JPH023666Y2 - - Google Patents

Description

[Detailed explanation of the idea]

This invention is a rack or frame mainly used for electronic communication equipment and information equipment.
This invention relates to a device that prevents malfunctions and damage to circuit elements caused by external noise in a group of electronic circuit modules installed in a system to form a system. First, conventional technology will be explained. The electronic circuits that make up the system are divided into blocks that have independent basic functions and are assembled on a single printed wiring board, and each block (called a module or unit; hereinafter referred to as a module) has a built-in power supply. Traditionally, it has been possible to construct a system that can be installed in a rack (9 in Figure 2) (this is called modularization) and use any type and number of modules as needed to construct a system with various functions. It is being done. For example, the CAMAC type module for measuring instrument interfaces, which will be described later, is a typical example and is used in various fields around the world. The typical form of the module is printed wiring board 1
A front panel 3 is attached to one end of the front panel as shown in FIG. 1, and screws 4 attached to the front panel are often used for easy mounting. One of the drawbacks of this modular system is that the constructed system is relatively vulnerable to external noise, and may cause malfunctions or malfunctions due to external noise such as electrostatic noise from a charged human body or jamming waves generated from other electronic devices. It is known that failures are likely to occur. However, in recent years, there has been a strong demand to improve the reliability of electronic circuits in order to solve these problems. This is because systems using electronic circuits are rapidly and widely used in industrial and consumer fields, and the damage caused by malfunctions and failures is becoming more serious and widespread.
The above drawbacks can be said to be serious drawbacks. The present invention aims to make a modular electronic circuit system strong against external noise and prevent breakdowns, malfunctions, and destruction of circuit elements, and will be explained below with reference to the drawings. First, a more specific configuration of a representative example of a conventional module and its operation against external noise will be explained. Fig. 1 is an external perspective view of a known CAMAC type module, Fig. 2 is an external perspective view of a rack with a built-in power supply to which the CAMAC type module is installed, and Fig. 3 is an external perspective view of the module installed in the rack shown in Fig. 2. FIG. The main part of the module is a printed wiring board 1 on which an electronic circuit is mounted, and in addition to this, there is also a metal rail (guide rail) 2 that reinforces this board, a surface panel 3 on which operating switches and lamps indicating the status of the circuit are attached, etc. The module is made up of fixing screws 4 that attach the module to a rack 9.
Power supply to the module and signal input/output connections are mainly performed by connecting a plug (a group of plug-in terminals) 5 to a connector 8. The rack 9 is provided with a groove 6 for inserting the module into a fixed position. After inserting the module along this groove 6, by tightening the fixing screw 4 to the fixing bar 7, the connector 8 and the plug 5 are connected. coupled and electrically connected. The system is constructed by attaching each mounting flange 11 of a plurality of racks 9 to the mounting column of the storage rack or the outer box 13 with screws, but generally the mounting column and the case 13 are kept at ground potential, and each rack 9 are connected to these 13 using conductors 12 and kept at ground potential. This measure of ensuring that the rack and its mounting parts are at ground potential is a basic requirement for protecting the system against extraneous noise and preventing malfunctions and damage to circuit elements. FIG. 4 is an explanatory diagram of a situation in which electrostatic noise N is added as external noise to a system constructed from the conventional module and rack 9 as described above. Electrostatic noise is mainly noise based on discharge that occurs when a charged human body touches the device, and most often discharge occurs on the front panel 3 when a person touches the device. Therefore, the situation in that case will be explained. Note that FIG. 4 shows the discharge path in this case with thick lines and arrows. Generally, when a human finger charged with several thousand volts due to static electricity touches the panel surface 3, the electric charge is rapidly discharged toward the ground, but there are two types of discharge paths, from the panel 3 to the fixing bar 7. The other is the one that flows from the panel 3 into the rack 9 along the ground wiring of the board 1 and the guide rail 2, and is discharged to the ground via the plug 5 and connector 8. In the former case, the discharge does not pass through the inside of the rack, so it has little negative effect on the internal electronic circuit, but in the latter case, an induced voltage is generated throughout the electronic circuit, which can have a large negative effect, causing malfunctions and damage to circuit elements. There is a possibility of a major accident. Furthermore, even if the former discharge path is taken, if the connection from the fixing bar 7 to the ground is not good, the voltage drop due to the discharge flow in the ground wire will instantaneously increase the potential of the entire rack 9.
Even if the panel 3 and the fixing screws 4 are in good contact, malfunctions and damage to circuit elements may occur. This modularized electronic circuit has the disadvantage of being susceptible to external noise, but this is due to the unstable electrical resistance of the path from the panel 3 to the fixing bar 7. This is thought to be because the electrical resistance to ground is also unstable. However, when the contact surfaces between the panel 3 and the bar 7 are clean and are brought into contact with sufficient pressure by the fixing screw 4, the electrical resistance between the panel 3 and the bar 7 is extremely low, and most of the discharge current passes through this path. Furthermore, if the connection between the fixing bar 7 and the ground is of sufficiently low resistance, there will be little variation in the potential across the rack 9, and the system will be extremely resistant to external noise. However, in actual conditions, dirt and dust are present at the contact portion between the panel 3 and the bar 7, and the contact resistance increases to a considerable value. In particular, if the surfaces are painted, the two will be insulated and slightly electrically contacted through the fixing screw 4. In such a case, the resistance value is large, and a considerable portion of the discharge current passes through the rack 9, making the system more or less adversely affected by external noise. Further, when the fixing screw 4 is loosened, the resistance value becomes significantly large, and most of the discharge current due to external noise flows inside the rack, greatly affecting the system. If the connection between the fixing bar 7 and the ground is made with a thin conductive wire, if there is dirt caught in the connection between the bar 7 and the ground, or if the surface of the panel or bar is painted and the connection is made through the mounting screws. In the above-mentioned case where they are connected, the electrical resistance is large, and the potential of the rack 9 will rise significantly due to discharge of electrostatic noise, resulting in malfunction or failure. From these considerations, in order to overcome the drawback of being susceptible to external noise, it is necessary to maintain electrical contact between the fixing bar 7 and the panel 3 with low resistance, regardless of the tightness of the fixing screws 4, presence of dust, presence of paint, etc. Try to keep the value
It is concluded that this can be achieved by keeping the contact resistance between the bar 7 and the grounding portion, that is, the mounting support or the outer box 13, sufficiently low. As a countermeasure for this, as shown in FIG. 5, an elastic contact leaf spring 10 is attached to the upper surface of the fixing bar 7, and this is brought into contact with the lower rail 2 of the module with pressure. There are ways to get good contact between the two. However, in this case, the module 1 must be inserted into the rack 9 while pressing down the contact spring 10, which has the disadvantage of making it difficult to attach and detach the module. is added to the module, so
If excessive force is applied to the joint between the panel 3 and the rail 2, the joint will be deformed and the dimensions will be out of order, which is a fatal problem. Therefore, the simple addition of such a contact spring 10 does not eliminate the drawbacks. The present invention eliminates these drawbacks and provides a system using a modularized electronic circuit that is resistant to external noise, and will be described in detail below. FIG. 6 shows a side view A and a perspective view B of an example in which the contact spring 14 is attached to the surface of the fixed bar 7 having a substantially rectangular cross section, in which the present invention is implemented, and the module is attached as in FIG. This shows the shape of the spring when it is not in use. The contact spring 14 is made of a plate of a highly elastic spring material such as phosphor bronze, and the portion 14a that contacts the panel 3 is formed into a convex surface as shown in the figure, and the portion 14b that contacts the upper surface of the fixing bar 7 is flat. It is characterized by keeping it as 14
Part b is smooth and contact spring 1 when inserting the module.
There is no need to compress 4. Therefore, no excessive force is applied to the module. 4' is a hole for screw 4. Further, the spring plate 14 is actually slightly bent at the bottom and rear surface of the bar 7 as shown in FIG. 6A. FIG. 7 is a side sectional view showing a state in which the module is mounted on the rack 9, and the convex surface 14a of the contact spring deforms into a flat shape as the front panel 3 is tightened to the fixing bar 7 with the fixing screw 4. do. As a result, the flat portion 14b of the contact spring that was in contact with the upper side of the fixing bar 7 lifts up and comes into contact with the rail 2 with sufficient pressure, achieving good contact with low electrical resistance. Rail 2 and contact spring 1
4, since the modules rub against each other when inserted, dirt and dust present on the surface of the spring are automatically removed and do not interfere with electrical contact at all. Moreover, this state does not change even if the fixing screw 4 loosens to some extent because the electrical contact does not depend on the screw 4. To remove the module from the rack, the fixing screw 4 is loosened, so that the convex surface 14a of the contact spring 14 returns to its convex shape, and the flat surface 14b returns to the position in contact with the upper surface of the fixing bar 7. Therefore, module extraction is also carried out smoothly. The entire fixing bar 7 actually has 25 springs 14, each made of a single spring plate that is partially connected to such an extent that each spring can be bent and stretched fairly freely. With the above configuration, the module can be mounted with good contact regardless of the presence of dirt or dust, the presence or absence of painting on the surface panel 3, the loosening of the fixing screws 4, etc., and the discharge current caused by external noise. Most of the discharge current flows from the panel 3 to the fixing bar 7 via the contact spring 14, and the amount of discharge current passing through the inside of the rack 9 is extremely small. In addition, the contact surface between the fixing bar 7 and the mounting flange 11 is made to have a large area to be a good electrical conductor, and screw holes are made in the end face of the fixing bar 7, and the module panel and the bar are fixed with screws 4. By making the contact surface between the mounting flange 11 and its mounting post or outer box 13 a good electrical conductor, the discharge current due to external noise will flow through an extremely low resistance path to the mounting post or outer box 13. Therefore, fluctuations in the ground potential of the rack 9 as a whole are extremely small. The above explanation is based on the case where electrostatic noise is added, but the adverse effects caused by radio interference are also caused by the fact that the potential of the outer walls of the rack 9, panel 3, etc. fluctuates due to the radio waves. Therefore, this problem can also be solved by implementing the above-mentioned electrostatic noise countermeasures. FIG. 8 is a perspective view of an example of a panel implementing the present invention. When CAMAC type modules are installed in such a rack, the grounding circuit of each module is always maintained in good electrical continuity with the rack 9 and its mounting support or outer box 13, which eliminates the grounding that was previously required. The conductor 12 is no longer necessary. The following table shows the experimental results of the limit of malfunction due to electrostatic noise, demonstrating the effectiveness of the present invention. In this experiment, the module was mounted on a conventional rack as shown in Fig. 2 with the fixing screw 4 loosened and the contact resistance large, and the fixing bar 7, the mounting flange 11, the mounting column or the outer box 13 were connected to each other. is screw 4 regardless of surface contact.
Electrostatic noise was applied to the surface of the panel 3 when the present invention was applied.

[Table] As shown in this table, the improvement ratio of the present invention reached 50 times, proving that the present invention has an extremely large effect. As explained above, although the present invention has a simple configuration, its effects are remarkable; it greatly improves the negative effects of external noise, prevents malfunctions and component damage, and improves system performance. The practical effect of increasing reliability is obvious.

[Brief explanation of the drawing]

Figure 1 is a perspective view of the structure of the module, Figure 2 is a perspective view of the rack on which the module shown in Figure 1 is installed, Figure 3 is a side sectional view of the module installed on the rack, and Figure 4 is an external perspective view of the module. Figure 5 shows an example of how a contact spring is used, Figure 6 shows an example of how the contact spring of the present invention is installed, and Figure 7 shows how the module is installed when using the contact spring of the present invention. The sectional view, FIG. 8, is a perspective view of a rack implementing the present invention. 1...Printed wiring board, 2...Rail, 3...Surface panel, 4...Fixing screw, 5...Plug part, 6
... Guide groove, 7 ... Fixing bar, 8 ... Connector, 9 ... Rack, 10 ... Contact spring, 11 ...
Mounting flange, 12...Grounding conductor, 13...Mounting column or outer box, 14...Contact spring.

Claims (1)

[Scope of utility model registration request] A storage rack is equipped with multiple modules (modular electronic circuits) consisting of a printed wiring board for electronic circuits, guide rails attached to each side of the top and bottom, a surface panel at one end of the board, a terminal board plug, etc. In a system formed by inserting each module along the groove and connecting them to the connectors of the rack, a rectangular bar is bent to cover the front and top surfaces of each module on the front of the rack for fixing each module and keeping it at ground potential. Before the module is mounted on the rack, the front surface of the elastic leaf spring is curved in a convex shape, and it lies flat on the top surface of the bar, but when the module is mounted on the rack, the convex part is attached to the front panel of each module for the above-mentioned fixing purpose. By screwing in the bar fixing screws, the module is forcibly brought into surface contact with the back surface of the panel, and as the bar becomes flat, the upper surface of the bar is lifted upward by the spring elasticity, and pressure is applied to the guide rails of each module. A device for preventing external noise from entering easily mounted modules, characterized in that they are mounted so that they touch each other.