JPS623885B2 - - Google Patents

Description

[Detailed description of the invention] In polar coordinates, the radius vector length ρ ₁ is expressed as a, b and c
When is a number related to length, d is a positive number from zero to 1, and x is a self variable, the following formula ρ ₁ = a + cos2x {cd ² | sin ² 2x | / (1-d
² cos ² 2x) ² -b} and μ is a number determined by a, b, c, and d, then the direction angle θ ₁ of ρ ₁ is a curve drawn from the following equation θ ₁ = 1/μ∫dx/ρ ₁ And the length of the radius vector ρ ₂ of another curve that engages with this in polar coordinates is expressed by the following formula ρ ₂ = a-cos2x {cd ² | sin ² 2 x |/(1-d
² cos ² 2x) ² -b} and the direction angle θ ₂ of the radius vector from the following equation θ ₂ = 1/μ∫dx/ρ ₂ A pair of non-circular curves with similar curves as pitch lines The so-called non-circular gear flowmeter, which has a gear rotor (hereinafter referred to as rotor) housed in a housing, exhibits a measurement function by rotating the rotor with the fluid to be measured. No. 57821 (Special Publication No. 53-
A rotor shape with a large discharge rate (ratio of the discharge amount by the rotor to the volume inside the instrument chamber) described in Publication No. 40469) has a significantly lower sensitivity flow rate than conventional similar meters with a low discharge rate. However, there is a problem in that precise indication function is lacking because instrumental error changes occur depending on the flow rate.

Figure 1 shows the rotor rotational speed and instrumental error of a commercially available conventional elliptical gear type flowmeter and a rotor flowmeter described in Japanese Patent Application No. 57821/1983 (Japanese Patent Publication No. 40469/1983). This is an instrumental error curve obtained from a test showing the relationship between The curve is from Japanese Patent Application No. 1972-57821 (Special Publication No. 53
-40469 Publication), the curve is the instrumental error-velocity curve of the conventional product. The sensitivity flow rate of the rotor with a large discharge rate in the former shows a much lower flow rate than the latter, but in the low flow region, that is, at low speed rotation, the theoretical discharge rate (indicated by the horizontal line with instrumental error of 0.0% in the figure) showed a high positive value.

The feature of positive displacement flowmeters is that the instrumental error changes are small in the low flow rate range and high flow rate range.As a result of investigating the reason why the rotor with the large tooth profile and high discharge rate shows a large instrumental error change, we found that the It was discovered that this is due to the flow rate, that is, when the rotor rotates at low speed, the fluid is trapped at the meshing part between the two rotors, causing a backflow phenomenon to the inlet side. To explain the backflow phenomenon in Fig. 2, the gears 3 and 4 of the pitch lines 1 and 2 are
_{1 , 0 2} as centers and rotated by fluid _pressure in the direction of _the arrow. The minor axis 8 (0 ₂ 2 ₁ ) and the major axis 9 (0 ₂ 2
₂ ) rotate while engaging with each other. However, as shown in the figure, in the case of low speed rotation, rotor 3 is rotor 4.
The long diameter tooth surfaces 10, 11 of the rotor 3 are rotated by
In this case, the meshing tooth surfaces 12 and 13 contact each other with a counterclockwise torque in the figure due to the difference in rotational torque shown by the lengths of the minor axis 8 and major axis 9 of the rotor 4, and rotation is transmitted. , a contact portion 16, 17 between the teeth of both rotors, which is defined by the short diameter tooth surfaces 14, 15 of the rotor 4;
As the fluid rotates, the fluid flows back into the gap 19, which is closed by the meshing part 18 and has a gap between the meshing parts 18 that do not contact each other due to the difference in torque, toward the inlet port. do. That is, void 1
This is because the volume of the tooth surface 9 decreases and the tooth surface 14 is pushed back toward the inlet by the pump action that pushes the tooth surface 10 to the left in the figure. Since the tooth shape of the long diameter part described in Japanese Patent Application No. 48-57821 (Japanese Patent Publication No. 53-40469) is large, the amount of entrapment between it and the short diameter part of the partner is large, accounting for approximately 2% of the discharge amount. Therefore, due to the backflow effect, the instrumental error becomes a positive value in the low speed section, and also shows a large value. The volume of the aforementioned confinement further decreases as both rotors rotate, and in the case of an incompressible fluid such as water, an excessive surface pressure is applied to the meshing surfaces. Therefore, even if the tooth surface has a back gap-like gap, deformation due to scratches occurs over time, and this momentary confinement pressure is applied, causing damage to the rotor's meshing surface and shaft hole. High hardness metal plating,
It is also necessary to improve and protect the sliding surfaces by ceramic coating, etc. During low speed rotation, torque mainly due to fluid pressure acts on the rotor, and as shown in _FIG . Arm 0 ₁
20 is applied, but the rotor 4 has a long diameter of 9.
Since the rotor 4 receives a large torque in the direction of the arrow due to the difference between the short diameter and the minor axis 8, the rotor 3 is rotated by the rotor 4. Next, when both rotors rotate to the parallel position shown in FIG. The meshing surface pressure becomes zero. That is, in the case of low speed (low flow rate), surface pressure due to the rotational torque of both rotors is applied to each tooth of the gear 4 shown in FIG. 5 on the tooth surface indicated by a thick line. This indicates that the rotor 4 rotates in the direction of the arrow and the tooth profile of the opposing rotor 3 contacts the tooth profile shown in thick line, and also indicates that the axes of both rotors are in a parallel position, that is, at the midpoint 24 of the pitch line. In the boundary range E-RO, a positive rotational torque acts to rotate the rotor 3, and in R-HA, it is rotated by the rotor 3, and the same process is repeated thereafter.

A back gap between both gears is essential for the smooth rotation of a non-circular gear rotor, but when rotating at low speeds, the rotor repeatedly accelerates and decelerates, and the rotational torque alternately reverses, so this backflow effect occurs. It causes

The present invention has been made specifically for the purpose of improving the accuracy of a small flow meter that measures minute flow rates, and because the back clearance of the meshing teeth of a small rotor is a relatively large value, for the above reason. As a result of the backflow phenomenon of the measured fluid towards the inlet side, accurate measurement of minute flow rates could not be obtained. By using a rotor, the difference in metering function between low speed and high speed rotation can be eliminated.

The instrumental error curve in Figure 1 shows a value equal to zero at high speed rotation, and to explain this using Figure 6, the moment of inertia becomes effective from around 100 to 200 rpm due to the high speed rotation of the rotor 4. Because of this, the direction of the rotational force is alternately reversed with the major and minor axes as boundaries in the figure. The rotor 3 is rotated by the rotor 3, and within the rotation angle range of the rotor 4, it is rotated by the rotor 4. Surface pressure is applied to the tooth surface shown by the bold line, and the inflow port side and the outflow port side are blocked at the meshing part due to contact with the opposing tooth surface, and there is no blocking effect particularly by the tooth surface 11 of the long diameter tooth. There is no backflow of the measured fluid to the inlet side, so there is no difference from the theoretical value.

Due to the above reasons, there is a difference in instrument error in the low flow rate and high flow rate ranges, so such defects are made into a tooth profile that pushes out all the fluid trapped between the teeth at the meshing part during low speed rotation to the outlet side. I got it resolved by this. Patent Application No. 1972-68811 (Japanese Patent Application No. 1973-
Publication No. 47995), Japanese Patent Application No. 53414 (1972)
The relief groove structure to prevent entrapment described in Publication No. 145766 does not completely prevent backflow to the inlet side due to the torque change at low speed rotation, so linearity of the instrumental error curve cannot be obtained, and the flow rate However, this was not avoided due to changes in instrumental differences.

The back gap-like notch provided in the tooth profile of the present invention to completely prevent the fluid trapped in the meshing portion as the rotor rotates from flowing back to the inlet side is disclosed in Japanese Patent Application No. 1973-
Use the rights of No. 141673 (Special Publication No. 60-27930).

The invention of the present application will be explained below with reference to Examples. 7th
The figure shows an embodiment in which a non-circular gear rotor 3 and a rotor 4 with relief grooves are housed in a housing 5. A part of the tooth profile of the short diameter portion of the rotor 4 is cut in a back gap shape along the meshing tooth surface 14 on the side opposite to the direction of rotation shown by the arrow to form a notch 27 and provide an escape groove 28. A similar notch surface 29 is cut in a part of the tooth pattern 11 on the long diameter portion in the opposite direction, that is, on the rotational direction side, and an relief groove 30 is provided. As shown in FIG. 8, since the rotational torque of the rotor 4 is larger than that of the rotor 3, the meshing tooth surfaces 10 rotate while being pushed to the left by the tooth surfaces 14, causing the tooth surfaces 10 and the notched tooth surfaces 27 The fracture measuring fluid in the space 19 flows out in the direction of the arrow as the volume decreases through the relief groove 28 formed between the two, and the above-mentioned backflow does not occur, so that no increase in instrumental error occurs in the small flow rate region. FIG. 9 is a three-dimensional explanatory diagram of the rotor 4 with the relief grooves shown in the previous figure.This phenomenon was confirmed through an actual machine test by obtaining the instrumental error curve shown in FIG. 1. The fact that the instrument error does not change depending on the rotation speed and can be used as an industrial meter with a wide flow range makes it possible to meet the demands of the chemical industry, etc., which require highly accurate measurement control. Accuracy of flow range ±0.2 to ±0.1
%, and was able to provide a high-performance product that is unrivaled by other types of meters. Figure 10 shows the tooth surfaces 11 of the long diameter teeth on rotors 3 and 4, respectively.
In this embodiment, an escape groove 30 is provided along the back gap to prevent the fluid from flowing back toward the inlet.
In addition, a combination in which the short diameter tooth surface 14 is notched has the same effect of preventing the backflow of trapped fluid.
Furthermore, the confinement has the effect of reducing braking resistance during high-speed rotation. Such an application example is also included in the patent claim, in which the notch portion bordering on the midpoint of the pitch line of the rotor of the non-circular gear with small teeth shown in FIG. It is also possible to provide an application in which the fluid trapped between the teeth is prevented from flowing back to the inlet side.

The present invention improves the instrumental error characteristics of a non-circular gear type flowmeter with low sensitivity flow rate and high discharge rate in a positive displacement flowmeter with little internal leakage, and provides an industrial meter for precise flow measurement. This invention is not limited to the embodiments, but the principles of the present invention include a gear rotor with a mechanism that pushes trapped fluid only toward the outlet side by the torque that the rotor receives from the fluid when rotating at low speed. Of course, this includes such applications as long as they can be used.

[Brief explanation of the drawing]

FIG. 1 is a graph for comparing instrumental error curves of a conventional product and a flowmeter according to the present invention. Figure 2 is an explanatory diagram of the backflow phenomenon of trapped fluid in a conventional flowmeter.
Figures 3 and 4 are explanatory diagrams of the relationship between torque depending on the rotational position of the rotor, Figure 5 is an explanatory diagram showing the total tooth pressure applied to the teeth of the rotor during low speed rotation, and Figure 6 is an explanatory diagram showing the tooth joint pressure applied to the teeth of the rotor during high speed rotation. FIG. 7 is an explanatory diagram of the embodiment of the present invention; FIG. 8 is a detailed explanatory diagram of the backflow prevention effect by the relief groove of the embodiment of the present invention; A three-dimensional explanatory diagram of the rotor of the embodiment, FIG. 10 is an explanatory diagram of another embodiment, and FIG.
The figure is an explanatory diagram of an embodiment according to the present invention in which relief grooves are provided on each tooth surface with the boundary at the midpoint of the pitch line to prevent backflow of trapped fluid caused by torque at low speeds. 1... Pitch line, 2... Pitch line of driven rotor, 3... Non-circular gear rotor, 4... Driven rotor, 5... Housing, 6... Short diameter of rotor, 7... ... Long axis of the rotor, 8 ... Short diameter of the driven rotor, 9 ... Long axis of the driven rotor, 10, 11 ... Tooth surface of the tooth on the long diameter section, 14, 15 ... Teeth of the tooth on the short diameter section Face, 16,1
7, 18...Meshing contact point of rotor, 19...Confinement by long diameter tooth, 24...Midpoint of pitch line, 2
4,25...Radius of both rotors in parallel position,
27, 29, 31, 33... Notched tooth surface,
28, 30, 32, 34...Escape groove.

Claims (1)

[Claims] 1. In polar coordinates, the length of the radius vector ρ ₁ , where a, b, and c are numbers related to length, d is a positive number from zero to 1, and x is a self variable, then the following equation ρ ₁ = a + cos2x {cd ₂ | sin ² 2x |/(1-d
² cos ² 2x) ² -b} and μ is a number determined by a, b, c, and d, then the direction angle θ ₁ of ρ ₁ is a curve drawn from the following equation θ ₁ = 1/μ∫dx/ρ ₁ And the length of the radius vector ρ ₂ of another curve that engages with this in polar coordinates is expressed by the following formula ρ ₂ = a-cos2x {cd ² | sin ² 2 x |/(1-d
² cos ² 2x) ² -b} and the direction angle θ ₂ of the radius vector from the following equation θ ₂ = 1/μ∫dx/ρ ₂ A pair of non-circular curves with similar curves as pitch lines In a flowmeter in which a gear rotor (hereinafter referred to as rotor) is housed in a housing,
A back-gap-like notch or relief groove is formed on the opposite surface of the rotor in the direction of rotation in the tooth profile of the long diameter portion whose boundary is the midpoint of the pitch line between the long and short diameters of one or both pitch lines of the rotor. A back gap-like notch or relief groove is provided on the rotational direction surface of the tooth profile of the short diameter portion with the midpoint of the pitch line as the boundary, and the fluid to be measured is occluded between the meshing teeth when the rotor rotates at low speed. A non-circular gear type flowmeter that prevents backflow to the inlet side.