Design of special fixture for automatic measurement of resistance of auto ignition wire*

Hua－ru YAN，Fang CHEN，Wei DU2 Department of Mechanical Engineering，Henan Mechanical and Electrical Engineering College，Xinxiang 453003，China;

2 Henan University of Science and Technology，Luoyang 471003，China

Design of special fixture for automatic measurement of resistance of auto ignition wire*

Hua－ru YAN†1，Fang CHEN1，Wei DU21Department of Mechanical Engineering，Henan Mechanical and Electrical Engineering College，Xinxiang 453003，China;

2Henan University of Science and Technology，Luoyang 471003，China

Resistance of auto ignition w ire，which is an im portant parameter of the factory inspection，affects the performance of engine ignition directly.Formeeting the demand of large scale production and automatic measurement，a special fixture to measure the resistance value of auto ignition w ire is designed from join shape ofauto ignition w ire in the paper.W ith easy operation，it can rapid ly assem ble and disassem ble，and is centralized outcome of optical-mechanic-pneumatic.Through practicaloperation，it reduces labor intensity of operator，saves unnecessary labor，and im proves measuring efficiency and automation level.It is very good for popularization.

Special fixture，Auto ignition w ire，Resistance，Automatic measurement

*Project supported by Natural Science Research Project of Henan Province Department of Education(2011B460006)

† Hua－ru YAN，E－mail:huaru6@163.com

1.Introduction

Generally，there are four auto ignition wireswith different length in electronic spark control system of auto engine，whose resistance value is also different from each other，and generally 2～10 kΩ.The value affects the performance of engine ignition directly，so it is a very important parameter and has to pass strict inspection before it leaves factory.Nowadays，automatic measurement system of resistance of automotive ignition wire is largely absent at home，and the generalway is to use amultimeter and a buzzer formanualmeasurement，which is very inefficient.With the rapid development of automaticmeasurement technology and the increasing enlargement of production［1－2］，it is urgent to meet the demand of effective and automatic measurement.According to join shape of auto ignition wire and operation requirements of automation system［3 －5］，a special fixture，which can coordinatewith automation system to realize rapid measurement in a cooperation project with enterprise in 2012，is designed，and which has passed provincial－level projects appraisement now.

2.The basic situation of the special fixture in automatic measurement system of resistance

2.1.The configuration of the special fixture in system

The external configuration of the whole system is shown in Figure 1.The special fixture consists of distributor module 4，clip module 3 and spark plug module 1.According to different length of four auto ignition wires，themodules are fixed on workbench 6 that ismade from aluminium plate.Inside distributor module and spark plug module，there are copper probes to connect auto ignition wire tomeasuring circuit.Between distributor module 4 and spark plug module 1，clip module 3 is a set，which contains photoelectric mechanism and pneumatic mechanism.The control button 5 can control start and stop of the measuring.Themeasuring and controlling device 8 is installed in thewall box of the back of LCD 9，which contains themain hardware circuit and a single chip microcomputer as core.The small keyboard 7 is used to set basic parameters of themeasuring system.

Figure 1.External configuration of system

Themajor role of clipmodule 3 is to create automatic signal for automaticmeasuring system，which is the core of the special fixture.Pressure clamp，used in the clipmodule 3，a high elasticity of rubber product，is obtained by direct buying.The four arc grooves are good for pressing 4 auto ignition wires.

2.2.The workflow of the special fixture in system

The workflow of the special fixture in system is:first，the two ends of four auto ignition wires are respectively connected to measuring circuit:one end is connected with distributor module，the other end is connected with spark plug module.Secondly，using pressure clamp，themiddle of four auto ignition wires can be pushed into the clip module，which can be detected by photoelectric mechanism of clip module，and a position signal(INPOS signal)is generated and transferred to controlling system.Thirdly，when the single chip microcomputer of control system receives the INPOS signal，the electromagnetic valve is opened and pneumatic mechanism is drived to lock wire harness，then a locking signal is generated to control system.Fourthly，when the single chip microcomputer receives the locking signal and the start button is pressed，the measuring programs is started to measure resistance value，then the measuring results，four groups ofwire numbers and the respective resistance value are displayed on the LCD panel.Lastly，after pressing stop button，the electromagnetic valve is switched and pneumatic mechanism is reset to loosened locked wire harness.Thus，themeasuring is end.

3.Specific structure of the special fixture

3.1.Specific structure of the spark p lug module

According to structure dimensions of spark－plug terminal of auto ignition wire，the spark plugmodule is designed，which consists of four same spark plug units.As shown in Figure 2，each of them consists of 16 parts.As amain part，copper probe 9 is installed in insulated sleeve 5 to achieve insulation.Because spring 7 is placed around the left－hand side of probe 9，probe 9 can keep a trend of a movement to the right，which can make reliable connection between probe 9 and spark－plug terminal of measured wire.There is an aperture on the leftend of probe9，which is designed to connect probe 9 tomeasuring circuit.

Figure 2.Structural drawing of spark plug unit

3.2.Specific structure of the distributor module

According to structure dimensions of distributor terminal of auto ignition wire，the distributormodule is designed，which consists of four same distributor units.As shown in Figure 3，each of them consists of 8 parts.Like internal structure of spark plug unit，copper probe 2 is installed in insulated sleeve 3 to achieve insulation.Because spring 5 is placed around the lower part of probe，probe 2 can keep an upward trend，which can make reliable connection between probe 2 and distributor terminal of measured wire.There is an aperture on the lower end of probe，which is designed to connect probe 2 to measuring circuit.Screw nut 7 is to fix distributor unit to workbench.

Figure 3.Structural drawing of distributor unit

3.3.Specific structure of the clip module

According to the signal demand of system and the structure dimensions of bought pressure clamp，clip module is designed.As shown in Figure 4，it consists of19 parts，and contains photoelectricmechanism and pneumatic mechanism.

Figure 4.Structural drawing of clip module

Four arc grooves of upper part of copper base 9 fits to four arc grooves of bought pressure clamp，which is good for fourwires pressed into clipmodule.Generating INPOS signal is this:when pressing pressure clamp，photoconductive rod 10 moves downward，which makes photodiode packed here generate INPOS signal to single chip microcomputer of controlling circuit.Clamping arm 3，which is installed on the left and right sides of copper base 9，can revolve round cylindrical－pin axis 14.Convex block on the upper port of clamping arm 3 is designed for pressing pressure clamp.A tension spring 15 and two trundles 16 are installed on the lower port of clamping arm 3.Support cap 18 is installed on the upper portof cylinder 1 by threaded connection.Its locking function is this:when the single chip microcomputer receives INPOS signal and controls the electromagnetic valve powering，cylinder 1 moves upward with support cap 18.When moving to a certain position，the conical head of support cap 18 can pushed two trundles16 to open by overcoming spring force of tension spring 15，then the convex block of clamping arm 3 can firmly press down pressure clamp with the help of lever principle，in other words，four measured wires are firmly pressed down.Whenmeasuring is over，the electromagnetic valve is controlled to be in loss of power，and cylinder 1 moves downward with support cap 18，then the upper port of clamping arm 3 is open under the action of spring restoring force，and pressure clamp is loosened.Screw nut 19，which is installed under base 2，has two roles:one is to fix clip module to workbench，the other is to adjust cylinder 1 position of upper or lower thatmakes support cap 18 good contactswith two trundles 16.

4.Conclusion

The special fixture is a very important partof the automatic measurement system of resistant.Its application effect has been fine since 2012.It has very obvious advantages such as compact structure，operation easily，low cost，and so on.It can meet the need of large scale production and measurement by coordinating with automation system.So it is very good for popularization.

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［2］ Liu Xialun.Types and structure characteristics of electronic ignition system［J］.Auto electric parts，2002(6):26－27.

［3］ ZHU Yao－xiang，Pu Lin－xiang.Modern fixture design handbook［M］.Beijing:China Machine Press，2010:8－10.

［4］ WU Zheng－hua.The principle and structure of special fixture［J］.Machining workers，2006(3):49 － 50.

［5］ WANG Xiao－hua.Machine tool fixture book［M］.Beijing:China Machine Press，1992.

实现汽车点火线电阻自动测量的专用夹具的设计*

闫花茹†1，陈 芳1，杜 伟2
1.河南机电高等专科学校 机械工程系，河南新乡 453003;
2.河南科技大学，河南洛阳 471003

汽车点火线的电阻直接影响了发动机的点火性能，是生产厂家出厂检验的一项重要参数指标。为满足大规模生产和自动化测量的需求，根据汽车点火线的接头特征，设计了一种能快速装拆的用于汽车点火线电阻自动测量的专用夹具。它集光、机、气为一体，操作省力方便;经实际应用表明:该夹具明显降低了工人的劳动强度，节约了不必要的劳动力，大大提高了检测效率和自动化水平，具有较大的推广应用价值。

专用夹具;汽车点火线;电阻;自动测量

U270.1+4

10.3969/j.issn.1001－3881.2014.12.019

2014－02－20