JPS58113580A - Control device for heating of preheated plug - Google Patents

Abstract

PURPOSE:To have a stable control of heating for residual preheat plugs up to an intended preheat temperature even though any one of the preheat plugs comes in disconnection, by sensing the discontinuity and changing the reference voltage value for the heating control according to the number of remaining plugs in good condition. CONSTITUTION:A discontinuity sensing circuit 12 takes in the output voltage value et of a differential amplifier 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 value e't under the OFF period in the previous cycle which is stored in its memory circuit. As the reference level for sensing of discontinuity a preset voltage value et is entered in the discontinuity sensing circuit 12, and the differential voltage value's (et-e't) exceeding eb shall give a judgement of discontinuity to lead to generation of the discontinuity sensing output. Accordingly, a number-of-discontinuities sensing circuit 16 gives out a setting temp. voltage value e's in accordance with the number of disconnected plugs, which is put in memory as a setting temp. voltage value for a setting temp. comparator circuit 10 to be then fed in the heating control of the preheat plug GP. Thus the remaining preheat plugs can be put underheating control stably up to the intended preheat temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heating side @ device after preheating (group lag) used to facilitate the starting of an engine (particularly a diesel engine) in a cold S. The present invention relates to a preheating plug heating control device that appropriately controls heating of other preheating plugs even if one of the preheating plugs is cut off after preheating.

Since it is difficult to start a cold engine engine just by starting the starter, a preheater is installed in the engine, and when the engine is started, the combustion chamber is heated to a predetermined temperature with a preheating plug, and then the starter is used to start the engine. ing. The preheating plug is
The engine must be heated to a predetermined temperature in a very short period of time when the engine is started, and the predetermined temperature must be maintained until the engine has finished starting.

Resistance wire is generally used in such preheating plugs,
This resistance wire has a rounded positive temperature coefficient of resistance that reduces preheating time.

In order to control the temperature so that the temperature does not exceed the preheating temperature after preheating, the resistance value of preheater #II& is detected after the current is applied after preheating, and the preheating is performed when the resistance value matches the resistance value of the preheating plug at the preheating temperature. The practice is to cut off the electrical current supply to the stopper.

On the other hand, if multiple preheating plugs are installed in parallel,
If the preheating plug is disconnected, the parallel resistance values of the plurality of preheating plugs will be distorted, the temperature control described above will not be performed smoothly, and the temperature of the preheating plug will exceed the expected temperature, which may cause an unfavorable situation.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a preheating plug heating control device that can control the heating of the remaining preheating plugs to a predetermined temperature even if any one of a plurality of preheating plugs is disconnected.

The present invention will be described in detail below with reference to the drawings.

FIG. 111 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 and can be considered to be a vehicle battery. The TR is a switching element, and can be an electrical switch made of a semiconductor such as a p1 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 supply electricity to the preheating plug GP 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 number of cylinders in the engine, and in FIG. 1, four preheating plugs are provided. The preheating 41GP has a metal resistance wire as a heating element, and the resistance temperature characteristic of the resistance wire has a positive characteristic (II, a characteristic in which the resistance increases as the temperature increases). CC is a constant current circuit, and the timing pulse T of the control section 1
P, and a constant current is applied to the preheating circuit 4 & GP during the off period of the closed element T. AP is a differential amplifier that outputs the voltage drop caused by current flowing through the preheating plug OP as a voltage value el, and the input balance resistor R1
, R2. Reference numeral 10 denotes a set temperature comparison circuit, which compares the preheating plug GP at a desired set preheating temperature (for example, 900°C).
The set temperature and voltage value es (='
xrs) is set or stored, and the voltage value e during the off period is output from the differential amplifier AP.

and the set temperature voltage value e, and if et≧C, a prohibition signal ST is sent to the ## closed element l1l111 circuit 11, which will be described later.
(See Figure 2). Reference numeral 11 denotes an m-circuit on the switching element side, which is operated by an engine starting signal from a start switch (not shown) or the like, and generates a drive signal DV shown in FIG. 2 for controlling ON/OFF of the switching element TR. The first period of the drive signal DV includes a heating period a in which the switching element TR is turned on to heat the pre-heating rod, and a detection period in which the switching element TR is turned off and the temperature of the rod is detected by a constant current. Therefore, if t4 pulse is applied during the heating period a, the switching element TR is turned on.

The intermittent cycle is determined from the preheating plug temperature-elapsed time characteristic obtained in advance, the temperature rise value/time value, and the allowable range of the set preheating temperature. In this embodiment, it is approximately 15 m5, and the switching element control circuit 11 generates a timing pulse TP for driving the constant current circuit CC. timing pulse T
P is generated at the falling edge of the heating period of the drive signal DV as shown in Fig. 2, and is generated during the detection period (off period) of the drive signal DV.
A constant current is output from the constant current circuit CC. 12 is a first disconnection detection circuit, which detects the measured voltage value el.

The output voltage value e() of the differential amplifier AP is captured in response to the capture pulse SP from the constant current circuit CC during the OFF period of the intermittent drive signal DV, and is stored in the memory circuit and stored in the memory circuit. The difference voltage value from the voltage value e/l during the off period is calculated and output, and the difference voltage value (et''-e't) is set and it is compared and determined whether it is larger or smaller than the nine predetermined values eb. This predetermined value eb is determined in advance based on the concentration-elapsed time characteristic of the preheating #9, and is determined to be a little larger than the temperature change of 91 intermittent cycles, that is, the voltage value e, and the preheating value described above is If the voltage value becomes 1 due to the voltage value change of one intermittent cycle or more due to the determined preheating plug temperature-course characteristic, that is, if the differential voltage value 1 (et-e't) I>eb, then the preheating plug GP K This detects when there is some kind of abnormality.Here, the above-mentioned abnormal voltage value change is largely caused by the disconnection of the preheating plug UP, and therefore, the above comparison indicates that the disconnection of the preheating plug GP is the cause. It is something that can be detected.

15 is a second disconnection detection circuit, which is connected to the first disconnection detection circuit 12.
During the heating control of the preheating plug, 1ITII! 1, this method detects a disconnection before the heating control a of the preheating plug is detected, and the constant current A constant current is passed through the circuit CC, and the resulting voltage 11e is captured at the timing of the capture pulse 8P, and a predetermined 9-set voltage value C is obtained.
, compared with. If this set voltage value ec is set to a voltage value that is close to the product of the resistance value ri of the preheating plug when not preheating and the constant current rise, the set voltage value ec and the voltage value et which greatly increases can be detected by comparison. Then, a disconnection output is generated. For example, as shown in the figure, if four preheating @GPs each with a resistance value r are connected in parallel, all four preheating plugs are connected to II
If there is no I wire, the resistance value is r/4, if one wire is broken, it is r15, if two wires are broken, it is r/2, if three wires are broken, it is r, and vice versa. If the wire is broken, the resistance value will be -, and the voltage value when there is no wire breakage (i・r/4)
The voltage value when the wire is disconnected (1・r15, i sr/2
, i or, 0) and the current state, and the disconnection is detected based on this difference. 14 is a heating control operation latch circuit;
The first pulse of the drive signal DV of the switching element control circuit 11 (
The on-period signal) is latched to hold the heating control, and the held output inhibits the operation of the second wire breakage detection circuit 13. Reference numeral 15 denotes a latch release circuit which receives a signal from a water temperature sensor (not shown) that detects the water temperature of the radiator, and when the cooling water temperature is within the preheating plug heating control operating condition (i.e., after the start of the engine) K, it is again within the heating control operating condition ( I
t, when the engine is stopped), the latch -aS of the latch circuit 14 is released, and the second disconnection detection circuit 15 detects the disconnection again. 2
is an lltll display, which is composed of a display device in the form of a lamp and a light emitting diode, and includes first and second disconnection detection circuits 12.
The disconnection detection outputs GPDC1 and GPDC2 of No. 13 are visually displayed and the operator is informed of: Ij1. 16 is a disconnection number detection circuit, which detects the difference voltage value + (et-e't)'l calculated by the disconnection detection circuit 12 and the disconnection detection output GPDC.
1, set the differential voltage value 1 (et −e't) I in advance, and obtain the 9 comparison voltage value v1 t vl'...
The number of broken wires of the preheating throw is detected, and the set voltage value eZ of the set temperature comparison circuit 10 is outputted according to the number of broken wires, and the set voltage value eZ of the comparison circuit 10 is set.

This will cause the changes to occur.

Now, the operation of the circuit shown in FIG. 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 DV, which drives the switching element TR on/off (intermittent drive). On the other hand, 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. Current is output. Therefore, in one period of intermittent operation, during the ON period of the switching element T, the current of the voltage #E is supplied to the preheating plug GP via the switching element TR, and the current of the voltage #E is supplied to the preheating plug GP through the switching element
During the off period of R, the current of constant current circuit CC preheats @GP
will be supplied to The preheater @qP is heated by the current from the power source E, raising the temperature and the preheating plug G.
The resistance value of P also increases. During the off period of the switching element TR,
The preheating plug GP is heated by the constant current supplied from the constant current circuit CC.
A voltage value el due to the voltage drop is output from the differential amplifier AP. Changes in the voltage value C1 are proportional to changes in the resistance value, and therefore the voltage value eg is considered to indicate a temperature change. This voltage value et is input to the set temperature comparison circuit 10 and compared with the set voltage value e. By this comparison, e
,>et1, that is, when it is detected that the preheating plug GP has not reached the set preheating temperature, the -closing element control circuit 11 is controlled so as to output a pulse that turns on the switching element T)t in the next cycle. Conversely, when the preheating plug ck1' reaches the set preheating temperature, the comparison result becomes et≧e, so in the next IJili period, the prohibition signal ST that prohibits the output of the pulse that turns on the switching element TR is activated. It is output to the control circuit 11. As shown in Fig. 2, the voltage value et during the off period is the drive signal l)■
As the preheating plug GP is heated by the application of Pulse output is prohibited during this period, so the switching element T is not turned on, and no current is applied to the preheating plug GPK for heating. When it is detected that the temperature of the preheating plug GP becomes lower than the set preheating temperature during the off period of the next cycle (as a comparison result, et < e.

is detected), the prohibition signal ST is not output.
The switching element control circuit 11 generates a pulse indicating an on period in the next cycle. In this manner, the preheating plug GP is heated at the preheating temperature range from the time the start signal arrives, and when the preheating temperature reaches the preheating temperature, the preheating plug GP is maintained at this temperature. In this configuration, since a constant current is used for temperature detection, temperature can be detected more accurately than in conventional systems that use current from the power source E. Moreover, since no voltage detection resistor is provided, the In the present invention, which is effective especially when the engine cape has only a limited power source without consuming current for temperature detection, a K11lii detection circuit 12 and a disconnection number detection circuit 16 are further provided. That is, the disconnection detection circuit 12
takes in the output voltage value e of the differential amplifier AP in response to the take-in pulse 8PK from the constant current circuit CC during the off period of the switching element TR. Then, the disconnection detection circuit 12 stores the output voltage value e/in the OFF period before '#-1 cycle in the internal storage circuit.
, outputs the difference voltage between.

Since the cycle of the off period is fixed, if the preheating valve G
If P is not disconnected, the differential voltage value is 1 (et-e't
>t is less than or equal to the voltage difference e1 of one intermittent cycle in the voltage value-elapsed time characteristic determined based on the pre-determined preheating plug temperature-elapsed time characteristic.

Therefore, the set voltage value e, which is slightly larger than the voltage value e1, is set as the disconnection detection reference level in the disconnection detection circuit 12.

is set, and the difference voltage value 1 (et −e't )
If I is more than cb, IFI411! It is determined that the disconnection detection output is issued, and the differential voltage value 1 (at - e't) I becomes eb.
'If it is below, it is determined that there is no disconnection. For example, if n preheating plugs, each with a resistance value r, are installed in parallel, if all of them are disconnected, the total resistance value will be ω, so the differential voltage value I (at - "t) l will be eb The above is 9. Conversely, if there is a main disconnection, the total resistance value is r/(n
-k)9, the voltage value el is ir/(n-k), so the expected voltage value i・r/n without any wire breakage
When υ is large, the difference voltage value I (e= -e't) l
is larger than el, and IITfIIA detection becomes possible. The disconnection detection circuit 12 outputs such a voltage difference and compares it with a set voltage value during each OFF period, and detects disconnection of the preheating plug GP early during heating control. Then, the voltage value eft of the previous off period stored in the memory circuit
After outputting the differential voltage, the current off-period voltage value C is determined by the update pulse R8 generated from the switching element control circuit 11.
8 and is used to obtain the difference from the voltage value of the next OFF period. The disconnection detection output GPDC1 obtained in this way is sent to the disconnection indicator 2, and an indication that there is a disconnection is performed.

This disconnection detection output GPDC1 is also sent to the disconnection number detection circuit 16, and the disconnection number detection circuit 16 receives the differential voltage value 1(at-e't)I from the disconnection detection circuit 12.

Here, the resistance value of each preheating plug during the OFF period before - cycle is white, and the resistance value of each preheating plug during the OFF period of the current cycle is r(
Then, before the -cycle, there is no preheating plug GP that is 1ITIi.
Since Il is not turned on, the voltage value elt is c11=i, hill (1). On the other hand, if k preheating plugs are turned off during the off period of this cycle, the voltage value CI is 1=1. °C=mouth
(2), and the differential voltage value V is 〆V = et-e', =i −(−−−)
(51n - k n ) Then, prepare the voltage values η, v, Vm, etc. obtained from equation (3) according to the disconnection rate 'Ikk.

r′ y, = H, (-i-jT--] and) r' V1=i・(-i-!T-],) and the difference voltage value V and this prepared nine comparison voltage value v1, ■
If you compare it with the proverb ``■maro...'', you can detect the number k of # and Ij.

In this way, the next detected tllri11ll
[The set temperature comparison circuit 100 outputs the set temperature voltage eclipse from k. Here, the set temperature voltage value e, which is actually set in the set temperature comparison circuit 10 KI, is: e,=lid/yu (4) However, r is the resistance value of each preheating plug at the scheduled preheating temperature.

The set temperature and voltage value e11 when k wires are broken is as follows, so the set temperature and voltage value e/, determined by equation (5), is determined according to the number of broken wires. This voltage value e/.

is set or stored as the set temperature voltage value of the set temperature comparison circuit 10. And the heating l1lI11 of the preheating plug GP
served. FIG. S is an explanatory diagram showing a change in the set temperature voltage value of the wire and the voltage value of the voltage drop of the preheating plug due to a disconnection during heating control. When a disconnection of the preheating plug is detected at time 11, the set temperature voltage value of the set temperature comparison circuit 10 changes from e to e.
′, is changed to Furthermore, due to the wire breakage, the voltage value e1 of the voltage drop also increases and changes to the square shown in the figure. Therefore, the voltage value et is compared with the set temperature voltage value changing in this manner as a reference and heating control is performed, so that the remaining preheating plugs are correctly controlled to the scheduled preheating temperature.

In the above explanation, an example is explained in which the control section 1 is divided into individual configurations from the comparison circuit 10 to the disconnection number detection circuit 14fi. .

Therefore, K, voltage value et is converted into digital value,
Input to the control unit 1, set voltage value ebleo, ed
is digitally stored in the main memory of the microcomputer, and the arithmetic circuit of the microcomputer calculates the superelectric EE value, compares it with the set voltage value, and calculates the drive signal according to a predetermined control program stored in the control program memory. This is to control generation.

As described above, according to the present invention, IITiI is detected,
The reference voltage value for heating control is changed according to the number of remaining unbroken preheating plugs, so even if any of the preheating plugs breaks, the remaining preheating plugs can be stably heated to the scheduled preheating temperature. Therefore, it is possible to easily start the engine using the remaining preheating plug without causing a leakage situation due to overheating.

Furthermore, according to the present invention, the number of disconnections is detected by flowing a constant current from the constant current circuit during the off period of the closing element to detect the voltage value of the voltage drop of the preheating plug. The number of #lyT plums can be detected without consuming power, and the accuracy is improved because it uses a constant current. Moreover, since the constant current circuit for temperature detection using the preheating plug temperature 111J II K is shared, the number of disconnections can be detected by simply capturing the voltage value, making the special KIII * less complicated and inexpensive. becomes possible. Furthermore, the number of broken wires is detected by determining the difference between the voltage value of the off-period of the previous cycle and the voltage value of the current off-period, and comparing the difference with a predetermined reference value, which is extremely effective in practical terms. .

Although the present invention has been described with reference to one embodiment, the present invention is not limited to the above-mentioned 11 embodiments, and various modifications can be made in accordance with the spirit of the present invention, and these may be considered within the scope of the present invention. It is not something to be excluded.

[Brief explanation of drawings]

The first part is a pull diagram of one embodiment of the present invention, and the second part is a 1W diagram.
The waveform diagram of each part of the fourth embodiment and FIG. 5 are diagrams illustrating the operation of the present invention. 111-wlt, TR-II@element, GP... Pre-11
1, CC...constant current circuit, AP...differential amplifier, 1
...Control unit, 2...Disconnection indicator, 12.13...
Disconnection detection circuit, 15-... disconnection number detection circuit. Patent applicant: Isuy Automobile Co., Ltd. (1 person) and 1 agent (Patent attorney): Mr. Tsuji (2 persons)

Claims (1)

[Claims] A switching element is inserted into the electric Wii path after preheating, and the control unit intermittently controls the switching element to control the heating of nine plurality of preheated circuits connected in parallel, and is connected to the preheating circuit 11 and connected to the nine constant current path. The off period of the switching element Kll! Preheating in which a constant current is passed through the preheating 46, a voltage value due to a voltage drop after the preheating is measured, and the control unit compares the measured voltage value with a reference voltage value according to the planned preheating temperature to control the switching element. In the stopper heating control device, the control unit includes a storage unit that stores 111111 constant voltage values, and the control unit stores the difference between the voltage value measured in the OFF period of the previous cycle and the voltage value measured in the current OFF period in the storage unit. Calculate the voltage value, detect whether or not there is a disconnection from the differential voltage value, and calculate the number of disconnections after preheating from the differential voltage value to 1lF.
A preheating plug heating control device configured to generate nine reference voltage values according to the number of illA wires, and changing the reference voltage value to the generated nine reference voltage values when a disconnection is detected.