JPS63652B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a variable speed fluid coupling used, for example, as a fluid transmission for a power plant.

[Background of the invention]

In this type of conventional variable speed fluid coupling, there may be discontinuities in the output shaft rotational speed as shown in FIG.

That is, when the radial position of the tip of the scoop tube is at point A, a discontinuous point (this is called a skip phenomenon) occurs where the output shaft rotational speed changes rapidly in response to a slight movement of the scoop tube position. At present, it is very difficult to completely eliminate these discontinuous points, and control has been performed to avoid and use the discontinuous points.

Therefore, there were problems in terms of reliability and controllability.

[Purpose of the invention]

An object of the present invention is to provide a variable speed fluid coupling that improves reliability and controllability by preventing the occurrence of discontinuities.

[Summary of the invention]

According to the inventor's model experiments, the discontinuity point occurs at a constant radial position of the scoop pipe and regardless of the magnitude of the load, and is not affected even if the impeller shape is changed, It has been revealed that this occurs due to a sudden change in the flow of rotating fluid within the tube chamber. The present invention was made in consideration of the inventor's experimental results that the cause of the discontinuity point is due to a sudden change in the flow inside the scoop tube chamber.
A feature is that the cross-sectional shape of the tip of the scoop tube along the rotating fluid surface is formed such that the width of both side wall portions of the scoop tube decreases from the upstream side to the downstream side.

[Embodiments of the invention]

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

FIG. 2 is a schematic diagram for explaining the entire variable speed fluid coupling. Rotation of the impeller impeller 2 connected to the input shaft 1 applies centrifugal force to the hydraulic oil, and this hydraulic oil flows into the runner impeller 3. Power is transmitted to the output shaft 4. At this time, the output shaft rotational speed is steplessly controlled by moving the scoop tube 6 provided in the scoop tube chamber 5 and having a shape to be described later in the radial direction to scoop up the rotating fluid 7 in the scoop tube chamber 5. .

By the way, the inventor's experiments have shown that the discontinuity point in the output shaft rotational speed occurs when the flows of the two types of rotating fluids 7 existing in the scoop tube chamber 5 transition from one flow to the other flow. This became clear from the results.

The experimental results will be explained below.

There are two types of flows of the rotating fluid 7 in the scoop tube chamber 5 as shown in FIGS. 3 and 4, and one of the flow states occurs depending on the radial position range of the scoop tube 6. Therefore, a sudden change in flow occurs at the scoop pipe position where one flow state transitions to the other flow state.

FIG. 3 shows one flow state in the scoop tube 6 when viewed from the side. The external flow of the scoop tube 6 adheres to the scoop tube wall surface, and such a flow is called an attached flow. In addition, FIG. 4 shows the other flow state in the scoop tube 6 seen from the side as in FIG. Air enters from the atmosphere to form a free streamline C, and this flow state is called a separated flow. The adhesion flow and separation flow become adhering flow in a radial position range smaller than the scoop pipe position where the discontinuity point occurs, and become a separation flow state in a radial position range larger than the scoop pipe position where the discontinuity point occurs. Become.

Figure 5 shows a conventional scoop tube with an egg-shaped cross section in which discontinuities occur. The width b of both side wall portions of the scoop pipe increases along the direction Y, reaches a maximum value, and then decreases.

FIG. 6 shows the pressure distribution on the side wall of the scoop tube having an egg-shaped cross section, and the pressure coefficient Cp shown in FIG. 6 is expressed by the following equation.

Cp=(P-Po)/1/2ρU ^2Where , P: Pressure on the side wall surface, Po: Atmospheric pressure, ρ: Fluid density, U: Uniform flow velocity at the tip of the scoop tube.

As is clear from Fig. 6, the pressure P becomes the minimum near the point D where the width b is maximum.
The pressure drops below Po and becomes a negative pressure state. Since the flow at the tip of the scoop tube is in contact with the atmosphere through the free surface, when the pressure P reaches a certain negative pressure state, air enters from the free surface, and the flow at the tip of the scoop tube and the side wall as shown in Figure 4. A free streamline C is formed from the section, and the flow condition in the scoop tube section changes significantly. FIG. 7 shows the flow state in an oval-shaped scoop tube in cross section, and shows the free streamline C from the position where the width b is maximum.
is formed.

The present invention was invented with a focus on eliminating the negative pressure state on the external side wall surface of the scoop tube by forming the scoop tube 6 into a special shape.The shape of the scoop tube 6 will be described below. As a result of experiments, it was found that the desired purpose could be achieved by defining the shape as follows.

8 and 9 are enlarged views showing essential parts of the scoop pipe 6 in the variable speed fluid coupling of the present invention, and the scoop pipe 6 is composed of a tip end 8 and a discharge pipe 9. A rake 10 into which the rotating fluid 7 flows is formed on the top surface of the tip 8, and a bottom 11 in contact with the rotating fluid 7 is formed to form a certain angle with the rotating fluid 7.

Further, the cross-sectional shape of the tip portion 8 along the liquid surface of the rotating fluid 7 is such that the width b of both side walls 12 of the scoop tube decreases smoothly from the scoop opening 10 to the rear end 13, as shown in FIG. Note that the cross-sectional shape of the tip portion 8 is formed so that the inflow position of the rotating fluid 7 into the scoop opening 10 changes depending on the radial position of the scoop pipe, so that the cross-sectional shape is maintained within the above-mentioned radial position range.

By forming the scoop tube 6 in this way, the pressure distribution on the side wall of the scoop tube tip 8 becomes the first.
As shown in Figure 1, the pressure P does not become a negative pressure state.

Therefore, as shown in FIG. 12, the rotating fluid 7 separates from the position of the rake opening 10, and the flow is always separated in all the radial position ranges of the scoop pipe without transitioning from adhering flow to separated flow as in the conventional case. Since the state can be maintained, the occurrence of discontinuous points can be prevented.

〔Effect of the invention〕

In the variable speed fluid coupling of the present invention, the cross-sectional shape of the tip of the scoop pipe along the rotating fluid surface is formed such that the width of both side walls decreases from the upstream side to the downstream side, so that the output shaft rotates. Since discontinuous points in the number can be prevented, reliability and controllability can be significantly improved.

[Brief explanation of the drawing]

Figure 1 is a scoop pipe position-output shaft rotational speed characteristic diagram to explain the discontinuity point, Figure 2 is a schematic sectional view to explain the overall configuration of the variable speed fluid coupling, and Figure 3
The figure is a diagram for explaining the adhesion flow at the tip of the scoop tube, FIG. 4 is a diagram for explaining the separation flow at the tip of the scoop tube, and FIG. 5 is a diagram for explaining the conventional tip of the scoop tube. , Figure 6 shows the pressure distribution at the tip of the scoop tube in the conventional variable speed fluid coupling shown in Figure 5, and Figure 7 shows the separation flow at the tip of the scoop tube in the conventional scoop tube shown in Figure 5. Figures 8 to 10 are diagrams for explaining the scoop pipe in the variable speed fluid coupling of the present invention, where Figure 8 is a side view, Figure 9 is a plan view, and Figure 10 is a side view. FIG. 8 is a sectional view taken along the line E--E, FIG. 11 is a diagram showing the pressure distribution at the tip of the scoop tube in the variable speed fluid coupling of the present invention, and FIG. 12 is a scoop tube in the variable speed fluid coupling of the present invention. It is a figure for explaining the separation flow of a tip part. 6... scoop pipe, 7... rotating fluid, 8... scoop tube tip, 10... scoop mouth, 12... side wall part.

Claims (1)

[Claims] 1. In a variable speed fluid coupling that controls the output shaft rotation speed by adjusting the radial position of the scoop pipe and adjusting the filling amount of working fluid in the impeller, 1. A variable speed fluid coupling characterized in that the cross-sectional shape of the scoop pipe is formed such that the width of both side wall portions of the scoop pipe decreases from the upstream side to the downstream side.