Control Unit Modifiable Engine Ignition Control Apparatus

This application is related to co-pending U.S. patent application Ser. No. 393,321 entitled "Engine Ignition Control Circuit". This application is also related to two U.S. patent applications filed concurrently herewith having U.S. patent application Ser. No. 433,913 and entitled "Engine Ignition Interpolation Apparatus", and U.S. patent application Ser. No. 433,912 and entitled "Input/Output Unit Modifiable Engine Ignition Control Apparatus" and based on Japanese Patent Applications Numbered 160912/81 and 160913/81, respectively.

The present invention relates to an apparatus for controlling ignition timing for an engine, and more particularly to an engine ignition control apparatus easily adaptable to a variety of engines having different numbers of cylinders and reference position sensors.

Recent rapid developments in electronics technology have resulted in an increased tendency for engine ignition timing to be controlled by a digital system. For example, an electronic engine ignition control circuit for two-wheeled motorcycles is supplied with crank angle pulses generated each time the crank shaft rotates through a unit angle and reference position pulses indicative of a reference position of the crank shaft. The control circuit counts and processes the crank angle pulses with the reference position pulses being used as references for determining a dwell angle and for controlling ignition timing.

There are many kinds of engines available which have different numbers of cylinders and reference position sensors. It has been customary to provide as many different engine ignition control devices as there are varying kinds of engines. Therefore, fabricating and keeping a variety of such engine ignition control devices has been quite time-consuming and tedious.

It is an object of the present invention to provide an engine ignition control apparatus easily adaptable to all types of engines.

It is another object of the present invention to provide a control unit for each reference position sensor.

It is a further object of the present invention to provide interchangeable control units.

According to the present invention, the above objects can be achieved by an engine ignition control apparatus divided into an input-output unit comprising: an input-output section having an input signal device and as many drivers as there are ignition coils to be controlled; and a controller comprising a single or a combination of control units each supplied with an output from a reference position sensor and each for controlling the associated ignition coil in a 1 to 1 correspondence.

These together with other objects and advantages which will be subsequently apparent, reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like reference numerals refer to like parts throughout.

FIG. 1 is a block diagram of an engine ignition control apparatus according to an embodiment of the present invention;

FIG. 2, including FIGS. 2(a)-2(c), are block diagrams of engine ignition control arrangements adapted to a variety of engines;

FIG. 3 is a more detailed circuit diagram of one of the control units 10 of FIG. 1;

FIG. 4 is a detailed circuit diagram of one of the drivers 5 of FIG. 1;

FIG. 5 is a detailed circuit diagram of a square wave circuit 20 of the shaper circuit 2 of FIG. 1;

FIG. 6 is a detailed circuit diagram of a trailing edge deletion circuit 21 of the shaper circuit of FIG. 1; and

FIG. 7 is a flow chart for the control of CPU 11 of FIG. 1.

FIG. 1 is a circuit diagram of an engine ignition control apparatus according to an embodiment of the present invention. The engine ignition control apparatus is shown as being incorporated into an engine for a two-wheeled motorcycle which has six in-line engine cylinders, the engine has three reference position sensors 14a-14c and six ignition coils that are grouped into three ignition coil assemblies (6 and 7). The engine ignition control apparatus includes a single input-output module or unit 1 with an input/output section 1--1 having a group of input ports A.sub.1 -A.sub.3 for receiving three different reference position pulses, an input port A.sub.4 for receiving crank angle pulses from a crank angle sensor 15, and an input port A.sub.5 for receiving a vacuum signal from the vacuum sensor 16. The reference position pulses and crank angle pulses supplied to the input ports A.sub.1 -A.sub.4 are shaped into rectangular pulses by a waveform shaper 2. A sensor failure interpolator 3 serves to interpolate reference position pulses when one or more sensors fail, so that the engine continues to run. The vacuum signal supplied through the input port A.sub.5 is converted into a digital signal by an analog-to-digital converter 4. Drivers 5a-5c are supplied with ignition timing signals from control units 10a-10c (described later) for driving ignition coils 6a-6c via output ports B.sub.1 -B.sub.3, respectively. Ignition plug combinations 7a-7c are supplied with high voltage outputs from the ignition coils 6a-6c, respectively, and each of the ignition plug combinations 7a-7c comprising two ignition plugs connected parallel and mounted respectively in engine cylinders operable in opposite strokes. A power supply circuit 9 serves to convert the output from a battery 8 into a stable voltage of +5 V to be supplied to the semiconductor devices.

The input-output unit 1 also includes a controller 1-2 having control units 10a-10c each supplied with the reference position pulses via the sensor failure interpolator 3, the crank angle pulses via the waveform shaper 2, and the vacuum signal via the analog-to-digital converter 4 and is for controlling the ignition coils 6a-6c in a 1:1 correspondence with the reference position sensors 14a-14c. Each of the control units 10a-10c comprising a central processing unit (hereinafter referred to as a CPU) 11, a data selector 12, and a failure detector 13.

FIG. 3 illustrates in more detail the control units 10a-10c of FIG. 1. CPU 11 receives the respective reference signal from the sensor failure interpolator 3 and provides an ignition signal to data selector 12. Data selector 12 selects either the ignition signal from the CPU 11 or the reference signal from the interpolator 3 based on the selection control signals from the failure detector 13. The data selector 12 comprises the needed OR gates and AND gate necessary to select and produce an ignition signal for the respective driver. The failure detector 13 includes a monitor circuit 18 which monitors the operating state of the CPU 11 to determine whether CPU 11 is running away or out of control and which monitors a low voltage detection signal produced by the low voltage detector 17. The failure detector provides the selection control signals to the data selector 12 and a reset control signal to a reset circuit 19. The reset circuit resets the CPU whenever a malfunction occurs. The low voltage detector 17 monitors the battery and generates the low voltage detection signal whenever the battery falls below a predetermined potential.

FIG. 4 is a detailed circuit diagram of the drivers 5a-5c. The driver 5 receives the ignition signal from the data selector 12 and drives the respective coil 6 to spark the respective plugs 7.

FIGS. 5 and 6 illustrate the details of the circuits comprising the waveform shaper circuit 2. The reference and crank angle signals generated by the reference sensors 14 and crank sensor 15 are shaped into square waves by square wave circuit 21 of FIG. 5. The square waves have their trailing edges detected by individual trailing edge detection circuits 21 of FIG. 6. The trailing edge detection circuit 21 produces a narrow pulse which is sent to the sensor failure interpolator 3.

The sensor failure interpolator 3 includes the counters and logic circuits required to count the crank angle pulses to determine if a reference position pulse is absent and produce a replacement pulse. An interpolator circuit adaptable as the sensor failure interpolator 3 is disclosed in the related U.S. patent application previously mentioned entitled "Engine Ignition Interpolation Apparatus" incorporated by reference herein.

The engine ignition control apparatus thus constructed will operate as follows. The reference position pulses supplied to the input ports A.sub.1 -A.sub.3 of the input-output unit 1 are shaped by the waveform shaper 2, and supplied as parallel signals through the sensor failure interpolator 3 to the CPU 11 in each of the control units 10a-10c. The crank angle pulses are supplied through the waveform shaper 2 to the CPU 11, and the vacuum signal is supplied through the analog-to-digital converter 4 to the CPU 11. Each of the control units 10a-10c is constructed to receive the reference position pulses supplied to the input ports A.sub.1 -A.sub.3, the crank angle pulses supplied to the input port A.sub.4 and the vacuum signal supplied to the input port A.sub.5. The CPU 11 in each of the control units 10a-10c is responsive to the predetermined outputs from the reference position sensors for processing the crank angle pulses and the vacuum signal to issue an optimum ignition timing signal, which is supplied to each of the drivers 5a-5c via the data selector 12 in the respective control units 10a-10c. In response to the supplied timing signal, the drivers 5a-5c, respectively, energize the ignition coils 6a-6c coupled to their outputs to enable the ignition coils to supply high voltage outputs for ignition to the ignition plug combinations 7a-7c.

Engines for use on two-wheeled motorcycles are classified by the number of reference position sensors and the number of output drivers as shown in the following Table 1:

As shown above, the number of reference position sensors is equal to the number of output drivers, that is, the number of ignition coil/plug pair combinations. Each of the output drivers can be controlled in a 1:1 correspondence with a reference position sensor by a single control unit. Therefore, the controller 1-2 in the ignition control apparatus can control all kinds of engines by providing as many control units as necessary. Since the controller 1-2 is of a complicated construction including expensive CPUs and other components, it would be undesirable from the standpoint of fabrication, maintenance and storage if there were as many different controllers as there are kinds of engines. With the arrangement of the present invention, however, the controller comprises a combination of control units each for controlling its associated ignition coil in a 1:1 correspondence with respect to a reference position sensor. Accordingly, an ignition control apparatus adaptable for all kinds of engines can be constructed by combining control units of the same construction and an input-output section suitable for a particular type of engine used. The length of cables connected between the engine and the ignition control apparatus varies with applications. To cope with this, only the input-output unit would be changed without requiring any alteration in the controller which would otherwise result from a change in the length of the cables.

FIGS. 2(a)-2(c) illustrate different arrangements respectively for the engine types I through III shown in the Table 1. Where only a single reference position sensor and single ignition coil are employed as with the type I, an input-output unit 1a having a single driver 5a is combined with a single control unit 10a as illustrated in FIG. 2(a). For two reference position sensors and two ignition coils, an input-output unit 1b having two drivers 5a and 5b is associated with two control units 10a and 10b as shown in FIG. 2(b). For three reference position sensors and three ignition coils, a combination of three drivers 5a-5c and three control units 10a-10c are employed, as illustrated in FIG. 2(c). Therefore, the controllers may contain one or more control units each having a minimum capacity to control a single ignition coil. Accordingly, the control units can be shared by an increased number of applications.

FIG. 7 is a flowchart for a control program capable of operating the CPU 11. The CPU 11 can be the well known 8048 eight bit microprocessor produced by Intel or NEC. The flow chart illustrates that the reference position pulses are used to initiate the counting of the crank angle pulses. When the crank angle pulse count reaches a predetermined value an ignition signal is output and the CPU 11 waits for another occurrence of the proper reference position pulse. The issuance of the ignition signal with the proper timing and dwell angle depends not only on the crank angle count but on the vacuum signal. In order to facilitate proper issuance of the ignition signal a table look-up method executed by the CPU using a local read only memory containing angle count and vacuum signal indexes can be used.

With the engine ignition control apparatus of the present invention, as described above, the controller comprises a single or a combination of control units each for controlling a single ignition coil, and the portion of the apparatus which is shared by various applications is enlarged. The engine ignition control apparatus can easily be fabricated, maintained and stored, and its adaptability to various engines is improved.

The many features and advantages of the invention are apparent from the detailed specification and, thus, it is intended by the appended claims to cover all such features and advantages of the apparatus which fall within the true spirit and scope of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation illustrated and described, and accordingly all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.