Title:
IGNITION ARRANGEMENT FOR INTERNAL COMBUSTION ENGINES
United States Patent 3640260
Abstract:
The ignition arrangement, which, as an integrated circuit, is fixed to the distributor housing, comprises a battery-powered circuit having two transistors Darlington connected, of which the common load is the primary winding of a spark coil or of an ignition capacitor charging transformer. A cam on the distributor shaft periodically opens a make-and-break switch in the circuit.


Inventors:
Mittag, Hermann (Stuttgart, DT)
Issler, Jorg (Stuttgart, DT)
Application Number:
05/051181
Publication Date:
02/08/1972
Filing Date:
06/30/1970
Assignee:
Robert Bosch GmbH (Stuttgart, DT)
Primary Class:
Other Classes:
315/209R, 315/209T
International Classes:
F02P7/00; F02P3/04; F02P3/045; F02P3/08; F02P7/02; G01P3/481; (IPC1-7): F02P3/06
Field of Search:
123/146.5A,148E 315
View Patent Images:
US Patent References:
3438362IGNITION SYSTEM1969-04-15Clyborne et al.
3374778Electronic ignition system1968-03-26Dixon
3340861Transistorized ignition circuit1967-09-12Schiff
3262438Ignition system for internal combustion engines1966-07-26Holford
Primary Examiner:
Goodridge, Laurence M.
Claims:
1. In an ignition arrangement for internal combustion engines, means for charging a capacitor comprising a circuit having a source of direct current; said circuit including at least two transistors connected together to have a current gain that is the product of their individual current gains, the base of one of said transistors being connected to the emitter of the other of said two transistors and the collectors of said two transistors being connected directly together, so that said two transistors are Darlington connected; means for generating high voltage pulses for firing spark plugs, said means including an inductive reactance connected in the emitter-collector path of said one of said transistors as the load common to said two or more said transistors; and means for periodically opening said circuit and thereby charging said capacitor in synchronism with the operation of the engine.

2. A combination as defined in claim 1, wherein said means for periodically opening said circuit disconnects the base of the other of said transistors in said circuit.

3. A combination as defined in claim 2, including an ignition distributor, and an electronic unit as a part of said distributor and having an integrated circuit comprising said transistors.

4. A combination as defined in claim 3, wherein said distributor comprises a housing to which said unit is fixed, and said unit includes connector means accessible from outside said housing for connection to said inductive reactance.

5. In an ignition arrangement for internal combustion engines, a combination comprising a circuit having a source of direct current; said circuit including at least two transistors connected together to have a current gain that is the product of their individual current gains; means for generating high voltage pulses for firing spark plugs, said means including an inductive reactance connected in the emitter-collector path of said one of said transistors as the load common to said two or more said transistors; means for periodically opening said circuit in synchronism with the operation of the engine, said means for periodically opening said circuit disconnecting the base of the other of said transistors in said circuit, said transistors being Darlington connected; an ignition distributor and an electronic unit as a part of said distributor and having an integrated circuit comprising said transistors, said distributor comprising a housing to which said unit is fixed, and said unit including connector means accessible from outside said housing for connection to said inductive reactants, said unit being located inside said distributor housing, and said connector means being a screw means having a head containing said unit and engaging an inside surface of said housing, and further having a threaded shank that projects through and outside of said housing for permitting connection to said inductive reactants, and at least one nut screwed on to the exposed portion of said shank.

6. In an ignition arrangement for internal combustion engines, a combination comprising a circuit having a source of direct current; said circuit including at least two transistors connected together to have a current gain that is the product of their individual current gains; means for generating high voltage pulses for firing spark plugs, said means including an inductive reactance connected in the emitter-collector path of said one of said transistors as the load common to said two or more said transistors; means for periodically opening said circuit in synchronism with the operation of the engine, said transistors being Darlington connected, said means for periodically opening said circuit disconnecting the base of the other of said transistors in said circuit; an ignition distributor and an electronic unit as part of said distributor and having an integrated circuit comprising said transistors, said distributor comprising a housing to which said unit is fixed, and said unit including connector means accessible from outside said housing for connection to said inductive reactants, said connector means being a heat dissipating body in which said electronic unit is held.

7. A combination as defined in claim 6, wherein said connector means is fixed to the outside of said distributor housing, and includes first terminal means projecting through and inside said housing for connection to said means for periodically opening said circuit and second terminal means outside of said housing for connection to said inductive reactance.

8. A combination as defined in claim 7, wherein said first and second terminal means are plugs.

9. A combination as defined in claim 1, wherein said inductive reactance is the primary winding of a spark coil.

10. A combination as defined in claim 1, wherein said inductive reactance is the primary winding of a transformer, said transformer having a secondary winding, and an ignition capacitor connected to be charged by said secondary winding.

Description:
BACKGROUND OF THE INVENTION

The invention relates to an ignition arrangement for internal combustion engines.

In one prior art scheme a direct current circuit containing an inductive reactance is periodically opened by means of a transistor switching circuit. An arrangement of this kind is greatly heated not only by the operation of the internal combustion engine but also by the heat loss in the control resistors of the circuit. Consequently, the highly temperature sensitive transistor circuit does not always ensure the desired switching reliability, and, moreover, poses difficulties as to where it should be placed.

SUMMARY OF THE INVENTION

An object of the invention is appreciably to reduce the heat acting on the transistor switching circuit, particularly the heat caused by the control current.

The invention broadly comprises a circuit having a source of direct current, such as the battery of an internal combustion engine, and at least two transistors connected together to have a current gain that is the product of their individual current gains, means for generating high-voltage pulses for firing spark plugs, the means including an inductive reactance connected in the emitter-collector path of one of the transistors as the load common to the transistors, and means for periodically opening the circuit in synchronism with the operation of the engine.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a circuit of one embodiment of the invention, as applied to a spark coil ignition;

FIG. 2 is a view in section of a distributor housing with the ignition circuit and connector arrangement;

FIG. 3 is a detail view of another embodiment of the combination of distributor housing, shown in section, the ignition circuit, and the connector arrangement;

FIG. 4 shows a circuit of another embodiment, as applied to an ignition system having a capacitor.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The circuit shown in FIG. 1 has a direct current source 11, such as the battery of the internal combustion engine, not shown. The ignition circuit uses the principle of an ignition, or spark, coil. When the operating switch 12 is closed (and the engine is running), the source 11 is connected to a direct current circuit containing an inductive reactance 13. In this embodiment the inductive reactance consists of the primary winding 14 of a spark coil 15. The secondary winding 16 of this coil is connected in turn to each of the spark plugs 20, 21, 22 and 23 of the engine's cylinders by the rotating arm 19 rigidly fixed to the turning shaft 17 of the ignition distributor 18 of the engine.

A transistor switch 24 ensures that the direct current circuit of the winding 14 is broken in synchronism with the ignition strokes of the pistons. The switch 24 comprises two transistors T1 and T2 connected together to have a common load and a current gain that is the product of their individual current gains. The specific connection shown is the Darlington; and the load, comprised by the primary winding 14, is connected in the emitter-collector path E1-C1 of the transistor T1. The emitter E1 of this transistor is therefore connected through a connector 25, a lead 25' forming part of the connector 25, the primary 14, the lead 26, and the operating switch 12 to the positive pole of the source 11. The collector C1 of this same transistor is connected to the negative pole of the source by the ground wire 27. The base B1 is connected to the emitter E2 of transistor T2, of which latter the collector C2 is connected to the collector C1. The base B2 is connected by a control resistance 28 and a lead 29 to a control arrangement 30 connected to the ground wire 27. The control arrangement preferably a make-and-break switch 31, which is operated by a cam 32 on the distributor shaft 17.

If the make-and-break switch 31 is closed, the two emitter-collector paths E2-C2 and E1-C1 are conductive, so that current from the source 11 flows through the primary 14 of the spark coil 15. At the desired moment of ignition in a cylinder, the cam 32 opens the switch 31, causing the potential at the base B2 to fall and thereby the two emitter-collector paths E2-C2 and E1-C1 to become nonconductive. Consequently, there appears across the secondary winding 16 of the spark coil 15 a high-voltage pulse, which the rotating distributor arm 19 conducts to one of the four spark plugs 20 to 24. In Fig. 1 the pulse is conducted to the spark plug 23, where the resulting spark ignites the compressed fuel-air mixture.

Since the two transistors T1 and T2 are connected together in a Darlington connection, the control resistance 28 can have a relatively large value, which ensures that very little of the control current is converted into heat. There is no difficulty, consequently, to incorporate the two transistors T1 and T2 as an integrated circuit in a tiny electronic unit, which is made part of the ignition distributor 18.

A suitable constructional arrangement for the unit 33 is shown in FIG. 2. The electronic unit 33 and the connector 25 comprises a unitary part, which is mounted on the distributor housing 34 and has a portion 35 that extends outside of the distributor housing. The portion 35 is a terminal to which the primary winding lead 25' is connected. The connector 25 is constructed as a screw, which has a head 37 containing the unit 33 and engaging the inner wall surface 36 of the housing 34 and which also has a threaded shank 38, which is the terminal 35. Two nuts 39 and 40 are screwed onto the shank 38. The nut 39 holds the unit 33 fast against the housing 34, and the nut 40 clamps in place the lead 25'. The lead 29 is mechanically held on the screwhead 37 and connected to the unit 33 in accordance with the wiring diagram of FIG. 1.

Another advantageous arrangement of the unit 33 is shown in FIG. 3. The connector 125 is constructed as a heat-dissipating body and fixed to the outside of the distributor housing 34. In addition to the terminal 135 for the lead 25', the connector 125 has for the lead 29 a terminal 41, which extends into the interior of the housing 34. Both terminals 35 and 41 are preferably flat plugs.

If the ignition arrangement is to incorporate a circuit for suppressing interference pulses caused by chattering of the contacts of the switch 31, it can be made as an electronic unit and built into, or as part of, the connector 25 or 125, as is the unit 33.

The invention can also be employed, as shown in FIG. 4, in an ignition circuit based upon the discharge of a capacitor charged to a high voltage. The direct current circuit, the made-and-break arrangement therefor, and the corresponding reference numerals are unchanged from FIG. 1. In this embodiment the inductive reactance 13 is formed by the primary winding 42 of a charging transformer 43, of which latter the secondary winding 44 is connected through a diode 45 to the ignition capacitor 46. The capacitor is shunted by a series circuit consisting of the primary 47 of the spark coil 48 and the switching path A-K of a thyristor 49. The spark coil secondary 50 is connected to the spark plugs 20 to 23 in the same way as is the secondary 16 in the circuit of FIG. 1. The thyristor has a gate S, which triggers the thyristor to conduct along the path A-K when it receives a positive pulse 51.

The resulting high-voltage pulse across the secondary 44 whenever the make-and-break switch 31 is opened charges the capacitor 46 through the diode 45. At the desired moment of ignition the thyristor gate S receives a positive pulse 51, which renders the switching path A-K conductive and so enables the capacitor 46 to discharge through the primary winding 47 of the spark coil 48. The high-voltage pulse appearing across the secondary 50 is conducted to one of the spark plugs 20 to 23, as in the embodiment shown in FIG. 1.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of ignition arrangements differing from the types described above.

While the invention has been illustrated and described as embodied in ignition arrangements for internal combustion engines, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.