Patent GB-1271444-A (GB)
Title: A vehicle decelerating system
Inventor: BESSIERE PIERRE ETIENNE
IPC: F02B1/04
Filed: 1969-09-12
Abstract: 1,271,444. Fluid-friction brakes. LABAVIA S.G.E. 12 Sept., 1969 [17 Sept., 1968; 13 March, 1969; 20 May 1969], No. 45100/69. Heading F2E. A hydrodynamic retarder is arranged in parallel with part of the cooling circuit of the engine of a vehicle; upstream of that part of the cooling circuit is located a three-way twoposition valve which in one position sends all the liquid it receives to that part of the circuit and in its other position sends it all to the decelerator inlet; constriction means in the decelerator outlet automatically varies the flow cross-section which it presents to the liquid in the same sense as the pressure of the liquid. The rotor is adapted to be connected to the engine shaft so as to run at a speed at least of the same order as the engine speed (i.e. above 3000 r.p.m.) the rotor diameter is less than 20 cms. As shown in Fig. 1 the retarder comprises blades 2 on a rotary semi-toroidal shell 1 cooperating with stator blades 3. Liquid introduced at 11 is impelled along passages 2 1  bounded by the upstream edges of blades 2 and is centrifugally discharged at 12. The shell 1 is rigidly secured to a shaft portion 5 disposed at the end of a vehicle engine shaft, e.g. the crankshaft. Fig. 2 shows the liquid circuits. Cooling water is withdrawn from the vehicle radiator 16, (cooled by the fan 17), by a pump 18 along line 19; the water is forced through the engine 15, along line 20, through a valve 21 and normally along the remainder of line 20 back to the radiator 16; an expansion tank 28 may be provided. The hydrodynamic retarder 14 is connected in parallel across a section 29 lying between valve 21 and the remainder of line 20 by lines 22 and 23 which connect with inlet 11, Fig. 1, and outlet 12 respectively. Valve 21 is a three-way, two-position, valve, of which a practical embodiment is shown in Fig. 4, where connection 20 is from the engine 15, connection 29 is as in Fig. 2, and connection 22 is to the retarder 14, also as in Fig. 2. Opertion of valve 21 is effected by the negative pressure produced in the engine induction pipe 51 downstream of an adjustable throttle member 52 when the member is at least partly closed, provided that the negative pressure has a sufficiently high value, which depends on whether the throttle member is sufficiently closed and whether the vehicle speed is high enough. As shown, the negative pressure is effective through pipe 45 communicating with one side of a diaphragm 41 which is urged to the left against spring 50 so that closure member 37 engages connection 29, while closure member 38 on the same stem 39 is spaced from connection 22. The retarder 14 is now in circuit, as shown in Fig. 2. Initiation of the operation of valve 21 is under the control of the driver by means of an electromagnetically-opened, spring-closed non- return valve 32 governed by a switch 49. The switch may be disposed near the accelerator pedal so as to be closed automatically very near the top of the pedal travel as the pedal is rising; or it may be closed automatically at the beginning of movement of the brake pedal, preferably prior to application of the conventional brake; or it may be opened automatically at the beginning of movement of the clutch pedal. Preferably a second switch is provided in series with switch 49 and located on the instrument panel for manual operation.  In order to make the retarder effective at low speeds, and also to shorten the response time (by speedier filling of the retarder), one or more constrictions 54, Fig. 2, are provided at the output of the retarder. The total crosssection of the constriction(s) increases with increasing liquid pressure or engine speed, and this may be effected by providing a plurality of constrictions, of fixed cross-section, in parallel, the number of constrictions in operation at any one time being controlled by the driver or automatically. Alternatively, a single constriction having a variable cross-section which increases automatically with pressure may be provided. Such a constriction, consisting of a rubber or like diaphragm pierced with an orifice in the shape of a nozzle converging towards its downstream end, is shown at 54 1 , in Fig. 8. Preferably a further such constriction 54 2  is located in parallel with it, and is rendered inoperative by the negative pressure in the engine induction pipe acting at 67 under a diaphragm 65 against a spring 66, this assembly controlling a by-pass valve 64. Preferably the pipe connection from 67 has incorporated in it an electromagnetically operated valve like 32 in Fig. 4. In that case a switch may be provided (Fig. 9, not shown) capable of occupying three alternative positions-(a) off, where valve 32 is closed, so the retarder is not operating; (b) valve 32 is energized and therefore open, so the retarder is operating at less than full torque with both constrictions 51 1  and 54 2  in circuit; (c) valve 32 and the constriction-control valve both energized, so the retarder is operating at maximum torque with valve 64 closed and only constriction 54 1  in circuit.