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Figure 31. Starter: 1. Anchor shaft; 2. Drive gear; 3. Gear bushing; 4. Freewheel clutch roller; 5. Clutch casing; 6. Pinion drive lever axis; 7. Starter cover on the drive side; 8. Gear drive lever; 9. Traction relay anchor; 10. Traction relay housing; 11. Pull-in winding of the traction relay, 12. Holding winding of the traction relay; 13. Traction relay rod; 14. Traction relay core; 15. Contact plate; 16. Traction relay cover; 17. Contact bolts; 18. End collector; 19. Brush; 20. Brush spring; 21. Starter cover bushing; 22. Casing; 23. Tie bolt; 24. Starter cover from the collector side; 25. Anchor winding; 26. Armature core; 27. Stator winding; 28. Stator pole; 29. Starter housing; 30. Limiting disc; 31. Leash ring; 32. Centering disc; 33. Buffer spring; 34. Outer ring of the freewheel clutch; 35. Freewheel clutch hub; 36. Gear travel limiting ring; 37. Guide rod; 38. Plunger; 39. Starter; 40. Auxiliary starter relay; 41. Mounting block; 42. Ignition switch; 43. Generator; 44. Battery; I. Scheme of operation of the overrunning clutch.
To spin the engine crankshaft to the speed at which it will start to operate (i.e. to start the engine), a starter of type 29.3708 is used. It turns the crankshaft with a gear for the toothed ring of the flywheel. The starter power is 1.3 kW with a current consumption of 260 A.
The starter is a four-pole DC motor with compound excitation, with remote electromagnetic activation and a roller freewheel clutch. It consists of the following main parts; housing 29, anchor with freewheel clutch and drive gear 2, two covers 7 and 24 and traction relay 10. The housing and covers are connected together by two tie bolts.
Inside the steel housing 29, four steel poles 28 with the excitation winding coils are secured with screws. The housing together with the poles and winding is the starter stator. Three winding coils (series) are connected to the armature winding in series, and one (shunt) is connected in parallel. Therefore, the excitation of the starter is called mixed. It allows obtaining a high torque in the braked state and a relatively low rotation frequency of the armature at idle, which reduces wear of the bearing bushings and facilitates the operating conditions of the freewheel clutch.
An anchor assembled on shaft 1 rotates between the stator poles. Anchor core 26 is assembled from electrical steel plates pressed onto the middle part of the shaft. Along the circumference of the core there are longitudinal grooves insulated with cardboard, in which the anchor winding 25 is located, made of copper tape. The ends of the winding are soldered to the collector plates and are calked for greater reliability. The anchor shaft rotates in two metal-ceramic bushings. The rear bushing 21 is pressed into cover 24, and the front one is located in the clutch housing and the front end of the anchor shaft enters it when the starter is installed in the clutch housing socket.
The special feature of the 29.3708 starter is the end collector 18, pressed onto the rear part of the anchor shaft. Its use allowed to reduce the length and "weight" of the starter. In addition, the end collector contributes to more stable and long-term operation of the brush contact. The collector is made in the form of a plastic disk with copper plates poured into it.
At the front end of the anchor shaft there is a freewheel clutch with gear 2 of the drive. When the engine is started, the clutch transmits torque from the anchor shaft to the gear, and after starting it disconnects the gear and the anchor shaft, and therefore the rotation of the flywheel is not transmitted to the shaft. As a result, the anchor is protected from "runaway" - damage by centrifugal forces due to excessive rotation speed.
The coupling consists of an outer ring 34 riveted to the hub 35 and an inner ring integral with the gear 2. In the grooves of the outer ring there are rollers 4 with springs, plungers 38 and guide rods 37. All of them together with the outer ring and two thrust half rings are rolled into a steel casing 5. The grooves of the outer ring have a variable width. In the wide part of the groove the rollers can rotate freely, and in the narrow part they are wedged between the outer and inner rings of the coupling.
The traction relay is attached to the cover 7. It is used to remotely control the starter. The relay closes the power supply circuit of the armature and stator windings, and also engages the gear 2 with the flywheel ring through the lever 8. The relay has two windings, has a pull-in 11 and a holding 12 winding, wound in one direction. The beginnings of the windings are soldered to the plug "50" on the relay cover. The end of the holding winding is welded to the relay flange (i.e. connected to the "ground"), and the end of the pull-in winding is connected to the lower contact bolt of the relay.
Starter operation
The starter is activated by an auxiliary relay type 111.3747-10, installed in the engine compartment. When the key is turned to position II ("Starter"), contacts "30" and "50" of the ignition switch are closed, and voltage is supplied to the winding of auxiliary relay 40. It is triggered, and current flows through its closed contacts to the windings of the starter traction relay. Under the action of this current, a magnetic force is generated (about 10-12 kgf), pulling in anchor 9 until it contacts core 14. The anchor is pulled in and pushes rod 13 with contact plate 15, which closes contact bolts 17. The dimensions of the rod are selected so that the closing of the contact bolts occurs even before the anchor contacts the core, and with further movement of the anchor the spring of the contact plate is compressed, pressing it more strongly against the contact bolts. At the same time, the anchor of the relay with lever 8 moves forward the freewheel clutch with gear 2 and brings it into engagement with the flywheel ring.
When the contact bolts are closed, the pull-in winding of the relay is de-energized, since both of its ends are connected to the "plus" of the storage battery 44. But since the relay anchor is already pulled in, then to hold it in this position, a relatively small magnetic flux is required, which is provided by one holding winding 12.
Current flows through the closed contacts of the traction relay, feeding the stator and anchor windings. The starter anchor begins to rotate, and its rotation is transmitted through the screw splines to the hub 35 and the outer ring 34 of the clutch connected to it. Since the rollers 4 are displaced by springs into the narrow part of the groove of the outer ring, they are wedged between the outer and inner rings of the clutch. Therefore, the torque from the anchor shaft is transmitted through the clutch and gear to the flywheel ring.
After the engine starts, the flywheel begins to rotate the starter pinion, and the pinion speed begins to exceed the starter anchor speed. Inner clutch ring (combined with gear) draws the rollers into the wide part of the groove of the outer ring 34, compressing the plunger springs 38. In this part of the groove, the rollers rotate freely without jamming, and the torque from the engine flywheel is not transmitted to the starter armature shaft.
When the starter is switched off, the auxiliary relay contacts open, and the starter winding supply current goes along the following path: "plus" of the storage battery - closed contacts of the traction relay - pull-in 11, and then holding 12 windings of the traction relay - "ground". Since the direction of the current in the turns of the windings is opposite, the magnetic fluxes created by the windings compensate each other, and the relay core is demagnetized. The relay anchor is pressed back to its original position by springs, and the relay contacts open, disconnecting the supply to the anchor and stator windings of the starter.
At the same time, the anchor of the traction relay with the lever 8 moves the freewheel clutch back and disengages the pinion from the flywheel ring. The anchor of the starter is slowed down by the friction forces of the brushes on the collector, and it quickly stops.