JPS5863890A - Control rod drive mechanism - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control rod drive mechanism in which the electrical wiring to the drive section is improved with a spring cable portion that is extendable and retractable.

In the control rod drive mechanism, the drive shaft requires a stroke of approximately 1 m in the vertical direction in order to insert or withdraw the control rod 4111 from the reactor core. Electrical wiring to the drive unit is generally done using a spring cable formed into a coiled shape so that it can be expanded and contracted.

FIG. 1 shows a longitudinal sectional view of a conventional control rod drive mechanism, in which 1 is a drive motor, 2 is an 11 drive gear train, and 3 is a pair of ball screws, which are combined with a ball putty 4 in one system. 5
6 is a position detector that detects the rotation speed of the drive motor 1;
is a spring cable, 7&: I° is a two-part flange at - where the spring cable 6 is taken, and l
kl: :l nectarf on Ti1s flange 7.

Lug 9 is attached. 8 Lower part 7 langes to which VJ ball nut 4 is fixed, 10 t:I', il□ Drive mechanism section consisting of the drive extension shaft of control salary 11, scram mechanism, etc., 12 is built-in each of the parts listed in 2...Ujiknob, 13
is the control rod guide tube.

In the structure shown in Figure 1, 1. The rotation of the drive motor rotates the ball screw shaft 3 via the drive gear train 2. The ball nut 4 engaged with the ball screw shaft 3 is located at the lower part 7.
Since it is fixed to the flange 8, the lower flange 8 is driven vertically by 30 rotations of the ball screw shaft. The drive mechanism section 10 requires a large number of electrical wiring such as a motor for gripping and releasing the control rod 11, a position detection switch, etc., power lines, signal lines, etc., and a spring cable 6 is passed through the connector plug 9 to the lower flange. Electrical wiring is connected below 8.

The lower flange 8 is thus driven by the drive motor 1 and moves up and down, and the spring cable 6 is expanded and contracted accordingly. Conventionally, the elasticity of the spring cable 6 itself is fully utilized to bring the entire spring into its free position in the contracted state as shown in FIG.
A spring cable was used that could be stretched by the amount that the -o-ri was actuated. However, since the spring cable 6 is composed of an insulating coating made of synthetic resin or the like and an electric conductor made of copper wire, it has a spring effect and is not very promising. - Since the control drive mechanism undergoes thousands of strokes, it must be maintained accordingly. And the ambient temperature is 60? When the temperature exceeds r, the spring cable loses its elasticity, and the fourth
As shown in the figure: The cable itself looks downwards at IJI.
L'i' calculation occurs.

In this state, when the T-flange I3 moves -1-1, the spring cable 6 collapses laterally 71. Ball screw I groan 3
or the spring cable itself may be damaged.

Disconnection, poor insulation, etc. may occur, which may lead to problems.

As a countermeasure, a steel spring 14 having a cross section shown in Fig. 6 is used.
A spring cable with a spring was considered in which the spring cable 6 was wound together with the spring cable 6. [・1・j, FIG. 6 is a sectional view taken along the line ■-■ in FIG. 5. In Fig. 6, 15 is an electrical conductor made of copper wire, 16 is an insulator made of synthetic resin, etc., and is integrated with the spring 14 by a deso 17, and the elasticity of the spring cable is imparted to the steel spring 14. It is maintained. However, since the stroke is as large as 1,000 m, it is difficult to manufacture a spring that stretches so much because the bending stress exceeds the limit when considering the diameter and free length.

Therefore, as shown in Fig. 5, an attempt was made to halve the spring stress of extension L and contraction A/(stroke L = t + A', 227) by making the intermediate position of the stroke fully free. It was done. The spring 14 does not fall sideways even if it is not particularly guided in the direction in which it extends from the free position. However, when compressed, the spring has a large number of turns and a long stroke, so it buckles and shifts laterally as shown in FIG. Therefore, it may come into contact with the ball screw shaft 3 and be damaged, which is not desirable. As a means to solve these problems, there is a telescopic mechanism that can extend and contract like a telescope, but it has a complicated structure and is not suitable for reliability as a nuclear reactor equipment. It is also possible to consider a structure in which the flange is completely penetrated and guided, but in this case, the position detector 5 is on the upper side and the drive unit 41''η part 10 is connected on the lower side, so it is impossible due to the space. In addition, there has been a proposal to install a guide rod in the second part, but
The effect of completely preventing buckling of '71 is not so long ago.

The present invention was made in view of the above situation, and aims to provide a control rod drive mechanism that allows smooth expansion and contraction of a spring cable and prevents cable breakage and breakage accidents. .

The control rod drive machines W and Y of the present invention include a ball screw +++b driven by a drive motor installed in a cylindrical housing and fixed to two parts of the housing, and a ball screw +++b that is slidably inside the housing. A lower 7 lange driven through a ball nut screwed into the two-part ball screw shaft,
One end is fixed to the upper 7 langes fixed to the upper part of the housing and connected to the connector plug, and the other end is connected to the drive mechanism part that fully drives the control rod in the control rod guide tube. A spring cable fixed to the lower flange is provided, and has a predetermined length in the axial direction.
A guide tube is provided that is supported via an arm on a guide bush that loosely fits into the r2 ball screw.

An embodiment of the control rod drive mechanism of the present invention will be described below with reference to FIGS. 8 and 9, where the same parts as in FIGS. 1 to 7 are denoted by the same reference numerals and explanations of the same parts are omitted.

In the figure, a guide tube 18 has a predetermined length in the axial direction and is loosely fitted around the inner periphery of the spring cable 6 having the structure shown in FIG. A guide bushing 19 is loosely fitted onto the ball screw shaft 3, and the guide tube 18 is fixed to the guide bush 19 via an arm 20.

In the above structure, when the ball screw shaft 3 is rotationally driven by the drive motor 1 and the lower flange 8 rises, when the spring cable 6 shifts in the lateral direction and tries to displace, it hits the guide tube 8 and is stopped, 1 as shown in FIG. As shown, the spring cable 6 is smoothly prevented from being displaced in the lateral direction until it reaches its most contracted state.

The guide tube 18 comes in contact with multiple locations on the inner circumference of the spring cable 6' to prevent the spring cable 6 from falling down, thereby preventing cable breakage, breakage, etc., and prolonging the life of the spring cable and driving the control rod. The reliability of the mechanism can be improved. ll'il 1 spring cable 6
Since the guide tube 18 has four built-in springs, the guide tube 18 is located in the middle.

There are many parts inside the housing.
! (Although it is located at fill f in this example,
illll rod drive machine lateral drive mechanism is 11 (1
The arm is fully valved and connected to the guide bushing, which is loosely fitted into the guide back spring cable having a predetermined length in the + direction and loosely attached to the ball screw.
It is possible to move the spring cable to 1°r, so that the spring cable can be reduced in the horizontal direction by 1°r/1'1. Therefore, cable breakage and breakage accidents can be prevented, the life of the cable can be extended, and the reliability of the control N111 rod drive mechanism can be improved. 11-1, Part 2 Example describes the case of a spring cable with a spring, but even with a structure without a spring, the guide tube tends to fall, but the same effect is obtained! , all have.

As described above, the control rod drive mechanism of the present invention enables the expansion and contraction of the spring cable to be performed in just 10 seconds, thereby completely preventing cable breakage and breakage, extending the life of the cable, and improving reliability. It has the effect that it can.

[Brief explanation of the drawing]

Figure 1 is a longitudinal sectional view of the spring cable arrangement part of a normal control rod drive mechanism, Figure 2 is an explanatory diagram of the spring cable in Figure 1 in an extended state, and Figure 3 is an explanatory diagram of the spring cable from the state in Figure 2. Figure 4 is an explanatory diagram of the state in which the spring cable of the conventional control rod drive device has lost its elasticity and is hanging down. Figure 5 is an illustration of the spring cable as a countermeasure to avoid the situation shown in Figure 4. 6 is an enlarged cross-sectional view of the Vl-■ arrow in FIG. 5, and FIG. 7 is the spring cable shown in FIG. 5 when the spring cable is contracted. FIG. 8 is a cross-sectional view of the control rod drive mechanism of the embodiment of the present invention when the spring cable is extended, and FIG. 9 is an explanatory view when the spring cable of FIG. 8 is contracted. 1... Drive motor, 3... Ball screw l11+,
4...Ball (9) Putt, 6...Sbring cable, 7...,
Upper flange, 8... Lower 7 flange, 9... Connector plug, 10... Drive mechanism pal (, II... Control rod, 12... Housing, 13... Control rod guide tube, 14...d: Hey, 18...guide tube, 19...
Guide bush, 20...arm. Agent Patent attorney Hiroo Nagasaki (and 1 other person) (IQ) Figure 5 Figure 6

Claims (1)

[Claims] 1. A ball screw shaft mounted in a cylindrical housing and driven by a drive motor fixed to the upper part of the housing, and a ball screw shaft slidably mounted in the housing. One end is fixed to the upper flange fixed to the upper part of the housing and connected to the connector plug, and the other end drives the control rod in the control rod guide tube. In the control rod drive mechanism, the control rod drive mechanism includes a spring cable connected to the drive mechanism section and fixed to the lower flange, the control rod drive mechanism having a predetermined length in the axial direction, loosely fitted in the spring cable, and connected to the ball screw shaft. A control rod drive mechanism characterized by having a guide tube supported via an arm on a loosely fitted guide bush. 2. The control rod drive mechanism according to claim 1, wherein the spring cable has a built-in spring.