CA1202692A - Heating current control for glow plug of internal combustion engine - Google Patents
Heating current control for glow plug of internal combustion engineInfo
- Publication number
- CA1202692A CA1202692A CA000413230A CA413230A CA1202692A CA 1202692 A CA1202692 A CA 1202692A CA 000413230 A CA000413230 A CA 000413230A CA 413230 A CA413230 A CA 413230A CA 1202692 A CA1202692 A CA 1202692A
- Authority
- CA
- Canada
- Prior art keywords
- glow plug
- output
- pulses
- current
- switch
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Abstract
ABSTRACT OF THE DISCLOSURE
In an ignition system having a glow plug, the filament thereof is supplied with power from a generator by means of a switch. The power is controlled so that a constant glow temperature level is obtained, for example by means of predetermined resistance in the filament. The arrangement is associated with a Wheatsone bridge which, during a short interval at the beginning of every heat current cycle, is switched on when generator power is not yet supplied to the glow plug. The balance of the Wheatstone bridge, which indicates whether the glow plug is too hot or too cold, is registered for the present cycle by means of a comparator in which the balance is converted into a logical signal to be the basis of on/off regulation by the switch in the heating circuit of the glow plug.
In an ignition system having a glow plug, the filament thereof is supplied with power from a generator by means of a switch. The power is controlled so that a constant glow temperature level is obtained, for example by means of predetermined resistance in the filament. The arrangement is associated with a Wheatsone bridge which, during a short interval at the beginning of every heat current cycle, is switched on when generator power is not yet supplied to the glow plug. The balance of the Wheatstone bridge, which indicates whether the glow plug is too hot or too cold, is registered for the present cycle by means of a comparator in which the balance is converted into a logical signal to be the basis of on/off regulation by the switch in the heating circuit of the glow plug.
Description
This invention relates to an ignition system using glow plugs, for use in an internal combustion engine.
A glow plug in an internal combuskion engine is dependent on a current source for keeping the glow filament of the plug glowing. The power to the filament is rather low, e.g. 4 W, but the temperature of the plug must be carefully controlled in order to make th'e engine run evenly. In known embodiments of glow plug ignition a battery is used as a current source which i.a. also requires the use of a charging device~ In small engines which are started by means of a rope starter, the battery is a heavy and inconvenient accessory which should be avoided if possible. It has therefore been found desirable to provide an alternative current source for the glow plug and also to employ a control system for the current to maintain proper temperature in the plug.
According to the present invention there is provided i~ an internal combustion engine ignition system having a glow plug and means applying a heating current to said glow plug, said glow plug being connected in one branch of a Wheatstone bridge, the means applying the heating current comprising switch means, said system further comprising sensing means including comparator means connected to the bridge and having a first output level responsive to a predetermined resistance of said glow plug corresponding to a cold condition of the glow plug, a source of test pulses con~ected to said bridge, and means responsive to the simultaneous occurrence of said first output and one of said test pulses for controlling said switch means to apply current to said glow plugO
An embodiment of an ignition system according to the invention is described in the following with reference to the attached drawing, in which:
FIGURE 1 is a simplified wiring diagram of the ignition system, and FIGURE 2 is a graph of different voltages in the system of Fig. 1.
æ
The current source is comprised of a generator 10 driven by the engine (not shown) on which the ignltion system is used. A glow plug 11 is supplied with alternating current from the generator via an electronic switch 12 which controls the current so that the glow plug receives a prede~ermined heating current. Temperature measurement on the plug is effected by a measuring procedure employing a Wheatstone bridge 13, in which the resistance of the glow plug comprises one branch. The other branches are comprised of two fixed resis~ors 14, 15 and a variable resis~or 16, respectively.
By means of this variable it is possible to adjust the balance of the bridge, and thus also the temperature of the plug3 as will be hereinafter described in detail.
Test pulses are applied to one of the diagonals of the bridge from a transistor amplifier 17 thereby resulting in the production of voltage pulses in the other diagonal for application to a comparator 18 connected thereto. The comparator lB i.s of the type having the same working mode as a differential relay which closes one contact at a higher voltage on a first input 19 but another contact at a higher voltage on a second lnput 20. The comparator in the present case, however, is electronic, e.g. the well-known standard module LM 339. A signal in the form of a logical "1" or "0"
appears at the output of the compara~or, depending on which of the inputs has the highest potential.
The signal is stored in a bistable flip-flop 22, e.g. the well-known standard module type 4013~ during a time equal to at l~ast one cycle of the generator voltage. The stored signal remains at the output 23 of the flip-flop for ~his time and is appl iecl ~o an AND-g~t~ 24 which Ls e . g . an LM 3 3 9 modul e .
~2~:~6~
The generation of the ~est pulses occurs in a mono-stable flip-flop 25, e.g. ~ standard module type 4098, which applies a pulse on a wire 26 to the transistor ampll~ier 17 at the beglnning of every positive half cycle of th2 generator voltage. Thus, the measurement occurs at an instant when generator curren~ to the glow plug i5 not supplied, This is a necessary condltion since only the test pulse must pass through the bridge during testing. The genera~or current is con~rolled by the switch 12 whlch, in the illustrated embodiment, is comprised of two anti-parallel thyristors 27, 28 connected to rece$ve trigger pulses from a monost~ble flip-flop lmodule 4098) 29 vla thc AND - gste 24. The~e trlgger pulses are controlled by conventional means to be somewhat delayed with respect to the pulses on the wire 26, and ss a result the thyristors can start to conduct only after the test pulse has passed the brldge. The test pulse is blocked by the AND gate from triggering the thyristors, however, if the pulse from the flip-flop 22 ls missing owing to the balance of the bridge i.e. if the temperature oE the glow plug is above a certain minimum. The trigger pulses from flip-flop 29 passes through the AND - gate 24 only lf the flip-flop 22 has been set during the test period in response to sensing in the bridge that the glow plug is too cold.
The thyristors ~hen st~rt to conduct, one during a positlve half cycle and the oth~ during a negative half cycle, snd the glow plug is supplied w~th power from the gener~tor during a whole cycle~ The question whether the glow plug should be supplied wlth power also during the next cycle is deter-mined by the test in the bridge which thus starts that cycle.
The control circuit of the invention endeavors to keep the ~,~
glow plug tempera~ure constant independently of the speed of the generator and the ambient temperature. The glow temperature level can be varied by adjusting ~he variable resistor 16 in the bridge.
FI~. 2 illustrates some voltages used in the described diagram. The only current source used for the power supply of the components is the generator, the illustrated voltage of which is a sine wave (top curve of FIG. 2). A
voltage converter 30 such as module LM 339 is connected to Zener diodes (not shown) in conventional manner to generate a square wave voltage 31 with a phase delay (hysteresis) from the sine waveO This square wave voltage is applied to the flip-flops 29 and 25, which in turn generate control pulses 32 for the bridge test and trigger pulses 33 respectively.
The flip~flop 29 is triggered by the negative going output of the converter 30 as well as by the flip-flop 25 (by a conventional interconnection, not shown) and hence the number of pulses 33 is double the pulses 32. In order to generate potentials and oper~ting voltages for the different components of the circuits the system is provided wi~h a rectifier circuit 34 connected to rectify the generator voltage to provide a direct operating voltage.
The engine employed in the invention is preferably a small motor of the type provided in power tools like motor saws, lawn mowers, etc. adapted to be started by manual force. The generator is driven by the engine during the start procedure and supplies the glow plug with electric power so that the glow filament reaches the glow temperature This is possible due to the fact that the glow filament has a low heating-up period (the effect is some 4W) and ~20~
the generator delivers full power at low rotation rates (about 1000 r.p.m.) When the engine in operation runs at a high r.p~m. the generator also runs at a high r.p.m. and delivers a high voltage tha~ may be too high for the glow plug. The voltage to the circuit of theinven~ion can be limited by means of shunt, e.g. 2ener diodes (not shown) or a non-linear resistor (thermistor) (not shown) connected in parallel with the generator.
The described embodiment is an example of how ~he invention can be realized. Alternatively, a DG-generator can also be used as a current source for the glow plug and the components.
A glow plug in an internal combuskion engine is dependent on a current source for keeping the glow filament of the plug glowing. The power to the filament is rather low, e.g. 4 W, but the temperature of the plug must be carefully controlled in order to make th'e engine run evenly. In known embodiments of glow plug ignition a battery is used as a current source which i.a. also requires the use of a charging device~ In small engines which are started by means of a rope starter, the battery is a heavy and inconvenient accessory which should be avoided if possible. It has therefore been found desirable to provide an alternative current source for the glow plug and also to employ a control system for the current to maintain proper temperature in the plug.
According to the present invention there is provided i~ an internal combustion engine ignition system having a glow plug and means applying a heating current to said glow plug, said glow plug being connected in one branch of a Wheatstone bridge, the means applying the heating current comprising switch means, said system further comprising sensing means including comparator means connected to the bridge and having a first output level responsive to a predetermined resistance of said glow plug corresponding to a cold condition of the glow plug, a source of test pulses con~ected to said bridge, and means responsive to the simultaneous occurrence of said first output and one of said test pulses for controlling said switch means to apply current to said glow plugO
An embodiment of an ignition system according to the invention is described in the following with reference to the attached drawing, in which:
FIGURE 1 is a simplified wiring diagram of the ignition system, and FIGURE 2 is a graph of different voltages in the system of Fig. 1.
æ
The current source is comprised of a generator 10 driven by the engine (not shown) on which the ignltion system is used. A glow plug 11 is supplied with alternating current from the generator via an electronic switch 12 which controls the current so that the glow plug receives a prede~ermined heating current. Temperature measurement on the plug is effected by a measuring procedure employing a Wheatstone bridge 13, in which the resistance of the glow plug comprises one branch. The other branches are comprised of two fixed resis~ors 14, 15 and a variable resis~or 16, respectively.
By means of this variable it is possible to adjust the balance of the bridge, and thus also the temperature of the plug3 as will be hereinafter described in detail.
Test pulses are applied to one of the diagonals of the bridge from a transistor amplifier 17 thereby resulting in the production of voltage pulses in the other diagonal for application to a comparator 18 connected thereto. The comparator lB i.s of the type having the same working mode as a differential relay which closes one contact at a higher voltage on a first input 19 but another contact at a higher voltage on a second lnput 20. The comparator in the present case, however, is electronic, e.g. the well-known standard module LM 339. A signal in the form of a logical "1" or "0"
appears at the output of the compara~or, depending on which of the inputs has the highest potential.
The signal is stored in a bistable flip-flop 22, e.g. the well-known standard module type 4013~ during a time equal to at l~ast one cycle of the generator voltage. The stored signal remains at the output 23 of the flip-flop for ~his time and is appl iecl ~o an AND-g~t~ 24 which Ls e . g . an LM 3 3 9 modul e .
~2~:~6~
The generation of the ~est pulses occurs in a mono-stable flip-flop 25, e.g. ~ standard module type 4098, which applies a pulse on a wire 26 to the transistor ampll~ier 17 at the beglnning of every positive half cycle of th2 generator voltage. Thus, the measurement occurs at an instant when generator curren~ to the glow plug i5 not supplied, This is a necessary condltion since only the test pulse must pass through the bridge during testing. The genera~or current is con~rolled by the switch 12 whlch, in the illustrated embodiment, is comprised of two anti-parallel thyristors 27, 28 connected to rece$ve trigger pulses from a monost~ble flip-flop lmodule 4098) 29 vla thc AND - gste 24. The~e trlgger pulses are controlled by conventional means to be somewhat delayed with respect to the pulses on the wire 26, and ss a result the thyristors can start to conduct only after the test pulse has passed the brldge. The test pulse is blocked by the AND gate from triggering the thyristors, however, if the pulse from the flip-flop 22 ls missing owing to the balance of the bridge i.e. if the temperature oE the glow plug is above a certain minimum. The trigger pulses from flip-flop 29 passes through the AND - gate 24 only lf the flip-flop 22 has been set during the test period in response to sensing in the bridge that the glow plug is too cold.
The thyristors ~hen st~rt to conduct, one during a positlve half cycle and the oth~ during a negative half cycle, snd the glow plug is supplied w~th power from the gener~tor during a whole cycle~ The question whether the glow plug should be supplied wlth power also during the next cycle is deter-mined by the test in the bridge which thus starts that cycle.
The control circuit of the invention endeavors to keep the ~,~
glow plug tempera~ure constant independently of the speed of the generator and the ambient temperature. The glow temperature level can be varied by adjusting ~he variable resistor 16 in the bridge.
FI~. 2 illustrates some voltages used in the described diagram. The only current source used for the power supply of the components is the generator, the illustrated voltage of which is a sine wave (top curve of FIG. 2). A
voltage converter 30 such as module LM 339 is connected to Zener diodes (not shown) in conventional manner to generate a square wave voltage 31 with a phase delay (hysteresis) from the sine waveO This square wave voltage is applied to the flip-flops 29 and 25, which in turn generate control pulses 32 for the bridge test and trigger pulses 33 respectively.
The flip~flop 29 is triggered by the negative going output of the converter 30 as well as by the flip-flop 25 (by a conventional interconnection, not shown) and hence the number of pulses 33 is double the pulses 32. In order to generate potentials and oper~ting voltages for the different components of the circuits the system is provided wi~h a rectifier circuit 34 connected to rectify the generator voltage to provide a direct operating voltage.
The engine employed in the invention is preferably a small motor of the type provided in power tools like motor saws, lawn mowers, etc. adapted to be started by manual force. The generator is driven by the engine during the start procedure and supplies the glow plug with electric power so that the glow filament reaches the glow temperature This is possible due to the fact that the glow filament has a low heating-up period (the effect is some 4W) and ~20~
the generator delivers full power at low rotation rates (about 1000 r.p.m.) When the engine in operation runs at a high r.p~m. the generator also runs at a high r.p.m. and delivers a high voltage tha~ may be too high for the glow plug. The voltage to the circuit of theinven~ion can be limited by means of shunt, e.g. 2ener diodes (not shown) or a non-linear resistor (thermistor) (not shown) connected in parallel with the generator.
The described embodiment is an example of how ~he invention can be realized. Alternatively, a DG-generator can also be used as a current source for the glow plug and the components.
Claims (7)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In an internal combustion engine ignition system having a glow plug and means applying a heating current to said glow plug, said glow plug being connected in one branch of a Wheatstone bridge, the means applying the heating current comprising switch means, said system further comprising sensing means including comparator means connected to the bridge and having a first output level responsive to a predetermined resistance of said glow plug corresponding to a cold condition of the glow plug, a source of test pulses connected to said bridge, and means responsive to the simultaneous occurrence of said first output and one of said test pulses for controlling said switch means to apply current to said glow plug.
2. The system of claim 1, wherein said means responsive to the simultaneous occurrence of said first output and one of said test pulses comprises a flip-flop circuit, whereby the output of said flip-flop is set to a given level only upon the simultaneous occurrence of said first output and test pulse.
3. The system of claim 1, further comprising a source of trigger pulses, said means responsive to the simultaneous occurrence of said first output and test pulse further comprising gate means responsive to said given level output of said flip-flop and one of said trigger pulses for controlling said switch means to apply current to said glow plug.
4. The system of claim 3, wherein said switch means comprises an electronic switch.
5. The system of claim 4, wherein said electronic switch comprises thyristor means.
6. The system of claim 5, wherein said means applying a heating current to said glow plug further comprises a generator driven by said internal combustion engine.
7. The system of claim 6, wherein said generator produces an alternating current, and said source of test pulses and source of trigger pulses comprise monostable multivibrator means connected to be triggered by said alternating voltage, whereby current is applied to said glow plug for the remainder of any cycle during which said given level occurs at the time of occurrence of a trigger pulse.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000413230A CA1202692A (en) | 1982-10-12 | 1982-10-12 | Heating current control for glow plug of internal combustion engine |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000413230A CA1202692A (en) | 1982-10-12 | 1982-10-12 | Heating current control for glow plug of internal combustion engine |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1202692A true CA1202692A (en) | 1986-04-01 |
Family
ID=4123751
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000413230A Expired CA1202692A (en) | 1982-10-12 | 1982-10-12 | Heating current control for glow plug of internal combustion engine |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1202692A (en) |
-
1982
- 1982-10-12 CA CA000413230A patent/CA1202692A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |