JPH0658041B2 - Thrust force balancing method for screw type rotary machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION “Industrial field of application” The present invention provides a balance piston at the shaft end of a screw rotor, and applies a predetermined fluid pressure to the balance piston so that the thrust force of a screw-type rotating machine is improved. Regarding how to balance.

"Prior Art" Conventionally, a screw compressor that performs gas compression by rotating a male rotor and a female rotor while meshing with each other is already known. Since the mouth and the outlet are arranged,
A differential pressure and a dynamic pressure (hereinafter referred to as a thrust force) generated at the time of discharging compressed gas are applied to the thrust bearing portion that axially supports the rotor (in the axial direction from the discharge side to the intake side). The discharge of compressed gas is not continuous but is intermittently discharged according to "rotor speed x male rotor tooth count", so the thrust force also pulsates, and vibration and noise of the thrust bearing occur. Moreover, due to these vibrations, the life of the thrust bearing is shortened.

In order to prevent such a drawback, a technique is proposed in which a balance piston is provided at the shaft end portion of the screw rotor, and a fluid pressure is applied to the balance piston in a direction to suppress the thrust force applied to the thrust bearing. Has been done.

[Problems to be Solved by the Invention] In this type of technology, a gear pump is generally used to apply fluid pressure to the balance piston, and the rotation of the gear pump is generally independent of the rotation of the screw rotor. As shown in Fig. 2c, the load applied to the thrust bearing increases or decreases due to the synergistic effect of the thrust force and the pressure applied to the balance piston, and in the worst case, the pulsating pressure of the gear pump is changed as shown in Fig. 2c. In some cases, the fluctuation width of the thrust force applied to the thrust bearing acts in the direction of amplification, and the vibration noise of the thrust bearing is rather amplified. (See FIG. 2) Incidentally, (a) of FIGS. 2a to 2d show the time series changes of the thrust force (F) and the pressure (P) applied to the balance piston, respectively.
(B) shows a time series change of the load (W) applied to the thrust bearing.

Further, in order to eliminate such drawbacks, a technique of disposing a cushion tank or the like between the balance piston and a gear pump to make the fluid pressure applied to the balance piston constant is also disclosed. No. 2b even if you take such a configuration
As shown in the figure, it is possible to reduce the thrust force, but the pulsation and fluctuation range cannot be suppressed.

In view of the above-mentioned drawbacks of the prior art, the present invention suppresses the fluctuation of the thrust force itself, prevents the generation of vibration and noise resulting from the fluctuation, and improves the durability of the thrust bearing. The purpose is to provide a method of balancing power.

"Means for Solving Problems" In order to achieve the technical problem, the present invention provides balance pistons 3 and 3'on the shaft ends of the screw rotors 1 and 2 as shown in FIG. 1, for example. In the method of balancing the thrust force B of the screw type rotating machine by applying a predetermined fluid pressure A to the balance pistons 3, 3 ',
Fluid pressure A for pressurizing the balance pistons 3 and 3 '
Is changed in synchronism with the fluctuation cycle of the thrust force B generated by the rotation of the screw rotors 1 and 2 to suppress the pulsation of the thrust force B applied to the thrust bearing 4 by the fluid pressure A. In the proposed and particularly preferred embodiment, the pulsating pump 5 is used as the fluid pump for applying the fluid pressure A to the balance piston 3, and its pulsating frequency is set to be the same as the fluctuation cycle of the thrust force B of the rotating machine. Pulsation pump 5 to balance pistons 3 and 3 '
Pulsation pump 5 corresponding to the fluid passage volume in pipe 6 up to
It is preferable that the pulsation frequency of the fluid pressure A is synchronized with the fluctuation cycle of the thrust force B by adjusting the start time of rotation of.

Incidentally, the present technical means is applicable to any of the screw compressor or the screw expander, but in the case of the screw compressor, the direction in which the thrust force is generated is from the discharge side to the intake side,
In the case of a screw expander, since the intake side is opposite to the discharge side, the pressurizing direction of the fluid pressure A is also set in the opposite direction.

The pulsation pump 5 may be a gear pump, a screw pump, or the like.

When such a pump is used, the pulsation frequency of the fluid pressure is set to be the same as the cycle of the thrust force B of the rotary machine by making the "revolution speed x number of pump rotor teeth" match that of the screw rotary machine. You can do it.

Even with such a structure, a time lag occurs due to the fluid passage volume (pipe length x diameter) of the pipes 10 and 10 'from the pulsation pump 5 to the balance piston 3, so that the pulsation corresponds to the fluid passage volume. It suffices to configure the pump 5 so that the pump 5 is rotated while shifting the rotation phase.

Further, according to the present technical means, the balance pistons 3 and 3'are attached to both the male and female rotors 1 and 2 to apply the fluid pressure from the pulsation pump 5, but the thrust force applied to the male rotor 1 is On the other hand, since the female rotor 2 has a minute amount of about 10 to 20%, the balance piston 3 may be attached only to the male rotor 1.

"Operation" According to the technical means, the fluid pressure A applied to the balance pistons 3 and 3'is changed in synchronization with the intermittent fluctuation of the thrust force B generated by the rotation of the screw rotors 1 and 2, and Since the pulsation of the thrust force B applied to the thrust bearing 4 is suppressed by the pressure A, the fluctuation of the thrust force is canceled by the fluid pressure A, and the fluctuation of the thrust force B is completely eliminated as shown in FIG. 2a. Can be prevented.

[Embodiment] Hereinafter, a preferred embodiment of the present invention will be exemplarily described in detail with reference to the drawings. However, unless otherwise specified, the dimensions, materials, shapes, relative positions, etc. of the components described in this embodiment are not intended to limit the scope of the present invention only thereto, but merely illustrative examples. Nothing more than.

FIG. 3 shows the configuration of a screw compressor according to an embodiment of the present invention, in which the male and female rotors 1 and 2 are housed in a case 6,
Thrust bearings 4a and 4b are attached to the other ends of the respective shafts 11 and 21 on the discharge side, and drive gears or couplings 9 are attached to the discharge sides of the male rotor 1-side shafts 11, respectively. The male rotor 1 is rotated in response to the rotation of the female rotor 2 and the female rotor 2 is driven by the synchronous gear to rotate without contact, and the male rotor 1 and the female rotor 2 are 4 × 6 meshed with each other. The number of teeth is set, and the compressed gas is discharged at a cycle of four times per rotation.

Further, balance pistons 3, 3'are attached to the shaft ends of the intake side shafts 11, 21 of the male rotor 1 and the female rotor 2, and the balance pistons 3, 3'are formed in the case 6 as cylinders 13, 13 '. It is hermetically fitted inside.

The diameters of the balance pistons 3 and 3'are determined in proportion to the thrust force applied to the corresponding rotors 1 and 2.

Further, the balance pistons 3, 3'are provided with port portions 31, 31 'so that oil supply pressure is applied from the intake side to the discharge side, and the ports 31, 31' are screwed through pipes 10, 10 '. Attach the hydraulic pump 5.

The screw hydraulic pump 5 has the same number of rotor teeth as the screw compressor, that is, a fraction of 4 × 6.

Reference numeral 14 is a control circuit that detects the rotational speed and phase of the screw compressor and determines the rotational phase of the rotational speed of the screw hydraulic pump 5.

That is, in the control circuit 14, the fluid passage volume of the pipes 10 and 10 'from the hydraulic pump 5 to the balance pistons 3 and 3' (pipe 1
In order to correct the time lag caused by (0,10 'length x diameter), the hydraulic pump 5 is rotated at the same speed by shifting the rotational phase of the hydraulic pump 5 in accordance with the fluid passage volume, and the fluid pressure applied to the balance pistons 3, 3' The pulsation frequency of A is synchronized with the fluctuation cycle of the thrust force B.

For example, the male rotor 1 of the hydraulic pump 5 has four teeth, and the fluid passage capacity of the pipes 10 and 10 'is one cycle (1
In the case where the discharge amount per / 4 rotation) is 9.5 times, if the rotation start time of the pump 5 is rotated 45 degrees out of phase, the synchronization can be achieved.

In addition, since the back pressure of the discharge pressure is present on the discharge side even during the no-load operation, and therefore, the pulsation of the thrust force similar to that at the time of the load occurs, the fluid pressure from the hydraulic pump 5 is balanced pistons 3, 3 ′. Need to be given to.

[Advantages of the Invention] As described above, according to the present invention, since the fluid pressure applied to the balance piston is changed in synchronization with the intermittent fluctuation of the thrust force, the fluctuation of the thrust force can be completely prevented. It is possible to prevent the generation of vibration and noise due to the fluctuation of the thrust force and to improve the durability of the thrust bearing. It has various remarkable effects.

[Brief description of drawings]

FIG. 1 is a schematic diagram for explaining the principle of the present invention, FIGS. 2a to 2c are action diagrams comparing the action of the present invention in comparison with a conventional example, and FIG. 2a shows the action of the present invention. Second b
FIGS. 2c and 2d respectively explain the operation of the prior art, in which (a) is a time series distribution diagram showing the relationship between the thrust force and the pressure of the balance piston, and (b) is a combination of both. It is a time-series distribution chart which shows the changed load. FIG. 3 is a sectional view of a screw compressor showing an embodiment of the present invention.

Claims (2)

[Claims] 1. A method of balancing a thrust force of a screw type rotary machine by providing a balance piston at a shaft end portion of a screw rotor and applying a predetermined fluid pressure to the balance piston. Is set with a pulsating fluid pressure whose pressure fluctuates periodically, and the pulsating frequency of the fluid pressure is set so as to be substantially synchronized with the periodic fluctuation of the thrust force generated by the rotation of the screw rotor,
Thrust force balancing method characterized in that the pulsating fluid pressure is applied to the balance piston so as to act in a direction in which the periodic fluctuation of the thrust force is canceled out. 2. A pulsating pump is used as a fluid pump for applying a fluid pressure to the balance piston, and the pressure pulsating frequency is set to be the same as the fluctuation cycle of the thrust force of the rotating machine, and in the pipe from the pulsating pump to the balance piston. The thrust force balancing method according to claim 1, wherein the rotational phase of the pulsation pump is adjusted in accordance with the fluid passage volume, and the pulsation frequency of the fluid pressure is synchronized with the fluctuation period of the thrust force.