JPH02221894A - Control rod driving device - Google Patents

Abstract

PURPOSE:To enable the ball screw and split ball nut of a driving shaft to properly engage each other by providing an absolute position detector for the driving shaft, and an absolute angle detector and a synchronous position setter for a rotor. CONSTITUTION:The absolute position detector 12 which detects the absolute position of the driving shaft 3 and the absolute angle detector 13 which detects the angle of rotation of the rotor 21 are connected to the synchronous position setter 30. The setter 30 is connected to the rotor 21 of a synchronous motor through a motor controller 31. The detector 12 detects how much the driving shaft 3 moves from a reference position and the detector 13 detects the current azimuth of the rotor 21. Then the setter 30 sets the angle of rotation of the ball nut up to the synchronous position according to the signals from the detectors 12 and 13 and supplies a command to the controller 31 to rotate the rotor, thereby determining the azimuth of the ball nut. In this state, an electromagnet is magnetized and the split ball nut and ball screw properly engage each other.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a control rod drive device for moving up and down control rods of a nuclear reactor.

[Prior Art] Conventional control rod drive devices include those shown in FIGS. 3 and 4 (see Japanese Patent Laid-Open No. 178694/1983).

In Fig. 3, 1 is the upper core mechanism in which the control rod drive mechanism (hereinafter abbreviated as CRDM) is installed, 2 is the upper guide tube of CRDM, and 3 is the drive shaft, which is not shown in the figure, but is equipped with a control rod at the lower end. The rods are connected, and by moving the drive shaft 3 up and down, the control rods can be withdrawn, inserted, or rapidly inserted to control the output of the reactor or bring about a rapid shutdown (scram). 10 is an electromagnet, 4 is an armature, and 5 is a ball. A connecting shaft 8 is attached to the armature 4, and the connecting shaft 8 passes through a pedestal 9 attached to the lower end of the rotor 21 of the motor. A driven ring 25 is suspended. A split ball nut 24 is attached to the driven ring 25 via a link 11, and the upper end of the split ball nut 24 is pivotally supported on the pedestal 9 by a pin 22. In addition, 20 is the stator of the motor,
26 is a ball screw carved into the drive shaft 3.

Then, the armature 4 is attracted by the electromagnet 10,
By opening, the connecting shaft 8 and the driven ring 25 move up and down, and the split ball nut 24 is opened and closed in the radial direction using the pin 22 as a fulcrum via the link 11, and the split ball nut 24 is attached to and removed from the ball screw 26. It looks like this. The left half of Fig. 3 and Fig. 4 (b) show the state in which the electromagnet is magnetized and the split ball nut 24 and the ball screw 26 are engaged, and the half shown in Fig. 3 and Fig. 4 (a) show the state in which the electromagnet is demagnetized. , shows a state in which the split ball nut 24 and the ball screw 26 are disengaged.

When current is applied to the stator 20 in the above magnetized state, the rotor 2
1 rotates, and the pedestal 9 attached to this rotates, and the split bod 5-
The lug nut 24, the link 11, the driven member 11, and the driven ring 25 are rotated simultaneously. Therefore, the drive shaft rises and a control rod (not shown) is pulled out.

Although the split ball nut 24 is divided into several sectors, it has the same function as a nut, so it can move the drive shaft 3 up and down. Note that the drive shaft 3 is provided with a rotation stopper (not shown).

In addition, when stopping the furnace quickly, when the electromagnet IO is demagnetized, the armature 4 and the driven ring 25 will fall.
The link 11 rotates, which causes the split ball nut 24
is separated from the ball screw 26, so the drive shaft 3 is inserted downward.

[Problems to be Solved by the Invention] However, in the above device, the drive shaft 3 expands and contracts due to the influence of the temperature of the furnace, and the rotor 21 of the motor has an uncertain rotational direction when stopping in an emergency. , electromagnet 1
0, if the ball row of the split ball nut 24 is in a position where it does not exactly engage with the ball screw 26 of the drive shaft 3 (FIG. 4(C)), the thread of the ball screw 26 or the ball nut 24 balls 14 and ball receiver 15
As a result, not only the efficiency of driving force transmission deteriorates and durability is lost, but also the device may become inoperable.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a control rod drive device in which the ball screw of the drive shaft and the split ball nut are synchronously engaged, that is, properly engaged. .

[Means for Solving the Problems] In order to achieve the above object, the present invention has a drive shaft in which a vertically slidable drive shaft with a ball screw groove is inserted into the rotor shaft of a motor and divided into two or more parts in the radial direction. The upper end of the split ball nut that rotates together with the rotor is pivoted at a predetermined position in the axial direction by a pin, the vicinity of the lower end is pivoted to one end of the link, and the other end of the link is moved up and down in the axial direction so that the pin becomes a fulcrum. In the control rod drive device, the divided ball nut is opened and closed in the radial direction to attach and detach the divided ball nut to the ball screw, an absolute position detector of the drive shaft, and an absolute angle detector of the rotor. and a synchronous position setting device that receives signals from each of these detectors and issues a signal instructing the motor controller to rotate the rotor so that the split ball nut and the ball screw are synchronized. A control rod drive device having a control rod drive device, and a drive shaft with a ball screw groove cut into it that can slide up and down inserted into the rotor shaft of the motor, divided into two or more parts in the radial direction, and a split ball nut that rotates together with the rotor. The upper end is pivoted at the same axial position by a pin, the vicinity of the lower end is pivoted to one end of the link, and the other end of the link is moved up and down in the axial direction to move the split ball nut in the radial direction using the pin as a fulcrum. In the control rod drive device, which is configured to open and close to attach and detach the split ball nut to and from the ball screw, there is provided a rod at the upper end of the drive shaft, which has the same pitch as the ball screw and whose outer diameter is greater than the outer diameter of the ball screw. An extension shaft is provided with a ratchet groove that is at least twice as large as the height of the groove, the ratchet groove is provided a plurality of pitches apart from the upper end of the drive shaft, and the split ball nut is attached to the lower end of the rotor. A ratchet brake is attached to the pedestal on which the upper end is pivotally supported, and the ratchet brake has a ratchet finger that has a claw at the tip that can engage with the ratchet groove and is biased perpendicularly to the extension shaft, and the other end of the link is moved up and down. When the electromagnet is demagnetized to disengage the split ball nut and the ball screw, the ratchet groove and the ratchet finger engage, magnetizing the electromagnet and disengaging the split ball nut and the ball screw. A control rod drive mechanism characterized in that the ratchet groove of the extension shaft and the pawl of the ratchet finger are configured to be disengaged from each other when the ratchet groove and the ratchet finger are engaged with each other, and The control rod drive mechanism according to claim 2, wherein the control rod drive mechanism is formed so that the contact angle of the control rod is approximately 90°.

[Function] In the first claim, the synchronous position setter sets the rotation angle of the ball nut to the synchronous position based on the signals from each detector, and gives a command to the motor controller to rotate the rotor. , position the orientation of the ball nut. If the electromagnet is magnetized in this state, the split ball nut and ball screw can be properly engaged.

In the second aspect, when the ratchet groove of the extension shaft and the pawl of the ratchet finger are engaged in advance, the vertical position of the drive shaft is adjusted and the positions of the ball screw and the split ball nut are synchronized.

[Example] Hereinafter, an example of the present invention will be described based on the drawings. Since the basic configuration is the same as the conventional example shown in FIG. The explanation will be omitted.

FIG. 1 shows an embodiment of the first claim of the present invention. In FIG. 1, 12 is an absolute position detector that detects the absolute position of the drive shaft 3, and 13 is an absolute position detector that detects the rotation angle of the rotor 21. These absolute angle detectors are each connected to a synchronous position setter 30. Further, this synchronous position setting device 30 is connected to a motor controller 3.
1 to the rotor 21 of the synchronous motor.

The absolute position detector 12 detects how far the drive shaft 3 has moved from the reference position, and the absolute angle detector 13 detects the current orientation of the rotor 21. Since the vertical position of the split ball nut 24 is fixed, the ball nut 24 and the ball screw 26 will synchronize, that is, exactly engage, by positioning the ball nut 24 in any direction relative to the current position of the drive shaft 3. It can be determined by calculation. The synchronous position setter 30 sets the split ball nut 2 to the synchronous position based on this data and the signals from each detector 12.13.
4 is set, a command is given to the motor controller 31 to rotate the rotor 21, and the orientation of the split ball nut 24 is determined. If the electromagnet 10 is magnetized in this state,
The split ball nut 24 and the ball screw 26 can be properly engaged. Next, an embodiment of the second aspect of the present invention will be described with reference to FIGS. 2(a) and 2(b). Drive shaft 3
An extension shaft 16 having a ratchet groove 32 extends from the upper end thereof. This ratchet groove 32 is formed to be an extension of the thread groove of the ball screw 26. In other words, each pitch is the same pitch p, and the distance between the grooves is L=np (where n is an integer). Also, the outer diameter of the ridge of the ratchet groove 32 is smaller than the outer diameter d of the ball screw 26. Increase the height by at least twice the height of the mountain S. In this embodiment, D=d+28. On the other hand, a spring holder 19 is attached to the pedestal 9 at the lower end of the rotor 21, and a ratchet finger 17 is attached horizontally to the spring holder 19 via a coil spring 18 to form a ratchet brake. is pressed into contact with the ratchet groove 32. This ratchet finger 17 includes an armature 4 and a driven ring 2.
A connecting shaft 8 with 5 passes through it in the vertical direction. Further, the connecting shaft 8 is provided with a hole 33 having a predetermined shape, through which a pin 35 attached to the ratchet finger 17 passes, and whose front surface is formed in a cam surface 34 . Therefore, the movement of the ratchet finger 17 is restricted by the hole 33 and the pin 35, and the tip of the pawl 17a does not cross the width S of the ratchet groove 32 and enter into the inside, and as shown in FIG. 2(b). When the connecting shaft 8 moves upward, the ratchet finger 17 is separated from the ratchet groove 32 by the action of the cam surface 34.

As a result, when the electromagnet 10 is magnetized and the armature 4 and the connecting shaft 8 are pulled up, the ratchet finger 17 is separated from the extension shaft 16, and when the electromagnet 10 is demagnetized, the armature 4 and the connecting shaft 8 are lowered and the ratchet finger 17 is moved away from the extension shaft 16.
is pressed against the extension shaft 16 side. However, as described above, the pawl 17a of the ratchet finger 17 does not go inward beyond the width S, so even if the drive shaft 3 is pulled up, it will not come into contact with the ball screw 26, and when the drive shaft 3 is lowered. When near the lower end, the two pawls 17a begin to come into contact with the ridges of the ratchet groove 32, and at the lower limit position of the drive shaft 3, the pawls 17a
is pressed against the crest of the ratchet groove 32.

If the motor is rotated at low torque in this state, when the simultaneously rotating pawl 17a matches the ratchet groove 32, rotational resistance increases and the rotation stops.

Therefore, if the motor is stopped and the electromagnet 10 is magnetized, the ball row of the split ball nut 24 and the thread groove of the ball screw 26 are in synchronized positions as a result of the vertical position of the drive shaft 3 being adjusted by the above operation. Therefore, it will engage properly. In addition,
At the same time as magnetizing the electromagnet 1o, the ratchet finger 1
7 is separated from the extension shaft 16, so the split ball nut 24
There is no problem with the subsequent rotational movement of the drive shaft 3. Also, when the drive shaft 3 is rapidly inserted from the upper limit position, the electromagnet 1O is demagnetized and the claw 17a protrudes from the inside, but does not come into contact with the ball screw 26. Therefore, the threads will not be damaged. However, there is a possibility that the threads of the ratchet groove 32 will impact the pawl 171 near the lower limit of the drive shaft 3, but in the control rod drive mechanism, the final stroke is about 150 mm. is considered a buffer stroke, and the deceleration is sufficiently reduced at this position, so there is no impact and the structural integrity can be maintained sufficiently.

FIG. 2(C) shows an embodiment of the third claim,
The ratchet groove 32a of the extension shaft 16 and the pawl 17b of the ratchet finger 17 that engages with the ratchet groove 32a are each formed so that the contact angle θ is close to 90°. As a result, even if an upward force is applied to the drive shaft 3 for some reason, a horizontal force that disengages the ratchet finger 17 is not generated, thereby preventing the control rod from flying out.

[Effects of the Invention] As described above, according to the present invention, the ball screw and split ball nut of the drive shaft are prevented from being damaged, so a stable operating condition is maintained, and reliability and durability are improved. improves. Further, by forming the ratchet groove and the claws of the ratchet fingers so that the contact angle thereof is around 90°, it is possible to prevent an accident of the control rod popping out after the reactor is shut down.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view showing an embodiment of the first claim of the present invention, FIG. 2(b) is a perspective view of the same ratchet brake, FIG. 2(C) is an enlarged sectional view of a main part showing an embodiment of the third claim, FIG. 3 is a longitudinal sectional view showing a conventional example, and FIG. Figure (a). (b) is a longitudinal sectional view of the main part of the conventional example, and Fig. 4 (C
) is an enlarged vertical sectional view showing a state of poor engagement between the ball screw and the ball nut. 3...drive shaft, 9...cradle,
10...Electromagnet, 11...Link, 1
2...Absolute position detector, 13...Absolute angle detector, 16...Extension axis, 17
...Ratchet finger a, 17b ... pawl, 21 ... rotor, ...
Pin, ... split ball nut, ... pole screw, ... synchronous position setting device 1. 32a...Ratchet groove.

Claims (3)

[Claims] (1) A vertically sliding drive shaft with a ball screw groove cut into it is inserted into the rotor shaft of the motor, and the upper end of the split ball nut, which is divided into two or more parts in the radial direction and rotates together with the rotor, is fixed in the axial direction. The split ball nut is opened and closed in the radial direction using the pin as a fulcrum by means of pivoting the lower end to one end of the link and moving the other end of the link up and down in the axial direction. In a control rod drive device in which a ball nut is attached to and detached from the ball screw, an absolute position detector of the drive shaft, an absolute angle detector of the rotor, and signals from each of these detectors are received to separate the divided balls. A control rod drive device, characterized in that the motor controller is provided with a synchronization position setting device that issues a signal to support the rotation angle of the rotor so that the nut and the ball screw are synchronized. (2) Insert the vertically slidable drive shaft with a ball screw groove into the rotor shaft of the motor, and place the upper end of the split ball nut, which is divided into two or more parts in the radial direction and rotates together with the rotor, at a predetermined axial position. The split ball nut is opened and closed in the radial direction using the pin as a fulcrum by means of pivoting the lower end to one end of the link and moving the other end of the link up and down in the axial direction. In a control rod drive device in which a nut is attached to and detached from the ball screw, a nut is attached to the upper end of the drive shaft at the same pitch as the ball screw.
and an extension shaft having a ratchet groove carved therein whose outer diameter is at least twice the height of the groove than the outer diameter of the ball screw, and the ratchet groove is provided a plurality of pitches apart from the upper end of the drive shaft, A ratchet brake is attached to the pedestal attached to the lower end of the rotor and on which the upper end of the split ball nut is pivotally supported, and in which a ratchet finger having a claw at the tip that can be engaged with the ratchet groove is biased perpendicularly to the extension shaft. When the split ball nut and the ball screw are disengaged by demagnetizing the electromagnet that moves the other end of the link up and down, the ratchet groove and the ratchet finger engage, and the electromagnet is attached. A control rod drive mechanism characterized in that when the split ball nut and the ball screw are magnetically engaged, the ratchet groove and the ratchet finger are disengaged from each other. (3) The control rod drive device according to claim 2, wherein the ratchet groove of the extension shaft and the claw of the ratchet finger are formed so that a contact angle thereof is around 90°.