JPH0676899B2 - Volumetric flow meter - Google Patents

Description

TECHNICAL FIELD The present invention relates to a positive displacement flowmeter, and more particularly to a non-circular gear of a positive displacement flowmeter having a non-circular gear as a main part.

BACKGROUND ART As is well known, a volumetric flowmeter using a non-circular gear as a main part rotor has a shaft around which a non-circular gear rotor (hereinafter simply referred to as a rotor) acts on the basis of a pressure difference between an inflow and an outflow of a fluid to be measured. Due to the difference in the rotational torque between the pair of rotors, the rotors of the pair continue to rotate by reversing the relationship between the main and driven directions, and the volume formed by the rotor and the main body measurement chamber is proportional to the rotor rotation. It is a flow meter that utilizes the elimination. Such volumetric flowmeters are less affected by piping conditions and the like, and have high accuracy, so they are also used for proof of trade of fluids, reference flowmeters, and the like. The machining accuracy of such a non-circular gear directly affects the accuracy of the flowmeter, and in the case of a rotor with low accuracy, it causes an increase in meshing torque, increasing the pressure loss and increasing the gap between the measuring chamber and the rotor. Therefore, the flow meter accuracy will be reduced due to an increase in leaks. Usually, the tooth profile of a non-circular gear is an involute tooth profile, and is mainly geared by a hob. In this case, the work is cut by being given a combined motion in which the X-Y axis motion is a radius vector determined as a function of the rotation and the rotation angle according to the pitch curve. Naturally, the combined movement is a relative movement between the work and the tool, and the movement is given to the tool, or only a part of the movement, for example, the X-axis movement is given to the tool. In contrast to the above-described gear cutting work, mainly in small-scale mass-produced flowmeters, the production is diversified, for example, the rotor is manufactured by molding with a resin material or molding with a sintered metal. However, in order to guarantee the accuracy of the gears as the main part of the weighing machine, the rotor manufactured by such various means also sets the reference value and measures the main dimensions. Incorporated.

Problems of Conventional Technology In the above-mentioned conventional technology, in the dimension measurement for maintaining and managing the gear accuracy, unlike the measurement of the spur gear, the main ones are the corresponding distance between the tooth tops and the distance between the tooth bottoms. There is a distance measurement. In Fig. 4, the apex tooth profile T, T'is the major axis. Neighborhood 1 of the top tooth profile T, T'of rotor 1 when it is above
When measuring the distance Do between the tooth crests of the apex gears T, T ′, the contact point such as a micrometer is correct When it is in contact with the intersection points P and P'of The distance D between the tooth crests when measured on ▲ ▼ ′ which is inclined by Δθ is a value including an error of approximately ▲ ▼ · Δθ with respect to the correct value Do. In the measurement of the distance between the tooth flanks in the above-described apex tooth profile T, T ′, the rotor tooth tip curve P _T and the root curve P _B are parallel to the pitch curve Ps, so the measured value D is actually There is no big difference with the value Do, but the middle tooth profile,
For example, when _TN and _TN 'are taken, the distance D _N between the points K and K'
Will be measured. Normally, the shapes of the points of projection are diverse, so there is a measurement error in the above-mentioned measurement between the apex tooth profiles.
There is a problem in that accuracy control is not performed correctly because an error slightly larger than the value of Δθ is included.

Means for Solving the Problems In order to solve the above problems, in the present invention, the tooth tip curved surface and / or the tooth bottom curve is formed as a cylindrical surface which is the center of rotation of the rotor under the condition that the engagement rate is 1 or more. The purpose of the present invention is to enable correct accuracy control without measurement error due to the contact position of the contact point of the measuring instrument.

Example FIG. 1 shows an example of a non-circular gear having a pitch curve Ps in the positive displacement flowmeter of the present invention in the first quadrant XOO ′, but for ease of comparison with the present invention, The tooth profile curve in the technology is shown by the dotted line (at tooth profile T ₅ , AB
CDE). Further, in the figure, for simplification, the apex tooth profile is on the major axis ▼ in the first quadrant, and T _{1 to} T ₇
The number of teeth is shown. In the prior art, as described above,
The tooth tip curve P _T and the tooth bottom curve P _B are each parallel to the pitch curve Ps, and therefore, in each tooth profile, the tooth matching curve P _T
The distances between _B and the tooth tip curve P _T , the point of intersection of both tooth flanks, and the center of rotation O of the non-circular gear are different, and the major axis side is larger than the minor axis side. In the tooth profile curve of the present invention shown by the solid line in FIG. 1 (AFCGE in the tooth profile T ₅ ), in each tooth profile, the tooth tip curve becomes an arc having a radius of a small distance from the rotation center to the tooth top and the tooth bottom. , The root curve is used, and the distance between the corresponding arcs of the tip is of course the same at any position of the tip.

In Figure 1, when we take a tooth T _4, T ₅ as a representative tooth profile, tooth bottom curve is an arc AF of radius r _51, the addendum curve is an arc CG of radius r _52, the radius r ₅₁ , r ₅₂ are the distances from the center of rotation O to the points A and C of the tooth bottom and the tooth tip. R ₁₁ in the tooth bottom side as the radius that defines the same in other tooth _{T 1 ~T 7, r 21,} r 31, r 41, r 61, r 71, r 12 in the addendum side, r _22, r
It is an arc whose radius is ₄₂ , r ₆₂ , r ₇₂ . As shown in FIG. 2, the tooth profile curve shown in FIG. 1 meshes at a meshing ratio of 1 or more and has contacts P ₁ and P ₂ . FIG. 2 shows the binding area at a certain moment when meshing as a part of the tooth profile curves I and II in FIG. 1, and in the present invention, [P ₁ -A ₃ -A ₄ -A ₅ -A _{6 -B 6 -B 5 -B 4 -B} 3]; in the prior art _{[P 1 -A 3 -A 41 -A} 5 -A 61 -P 2 -B 6 -B 51 -B
₄ −B ₃₁ ], which is the sum of approximation triangles (A ₃
-A ₄₁ -A ₄ ) + △ (A ₅ -A ₆₁ -A ₆ ) + △ (B ₅ -B ₆ -B ₅₁ )
The area is increased by + △ (B ₄ −B ₃ −B ₃₁ ). When the radius of the root and the tip arc of the tooth profile curve in FIGS. 1 and 2 described above is the small distance from the center of rotation to the tip and the root of the prior art in each tooth profile, However, the present invention is not limited to the arc of the radius. FIG. 3 shows the tooth profile T ₅ of FIG. 1 as a representative, Is the tip curve of the prior art Radius from arbitrary position C ₁ to r ₅₂₁ of Is the tooth flank _Is a tip circular arc whose radius is from the tip C ₂ to r _522. Is the root curve of the prior art From the arbitrary position A ₁ of the meshing tooth surface The radius is r ₅₁₁ up to the closing position F ₁ of From the F position to the meshing tooth surface Is a root arc with radius r _512, which is a further increase of
It is an arc selected so as to satisfy the condition that the engagement rate is 1 or more. The present invention includes all arcs that satisfy this condition, and does not include the case where the tip curve and the root curve are all arcs, but includes the case where only the tip part or the root part is arced. It is a waste.

Effects As described above, the present invention provides the tooth top curved surface and the tooth bottom curved surface in the rotor as a main part of the non-circular gear type positive displacement flowmeter to be the cylindrical surface for each tooth profile.
The reliability of dimensional measurement accuracy, which is the basis for controlling the accuracy of gears, is improved, and a uniform and highly accurate volumetric flow meter can be provided. In particular,
With a general-purpose flowmeter, the reliability of the management accuracy of a small mass production rotor by molding using a resin mold or a mold made of a sintered alloy or the like becomes high. Further, the meshing capacity of the non-circular gear of the present invention in meshing is larger than that of the prior art, and as a result of suppressing the meshing pressure increase, the effect of reducing the bearing friction torque and the measured pressure loss is large. In addition to improving accuracy, it contributes not only to accuracy but also to economic effects.

[Brief description of drawings]

FIG. 1 is a view showing an example of a non-circular gear in the first quadrant, the solid line is the present invention, and the dotted line is the conventional tooth profile curve. FIG. 2 is an enlarged view for explaining a binding area of a meshing tooth profile, FIG. 3 is a view showing another embodiment of the present invention, and FIG. 4 is a conventional vertex tooth profile on a major axis. It is a figure which shows the dimension measurement in the case. T ₁ ~ T ₇ …… Tooth profile, P _T …… Tooth curve, P _B …… Toth root curve, Ps
...... Pitch curve.

Claims (1)

[Claims] 1. A positive displacement flowmeter, the main part of which is a pair of non-circular gears of equal size, which rotate in mesh with each other in proportion to the flow rate, in a range satisfying a meshing condition in which the meshing ratio of the non-circular gears is 1 or more. The volumetric flowmeter, wherein the tooth profile of is a tooth top curved surface and / or a tooth bottom curved surface is a cylindrical surface centered on the rotation center of the non-circular gear.