Patent GB-585716-A (GB)
Title: Improvements in variable-speed transmissions, more particularly for motor vehicles
IPC: B60K17/08
Filed: 1939-08-11
Abstract: 585,716. Variable-speed gearing. KEGRESSE, A. Aug. 11, 1939, No. 23230. [Class 80 (ii)] In an automatic transmission applicable to motor-vehicles, comprising a change-speed gear with constant-mesh gear wheels controlled by dog clutches and a friction clutch device, hydraulic members controlling the clutches are so arranged that for each speed-change upwards or downwards, the appropriate dog clutches are brought into engagement before the corresponding friction clutch. Two friction clutches 14, 15 are employed, the clutch 15 being placed in engagement by the fluid pressure and the clutch 14 by the action of springs 13 exerted in the contrary sense to the action of the fluid and acting independently of the pressure of the fluid. In the four-speed gear shown in Fig. 1, comprising gears 90, 91 ; 93, 89 ; 87, 85 ; and 88, 86 ; the gear 90 is moved axially by hand control on splines on the tubular shaft 83 on which the clutch disc 15 is splined, and the gear 89 is integral with the shaft 83. The gear 85 is mounted freely on the shaft 82 passing through the tubular shaft 83 and carrying the clutch disc 14 on splines, while the gear 86 is integral with the driven shaft 3. The gears 91, 93 are mounted freely on the secondary shaft and the gears 87, 88 are integral with the secondary shaft. A dog clutch sleeve 72 splined on the shaft 82 can be placed in engagement with either of the gears 85, 86 by means of a fork 71 on the rod 70 of a piston 66. and a dog clutch block 69 splined on the secondary shaft can be placed in engagement with either of the gears 91, 93 by means of a fork 68 on the rod 67 of a piston 65, Fig. 8. External teeth 95 on the block 69 mesh with a pinion adapted to mesh with the sliding pinion 90 for reverse drive. Cooperating with the clutch discs 14, 15 are a flywheel 4 mounted on the engine shaft 2, a distributor plate 6 fixed to the flywheel by bolts 7, and an axially movable plate 5 having peripheral teeth 8, Fig. 3, engaging in recesses in the rim of the plate 6. An annular piston 9 sliding in the rear face of the plate 6 is held in its neutral position by a piston ring 114, and is connected to the plate 5 by bolts 12. Compression spring 13 being interposed. An annular channel.16 in the hub of the plate 5 leads through a radial conduit 17 to a piston valve 18 counterbalanced with respect to centrifugal face, as described in Specification 466,543, and controlling parts for the actuation of the annular piston and the evacuation of the oil. Opposite the valve 18 is a spring-controlled piston 22 controlling ports leading to the annular piston and to the atmosphere. A body 26 fixed to the casing 1 contains the hydraulic pump 27, Fig. 6, driven from the hub of the plate 6 and delivering oil through a conduit 32, Fig. 6, to a selector 33, Fig. 8, comprising a sliding sleeve 34 actuated manually and a hollow cylinder 35 actuated from a centrifugal governor 97 through a rod 141. The sliding sleeve of the governor and the rod 141 are each provided with means for retaining them in each of the 'gear' positions and the 'stop' position. The sleeve 34 also has external grooves engaged by a spring bolt to retain it in a 'stop' position or in any 'gear' position, in which apertures 40 connect a port 47 in the cylinder 35 in turn with each of the passages 48 corresponding with the four 'gear' positions or with a passage 53 corresponding to the 'stop' position. The passages 48 lead to chambers 49-52 communicating with ends of the cylinders 63, 64 of the pistons 65, 66 which actuate the dog clutches for changing gear. A central port 73 in each cylinder admits oil beneath a piston 74 actuating a needle valve 75 controlling a port 76 leading to the centre of the other cylinder and an escape port 78. The passage 53 admits oil between valves 54, 55, Fig. 11, the valve 54 has the weaker spring and leads to the chamber 56 of hollow distributor ring having holes leading through a channel 16 to the conduit 17 of the distributor plate 6, while the valve 55 leads to an escape port 115. In operation, with the car stopped and the cylinder 35 and sleeve 34 in the 'stop' position, Fig. 8, oil expelled past the valve 54 &c. to the conduit 17 opens the valve 18 and penetrates behind the annular piston 9 and can escape through the outlet 25. If the driver accelerates, the plug 22 closes the outlet 25, the piston 9 is at first retained by the ring 114, and the pressure is built up to an amount determined by the relief valve 55. The axial movement of the piston 9 then releases the clutches 14, 15. If the sleeve 34 is now moved to the extreme left in Fig. 8, oil escaping through one of the apertures 40 and the corresponding passage 48 actuates the piston' 65 to engage the clutch sleeve 69 with the gear 92 for first speed; the piston 65 uncovers the conduit 117 and oil escapes through this to the distributor 57 and valve 18 to the piston 9, which moves the plate 5 into engagement with the clutch disc 15 to transmit the drive. When the desired speed is reached, the governor 97 displaces the rod 141 to its first position, bringing the aperture 47 of the cylinder 35 opposite the second passage 48 ; oil is thus admitted to the chamber 50 and the cylinder 64, so that the piston 66 will engage the clutch sleeve 72 with the gear 85 and the disc 14 will be rotated idly at less than engine speed. When the piston 66 reaches the end of its stroke, the oil pressure displaces the piston 74 and its needle valve 75 to relieve the pressure, and the springs 13 will actuate the piston 9 and plate 5 to engage the clutch disc 14 and release the disc 15, so that the second speed is in engagement. The third and fourth speeds are similarly brought into engagement by further increase of speed, provided that the sleeve 34 has been manually moved to its full-speed position. For a three-speed gear, a single dog-clutch cylinder controls the first and third speeds, Fig. 20, these speeds being associated with one of the friction clutches while second speed is controlled by the other ; for a five-speed gear, three dog-clutch sleeves are provided two for double dog clutching and one with single dog clutching; and so on, the even speeds always being controlled by one of the friction clutches and the odd speeds by the other.