce the diameter of a pump rotor for the purpose of reducing driving torque (reducing torque) in order to meet the demand for improvement in fuel consumption that is increasing year by year.

  Since there is a limit to the reduction in torque by modifying the tooth profile, if the purpose of reducing torque cannot be achieved by modifying the tooth profile, the rotor diameter can be reduced even if the overall length of the pump rotor is increased. Yes.

  Here, in Patent Document 1 below, the ratio of the area of the outer teeth formed on the outer peripheral side of the root circle of the inner rotor and the area of the inner teeth formed on the inner peripheral side of the root circle of the outer rotor is appropriately set. An internal gear pump that achieves miniaturization and high performance by setting to is shown.

  However, it is conceivable that the internal gear pump disclosed in Patent Document 1 also increases the total length of the pump rotor in order to further reduce the rotor diameter, depending on the degree of demand for reducing the drive torque.

Japanese Patent No. 3917026 No. 06-039109

  In the internal gear pump, the pump efficiency decreases as the total length of the pump rotor used increases.

The pump efficiency (total efficiency of the pump) is expressed by the product of the volumetric efficiency and the mechanical efficiency of a pumping chamber (hereinafter simply referred to as a chamber) formed between the inner rotor and the outer rotor. here,
Pump efficiency (%) = volumetric efficiency (%) x mechanical efficiency (%) ÷ 100
Volumetric efficiency (%) = actual discharge amount ÷ theoretical discharge amount (V _TH ) × 100
Mechanical efficiency (%) = (theoretical discharge amount × discharge pressure) ÷ (2π × drive torque) × 100

  Of the two factors that determine the pump efficiency, the mechanical efficiency depends on the sliding resistance when the pump rotor rotates. The sliding resistance decreases when the outer diameter of the pump rotor is reduced to reduce the area of the sliding surface, but the theoretical discharge amount of the pump decreases as the outer diameter of the pump rotor decreases.

  Thus, the overall length of the pump rotor is increased to compensate for the decrease in the discharge amount. However, when this method is adopted, the tip clearance forming area is increased by the increase in the overall length of the pump rotor.

  As a result, although the mechanical efficiency is improved by reducing the driving torque by reducing the outer diameter of the pump rotor, the amount of liquid leakage from the tip clearance portion is increased and the volumetric efficiency is greatly reduced, which has the effect of improving the mechanical efficiency. This cancels out and pump efficiency decreases.

  The tip clearance is a gap between teeth at a position that partitions the maximum volume chamber when the inner rotor and the outer rotor are in the theoretical eccentric position.

  Therefore, an object of the present invention is to realize and provide an internal gear type pump that can satisfy both the demand for torque reduction and the demand for improvement of pump efficiency.

  An internal gear pump according to an aspect of the present invention provided as a solution to the above problem is a pump case in which a pump rotor including an inner rotor having n teeth and an outer rotor having n + 1 teeth is incorporated in a pump case. The outer diameter of the pump rotor is D, and the total length of the pump rotor is L. The condition of D / L ≧ 5.0 is satisfied.

  The internal gear pump of the present invention exhibits high pump efficiency in a low rotation range. Further, the torque can be reduced by using in a low rotation range.

It is an exploded perspective view showing one mode of an internal gear type pump of the present invention. FIG. 2 is an end view showing the internal gear pump of FIG. 1 with a pump case lid removed. It is a longitudinal cross-sectional view of the internal gear type pump of FIG.

[Description of Embodiment of the Present Invention]
An internal gear pump according to an aspect of the present invention includes a pump rotor including an inner rotor having n teeth and an outer rotor having n + 1 teeth. The pump rotor has a ratio of its own diameter D to the total length L of D / L ≧ 5.0, and the pump is configured by incorporating the pump rotor into a pump case.

  The pump case is a case having a known structure in which a case main body having a rotor storage chamber and a lid for closing the inlet of the rotor storage chamber are combined.

  The case body has a suction port and a discharge port. The suction port and the discharge port are opened at the end surface of the rotor storage chamber facing the side surface of the pump rotor.

  The volume of the chamber formed between the inner rotor and the outer rotor increases and decreases with the rotation of the pump rotor, and by this increase and decrease, the fluid pumped up by the pump is sucked into the chamber and discharged from the chamber.

  As the tooth profile of the pump rotor, many tooth profiles are known, such as a tooth profile using a trochoid curve, a tooth profile using a cycloid curve, or a tooth profile disclosed in Patent Document 2, and the known tooth profile is arbitrarily selected. It is not limited to a specific tooth profile.

  Whichever tooth profile is adopted, the outer rotor has a tooth profile created by the envelope of the inner rotor tooth profile curve group obtained by rotating the inner rotor to be combined by the method disclosed in Patent Document 2. It is preferable because fluctuations between the tooth gaps during rotation of the rotor can be reduced.

  In the internal gear pump according to one aspect of the present invention, the total length L of the pump rotor is extremely short, for example, 10 mm in the case of a rotor having a diameter D = φ50 mm.

  For this reason, in order to secure the same theoretical discharge amount as that of a conventional internal gear pump in which the overall length of the pump rotor is increased and the outer diameter of the pump rotor is reduced, the outer diameter of the pump rotor must be increased. This reduces the mechanical efficiency of the pump.

  However, since the total length of the pump rotor is short, liquid leakage through the tip clearance portion is reduced (theoretical liquid leakage amount is substantially constant regardless of the rotational speed), and the volumetric efficiency is increased.

  In the low rotation range of 3000 rpm or less, the volume efficiency improvement range is larger than the mechanical efficiency reduction range due to the shortening of the overall length of the pump rotor, thereby improving the pump efficiency.

  In addition, the pump drive torque increases in proportion to the increase in the number of rotations. However, the pump of the present invention exhibits high pump efficiency in a low rotation range of 3000 rpm or less, so the rotation number during use is set to 3000 rpm or less. It is also possible to reduce the drive torque (lower torque) by reducing the torque.

  By reducing the rotational speed during use to 3000 rpm or less, the effect of reducing sound and vibration (NV characteristics) is also enhanced.

  The present invention can be expected to be effective in improving efficiency and improving NV characteristics regardless of the type of drive source as long as the pump is driven at a rotational speed of 3000 rpm or less. Particularly suitable for use in oil pumps.

  The electric motor that is the drive source of the electric oil pump can control the rotation speed, and can reduce the rotation speed to 3000 rpm or less.

  Therefore, when the present invention is applied to an electric oil pump, it can contribute to the miniaturization of the motor and the cost reduction of the motor by reducing the number of magnets used.

  In vehicles having an idling stop function, an electric oil pump that is operated while the engine is stopped is employed for the purpose of securing the hydraulic pressure for clutch engagement of the automatic transmission (AT / CVT) immediately after the engine is started. .

  The electric oil pump for that purpose is required to have low power consumption because it is driven by the electric power stored in the vehicle battery. Therefore, for the electric oil pump for that purpose, it is preferable that the outer diameter of the pump rotor is 50 mm or less in order to reduce power consumption.

  Since the sliding resistance decreases as the area of the sliding surface decreases, the driving torque may be small and the power consumption for driving may be reduced.

[Details of the embodiment of the present invention]
Specific examples of the internal gear pump according to one embodiment of the present invention will be described below with reference to the drawings. In addition, this invention is not limited to these illustrations, is shown by the claim, and it is intended that all the changes within the meaning and range equivalent to a claim are included.

  The internal gear pump 1 illustrated in FIGS. 1 to 3 is an electric pump that is operated by direct current power supplied from a car battery.

  The internal gear pump 1 includes a pump rotor 2, a pump case 3 that houses the pump rotor, and an electric motor 4 that rotationally drives the pump rotor 2 via a shaft 10.

  As the pump rotor 2, a combination of an inner rotor 2i having n teeth (n is an integer of 2 or more) and an outer rotor 2o having n + 1 teeth is used.

  The illustrated pump rotor is a paracoid rotor (trademark of Sumitomo Electric), the inner rotor 2i has a tooth profile using a trochoid curve, and the outer rotor is described in Patent Document 2 as an inner rotor. The tooth profile is created by the envelope of the inner rotor tooth profile curve group obtained by rotating by the above method.

  The pump case 3 is a case in which a case main body 5 and a lid 6 are combined. The case main body 5 includes a rotor storage chamber 5a, and a suction port 5b and a discharge port, each of which opens at an end surface of the rotor storage chamber 5a. 5c. The lid 6 closes the entrance of the rotor storage chamber 5a.

  The pump rotor 2 is incorporated in the rotor storage chamber 5 a of the pump case 3. The pump rotor 2 employed in the internal gear pump 1 has a ratio D / L of the rotor outer diameter D (see FIG. 2) and the rotor full length L (see FIG. 3) of 5.0 or more.

  An example of a specific combination of the rotor outer diameter D and the rotor total length L of the pump rotor that satisfies the condition that D / L is 5.0 or more is shown below.

・ 20mm ≦ D <25mm, L = 4mm or less D / L ≧ 5.0
・ 25mm ≦ D <30mm, L = 5mm or less D / L ≧ 5.0
・ 30mm ≦ D <35mm, L = 6mm or less D / L ≧ 5.0
・ 35mm ≦ D <40mm, L = 7mm or less D / L ≧ 5.0
・ 40mm ≦ D <45mm, L = 8mm or less D / L ≧ 5.0
・ 45mm ≦ D <50mm, L = 9mm or less D / L ≧ 5.0

  The internal gear pump 1 configured as described above exhibits high pump efficiency in a low rotation range of 3000 rpm or less.

  Further, by reducing the rotational speed to 3000 rpm or less, it becomes possible to reduce the drive torque and improve the NV characteristics.

Example 1
Rotor outer diameter D = φ40 mm, rotor total length L = 4.5 mm, D / L = 8.9 pump rotor (paracoid rotor: Sumitomo Electric Trademark), rotor outer diameter D = φ24.8 mm, rotor total length L = 14 mm, A performance simulation of an oil pump having a pump rotor with D / L = 1.8 (paracoid rotor: Sumitomo Electric Trademark) was performed.

The theoretical discharge amount (V _TH ) of these pumps is as follows. The theoretical discharge amount is the same for both pumps.
At 500 rpm: 0.63 cm ³ / rev
At a rotation speed of 800 rpm: 1.00 cm ³ / rev
At a rotation speed of 1000 rpm: 1.25 cm ³ / rev
At a rotation speed of 1500 rpm: 1.88 cm ³ / rev
At a rotation speed of 2000 rpm: 2.50 cm ³ / rev
At 3000 rpm: 3.75 cm ³ / rev

  Table 1 shows the pump efficiency when the oil temperature is 80 ° C. and the discharge pressure is 1.0 MPa.

-Example 2-
The performance simulation of the two types of oil pumps used in Example 1 was performed by changing the oil temperature and the discharge pressure. Table 2 shows the pump efficiency in the performance simulation.

  From the first and second embodiments, the internal gear type pump in which the ratio D / L of the outer diameter to the total length of the pump rotor is set to 5.0 or more is an internal gear type pump having a D / L of 5.0 or less. It can be seen that high pump efficiency can be obtained when used in the region of 3000 rpm or less compared to the pump.

DESCRIPTION OF SYMBOLS 1 Internal gear type pump 2 Pump rotor 2i Inner rotor 2o Outer rotor 3 Pump case 4 Motor 5 Case main body 5a Rotor storage chamber 5b Intake port 5c Discharge port 6 Lid

Claims (3)

  An internal gear type pump in which a pump rotor comprising an inner rotor having n teeth and an outer rotor having n + 1 teeth is incorporated in a pump case, the outer diameter of the pump rotor being D and the total length of the pump rotor being L As an internal gear pump that satisfies the condition of D / L ≧ 5.0.   The internal gear pump according to claim 1, which is configured as an electric oil pump using an electric motor as a drive source.   The internal gear type pump according to claim 1 or 2, wherein an outer diameter D of the pump rotor is 50 mm or less.

Images