JPH0660835B2 - Positive flow meter - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel positive displacement flow meter having a rotor having a non-circular gear as a timing gear.

2. Description of the Related Art Positive displacement flowmeters represented by Oval flowmeters and roots flowmeters each have a pair of rotors built-in, and the flowrate is obtained from the rotation of the rotors in proportion to the flowrate. The movement of the flow meter rotor during flow rate measurement is complicated and varies depending on the type of fluid to be measured, piping conditions, and the like. For example, looking at the relationship between the kinetic energy of the flowmeter rotor during measurement and the kinetic energy of the fluid, in the extreme case, that is, the fluid is a liquid and the rotational energy of the rotor is ignored with respect to the kinetic energy of the fluid. Then, when the fluid is a gas and the kinetic energy of the fluid is ignored with respect to the rotational energy of the rotor, in the former case, the rotor performs non-constant rotation at a constant area velocity at a constant flow rate, On the other hand, in the latter, the rotor makes a free rotational motion with a constant rotational energy. In general. It is an intermediate exercise between the two. Looking at this in the case of an oval flowmeter, the pitch curve motion is expressed in two-dimensional polar coordinates (ρ, θ) with the origin of the axis of rotation of the pitch curve of a non-circular gear with similarity coefficient a and flatness b. The diameter ρ is the angle of deviation θ
(Hereinafter, ρ (θ)), one of a pair of isomorphic pitch curves is ρ ₁ (θ ₁ ), and the other is ρ (θ ₁ ).
₂ (θ ₂ ) The pitch curve ρ ₁ (θ ₁ ) of the non-circular gear at this time is And the angular velocity of the rotor with constant area velocity and constant rotation energy when b = 0.3 And discharge rate accompanying rotor rotation Is shown in FIGS. 5 (A) and 5 (B). These figures show the angular velocity,
The ratio of the average angular velocity and the average discharge amount to the discharge amount is expressed as a dimensionless amount.

Problems As described above, in a typical positive displacement flow meter, even with the same flow meter, the rotational motion form of the rotor varies depending on the properties of the fluid to be measured, the fluid volume in the pipe, and the like. As a result, various problems occur. For example, in the case of liquid measurement, depending on the conditions, the fluid that was trying to flow at a constant flow rate becomes a pulsating flow, which causes vibration or changes in angular velocity cause changes in angular acceleration, which accelerates wear of gears,
There were various problems such as the cause of noise.

Means for Solving the Problems A condition for equalizing the angular velocity fluctuation rate in the equal flow motion and the angular velocity fluctuation rate in the free rotation is obtained, and the flow meter main part configuration satisfying this condition is obtained. That is, the object is to make the same motion under all conditions by giving a condition that the area velocity is constant when the rotor is freely rotated.

Specific Example First, the conditions for matching the angular velocity during the uniform flow motion and the angular velocity during the free rotation are obtained.

In FIG. 4, when ρ ₁ (θ ₁ ) and ρ ₂ (θ ₂ ) are non-circular gears and radii of R ₁ and R ₂ , R ₁ ² = ρ ₁ ² + r ² +2 ρ ₁ rcos ₂ ψ R ₂ ² = ρ ₂ ² + r ² −2ρ ₂ cos ψ Therefore, when the major axis of the rotor is R ₀ and the center distance is K, the discharge area flow rate V is Becomes

Therefore, the angular velocity fluctuation rate in uniform flow motion (Is the average angular velocity) is as follows.

On the other hand, the angular velocity fluctuation rate in free rotation Is Becomes here, If you say, And from this, Is obtained. That is, if a rotor is an envelope of a circle group having a radius r and having the pitch point of the non-circular gear ρ (θ) as the center, the formula (2) is satisfied, Becomes

Here, in ρ ₁ = ρ ₂ = K / 2, since r = 0, this is substituted into the equation (2), Then, if the long radius of the non-circular gear is ρ ₀ , then
Since R ₀ = ρ + r at ρ ₁ = ρ ₀ , this is substituted into the equation (2), From this, when solving for (R ₀ / K), Becomes

From the above, when the pitch curve ρ (θ) of the non-circular result is given, r is obtained from the equations (3), (4) and (2),
The rotor is given as its envelope.

FIG. 1 shows a non-circular tooth for realizing the present invention, 2 shows a timing gear 2 at b = 0.3 and a rotor (R) 1 composed of an envelope of r centered on the pitch curve ρ (θ), and FIGS. Shows a principle structure diagram when applied to volumetric flow rate. In the figure, 11 and 12 are rotors forming a pair of the rotors shown in FIG. 1, respectively, with the axes 41 and 42 in the measuring chamber 5 as axes,
The flow in the arrow B direction receives the rotational torque in the R direction.
Timing gears 21 and 22 that are coaxially meshed with the timing gear chamber 7 are fixed to the shafts 41 and 42.
Since it is rotatably supported by 1, 62, the flow rate is measured without pulsation according to the rotational torque caused by the flow.

In the above embodiment, the timing gear is also b =
Although the case where the oval gear of 0.3 has been described, the present invention is applied to all non-circular gears.

Effect As described above, according to the present invention, a uniform flow rate and non-pulsating rotor movement can be obtained regardless of the type of fluid to be measured, so that a flow meter free from vibration and noise can be obtained. Also, vibration,
Since the noise energy is replenished by the pressure loss of the fluid to be measured, the removal of vibration and noise brings about the improvement of the measurement accuracy.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention, showing the relationship between the timing gear and the rotor at b = 0.3, and FIGS. 2 and 3 show the case where the present invention is applied to a flow meter. FIG. 4 is a sectional view showing the relationship between a non-circular gear and a rotor for analyzing the present invention, and FIG. 5 is a limit condition of a conventional positive displacement type flow meter. Angular velocity in the case of (B) Discharge rate FIG. 11, 12 ... Rotor, 21, 22 ... Timing gear, 3 ... Outer casing, 41, 42 ... Shaft.

Claims (2)

[Claims] 1. A positive displacement flowmeter comprising: a pair of timing gears, which are non-circular gears that mesh with each other, and a pair of rotors, which are coaxially fixed to the timing gears and rotatably supported in a measuring chamber. When the pitch curve of the timing gear is represented by two-dimensional polar coordinates (ρ ₁ , θ ₁ ) with the rotation axis of the pitch curve as the origin, the radial angle ρ ₁ is the deviation angle θ ₁
And a center of the rotor curve on a pitch curve having the same radial radius ρ ₁ and declination θ _{1 as the} timing gear, R ₀ : Maximum radius of rotor K: Center distance k: Envelope of a circle of radius r represented by a dimensionless constant, when the envelope is the radius of the pitch curve of the rotor is K / 2 The displacement type flow meter is characterized in that the angle is defined as the boundary, and the short radius vector side is on the rotary shaft side, and the long radius vector side is on the far side from the rotary shaft. 2. When the similarity coefficient of the pitch curve of the non-circular gear is a and the flatness is b, The positive displacement flowmeter according to claim 1, wherein