JP2004183650A - Inscribed oil pump rotor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize an inscribed oil pump capable of suppressing noise by decreasing pulsation even under high speed revolution by providing an inscribed oil pump rotor capable of suppressing the pulsation while keeping a designated theoretical discharging rate is provided irrespective of its thickness (tooth width) is optional. <P>SOLUTION: The rotor used for the inscribed oil pump conveying a liquid by sucking/discharging the liquid when an outer rotor having internal teeth and an inner rotor having external teeth are rotated in the state of being meshed with each other is designed such that 0.0200≤γmax ≤0.0250[mm/° degree/mm] V, wherein the maximum γmax of the flow rate change of the fluid flowing in and out the cell per unit tooth γ calculated by formula γ=dV/dθ/S/l; V represents the volume of a cell C at rotation angle location θ of the inner rotor 20; S represents an area obtained by projecting the cell C in axial direction; and l represents tooth width in both rotors axial direction and relation. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inscribed oil pump rotor that sucks and discharges fluid by a change in the volume of a cell formed between the tooth surfaces of both rotors when the inner rotor and the outer rotor rotate while meshing with each other.

  Conventionally, an inscribed oil pump has an inner rotor having Z external teeth, an outer rotor having Z + 1 internal teeth meshing with the external teeth, a suction port through which fluid is sucked, and a fluid being discharged. The outer rotor is rotated by rotating the inner rotor to rotate the outer rotor, and the fluid is sucked by a change in the volume of a plurality of cells formed between the two rotors.・ It is designed to discharge.

  On the front side and the rear side in the rotation direction, the cells are individually partitioned by contacting the outer teeth of the inner rotor and the inner teeth of the outer rotor, respectively, and are partitioned by casings on both sides in the rotation axis direction. An independent fluid transfer chamber that rotates and moves with the rotation of the inner rotor is configured. After each cell has a minimum volume during the process of engagement between the external teeth and the internal teeth, the cells increase in volume while moving along the suction port and suck fluid from the suction port. Then, the cell having the maximum volume decreases the volume while moving along the discharge port, and discharges the fluid from the discharge port.

In such an inscribed oil pump, in many cases, it is an issue how to suppress a decrease in pump efficiency and generation of noise due to pulsation and cavitation. To solve this problem, the present inventor has calculated a value (dV / dθ) obtained by dividing the change in the cell volume V according to the rotation angle θ of the inner rotor by the projected area (cell opening area) S in the direction of the rotation axis of the cell. / S) assuming that the maximum value of the change in the flow velocity is small, which is advantageous for suppressing the pulsation, and proposes a tooth profile capable of reducing the maximum value of the change in the flow velocity (/ S). For example, see Patent Document 1).
Japanese Patent No. 3132632 (pages 1-2, FIG. 1)

  In view of the above-mentioned knowledge of the change in the flow velocity by the present inventor, if the rotors have the same shape, the change in the flow velocity can be reduced by reducing the tooth width (the size in the rotation axis direction) of both rotors. Therefore, in order to suppress the pulsation by reducing the change in the flow velocity without reducing the theoretical discharge amount, a large-diameter thin rotor may be used. However, in recent years, there has been a strong demand for further downsizing of the internal oil pump, and a large-diameter and thin rotor cannot meet the demand for downsizing of the pump.

  On the other hand, in order to increase the discharge amount while keeping the diameter small, the rotor may be thickened to increase the cell volume. However, simply increasing the thickness of the rotor increases the volume with respect to the opening area of the cell, so that the flow velocity of the fluid entering and exiting the cell increases, and cavitation tends to occur. Therefore, conventionally, it has been difficult to realize an inscribed oil pump that is small, has a sufficient discharge amount, and suppresses pulsation.

  Further, even in the case of an inscribed oil pump having a large change in flow velocity, pulsation can be suppressed by reducing the rotation speed. However, in recent years, it has been required to ensure a sufficient discharge amount even with a small pump by rotating at high speed, and it is not desirable to reduce the rotation speed to suppress pulsation.

  The present invention has been made in view of such circumstances, and it is possible to suppress the pulsation while securing a predetermined theoretical discharge amount regardless of the thickness (tooth width) regardless of the thickness. It is an object of the present invention to provide an internal-type oil pump that provides a small-sized oil pump rotor and can suppress noise even when rotated at high speed.

In order to solve the above-mentioned problems, an inscribed oil pump rotor according to claim 1 of the present invention includes an inner rotor having Z external teeth and an outer rotor having Z + 1 internal teeth meshing with the external teeth. And a casing having a suction port through which fluid is sucked and a discharge port through which fluid is discharged, and housing the inner rotor and the outer rotor, and when both rotors mesh with each other and rotate, between both rotor tooth surfaces and the casing. A rotor used in an internal oil pump that conveys a fluid by sucking and discharging a fluid by a change in the volume of the formed cell, wherein the cell volume V at the rotation angle position θ of the inner rotor is defined by an axial direction. And the tooth width l in the axial direction of both rotors,
γ = dV / dθ / S / l
The maximum value γmax of the flow velocity change γ per unit tooth width of the fluid entering and exiting the cell, calculated by
0.0200 ≦ γmax ≦ 0.0250 [mm / ° degree / mm]
It is characterized by being.

  According to the present invention, the pulsation can be suppressed and the generation of noise can be prevented by setting the maximum value γmax of the flow velocity change γ per unit tooth width to 0.0250 or less. Further, by setting the maximum value γmax of the flow velocity change γ per unit tooth width to 0.0200 or more, a practical discharge amount and discharge efficiency can be obtained. That is, according to the present invention, it is possible to realize an oil pump rotor which has a sufficient discharge amount, has a small pulsation even when driven at a high rotation speed, and can prevent generation of noise.

  ADVANTAGE OF THE INVENTION According to the internal-type oil pump rotor which concerns on this invention, the rotor which has a sufficient discharge amount, and can reduce a pulsation even if it is driven at high rotation and can prevent noise generation is realized, and an efficient and noise-free It is possible to obtain a small inscribed oil pump.

A first embodiment of an inscribed oil pump rotor according to the present invention will be described with reference to FIGS.
In the present embodiment, the outer rotor 10 having a thickness (tooth width) 1 having 10 internal teeth and the inner rotor 20 having a thickness (tooth width) 1 having 9 outer teeth have respective rotation centers. O1 and O2 are arranged eccentrically.

  The outer rotor 10 is rotatably held in the casing 30 around a rotation center O1. The inner rotor 20 incorporated inside the outer rotor 10 is disposed around a rotation center O2 that does not coincide with the rotation center O1 of the outer rotor 10, and the rotation of the drive shaft 40 fixed to that center causes the arrow shown in the figure to turn. Rotated in the direction.

  The rotors 10 and 20 are rotated by the rotation of the drive shaft 40 while meshing with each other due to their respective tooth surface shapes. A cell C, which is a fluid transfer chamber, is formed between the meshing points of the rotors 10 and 20 meshing with each other. A suction port 31 and a discharge port 32 opening to the cell C are formed in the casing 30, and fluid exchange with each cell C is performed from the suction port 31 and the discharge port 32.

The opening area (projected area in the axial direction) S, that is, the cell volume V of the cell C changes while rotating and moving with the rotation of the outer rotor 10 and the inner rotor 20. Then, fluid is sucked from the suction port 31 in the process of expanding the cell volume V, and is discharged from the discharge port 32 in the process of reducing the cell volume V. In other words, the volume V of the cell C is changed from the minimum indicated by the symbol A to the maximum indicated by the symbol B in FIG.
The volume V of the cell C is obtained by the product of the opening area S and the tooth width 1 of the rotors 10 and 20.

  Since the volume of the cell C changes due to the change in the rotation angle position θ of the inner rotor 20, when the volume of the cell C is differentiated by the rotation angle position θ of the inner rotor 20, the fluid flowing into and out of the cell C by the rotation of the inner rotor 20 is changed. Is obtained. The flow velocity of the fluid flowing into and out of the cell C due to the change in the volume of the cell C can be obtained by dividing the flow rate by the opening area S of the cell C. FIG. 2 shows a value obtained by dividing the change in the flow velocity by the tooth width 1 of the rotors 10 and 20, that is, the relationship between the flow velocity change γ per unit tooth width and the rotation angle position θ of the inner rotor 20.

Note that the flow velocity change γ per unit tooth width is
γ = dV / dθ / S / l [mm / ° degree / mm]
Is calculated. In FIG. 2, the rotation angle position of the inner rotor 20 at which the cell volume V indicated by the reference symbol B in FIG. 1 is maximized is set to θ = 0 °, the change in the flow velocity of the suction fluid in the expansion process of the cell C is positive, and the discharge in the reduction process is positive. Fluid flow rate changes are shown as negative values.

  As shown in FIG. 2, the flow velocity of the fluid sucked / discharged in the internal oil pump reaches its maximum value before and after the cell C goes from the suction process to the discharge process. In the present embodiment, the maximum value γmax of the flow velocity change γ per unit tooth width is smaller than that in the related art, and is set to 0.0214 [mm / ° degree / mm].

Here, the relationship between the maximum value γmax of the flow velocity change γ per unit tooth width and the pulsation characteristics and noise characteristics is shown in FIG.
As shown in FIG. 3, when the maximum value γmax of the flow velocity change γ exceeds 0.0250 [mm / ° degree / mm], the pulsation characteristics sharply increase, and the noise characteristics also increase. On the other hand, if the maximum value γmax is less than 0.0200 [mm / ° degree / mm], the suction / discharge amount is extremely reduced, which makes the pump impractical.
In the present embodiment, the maximum value γmax of the flow velocity change γ is set to 0.0214 [mm / ° degree / mm] which satisfies 0.0200 ≦ γmax ≦ 0.0250 [mm / ° degree / mm]. Pulsation and noise are suppressed, and a practical discharge amount is obtained.

  In addition, this oil pump rotor averages the flow rate change γ per unit tooth width and has a small maximum value γmax. Therefore, when driven at a higher speed than the conventional one, the oil pump rotor is compared with a case where the conventional rotor is similarly rotated at a high speed. Thus, the flow velocity can be kept low. Therefore, even when driven at a high speed, pulsation and cavitation are suppressed to be small. As a result, the pump can be used in a high speed range, and a large discharge amount can be obtained even with a pump having the same capacity.

Next, a second embodiment of the inscribed oil pump rotor according to the present invention will be described with reference to FIGS. 3 and 4. The same parts as those in the first embodiment are denoted by the same reference numerals. This description is omitted.
In this embodiment, as shown in FIG. 4, an outer rotor 50 having eleven internal teeth 50a and having a thickness (tooth width) 1 and an inner rotor having ten external teeth 60a and having a thickness (tooth width) 1 are provided. In the same manner as in the first embodiment, the rotor 60 and the rotor 60 are arranged so that their rotation centers O1 and O2 are eccentric. The outer teeth 60a of the inner rotor 60 have a trochoid tooth profile formed based on a trochoid curve, and the inner teeth 50a of the outer rotor 50 have an arc shape forming a part of a single circle.

Here, the specification values of the inner rotor 60 and the outer rotor 50 shown in FIG. 4 satisfy the following relational expressions.
d2 + 2e + t1 = D1 (1)
d1 + 2e + t2 = D2 (2)
R ± t3 = RO (3)
(Where d1 is the tip circle diameter of the inner rotor 60, d2 is the root circle diameter of the inner rotor 60, D1 is the tip circle diameter of the outer rotor 50, and D2 is the root circle diameter of the outer rotor 50. E is the amount of eccentricity between the inner rotor 60 and the outer rotor 50; t1, t2, and t3 are the clearances (usually in the range of 0 to 1 mm) between the inner rotor 60 and the outer rotor 50; (The radius of a creation circle (not shown) of the outer teeth 60a is shown, and RO shows the radius of the inner teeth 50a of the outer rotor 50.)

Next, specific numerical values will be described.
The root diameter d1 of the inner rotor 60 is 18.100 mm, the root diameter d2 of the inner rotor 60 is 15.084 mm, the root diameter D1 of the outer rotor 50 is 16.632 mm, and the root diameter of the outer rotor 50 is 16.632 mm. D2 is 20.000 mm, the eccentricity e between the inner rotor 60 and the outer rotor 50 is 0.754 mm, the radius RO of the inner teeth 50a of the outer rotor 50, and the radius R of the generated circle of the outer teeth 60a of the inner rotor 60 is 1. 00 mm, and the outer diameter D3 of the outer rotor 50 is 25,000 mm.
When the number of the external teeth 60a of the inner rotor 60 is Z, in the present embodiment, R · Z / (π · (d1 + d2) / 2) is 0.19. Is set outside the range (0.2 or more and 0.3 or less) disclosed in Patent Document 1. However, in the present embodiment, the maximum value γmax of the flow velocity change γ per unit tooth width is set to 0.0236 [mm / ° degree / mm by setting the dimensions of the respective parts of the inner rotor 60 and the outer rotor 50 to the above-mentioned numerical values. As described with reference to FIG. 3 in the embodiment, since 0.0200 ≦ γmax ≦ 0.0250 [mm / ° degree / mm] is satisfied, the same operation and effect as in the embodiment can be obtained.

  Here, the relationship between the maximum value γmax of the flow velocity change and the rotation speed of the rotor will be described with reference to FIG. The rotation speed of the rotor is determined according to the required discharge amount of the oil pump. However, in a high rotation range exceeding the upper limit, appropriate pump performance cannot be obtained. There is.

The limit rotation speed Nmax of the rotor is defined as Umax [mm / sec. ], The change in flow velocity per unit tooth width is γ [mm / ° degree / mm], and the tooth width of the rotor is l [mm],
Nmax = Umax / (γ · l) × 60 min / 360 ° [rpm]
Is calculated.

The flow rate Umax in the allowable port is usually 10,000 to 7500 [mm / sec. It is empirically known that the smaller the maximum value γmax of the flow velocity change, the larger the value can be set. For example, when γmax = 0.021, Umax = 9500 [mm / sec. ]
When γmax = 0.033, Umax = 8100 [mm / sec. ]
Set to about.

FIG. 4 shows the relationship between the maximum value γmax of the flow velocity change and the limit rotational speed Nmax of the rotor set as described above. As shown in this figure, conventionally, since γmax is larger than 0.025 [mm / ° degree / mm], Nmax has to be set to about 8000 [rpm] at the maximum.
On the other hand, according to the present invention in which 0.020 ≦ γmax ≦ 0.025, Nmax can be set to 9000 [rpm] or more, and it can be used in a high rotation range of 12000 [rpm], which was conventionally impossible. It can be.

It is a figure showing an inscribed oil pump rotor by a 1st embodiment of the present invention. FIG. 4 is a diagram showing a comparison between an inscribed oil pump rotor according to the first embodiment of the present invention and a conventional inscribed oil pump rotor in relation to a change in flow velocity and a rotation angle position of an inner rotor. It is a figure which shows the relationship between the maximum value of the flow velocity change in an internal type oil pump rotor, a pulsation characteristic, and a noise characteristic. It is a figure showing an inscribed oil pump rotor by a 2nd embodiment of the present invention. It is a figure showing the relation between the maximum value of a flow velocity change, and the limit number of rotations of a rotor.

Explanation of reference numerals

10,50 Outer rotor 20,60 Inner rotor 30 Casing 31 Suction port 32 Discharge port l Thickness (tooth width)
C cell S cell opening area (projected area in axial direction)
V cell volume

Claims (1)

An inner rotor having Z external teeth, an outer rotor having Z + 1 internal teeth meshing with the external teeth, and an inner rotor and an outer having a suction port for sucking fluid and a discharge port for discharging fluid A casing accommodating the rotor, and an inscribed oil that conveys the fluid by sucking and discharging the fluid by a change in the volume of cells formed between the rotor tooth surfaces and the casing when the two rotors rotate while meshing with each other. A rotor used for a pump,
As the volume V of the cell at the rotation angle position θ of the inner rotor, the area S of the cell projected in the axial direction, and the tooth width l in the axial direction of both rotors,
γ = dV / dθ / S / l
The maximum value γmax of the flow velocity change γ per unit tooth width of the fluid flowing in and out of the cell is calculated by
0.0200 ≦ γmax ≦ 0.0250 [mm / ° degree / mm]
An inscribed oil pump rotor characterized by the following.

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