Patent GB-1028499-A (GB)
Title: Power transmission
IPC: F16H61/14
Filed: 1963-09-09
Abstract: 1,028,499. Friction clutches; clutch combinations; change speed control; hydro-dynamic brakes. TWIN DISC CLUTCH CO. Sept. 9, 1963 [March 25, 1963], No. 35511/63. Headings F2C, F2D and F2E. In a change speed gear for vehicles comprising an hydrodynamic torque converter 12 having an engine-driven impeller 14, a turbine 15 connected to the driving shaft of a following constant-mesh change speed gear, and a reactor 18 reacting on a one-way detent 19, a fluidpressure actuated multi-plate friction converterlock-up clutch 33 between the impeller and the turbine is controlled by a lock-up valve 140 which determines clutch 33 disengagement and engagement, for converter drive or lock-up drive to the change speed gear, in response to relatively low and relatively high turbine speeds respectively. In First and Reverse gear, gearestablishing clutch engaging pressure is increased and the transmission to the change speed gear is restricted to converter drive. The lock-up clutch 33 is released during shifts in the higher gears to use the converter as a shock damper. A selectively operable hydrodynamic retarder 37 used to brake the vehicle as an alternative to, or in conjunction with, the usual wheel brakes during converter drive or lock-up drive comprises a radially vaned rotor 38 driven by the turbine 15 and operating in a radially bladed stator chamber 40 which is secured to the stationary housing, supplied with oil, for braking, through an inlet 42, and drained through an outlet 43. The change speed gear (Figs. 5-10, not shown) providing five forward speeds and one reverse may comprise coaxial driving and driven shafts and train-completing fluid-pressure-actuated friction plate clutches 58-62 (first to fifth gears) and 63 (Reverse) arranged singly or in pairs respectively on six or three countershafts and engaged under the control of a conventional selector valve 57 having a neutral position N. The fluid control system includes a pump 45 drawing from a sump 44 and feeding a line 47 through a filter 46 having a one-way by-pass valve 49. The pressure in the line 47 is determined by a pressure regulating valve 48. The line 47 feeds the change-speed gear establishing clutches 58-63 through a line 54, a restriction 55 and a line 56. When First or Reverse gear is engaged, energizing pressure for the clutches 58 or 63 is directed through a ball valve 99 and a line 100 to load a spring 51 of the pressure regulating valve 48 to increase gear establishing clutch pressure in these gears only. Fluid relieved from the valve 48 is fed through a line 102, an oil cooler 103, a retarder valve 106 in its " up " position shown, and a line 121 to the torque converter 12, the outlet of which passes through a line 122 to a further pressure regulating valve 123 determining converter pressure. A valve member 141 sliding on a fixed pin 148 is subjected at its upper (smaller area) and lower (larger area) ends respectively to the pressures at the inlet and. through a line 147, the outlet of the restriction 55 so that, upon every gear shift, during energization of the selected gearestablishing clutch the load on the upper ends of the valve member initially exceeds that at the lower end and shifts the memberto its " down " position after which the restriction 55 loses control and the member returns to its clutch engaged " up " position. The lock-up valve 140 comprises a piston 154 having an " up " position connecting pressure in the line 54 to a line 167 leading to an annular servo-chamber 28 behind a presser plate 29 of the lock-up clutch 33 and a " down " position exhausting the line 167 to the sump for converter drive in which the clutch 33 is released by pressure in the converter. The piston 154 is upwardly loaded against a load-adjustable spring 157 by pressure in a chamber 163 which is connected to a Pitot tube 169 positioned in an oil annulus carried by a radially vaned spinner 170 driven directly or, as shown, indirectly by the turbine 15 and fed through a pipe 181. In First and Reverse gears pressure in the line 100 provides a downward load on the piston 154 additional to the spring load to prevent clutch lock-up upward shift of the valve 140 at all speeds of the turbine. In First or Reverse gear the lock-up clutch is unable to upshift so that drive is through the converter, the pressure of which is at a maximum due to loading of the spring 127 of the valve 123 by pressure in a chamber 187 fed from the line 122 through a line 128, an annular channel 129 and a passage 131 in a manually slidable stem 130. In 1-2 shift the clutch 58 is exhausted in conventional manner and pressure release in the line 100 removes the additional loading of the spring 51, for lower gear-establishing clutch pressure, and the loading additional to the spring 157. The down and up movement of the valve member 141 is ineffective during this shift. At this time Pitot pressure at 169 is insufficient to upshift the valve 140 and drive is through the maximum - pressure converter. On vehicle acceleration, Pitot pressure at 169 increases and at a predetermined turbine speed the valve 140 upshifts to engage the lock-up clutch and exhaust the chamber 187 of the valve 123 to the sump 44 through lines 186, 152 to reduce the loading of the spring 127 and hence the pressure to a minimum in the line 122 and the converter during lock-up drive. A snap-action upshift of the lock-up valve 140 and the turbine speed differential for lock-up clutch engagement and release is achieved by the admission of pressure. as the piston 154 rises, into a passage 164 to act against a fixed pin 162. With the change speed gear in, e.g., second gear and the lock-up clutch engaged, on appropriate reduction of the vehicle and hence turbine speed, the valve 140 downshifts to disengage the lock-up clutch 33 and exhaust it to the sump, and to block the line 186 to allow build up of pressure in the chamber 187 and hence establish maximum pressure in the converter. During, e.g. 2-3 shift with the lock-up clutch 33 initially engaged, the valve piston 141 first moves to its " down " position in which it exhausts the chamber 163 through a line 189 to the sum to downshift the valve 140 to release the lock-up clutch and establish maximum converter pressure so that during shifts above second gear the transmission is in converter drive to damp shocks. When the valve member 141 returns to its " up " position the passage 189 is masked so that as the turbine speed increases pressure build-up in the chamber 163 upshifts the valve 140 to re-engage the lock-up clutch 33. For hydrodynamic braking, the manually slidable stem 130 is moved upwardly to exhaust, if in converter drive, the chamber 187 to the sump through passages 131 and 203, and thereafter to control the pressure in the line 122 by its selected position in the valve 123. A chamber 133 below the retarder valve piston 113 which chamber is normally pressurized from the channel 129 through a line 132 to hold the piston 113 " up " for converter feeding, is also exhausted and converter discharge pressure acts at the upper end of the piston 113 to shift the latter downwards. Fluid is thereby denied the converter feed line 121 and is directed from the cooler through a line 194 to the retarder inlet 42 and thence from the outlet 43 through a line 195, the valve 106, and a line 197 to the converter discharge line 122. The by-passed converter remains filled with oil. The variation of pressure in the line 122 by the stem 131 is effected in the line 197 to control the braking action of the retarder. On return movement of the stem 130, the retarder valve piston 113 resumes its " up " position to re-establish converter connection and exhaust the retarder. When retarder braking is first applied during lock-up drive it may continue long enough to reduce the turbine speed so that converter drive follows when retarder action ceases. During converter drive a pump 199 provides additional flow through the cooler 103. However, when the retarder 37 is operative the pumping effect thereof effects a higher pressure in the lines 195, 197 and 122 than in the line 121, and a check-valve 201 enables this pressure differential to increase flow to the oil cooler above that supplied by the pumps 45, 199. A relief valve 202 opens in the event of cold oil restriction in the converter or retarder. Fluid relieved from the valve 123 passes through a conventional regulating valve 135 to the usual transmission lubricating system.