Electrical on-off-starting operation control system for engines requiring pre-heat time, such as automotive Diesel engines

Claim 1

Electrical ON-OFF-START operation control system for engines requiring a pre-heat time before starting, such as automotive-type Diesel engines having a source of electrical power (11, 12); a starter motor (M-19); and a starter switch means (18, 52, 53, 54) therefor selectively connecting the motor (19) to the source; a manually operable control switch (15, 20) having the positions, in sequence; OFF (O); ON (I); START (II); and corresponding ON (21) and START (22) terminals and a movable switch member (14) connected to said source; a glow plug energization circuit (X-17-38-G) including at least one glow plug (17) and a heating element (32) -- temperature sensitive switch (36) in heat transfer relation to the heating element (32); wherein, in accordance with the invention, the START position of the control switch (15) is unstable and includes means (A) biassing the switch to return to the ON position upon release of manual operation after having moved the switch through the ON position to the START position, said switch being connected to form in the single ON position simultaneously a pre-heat connection for the glow plug or glow plugs; and wherein the system further comprises a first relay (29) having its relay terminals and switch element (31) selectively connecting the glow plugs (17) directly to the source (11); a second relay (25) having transfer terminals (24-26; 24-61), one set (24-61) of which is connected in a self-holding circuit; the coil (28) of the first relay (29) being connected (30-28-27-23) through the other set of transfer contacts (26-24) of the second relay (25); a start control circuit (46-48-51) connecting said START terminal (22) of the switch (15) to the starter switch means (18, 52, 53, 54); an energizing junction (57) connected to the coil (59) of the second relay (25) which, when energized, provides energization to the coil; a diode (56) connecting (46-55) said START terminal (22) of the control switch (15) to the energizing junction (57); and a further diode (50) connecting (46-49-47) said START terminal (22) of the control switch (15) to the coil (28) of the first relay (29). whereby said further diode (50) and the connection thereof to the START terminal will be in parallel with the connection of the coil (28) of the first relay (29) through the other set (24-26) of the transfer contacts of the second relay (25), said diodes (56, 50) being poled in conductive direction with respect to said source; said energizing junction (57) being further connected (60) to said one set of transfer contacts (24, 61) of said second relay (25) to form said self-holding circuit, and being additionally connected (X', 62) to said temperature sensitive switch (33, 36) to be energized thereby when the temperature to which said switch is exposed is above a predetermined level to provide energization current to the junction (57) and hence to the second relay (25) when the temperature as sensed by said temperature sensitive switch (36) is indicated to be adequate to permit starting and operation of the engine.