Internal-combustion engine starter device

Abstract: Starter device comprising an electric starter motor (3) and a main switch (10) of the normally open type connected between a supply input (3b) of the electric motor (3) and a battery (7). The device comprises a main switch (10) activation circuit comprising a first and a second switches (15, 16) arranged in series with each other and connected between the battery (7) and a main switch (10) activation device. The first switch is in the form of a manually operated switch operated by an ignition key (20) and the second switch (16), of the normally open type, is closed by a power enable signal output by an electronic control circuit (22) designed to inhibit the production of the enable signal when the voltage of the battery (7) falls below a threshold value. An electrical connection device extends between the supply input (12a) of the main switch (10) and a control input (16i) of the second switch (16) in order to provide a supply voltage to the control input and keep the second switch (16) closed independently of the production of the enable signal.

Description: The present invention relates to an internal-combustion engine starter device. There are starter devices for internal-combustion engines in the prior art comprising an electric starter motor able to turn the crankshaft and a main power switch connected between a starter motor activation input and the battery of a motor vehicle. For instance US-4,896,637 describes an engine starter wherein an electromagnetic relay switch is interposed between a battery and a DC electric motor. This main switch is of the normally open type and is usually a relay with an energizing solenoid which, when energized, causes the main switch to close. The starter device also includes, for the main switch, a supply circuit comprising a first switch and a second switch arranged in series with each other and connected between the battery and the solenoid; in particular the first switch is conveniently in the form of a manually operated switch incorporated in an ignition switch for starting the vehicle, operated by an ignition key. The second switch, which may take the form of a relay, is of the normally open type and is made to close by a power enable signal produced by an electronic control circuit and sent to a control input of the second switch. The electronic control circuit is powered by the battery and is designed to inhibit the production of the enable signal when the supply voltage to the electronic circuit falls below a threshold value. In order to start the engine, the first switch is closed for a few seconds, thus energizing the solenoid and so closing the main switch and turning the electric motor; during this cranking phase the second switch is normally kept closed by the electronic control circuit. During the cranking of the internal-combustion engine, the electric motor draws a heavy current from the battery (of the order of a hundred amps) and the voltage of the battery may fall below its rated value (normally 12 volts); for this reason the voltage supplied to the control circuit may itself fall below the threshold value, causing the immediate opening of the second switch and consequently cutting out the starter motor. Clearly, if the starter motor cuts out before the internal-combustion engine is self-sustaining, it will be impossible to start the latter. The object of this invention is to provide a starter device capable of keeping the electric starter motor turning even when the electronic control circuit produces a signal causing the second switch to open and consequently cutting out the starter motor. According to the present invention an internal-combustion engine starter device of the type described in Claim 1 is provided. The invention will now be described with reference to the accompanying drawings, which illustrate a non-limiting example of an embodiment thereof, in which: Figure 1 is a schematic of a starter device for an internal-combustion engin made in accordance with the teaching of the present invention and Figure 2 shows a variant of the device shown in Figure 1. In Figure 1 the reference numeral 1 denotes the whole of a starter device in which an electric motor 3 (shown schematically) is able to start an internal-combustion engine (not shown) such as a petrol engine in a vehicle (not shown). The electric starter motor 3 has a first terminal 3a connected to a reference potential 5 (earth) and a second terminal 3b that can be connected by a power line 6 to the positive pole (+) of a power source 7, which will conveniently b the battery of the vehicle (not shown). The starter device 1 comprises a power switching device 10 housed in the casing (not shown) of the motor 3 and arranged on the power line 6 between the power source 7 and the terminal 3b; the switch device 10 is of the normally open type and, when kept closed, allows a power current I a to pass from the battery 7 to the starter motor 3. More specifically, the switch device 10 may advantageously take the form of a relay comprising a solenoid (shown schematically) acting on a movable element (not shown) capable of moving an electric contact 14 between a rest position in which the solenoid is not energized and the switch device 10 is open, and an activated position in which the switch device 10 is closed while a supply voltage of a few volts is applied to the solenoid. The starter device 1 also comprises a circuit for activating the switch device 10 comprising first and second switches 15 and 16 arranged in series with each other on an electric line 7 that extends between the positive terminal (+) of the battery 7 and a first terminal 12a of the solenoid 12, which also has a second terminal 12b connected to the reference potential 5. The first switch 15 is conveniently in the form of a manually operated switch incorporate in an ignition switch for starting the vehicle, operated by an ignition key 20. The second switch 16 comprises a relay with a control input 16i connected, via a separating diode 24, to an output 22u of an ignition control circuit 22 (of known type). The relay 16 comprises an electric contact 16a that can be moved between a rest position in which the relay is not energized and the switch 16 is open, and an activated position in which the relay 16 is energized and the switch 16 is closed. The ignition control circuit 22 (of known type) is powered by the battery 7 and its input receives a plurality of electrical signals measured in the engine/in the vehicle and delivers enable and/or control signals through its output; in particular, where the signals fed to the input of the circuit 22 identify a situation of normal running of the engine, an ignition enable signal is delivered at the output 22u allowing the relay 16 to be energized and thus closing the switch formed by this relay. Among the various functions performed by the circuit 22 is a safety function whereby, if the supply voltage to the circuit 22 falls below a threshold value, the production of the ignition enable signal is inhibited, thus de-energizing the relay 16 and causing the switch represented by this relay 16 to open as a consequence. In the present invention the starter device 1 comprises an electrical connection device 27 extending between the control input 16i of the second switch 16 and the terminal 12a of the solenoid 12; in the preferred embodiment shown in Figure 1 the electrical connection device 27 comprises a diode 29 whose anode is connected to the terminal 12a and whose cathode is connected to the control input 16i. The diode 29 allows current to flow from the terminal 12a to the control input 16i of the second switch 16 but prevent it from flowing in the opposite direction. When in use, in conditions of normal running of the engine and where the supply voltage to the circuit 22 exceeds the threshold value, the control circuit 22 produces an ignition enable signal that causes the switch 16 to close; in this situation, as a result of the closure of the switch 15, the solenoid 12 is energized, which causes the power switching device 10 to close and consequently supplies power to the electric motor 3 which then cranks the crankshaft (not shown) of the internal-combustion engine (not shown . During the cranking of the internal-combustion engine, the electric motor 3 draws a heavy current (normally of the order of a hundred amps) which flows from the battery 7 along the power line 6. During this cranking phase, the voltage of the battery 7 may fall below the rated value, causing the voltage supplied to the control circuit 22 to fall below the threshold value; in this situation the production of the enable signal is inhibited and the circuit 22 ceases to provide a supply voltage to the relay 16 which, if it were supplied only by the control circuit 22, would be de-energized. In the present invention the control input 16i is also connected to the battery 7 through the electrical connection device 27 (diode 29), the second switch 16 (which is closed) the first switch 15 (which is kept closed during cranking) and the power line 17; therefore, after the switches 15 and 16 have closed, and even if the circuit 22 as ceased to provide the activation signal, the relay 16 continues to be energized because the voltage for its activation is being drawn downstream of the switches 15 and 16, which are closed and connected to the battery 7. When the first switch 15 is opened the second switch 16 is however de-energized and comes open. The starter device shown in Figure 2 differs from that illustrated in Figure 1 in that the second switch takes the form of a solid-state electronic device, such as a MOS transistor, and i that the second switch is internal to the control circuit 22. The drawing also shows a resistor 32 connected between the control input 16i and the diode 29 and a resistor 33 with one terminal connected to the input 16i a d another terminal receiving the enable signal. The way this device works is exactly the same as the device shown in Figure 1 and, for brevity's sake, will not be repeated here. The first switch 15 could also be non-manual and could take the form of an automatically operated electronic switch - for example a switch controlled by an electronic control system designed to extinguish the engine automatically when the vehicle stops at traffic lights and start the engine automatically when the accelerator pedal is operated (the so-called START/STOP function).

Claims: Internal-combustion engine starter device of the type that comprises: an electric starter motor (3) and main switch means (10) connected between a supply input (3b) of said electric starter motor (3) and a voltage source (7), in particular a motor vehicle battery, said main switch means (10) being of the normally open type and having actuator means (12) which, when energized, cause said main switch means (10) to close; said starter device (1) also comprising means (17, 15, 16) for activating said main switch means (10) comprising first and second switch means (15, 16) a ranged in series with each other and connected between said voltage source (7) and said actuator means (12); said second switch means (16) being of the normally open type and being made to close by a power enable signal produced by electronic control means (22) and sent to a control input (16i) of said second switch means (16); said electronic control means (22) being powered by said voltage source (7) the device being characterized in that said electronic control means is designed to inhibit the production of said enable signal when the supply voltage to said electronic control means falls below a threshold value; and that the device comprises electrical connection means (27, 29) communicating with a supply input (12a) of said actuator means (12) and with aid control input (16i) of said second switch means (16) in order to send a power signal to said control input (16i) as a result of the closing of said first and second switch means (15, 16) and to keep said second switch means (16) closed independently of the enable signal coming from said electronic control means (22); said electrical connection means allow current to flow from said supply input (12a) of said actuator means (12) to said control input (16i) of said second switch means (16) but prevent it from flowing in the opposite direction. Device according to Claim 1, characterized in that said electrical connection means comprise at least one diode (29) connected between said supply input (12a) of said actuator means (12) and said control input (16i) of said second switch means (16). Device according to any one of the previous claims, characterized in that said main switch means (10) comprise a relay with a solenoid (12) forming said actuator means. Device according to any one of the previous claims, characterized in that said second switch means (16) comprise a relay with a control input (16i) communicating with said electronic means (22) and with said electrical connection means (27, 29). Device according to any one of Claims 1 to 3, characterized in that said second switch means (16) comprise a semiconductor switch with a control input (16i) communicating with said electronic means (22) and with said electrical connection means (27, 29). Device according to any one of the previous claims, characterized in that said first switch means (15) are conveniently in the form of a manually operated switch incorporated in an ignition switch for starting the vehicle, operated by an ignition key (20).

Inventors: ALOTTO GIORGIO, SAPPE LEVI, ALOTTO, GIORGIO, SAPPE', LEVI
Applicants: MAGNETI MARELLI SPA, MAGNETI MARELLI S.p.A.
Application year: 1997
Main classification: F02N11
IPC codes: F02N11