OBJECTIVES

2. OBJECTIVES After studying Chapter 9, the reader should be able to: • Identify the components of a torque converter. • Explain the purpose for each torque converter component. • Describe the fluid flow inside a torque converter. • Explain the operation of a torque converter clutch.

3. INTRODUCTION • The torque converter, commonly called a converter, is a type of fluid coupling that transmits power from the engine’s crankshaft to the transmission input (turbine) shaft. It has two important purposes as it transfers the engine torque to the transmission: • It serves as an automatic clutch so the vehicle can be stopped with the engine running and the transmission in gear. • It multiplies torque while the vehicle is accelerating to improve acceleration and pulling power.

4. FIGURE 9-1 The torque converter is mounted on the engine’s crankshaft and transfers power to the transmission. (Courtesy of Toyota Motor Sales USA, Inc.) INTRODUCTION

5. FIGURE 9-2 A fluid coupling transfers power through fluid, from one set of vanes to the other. INTRODUCTION

6. FIGURE 9-3 The major parts of a four-element torque converter are the clutch disc, turbine, stator, and impeller shown in this cutaway view. The turbine is splined to the transmission input shaft, and the stator is splined to the stationary reaction shaft at the front of the transmission. (Courtesy of Chrysler Corporation) CONSTRUCTION • Most torque converters have four major elements: an impeller, turbine, stator, and converter clutch.

7. FIGURE 9-4 A three-element torque converter has a turbine, stator, and pump or impeller. (Courtesy of Chrysler Corporation) CONSTRUCTION

8. FIGURE 9-5 This cutaway view of a four-element torque converter shows the relationship of the internal parts. CONSTRUCTION

9. FIGURE 9-6 The flexplate connects the converter to the crankshaft. The pilot of the converter fits the end of the crankshaft to center the converter to the crankshaft. (Courtesy of Chrysler Corporation) CONSTRUCTION

10. FIGURE 9-7 Most torque converters have a round cross section (left). Some new transmissions use a shorter, elliptical, squashed converter (right). FIGURE 9-8 The stator one-way clutch allows the stator to rotate freely during the coupling phase, but stops counterclockwise rotation during torque multiplication. (Courtesy of Toyota Motor Sales USA, Inc.) CONSTRUCTION

11. FIGURE 9-9 These air-cooled torque converters have shrouds that pump cooling air past the impeller. WHAT IS AN AIR-COOLED TORQUE CONVERTER? • Some early torque converters used with smaller engines are air cooled. • They have a shroud with fins attached to the rear of the converter cover to force cooling air flow past the converter.

12. FIGURE 9-10 When the engine is running, fluid in the impeller is thrown outward and into the vanes of the turbine. (Courtesy of Chrysler Corporation) OPERATION • A torque converter is a hydrodynamic unit. • It transfers power through the dynamic motion of the fluid. • Most other hydraulic units transfer power through the static pressure of the fluid.

13. FIGURE 9-11 The two major operating conditions of a converter are stall and coupling. These conditions shift back and forth depending on throttle opening and vehicle load. OPERATION

14. FIGURE 9-12 The fluid flowing around the guide ring is called vortex flow (a). The fluid flow around the converter is called rotary flow (b). (Courtesy of Chrysler Corporation) OPERATION

15. FIGURE 9-13 If a ball is thrown against a wall, kinetic energy in the ball will cause it to bounce back (a). The energy remaining in the fluid striking the turbine vanes will cause the fluid to bounce back in a similar manner (b). OPERATION

16. OPERATION • Torque Multiplication • Coupling Phase

17. FIGURE 9-14 The fluid flow from the turbine is turned to the same direction as the impeller by the stator vanes. OPERATION

18. FIGURE 9-15 The vortex flow, torque multiplication, and efficiency of a torque converter change as the turbine speed increases relative to the impeller. OPERATION

19. FIGURE 9-16 The clutch disc of a TCC has lining on the outer edge where it can contact the inner side of the cover. While released, there is a fluid flow between the disc and the cover. Note that the clutch disc is splined to the turbine. (Courtesy of Chrysler Corporation) TORQUE CONVERTER CLUTCHES • The converter clutch is a large clutch disc called a • pressure plate or clutch disc. • It has friction material and a damper assembly attached to it and it is splined to the turbine

20. FIGURE 9-17 TCC release fluid flows through the center of the turbine shaft to the front of the clutch disc (left). Pressure to apply the clutch enters between the converter hub and the stator support (right). TORQUE CONVERTER CLUTCHES

21. FIGURE 9-18 The turbine has a series of damper strings that connect to the clutch disc (a). Many clutch discs have a damper assembly at the center (b). (a is courtesy of Chrysler Corporation; B is courtesy of Tribco, Inc.) TORQUE CONVERTER CLUTCHES

22. FIGURE 9-19 A four-cylinder engine has two power impulses every revolution, and these impulses cause the crankshaft to speed up momentarily. During this time, the damper springs will compress to absorb the speed fluctuation. TORQUE CONVERTER CLUTCHES

23. TORQUE CONVERTER CLUTCHES • Controlled TCC Capacity

24. CVT TORQUE CONVERTER • Most CVT transmissions use a low-profile elliptical torque converter with a lock-up clutch. • Since CVTs are infinitely variable, the torque converter is not needed once the vehicle is moving. • Therefore the converter is used to multiply the torque to get the vehicle moving from a stop, and then becomes a mechanical connection between the engine and the CVT. • The torque converter clutch apply will occur at about 12 mph (20 kph) and stay locked until the vehicle comes to a stop.

25. STALL SPEED • Stall is when the turbine is held stationary while the converter housing and impeller are spinning. • This is done by shifting the transmission into gear and applying the brakes to hold the drive wheels stationary. • The importance of stall speed is that an engine must be able reach an rpm where enough torque is available to accelerate the vehicle, but not running so fast that there is poor fuel economy and excessive noise

26. FIGURE 9-20 A technician measures stall speed while testing a transmission. This test is performed using extreme caution because of the potentially dangerous conditions. The test period is limited to 5 seconds because of potential transmission damage. STALL SPEED

27. STALL SPEED • Stall Factors • The actual stall speed of a torque converter is determined by several factors: • The amount of engine torque, • The diameter of the converter, • The angle of the impeller vanes, • The angle of the stator vanes.

28. FIGURE 9-21 The stall speed of a torque converter must match the engine for good vehicle driveability. STALL SPEED

29. FIGURE 9-22 Converter diameter helps determine stall speed. Along with other factors, it is used to help select the correct replacement converter. STALL SPEED

30. FIGURE 9-23 On some converters, it is possible to see the impeller fin angle from the outside. The converter on the right has rearward or negative fin angles that will produce a higher stall speed than the one on the left, which has forward or positive fin angle. STALL SPEED

31. SUMMARY • A torque converter hydraulically connects the engine to an automatic transmission and will multiply the engine torque under certain conditions. • Torque converters utilize an impeller, turbine, stator, and lock-up clutch. • Stall and coupling are the extremes of torque converter operation. Stall occurs when the impeller and turbine are operating at different speeds, and coupling occurs when the impellers are turning at nearly the same speed.

32. SUMMARY • Torque converter clutches are used to mechanically connect the engine to the transmission. During lock-up, torque converter slippage will be eliminated and fuel mileage will improve. • The factors that affect torque converter stall are converter diameter, angle of the vanes, and the torque of the engine.

33. REVIEW QUESTIONS • The two purposes for a torque converter are to serve as an automatic _________ and to multiply the engine’s _________. • List the four elements of a typical torque converter. • The torque converter is bolted to the _________. • The torque converter’s input member is the _________ and the output member is the _________. • The stator is the _________ member of the torque converter and is splined onto the reaction shaft through a _________ clutch. • The flow of fluid from the impeller to the turbine is called a _________ flow. The circular flow of fluid leaving the impeller is called _________ flow.

34. REVIEW QUESTIONS • A torque converter clutch uses _________ springs to smooth out _________ vibrations. • Some torque converter clutches use a _________-filled clutch to smooth out torque converter clutch application. • Torque converter stall is when the _________ is held stationary and the _________ is spinning. • Stall speed is the _________ rpm that an engine can turn while the turbine is _________. • Stall testing can be used to check _________ and _________ condition. • Vehicles with small engines typically use a torque converter that has a _________ stall speed, and vehicles with a powerful engine use a torque converter with a _________ stall speed.

35. REVIEW QUESTIONS 19. Four factors that affect torque converter stall speed are: • Engine _________ • _________ diameter • Impeller _________ angle • Stator fin _________

36. CHAPTER QUIZ • Student A says that a torque converter is a hydraulic connection between the engine and transmission. Student B says that a torque converter clutch will increase the torque to the transmission. Who is correct? • Student A • Student B • Both A and B • Neither A nor B

37. CHAPTER QUIZ • Student A says that a torque converter is a hydraulic connection between the engine and transmission. Student B says that a torque converter clutch will increase the torque to the transmission. Who is correct? • Student A • Student B • Both A and B • Neither A nor B

38. CHAPTER QUIZ 2. The input member of the converter is the • turbine. • stator. • impeller. • All of these

39. CHAPTER QUIZ 2. The input member of the converter is the • turbine. • stator. • impeller. • All of these

40. CHAPTER QUIZ 3. Student A says that the flexplate connects the torque converter to the crankshaft. Student B says that the torque converter is considered part of the transmission. Who is correct? • Student A • Student B • Both A and B • Neither A nor B

41. CHAPTER QUIZ 3. Student A says that the flexplate connects the torque converter to the crankshaft. Student B says that the torque converter is considered part of the transmission. Who is correct? • Student A • Student B • Both A and B • Neither A nor B

42. CHAPTER QUIZ 4. Student A says that fluid motion inside a converter is controlled by the guide ring. Student B says that fluid motion inside a converter is controlled by the stator vanes. Who is correct? • Student A • Student B • Both A and B • Neither A nor B

43. CHAPTER QUIZ 4. Student A says that fluid motion inside a converter is controlled by the guide ring. Student B says that fluid motion inside a converter is controlled by the stator vanes. Who is correct? • Student A • Student B • Both A and B • Neither A nor B

44. CHAPTER QUIZ 5. The fluid flow from the impeller through the turbine and stator is called • rotary flow. • impeller flow. • vortex flow. • turbine flow.

45. CHAPTER QUIZ 5. The fluid flow from the impeller through the turbine and stator is called • rotary flow. • impeller flow. • vortex flow. • turbine flow.

46. CHAPTER QUIZ 6. The fluid flow around the circumference of the converter is called • rotary flow. • impeller flow. • vortex flow. • turbine flow.

47. CHAPTER QUIZ 6. The fluid flow around the circumference of the converter is called • rotary flow. • impeller flow. • vortex flow. • turbine flow.

48. CHAPTER QUIZ 7. A strong vortex flow will • cause the stator clutch to lock. • release the stator clutch. • circulate through the guide ring. • All of these

49. CHAPTER QUIZ 7. A strong vortex flow will • cause the stator clutch to lock. • release the stator clutch. • circulate through the guide ring. • All of these

50. CHAPTER QUIZ 8. During the coupling phase the • vortex flow nearly stops. • stator clutch locks. • rotary flow nearly stops. • flow stops.