JPS5937365A - Pressure-force converter - Google Patents

Abstract

PURPOSE:To prevent mechanical contact friction between a piston and a cylinder under a working condition and to perform steady and highly sensitive pressure-force conversion, by forming a proper taper on the piston or cylinder. CONSTITUTION:Taper is formed on a cylinder 1 or a piston 2 such that a clearance 4 increases on the high pressure side 3a and decreases on the low pressure side 3b. In case of the piston 2 being positioned in the center of the cylinder 1, the pressure distribution in the clearance 4 is uniform at any point of a periphery, and the radial component, of a force exerted on the piston 2 becomes zero. In case of the piston 2 being moved in parallel and being brought to an eccentric state, the pressure distribution on the side 4a, where the clearance 4 decrease, is different from that on the side 4b where the clearance increases. The average of pressure exerted on the clearance 4a side increases and the average of pressure exerted on the clearance 4b side decreases. Namely, a force is exerted on the piston in the direction in which eccentricity decreases. This restoring force is in proportion to the magnitude of the eccentricity and the pressure difference between both end faces. The provision of tapered clearance causes a restoring force to be exerted on the piston so that the piston is maintained in a vertical state at the center of the cylinder, and prevents the piston from making mechanical contact with the cylinder.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention automatically stabilizes a sliding piston by using the differential pressure acting between both end surfaces of the piston, avoids mechanical contact friction with the cylinder, and achieves high precision. This is a mechanism to realize pressure/force conversion.

A piston commonly used as a pressure/force transducer.
It is said that a cylinder with a simple inner cylindrical shape is best. In this case, if the piston becomes eccentric or tilted within the cylinder, the restoring force does not work and the piston and cylinder come into mechanical contact. In this type of pressure/force transducer, the following measures are taken to avoid mechanical contact between the piston and cylinder during operation.

Therefore, there are structural limitations, and furthermore, the rotation must be driven by external force.

In view of the above, the present invention prevents mechanical contact friction between the piston and cylinder during operation by providing the piston or cylinder with an appropriate taper, and performs pressure/force conversion stably and with high sensitivity. .

Embodiments of the present invention will be described in detail below with reference to the drawings. In FIGS. 1 and 2, 1 is a cylinder, and 2 is a piston that is slidable inside the cylinder. A gap 4 is formed that communicates with the low pressure section 31 and the low pressure section 31 side.

-1- Taper the cylinder 1 or piston 2 so that the groove 4 is large on the high pressure side 3 days and becomes small on the low pressure side 31). FIG. 1 shows the case where the cylinder is tapered, and FIG. 2 shows the case where the piston is tapered.

Next, the action of the pressure/force conversion mechanism having 1-styl structural acid is explained as follows.
An example will be explained in which the cylinder shown in the figure has a taper.

FIGS. 3 and 4 show typical ways in which the posture of the piston is disturbed. 3 shows parallel movement, and FIG. 4 shows eccentricity due to inclination.3 In either case of eccentricity, a restoring force acts on the screw I/N to return to the original position shown in FIG. 1. To explain the principle, when the pressure medium flows from the high pressure side 3a to the low pressure side 31) through the gap 4, there is a pressure drop depending on the size of the gap 4. That is, the pressure distribution in the gap 4 is determined by the shape of the gap. The magnitude 1P1 of the pressure change P in a minute portion with the gap 4 is determined by the magnitude Δ of the gap in that portion and the volumetric flow rate V of the fluid flowing therein, and is expressed as 1P1oCV/Δ3. In other words, where the clearance is narrow, the pressure gradient is large, and where the clearance is wide, the pressure gradient is small.3 As shown in Figure 1, if the piston is at the center of the cylinder, what is the pressure distribution in the clearance 4? Circumference -1- is also uniform, and as a summation, the radial component of the force that the piston receives becomes zero. When the piston 2 moves in parallel and becomes eccentric as shown in FIG. 3, the pressure distribution will be different between the narrow side 4a and the wide side 4b of the gap 4. On the side of the gap 4a, the degree of taper increases, and the pressure gradient becomes steeper on the 31] side, and the pressure gradient on the high pressure side 3a
It becomes loose. On the other hand, on the side of the gap 41), the degree of taper decreases and the pressure gradient approaches uniformity.

As a result, the average pressure acting on the gap 4a side becomes higher,
The average pressure acting on the gap 4b side becomes lower.

In other words, the piston receives a force in a direction that reduces eccentricity. This restoring force is proportional to the magnitude of eccentricity and the differential pressure between the two end faces of the piston.

When the piston 2 is tilted, the shape of the gap 4 changes as shown in FIG. On the side of clearance 4a, the low pressure side 31)
The pressure gradient becomes thicker near j, and the pressure becomes higher.This change meter becomes larger near the low pressure side 31].On the other hand, on the gap 4b side, the pressure gradient approaches . Low (
Become. This amount of change is also larger in the portion closer to the low pressure side 31]. As a result, the force that the screw receives is the sum of the pressures that it receives in the gap 4, including a translational force in the direction of the gap 4b and a rotational force that returns the inclination to perpendicular. The latter force is a restoring force against tilt eccentricity. This restoring force is proportional to the magnitude of eccentricity and the differential pressure between the ends of the piston.

Below 1-. As explained, by providing the tapered gap, a restoring force acts on the piston to maintain it perpendicular to the center of the cylinder, and mechanical contact between the piston and the cylinder is prevented. The principle regarding this restoring force is not shown in FIG. The same holds true when the piston has a taper.

The magnitude of the restoring force is proportional to the surface area S [:=4] of the fitting part of the screw cylinder. Furthermore, if the size of gap 4 is expressed as Δa for the narrower one and Δb for the wider one, the restoring force is
While Δb/Δa takes a value of 2 to 5, it increases as it becomes larger, and reaches a nearly maximum value at Δb/Δa:5. Incidentally, the magnitude of the restoring force is, when Δb/Δa=5 and the amount of eccentricity is half of the maximum value, the translational force F = 1.0X 10''S・
ΔP (N), rotational force M-6×1OS・ΔP-L [N
−m]. Here, S is the area of the fitting part between the piston and cylinder, ΔP is the differential pressure between both end surfaces of the piston,
L is the length of the fitting portion between the piston and cylinder.

As described in detail below, according to the pressure/force conversion mechanism according to the present invention, the piston or cylinder is tapered, and the pressure distribution changes in response to changes in the posture of the piston due to the action of the pressure medium flowing through the gap. is generated in the gap,
This becomes the restoring force that returns the piston to its original eccentricity. Therefore, it is possible to reliably prevent friction and seizure between the piston and cylinder, and there is no need to use special lubricants. - Not only can it be applied to cylinder pressure gauges, but it is also extremely effective as a variety of 1-1 pressure/force converters.

[Brief explanation of the drawing]

1 and 2 are longitudinal sectional views showing two embodiments of the present invention, and FIGS. 3 and 4 show changes in the shape of the clearance due to two typical eccentricities of the piston. Longitudinal cross-sectional view. 1...Cylinder, 2...Piston 3a...High pressure part side, 31]...Low pressure part side 4...Gap, 4a...Gap deformed due to eccentricity 4b...
Gap 7 deformed due to eccentricity - Figure 1 Figure 2 Rinta Figure 3 Figure 4

Claims (1)

[Claims] 1. A pressure/force converter characterized in that in a slidable piston/cylinder system, the piston or cylinder is tapered so that the gap between the piston and the cylinder becomes larger on the high pressure side.