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Everyone knows that a car has an engine to power it, but not everyone is familiar with a clutch or how it works. This mechanism both engages and disengages your power transmission from the driving shaft to the driven shaft. It connects rotating shafts, and there can be two or more of these under your hood. If you drive a manual transmission, the clutch is connected to both the shaft coming from the engine and the shafts that turn the wheels. While the motor is going to spin constantly, you dont want the wheels continually spinning. Frictional forces are what clutches rely on to operate. Frictional clutches connect one moving member to another one that is moving at a different speed, or not at all, to get it moving at the same speed so that there is no slippage. Various materials are used to create this friction.
start Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 OBJECTIVES: After studying Chapter 94, the reader should be able to: • • • Prepare for ASE Manual Drive Train and Axles (A3) certification test content area “A” (Clutch Diagnosis and Repair) List the parts that are included in the clutch system Describe how the clutch works Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 OBJECTIVES: After studying Chapter 94, the reader should be able to: • • • Explain the importance of proper clutch pedal freeplay List the steps necessary to replace a clutch Describe the characteristic noise each clutch component part makes when defective Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 KEY TERMS: Bushing candlestick • clutch disc • coil spring clutch • cushioning spring front bearing retainer lever style (pressure plate) marcel spring pilot bearing • pressure plate Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 KEY TERMS: quill • quill shaft release bearing slave cylinder torsional dampers • throwout bearing Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 PURPOSE AND FUNCTION OF A CLUTCH The clutch assembly is located between the engine and the transmission/transaxle The purpose and function of a clutch include the following: To disconnect the engine from the transmission/transaxle to permit the engine to remain running when the vehicle is stopped and to permit the transmission/transaxle to be shifted Connect and transmit engine torque to the transmission/ transaxle To dampen and absorb engine impulses and drivetrain vibration To provide a smooth engagement and disengagement between the engine and the transmission/transaxle Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 NOTE: The term transmission refers to rear-wheel-drive vehicles and the term transaxle usually refers to front-wheel-drive vehicles that have a differential built into the unit A separate differential is used with a transmission Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 COMPONENT PARTS AND OPERATION OF A CLUTCH ASSEMBLY A clutch assembly consists of a clutch disc that is splined to the input shaft of the transmission/transaxle When the driver depresses the clutch pedal, a throwout bearing (release bearing) is forced against the fingers of the pressure plate, which is bolted to and rotates with the flywheel When force is exerted on the center of the pressure plate, the pressure is released from the clutch disc that has been forced against the engine flywheel With the pressure removed from the clutch disc, the engine can be operated without transferring torque to the transmission/ transaxle See Figure 94–1 Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Figure 94–1 Typical automotive clutch assembly showing all related parts (Courtesy of LUK) Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 When the driver reduces force on the clutch pedal, the pedal return spring and the pressure plate spring combine to return the clutch pedal to its at-rest position (clutch-engaged position) When the clutch pedal moves up, the pressure on the throwout bearing is released and the force against the pressure plate spring(s) is released allowing the force of the pressure plate to clamp the clutch tightly between the flywheel and the pressure plate See Figure 94–2 To summarize: When the clutch pedal is up, the clutch is engaged When the clutch pedal is down, the clutch is disengaged Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458