JP6747302B2 - Vacuum valve - Google Patents

Description

The present invention relates to vacuum valves.

A vacuum valve that automatically adjusts a chamber internal pressure to a preset predetermined pressure is used in a manufacturing apparatus such as a semiconductor or a flat panel display. As one of such vacuum valves, a pendulum type slide valve as described in Patent Document 1 is known. In the pendulum type valve, the valve body is oscillated by a motor to change the opening degree θ corresponding to the opening area of the gas flow passage to adjust the conductance, which is an index of the ease of gas flow. In particular, a stepping motor is generally used as a motor for driving the valve body because it is necessary to finely adjust the opening in the vicinity of the target pressure.

The motor has an absolute value encoder using a magnet, and the controller detects the magnetic pole position of the motor to separately control the q-axis, which is the operation in the rotation direction, and the d-axis, which is the holding direction. it can. When the valve body is stopped, a constant current is applied to the d-axis current (field current Id) and the q-axis current (torque current Iq) is controlled to zero, so that the valve body can be held at a predetermined position. .. As a result, the valve body is held at the desired stop position even when there is an influence of a disturbance force such as gravity. During valve operation, the torque current Iq is changed while controlling the field current Id to zero, thereby realizing motor control with high power efficiency (control of Id=0).

JP, 2011-137537, A

However, when Id and Iq are switched as described above when shifting from the valve body driving state to the stop state, there is a problem that overshoot or damping vibration occurs when the valve body is stopped.

A vacuum valve according to a preferred embodiment of the present invention includes a valve body, a motor that opens and closes the valve body, and a torque current Iq is passed through the motor to drive and control the valve body. A control unit for controlling the holding of the valve body at an arbitrary opening position by supplying a magnetic current Id is provided, and the control unit once decreases the field current Id when the holding control is switched to the drive control. After that, the field current Id is continuously increased to the predetermined value with the lapse of time.
In a further preferred embodiment, an Id rising period is set at the end of the period in which the drive control is performed, and the control unit continuously increases the field current Id to the predetermined value during the Id rising period.
In a further preferred embodiment, the field current Id is controlled to be zero during the drive control period excluding the Id rising period, and the field current Id is controlled from the predetermined value to the torque current during the Id rising period. It is controlled to a value obtained by subtracting Iq.

According to the present invention, it is possible to reduce overshoot and damping vibration when the valve body is stopped.

FIG. 1 is a diagram showing a schematic configuration of a vacuum system including a vacuum valve. FIG. 2 is a plan view of the vacuum valve. FIG. 3 is a block diagram showing an example of the motor control device. FIG. 4 is a diagram illustrating an example of a motor. FIG. 5 is a diagram illustrating an inverter. FIG. 6 is a diagram illustrating an example of conventional valve control. FIG. 7 is a diagram showing an example of valve control in the present embodiment. FIG. 8 is a diagram showing another example of valve control in the present embodiment.

Hereinafter, an embodiment for carrying out the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of a vacuum system including a vacuum valve 1 in the present embodiment. The vacuum valve 1 is provided between the chamber 2 and the vacuum pump 3 of the vacuum device. The vacuum pump 3 evacuates the chamber 2 via the vacuum valve 1. The vacuum valve 1 includes a valve plate 11 that is a valve body, a motor 12 that swings and drives the valve plate 11, and a motor control device 13 that drives and controls the motor 12. As the motor 12, for example, a stepping motor is used.

FIG. 2 is a plan view of the vacuum valve 1 viewed from the chamber 2 side. A valve body 14 that is a housing that houses the valve plate 11 is formed with a flange 14 a that is connected to the chamber 2. When the valve plate 11 is rockably driven by the motor 12, the valve plate 11 is horizontally slid and driven to open and close the valve. The valve plate 11 can be slidably moved to an arbitrary position between a full blocking position C2 that faces the entire opening of the flange 14a and a full open position C1 that does not face the flange opening at all.

The opening/closing position of the valve plate 11 is represented by a parameter called an opening. The opening degree is a ratio=(the swing angle of the valve plate):(the swing angle from the fully open position C1 to the fully closed position C2) expressed as a percentage. The full blocking position C2 in FIG. 2 has an opening of 0%, and the full open position C1 has an opening of 100%. That is, the conductance of the vacuum valve 1 is controlled by adjusting the opening of the valve plate 11.

FIG. 3 is a block diagram showing an example of the motor control device 13. The motor control device 13 includes a current sensor 131, an inverter 132, a PWM signal generation unit 133, a dq-αβ conversion unit 134, a two-phase current conversion unit 135, and a speed/position control unit 136. The motor 12 has an absolute value encoder using a magnet as the encoder 121. The motor rotation position θm detected by the encoder 121 is input to the speed/position control unit 136. By detecting the magnetic pole position of the motor 12, the motor control device 13 can separately control the q-axis, which is the operation in the rotation direction, and the d-axis, which is the holding direction.

A target opening degree (hereinafter referred to as an opening degree instruction value) θs for moving the valve plate 11 is input to the speed/position control unit 136. The speed/position control unit 136 performs PID control using the opening degree θr (hereinafter, referred to as an opening degree measurement value) of the valve plate 11 and the opening degree command value θs based on the motor rotation position θm that is feedback-input, A torque current Iq and a field current Id to be passed through the motor 12 are calculated. The calculated torque current Iq and field current Id are input to the dq-αβ conversion unit 134 and converted into the two-phase currents Iα and Iβ by the dq-αβ conversion unit 134.

The current flowing in the motor 12 is detected by the current sensor 131 and converted into the two-phase currents Iαr and Iβr by the two-phase current converter 135. The two-phase currents Iαr and Iβr are fed back to the PWM signal generator 133. The PWM signal generation unit 133 outputs a PWM switching signal for switching each switching element of the inverter 132 based on the two-phase currents Iαr, Iβr and the two-phase currents Iα, Iβ input from the dq-αβ conversion unit 134. To generate. The inverter 132 performs a switching operation based on the PWM switching signal from the PWM signal generation unit 133 to supply a desired current to the motor 12.

FIG. 4 is a diagram illustrating an example of the motor 12. In this embodiment, a stepping motor is used as the motor 12. In the example shown in FIG. 4, a two-phase hybrid (HB) type stepping motor is used, and a plurality of stator coils 124A and 124B are arranged around the rotor 122.

For example, in the case of a two-phase eight-pole motor, eight coils are arranged such as A phase (+), B phase (+), A phase (-), B phase (-).... Furthermore, the A-phase (-) coil is a reverse winding of the A-phase (+), and the A-phase (+) and A-phase are connected to the two bridge circuits to be described later in a bipolar connection. The coils of each pole are wired between (-), B-phase (+), and B-phase (-).

The rotor 122 has a structure in which both axial ends of a permanent magnet magnetized in the axial direction NS are sandwiched between two rotor cores 122a and 122b. A plurality of small teeth 123 are formed on the outer circumference of each rotor core 122a, 122b. The small teeth of the two rotor cores are formed with a 1/2 pitch offset.

The inverter 132 of FIG. 3 is provided with a full bridge circuit using four switching elements for each phase coil. FIG. 5 is a diagram showing the configuration of the full bridge circuit. FIG. 5 shows a diagram in which the coil in which the pole coils for the A phase are wired is again used as the A phase coil, and the coil in which the pole coils for the B phase are wired is again connected to the full bridge circuits 132A and 132B as the B phase coils. It was

Transistors, IGBTs or the like are used for the switching elements S1 to S4 of the full bridge circuits 132A and 132B, and the diodes D1 to D4 are connected in parallel to the switching elements S1 to S4. ON/OFF control of the switching elements S1 to S4 of the inverter 132 is performed by the switching signal from the PWM signal generating unit 133, so that each phase coil is energized.

The basic step angle θsm of such a stepping motor is given by θsm=180/mNr (deg). In addition, m is the number of phases of the stator, and Nr is the number of small teeth of the rotor. Since the motor 12 has two phases and Nr=50 is set, θsm=1.8 (deg).

(Conventional valve control)
By the way, when changing the valve plate from the first opening θ1 to the second opening θ2, it is common to control the field current Id and the torque current Iq as shown in FIG. Further, FIG. 6B is a diagram showing the transition of the opening degree of the valve plate 11 when the field current Id and the torque current Iq are changed as shown in FIG. 6A.

In FIG. 6A, the line L11 indicates the field current Id, and the line L12 indicates the torque current Iq. The valve control state is a holding state in which the valve plate 11 is held at the opening θ1 when t<t1, and a driving state in which the valve plate 11 is moved from the opening θ1 to the opening θ2 when t1≦t≦t2, and t2< At t, the valve plate 11 is held at the opening θ2. Further, in FIG. 6B, a line L21 shows a transition of the opening degree command value θs, and a line L22 shows a measured opening degree value of the valve plate 11 calculated from the motor rotation position θm detected by the encoder 121. The transition of θr is shown.

When t<t1, the opening command value θs is θs=θ1, the motor current is controlled to Id=I1, Iq=0, and the valve plate 11 is held at the opening θ1. The current I1 is a holding current for holding the valve plate 11 at an arbitrary opening position. When the opening command value θs is changed from θ1 to θ2 at t=t2, the speed/position control unit 136 of the motor control device 13 switches the field current Id and the torque current Iq to Id=0 and Iq=I2. As a result, the opening degree measurement value θr of the valve plate 11 increases with the passage of time.

When the deviation Δθ=θ2−θr becomes small to some extent, the torque current Iq is gradually decreased like the line L12 in order to reduce the drive speed of the valve plate 11. When the deviation Δθ becomes smaller and becomes equal to or smaller than the threshold Δθth (time t2), the field current Id and the torque current Iq are switched to Id=I1 and Iq=0 to hold the valve plate 11 at the position of the opening θ2. Transfer to control. At this time, in the state of Iq=0, the field current Id changes stepwise, that is, discontinuously and instantaneously to the holding current I1, so that the rotor 122 of the motor 12 suddenly moves to the rotational position corresponding to the opening θ2. Therefore, there is a problem that the valve plate 11 overshoots due to inertia and the valve plate 11 damps and vibrates before and after the opening θ2.

(Valve control of the present embodiment)
FIG. 7 is a diagram showing an example of valve control according to the present embodiment. FIG. 7A shows changes in the field current Id and the torque current Iq, as in the case of FIG. 6A. FIG. 7B shows the transition of the opening degree of the valve plate 11 as in the case of FIG. 6B. The line L31 shows the field current Id, and the line L32 shows the torque current Iq. Further, line L41 in FIG. 7B shows the transition of the opening degree command value θs, and line L42 shows the transition of the opening degree measurement value θr.

As described above, when the drive control is switched to the holding control, the field current Id is rapidly increased in a stepwise manner, so that an overshoot of the opening occurs. Therefore, in the present embodiment, as shown in FIG. 7, when the holding control is switched to the drive control, the field current Id is temporarily reduced, and thereafter, the field current Id is gradually changed before switching from the drive control to the holding control. That is, it was made to increase continuously with the passage of time. The gradually increasing field current Id becomes Id=I1 when the drive control is switched to the holding control.

In the example shown in FIG. 7A, Id=(holding current I1)-Iq is set for the torque current Iq calculated by the PID control, and the lower limit value of the field current Id is set to zero. That is, Id=0 is set in the range of Iq>I1, and the field current Id is continuously supplied in the Id rising period (t3≦t≦t2) set at the end (Iq≦I1) of the period in which the drive control is performed. The holding current I1 is increased. Here, the time when Iq=I1 is set to t3, and at time t2, Iq=0 and Id=I1, and at that time, the drive control is switched to the holding control.

Since the torque current Iq is set to a large value (Iq=I2) for some time after the start of the drive control, the valve plate 11 is driven at a high speed. At this time, since Id=0 is set, the motor control is highly power efficient. After that, when the measured opening degree θr approaches the target opening θ2, the torque current Iq is reduced, and the speed of the valve plate 11 is gradually reduced. At this time, the field current Id gradually increases from Id=0 and becomes Id=I1 at t2.

In the example shown in FIG. 6, the field current Id instantaneously rises stepwise at the time t2, so overshoot and damping oscillation occurred. However, in FIG. 7A, the field current Id increases with time. Since the field current Id is gradually increased by continuously increasing the current Id, it is possible to prevent the rotor 122 from being suddenly attracted to the rotational position corresponding to the opening degree θ2, and it is possible to prevent the conventional overcurrent. It is possible to prevent the chute and the damping vibration of the valve plate 11.

As the control mode of the field current Id, various modes can be used as long as the field current Id is once reduced and then continuously increased with the passage of time when the holding control is switched to the drive control. Is possible. For example, as in the case of FIG. 7A, as a control mode in which the Id rising period is set at the end of the period in which the drive control is performed, the Id rising period is set to increase linearly as indicated by line L51 in FIG. May be. In this case, t4≦t≦t2 is the Id rising period, and the field current Id is controlled as Id={I1/(t2-t4)}·(t-t4) when t4≦t<t2. ..

Alternatively, as indicated by line L52 in FIG. 8, the field current Id may be once set to Id=0 at time t1 and then gradually increased to set Id=I1. Further, as indicated by line L53 in FIG. 8, the amount of decrease in Id at time t1 is set smaller than that in the case of line L52, and the field current Id is gradually increased after setting Id=I3 at time t1. Good (0<I3<I1).

Although various embodiments and modifications have been described above, the present invention is not limited to these contents. Other modes that are conceivable within the scope of the technical idea of the present invention are also included within the scope of the present invention. For example, in the above-described embodiment, the case where the motor 12 is the stepping motor has been described as an example, but the present invention is applicable not only to the case of the stepping motor.

DESCRIPTION OF SYMBOLS 1... Vacuum valve, 3... Vacuum pump, 11... Valve plate, 12... Motor, 13... Motor control device, 121... Encoder, 131... Current sensor, 132... Inverter, I1... Holding current, Id... Field current, Iq … Torque current

Claims (3)

Valve body,
A motor for opening and closing the valve body,
The motor is supplied with a torque current Iq to drive and control the valve body, and the motor is supplied with a field current Id of a predetermined value to control the valve body to be held at an arbitrary opening position.
When the control is switched from the holding control to the drive control, the control unit temporarily reduces the field current Id and then continuously increases the field current Id to the predetermined value with the lapse of time. valve. The vacuum valve according to claim 1,
An Id rising period is set at the end of the period in which the drive control is performed,
The said control part is a vacuum valve which raises the field current Id to the said predetermined value continuously during the said Id raising period. The vacuum valve according to claim 2,
The field current Id is controlled so that the field current Id is zero during the drive control period excluding the Id rising period, and has a value obtained by subtracting the torque current Iq from the predetermined value during the Id rising period. Vacuum valve controlled.

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