JP3150727B2 - Small flow sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a small flow sensor.

[0002]

2. Description of the Related Art Small flow sensors using an impeller are widely used for detecting flow rates in shower toilets, water purifiers, instantaneous water heaters and the like.

In the flow sensor described in Japanese Patent Application Laid-Open No. 60-228923, the entire impeller is integrally formed of a synthetic resin material in which particles of a rare-earth magnetic material are dispersed, and the magnetism of the impeller is detected by a detection element. are doing. And it has the structure of the both ends bearing system which has a shaft in both ends of an impeller. Also,
The diameter (outer diameter) of the impeller was smaller than the diameter because the main body case was an integral structure.

[0004] The flow rate detector described in Japanese Patent Application Laid-Open No. 57-18818 is provided with an impeller having an outer diameter slightly larger than the caliber, and both ends of the main body are inserted into the main body. , A connecting O-ring was provided between the body and both connecting pipes.
This prior art also has a double-ended bearing structure.

[0005]

In the above prior art,
Due to the structure of the double-ended bearing system, there is a problem that a considerably accurate dimensional accuracy is required for downsizing, and it is difficult to mold the main body or the like into a plastic, thereby making it difficult to reduce the cost. In addition, in the double-ended bearing system, there is a problem that since the displacement of the shaft center greatly affects the performance, it is extremely difficult to assemble and assemble the shaft center.

The former of the above prior arts has a problem that the impeller has a heavy underwater weight, and the shafts and bearings are remarkably abraded. In addition, in order to simplify the structure of this type of small flow sensor, if the outer diameter of the impeller is made smaller than the diameter of the impeller by using an integrally-structured main body case as in the former of the prior art, the impeller The rotational moment of the vehicle becomes smaller as the pipe diameter becomes smaller, and the measurement error increases. In addition, when the diameter becomes small, the flow velocity becomes high to obtain the same flow rate, and the rotation speed of the impeller increases. And since the impeller rotation speed is limited from the point of durability,
As a result, the weighing range is reduced.

The latter of the above prior arts requires an O-ring for sealing between the main body (body) and both connecting pipes, and the main body case also comprises three parts between the main body (body) and both connections. However, there is a problem that the structure is complicated and the cost is high.

Accordingly, an object of the present invention is to provide a small-sized flow sensor capable of solving the above-mentioned problems of the prior art.

[0009]

In order to achieve the above object, a small flow sensor according to the present invention comprises a cylindrical portion forming a flow path, a main body case (1) made of reinforced plastics and a sensor case (5). ), One end of which is fixed with a thin stainless steel shaft (2), the whole is formed of wear-resistant plastic, and a small rod-shaped rare earth magnet (4) is embedded at the tip of the impeller. (3) is rotatably fitted to the fixed shaft (2), and the sensor case (5) is provided with a detection element (6) close to the magnet (4). The impeller (3) was housed in the sensor case (5), and the two cases (1) and (5) were joined in a watertight manner to be integrated.

[0010]

When the fluid flows through the flow path, the impeller rotates, and the rotation is detected as an electric signal by the magnet and the detecting element. The impeller rotates while being supported by a fixed shaft.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the drawings, reference numeral 1 denotes a cylindrical main body case forming a flow path, which is formed of reinforced plastic. Reference numeral 1a denotes a rectifying plate for fixing a shaft 2 to be described later and rectifying the fluid, and is formed integrally with the main body case 1 together with a connection taper screw 1b formed on the outer periphery of the right end of the main body case 1.

Reference numeral 2 denotes a shaft made of a thin and strong stainless steel rod, which is inserted into and fixed to the current plate 1a coaxially with the axis of the main body case 1. The tip (left end) of the fixed shaft 2 protrudes and extends leftward from the current plate 1a.

Reference numeral 3 denotes an axial-flow type impeller made of plastic having high wear resistance, and bearings 3a and 5 fitted to the shaft 2 are provided.
The blades 3b are integrally formed. In addition, feather 3
b is twisted to rotate with the fluid flow.

Reference numeral 4 denotes a small rod-shaped rare earth magnet.
It is embedded near the tip (left end). The magnet 4 is embedded in the center of the left end of the impeller 3, and is arranged so that no rotational force is generated due to the imbalance of the weight of the magnet.

The impeller 3 in which the magnet 4 is embedded has its bearing 3
a is rotatably fitted to a fixed thin shaft 2. Reference numeral 5 denotes a cylindrical sensor case for forming a flow path, which is formed of reinforced plastic. Similar to the case of the main body case 1, a rectifying plate 5a for rectifying the fluid and a taper screw 5b for connection on the outer periphery of the left end are integrally formed. Have been.

Reference numeral 6 denotes a detection element housed in the sensor case 6, which detects the rotation of the magnet 4 and converts it into an electric signal. In the sensor case 5, the cylindrical portion forming the flow path is disposed coaxially with the cylindrical portion of the main body case 1, and the two fitting portions 5c and 1c are fitted to each other. Bonded or welded in a watertight manner.

Reference numeral 7 denotes a fluid inlet, and reference numeral 8 denotes an outlet. When the fluid flows from the inflow port 7 to the outflow port 8, the impeller 3 rotates, and the detection element 6 detects the rotation.

The inner diameter of the main body case 1 for storing the blades 3b of the impeller 3 is larger than the diameter of the right end of the main body case 1 and the left end of the sensor case 5.

The outer diameter of the blade 3b is larger than the diameter, and is set to be 1.1 to 1.5 times the diameter. Since the rotation moment M of the impeller is determined by the product of the blade rotation force F and the distance L from the shaft to the point of application, if the rotation inhibition force is equal and the blade rotation force is the same, the impeller having an outer diameter larger than the diameter is used. By using, it is possible to reduce the weight even to a micro flow area (a region where the rotational force is small), and as a result, the light weight range is expanded. Even if the diameter becomes smaller, the impeller does not rotate at high speed in a large basin, and a stable and wide measuring range (1:20 to 1:30)
Could be obtained.

Further, the entire impeller was formed of wear-resistant plastic, and a small rod-shaped rare earth magnet was embedded in the center of the tip to reduce the weight in water as a whole. And fixed shaft 2
Is made of a metal as thin as possible, the peripheral speed of the bearing 3a fitted and slid on the metal is reduced, so-called PV value is reduced, and wear resistance is improved. By the way, 10 at 3000 rpm
After passing through 00H, there was no change in performance.

In the embodiment, the fluid flowing in from the left inlet 7 flows out from the right outlet 8. However, since the shape of the flow straightening plate and the flow path are the same as those on the left and right sides, The same performance is obtained irrespective of the flow direction, and the flow direction is not limited.

[0022]

As described above, the small flow sensor of the present invention is constructed as described above, so that the bearing is less worn, can withstand long-time use, has a simple structure, and most parts can be manufactured by plastic molding. Since it is joined in a watertight manner only by assembling, it can be manufactured at low cost.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an embodiment of the present invention, and is an AA sectional view of FIG.

FIG. 2 is a side view of the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main body case 2 axis 3 Impeller 4 Magnet 5 Sensor case 6 Detection element

Claims (1)

(57) [Claims] 1. A tubular part forming a flow path is constituted by a main body case (1) made of reinforced plastics and a sensor case (5), and a thin stainless steel shaft (2) is fixed to one of them. Then, the whole is made of wear-resistant plastic, and a small bar-shaped rare earth magnet (4)
An impeller (3) embedded with the shaft is rotatably fitted to the fixed shaft (2), and a detection element (6) is provided in the sensor case (5) near the magnet (4). A small flow sensor in which an impeller (3) is housed in a case (1) and a sensor case (5) and both cases (1) and (5) are joined in a watertight manner.