GB2108587A - Engine starting system - Google Patents

Abstract

A starting system for an internal combustion engine 1, comprising a cranking motor assembly 4, a starter switch circuit 12 having a series combination of a cranking-motor switch 16 and a motor cut-off switch 17 connected between electrical power source 13 and the cranking motor assembly 4, an engine-speed sensor 25 to produce a signal representative of the detected revolution speed, and a control circuit 18 operative to produce a signal when the detected revolution speed is higher than a predetermined value to cause the cut-off switch 17 to open. <IMAGE>

Description

SPECIFICATION Engine starting system Field of the Invention The present invention relates to an engine starting system for an internal combustion engine of an automotive vehicle.

Background of the Invention An internal combustion engine of, for example, an automotive vehicle is usually equipped with a cranking motor connected to a power source across a normally-open cranking-motor switch.

The cranking motor has a pinion gear axially movable into and out of engagement with a driven gear rotatable with the output shaft of the engine.

When the cranking-motor switch is closed manually by the vehicle drive, the cranking motor is actuated and the pinion gear of the motor is brought into engagement with the driven gear on the engine output shaft so that the engine is started for operation. With such an internal combustion engine, the vehicle driver may happen.

to turn on the cranking-motor switch although the engine has already been started by the cranking motor. When this occurs, the pinion gear of the cranking motor is brought into engagement with the driven gear on the output shaft of the engine in operation. In this instance, the pinion gear of the cranking motor is unable to follow the rotation of the engine output shaft rotating at a high speed so that a damage may be caused to the pinion gear or the driven gear on the engine output shaft or a failure may be invited in the cranking motor.

In order to avoid such an accident, an engine cranking motor system has been proposed which cannot be actuated unless the cranking-motor switch which has once been closed is made open.

A problem has however been experienced in such a prior-art engine cranking motor system in that, when the cranking motor fails to start the engine, the cranking-motor switch must be turned off repeatedly until the engine is started. The present invention contemplates provision of a solution to this problem.

Summary of the Invention In accordance with the present invention, there is provided an engine starting system for an internal combustion engine having an output shaft, comprising a cranking motor assembly operative to drive the engine when electrically actuated, a starter switch circuit comprising a power source and a series combination of a cranking-motor switch and a motor cut-off switch electrically connected between the power source and the cranking motor assembly, detecting means operative to detect the revolution speed of the output shaft of the internal combustion engine and to produce a signal representative of the detected revolution speed, and a control circuit electrically connected to the motor cut-off switch and the detecting means and operative to produce an electric signal when the revolution speed represented by the signal produced by the detecting means is higher than a predetermined value and to cause the cut-off switch to open by the electric signal. In an engine starting system thus constructed and arranged, the motor cut-off switch preferably comprise a relay unit having normally-closed contact elements electrically connected between the cranking motor assembly and the power source across the cranking-motor switch and an actuating coil electrically connected to the control circuit.

Brief Description of the Drawing The features of an engine starting system according to the present invention will be more clearly understood from the following description taken in conjunction with the accompanying drawing which schematically shows a preferred embodiment of the system according to the present invention.

Description of the Preferred Embodiment Referring to the drawing, an engine starting system embodying the present invention is shown provided for an internal combustion engine 1 having an output shaft 2 carrying an externally toothed ring gear 3. The engine starting system comprises a cranking motor assembly 4 having a cranking motor unit 5 and a solenoid-operated shifting unit 6. The cranking motor unit 5 has an output shaft 7 having carried thereon a pinion gear 8 which is rotatable with the shaft 7. The pinion gear 8 is axially movable on the shaft 7 into and out of engagement with the ring gear 3 on the output shaft 2 of the engine 1. The shifting unit 6 has an axially movable actuating rod 9 pivotally connected at its leading end to one end portion of a shift lever 10 which is rotatable about a pivot pin 11 secured to, for example, the casing of the cranking motor assembly 4.The shift lever 10 has the other end portion pivotally connected to or otherwise engaged by an axial extension of the pinion gear 8 on the shaft 7. Though not shown in the drawing, the shifting unit 6 has incorporated therein a spring-loaded plunger which is in part coaxially surrounded by a solenoid coil. The spring-loaded plunger is connected to or integral with the actuating rod 9 which is accordingly biased to axially move in a direction to turn the shift lever 10 about the pivot pin 11 in a direction to move the pinion gear 8 into a predetermined axial position disengaged from the ring gear 3.

When the solenoid coil of the shifting unit 6 is energized, the actuating rod 9 is driven to protrude from the shifting unit 6 so that the shifting lever 10 is caused to turn about the pivot pin 11 in a direction to move the pinion gear 8 into a predetermined axial position held in mesh with the ring gear 3.

The cranking motor assembly 4 as above described is operated by a starter switch circuit 1 2 comprising a power source 1 3 having negative and positive terminals 14 and 14'. The power source 1 3 is constituted by, for example, a battery connected to a battery charge or alternator (not shown) to be driven by the output shaft 2 of the engine through, for example, a suitable belt-andpulley mechanism. The terminals 14 and 14' of the power source 1 3 are electrically connected to the cranking motor assembly 4 through lines 1 5 and 15', respectively, with a normally-open cranking-motor switch 1 6 and a normally-closed relay unit 1 7 provided in, for example, the line 15 as shown.The relay unit 1 7 constitutes a motor cut-off switch in the engine starting system according to the present invention and is composed of normally-closed contact elements 1 7a arranged in series with the cranking-motor switch 16 in the line 1 5 and an actuating coil 1 7b connected to a control circuit 1 8. The control circuit 18 has control terminals 19 and 19' connected to the actuating coil 1 7b through lines 20 and 20', respectively, and power supply terminals 21 and 21' connected to the negative and positive terminals 14 and 14' of the power source 13 through lines 22 and 22', respectively, with a normally-open accessory switch 23 arranged in, for example, the line 22 as shown.

The cranking-motor switch 1 6 and the accessory switch 23 are actuated by an ignition key (not shown) in such a manner that the accessory switch 23 first closes when the ignition key is manually turned through a predetermined angle from a predetermined rest position and the cranking-motor switch 1 6 closes when the ignition key is further turned beyond the predetermined angle. The control circuit 1 8 further has signal input terminals 24 and 24' connected to an engine-speed sensor 25 adapted to be responsive to the revolution speed of the output shaft 2 of the engine 1 and to produce signals representative of the revolution speed of the engine output shaft 2.Such an engine-speed sensor 25 may be constituted by an electromagnetic or photoelectric pickup device cooperative with a magnet-carrying or stroboscopic wheel 27 attached to the engine output shaft 2 as shown. The control circuit 1 8 is constructed and arranged in such a manner as to be operative to produce a control signal at the control terminals 1 9 and 19' thereof when the signal supplied from the engine-speed sensor 25 through the lines 26 and 26' is indicative of an engine output speed higher than a predetermined value. The predetermined value is preferably higher than the cranking speed of the engine output shaft 2 and lower than the idle speed of the engine output shaft 2.It may be possible to set the predetermined value higher than the idle speed of the engine output shaft 2 as the idle speed of the engine output shaft 2 is variable depending upon types of automatic transmission to be assembled to the engine.

When, now, the ignition key is held in the rest position thereof, the control circuit 1 8 is disconnected from the power source 13 with the accessory switch 23 kept open so that the actuating coil 1 7b of the relay unit 1 7 remains deenergized and permits the contact elements 1 7a to be closed. The cranking motor assembly 4 is also electrically disconnected from the power source 13 with the cranking-motor switch 1 6 kept open and thus remains inoperative with the pinion gear 8 held in the axial position disengaged from the ring gear 3.

When the ignition key is manually turned through a predetermined angle from the rest position thereof, the accessory switch 23 is closed so that the control circuit 1 8 is electrically connected to the power source 1 3 through the lines 22 and 22'. When the ignition key is further turned beyond the predetermined angle, the cranking--motor switch 1 6 is closed and provides electrical connection between the cranking motor assembly 4 and the power source 13 through the lines 1 5 and 15' with the normally-closed contact elements 1 7a of the relay unit 1 7 kept closed.The cranking motor assembly 4 being thus energized from the power source 13, the cranking motor unit 5 is actuated to drive the pinion gear 8 for rotation on the shaft 7 and, at the same time, the shifting unit 6 is actuated to drive the actuating rod 9 to axially retract. As a consequence, the shifting fork 10 is driven to turn about the pivot pin 11 in the direction to move the pinion gear 8 into the axial position in mesh with the ring gear 3. The engine output shaft 2 is thus driven for rotation by the cranking motor unit 5 through the pinion gear 8 and ring gear 3.

When the engine 10 thus started by the cranking motor assembly 4 is enabled to operate for itself and the ignition key is released from the manipulative effort which has been applied thereto, the cranking-motor switch 1 6 is automatically caused to open and disconnects the cranking motor unit 5 and the shifting unit 6 from the power source 13. The cranking motor unit 5 is thus brought to a stop and, simultaneously. the shifting unit 6 is de-energized to cause the actuating rod 9 to axially protrude forwardly. The shifting lever 10 is driven to turn in the reverse direction about the pivot pin 11 and causes the pinion gear 8 to move back into the axial position disengaged from the ring gear 3.

When the revolution speed of the output shaft 2 of the engine 1 as detected by the engine-speed sensor 25 reaches the predetermined value registered in the control circuit 18, the control circuit 1 8 produces an output signal and energizes the actuating coil 1 72b of the relay unit 17 through the lines 20 and 20'. The actuating coil 1 7b being thus energized, the normally-clpsed contact elements 17a of the relay unit 1 7 are made open and thereby holds the cranking motor assembly 4 disconnected from the power source 1 3 independently of the cranking-motor switch 1 6. If the vehicle drive may accidentally or erroneously turn the ignition key into the position to close the cranking-motor switch 16, the cranking motor unit 5 and the shifting unit 6 are kept de-energized and are held inoperative.

According to the present invention as previously mentioned, the pinion gear of the cranking motor is by no means brought into engagement with the driven gear on the output shaft of the engine rotated at a high speed even if the vehicle driver happens to turn on the crankingmotor switch in the case that the engine has already been started by the cranking motor. This follows that a damage can be prevented with certainty to the pinion gear or the driven gear on the engine output shaft and that no failure may be invited in the cranking motor.

Claims (3)

1. An engine starting system for an internal combustion engine having an output shaft, comprising a cranking motor assembly operative to drive the engine when electrically actuated, a starter switch circuit comprising a power source and a series combination of a crankingmotor switch and a motor cut-off switch electrically connected between said power source and said cranking motor assembly, detecting means operative to detect the revolution speed of the output shaft of the internal combustion engine and to produce a signal representative of the detected revolution speed, and a control circuit electrically connected to said motor cut-off switch and said detecting means and operative to produce an electric signal when the revolution speed represented by the signal produced by said detecting means is higher than a predetermined value and to cause the cut-off switch to open by said electric signal.

2. An engine starting system as set forth in claim 1, in which said motor cutoff switch comprises a relay unit having normally-closed contact elements electrically connected between said cranking motor assembly and said power source across said cranking-motor switch and an actuating coil electrically connected to said control circuit.

3. An engine starting system for an internal combustion engine substantially as hereinbefore described with reference to the accompanying drawing.