JPH0213934Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Technical Field] This invention relates to a shaft structure suitable for positive displacement flowmeters of various structures, particularly for small positive displacement flowmeters.

[Prior art]

Conventionally, generally known positive displacement flowmeters have a rotor disposed inside the measuring chamber, and the rotor shaft is fitted into a through hole drilled in the center axis of the rotor, allowing the rotor shaft to rotate freely. There is a structure in which the rotor is supported, and a rotor shaft having a diameter corresponding to the size of the rotor is fixed and used in practical use. However, such an integral configuration of the rotor and rotor shaft does not cause any particular problems in the case of a normal-sized positive displacement flowmeter that can ensure centering accuracy during machining, but it does not pose any particular problem, especially at low flow rates. In the case of a so-called small positive displacement flowmeter that requires the following, it is necessary to reduce the diameter of the rotor shaft to reduce frictional torque consumption. In order to reduce the diameter of the rotor shaft, a structure in which a part of the shaft is made thinner is known. It is difficult to ensure centering accuracy. As a result, smooth rotation of the rotor may not be obtained. Alternatively, in order to use a thin rotor shaft, the rotor hole diameter must also be made thin. In this case as well, it is difficult to align the center of the hole with the central axis of the rotor. In addition, precision machining of the outer surface of the rotor generally has a large effect on preventing leakage of the fluid to be measured in the measuring chamber and improving measurement accuracy and durability. It is no exaggeration to say that this depends on the small diameter of the child shaft and the precision machining of the rotor itself. Furthermore, when considering the man-hours for the rotor shaft, the latter requires less man-hours between the stepped shape and the straight shape, and in the case of a straight shaft, rolling machining is possible, so the surface hardness is lower. This increases the durability of the shaft.

By the way, in precision machining of the outer surface of the rotor, especially when machining both top sides, the larger the circular hole that the rotor shaft passes through, the more difficult it is to insert a machining jig such as a lathe into the circular hole. The diameter of the shaft is also increased, which reduces the effects of center runout during rotation and deflection due to cutting resistance, increasing machining accuracy.

However, in the past, if the circular hole of the rotor that the rotor shaft passes through is small in diameter, the shaft diameter of the processing jig will also be small, making it impossible to obtain a high-precision rotor without the above-mentioned adverse effects. It was hot.

[Summary of the idea]

This idea was made by focusing on the points mentioned above, and the circular hole through which the rotor shaft of the rotor can be inserted has a sufficiently large diameter to facilitate the machining of the rotor. In order to reduce friction during rotation by forming the diameter sufficiently small, an elastic bushing with a diameter slightly larger than the circular hole of the rotor is inserted through the small diameter rotor shaft in the center. Another object of the present invention is to provide a shaft structure for a positive displacement flowmeter in which the rotor shaft and the rotor are integrally fitted.

〔Example〕

An embodiment of this invention will be described below with reference to the drawings.

1 is a pair of rotors such as an elliptical gear rotor (trademark OVAL) or a Roots type rotor, which is rotatably disposed in the measuring chamber 2 of a positive displacement flowmeter a;
A circular hole 5 is formed in the direction of the central axis of the rotor 1 for inserting and fixing the rotor shaft 4;
An elastic bushing is shown that is fitted and fixed in the circular hole 3 through the center of the elastic bushing. Constructed to form equal surfaces.

By the way, the diameter of the circular hole 3 of the rotor 1 is bored sufficiently larger than that of the rotor shaft 4, and the shaft of a processing jig such as a lathe is inserted into the circular hole 3 having a large diameter. The rotor 1 can be securely fixed. In particular, when processing the outer surface of the rotor 1, since the shaft of the processing jig is thick, there is no center runout during processing, and proper processing can be performed. In addition, the rotor shaft 4
can be securely fixed in the circular hole 3 of the rotor 1 by using an elastic bushing 5 having a diameter slightly larger than the diameter of the circular hole 3. Furthermore, this elastic bushing 5 can be made of materials having desired elasticity such as various metals and synthetic resins.

An example of a case where the rotor 1 is small is as follows.
The diameter of the circular hole 3 is 5 mmφ, and the diameter of the rotor shaft 4 is 1 mmφ. can be set freely.

It goes without saying that the rotor shaft 4 is rotatably supported by a bearing (not shown).

[Effect of idea]

According to this invention, the rotor shaft can be formed with a sufficiently small diameter for the rotor, thereby reducing frictional resistance during rotation as much as possible, and the rotor shaft can be inserted and fixed. The circular hole of the rotor has a sufficiently large diameter, so that the rotor can be easily machined without centering.

Furthermore, according to this invention, the small-diameter rotor shaft and the large-diameter circular hole are firmly fixed using an elastic bushing, so the rotor can be rotated smoothly. has. Furthermore, since the number of processing steps is small, mass production is easy and costs can be gradually reduced.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing an embodiment of the shaft structure of a positive displacement flowmeter according to the invention, and FIG. 2 is an enlarged sectional view of the rotor of the same. 1...Rotor, 2...Measuring chamber, 3...Circular hole, 3
a... Opening surface, 4... Rotor shaft, 5... Elastic body bushing, 5a... Outer end, a... Positive displacement flow meter.

Claims (1)

[Scope of utility model registration request] A positive displacement flowmeter is equipped with a pair of rotors that are supported in a measuring chamber and rotate in proportion to the flow rate.
A rotor with a circular hole bored on the shaft, a small-diameter cylindrical rotor shaft, and an elastic resin cylindrical bush with an outer diameter larger than the circular hole and an inner diameter slightly smaller than the rotor shaft. A shaft structure of a positive displacement flowmeter, characterized in that a bushing through which a rotor shaft is inserted is elastically fitted into a circular hole.