Design and manufacture of automatic feed structure

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Design and manufacture of automatic feed structure of brake drum boring machine

automobile brake drum is one of the parts of automobile brake system. Before installation, the working surface shall be positioned and bored to reduce the form and position error after installation. The author designed and manufactured a simple brake drum boring machine together with the repair factory of Baoji No. 1 automobile transportation company, which has achieved good results. This paper mainly introduces the design principle of the automatic feed structure of the machine

1 principle

the principle of involute planetary transmission with small tooth difference is a meshing transmission that uses involute internal gear and external gear to make the tooth number difference between 1 and 3. Its meshing process is shown in Figure 1a), the internal gear B is fixed, and the planetary gear G is installed on the eccentric shaft (tie rod h). When the tie rod h rotates, the teeth of the planetary gear g and the teeth of the internal gear B mesh in turn. When the tie rod h rotates for one cycle, because the planetary gear has one (or several) fewer teeth than the internal gear, the planetary gear cannot be restored to the initial meshing position, and one (or several) teeth are missed for meshing. This is equivalent to that the planetary gear has turned one tooth in the opposite direction by an angle of 2 π/zg. If ZB zg=z, the planetary gear has turned 2 in the opposite direction × 2 π/zg angle, and so on

Fig. 1 involute planetary transmission with small tooth difference and external meshing differential principle

2 mechanism deformation

planetary transmission with small tooth difference is widely used in engineering. This mechanism is generally in the form of internal meshing transmission. When designing the feed mechanism of the simple automobile brake drum boring machine, I used the differential principle of the mechanism, and the specific structure adopted the external meshing transmission form. The principle is shown in Figure 1b): gear K and tooth 1 film blowing machine with good performance showed good market adaptability in the process of film production. The diameter of wheel 2 is the same, but gear K has one more tooth than gear 2, and K is fixedly connected with the screw nut, The nut and K can rotate in the semicircle frame plate 1 (see Figure 2); The gear 2 and the screw rod are connected by a guide flat key. When the handle is pulled out, the end face key of shaft 9 is connected with the gear. At this time, gear 10 is meshed with gear K and gear 2 at the same time. Since the gear K has one more tooth than the gear 2, the two gears are staggered by one tooth thickness every revolution. When ZK turns (zk is the number of teeth of the gear K), the screw nut rotates on the screw rod for one revolution. In this way, the screw rod pushes the large cutter head 5 forward by one pitch. If the handle is pushed in, the gear 10 is separated from the end face key of the shaft 9, the gear does not rotate, and the feed movement stops

1. Semicircle frame plate 2 Connecting lead screw gear 3 Lead screw 4 Support 5 Large knife table 6 Knife holder 7 Tool cartridge 8 Spindle end cap 9 Shaft 10 Input the feed movement gear 11 Pulley 12 Box 13 Electrical box 14 Base 15 Motor

Figure 2 simple automobile brake drum boring machine

3 the higher the machine structure is The calculation formula is: ha=100- l/0.025

see Figure 2

1) overall structure

this machine is composed of base 1. At present, the hydraulic universal testing machine produced by this enterprise includes: digital display hydraulic universal testing machine, screen display hydraulic universal testing machine, microcomputer controlled electro-hydraulic servo hydraulic universal testing machine 3 and 4, box 12, tool table and automatic tool walking mechanism, electrical control box 13, etc. When the machine is started, the motor 15 will input the movement into the box 12 through the belt pulley 11. After two-stage deceleration, it will be output by the main shaft 8 in May 1999. The front end of the main shaft 8 is threaded, and the special front and rear conical blocks are installed. The brake drum installed on the flange can be pressed on the main shaft by tightening the nut, and the front and rear conical blocks play a centering role

2) screw feed

the tool feed system of the machine adopts the form opposite to the traditional screw feed mother structure, that is, the way of screw feed. The most important feature of this method is its simple structure, which omits the complex control mechanism in the wire feeding mother structure, which is necessary for the automobile repair shop with limited machining capacity

4 control features

the operator will install the brake drum to be processed, set the tool, and pull out the handle to automatically carry out boring. After the brake drum is bored, the limit switch will stop automatically and the buzzer will tell. The machine can quickly manually retract the tool: there is a square handle at the end of the screw rod. When retracting the tool, insert the handle and swing it back to the big knife in reverse. The production capacity of lithium battery related materials can be gradually transferred to China and the technology of domestic leading enterprises can be continuously improved

5 several problems

1) the role of axial force

in order to reduce the friction between gear K, gear 2 and support caused by boring axial force, the machine is equipped with end bearing or brass spacer at the above two places

2) select the modified gear

theoretically, two gears with different tooth numbers mesh with one gear at the same time on the same shaft. If the standard gear is still used, interference will occur. Therefore, the modified gear should be selected

3) influence of tooth number difference on machined surface roughness

as mentioned above, gear K and gear 2 miss an angle of tooth thickness each other every revolution, that is, 2 π/zk. If the tooth number difference △ z=zk-z2=z, KK, the two wheels miss each other by 2 × 2 π/zk angle, and so on. It is not difficult to see that the greater the value of △ Z, the greater the feed amount and the roughness of the machined surface. This is one of the reasons why the number of teeth difference of this machine is 1. (end)

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