Patent GB-1490346-A (GB)
Title: Hydrokinetic fluid torque transmission
IPC: F16H61/14
Filed: 1974-04-02
Abstract: 1490346 Hydrodynamic torque converter lock-up clutch control; friction clutches; torque converters BROCKHOUSE TRANSMISSIONS Ltd 31 Jan 1975 [2 Feb 1974] 04932/74 Headings F2D F2C and F2W A hydrodynamic torque converter lock-up clutch is engaged in dependance on the ratio between the speeds of the turbine 13 and the impeller 11, there being over-riding means, in the form of a kick-down switch operated by a vehicle accelerator pedal or a switch operated by operation of the main vehicle clutch, to disengage the lock-up clutch. The clutch is engaged when the ratio rises above a first value and remains engaged (or will re-engage if previously disengaged by an over-ride) until the ratio drops below a second, lower value (greater slip). The clutch is also disengaged if the turbine speed (or alternatively the impeller speed) is below a predetermined value, to prevent stalling of the engine at idle and engaged if the turbine or impeller rotates above a further predetermined speed. Pressure fluid supply.-As shown in Fig. 4, a pump 51 supplies fluid through a filter 54 to the torque converter 10 and to one side, B, of the lock-up clutch to hold the clutch disengaged against a spring 23 (Fig. 2), the clutch being engaged when a solenoid-controlled valve 37 is actuated to supply pressure liquid to the side A of the clutch (through passages 34, 33, 32 and 31). The pressure fluid supply is protected by a relief valve 64 and also contains a pilot-operated pressure regulating valve 59 and a cooler 61. The electrical circuit which operates the solenoid controlled valve 37 comprises transducers 100, 101 which produce signals repre senting the turbine and impeller rates of rotation, respectively (Fig. 5). These signals are fed through signal conditioners 102 and 104 and then to a ratio detector 106 which feeds a signal to one input of a logic gate S3 if the ratio of turbine speed to impeller speed is greater than a predetermined value (0À72 as shown), and feeds a signal to the other input of gate S3 if the ratio is less than another, higher value (0À84 as shown). Gate S3 consists of a pair of NAND gates, each with its output connected to one input of the other so that this gate will generate a signal to engage the clutch if the ratio rises above 0À84 and hold it engaged until the ratio falls below 0À72 (Fig. 6, not shown). The circuitry also includes an electronic counter 108 and a comparator 110, the counter giving a signal, summed pulses from conditioner 102 over a time set by pulses from an oscillator 105, and supplies signals to the inputs of logic gates S1 and S5, these being of the same construction as gate S3. Logic gate S1 overrules gate S3 if the turbine speed is below a set value (850 r.p.m. as shown) to maintain the clutch disengaged and similarly logic gate S5 engages the clutch when turbine speed is high (over 1900 r.p.m. as shown), irrespective of the ratio of turbine and impeller speeds. Switches S2 and S4 are operated by the vehicle clutch and accelerator pedal to provide the above-described over-ride. The control logic 112 contains further gates which combine the signals of gates S1 to S5, (Fig. 6, not shown) to provide an output to the coil of valve 37. Clutch construction.-The clutch comprises a driving plate 26 provided with friction linings 27 and slidably mounted on a portion of the impeller 11, the clutch plate 26 being clamped between a plate 21 fixed to the turbine 13 and a piston 22 during engagement. The piston 22 is urged away from plate 26 to disengage the clutch by pressure at side B acting against the bias of a Belleville spring 23, and the clutch is engaged when pressure is supplied to side A via a rotating seal 35, a radially extending passage 34 in the converter output shaft 16, an axial passage 33 and further passages 32 and 31. In addition to the above controls of the lockup clutch, the clutch may be engaged if too much heat is generated in the cooling system due to excessive slip, a manually operated switch may allow the clutch to be disengaged at will or the clutch may be permanently engaged in certain of the ratios in a gear-box in series with the torque converter. As an alternative to clutch engagement due to excessive heat generation, a warning light or an audible warning may be operated. Fluid logic may replace the electrical circuitry.