JP4393217B2 - Scroll vacuum pump - Google Patents

Description

  The present invention relates to a scroll vacuum pump.

  First, a general configuration of the scroll vacuum pump will be described with reference to FIGS. 3 and 4.

  A drive shaft (5) integral with the eccentric shaft portion (4) is provided through the center of the housing (2) and the lid (3) in the housing (1).

  A rotating wrap (8) is erected on both sides of a rotating end plate (7) pivotally supported via a needle bearing (6) on an eccentric shaft portion (4) of a drive shaft (5), and a rotating scroll (9) is mounted. It is formed.

  Fixed wraps (10) that can be engaged with the orbiting wrap (8) are provided on the opposing surfaces of the housing (2) and the lid (3) in the housing (1), and the fixed scroll (11) is provided. It is formed.

  By meshing the swivel wrap (8) and the fixed wrap (10), a sealed chamber (12) whose volume changes in the radial direction according to the swirl is formed between the wraps (8) and (10). is there.

  A known crankpin type anti-rotation for preventing the orbiting scroll (9) from rotating over the orbiting end plate (7) and the outer peripheral portion of the housing (1) which is a stationary part. A mechanism (13) is provided.

  When the orbiting scroll (9) is eccentrically rotated with the drive shaft (5), gas is sucked from the intake hole (14) provided in the outer peripheral portion of the housing (2) of the housing (1). The volume is reduced and compressed as it goes toward the center of the housing (1), and then the ventilation hole (15) provided in the vicinity of the center of the sealed chamber (12) on the lid (3) side and the swivel end plate ( It is discharged from an exhaust hole (17) provided near the center of the sealed chamber (12) on the housing (2) side through a vent hole (16) provided near the center of 7).

  Therefore, in this case, when the scroll vacuum pump is operated by connecting the intake port (14) to a decompressed portion (not shown), the aerodynamic power necessary for compressing the gas is applied to the drive shaft at the initial stage of the operation. Although it is larger than the mechanical power consumed by the bearings to operate, this tendency reverses as the operation continues, and there is no gas suction when the inside of the sealed container reaches the ultimate pressure Therefore, mechanical power occupies most of the power required for operation.

  This will be described in detail with reference to FIG. 4, which is an enlarged longitudinal sectional view in the axial direction of the central portion of the turning wrap (8) and the fixed wrap (10).

  An inner peripheral end (8a) of the orbiting wrap (8) in the orbiting scroll (9) passes through a partition wall (18) and a discharge communication chamber (19), and is attached to an annular boss (20) that fits the needle bearing (6). It is lined up.

The partition wall (18) partitions the outer peripheral surface of the annular boss (20) and the innermost peripheral portion of the orbiting wrap (8), and communicates the sealed chamber (12) and the discharge communication chamber (19). A small-diameter discharge communication hole (21) is formed.

The discharge communication chamber (19) is formed on the inner peripheral side of the partition wall (18), that is, between the inner periphery in the circumferential direction of the partition wall (18) and the annular boss (20), and the exhaust hole (17) It is provided in the discharge communication chamber (19).

As long as the temperature of the intake air and outside air is within the normal range, and the gap between the swivel wrap (8) and the fixed wrap (10), the sliding contact range and friction with rotation, etc. are within the conditions assumed at the time of design, Further, as long as the inner peripheral end (10a) of the fixed wrap (10) is located within the design range, the above intake / exhaust is performed without abnormality.

However, if there is a change in the outside air temperature, abnormal deformation or extension of the swirl wrap (8) or fixed wrap (10), or abnormal contact pressure between the wraps (8) (10), the sealed chamber ( 12) The gas pressure at the inner end (12a) in the circumferential direction is excessive, and the gas cannot smoothly and continuously pass through the small-diameter discharge communication hole (21). In some cases, a closed state may occur.

  For this reason, the power required to drive the drive shaft may increase rapidly, or an excessive load may act on the bearing portion, etc., generating high heat and reducing the durability of each portion.

In order to prevent such inconvenience, the pressure of the gas generated at the inner end (12a) of the sealed chamber (12) during operation is slightly lower than the ideal maximum pressure. It is the actual situation that is set. However, this means that the ability that can be performed originally is held down to a low level, and there is nothing other than a disadvantage.
Further, an inlet (14), connected to the vacuum chamber is sealed, when reducing the pressure of the object to be vacuum chamber, in an initial operation is at startup, in a state of atmospheric pressure in the vacuum chamber gaseous Therefore, the discharge pressure increases, the load increases, and the driving power of the motor increases.
However, as the operation continues, the suction pressure decreases, and accordingly, the discharge pressure decreases to about atmospheric pressure, so the driving power of the motor decreases.

  Such a power state occurs in a vacuum pump for a certain period of time at the time of start-up. Therefore, a motor with a large driving power must be provided only to consume the power, which is disadvantageous in terms of cost. In addition, since a motor with a large output is provided, there is a problem that the weight and dimensions of the vacuum pump itself are increased.

For this purpose, a scroll compressor is also known in which an auxiliary discharge hole including a discharge valve is provided at a position communicating with the compression chamber on the end plate of the fixed scroll (Patent Document 1).
However, in this case, it is clear that the edge of the auxiliary discharge hole damages the chip seal in a short time, making it unusable.
JP-A-61-116085

  The problem to be solved by the present invention is that, in the scroll vacuum pump having the above-described configuration, as described above, the problem as described above is caused by the abnormal pressure increase at the inner end of the sealed chamber formed with the fixed wrap and the swirl wrap. It is to provide a scroll vacuum pump that can prevent the occurrence of the occurrence and that can achieve the intended purpose without the tip seal being damaged by the auxiliary discharge hole as described in Patent Document 1. .

According to the present invention, the above problem is solved by the following means.
(1) The fixed lap in the fixed scroll and the orbiting lap in the orbiting scroll are meshed with each other, and the latter is eccentrically orbited, so that the gas sucked from the outer periphery into the sealed chamber formed between the two wraps. In the scroll vacuum pump, which is pressurized as it goes in the center direction and is discharged from the exhaust hole provided in the center portion, the discharge communication chamber is provided at the inner end of the sealed chamber via a partition wall having a guide hole and a valve device. the provided, along with communicating this discharge communicating chamber and the exhaust hole, the valve device, it opens when the pressure of the gas in the inner end portion of the sealed chamber becomes constant or, enclosed chamber pressure gas At least a part of the air is allowed to escape into the discharge communication chamber.

(2) In the above item (1), the valve device includes a valve hole provided in the partition wall, a valve body provided in the valve hole so as to open toward the discharge communication chamber , and the valve body. and by spring biased to the inner end direction of the sealed chamber, and shall such and a spring adapted to to close the valve hole.

(3) In the above (1) or (2) section, the inner peripheral end of the orbiting wrap, connected to the outer peripheral surface of the annular boss that surrounds the exhaust hole, and slightly in the outer circumferential direction from the inner peripheral end of the orbiting wrap, the orbiting wrap an annular boss forms a partition wall spanning the outer peripheral surface of the orbiting wrap of the inner peripheral direction from the partition wall, with a space between the outer peripheral surface of the annular boss, the discharge communication chamber.

  Invention of Claim 1: When the pressure in the sealed chamber formed by the fixed wrap and the swirl wrap becomes equal to or higher than the design value at the inner peripheral end, the pressure is automatically reduced in the discharge communication chamber. , Discharged smoothly. Therefore, an excessive force does not act on each operating part, and the limit of the pressure at the inner peripheral end of the sealed chamber can be increased to improve the performance.

  Invention of Claim 2: When the pressure of the inner end part of a sealed chamber becomes more than a certain value, the valve device in the partition wall that separates this inner end part and the discharge communication chamber is automatically and simply used. Can be opened.

Invention of Claim 3: Since the discharge communication chamber is formed between the inner peripheral end of the swirl wrap and the annular boss , there is no need for a special space for the discharge communication chamber, and a sophisticated design is performed. Can do.

  The best mode for carrying out the present invention will be described with reference to FIG. 1 and FIG.

  1 and 2 are views showing inner end portions of a swirl wrap and a fixed wrap provided with an embodiment of the present invention, and an enlarged central portion of the figure corresponding to a longitudinal sectional view taken along line AA in FIG. FIG.

  Since the arrangement of the swing wrap (8) and the fixed wrap (10) and the like are basically not different from the conventional one shown in FIGS. 3 and 4, only the differences will be described.

A small-diameter discharge communication hole (21) is provided on the radially inner end of the partition wall (18) that partitions the sealed chamber (12) and the discharge communication chamber (19), and the radially outer side of the discharge communication hole (21). A large-diameter valve hole (22) is provided on the side. The valve hole (22) is fitted with a valve body (23) that can move toward the inside of the discharge communication chamber (19) and open.

  The valve body (23) is pushed in the direction of the sealed chamber (12) by the compression spring (24) provided in the discharge communication chamber (19), so that the valve hole (22) is always closed, and the sealed chamber (12 As long as the pressure at the inner end (12a) is within the proper range, the pressurized gas is smoothly discharged through the discharge communication hole (21), the discharge communication chamber (19), and the exhaust hole (17).

Thus, when the pressure at the inner end (12a) in the circumferential direction of the sealed chamber (12) becomes a predetermined value or more determined by design, the valve body (23) is opened by pushing the compression spring (24). . Therefore, the high-pressure gas in the inner end (12a) of the sealed chamber (12) escapes into the discharge communication chamber (19) and is depressurized to an appropriate pressure, and then is smoothly exhausted from the exhaust hole (17). It is done.

  Thus, according to the present invention, when the pressure at the inner end (12a) of the sealed chamber (12) exceeds a set value due to changes in temperature conditions or contact conditions of each part, the high-pressure gas is In the discharge communication chamber (19), the pressure is automatically reduced to an appropriate pressure.

  Accordingly, the gas at the inner end (12a) of the sealed chamber (12) is decompressed and smoothly and continuously discharged from the exhaust hole (17) toward the atmosphere, and the resistance of the drive shaft (5) is reduced. It is not excessive, and no excessive force is applied to the drive source and other operating parts.

  In the scroll vacuum pump, the overpressure at the inner peripheral end portion of the sealed chamber formed by the fixed wrap and the swirl wrap can be eliminated, and a smooth and light operation can be performed.

  Needless to say, the present invention can also be implemented in the vacuum pump in which the discharge communication hole is provided in the innermost periphery of the fixed scroll.

FIG. 4 is an enlarged cross-sectional view in the vicinity of the center portion of an embodiment of the present invention, showing a state in which an inner peripheral end of a fixed wrap is separated from a sealed indoor end portion. It is a figure similar to FIG. 1 in the state which the inner peripheral end of a fixed wrap is adjoining to the sealed indoor end part. It is a vertical side view which shows the typical example of the conventional scroll vacuum pump. It is an AA line expanded vertical sectional view in FIG. 3, and is a figure which shows the state which the inner peripheral end of a fixed lap is in close contact with the inner peripheral end part of a contact | adherence chamber.

(1) Housing
(2) Housing
(3) Lid
(4) Eccentric shaft
(5) Drive shaft
(6) Needle bearing
(7) Revolving end plate
(8) Turning lap
(8a) Inner peripheral edge
(9) Orbiting scroll
(10) Fixed wrap
(10a) Inner edge
(11) Fixed scroll
(12) Sealed room
(12a) Inner end
(13) Anti-rotation mechanism
(14) Intake hole
(15) (16) Vent
(17) Exhaust hole
(18) Bulkhead
(19) Discharge communication chamber
(20) Annular boss
(21) Discharge communication hole
(22) Valve hole
(23) Disc
(24) Compression spring

Claims (3)

The fixed lap in the fixed scroll and the orbiting wrap in the orbiting scroll are meshed with each other, and the latter is eccentrically orbited, so that the gas sucked from the outer peripheral portion into the sealed chamber formed between the two wraps in the central direction. In the scroll vacuum pump that pressurizes as it goes to and discharges it from the exhaust hole provided in the center,
The inner end portion of the sealed chamber, a discharge communicating chamber provided via a partition wall having a guide bore and the valve device, with communicating the discharge communicating chamber and said exhaust port, said valve device, said sealed chamber A scroll vacuum pump that opens when the gas pressure at the inner end becomes a certain level or more and allows at least part of the pressure gas in the sealed chamber to escape into the discharge communication chamber. The valve device includes a valve hole provided in the partition wall, a valve body provided in the valve hole so as to open toward the discharge communication chamber , and the valve body in the direction toward the inner end of the sealed chamber. The scroll vacuum pump according to claim 1, comprising a spring adapted to close the valve hole by energizing the spring. The inner peripheral end of the orbiting wrap, connected to the outer peripheral surface of the annular boss that surrounds the exhaust hole, and in somewhat outer circumferential direction from the inner peripheral end of the orbiting wrap to form a partition wall spanning the outer peripheral surface of the orbiting wrap and the annular boss, The scroll vacuum pump according to claim 1 or 2 , wherein a space between the turning wrap in the inner circumferential direction from the partition wall and the outer circumferential surface of the annular boss is used as a discharge communication chamber.

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