Patent GB-1003403-A (GB)
Title: Power transmission
IPC: F16H61/06
Filed: 1963-03-04
Abstract: 1,003,403. Change-speed control. TWIN DISC CLUTCH CO. March 4, 1963 [Oct. 5, 1962], No. 8539/63. Heading F2D. A variable speed transmission for use with heavy duty vehicles comprises a hydraulic torque converter 11 followed by a constantmesh gearing providing four forward and four reverse speeds, the gearing being controlled by hydraulically engaged friction plate clutches under the control of a selector valve 60 which controls the supply of pressure to forward and reverse clutches 15, 23 and also controls the supply of liquid to a selector valve 61 which controls the engagement of ratio clutches 38, 40, 53, 55. The valve 60 has a neutral position (shown in Fig. 1) in which both the forward and reverse clutches 15, 23 are disengaged and liquid is not supplied to the valve 61 so that all the ratio clutches are also disengaged. When a direction clutch 15 or 23 is engaged, and the valve 61 is actuated to change gear, the direction clutch is temporarily disengaged, and the rise in pressure of the clutches about to be engaged is controlled such that the ratio clutches are brought into light engagement before pressure is supplied to the direction clutch, and the final engaging pressure for the ratio clutches is higher than that for the direction clutch. Means is also provided for disengaging the clutches when the vehicle brakes are applied. Gearing arrangement.-The constant mesh gearing comprises an input shaft 10 having a gear 13 fast thereon and a gear 19 clutchable thereto by the forward clutch 15. Gear 13 meshes a gear 20 fast on a reverse shaft 21 to which a gear 27 is clutchable by the reverse clutch 23. The gears 19, 27 mesh a gear 28 which is selectively clutchable by the clutches 38, 40 to gears 39, 41 respectively meshing gears 42, 43 gast on a countershaft 44. Gears 54, 56 are clutchable to the countershaft 44 by the clutches 53, 55 and mesh gears 57, 58 on an output shaft 59. Clutch 15 is engaged for forward speeds and clutch 23 for reverse speeds and the first, second, third and fourth ratios are obtained by engaging clutches 38 and 53, 40 and 53, 38 and 55, and 40 and 55. Control system.-Control liquid is supplied by pump 115 through a filter 117 to an inlet port 118 of a flow divider 119 having a piston 121 moved by the hydraulic pressure against spring loading to partially uncover a port 124 leading to a heat exchanger 128, the hydraulic torque converter 11 and a pipe 129 leading to the transmission lubricating system. Liquid also passes through a passage 130 in the piston 121 to a manifold pipe 131 which is connected through lines 132, 92 to the valve 61 and which is also connected to an inlet port 133 of a pressure regulating valve 134. With the valve 60 in its neutral position line 92 is connected through a passage 94 in the valve 60 to a sump 74 so that all the clutches are disengaged. If the valve 60 is now moved to the reverse position (shown in Fig. 3), for example, the passage 94 is cut off from the line 92 and pressure builds up in the line 92 and flows in the position of the valve 61 shown through passages 91, 90 in the valve 61 to lines 82, 95 to engage the clutches 38, 53 for first reverse gear. The reverse clutch 23 however remains disengaged as it is connected to exhaust through a line 75, passages 165, 163 in the valve 60, a line 139, a cylinder 135 and an exhaust port 140 to the sump 74. When the clutches 38, 53 are lightly engaged the pressure in the supply pipes rises and acts through the port 133 on a valve piston 136 and moves it against the bias of a spring 137 to close the sump port 140 and connect the port 133 with the cylinder 135 through passages 141, 142. Oil then begins flowing through the pipe 139 to the cylinder of the reverse clutch and also to opposite ends of a pressure regulating valve 149 through a pipe 143 and a throttling orifice 161 and pipe 162. The pressure of this oil is relatively low until the plates of the reverse clutch 23 are in contact and then begins a controlled rise to maximum value as determined by spring loading on a piston 153 to which is added oil pressure acting against a piston 154 the rate of which additional loading is controlled by the orifice 161. The piston 153 controls connection of the pipe 143 to the transmission lubricating system pipe 129. The valve piston 136 provides a pressure differential so that the engaging pressure of the ratio clutches is higher than that of the direction clutch 23. If, with the valve 61 in the first speed position shown, the valve 60 is shifted from reverse position which is determined by a detent 62 engaging a notch 65, to the forward position determined by the detent engaging a notch 63, the neutral position is passed through in which all heretofore engaged clutches are released. In the forward position of the valve 60, the pipe 139 communicates through passages 166, 164, 165 and a pipe 66 with the cylinder of the forward clutch 15. Control of the pressure for the clutches then proceeds as before. For successive speed shifts, with the valve 60 in forward or reverse position, and considering shift of the valve 61 from first to second speed, the valve 61 is moved to engage a detent 77 with a notch 79 and register the passages 90 with ports 101, 107 leading to lines 95, 104 leading to the clutches 53, 40 and opening the line 82 of clutch 38 to exhaust through a port 87 and a passage 109 in the valve. The cylinder of clutch 53 thus retains connection with the supply pipe 92, but since these passages also now connect with the pipe 104 leading to the empty cylinder of the clutch 40, the pressure drops and with this drop the spring 137 returns the regulating valve piston 136 to its righthand position in which the sump port 140 is uncovered to release the reverse clutch 23. Pressure then begins to build up as previously described. The same considerations apply to the other speed shifts. This procedure enables gear change to be achieved without appreciable shock due to the controlled pressure rise. Provision is made for quickly releasing all the clutches when the vehicle brakes are applied. A conventional master brake cylinder 180 is connected by a pipe 181 to act on a piston 175 which is thus moved when the brakes are applied to open the supply passage to the sump through ports 179, 177 and a channel 178. The pressure at the outlet of the hydraulic torque converter and the inlet 129 of the lubrication system is controlled by a spring-biased valve 170.