Patent GB-859976-A (GB)
Title: Improvements in or relating to variable speed transmission mechanisms
IPC: F16H61/02
Filed: 1958-02-27
Abstract: 859,976. Change-speed gears. REGIE NATIONALE DES USINES RENAULT. Feb. 27, 1958 [March 7, 1957; May 22, 1957], No. 6410/58. Class 80 (2). [Also in Group XXXIV] On a motor vehicle, planetary change - speed gear, driven through an automatic clutch or torque converter 5, has elements held against relative rotation by electromagnetic brakes 28, 37 and a direct drive electromagnetic clutch 9, the number of such brakes being one less than the number of forward ratios, only one being engaged for each ratio. Reverse is by a separate dog clutch on the output side 24, Figs. 1-4, or input, Fig. 5 (not shown), reaction in the first case being taken by the same brake as that used for low ratio, such brake being electromagnetic. Unless overridden, each brake acts in one direction only, by initial engagement rocking the brake which closes a switch for full engagement. Function summary.-The gear is automatically controlled by an eletric governor 59, Fig. 4, not described, responsive to vehicle speed and engine torque, with two-stage interlocked manual override cutting out the highest and two highest ratios respectively. Gear arrangement.-Two embodiments are described, one, Fig. 1, driven through a torque-converter 5, and providing one reverse, two reduced forward ratios and a wholly mechanical direct drive by-passing the torque converter; the other, Fig. 5, not shown, driven through a centrifugal clutch and providing three reduced forward ratios, direct drive and one reverse using two electromagnetic brakes and one electromagnetic clutch. The planet train in Fig. 1 comprises a sun 12 driven by an input shaft 3 through the torque converter 5; a sun 14 freely rotatable on an output shaft 11 and clutchable thereto by a dog clutch 24 for forward ratios. The suns 12, 14 mesh a step planet pinion 30 of interengaging planets 13, 16 carried by a common carrier 20 which may be held by the electromagnetic brake 37 for second or clutched to an output shaft 11 by the dog clutch 24 for reverse. The planet pinion 16 meshes a ring gear 17 which is held by the electromagnetic brake 28 for both low and reverse. The input shaft 3 is clutched directly to the output shaft 11 for direct drive by an electromagnetic clutch 9. In Fig. 5 (not shown), the additional forward ratio is provided by a third step on the stepped planet 13, meshing an additional ring gear fast on the output shaft. The dog clutch now serves to connect the clutch-driven input shaft to the second sun for forward ratios, or to the first sun for reverse and at the same time to engage a dog brake for positively holding the planet carrier in reverse. Backward reaction of the planet carrier in low ratio is taken by a one-way detent. Electromagnetic brakes hold the first sun or first ring gear for third and second ratios respectively, whilst an electromagnetic clutch connects the two suns for direct drive. Electromagnetic brakes.-Unless overridden, each brake acts in one direction only, by an auxiliary winding, e.g. 28<SP>2</SP>, which is energized directly by the control to engage the rotating ring-gear armature 27 with the yoke 28, such engagement causing the yoke to rock slightly in the direction of torque reaction 50, Fig. 2, to an extent limited by teeth 32 which thereupon closes the switch 48 causing energization of the main clutch winding 28<SP>1</SP> for full brake engagement. For two-way braking the main winding can be energized directly through a resistor by the override control. Positive means are provided to support the additional torque reaction on the brake 28 in reverse. In this case reaction on the ring gear 17 is in the forward direction 49 and the control directly energizes the main winding 28<SP>1</SP>. The magnet yoke 28 rocks in the direction 49, its teeth 32 being opposed by a spring 43, and this movement causes blade springs 53 carried by the yoke 28 to depress pawls 51 into engagement with ratchet teeth 18 on the ring gear 17 to hold the latter positively. Control.-The dog-clutch 24 is operated by a forward-neutral-reverse lever 56 which, breaks all circuits in neutral, energizes the main winding 281 of the brake 28 in reverse, and feeds a line 57 in forward. The line 57 feeds manual override switches 63, 64 and the torque-speed governor 59 which actuates relays 61, 62 controlling sequentially the brakes 28, 37 and clutch 9. Initially with the lever 56 selecting forward and override switches 63, 64 in their upper positions, springs pull down the relay armatures to make contacts 69, 70. The line 57 thus energizes the low speed auxiliary brake winding 282 through contact 69 and the low speed brake engages as above described. When the governor energizes the relay 61 for 1-2 upshift, the contact 69 is broken and 71 made. Although this disengages the low speed auxiliary brake winding 28<SP>2</SP>, the main winding 28<SP>1</SP> remains engaged by torque reaction. The auxiliary winding 372 of the second speed brake 37 is now energized through contacts 71 and 70 and as the second speed brake 37 self-energizes its main winding 371 at contact 40 (as above described), the torque is released from the first speed brake 28, permitting its contact 48, Fig. 2, to open and disengage its main winding 281, completing the shift. When the governor 59 additionally energizes the relay 62 for 2-3 upshift, the contact 72 feeds the direct-drive clutch winding 9<SP>1</SP>, and breaks the circuit to the auxiliary winding 37<SP>2</SP> of the second speed brake, which self de-energizes its main winding at contacts 40 on the release of torque reaction as in the case of the first speed brake above described. During automatic downshift, the engine has a free period to accelerate to provide the torque reaction necessary to energize the main winding of the brakes. Override.-Depressing the first override switch 64 breaks the direct drive clutch circuit and directly energizes the main winding 371 of the second speed brake 37 through a resistor 68 or providing a 1-2 automatic range with two-way second speed. Depressing the second override switch 63 similarly provides an invariable two-way first speed.