JPS58113581A - Discontinuity sensing device for preheated plug - Google Patents

Abstract

PURPOSE:To have easy sensing of discontinuity in a preheat plug during the heating control of preheat plugs by such as arrangement that discontinuity is sensed off by allowing a constant current to flow under the OFF period of an opening/closing element for heating and thus sensing any sunk voltage value at a preheat plug. CONSTITUTION:A discontinuity sensing circuit 12 takes in the output voltage value et of a differential amplifier AP during the OFF period of an opening/closing element TR in accordance with take-in pulses SP from a constant current circuit CC, and gives out its differential voltage with respect to the output voltage e't under the OFF period in the previous cycle which is stored in its memory circuit. Thus a setting voltage value eb, which is a little larger than the voltage ea, is entered in the discontinuity sensing circuit 12 as the reference level for sensing of discontinuity, and the differential voltage value's (et-e't) exceeding eb shall give an judgement of discontinuity, to generate the discontinuity sensing output and display it on a discontinuity display 2. According to this arrangement, heating of preheating plugs does not require any consumption of power, and thus any disconnected preheat plug under heating control can be easily sensed off.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a disconnection detection device for a preheating plug (glow lamp) used to facilitate starting of a cold engine (particularly a teasel engine).

It is difficult to start a cold engine just by starting the starter [7], so a preheating plug is installed in the engine, and when the engine is started, the combustion chamber is heated to a predetermined temperature with the preheating plug, and then the starter is used to start the engine. I haven't been able to put it on. The preheating plug must be heated to a predetermined temperature If in a short time at the time of engine startup, and must continue to maintain that predetermined temperature until the engine has finished starting.

Resistance wire is generally used in such preheating plugs,
This resistance wire has a positive temperature coefficient of resistance in order to shorten the preheating time.

Then, in order to control the hot water temperature so that the preheating plug is heated above the preheating temperature (PPL, Z・b), the resistance value of the preheating plug is detected while supplying current to the preheating plug. It is not possible to stop the current supply to the preheating plug at the point where the resistance value of

On the other hand, if the preheating plug is disconnected, it is pointless to supply current to the Tsugiko heat thrower, so immediately stop supplying current and notify the operator of the disconnection. There is a need to. Similarly, when a kit is equipped with a plurality of preheaters, such as an engine with a plurality of cylinders, it is also necessary to control the current supply according to the number of preheating plugs that are not disconnected.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a preheating plug disconnection detection device that can easily detect a preheating plug disconnection during heating control of the preheating plug.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a configuration diagram of an embodiment of the present invention, and FIG. 2 is a waveform diagram of each part thereof. In the diagram, E is a power source, which can be considered as a vehicle battery. The TR is a switching element, and can be an electrical switch made of a semiconductor such as a power transistor, or a mechanical switch such as a relay, and can be selected as appropriate depending on the required operating speed. The opening/closing element TR is controlled by the control unit 1, which will be described later, to turn on the preheating plug aprcm source E during its on period.
current is applied, and the current supply is stopped during the off period.

GP is a preheating plug (glow plug), which is provided as many as the cylinders of the engine, and in FIG. 1, four preheating plugs are provided. The preheating plug GP has a metal resistance of 11M as a heating element.
2il-, and the resistance-temperature characteristic of the resistance wire is a positive characteristic (ie, the resistance increases as the temperature increases). CC is a constant current circuit which receives the timing pulse TP' of the control unit 1 and turns on the preheating plug G during the off period of the switching element TR.
The constant side 1 is applied to P. The APij differential amplifier outputs the total voltage value et caused by the current tIIt flowing through the preheating plug CP, and is equipped with balance resistors R1 and R2 for input.The 610Fi set temperature comparison circuit outputs the % desired value. # & foot preheating temperature (e.g. 900℃) K
The voltage (1
1kes (= i 11ij - A pixel control circuit that provides an inhibition signal ST (see Fig. 2) to the control circuit 11, which operates in response to an engine start signal from a starter switch (not shown), etc., and turns on and off the opening/closing element TH. The controlling drive signal DVt- of FIG. 2 is generated. One cycle of the drive signal DV includes a heating period a in which the switching element TR is turned on and L-c pre-cock heat is turned on, and a heating period a in which the switching element TR'fr is turned off and a preliminary heat detection is performed by a constant current i.
It consists of a detection period for detecting I degrees, and if a pulse is given during heating period 1, the switching element TR is turned on. The intermittent period is approximately 15 m1 in this embodiment, which is determined from the preheating l & temperature-elapsed time characteristics determined in advance and the allowable range of the temperature rise value/time value and the set preheating temperature. It also generates a timing pulse TP for driving the constant current circuit CC of the switching element control circuit 11ij. Tining pulse TP
The falling edge of the heating period of the drive signal DV as shown in Fig. 2 (F)
A constant current is generated from the constant current circuit CC during the detection period (off period) of the drive signal DV. 12
is a first disconnection detection circuit, which includes a storage circuit that stores the measured voltage value t, and which outputs a differential amplifier AP according to the input voltage SPK from the constant current 1φ1 path CC during the off period of the intermittent drive signal DV. The output voltage value st is taken in, and the difference voltage value between it and the voltage value e't of the OFF period one cycle before which is stored in the storage circuit is outputted, and the difference voltage value (et-e't) is set. It compares and determines whether it is larger or smaller than a predetermined value b.

This predetermined value e1. ．． Fi is a ii degree change in one intermittent cycle determined based on the predetermined preheating plug temperature-elapsed time characteristic, that is, it is set slightly larger than the voltage value ek, and If the voltage value changes more than one intermittent period due to the characteristics, that is, the difference voltage value 1 (
et-e't) 1) In the case of eb, the trap detects if there is any abnormality in the preheating plug GP.

Here, the disconnection of the preheating plug GP is a major cause of the abnormal voltage value change described above, and therefore, the disconnection of the preheating plug CP can be detected by the comparison described above. 13 The second disconnection detection circuit detects a disconnection before controlling the heating of the preheating plug, whereas the first disconnection detection circuit 12 detects the disconnection during heating control of the preheating plug. Before heating control, that is, before the opening/closing ligature control circuit 11 outputs the first drive pulse, a constant current is caused to flow from the constant current circuit CC, and the resulting voltage value et is captured at the timing of the capture pulse, and is set in advance. compared with the set voltage value e. This set voltage value・c
If you set the two voltage values equal to the product of the resistance value r of the preheating plug when not preheating Fi and the constant current amount, the set voltage value ・
. For example, if four preheating plugs GP each having a resistance value r are connected in parallel as shown in Figure 1, all four preheating plugs If all wires are disconnected, the resistance value is r.
/4, if one wire is broken, r/3. If two wires are broken, it is r/2. If three wires are broken, the resistance value will be r; on the other hand, if all the wires are broken, the resistance value will be ■, and the voltage value (1・r/4) when there is no wire breakage will be the voltage value when there is a wire breakage ( 1・r
/' + i・r/2. ir, 0), paper breakage is detected based on this difference. The 14ij71II thermal control operation latch circuit latches the first pulse (on period signal) of the drive signal DV of the switching element control circuit 11, holds that heating control has been performed, and uses the holding output to activate the second disconnection detection circuit. The 13th action is the turtle that is prohibited. 15
is a latch release circuit that receives a signal from a water temperature sensor (not shown) that detects water ii' in the second radiator, and when the cooling water temperature falls outside the preheating plug heating control operation conditions (i.e., after the start of the engine), the heating control is activated. When it is detected that the condition is within the condition (that is, when the engine is stopped), the latch circuit 14 is released in a near-blind state, and the second disconnection detection circuit 15 is caused to detect a disconnection again. This is a 2Fi disconnection indicator, which is composed of a display device such as a lamp or a light emitting diode, and visually displays the disconnection detection output of the first and second disconnection detection circuits 12.13, and notifies the operator of the disconnection. It is.

Now, the operation of the circuit shown in Figure @1 will be explained next.

A starting signal from a starter switch (not shown) is input to the switching element control circuit 11 to generate a drive signal 1) V to drive the switching element TR on/off (intermittent drive). on the other hand,
Since the switching element control circuit 11 supplies the timing pulse TP generated at the falling edge of the drive signal DV to the constant current circuit CC, a current is output from the constant current circuit CC during the off period of the switching element TH. Therefore, in one period of intermittent operation, the ON period Ktf of 1Ipl closed element TR, the power supply E
The current preheats through the switching element TR! GPK is supplied, the off period KFi of the switching element TH, and the current of the constant current circuit CC is supplied to the preheating circuit 4&GP. The preheater 4&GP generates heat due to the current from the power source E, raising the temperature and increasing the resistance value of the preheating plug GP. Switching element TH
During the off-period, preheating is performed by the constant current supplied from the constant current circuit CC! The voltage value t due to the voltage drop of GP is output from the differential amplifier AP. Changes in voltage value and t are proportional to changes in resistance value.

Therefore, the voltage value t is considered to indicate a temperature change. This voltage value/tFi is input to the set temperature comparison circuit 10 and compared with the set voltage value C1. By this comparison, when e@〉et, that is, preheating &GP reaches the set preheating temperature and it is detected as tenah, the switching element TR is activated in one cycle of the primary.
The switching element control circuit 11 is controlled so as to output a pulse that turns on. Conversely, the preheating plug GP is set to the preheating fItA.
When f is reached, the comparison result becomes et≧e, so the prohibition signal STv! that prohibits the output of the pulse that turns on the switching element TRτ in one cycle of the first order is STv! Pl closed element control same element control circuit. As shown in Figure 2, the voltage value et#'i during the off period increases due to the heating of the preheating plug GP due to the application of the drive signal DV, and it is detected during the off period that it reaches the set voltage value e. As a result, the pulse output is prohibited as shown by the dotted line of the drive signal DV in Fig. 2, so the switching element TR is not turned on and no current is applied to the preheating plug GPK for heating. . In the off period of the next cycle, when it is detected that the temperature of the preheating plug GP is lower than the temperature of the crotch preheating source (i.e., the comparison result is taken and et is detected), a prohibition signal ST is output. -C The opening/closing switch control circuit 11 emits a pulse indicating the on period in the next power period.In this way, the preheating plug GP is heated at the scheduled preheating temperature from the time the start signal arrives, and Moreover, the planned preheating temperature KiM
Then, the temperature is maintained at this temperature. With this configuration, 1
J.

Round, conventional power supply using constant current for temperature detection.
Compared to those that use a current of
However, there is no resistance for detecting electric voltage.

The current of the power source E is not consumed for temperature detection, and it is effective when the engine has only a limited power source.

In the present invention, a disconnection detection device is further provided. That is, during the off period of the wIrII detection circuit 12ii switching element TR, the output voltage value t of the differential amplifier P is taken in response to the input signal SPK from the constant current circuit CC. Then, the disconnection detection circuit 12 outputs the difference voltage from the output voltage value e't of the OFF period one cycle before, which is stored in an internal storage circuit. The period of the off period is fixed, so if you
If there is no disconnection, the differential voltage value 1(・s −e'*)
I is the voltage series of one intermittent cycle in the predetermined voltage value-elapsed time characteristic determined based on the predetermined preheating time-elapsed time characteristic.

Therefore, the disconnection detection circuit 12 is set to a set voltage value slightly larger than the voltage value . It makes a judgment and outputs a disconnection detection output, and the differential voltage value 1 (at-・'
t) If 1 is less than eb, it is determined that there is no disconnection. For example, if n preheating plugs, each with a resistance value of r, are installed in parallel, all of them will break, resulting in a flash with a total resistance of I/i.
Therefore, the differential voltage value 1 (et-e't) l
If it is greater than tjeb and there are reverse Kk disconnections, the S total resistance value will be r/(n-k), and the voltage value etFi1・r/
(n-k), it is larger than the expected voltage value 1・r/n without any disconnection, and the difference voltage value 1(・ is -・'
4) It becomes larger than Itj@b, making it possible to detect disconnection. The disconnection detection circuit 12ij compares the output of such a voltage difference with the mausoleum voltage value during each off period, and detects the preheat & GP disconnection at an early stage during heating control. Then, the voltage value of the previous OFF period stored in the memory circuit 't is changed to the voltage value at of the current OFF period by an update pulse R8 generated from the switching element control circuit 11 after outputting the differential voltage.
The K*new value is stored and used to obtain the difference from the voltage value of the next OFF period. The disconnection detection output obtained in this way is sent to the disconnection indicator 2, and a display indicating fresh green is performed.

Regarding such disconnection detection during heating control, in order to detect disconnection before heating control, when the start signal first arrives at the switching element control circuit 11, the % timing pulse TPt is activated before issuing the drive signal -1jDV. Send it to the constant current circuit CC and preheat the constant current from the constant current circuit CC before heating control! G.P.K.
Then, the voltage value t due to the voltage drop of the preheating plug GP is outputted from the differential amplifier AP.

Then, the second disconnection detection circuit 16 incorporates this voltage value ** at the timing of the weaving pulse BP and compares it with the next set internally set voltage value *. Setting voltage value・Fi pre-11
Preheating when 1kGF is not disconnected and does not preheat*
Since it is determined by the apo*resistance value and the constant current value iK, if an output voltage value t that is significantly different from these values is input, a wire breakage detection output will be generated. If this ninth K detects that the voltage value t is larger than the set voltage value , it is possible to detect a disconnection in one of the plurality of preheating 41GPs.

K, which also detects that the total preheating 41GP is disconnected, has a differential voltage value of 1 (@
What is necessary is to take L-ec)I and compare it with the allowable voltage value ed. In this second disconnection detection circuit 13, when the drive signal DV is generated from the switching element control circuit 11, the latch circuit 14 is held and the detection operation is prohibited due to (9). On the other hand, when the cooling water temperature goes outside the operating conditions for the preheat orange heating control and returns to the operating conditions for the heating control, that is, when the engine becomes cold, the latch release circuit 15 releases the latch state a of the latch circuit 14. No output is generated, and the inhibition of the detection operation of the disconnection detection circuit 13 of W, 2 is released.

In the above description, an example has been described in which the control section 1 is divided into individual configurations from the comparator circuit 10 to the latch release circuit 15, but if the control section 1 is configured with a microcomputer, a common hardware: C configuration can be achieved. For this purpose, the voltage value t is converted into a digital value 1/CX and inputted to the control unit 1, and the set voltage value ea+ek+ec, e (1 is stored as a digital value in the main memory of the microcomputer, and The arithmetic circuit calculates the differential voltage value, compares it with a set voltage value, and controls the generation of a drive signal in accordance with the required control program stored in the control program memory.

As described above, according to the present invention, a constant current is passed during the OFF period of the switching element for heating, and the voltage value of the voltage drop of the preheating plug is detected, and the disconnection 41 is detected. Disconnection can be detected without consuming electricity for heating, and since it uses a constant current, it has the advantage of improving accuracy. Moreover, since the constant current circuit for temperature detection used to control the temperature of the preheating plug is shared, disconnection can be detected by simply capturing the voltage value, which does not complicate the configuration and allows for an inexpensive configuration. . Furthermore, disconnection detection is performed by determining the difference between the voltage value during the off-period of the previous cycle and the voltage value during the current off-period, and comparing the difference with a predetermined reference value. Since it can detect wire breakage, it is extremely effective in practical use, as it enables early detection of wire breakage.

Although the present invention has been described with reference to one embodiment, the present invention is not limited to the above-described embodiment, and various modifications can be made in accordance with the spirit of the present invention. It is not excluded from the scope.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a waveform diagram of each part of the embodiment of FIG. E...power supply, TR...switching element, GP...preheating plug, CC...constant current circuit, AP...differential amplifier, 1.
...Control unit, 2...Disconnection indicator, 12.15...Disconnection detection circuit.

Claims (3)

[Claims] (1) A switching element is inserted into the electric circuit of the preheating plug, and the control unit intermittently controls the switching element to control the heating of the preheating plug, and a constant current circuit is connected to the preheating plug to turn off the switch. Preheating in which a constant current is passed through the preheating plug from the constant current circuit during a period, a voltage value due to a voltage drop of the preheating plug is measured, and a control unit detects the temperature f of the preheating plug and controls the opening/closing element. In the stopper heating control device, the core control section includes a storage section that stores the voltage value, and the crest control section stores the voltage value of the off-period of the previous cycle and the voltage value measured during the current off-period of the storage section. A disconnection detection device for a preheating plug, characterized in that it calculates the difference between the two and outputs a disconnection output when the difference is larger than a predetermined value. (2) A disconnection detection device for a preheating plug according to claim (1), wherein the voltage value of the pre-distribution section is updated to the voltage value measured during the current off period. (3) The disconnection detection device for a preheating plug as set forth in claim (1) or (2), characterized in that a disconnection # display section is provided to display the disconnection output of the restriction section.