GB2404461A

GB2404461A - Boosting generator output current when kickstarting engine

Info

Publication number: GB2404461A
Application number: GB0415471A
Authority: GB
Inventors: Toshiya Nagatsuyu; Tomokazu Sakamoto
Original assignee: Honda Motor Co Ltd
Current assignee: Honda Motor Co Ltd
Priority date: 2003-07-31
Filing date: 2004-07-09
Publication date: 2005-02-02
Anticipated expiration: 2024-07-09
Also published as: CN1581674A; FR2858489B1; JP4144744B2; GB2404461B; CN100345369C; FR2858489A1; GB0415471D0; JP2005048628A

Abstract

The output current of an engine driven, rectified alternating current generator is boosted during kick starting of the engine, when the crank angle corresponds to the piston being in the vicinity of top dead centre. Additional power is thereby provided when ignition 22 and injector 28 require most power, without increasing the generator torque at other crank angles. The current boosting means may comprise a boost chopper (fig 3, 44) and pulse generating means (fig 3, 53-55) which increases the on duty ratio of the switching means when the engine piston is near top dead centre.

Description

240446 1

OUTPUT CONTROL DEVICE FOR POWER GENERATOR

The present invention relates to an output control device for a power generator, which is capable of supplying a sufficient voltage to a fuel supply system and to an ignition system in spite of a small generated voltage when starting an engine and thereby enhancing an engine starting performance.

Japanese Unexamined Patent Publication No 8(1996)-5 l 731, entitled "Power supply for internal-combustion engine", discloses a generated voltage boosting method for boosting an output generated by a power generator for supply to a load in a fuel supply system and to other electric loads when starting an engine Fig. 3 of the above-mentioned publication describes a first power supply circuit 10 which includes a boost rectif er circuit 10a incorporating a MOSFET (F 1), a MOSFET (F2), and rectifying diodes D2 1 and D22 into a power generation coil Wp of a power generator, and a FET control circuit I Ob which is connected between direct current output terminals tl and t2 of this boost rectifier circuit 1 Oa and is configured to supply a driving signal Vg to respective gates of the MOSFET (F 1) and the MOSFET (F2) The boost rectifier circuit 1 Oa constitutes a bridge full-wave rectifier circuit by establishing bridge connection among the rectifying diodes D2 1 and D22, a parasitic diode Dfl provided between a drain and a source of the MOSFET (F I), and a parasitic diode Df2 provided between a drain and a source of the MOSFET (F2), performs on-and-off control, i e chopping control by providing the rectangular wave driving signal Vg from the FET control circuit 10b to the MOSFET (F1) and the MOSFET (F2) as a switching pulse, and thereby generates a high voltage on the power generation coil Wp Then, the direct current output obtained by rectifying this high voltage by the bridge full-wave rectifier circuit is supplied to a fuel pump 11.

In the technique according to the publication, the FET control circuit 10b is not activated due to a small voltage generated by the power generator when starting the engine, and a necessary voltage is not obtained when boosting is not performed.

Accordingly, it is not possible to operate the fuel pump 11 or an ignition system.

Even if the start is attempted, starting the engine takes a long time until the voltage is boosted To solve this technical problem, the applicant has filed a patent application (Japanese Unexamined Patent Publication No 2002 - 101697) related to a technique of providing an oscillator and a central processing unit as pulse supply sources for supplying a switching pulse to a boost chopper and selectively supplying either an oscillation pulse generated by the oscillator in a time period of a low starting voltage or a CPU pulse generated by the central processing unit when the starting voltage is increased respectively as the switching pulse When the generated voltage is boosted to supply a sufficient voltage to the fuel supply system and to the ignition system when starting the engine, production of electricity by the power generator is increased and driving torque is thereby increased Accordingly, a load on the engine is increased.

Meanwhile, as shown in Fig. 14, engine revolutions are temporarily reduced when the piston reaches a compression top dead center or in the vicinity thereof, and such an influence becomes significant at low engine revolutions when starting the engine Moreover, among the electric loads including the fuel pump, an injector, an igniter, and the like which are operated when starting the engine, the igniter in particular is electrically conducted when a crank angle approaches O" Accordingly, power consumption is increased in the vicinity of the crank angle of O" Therefore, it has been difficult to enhance an engine starting performance sufficiently only by boosting the generated voltage when starting the engine In addition, there also has been a technical problem that large force on pedal is required for kick-starting because the driving torque is increased due to the increase in production of electricity by the power generator upon the boost in the generated voltage when starting the engine It is an object of at least the preferred embodiment of the present invention to provide an output control device for a power generator which is capable of solving the above-described problems of the prior art and of obtaining a fine starting performance in spite of a small generated voltage when starting an engine.

To attain the above-described object, according to the present invention there is provided an output control device for a power generator configured to rectify an alternating current output from an alternator driven by an engine and to boost a direct current output after rectification, which is characterized by taking the following measures.

(l) Crank angle detection means for detecting a crank angle ofthe engine, and boosting means for boosting the direct current output when the engine is kick started depending on the detected crank angle are provided, and the boosting means is characterized by boosting the direct current output higher at a crank angle where a piston of the engine is located at a top dead center or in the vicinity thereof as compared to other crank angles The electric loads require large electric power at the crank angle where the piston is located at the top dead center or in the vicinity thereof Accordingly, it is possible to supply a sufficient voltage to the fuel supply system and to the ignition system by boosting the direct current output largely at the relevant time, and thereby to enhance the engine starting performance (2) The boosting means includes a boost chopper for chopping the direct current output by use of a switching pulse, and pulse generating means for supplying the switching pulse of a duty ratio corresponding to the detected crank angle to the boosting chopper, and the pulse generating means is characterized by increasing an on-duty ratio of the switching pulse higher at the crank angle where the piston of the engine is located at a compression top dead center or in the vicinity thereof as compared to other crank angles In this way, when the boost chopper is adopted as the boosting means, it is possible to boost the direct current output easily up to a desired voltage only by controlling the on-duty ratio of the switching pulse when the piston of the engine is located at the top dead center or in the vicinity thereof A preferred embodiment of the present invention will now be described by way of example only, and with reference to the accompanying drawings, in which Fig I is a side view of a motorcycle mounting a power supply device which embodies a generated voltage boosting method for a power generator according to the present invention; Fig. 2 is a side view of a substantial part of the motorcycle mounting the power supply device which embodies the generated voltage boosting method for a power generator according to the present invention, Fig. 3 is a circuit diagram of a power supply device according to the present invention; Fig 4 is an operation diagram describing the generated voltage boosting method by a generated voltage booster device according to the present invention; Fig 5 is a first graph describing the generated voltage boosting method according to the present invention; Fig 6 is a second graph describing the generated voltage boosting method according to the present invention, Fig 7 is a third graph describing the generated voltage boosting method according to the present invention; Fig 8 is a fourth graph describing the generated voltage boosting method according to the present invention; Fig 9 is a fifth graph describing the generated voltage boosting method according to the present invention, Fig 10 is a first flowchart of the generated voltage boosting method according to the present invention, Fig I 1 is a second flowchart of the generated voltage boosting method according to the present invention; Fig. 12 is a flowchart of procedures for setting an on-duty ratio of a CPU pulse to a value corresponding to a crank angle when kick-starting, Fig 13 is a timing chart of the procedures for setting the on-duty ratio of the CPU pulse to the value corresponding to the crank angle when kick-starting, and Fig 14 is a view for describing problems of the prior art Here, the drawings are assumed to be viewed in accordance with orientations of reference numerals Fig I is a side view of a motorcycle mounting a power supply device which embodies a generated voltage boosting method for a power generator according to the present Invention In motorcycle 10, a starter switch 12 is fitted to a handle I 1, a main switch 13 is disposed inside a front cover 14 and below the handle l l, a full transistor type ignition coil 16 for igniting an engine 15 and a battery 21 are disposed inside a body cover 18 below a seat 17, a kick pedal 25 as a kick-starter device is fitted to a power unit 24 provided with the engine 15 including an ignition plug 22 and an injector 28 and with a power transmission mechanism 23, and a fuel pump 27 as a fuel supply system is fitted inside a fuel tank (not shown) provided below a floor step 26. Here, reference numerals 31 and 32 denote a head lamp and a tail lamp as lamp loads Fig 2 is a side view of a substantial part of the motorcycle mounting the power supply device which embodies the generated voltage boosting method for a power generator according to the present invention, which illustrates the opposite side surface to the side surface of the motorcycle 10 shown in Fig I The power unit 24 is provided with an alternator 33, which also functions as a starter motor, in a position beside and below the body cover 18.

Fig 3 is a circuit diagram of the power supply device according to the present invention A power supply device 40 includes. the battery 21; a battery disconnecting relay 42 connected to this battery 21 through a main fuse 41; a starter relay 43 connected to this battery disconnecting relay 42 and to the battery 21, the alternator 33 connected to this starter relay 43 through a boost rectifier circuit 44; PET driving means 53 for driving FETs 45 to 50 constituting the boost rectifier circuit 44, an oscillator 54 and a computer 55 for supplying a pulse for chopping (chopping means an operation to convert a direct current into an alternating current, to amplify (boost) such an alternating state, and then to rectify the alternating output again into a direct current), the main switch 13 connected to the battery 21 side and to the alternator 33 side respectively through a first diode 56 and a second diode 57, the starter switch 12 provided respectively between this main switch and the starter relay 43; a general load 61, the fuel pump 27, the in jector 28, and the full transistor type ignition coil 16 to which electricity is supplied from the battery disconnecting relay 42 side through a sub fuse 58; switching elements 103 to 107 for switching an electric motor 74 of the fuel pump 27, the injector 28, the full transistor type ignition coil 16, the general load 61 and a coil 81 ofthe battery disconnecting relay 42, and a coil 86 of the starter relay 43, respectively; and controlling means 65 for performing on-and-off control of the respective switching elements 103 to 107 The starter switch 12 includes a first fixed contact 66 connected to the starter relay 43, a second fixed contact 67 connected to the main switch 13, and a traveling contact 68 which can be connected to these first and second fixed contacts 66 and 67 or disconnected from the first and second fixed contacts 66 and 67 The main switch 13 includes a fixed contact 71 connected to the controlling means 65, a traveling contact 72 which can be connected to this fixed contact 71 or disconnected from the fixed contact 71 and is connected to the battery 21 and to the alternator 33, and an antitheft switch unit 73 connected to the traveling contact 72.

The antitheft switch unit 73 is connected to an unillustrated antitheft device, which is turned on when the traveling contact 72 of the main switch 13 is connected to the fixed contact 71 (on) and is turned off when traveling contact 72 of the main switch 13 is disconnected from the fixed contact 71 (off) The fuel pump 27 includes the electric motor 74, and a pump body 75 which is driven by this electric motor 74 The alternator 33 is of a three phase alternating current generation type and is configured to retrieve outputs from stator coils 33a, 33a, and 33a The battery disconnecting relay 42 includes a switch unit 78 having a fixed contact 76 connected to the main fuse 41, and a traveling contact 77 which can be connected to this fixed contact 76 or disconnected from the fixed contact 76 and is connected to the starter relay 43, and a coil 81 for turning this switch unit 78 on and off The switch unit 78 is turned off when the coil 81 is not electrically conducted.

The starter relay 43 includes. a switch unit 85 having a first fixed contact 82 connected to the battery disconnecting relay 42, a second fixed contact 83 connected to the battery 21, and a traveling contact 84 which is connected respectively to these first and second fixed contacts 82 and 83 or disconnected from the first and second fixed contacts 82 and 83, and a coil 86 for switching connection of the traveling contact 84 to the first or second fixed contact 82 or 83 The traveling contact 84 is connected to the first fixed contact 82 when the coil 86 is not electrically conducted, and the traveling contact 84 is connected to the second fixed contact 83 when the coil 86 is electrically conducted The boost rectifier circuit 44 includes the above-mentioned FETs 45 to 50, diodes 91 to 96 connected between respective sources and drains of these FETs 45 to 50, and a capacitor 101 connected between output terminal units 97 and 98. The diodes 91 to 96 constitute a three phase full-wave rectifier circuit, and the FETs 45 to 50 constitute a switching circuit for chopping The FETs 45 to 50 are p-channel MOS FETs and are configured to control drain currents flowing between drains and sources with gate voltages which are applied between gates and the sources.

The FET driving means 53 is configured to receive the pulse from the oscillator 54 or the computer 55 and to provide rectangular wave driving signals Sd to the respective gates ofthe FETs 45 to 50 synchronously with a frequency of this pulse The oscillator 54 is activated when a voltage supplied from the battery 21 or from the alternator 33 reaches vl, and generates the oscillation pulse having a given amplitude, a given pulse width, and a given time interval, in other words, generates the oscillation pulse at a starting voltage equal to or greater than v 1 The computer 55 includes a central processing unit (CPU) 55a (hereinafter referred to as the "CPU 55a") This CPU 55a includes an unillustrated clock generator which generates a periodical pulse having a constant time Interval The CPU 55a is activated when the voltage supplied from the battery 21 or from the alternator 33 reaches v2, and generates a pulse (such a pulse will be herein referred to as a "CPU pulse") having a given amplitude, a given pulse width, and a given time interval based on the pulse from the clock generator, in other words, generates the CPU pulse at a starting voltage equal to or greater than v2 Moreover, whereas the CPU 55a generates the CPU pulse only for a given time period after staring generation of the CPU pulse, the CPU 55a is configured, when an ignition purser signal from an unillustrated ignition purser signal generation device is detected within the given time period, to continue generation of the CPU pulse even after the given time period until engine revolutions reach a given value or above, or until a battery voltage reaches a given value or above In addition, the CPU 55a is configured to terminate generation of the CPU pulse when the engine revolutions drop to a certain value or below or when the engine stops running.

The first diode 56 allows an electric current to flow only in the direction from the battery 21 to the main switch 13 side, and does not allow the electric current to flow in the direction from the alternator 33 to the battery 21 The second diode 57 allows an electric current to flow only in the direction from the alternator 33 to the main switch 13 side, and does not allow the electric current to flow in the direction from the battery 21 to the alternator 33 The general load 61 is an electric load other than a fuel supply system load such as the fuel pump 27 or the injector 28 and an ignition system load such as the full transistor type ignition coil 16 or the ignition plug 22. The general load 61 generally includes a lamp load such as the head lamp 31, the tail lamp 32, a turn signal lamp or an instrument light, and a horn BacktoFig.3,the switching elements 103, 104, 106,and 107 are FETs connecting diodes between respective drains and sources thereof, and the switching element 105 is a bipolar transistor The controlling means 65 is configured to be activated at a given voltage V supplied from the battery 21 or the alternator 33 by turning on the main switch 13, and to control respective gate voltages of the switching elements 103 to 107 so as to turn on or turn off spaces between the drains and the sources (or spaces between collectors and emitters) thereof Moreover, the controlling means 65 is configured to generate a control signal for operating the full transistor type ignition coil 16 A full transistor type ignition system is configured to conduct an electric current (a primary electric current) on a primary side of an ignition coil in advance, to suddenly cut offthe electric current conducted on the primary side of the ignition coil by use of a switching element such as a power transistor when energy is increased on the primary side ofthe ignition coil, to induce back electromotive force on the primary side of the ignition coil, to cause discharge of a high voltage which is generated on a secondary side of the ignition coil at that time, and to ignite fuel -air mixture inside the engine Here, the boost rectifier circuit 44, the FET driving means 53, the oscillator 54, and the computer 55 constitute a generated voltage booster device 110 The generated voltage boosting method by use of the above-described generated voltage booster device 110 will be explained below Fig 4 is an operation diagram describing the generated voltage boosting method by use of the generated voltage booster device according to the present invention First, the main switch 13 is turned on For example, when an electricity level of the battery 21 is low and the engine is not activated by turning the starter switch 12 on, kicking is started by stamping on the kick pedal 25 In this way, the alternator 33 starts rotation and power generation Then, the alternating current power generated by the alternator 33 is subjected to three phase full wave rectification by the boost rectifier circuit 44, and a direct current is outputted between the output terminal units 97 and 98 The voltage of this direct current output is applied to the oscillator 54 and to the computer 55 through the main switch] 3.

When the voltage is smaller than the starting voltage vl for the oscillator 54, power generation with the alternator 33 is continued by means of stamping on the kick pedal continuously In this way, the engine revolutions, i e revolutions of the alternator are increased and the generated voltage is gradually raised Eventually, the oscillator 54 starts generation of an oscillation pulse Pb when reaching the starting voltage vl for the oscillator 54 (the battery voltage becomes equal to vl in this event) As a result, the oscillation pulse Pb is applied to the FET driving means 53, and the FET driving means 53 respectively provides the rectangular wave driving signals Sd of the same phase at higher frequencies than an alternating current output frequency of the alternator 33 to the respective gates of the FETs 45 to 50 In this way, a high voltage alternating current is generated in each of the stator coils 33a, and the alternating current is subjected to full-wave rectification by the diodes 91 to 96 and is smoothed by the capacitor 101 That is, chopping is performed by the boost rectifier circuit 44 in accordance with the oscillation pulse Pb Thereafter, when the direct current voltage after rectif cation and smoothing reaches the starting voltage v2 for the CPU 55a which is higher than the starting voltage v 1 for the oscillator 54 (the battery voltage becomes equal to v2 in this event), the CPU 55a transmits a pulse stop signal Sp to the oscillator 54 to allow the oscillator 54 to terminate generation ofthe oscillation pulse Pb, and starts generation of a CPU pulse Pc As a result, the CPU pulse Pc is applied to the FET driving means 53 and chopping is performed again by the boost rectifier circuit 44, whereby the output voltage between the output terminal unit 97 and 98 is raised further When the output voltage between the output terminal units 97 and 98 reaches a given voltage v3 (the battery voltage becomes equal to v3 in this event), the CPU 55a stops generation of the CPU pulse Pc When the output voltage is raised as described above, it is possible to supply a sufficiently high voltage to the fuel pump 27 and the injector 28 which are the fuel supply system loads and to the controlling means 65 which operates the full transistor type ignition coil l 6 when starting the engine, and thereby to enhance an engine starting performance The reason for terminating generation of the oscillation pulse Pb by the l 0 oscillator 54 at the voltage v2 and terminating generation of the CPU pulse Pc by the CPU 55a at the voltage v3 is as follows Assuming that vl = 3 volts, v2 = 6 volts, and v3 = 8 volts, the oscillator 54 is most efficiently operated in a range from 3 volts to 6 volts and the CPU is most efficiently operated in a range from 6 volts to 8 volts Fig 5 is a first graph describing the generated voltage boosting method according to the present invention in the case where a battery voltage VB when starting the engine (the battery voltage becomes equal to the voltage generated by the alternator if the battery is connected to the alternator when starting the engine) is in a range defined as O < VB < vl (vl = 3V for example) Here, the longitudinal axis of the graph represents the battery voltage VB (unit: V), engine revolutions N (unit rpm), the ignition purser signal, an oscillation pulse generation signal, and a CPU pulse generation signal The transverse axis represents time T (unit msec).

The oscillation pulse generation signal and the CPU pulse generation signal represent that the oscillation pulse or the CPU pulse is not generated by the oscillator or the CPU at an L level, and that the oscillation pulse is generated by the oscillator and the CPU pulse is generated by the CPU at an H level Firstly, the main switch is turned on at time t l, and the kick pedal is stamped on at time t2 to start kicking In this way, the engine revolutions N are gradually increased. In conjunction therewith, the battery voltage VB is gradually raised by power generation of the alternator At time t3, when the battery voltage reaches vl which is the starting voltage for the oscillator, the oscillation pulse generation signal is switched from an off-state (the L level) to an on-state (the H level), i e the oscillator starts generation of the oscillation pulse The generated voltage is boosted by this oscillation pulse. When the battery voltage VB charged by this generated voltage is raised further and the battery voltage VB thereby reaches the VB = v2 which is the starting voltage for the CPU, the oscillation pulse generation signal is set to the off-state (the L level) and the CPU pulse generation signal is changed from the off-state (the L level) to the on state (the H level), i.e. the CPU causes to terminate generation of the oscillation pulse and starts generation of the CPU pulse.

At the point when the CPU pulse generation signal is turned on, a timer is activated, i.e starts increasing from elapsed time t= 0 When the ignition purser signal is detected in a period before the elapsed time t reaches given time Is, the CPU 55a continues generation of the CPU pulse even after the given time Is. When the engine revolutions N reach N = nl (1600 rpm, for example) at time t7 after starting the engine at time t6, the CPU terminates generation of the CPU pulse.

Here, if the battery voltage reaches VB = v3 before the engine revolutions reach N = nl, the CPU terminates generation of the CPU pulse at this point.

Fig 6 is a second graph describing the generated voltage boosting method according to the present invention in the case where the battery voltage VB when starting the engine is in a range defined as v 1 < VB < v2 (v 1 = 3 V and v2 = 6 V, for example). The longitudinal axis and the transverse axis of the graph are similar to Fig 5 Firstly, when the main switch is turned on at the time tl, the oscillator starts generation of the oscillation pulse simultaneously with turning the main switch on because the battery voltage VB is greater than vl which is the starting voltage for the oscillator. Thereafter, the kick pedal is stamped on at the time t2 to start kicking.

In this way, the engine revolutions N are gradually increased In conjunction therewith, the battery voltage VB is gradually raised by power generation of the alternator. At time tlO, when the battery voltage VB reaches VB = v2 which is the starting voltage for the CPU, the CPU causes the oscillator to terminate generation of the oscillation pulse and starts generation of the CPU pulse The timer is activated (the elapsed time t = 0) at the point of starting generation of the CPU pulse. When the CPU detects the ignition purser signal before the elapsed time t reaches the given time ts, the CPU 55a continues generation of the CPU pulse even after the given time Is When the battery voltage VB reaches VB = v3 at time tl 2, the CPU terminates generation of the CPU pulse.

Fig 7 is a third graph describing the generated voltage boosting method according to the present invention in the case where the battery voltage VB when starting the engine is in a range defined as v2 < VB < v3 (v2 = 6 V and v3 = 8 V, for example) The longitudinal axis and the transverse axis of the graph are similar to Fig 5 Firstly, when the main switch is turned on at the time tl, the oscillator starts generation of the oscillation pulse simultaneously with fuming the main switch on because the battery voltage VB is greater than vl which is the starting voltage for to the oscillator Moreover, since the battery voltage VB is also greater than v2 which is the starting voltage for the CPU, the CPU causes the oscillator to terminate generation of the oscillation pulse after given time tb from the point of starting generation of the oscillation pulse, and starts generation of the CPU pulse Here, generation of the l 5 CPU pulse is terminated at the given time Is because the CPU does not detect the ignition purser signal within the given time Is Thereafter, the kick pedal is stamped on at the time t2 to start kicking When the CPU detects the ignition purser signal, the CPU judges that the engine starts revolutions, and starts generation of the CPU pulse In this way, the engine revolutions N are gradually increased In conjunction therewith, the battery voltage VB is gradually raised by power generation of the alternator. When the battery voltage VB reaches VB = v3 at time tl 8, the CPU terminates generation of the CPU pulse Fig 8 is a fourth graph describing the generated voltage boosting method according to the present invention in the case where the battery voltage VB when starting the engine is in a range defined as v2 < VB v3 (v2 = 6 V and v3 = 8 V, for example) The longitudinal axis and the transverse axis of the graph are similar to Fig 5. Firstly, when the main switch is turned on at the time tl, the oscillator starts generation of the oscillation pulse simultaneously with turning the main switch on because the battery voltage VB is greater than vl which is the starting voltage for the oscillator.

Moreover, since the battery voltage VB is also greater than v2 which isthe starting voltage for the CPU, the CPU causes the oscillator to terminate generation of the oscillation pulse after given time tb from the point of starting generation of the oscillation pulse, and starts generation of the CPU pulse When the CPU detects the ignition purser signal at time t22 within the given time ts, the CPU continues generation of the CPU pulse after the given time ts.

However, when the battery voltage VB reaches v3 within the given time ts, the CPU terminates generation of the CPU pulse at the point of the given time ts Fig 9 is a f fth graph describing the generated voltage boosting method; according to the present invention in the case where the battery voltage VB when starting the engine is defined as VB 2 v3 (v3 = 8 V, for example) The longitudinal axis and the transverse axis of the graph are similar to Fig. 5 Firstly, when the main switch is turned on at the time tl, the oscillator starts generation of the oscillation pulse simultaneously with turning the main switch on because the battery voltage VB is greater than vl which is the starting voltage for the oscillator Moreover, since the battery voltage VB is also greater than v2 which is the starting voltage for the CPU, the CPU causes the oscillator to terminate generation of the oscillation pulse after the given time tb, and starts generation of the CPU pulse Here, generation of the CPU pulse Is terminated at the given time ts because the CPU does not detect the ignition purser signal within the given time ts.

Thereafter, the kick pedal is stamped on at the time t2 to start kicking.

Although the CPU detects the engine starting revolutions by means of the ignition purser signal, the CPU does not generate the CPU pulse because the battery voltage VB satisfies VB 2 SV Fig 10 is a first flow of the generated voltage boosting method according to the present invention Here, STxx indicates a step number STOl. The main switch is turned on ST02. Judgment is made as to whether the battery voltage VB < the given battery voltage value v3 is satisfied When VB < v3 is not satisfied (NO, i.e. VB 2 1 v3), the process is completed When VB < v3 is satisfied (YES), the process moves to ST03.

ST03 Judgment is made as to whether the battery voltage VB < the starting voltage for the CPU v2 is satisfied When VB < v2 is not satisfied (NO, i e. v2 < VB <v3), the process moves to ST04 When VB < v2 is satisfied (YES) , the process moves to ST10.

ST04. The oscillator starts generation of the oscillation pulse ST05. The CPU causes to terminate generation of the oscillation pulse and starts generation of the CPU pulse (the timer is activated (turned on) here (the elapsed time t = 0)) ST06. Judgment is made as to whether the elapsed time t = the given time ts is satisfied When t = ts is not satisfied (NO), the process moves to ST07 When t = ts is satisfied (YES), the process moves to ST08.

l O ST07 Judgment is made as to whether the kick is started When the kick is not started (NO), the process returns to ST06 When the kick is started (YES), the process moves to STl 8 in Fig. I I through a connector C ST08. The CPU terminates generation of the CPU pulse ST09 The kick is started ST 10. Judgment is made as to whether O < the battery voltage VB < the starting voltage for the oscillator v I is satisfied When O < VB < v I is not satisfied (NO, i e v l < VB < v2), the process moves to ST I I When O < VB < vl is satisfied (YES), the process moves to STI3 STI I The oscillator starts generation of the oscillation pulse STI2 The kick is started Thereafter, the process moves to ST16 STI3 The kick is started ST14 Judgment is made as to whether the battery voltage VB 2 vl is satisfied When VB 2 vl is not satisfied (NO), STI4 is executed again When VB 2 vl is satisfied (YES), the process moves to STI5 ST 15 The oscillator starts generation of the oscillation pulse STl 6 Judg,ment is made as to whether the battery voltage VB > the starting voltage for the CPU v2 is satisfied When VB 2 v2 is not satisfied (NO), ST16 is executed again ST l 7 The CPU causes the oscillator to terminate generation of the oscillation pulse and starts generation of the CPU pulse (the timer is activated (turned on) (the elapsed time t = 0)) Thereafter, the process moves to STl 8 in Fig 11 through the connector C Fig. 11 is a second flow of the generated voltage boosting method according to the present invention Here, STxx indicates the step number.

ST18. Judgment is made as to whether the elapsed time t = the given time ts is satisfied When t= ts is not satisfied (NO), the process moves to STI9 When t = ts is satisfied (YES), the process moves to ST21 STl9... Judgment is made as to whether the CPU detects the ignition purser signal within the given time ts When the ignition purser signal is not detected (NO), the process returns to STI 8 When the ignition purser signal is detected (YES), the process moves to ST20 ST20 The CPU continues generation of the CPU pulse after t = ts ST21. The CPU terminates generation of the CPU pulse ST22.. Judgment is made as to whether the CPU detects the ignition purser signal within the given time Is When the ignition purser signal is not detected (NO),ST22is executed again When the ignition purser signal is detected (YES), the process moves to ST23.

ST23 The CPU starts generation of the CPU pulse ST24 Judgment is made as to whether the battery voltage VB < the given battery voltage value v3is satisfied When VB v3is not satisfied (NO), the process moves to ST27. When VB v3is satisfied (YES), the process moves to ST25 ST25 Judgment is made as to whether the engine revolutions N 2 first given revolutions NH (the first given revolutions NH are equal to the engine revolutions n I shown in Fig 5 to Fig 9) is satisfied When N 2 NHis not satisfied (NO), the process moves to ST26 When N 2 NH is satisf ed (YES), the process moves to ST27.

ST26 Judgment is made as to whether the engine revolutions N < second given revolutions NL (such as 100 rpm) is satisfied When N < Nb is not satisfied (NO), the process returns to ST24 When N < NLis satisfied (YES), the process moves to ST27 ST27.. The CPU terminates generation of the CPU pulse Here, in the embodiment described in Fig 8, the CPU pulse is generated only for the given time Is. However, when the battery voltage VB 2 v3 is satisfied, generation of the CPU pulse may be terminated at that point irrespective of passage of the given time Is. Meanwhile, in the embodiment described in Fig 9, generation of the oscillation pulse is continued only for the given time tb and generation of the CPU pulse is continued only for the given time Is However, when the battery voltage VB 2 v3 is satisfied, it is possible not to generate the oscillation pulse and the CPU pulse Fig 12 is a flowchart showing procedures of on-duty ratio setting processing for the CPU pulse executed when starting kicking in ST05, STl 7, ST23, and the like in the flows shown in Figs. 10 and 1 I Fig 13 is a timing chart thereof. In this embodiment, the on-duty ratio of the CPU pulse is increased in the vicinity of 0 where the piston of the engine is located at a compression top dead center or in the vicinity thereof so as to increase production of electricity In ST3 1, a crank angle Oclk is detected based on detection timing of the ignition purser signal. In ST32, judgment is made as to whether or not the piston of the engine is located at the compression top dead center or in the vicinity thereof based on the detected crank angle Oclk When the crank angle Oclk satisfies a correlation Orefl < Oclk < Dref2 with given standard angles Orefl and Oref2, it is judged that the piston is located at the compression top dead center or in the vicinity thereof (corresponding to the crank angle of 0 ), and the process moves to ST33 In ST33, a relatively large ratio R I is registered as an on-duty ratio Ron for the CPU pulse As a result, large production of electricity is obtained in the vicinity of the crank angle 0 where power consumption is large On the contrary, when the correlation Orefl < ttclk < Oref2 is not satisfied, it is judged that the piston is located at a point other than the compression top dead center or in the vicinity thereof, and the process moves to ST34. In ST34, a ratio R2 smaller than the ratio Rl (Rl > R2) is registered as the on-duty ratio Ron for the CPU pulse. As a result, driving torque of the power generator is suppressed in a position other than the vicinity of the crank angle of 0" In this way, a kick-starting performance is enhanced As described above, in this embodiment, the on- duty ratio Ron for the CPU pulse is increased so as to give priority to an increase in production of electricity at the time when the piston is located at the compression top dead center or in the vicinity thereof and large electricity is required On the contrary, the on-duty ratio Ron for the CPU pulse is decreased so as to give priority to reduction in the driving torque at other time Therefore, it is possible to enhance the kick-starting performance Here, the above-described embodiment has explained that the on-duty ratio Ron for the CPU pulse was increased when the piston was located at the l 0 compression top dead center or in the vicinity thereof so as to increase the production of electricity. However, it is also possible to increase the on -duty ratio Ron for the CPU pulse similarly when the piston is located at an exhaust top dead center or in the vicinity thereof The following effects are achieved by at least the preferred embodiment of l 5 the present invention (l) According to the invention of claim l, it is possible to boost the direct current output obtained by rectifying the alternating current output from the alternator at the crank angle of 0 or in the vicinity thereof where the electric loads require large electric power and the engine revolutions drop temporarily In this way, it is possible to supply a sufficient voltage to the fuel supply system and to the ignition system and thereby to enhance the engine starting performance (2) According to the invention of claim 2, it is possible to configure the boosting means by use of the boost chopper and the pulse generating means Therefore, it is possible to boost the direct current output easily up to a desired voltage only by controlling the on-duty ratio for the switching pulse generated by the pulse generating means. ?

Claims

l An output control device for a power generator configured to rectify an alternating current output from an alternator driven by an engine and to boost a direct current output after rectif cation, the output control device comprising crank angle detection means for detecting a crank angle of the engine; and boosting means for boosting the direct current output when the engine is kick-started depending on the detected crank angle, wherein the boosting means boosts the direct current output higher at a crank to angle where a piston of the engine is located at a top dead center or in the vicinity thereof as compared to other crank angles.
2. An output control device for a power generator as claimed in claim l, wherein the boosting means includes.

l 5 a boost chopper for chopping the direct current output by use of a switching pulse; and pulse generating means for supplying the switching pulse of a duty ratio corresponding to the detected crank angle to the boosting chopper, and the pulse generating means increasing an on-duty ratio of the switching pulse higher at the crank angle where the piston of the engine is located at the top dead center or in the vicinity thereof as compared to other crank angles