JPH01267384A - Screw rotor having beveled tooth - Google Patents

Abstract

PURPOSE:To improve the efficiency of a machine, by making gradually small the outer diameter of at least one of a pair of two screw rotors, while enlarging gradually the tooth bottom diameter of the other rotor, and providing each tooth of the rotor as a beveled tooth the height of which is made smaller gradually. CONSTITUTION:In a screw fluid machine which is formed by accomodating inside a casing 6 a pair of screw rotor 1a, 1b rotated is synchronism through synchronous gears 2a, 2b in the condition engaged each other while the total of the outer diameter of one side rotor 1a or 1b and the tooth bottom diameter of the other rotor 1b or 1a is kept nearly a constant value in the vertical section of every shaft the outer diameter of at least one of two rotors 1a, 1b is gradually formed smaller in the rotary shaft direction. An simultaneously, the tooth bottom diameter of the other rotor is gradually enlarged in the rotary shaft direction. Thereby, a beveled tooth is formed with its height gradually reduced, so that operation of high efficiency can be carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a screw type fluid machine such as a screw vacuum pump or a screw compressor, and particularly to a screw rotor that is easy to manufacture and has high efficiency.

[Conventional technology]

In screw fluid machines such as conventional screw compressors and screw vacuum pumps, the length of the screw rotor is often about the same as or shorter than the lead, so the working chamber is at the highest pressure during operation, and the working chamber is at the highest pressure when suction is completed. A low-pressure working chamber will soon appear.

Adjacent.

In an oil-free screw fluid machine, a minute gap is provided to prevent the screw rotors from coming into contact with each other, so fluid leaks from this gap. The amount of fluid leaking increases as the pressure difference increases, so in the conventional screw fluid machine mentioned above, there is a large amount of leakage from the high pressure working chamber to the low pressure working chamber, which causes problems such as heat generation and a decrease in efficiency. there were.

As a means to solve this problem, there is a method in which the length of the screw rotor is made sufficiently longer than the lead, and each tooth groove is formed over 360 degrees Celsius or more around the rotation axis.

However, the use of the above means causes the following drawbacks.

As the screw rotor rotates during operation, the working chamber, which is a spiral space closed by the tooth grooves of the screw rotor, the inner surface of the casing, and the tips of the teeth of the mating screw rotor, moves from the suction port side to the discharge port side. However, although the working chamber is described here as a closed space, it actually depends on a minute gap' for the reasons mentioned above.

When the suction of fluid from the suction port is completed and the working chamber is closed, the open working chamber remains at a constant volume and moves for a while. When the casing reaches the end on the discharge side, the end surface of the casing becomes one wall of the working chamber, and the volume begins to be reduced, that is, compressed. Then, the pressure is rapidly increased within a short period of one revolution of the screw rotor to complete compression.

Rapidly increasing the pressure means that the pressure difference between adjacent working chambers becomes larger, and from the minute gap between the two screw rotors and between the screw rotor and the casing mentioned earlier. The amount of fluid leaking increases.

As a countermeasure against this increase in leakage amount, there is a method of gradually reducing the volume of the working chamber after suction is completed and the working chamber is closed to avoid sudden compression.1 Conventional techniques for gradually reducing the volume of the working chamber include, for example. Some of these are disclosed in Japanese Patent Publication No. 38-15285 and Japanese Patent Publication No. 59-36116.

[Problem to be solved by the invention]

The prior art described above does not take into consideration the design and manufacturing method of the screw rotor and the method of manufacturing the casing, and there are problems in manufacturing.

The screw rotor described in this patent has few surfaces parallel or perpendicular to the axis of rotation.

Furthermore, since the rotation axis and the rotation axis of the mating screw rotor are not parallel, the mathematical formula for geometrically expressing the locus of the tooth surface due to rotation becomes complicated.

In addition, the gears that synchronize the rotation of both rotors require bevel gears, and it is difficult to achieve the precision of the gears.When designing the tooth profile of the screw rotors that rotate in mesh, it is important to avoid interference with the mating teeth or the creation of tooth surfaces. Since complex geometrical calculations such as these are essential, there is a problem in that these things make designing the tooth profile difficult.

For the same reason, it is extremely difficult to machine the screw rotor with high precision using conventional machine tools, and it is also difficult to machine the casing so that the two rotating axes intersect with high precision, which is a manufacturing problem. was there.

In addition, other prior art techniques solve the problem of difficulty in design and manufacturing in the above-mentioned known examples.

However, the screw fluid machine according to this patent has a working chamber whose volume gradually decreases as the screw rotor rotates, and a working chamber whose volume increases.

This working chamber is unnecessary, which increases the size of the entire machine and consumes energy, which reduces efficiency.

An object of the present invention is to realize an efficient screw rotor that is easy to design and manufacture.

[Means to solve the problem]

The above purpose is to make the rotational axes of the two rotors parallel, so that the sum of the outer diameter of one rotor and the root diameter of the other rotor remains approximately constant no matter where the cross section perpendicular to the axis is taken. Gradually reduce the outer diameter of at least one of the screw rotors in the direction of the rotation axis, and at the same time gradually increase the tooth bottom diameter of the mating rotor in the direction of the rotation axis, making the teeth of the screw rotor gradient teeth with gradually lower tooth heights. This is achieved by

[Effect]

- When a pair of screw rotors are meshed and assembled into a casing, a space surrounded by the rotor and the casing, that is, a working chamber is formed.Since the screw rotor according to the present invention has sloped teeth, the volume of this working chamber is gradually decreases from one end to the other.

When this screw rotor is used in a compressor or a t2 vacuum pump, one end will be the suction side and the other end will be the discharge side, so each rotor end will be temporarily referred to as such. Then, the working chamber volume gradually decreases from the suction side to the discharge side.

When the two screw rotors are rotated synchronously, the working chamber moves from the suction side to the discharge side.

As for one working chamber, if we follow the passage of time 0 when the volume gradually decreases and moves, as soon as the suction process in which fluid is sucked into the working chamber ends and the working chamber is closed, the working chamber Volume reduction begins. Furthermore, the volume of the working chamber continues to shrink, gradually compressing the fluid trapped inside. Then, at the same time or before or after the working chamber reaches the discharge end surface, the discharge port is opened and the compressed fluid is discharged.

Since the fluid is compressed continuously and gradually from suction to discharge, the pressure difference between adjacent working chambers is small. Therefore, the amount of fluid leaking from minute gaps between screw rotors or between the screw rotor and casing is small. Therefore, the efficiency of screw fluid machines can be improved by using this screw rotor.

〔Example〕

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

FIG. 1 is a side view of a screw rotor that best represents the features of the present invention, and FIG. 2 is a cross-sectional view of the screw rotor shown in FIG. 1, including its rotation axis.

In these figures, the two rotors mesh with each other with a small gap. The teeth of the two rotors have almost the same shape, and only the twisting direction is reversed. When this set of rotors is used in a compressor or a vacuum pump, the left end of the toothed portion of the screw rotor in the figure is the suction side, and the right end is the discharge side. The outer diameters of both screw rotors decrease linearly from the suction side to the discharge side, and either rotor is inscribed in a conical hole. The two rotors mesh with each other by increasing the bottom diameter of one surface at the same rate as the outer diameter from the suction side to the discharge side.

The working chamber is formed by dividing a spiral groove of a screw rotor covered by a casing into several chambers by teeth of a mating screw rotor. The volume of one working chamber decreases toward the discharge side as the tooth height decreases in proportion to the difference between the outer diameter and the tooth bottom diameter.

When the two rotors are rotated synchronously, one working chamber decreases in volume while moving from the suction side to the discharge side. Therefore, it is possible to perform so-called internal compression in which the confined fluid is compressed while being transferred from the suction side to the discharge side, thereby improving efficiency.

In addition, this screw rotor is suitable for lathe processing, has a uniform lead, and has a simple tapered outer diameter. The advancing and retracting surfaces of the teeth are also perpendicular to the axis of rotation. Therefore, it has the advantage that it can be manufactured at low cost since no special cutting tools or machine tools are required.

The tooth profile of this example causes slight interference, so
A small gap must be provided between the two screw rotors, and if fluid leaks from this gap, efficiency will decrease.In this screw rotor with sloped teeth, the amount of interference is large on the suction side where the tooth height is high. Since the amount of interference is small on the discharge side where the tooth height is low, the gap can be made smaller on the discharge side than on the suction side in accordance with the amount of interference. For the same gap and pressure difference, the higher the absolute pressure, the more leakage will occur.In the screw rotor of this embodiment, the gap can be made smaller on the discharge side where pressure is high and leakage is likely to occur, so leakage can be kept to a minimum.

FIG. 3 is a sectional view of a screw fluid machine using the screw rotor of the embodiment shown in FIG.

A pair of screw rotors 1a and 1b are attached inside the casing 6 in a meshed state.

In order to rotate the two screw rotors synchronously, synchronous gears 2a and 2b are attached to each rotating shaft. Further, power is input by rotating the power input shaft 3. When this fluid machine is used as a compressor or a vacuum pump, fluid is sucked into the working chamber through the suction port 4 and discharged from the discharge port 5 in the form of internal compression.

FIG. 4 shows another embodiment of the present invention, which is an example of a vacuum pump in which a motor is incorporated inside a screw rotor.

Screw rotors ila and l are installed inside the casing 16.
It is installed with the lbs engaged. Synchronous gears 12a and 12b are attached to the lower end of each screw rotor to rotate the two screw rotors synchronously. Further, an outer motor having a stator 13a on the inside and a rotor 13b on the outside is provided inside the screw rotor lla.

The fluid enters the inside of the vacuum pump through the suction port 14, is sucked into the working chamber, is internally compressed, and is discharged from the discharge port 15.

In this example, the rotating shaft does not protrude from the suction port side of the screw rotor, so lubricating oil used for bearings, synchronous gears, etc. is not needed on the suction port side, so the lubricating oil flows back from the vacuum pump and contaminates the vacuum. There is no need to worry about doing so.

Furthermore, since the bearings that support the screw rotor are located near both ends of the screw rotor, they are more rigid than a single cantilever structure and are resistant to vibration and load fluctuations.

By installing a motor inside the further screw rotor,
The entire vacuum pump can be downsized. If the motor inside screw rotor lla alone is insufficient in output, a motor is also installed inside screw rotor llb, and 2
It can also be driven by two motors.

FIG. 5 is a sectional view of still another embodiment of the present invention. In this embodiment, the change in tooth height is made exponential in order to keep the compression ratio per revolution constant in internal compression. .

When the screw rotors 21a and 21b of this embodiment are applied to a compressor or a vacuum pump, the left end is the suction side,
The right end will be the discharge side. Near the discharge side, where pressure is high and leakage from gaps is likely to increase, the pressure ratio between adjacent working chambers is small, reducing leakage and improving efficiency.

FIG. 6 is a sectional view of still another embodiment of the present invention.

The outer diameter of one of the screw rotors 31a and 31b (31a in this example) of the present embodiment is constant, and the tooth root diameter gradually increases.

The other screw rotor (31b in this example) is.

The outer diameter gradually decreases and the root diameter remains constant.

In the embodiment shown in FIG.
It is necessary to machine two partially overlapping conical holes into which the two screw rotors la and lb are inserted, but in this example, since the outer diameter of one screw rotor 31a is constant, the two conical holes drilled in the casing are The holes will be conical and cylindrical. Therefore, there is an advantage that alignment of the two holes in the axial direction is not necessary, and machining is easy.

〔Effect of the invention〕

According to the present invention, internal compression is possible in which the volume of the working chamber is gradually reduced while moving one working chamber inside the screw fluid machine.

Therefore, the pressure difference between the working chamber that has finished suction and the adjacent working chamber that is in the middle of compression is small, and therefore the suction efficiency is 1
Close to 00%.

Moreover, by performing internal compression, it is possible to suppress an increase in torque, so the efficiency of one machine can be greatly improved.

[Brief explanation of the drawing]

Fig. 1 is a side view of one embodiment of the present invention, Fig. 2 is a sectional view including the rotating shaft of Fig. 1, and Fig. 3 is a sectional view of an example in which the embodiment of Fig. 1 is used in a screw fluid machine. , FIG. 4 is a sectional view of another embodiment of the invention, FIG. 5 is a sectional view of still another embodiment of the invention, and FIG. 6 is a sectional view of still another embodiment of the invention. 1 a, 1 b, 11 a, 1 l
b-Screw rotor, 2a, 2b, 1
2 a, 12 b - synchronous gear, 4, 14... Suction 0.5.15... Discharge port, 6, 16... Casing, 3... Power input shaft, 13a... Outer motor fixed representative People Patent Attorney Katsuo Ogawa-゛′ Toki /l! 1 Hanawa 2 Figure 1 Ku, To Screw Loaf No. 3 No. 4 Mouth/4- No. 5 Figure No. 6 Logo l (L, ij 衾 nu7su・-rotor

Claims (1)

[Scope of Claims] 1. A plurality of working chambers are formed in the direction of the rotation axis, each of which is formed by a screw rotor that meshes around two parallel shafts and a casing that houses this rotor. In a screw fluid machine where the spiral working chambers around the shaft do not communicate with each other, the sum of the outer diameter of one screw rotor and the root diameter of the other screw rotor is approximately constant regardless of the cross section perpendicular to the axis. While maintaining the same, the outer diameter of at least one of the two screw rotors is gradually decreased in the direction of the rotation axis, and at the same time the tooth bottom diameter of the mating rotor is gradually increased in the direction of the rotation axis, thereby creating a sloped tooth whose tooth height gradually decreases. A screw rotor having sloped teeth, characterized in that: 2. In claim 1, an outer motor (a structure in which the inner side is a stator and the outer side is a rotor) has a dead shaft fixed to a casing inside at least one screw rotor, and the dead shaft is the rotating shaft. A screw rotor having inclined teeth, characterized in that the screw rotor is driven by a motor).