Method of preheating an internal combustion engine of the diesel, or similar, type
AssigneeRobert Bosch GmbH
InventorLeo Steinke
Life of this patent
Estimating the term…
Abstract
To rapidly heat glow plugs having positive temperature coefficient characteristics, or glow plugs in circuit with a positive temperature coefficient resistor, without overloading connecting relay contacts, a current limiting resistor is placed in circuit with the glow plugs upon first connection thereof to a supply source. After elapse of a first time interval of about 0.1 to 0.3, maximally 1 second, a second switch is controlled to short-circuit the current limiting resistor to permit full voltage to be applied to the glow plugs for rapid heating thereof, during a second time interval, for example between about 2 to 6 seconds, the positive temperature characteristics of the circuit self-limiting current through the resistors to thereby protect circuit switches and relay contacts.
Claims20
In an internal combustion engine requiring preheating for example a Diesel engine, having electrical glow plugs (20, 20'),
- an electrical circuit (10, 18, 19, 19', 20, 20', 36, R) including said glow plugs, said circuit having positive temperature coefficient of resistance characteristics, and including a current limiting resistor (17) and a controlled first switch (15) serially connected with the glow plugs to control current flow and its intensity thereto, and a controlled second switch (21) connected across the current limiting resistor to selectively short-circuit said resistor upon closing of said second switch,
- the method of preheating which comprises, in accordance with the invention,
- controlling said first switch (15) to close and thereby energize the electrical circuit and hence pass limited current through the glow plugs (20, 21') and the current limiting resistor (17) while said second switch (21) is in open condition;
- then, when a first predetermined time period (t.sub.1) of less than 1 second after energization of the glow plugs has elapsed controlling said second switch (21) to short-circuit the current limiting resistor (17);
- and passing current through said electrical circuit directly to the glow plugs for a second predetermined time period (t.sub.2) of at least 2 seconds to rapidly heat the glow plugs.
A Diesel engine glow plug preheating system comprising
- an electrical circuit (10, 18, 19, 19'R, 20, 20', 36) including in series circuit arrangement;
- at least one glow plug (20) having positive temperature coefficient of resistance (PCT) characteristic,
- a current limiting resistor (17), and
- a controlled first control switch (15) serially connected with the at least one glow plug and the current limiting resistor to control current flow to said series circuit arrangement;
- a second control switch (21) connected across the current limiting resistor to selectively short circuit said current limiting resistor upon closing of said second control switch, said second control switch having normally open terminals;
- and a timing control unit (29, 40) connected to and controlling operation of said second control switch (21) to control said second control switch to close the normally open (NO) terminals after elapse of a first time period (t.sub.1) in the order of less than one second and thereby short circuit said current limiting resistor (17),
- said timing control unit (29, 40) being additionally connected and controlling operation of said controlled first control switch (15) to close for energization of the glow plugs and to remain closed at least for a second time period (t.sub.2) of at least two seconds and subsequent to said first time period (t.sub.1) to rapidly heat the glow plugs.
Dependencies are inferred from the claim text.