JPH07301234A - Fluid machine - Google Patents

Abstract

PURPOSE:To correct the floating position of a shaft due to a machining error into an optimum capacity state. CONSTITUTION:A fluid machine comprises a magnetic bearing to float and support a shaft 22 to a supporting member, a position sensor to detect the floating position of the shaft 22, a magnetic field control means 5a to control the magnetic field strength of a magnetic bearing for floating and supporting the shaft 22, a variation input means 52 to input waveform signals into the magnetic field control means 5a for reciprocally vary the floating position of the shaft 22, a vacuum sensor 53 to detect the degree of vacuum, an integration computing means 5b to compute an integration value for a product between the variation of the shaft 22 with the variation input means 52 and the degree of vacuum at each variation position, and a shaft center setting means 5c to output optimum position signals from the shaft 22 to the magnetic field control means 5a for maintaining the optimum degree of vacuum in accordance with an integration value given by the integration computing means 5b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluid machine, and more particularly to a countermeasure for setting an axial center by a magnetic bearing.

[0002]

2. Description of the Related Art Conventionally, there has been a vacuum pump as one of fluid machines. For the vacuum pump, there is a real exploitation 64-43295.
As disclosed in Japanese Patent Laid-Open Publication No. 2000-242242, a rotary shaft is inserted into a shaft hole of a support member provided in a casing, and a drive motor for the rotary shaft is provided in the shaft hole, while the rotary shaft has:
There is a configuration in which the rotor of the first screw groove pump unit is attached and the rotor of the second screw groove pump unit is attached. The vacuum pump causes the second screw groove pump section to generate an intermediate vacuum state, and
A high vacuum state is generated by the thread groove pump section. In the above vacuum pump, the rotation axis is up and down 2
One radial magnetic bearing and one lower thrust magnetic bearing are floated in the shaft hole, and are supported by the support member in a non-contact manner.

[0003]

In the above-mentioned vacuum pump, the magnetic bearing has conventionally controlled the magnetic field strength of the electromagnet so that the axis of the rotary shaft coincides with the center of the shaft hole. However, matching the axis of the rotary shaft with the center of the shaft hole may not be optimal in terms of pump performance. That is, in the vacuum pump, the performance varies depending on the gap between the rotor and the stator, and the gap varies depending on the processing error. The processing error varies depending on each product and varies, so that the processing error cannot be recognized in advance. Therefore, it was unclear whether or not the rotor was set in the optimum state. In particular, conventionally, no consideration has been given to the clearance adjustment between the rotor and the stator due to this processing error, and therefore, there is a problem that it is not always used in the optimum state in which the ability is most exerted. Therefore, it is conceivable that the optimum point of the rotation axis is randomly fine-tuned to search while monitoring the degree of vacuum arrival, but this has a problem that it takes a lot of time and effort.

The present invention has been made in view of the above point, and an object of the present invention is to correct the floating position of the rotary shaft so as to absorb a machining error and bring it to an optimum performance state.

[0005]

In order to achieve the above object, the means taken by the present invention calculates the optimum position of the rotary shaft from the amount of fluctuation of the rotary shaft and the pressure value of the changed position. It was done like this. Specifically, as shown in FIG. 1, the means taken by the invention according to claim 1 is that a support member (21) provided inside a casing (11) and having a shaft hole (23) is formed. A fluid having a rotary shaft (22) inserted into the shaft hole (23) of the support member (21) and a fluid action part (30) connected to the rotary shaft (22) for exchanging energy with the fluid. It is premised on machines. Then, a magnetic bearing (40) for levitating and supporting the rotating shaft (22) with respect to the support member (21), and position detecting means (4a, 4b, 4c) for detecting the floating position of the rotating shaft (22), Is provided. Further, the magnetic field strength of the magnetic bearing (40) so as to float and support the rotating shaft (22) at a predetermined position with respect to the supporting member (21) based on the position signal of the position detecting means (4a, 4b, 4c). A magnetic field control means (5a) for controlling is provided. Moreover, a fluctuation input means (52) for inputting a waveform signal for reciprocating the floating position of the rotating shaft (22) to the magnetic field control means (5a), and a pressure detection means (53) for detecting the pressure of the fluid. And are provided. In addition, the rotary shaft (22) by the fluctuation input means (52)
Which is an integrated value of the product of the amount of fluctuation of the waveform and the pressure value at each fluctuation position detected by the pressure detecting means (53), and which calculates at least one cycle of the waveform signal of the waveform input means. Means (5b) are provided. Moreover, the optimum position signal of the rotating shaft (22) is sent to the magnetic field control means so that the fluid has the optimum pressure value based on the integral value of the integral calculation means (5b).
A shaft center setting means (5c) for outputting to (5a) is provided.

Further, in the invention of claim 1 described above, in the means implemented by the invention of claim 2, the waveform input means reciprocally fluctuates the floating position of the rotary shaft (22) in the radial direction, and a rotation signal. And a waveform signal for reciprocating the floating position of the shaft (22) in the thrust direction.
In the means implemented by the invention according to claim 3, the waveform input means is
It is configured to output a sinusoidal waveform signal. Further, the means taken by the invention according to claim 4 is that in the invention according to claim 1, 2 or 3, the fluid acting portion (30) is a vacuum pump portion.

[0007]

With the above construction, in the invention according to claim 1,
The rotating shaft (22) is levitated and supported by a magnetic bearing (40) with respect to a support member (21), and the magnetic bearing (40) is a magnetic field control means.
The magnetic intensity is controlled by (5a). The rotation of the rotating shaft (22) causes the fluid action portion (30) to exchange energy with the fluid. Specifically, in the invention according to claim 4, the vacuum pump section (30) sucks and discharges gas molecules.

On the other hand, to the magnetic field control means (5a), the waveform signal is added from the fluctuation input means (52) to the position signal of the initial floating position and is input. Specifically, claim 2
In the inventions according to 3 and 4, the fluctuation input means (52) includes the rotary shaft (2
A waveform signal that fluctuates 2) in the radial direction and a waveform signal that fluctuates in the thrust direction are output, and this waveform signal is composed of a sinusoidal waveform signal. Also, the pressure detection means
(53) detects the fluid pressure, for example, detects the ultimate vacuum, and the detection signal is input to the integral calculation means (5b). Therefore, the integral calculation means (5b) is a fluctuation input means.
The integrated value is calculated by integrating the product of the fluctuation amount of the rotating shaft (22) due to (52) and the fluid pressure detected by the pressure detecting means (53) for at least one cycle of the waveform signal. After that, the axis center setting means (5c)
Outputs the optimum position signal of the rotary shaft (22) to the magnetic field control means (5a) based on the integrated value. That is, the axis center setting means (5c) calculates the amount of movement by multiplying the integrated value by a predetermined control gain. Then, the magnetic field control means (5a) is a magnetic bearing so that the rotating shaft (22) is located at the derived optimum floating position.
(40) will be controlled.

[0009]

Therefore, according to the invention of claim 1,
Since the optimum floating position of the rotary shaft (22) is derived from the integrated value of the product of the fluctuation amount of the rotary shaft (22) and the fluid pressure at each fluctuation position, the machining error is calculated. Since it can be corrected, the fluid action portion (30) can be rotated at the optimum position. As a result, since the driving can be performed in the optimum state, the capacity can be maximized and highly efficient operation can be performed. In addition, claim 2
According to the invention of (1), the rotating shaft (22) is changed in the radial direction and the thrust direction.
It is possible to reliably absorb the processing error between the radial direction and the thrust direction. Further, according to the invention of claim 3, since the fluctuation input means (52) is configured to give a reciprocal fluctuation of a sine waveform to the rotation axis (22), the integral calculation becomes extremely easy. The optimum floating position of the rotary shaft (22) can be easily set. In particular, according to the invention of claim 4, in the case of the vacuum pump portion (30), the position of the rotor has a great influence on the performance, that is, the performance can be improved by adjusting the clearance, so that the maximum ultimate vacuum degree can be achieved. Can be improved.

[0010]

Embodiments of the present invention will now be described in detail with reference to the drawings. As shown in FIG. 2, a vacuum pump (10), which is one of the fluid machines, has a rotary drive unit inside a casing (11).
(20) and the thread groove pump section (30) are housed and configured. The casing (11) is formed in a substantially cylindrical shape, and the upper surface thereof is formed as a suction port (12) communicating with the vacuum space, and the discharge port (13) is opened at the lower portion of the side surface. . The rotation drive section (20) includes a support member (21) fixed to the casing (11) and a rotation shaft (22), and the support member (21) is formed in a substantially cylindrical shape. A shaft hole (23) is vertically formed in the center. The rotating shaft (22) is a support member.
It is inserted into the shaft hole (23) of (21) and arranged in the axial direction of the support member (21) (vertical direction in FIG. 2). And
The rotating shaft (22) is rotatably supported by a supporting member (21) via a bearing means (40), while the rotating shaft (22) is provided in the central portion of the shaft hole (23). Drive motor for rotating
(24) is provided. In addition, (25, 25, ...) is the shaft hole (23)
Are protective bearings arranged on the upper and lower parts of the. The screw groove pump section (30) has a rotor (31) housed in the upper part of the casing (11) to form a vacuum pump section.
The (31) is formed in a cylindrical shape with its upper part closed, and has a thread groove formed on its outer peripheral surface. The rotor (31) is located so that the thread groove (32) on the outer peripheral surface closely faces the inner peripheral surface of the casing (11) and is connected to the upper end of the rotating shaft (22). Inside the casing (11), the thread groove (3
A flow path (33) is formed from the suction port (12) to the discharge port (13) via the (2).

The bearing means (40) is a magnetic bearing for supporting the rotating shaft (22) by levitation with respect to the support member (21) in a non-contact state, and includes an upper radial magnetic bearing (41) and a lower radial magnetic bearing. (42) and a thrust magnetic bearing (43). The upper radial magnetic bearing (41) is arranged in the lower part of the shaft hole (23), the lower radial magnetic bearing (42) is arranged in the lower part of the shaft hole (23), while the thrust magnetic bearing (43) is arranged in the shaft hole (23). It is located at the lower end of 23). Although not shown, the two radial magnetic bearings (41, 42) are, for example, 4 symmetrically with respect to the center of the shaft hole (23).
A pair of electromagnets (4a, 4b) are arranged, and the electromagnets (4a, 4b
The rotary shaft (22) is sucked by b) and the rotary shaft (22) is inserted into the shaft hole (2
It is levitationally supported without contact in the radial direction with respect to 3).
The thrust magnetic bearing (43) includes, for example, four pairs of electromagnets with a flange (26) attached to the lower end of the rotating shaft (22) interposed therebetween.
(4c) are arranged, and the rotating shaft (2
2) is sucked and the rotating shaft (22) is levitationally supported in the thrust direction in a non-contact manner with respect to the shaft hole (23). In addition, above the upper radial magnetic bearing (41), the upper radial position sensor (4
4), lower radial position sensors (45) are arranged below the lower radial magnetic bearings, and thrust position sensors (46) are arranged below the lower end surface of the rotating shaft (22).
The both radial position sensors (44, 45) detect the floating position of the rotary shaft (22) in the radial direction, that is, the radial position of the shaft center of the rotary shaft (22) with respect to the center of the shaft hole (23). The thrust position sensor (46) detects the floating position of the rotary shaft (22) in the thrust direction and outputs a position signal. There is.

FIG. 3 shows a bearing control system by the above magnetic bearings (41, 42, 43), which is provided with a control system (50) for each magnetic bearing (41, 42, 43). The control system (50) consists of magnetic bearings (4
The magnetic field control means (5a) is provided for controlling the magnetic field strength of the electromagnets (4a, 4b, 4c) in (1, 42, 43). That is, the magnetic field control means (5a) is composed of, for example, PID control means,
The magnetic field strength of the electromagnets (4a, 4b, 4c) in each magnetic bearing (41, 42, 43) is controlled by receiving the initial flying position signal of (22) and the feedback signal. Each of the magnetic bearings (41, 42, 43) supports the rotating shaft (22) by levitation with respect to the shaft hole (23), and the rotating shaft (22) has, for example, an axial center (2).
It is controlled to match the center of 3). Further, the floating position of the rotary shaft (22) is detected by each position sensor (44, 45, 46), and the gain control means (51) outputs a control gain based on the displacement amount of the rotary shaft (22). Then, the control gain is fed back to the magnetic field control means (5a) as a feedback signal.

Further, as a feature of the present invention, the above magnetic control system (50) is provided with a fluctuation input means (52) and has a control system.
The integral calculation means (5b) and the axis center setting means (5c) are provided at (50). The fluctuation input means (52) is the rotary shaft (22).
The sine wave signal (waveform signal) for reciprocating the flying position of the head in the radial direction and the thrust direction is added to the initial flying position signal and input to the magnetic field control means (5a). Further, a detection signal is inputted from the vacuum degree sensor (53) to the integral calculating means (5b), and the vacuum degree sensor
(53) constitutes pressure detection means for detecting the fluid pressure on the suction port (12) side, that is, the degree of vacuum. The integral calculation means (5b) is a product of the variation amount of the rotary shaft (22) reciprocally varied by the variation input means (52) and the ultimate vacuum degree at each variation position detected by the vacuum degree sensor (53). Is the integral value of
The integrated value of at least one cycle of the waveform signal is calculated. The shaft center setting means (5c) outputs the optimum position signal of the rotating shaft (22) to the magnetic field control means (5a) so that the optimum vacuum degree is obtained based on the integral value of the integral calculation means (5b). Is configured.

Therefore, the integral calculating means (5b) is
The basic principle of calculating the integrated value of the product of the fluctuation amount in (22) and the ultimate vacuum at each fluctuation position will be described. As shown in FIG. 4, when the vacuum degree Y is set on the vertical axis and the floating position X of the rotation axis (22) is set on the horizontal axis, the relationship between the vacuum degree Y and the floating position X is, for example, a quadratic curve A. Assuming that, the tangent line B of the quadratic curve A at the initial flying position X0 is as follows: Y = a · X + b. On the other hand, the integral value R of the product of the variation and the degree of vacuum is as follows:

[0015]

[Formula 1] Becomes Therefore, the ultimate vacuum Y with respect to the fluctuation of the sine waveform
The change of can be approximated to the following equation if the above variation is small, so that Y = a · X0 + a · Sinωt + b ... The above equation is as follows.

[0016]

[Formula 2] Therefore, when the above formula is calculated, the following formula is obtained.

[0017]

[Formula 3] That is, the integrated value R is represented by a function of the slope a of the tangent line B. Therefore, in FIG. 4, since the inclination a of the tangent line B is zero at the optimum flying position Xs where the ultimate vacuum is the highest, if the absolute value of the integrated value R is large, the initial floating position X0 is the optimum flying position Xs. It means that the displacement is larger, and the displacement direction can be identified by the sign. Therefore, the control gain η
The amount of movement ΔX is calculated by multiplying by.

-Vacuum Pump Action- Next, the operation of the vacuum pump (10) will be described. First, when the vacuum operation is started, the rotation shaft (22) is rotated by the rotation of the drive motor (24), the rotor (31) is rotated, and the suction port is rotated.
Air, that is, gas molecules are sucked from (12), and these gas molecules are pushed along the screw groove (32) to the downstream side which is the discharge port (13) and discharged from the discharge port (13). become. Therefore, the operation of setting the floating position of the rotary shaft (22) will be described based on the control flow of FIG. At the start of this setting operation, the initial floating position X0 is input, and the fluctuation input means (5
The sine wave fluctuation signal is added from (2) and the magnetic field control means (5
Entered in a). The waveform signal of this sine wave is set to a frequency sufficiently lower than that of the position control signal. Also,
For the amplitude of the waveform signal, since the approximate expression of the expression is applied,
If it is set too large, the error becomes large, and conversely, if it is made too small, the effect of fluctuating is not exhibited, so it is set to an appropriate value. This magnetic field control means (5a) controls the magnetic field strength of each magnetic bearing (41, 42, 43),
(22) is levitationally supported on the support member (21) in a non-contact manner. On the other hand, in the vacuum space (not shown) on the suction port (12) side, the vacuum degree sensor (53) detects the ultimate vacuum degree,
The detection signal of this ultimate vacuum is the integral calculation means of the control system (50).
It is entered in (5b). Therefore, in step ST1, the integral calculation means (5b), based on the command position signal obtained by adding the fluctuation position to the initial floating position X0, the fluctuation amount of the rotary shaft (22) and the ultimate vacuum of the vacuum sensor (53). The integrated value R is calculated by integrating the product of the degree and the degree for one cycle of the sine wave according to the formula.

After that, the above steps ST1 to ST
Moving to 2, it is determined whether the integrated value R has converged. That is, as shown in the above equation, since the integral value R is a function of the slope a of the tangent line B, when the integral value R is small, it is close to the extreme value of the quadratic function A and the rotation axis (22) is It will be close to the optimum ascent position Xs. Therefore, the minimum value Rmin of the integrated value R is set in advance, and it is determined whether or not the calculated integrated value R is smaller than the minimum value Rmin. The minimum value Rm of this integrated value R
in is set appropriately so that the convergence determination is not repeated many times. When the calculated integrated value R is larger than the minimum value Rmin, the inclination a of the tangent line B is large, and therefore the rotation axis (22) is
Since the initial flying position X0 is located away from the optimum flying position Xs, the steps ST2 to ST3 above are performed.
Then, the axis setting means (5c) calculates the moving amount ΔX by multiplying the integral value R by the control gain η. It should be noted that if the control gain η is too large, the movement amount ΔX becomes too large and hunting occurs, so it is set to an appropriate value. Subsequently, the process proceeds from step ST3 to step ST4, and the axis center setting means (5c) derives the flying position X1 (= X0 + ΔX) at which the set floating position is higher than the current floating position X0 and controls the magnetic field. A position signal will be output to the means (5a). Then, the magnetic levitation means controls the magnetic bearings (41, 42, 43) so that the rotating shaft (22) is located at the derived levitation position X1. Then, the process returns from step ST4 to step ST1 to repeat the above operation. That is, as shown in FIG.
The new floating position X1 is set from the initial floating position X0, and the floating position is sequentially moved until the integrated value R reaches the minimum value Rmin. When the above integrated value R reaches the minimum value Rmin by repeating this operation, the ultimate vacuum reaches the maximum value or is almost close to the maximum value, and the rotary shaft (22) is set to the optimum floating position. Therefore, the determination in step ST2 is NO.
Then, the setting operation ends. After that, place the magnetic bearings so that the rotary shaft (22) is located at the optimum floating position.
The magnetic strength of (41, 42, 43) is controlled, that is, the rotation axis (22)
When is displaced, the gain control means (51) feeds back the control gain to the magnetic field control means (5a) by the position signal of each position sensor, and the rotary shaft (22) is positioned at the set levitation position.

-Effects of Embodiment-As described above, according to the present embodiment, from the integral value of the product of the fluctuation amount in which the rotary shaft (22) is positively changed and the ultimate vacuum at each fluctuation position, Since the optimum floating position of the rotary shaft (22) is derived, the machining error can be corrected, so that the rotor (31) can be rotated at the optimum position. As a result, since the driving can be performed in the optimum state, the vacuum capacity can be maximized and highly efficient operation can be performed. Further, since the rotary shaft (22) is made to fluctuate in the radial direction and the thrust direction, it is possible to surely absorb the machining error between the radial direction and the thrust direction of the rotary shaft (22). In addition, the fluctuation input means
In (52), since the reciprocal fluctuation of the sine waveform is applied to the rotating shaft (22), the integral calculation becomes extremely easy, so it is easy to set the optimum floating position of the rotating shaft (22). You can Further, the integral calculating means (5b) may integrate two or more cycles of the waveform signal. Especially the vacuum pump
In the case of (10), since the position of the rotor (31) greatly affects the performance, that is, the performance can be improved by adjusting the clearance, the maximum ultimate vacuum can be improved.

-Other Modifications-In this embodiment, the vacuum pump (10) has been described.
The present invention can also be applied to a support structure for the rotating shaft (22) such as a scroll compressor or a rotary piston pump. Further, although the fluctuation input means (52) inputs the sine wave signal, it may be a triangular wave signal or the like. In short, the relationship between the input waveform signal and the ultimate vacuum degree for the waveform signal can be understood. The waveform signal may have any waveform. Further, the fluctuation input means (52) in the invention according to claim 1 is
A waveform signal for varying the rotating shaft (22) in either the radial direction or the thrust direction of the rotating shaft (22) may be output.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of the present invention.

FIG. 2 is a sectional view showing a vacuum pump.

FIG. 3 is a control block diagram showing a bearing control system.

FIG. 4 is a characteristic diagram of an ultimate vacuum degree with respect to a changing position of a rotating shaft.

FIG. 5 is a flowchart showing position control of a rotary shaft.

[Explanation of symbols]

 10 Vacuum pump 21 Support member 22 Rotating shaft 23 Shaft hole 30 Thread groove pump section 40 Bearing means 41,42,43 Magnetic bearing 44,45,46 Position sensor 50 Control system 5a Magnetic field control means 5b Integral calculation means 5c Shaft center setting means 51 Gain control means 52 Fluctuation input means 53 Vacuum sensor

Claims (4)

[Claims] 1. A shaft hole provided inside a casing (11).
(23) is formed on the support member (21), the rotary shaft (22) inserted into the shaft hole (23) of the support member (21), the rotary shaft (22) is connected to the fluid and energy. In a fluid machine including a fluid action part (30) to be replaced, a magnetic bearing (40) for levitating and supporting the rotating shaft (22) with respect to a supporting member (21), and a floating position of the rotating shaft (22). Position detecting means (4a,
4b, 4c) and the magnetic bearing (40) so as to float and support the rotating shaft (22) at a predetermined position with respect to the supporting member (21) based on the position signals of the position detecting means (4a, 4b, 4c). ) Magnetic field control means (5a) for controlling the magnetic field strength, a fluctuation input means (52) for inputting to the magnetic field control means (5a) a waveform signal that reciprocally fluctuates the floating position of the rotating shaft (22), and The product of the pressure detection means (53) for detecting the pressure of the fluid, the fluctuation amount of the rotary shaft (22) by the fluctuation input means (52) and the pressure value at each fluctuation position detected by the pressure detection means (53). Integral calculation means for calculating at least one cycle integral value of the waveform signal of the waveform input means.
(5b) and a shaft center setting for outputting an optimum position signal of the rotating shaft (22) to the magnetic field control means (5a) so that the fluid has an optimum pressure value based on the integral value of the integral calculation means (5b). A fluid machine comprising means (5c). 2. The fluid machine according to claim 1, wherein the waveform input means reciprocates the waveform signal for reciprocating the floating position of the rotary shaft (22) in the radial direction and the floating position of the rotary shaft (22) in the thrust direction. A fluid machine configured to output a reciprocating waveform signal. 3. The fluid machine according to claim 1, wherein the waveform input means is configured to output a sinusoidal waveform signal. 4. The fluid machine according to claim 1, 2, or 3, wherein the fluid acting portion (30) is a vacuum pump portion.