KR20050001379A - Non circular gear and positive displacement flowmeter using it - Google Patents

Abstract

PURPOSE: A non circular gear and a positive displacement flowmeter using the same are provided to ensure a sealing capability by reducing the number of teeth. CONSTITUTION: A pair of non circular gears are installed in a casing. The non circular gears have a teeth type curve. The teeth type curve varies with the non circular gear installation place and the size of an inner wall of the gear. The teeth type curve has 14 or 18 as the number of teeth. The teeth type curve has a single closed curve or multiple closed curves. The non circular gear includes resins. The casing includes a measurement chamber in a positive displacement flowmeter(10). The positive displacement flowmeter has a pair of non circular gears. The non circular gears are installed as a rotor in the positive displacement flowmeter(10).

Description

NON CIRCULAR GEAR AND POSITIVE DISPLACEMENT FLOWMETER USING IT}

The present invention relates to a volumetric flow meter using a non-circular gear and a non-circular gear.

Conventionally, non-circular gears have been used in volumetric flowmeters, pumps, and the like. Among the non-circular gears, the oval gear whose pitch curve is represented by ρ = a / (1-bcos2θ) has a large change in the engagement pressure angle due to rotation, and a long diameter portion. To avoid interference such as deterioration of teeth in the tooth, the tooth module is made smaller and the number of teeth is increased. Here, p is the motion diameter, a is the similarity coefficient, b is the flatness, and θ is the declination angle.

As a technique which does not increase the engagement pressure angle by rotation, an oval gear, which is a kind of elliptical gear, has been proposed (for example, see Japanese Patent Application Laid-open No. Hei 1-39052). The oval gear is a non-circular gear designed to reduce the change of the engagement pressure angle and never become negative by always toothing the actual portion of the tooth curve engraved on the pitch curve of the gear in the rotational center direction. This oval gear is widely used as a rotor of a volumetric flowmeter because the discharge amount per revolution is large and high precision can be maintained for a long time.

In addition, as a technique for preventing the lowering of the involute teeth, a deformation ellipse gear having a special potential has been conventionally proposed (for example, Ichikawa Tsuneo, 'Gear Pump', Daily Industries). Newspaper, issued August 20, 1962, pp. 165-166}. This deformed ellipse gear has 14 teeth, which is assembled in a pump known as a Seiko pump, and the seal portion of the gear with the inner wall of the pump located at the top of the long diameter of the gear has a long axis direction. It consists of one tooth each at the end. In addition, this deformed ellipse gear is a tooth shape without a drop, but has an overhang portion. Here, the overhang portion refers to a portion where the tooth profile is pushed out from a straight line connecting the contact point between the pitch curve and the engagement surface of each tooth and the ellipse center.

On the other hand, non-circular gears are often made of a metal material, but in some cases, they may be made of inexpensive resin molding in consideration of cost. However, in the case of considering a non-circular gear of resin molding, it is necessary to increase the moldability and improve the tooth strength. For this purpose, the tooth module must be enlarged to reduce the number of teeth.

As a technique for reducing the number of teeth, the modified elliptical gear described in the above-described "Ichikawa Tsuneo" gear pump "is mentioned, but this gear will have the tooth shape which has an overhang part. The elliptical gear by resin molding is formed by shrinking the resin toward the elliptic center direction in the mold when the resin is injected and solidified. However, since there is no contraction direction in the overhang portion, the elliptical gear cannot be contracted and defects are likely to occur at the portion. Therefore, it is required to design the teeth so that there is no overhang.

Moreover, as a non-circular gear, the projection gear which has a projection tooth shape is also proposed (for example, refer Unexamined-Japanese-Patent No. 62-3885). The non-circular gear flowmeter described in Japanese Patent Application Laid-Open No. 62-3885 is used to protrude the teeth of a long diameter part and to increase the accuracy of measurement as a small flowmeter and to increase the discharge amount per revolution. And a non-circular gear formed of a short diameter portion engaging the notch.

As described above, when the non-circular gear is manufactured by resin molding, it is necessary to increase the strength of the resin teeth, and therefore, it is necessary to increase the module. However, in order to increase the module, the size of the entire gear is also limited. Less teeth are required. However, in non-circular gears, it is necessary to form an overhanging tooth by resin molding only by increasing the ratio of the module to the entire gear by tilting the tooth by increasing the tool pressure angle while preventing a drop. And, as a result, a defect occurs at that portion.

Japanese Patent Application Laid-open No. Hei 1-39052 discloses a tool pressure angle (pressure angle of a tool for making an involute tooth first) by always attaching a substantial portion of a tooth curve engraved on a pitch curve of a gear or the like in the center of rotation. Although the oval gear is designed to tilt the teeth so that the engagement pressure angle does not become negative in setting, and as a result, there is no tooth with an overhang portion, there is no description of a technique that has no overhang portion and fewer teeth. not.

In the flowmeter described in Japanese Patent Application Laid-Open No. 62-3885, in the case of actually designing and manufacturing a projection gear in which the rotor shaft is fixed to the casing (here, the metering chamber) side, the projection of the top portion is proportional to the module. Inevitably, the depression of the concave portion engaged with the projection is also increased, and it is not possible to secure an area in which the bearing to be provided at the center of the projection gear enters. Moreover, also in the projection gear of Unexamined-Japanese-Patent No. 62-3885, the technique for reducing the number of teeth so that it does not have an overhang part is not described. Therefore, since the number of teeth increases, this projection gear must be made to reduce the seal length (sealing width) between the projection of the tip portion and the inner wall of the casing. Gears with a short seal length have a large amount of leakage from the tip, and are not suitable for installation in a volumetric flowmeter.

In addition, in the non-circular gear according to the prior art such as Japanese Patent Publication No. Hei 1-39052, in order to reduce the number of teeth and to prevent overhang, the tool pressure angle is increased to the tip limit so that the teeth are inclined and sharpened. Although it can be considered, since the seal portion between the non-circular gear and the inner wall of the casing for installing it is almost lost and the sealability cannot be secured, wear at the tip portion is severe according to the rotation in which the gear is engaged. Therefore, especially in the case of a top part and the teeth of its vicinity, it is not designed to bend to the tip limit.

In addition, it is not limited to non-gear gears of resin molding, and even non-gear gears formed of, for example, metals have a drawback that the teeth and the seal length that are sharpened to the tip limit are shortened. Therefore, even in non-round gears other than resin molding, the design using the teeth sharpened to the tip limit has not been achieved.

An object of the present invention has been made in view of the above-described circumstances, and it is advantageous to set the change in the engagement pressure angle, to advantageously set the tool pressure angle on the engagement surface, and to reduce the number of teeth without forming an overhang portion, so that the casing It is providing the non-circular gear and the volumetric flowmeter provided with the non-circular gear which can fully ensure the sealing property with the inner wall of a casing when installed in the inside.

This invention is comprised by each technical means described in the following claims.

The 1st technical means of Claim 1 is a non-circular gear provided in a pair in a casing, This non-circular gear has 4n + 2 pieces of teeth (n is a natural number), The both ends of a long axis are two grooves, It has a tooth curve with both ends at the end, the interlocking surface at the involute curve, and the non-engaging surface at the cycloid curve. The tool pressure angles of the involute curve of each tooth in the tooth curve are the lower limit and the tip. The non-circular gear, which is set by the limit, fills in the recess between two teeth fitted with the two grooves, including the two grooves at the both ends of the long axis, based on the tooth curve, and also the two ends of the short axis. It is characterized in that the number of teeth cut off the teeth including the tip of the teeth has a shape of 4n-2 pieces.

As for the 2nd technical means of Claim 2, in the 1st technical means, the said non-circular gear is a convex part which has the shape which filled the said recessed part, and the said tooth part in the non-circular gear like this non-circular gear. It is characterized by being comprised so that the recessed part which has a shaved shape may be engaged.

In the third technical means described in claim 3, in the first or second technical means, the tooth curve is determined by the installation location of the non-circular gear in the casing and the size of the inner wall. It is characterized in that the recess is filled with an arc corresponding to the inner wall of the casing.

As for the 4th technical means of Claim 4, in a 1st or 2nd technical means, the said tooth curve is determined by the installation place of the said non-circular gear in the said casing, and the magnitude | size of an inner wall, The said shape is said The recess is filled with a curve aligned with the inner wall of the casing, and the filled curve is brought into contact with the bottom of the recess formed by shaping the tooth in a non-circular gear such as the non-circular gear.

In the fifth technical means described in claim 5, in the technical means in any one of the first to fourth aspects, the tooth curve has 14 or 18 teeth, and as a result, 10 or 14 teeth, respectively. It is characterized by the configuration.

As for the 6th technical means of Claim 6, the technical curve of any one of the 1st-5th, The pitch curve of the said non-circular gear is a single closed curve which satisfy | fills a rolling contact condition, or the closed curve which combined several types. It is characterized by that.

As for the 7th technical means of Claim 7, in the technical means in any one of 1st-6th, the said non-circular gear is formed with resin, It is characterized by the above-mentioned.

The eighth technical means according to claim 8 is the technical means according to any one of the first to seventh aspects, wherein the casing is a metering chamber in a volumetric flowmeter.

A ninth technical means according to claim 9 is a volumetric flowmeter provided with a pair of non-circular gears according to the eighth technical means, wherein the pair of non-circular gears is engaged as a pair of rotors in the weighing chamber. And a flow rate meter for measuring the flow rate of the fluid under measurement discharged by the pair of rotors.

From this configuration, according to the present invention, in the non-circular gear, the change of the engagement pressure angle is reduced, and it is advantageous to set the tool pressure angle on the engagement surface, and the number of teeth is reduced without forming an overhang portion, so that the casing When installing inside, the sealing property with the inner wall of a casing can be ensured enough.

In addition, according to the volumetric flowmeter according to the present invention, since the non-circular gear is used, it is possible to measure the flow rate with high accuracy.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the structural example of the volumetric flowmeter provided with the non-circular gear which concerns on one Embodiment of this invention.

2 is a diagram illustrating an example of a configuration of a non-circular gear according to an embodiment of the present invention.

3 is a series of configuration diagrams for explaining points taken into consideration when designing the non-circular gear of FIG. 2.

4 is a series of configuration diagrams for explaining points taken into consideration when designing the non-circular gear of FIG. 2.

FIG. 5 is a series of configuration diagrams for explaining points taken into consideration when designing the non-circular gear of FIG. 2.

FIG. 6 is a series of configuration diagrams illustrating points taken into consideration when designing the non-circular gear of FIG. 2.

7 is a diagram showing an example of the configuration of a non-circular gear according to another embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

10 volumetric flow meter 11: box (outer box)

12: cross-section plate 15: electrical sensor

20: metering chamber 21: inlet

22: outlet 23, 27: rotor (non-circular gear)

23a: gear part of the rotor (engagement part) 23b: end face of the rotor

24: axis of rotation of the rotor 25, 26: magnet

30, 30 ': first non-circular gear

31 to 37, 41 to 47: first to fourteenth teeth in the first non-circular gear

33a: interlocking in third tooth

33b: Non-interlocking in third teeth

33c: tooth tip in third tooth

36a: Interlocking on the sixth tooth

36b: Non-interlocking in sixth tooth

36c: tooth tip in sixth tooth

38, 48: recessed part in 1st non-circular gear

39, 39 ', 49, 49': projections in the first non-circular gear

50, 50 ': second non-circular gear

51 to 57, 61 to 67: first to fourteenth teeth in the second non-circular gear

58, 68: recessed part in second non-circular gear

59, 59 ', 69, 69': Convex portion in second non-circular gear

O1: center of the first non-circular gear

O2: center of 2nd non-circular gear

L: tooth curve

La: If it is engaged

Lb: If it's not interlocking

Lc: this end

P: pitch curve

R: radiation from the center of the pitch curve

T: curve connecting tooth ends

B: Curve connecting the bottom of the tooth

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the structural example of the volumetric flowmeter provided with the non-circular gear which concerns on one Embodiment of this invention, FIG. 1: (A) is sectional drawing of the arrow line AA of FIG. 1 (B) is a cross-sectional view taken along the line BB of FIG. 1A. In the figure, reference numeral 10 is a volumetric flow meter, 11 is a box body (outer box), 12 is an end plate, 15 is a magnetic sensor, 20 is a measuring chamber, 21 is an inlet, 22 is an outlet, 23 and 27 is a rotor, and 23a is The gear part (engagement part) of the rotor 23, 23b is an end surface of the rotor 23, 24 is a rotating shaft of the rotor 23, and 25 and 26 are magnets.

The volumetric flow meter 10 includes a metering chamber 20 corresponding to a space formed by an outer box 11, a cover (end face plate) 12, an outer box 11 and an end face plate 12, And a rotor 23 and a rotor 27 such as that arranged in the metering chamber 20 and rotatably supported around the rotation shaft 24, and the magnetic sensor 15 as its main components.

The metering chamber 20 has an inner wall of the outer box 11 connected to the inlet 21 and the outlet 22 and a non-attachment attached to the outer box 11 to seal the opened outer box 11. It is comprised by the end surface plate 12 which consists of magnetic materials. In addition, in the metering chamber 20, the rotating shaft 24 is vertically and parallel to each other, and is rotatably supported by the rotor 23 of the non-circular gear rotatably supported by the rotating shaft 24 and the same rotating shaft. The rotors 27 of the non-circular gears are arranged to engage with each other. The rotors 23 and 27 of the non-circular gear which is a feature of the present invention will be described later.

Further, magnets 25 and 26 are embedded in the end face 23b of one rotor 23 at an axisymmetric position (in this case, a long diameter). In this way, the columnar magnets 25 and 26 are pressed into the end faces 23b of the rotor 23 which rotates in proportion to the volume of the fluid flowing in the metering chamber 20, and the magnets 25 and 26 Magnetic flux is detected by the magnetic sensor 15 disposed on the end face plate 12. In this configuration example, an example in which the magnets 25 and 26 are embedded in the rotor 23 is illustrated. Alternatively, the magnets 25 and 26 may be embedded in the rotor 27, and only one magnet may be embedded.

In addition, although the above-described volumetric flowmeter employs a magnetic sensing method, an electronic sensing method may be employed and a method of optically detecting the position of the rotor (optical position detection method) or the What is necessary is just to employ | adopt the system which transmits rotation of a shaft mechanically, and just to measure the rotational motion of a rotor by some means.

The non-circular gear, which is not limited to the above-described volumetric flowmeter but also can be installed by engaging a pair of rotors in a volumetric flowmeter for measuring the flow rate of the fluid under measurement discharged by a pair of rotors, will be described in detail. do.

FIG. 2 is a diagram showing an example of a configuration of a non-circular gear according to an embodiment of the present invention. FIGS. 2A and 2B show engagement of a pair of non-circular gears according to their rotational positions. Figure is shown. In the figure, reference numeral 30 denotes the first non-circular gear, 31-37, 41-47 are the first to fourteenth teeth in the first non-circular gear, and 33a, 33b, and 33c respectively indicate the third tooth. If interlocked, non-engaged, this is the end, 36a, 36b, 36c are interlocked, sixth-engaged teeth, non-engaged, toothed in the sixth tooth type, 38, 48 are recesses in the first non-circular gear, 39 And 49 are convex portions in the first non-circular gear, 50 are second non-circular gears, and 51 to 57 and 61 to 67 are first to fourteenth teeth in the second non-circular gear, respectively. And 68 are recesses in the second non-circular gear, 59 and 69 are convex portions in the second non-circular gear, O1 is the center of the first non-circular gear, and O2 is the It is the center.

The non-circular gears 30 and 50 (corresponding to the rotors 23 and 27 in Fig. 1) according to one embodiment of the present invention are non-circular gears to be provided in pairs in a casing and have the following tooth curves. It shall have. Here, a casing corresponds to the measurement chamber in a volumetric flowmeter. Here, the non-circular gears 30 and 50 are formed of resin (by molding of a resin mold or the like), so that not only can be manufactured at low cost, but also the number of teeth is reduced, and furthermore, the shrinkage in the rotational center direction can be achieved. It becomes the form which utilized the characteristic part of this invention which does not form the overhang part which a defect produces. However, of course, the non-circular gears 30 and 50 can be formed not only by resin molding but also by various materials and manufacturing methods, such as those cut and processed into metal.

This tooth curve is a tooth curve engraved with an ellipse on the pitch curve and has 4n + 2 teeth (n = 1, 2, 3, ...) and two grooves at both ends on the long axis { Two grooves between the teeth 34 and the teeth 35} and both ends of the short axis are teeth (for example, teeth of the teeth 31), and teeth 31 to 37 and 41 to 47 { In the case of the non-circular gear 50, the teeth 51-57, 61-67 are made into a basic curve. On the other hand, in Figure 2, n = 3, a total of 14 cases are illustrated. In the case where n is taken small or in the case of smaller gears, the flatness of the pitch curve may be reduced to be close to the circle. In addition, although the pitch curve is demonstrated here as an ellipse, the pitch curve of a non-circular gear is not limited to what is represented by the pitch curve ρ = a / (1-bcos2θ) of an oval gear, and is a single thing which satisfies a rolling contact condition. A closed curve or a closed curve that combines several types may be used.

Regarding the number of teeth, the number of teeth before considering the infill and the cut off, that is, the number of teeth in the original tooth curve, may be six or more (4n + 2) in consideration of the infill and the cut off, and will be described later. Considering the filling and cutting, the final number of teeth is 4n-2 pieces. In fact, the original tooth curve is assumed to be 14 or 18 teeth, and it is preferable to finally configure the number of teeth to be 10 or 14, respectively.

In addition, this basic tooth curve is a tooth curve having an interlocking surface as an involute curve and a non-engaging surface as a cycloid curve. Taking the third tooth 33 of the first non-circular gear 30 as an example, the engagement surface 33a will be an involute curve, and the non-engagement surface 33b will be a cycloid curve with the end 33c fitted. have. In this tooth curve, the tool pressure angle of the involute curve of each tooth is set by the lowering limit and the tip limit. On the other hand, the non-engaged surface is a cycloid curve, the tool pressure angle is zero, and the non-engaged surface on the outside of the pitch curve is an epicycloid generated when rolling outside the pitch curve. Nonengaged surfaces are hypocycloids that occur when rolling inside the pitch curve.

Then, the non-circular gears 30 and 50 are recessed parts including two grooves (for example, two grooves between the teeth 34 and the teeth 35) at both ends on the long axis based on the basic tooth curve described above. It is designed to have a shape filling the recess between two teeth (for example, teeth 34 and teeth 35) sandwiching the groove. In Fig. 2, for example, the recess between the tooth 34 and the tooth 35 is shown as a shape having a convex portion 39 filled with a curved line, which curve 39 is a circular arc with the recess corresponding to the inner wall of the casing. I assume that it is hot. At this time, the tooth curve is determined by the installation place of the non-circular gear in the casing and the size of the inner wall. For example, the engagement surface of the tooth | gear 34 and the tooth | gear 35 which are the base of the convex part 39 is designed to leave a tooth shape as it is.

In addition, the non-circular gears 30 and 50 are designed to have a shape in which the teeth including the teeth on both ends of the short axis (for example, the teeth on the teeth 31) are cut off based on the basic tooth curve. . In FIG. 2, the tooth (corresponding to the tooth 31) which cut | disconnects the tooth tip of the tooth 31, for example is cut off, and is shown as a shape which has the recessed part 38. As shown in FIG. Therefore, if the number of teeth of the basic tooth curve is 4n + 2 sheets, the number of teeth of the final tooth curve is 4n-2 sheets.

In addition, the non-circular gear 30 and the non-circular gear 50 include a convex portion 39 having a shape that fills a recess between two teeth (for example, the teeth 34 and the teeth 35), The recessed part 58 which has the shape which cut | disconnected the tooth | part (corresponding to the tooth | gear 51) in the circular gear 50 is comprised so that the recessed part 38 and the non-circular shape of the non-circular gear 30 may be similarly engaged. The convex portion 59 of the gear 50, the convex portion 49 of the non-circular gear 30 and the concave portion 68 of the non-circular gear 50, the concave portion 48 of the non-circular gear 30. ) And the convex portion 69 of the non-circular gear 50 are configured to mesh with each other.

On the other hand, the engagement here is not all caused by the contact between the centers of the concave portions and the convex portions, but the engagement of the convex portions 39 and the concave portions 58 is illustrated in Fig. 2B, for example. When the long diameter of the non-circular gear 30 and the short diameter of the non-circular gear 50 match, the convex portion 39 and the concave portion 58 do not contact each other, and the original teeth of the convex portion 39 are not in contact with each other. The apex of the interlocking surface of (35) is in contact with the interlocking surface of the fourteenth tooth 67 of the non-circular gear 50, rotates in the rotational direction of the arrow mark, and then the original tooth in the convex portion 39. The apex of the interlocking surface of (34) is rotated in contact with the interlocking surface of the second tooth 52 of the non-circular gear 50. Therefore, the pair of non-circular gears 30 and 50 shown in FIG. 2 cannot rotate the other gear by one rotation or more by the rotational force from the shaft of one gear. However, the pair of non-circular gears 30 and 50, like a volumetric flow meter, use a form in which a portion located outside of both gears is pressed by a flow force by a fluid to be measured, as shown in FIG. 2. Can be rotated in the rotational direction of the arrow mark, and the turning point is near the top (convex portion 39, etc.) in inertia relationship.

In addition, in other teeth, for example, the sixth tooth 36 of the non-circular gear 30 is taken as an example. As shown in Fig. 2A, the engagement surface 36a of the tooth 36 is formed. The non-round gear 50 of the thirteenth tooth 66 is in contact with the engaged teeth, and then the engaged teeth of the teeth 35 in the convex portion 39 are made of the non-round gear 50. 14 The tooth 67 is rotated in the direction of rotation of the arrow mark by being in contact with the engaging surface of the tooth.

3 to 6 are a series of configuration diagrams for explaining the points taken into consideration when designing the non-circular gear of FIG. 2, and in FIG. The figure shows a quarter of a circular gear. In the figure, L is tooth curve, La is interlocking, Lb is non-engaging, Lc is this end, P is pitch curve, R is radiation from the center of pitch curve, T is the curve connecting tooth ends, B is It is a curve which connected the bottom part of a tooth, and is shown using the same code | symbol as FIG.

The tooth curve L in FIG. 3 is a tooth curve engraved by the pitch curve P as an ellipse, and the number of teeth is 4n + 2 (14 sheets in this case), and when engaged, La is an involute curve, and the non-engaged teeth Lb is a cycloid. It is a tooth curve with a curve. This tooth curve L is wide in the overhang part in the area | region (shown with color) divided by the radiation R. As shown in FIG. The toothed curve L shown in Fig. 3 has a design in which both ends on the long axis and the two ends on the short axis are two grooves. With this design, the tool pressure angle can be set large enough to cause no dropping. Even if the teeth are tilted in the long axis direction, the overhang cannot be eliminated.

In resin molding or the like, defects occur in the overhang portion due to shrinkage in the rotational center direction, so that the design is advanced with two teeth (two ends on the long axis in this groove) so as not to form the overhang portion. That is, as shown by the tooth curve L of FIG. 4, a design in which both ends of the long axis are the two grooves and the two ends of the short axis are the two ends, and as shown in the order of the tooth curve L of FIGS. 4 and 5 in order. Similarly, each tooth is tilted in the major axis direction so as to reduce the overhang. At this time, when engaged, La uses the involute curve, but in order to reduce the change in the engagement pressure angle, the tool pressure angle is required to the lower limit and the engagement pressure angle is not negative. However, in the tooth curve L of FIG. 5, since the overhang is present as a tooth with the longest axis, La uses the involute curve similarly when engaged, but the tool pressure angle is lowered to reduce the change in the engagement pressure angle. And from the tip limit. On the other hand, when engaged, Lb uses a cycloid curve to favor the tool pressure angle setting of La. Here, the tooth with the highest inclination for eliminating the overhang portion is a tooth that is close to both ends of the long axis. Therefore, by making the two ends of the long axis into two grooves (concave), the tool pressure angle is large (to the maximum end limit) to prevent falling. Can be set.

That is, as shown by the tooth curve L of FIG. 6, since each tooth was inclined in the long axis direction until the overhang was completely removed, the tooth tip Lb {especially the teeth 34 of the teeth] was sharpened to the tip limit only by it alone. The tip of the tooth 34 is excessively sharp, so that the tip of the tooth 34 and the tip of the tooth 35 of FIG. 2 are connected to eliminate the sharpness. In consideration of the engagement of the convex portions 39 formed by connecting these teeth, the short diameter teeth are cut to form the concave portions 38. The curve T connecting the teeth of each tooth and the curve connecting the bottom of each tooth become a curve parallel to the pitch curve.

The above-described design, in which the tip of the tooth {the convex portion 39} is connected to the casing by a circular arc and one tooth is removed, and the tooth of one short diameter part is removed, has a large tooth module and reduces the number of teeth. Not only is it hardened, but also the lack of the sealing state of the top part by the tip is prevented, and the sealability of the top part is also improved. 4 to 6, the design having two grooves on the long axis in the basic tooth curve is effective for avoiding overhanging.

According to the non-circular gear according to the embodiment, there is little change in the engagement pressure angle, which is advantageous for setting the tool pressure angle on the engagement surface, and reduces the number of teeth without forming an overhang portion, or when installing in the casing. The sealing property with an inner wall can fully be ensured, and also the area | region in which a bearing | entrance enters can be secured even when it is axially fixed to a casing. Moreover, this non-circular gear is effective for resin molding because the tooth module is enlarged with respect to the whole, and it is solid and can be configured with a small number of teeth. In addition, the volumetric flowmeter with the non-circular gear as described above can be realized to be robust and high precision, and can be realized to be inexpensive when the non-circular gear is formed by resin.

FIG. 7 is a view showing a configuration example of a non-circular gear according to another embodiment of the present invention, and FIGS. 2A and 2B show engagement of a pair of non-circular gears according to their rotational positions. Figure is shown. In the figure, reference numeral 30 'denotes the first non-circular gear, 39' and 49 'denote the convex portion in the first non-circular gear, 50' denotes the second non-circular gear, and 59 'and 69' denote the second. It is a convex part in a non-circular gear, and the same code | symbol is attached | subjected to other parts similar to FIG. 2, and the description is abbreviate | omitted.

The non-circular gear of the embodiment illustrated in FIG. 7 is a convex portion (convex in FIG. 2) in the non-circular gear illustrated in FIGS. 2 to 6 and a volumetric flowmeter (see FIG. 1) provided with the gear. 39, 49, 59, 69), the shape of which is modified, and the description other than the deformation | transformation part also includes the effect, and abbreviate | omits.

The non-circular gears 30 'and 50' according to the present embodiment have the convex portions 39 ', 49' (59 ', 69') filled with curves in line with the inner wall of the casing, and further filled with curves. Is designed to be brought into contact with the bottom of the recesses 58, 68, 38, 48 formed by shaving the teeth in the non-circular gears 50 ', 30'. At this time, the tooth curve is determined by the installation place of the non-circular gear in the casing and the size of the inner wall. In Fig. 7, for example, the engagement surface of the teeth 34 and the teeth 35 on which the convex portion 39 'is based is designed as a curve in which the original teeth are deformed, but the convex portion ( The engagement surface of the tooth 34 and the tooth 35 as the basis of 39 ') may be designed to leave the tooth as it is. According to the non-circular gear according to the present embodiment, compared with the embodiment described with reference to Figs. 1 to 6, when it is installed in the volumetric flowmeter, the phenomenon of closing due to the engagement pressure angle is alleviated, thereby reducing the pressure loss. The measurement accuracy can be increased in accordance with the improvement of the sealability of the top portion.

According to the present invention, in the non-circular gear, the change in the engagement pressure angle is reduced, and it is advantageous to set the tool pressure angle on the engagement surface, and the number of teeth is reduced without forming an overhang portion, and the casing is installed in the casing. The sealing property with the inner wall can be secured sufficiently.

In addition, according to the volumetric flowmeter according to the present invention, since the non-circular gear is used, it is possible to measure the flow rate with high accuracy.

Claims (9)

A non-circular gear that must be installed in a pair in a casing, wherein the non-circular gear has 4n + 2 teeth (n is a natural number), two grooves on both ends on the long axis, two ends on the ends on the short axis, and the involute on the interlocking surfaces. It has a tooth curve with a curved and non-meshed surface as a cycloid curve. The tool pressure angle of the involute curve of each tooth in this tooth curve is set by the lowering limit and the leading limit, This non-circular gear fills in the recess between two teeth sandwiching the teeth, including teeth on both ends of the long axis, and cuts teeth including teeth on both ends of the short axis, based on the tooth curve. And a non-circular gear having a shape of 4n-2 teeth. The said non-circular gear is comprised so that the convex part which has the shape which filled the said recessed part, and the recessed part which has the shape which cut | disconnected the tooth in the non-circular gear like the said non-circular gear are comprised. Non-circular gear, characterized in that. 3. The toothed curve according to claim 1 or 2, wherein the tooth curve is determined by the installation place of the non-circular gear in the casing and the size of the inner wall, wherein the shape is a circular arc that fits the recess to the inner wall of the casing. Non-circular gear characterized by the filling. 3. The toothed curve according to claim 1 or 2, wherein the tooth curve is determined by the installation place of the non-circular gear in the casing and the size of the inner wall, and the shape is a curve in which the recess is fitted to the inner wall of the casing. A non-circular gear is made to fill, and this infill curve makes contact when it engages with the bottom of the recessed part which cut | disconnected the toothed part in the non-circular gear like the said non-circular gear. The non-circular gear according to any one of claims 1 to 4, wherein the tooth curve has 14 or 18 teeth and consequently 10 or 14 teeth, respectively. The non-circular gear according to any one of claims 1 to 5, wherein the pitch curve of the non-circular gear is a single closed curve that satisfies the rolling contact condition or a closed curve combining various types. The non-circular gear according to any one of claims 1 to 6, wherein the non-circular gear is formed of a resin. The non-circular gear according to any one of claims 1 to 7, wherein the casing is a metering chamber in a volumetric flowmeter. A volumetric flowmeter provided with a pair of non-circular gears as set forth in claim 8, wherein the pair of non-circular gears are provided in such a manner as to be engaged with a pair of rotors in the metering chamber, and the pair of rotors discharges the pump. A volumetric flow meter which measures the flow rate of a measurement fluid.