JPS6282277A - Glow plug energizing control device - Google Patents

Abstract

PURPOSE:To prevent properties of ceramics from being changed by turning over the direction of feed current to ceramic heaters at certain time intervals so as to allow each of integrated values of applied current in the positive and negative directions to be approximately equal. CONSTITUTION:A preheat control unit 19 outputs the first preheat control signal S1 with a key switch 22 turned on allowing glow plugs 3 through 6 made of ceramics to be turned on or off through a switch 16 for preheating. Then an after glow performance is effected by the second preheat control signal S2 with a switch 20 turned on or off. And the signal S2 is also inputted into a switching circuit 18 allowing switches 13 and 14 to be changed periodically so as to switch the direction of feed current to the glow plugs 3 through 6 reversely. This configuration can prevent properties of ceramics effectively from being changed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a control device for a glow plug for an internal combustion engine, and more particularly to a control device for controlling energization of a glow plug having a ceramic heater.

(Prior art) Various glow plugs are used to preheat the cylinders of internal combustion engines, but so-called ceramic heater type glow plugs have good heat transfer efficiency and can perform as a fast heating type. Plugs are becoming more common. This type of glow plug is characterized in that it uses a ceramic heater in which a heater wire is embedded in a ceramic body formed in the shape of a rod (see Japanese Patent Publication No. 59-52725). Conventionally, when controlling the energization of a glow plug in this way, the positive electrode of the battery is usually connected to the electrode nut side of the glow plug, while the negative electrode of the battery is connected to the housing side of the glow plug. A switch disposed between the glow plug and the glow plug is turned on and off by a control signal from the energization control device, thereby controlling the energization of the glow plug.

(Problems to be Solved by the Invention) By the way, the present inventor has discovered that if the above-mentioned conventional energization control device is used to control the energization of a ceramic heater type glow plug for a long period of time, the ceramic heater will break down. I discovered this fact. In this process of ceramic heater destruction, the ceramic member first changes in quality on the negative potential side of the ceramic heater when the glow plug is energized, and this causes a crank to occur in the ceramic body starting from this deteriorated part, and the ceramic heater It will lead to destruction.

Therefore, an object of the present invention is to provide an energization control device for a glow plug for an internal combustion engine that prevents the ceramic heater from being destroyed even if the energization of the ceramic heater type glow plug is controlled for a long period of time. It's about doing.

(Means for solving the problem) In order to solve the above problem, the present inventor conducted various experiments, and as a result, the deterioration of the ceramic member that occurs on the negative potential side of the ceramic heater is This is due to the fact that the heating current is supplied only in one direction.The direction of the current supplied to the ceramic heater is reversed at appropriate time intervals, and the deterioration of the ceramic member is prevented by applying approximately the same amount of current in both directions. We have found that this can be effectively prevented.

The present invention is based on the above-mentioned novel findings, and the content thereof is to provide a glow plug energization control device for preheating a glow plug having a ceramic heater, which is provided between a DC power source and a glow plug. a switch means for reversing the direction of the preheating current supplied from the DC power supply to the glow plug; an integrated value of the amount of current applied to the glow plug in the forward direction; and switch control means for controlling the switch means to switch at required time intervals so that the values are substantially equal.

(Function) The switch control means performs switching control of the switch means, whereby the direction of the current supplied to the glow plug is switched at a required time interval, and the current is supplied to the glow plug in one direction. The energization of the glow plug is controlled such that a state is maintained in which the integrated value of the energization amount of the heating current is substantially equal to the integrated value of the energized amount of the heating current supplied in the other direction. .

(Embodiment) FIG. 1 shows a circuit diagram of an embodiment of a glow plug energization control device according to the present invention. A glow plug energization control device 1 connects glow plugs 3 to 6 equipped with ceramic heaters (not shown) from a patch IJ 2 that is a DC power source.
This is a device for controlling the preheating current supplied to the In the illustrated embodiment, each glow plug 3 to 6 has two
It has a terminal-type configuration, and therefore, each of the current-carrying terminals 3a to 6a on one side and the current-carrying terminals 3b to 6b on the other side of each of these glow plugs 3 to 6 are electrically insulated from the housing of each glow plug. When each glow plug 3 to 6 is attached to each cylinder of a four-cylinder diesel engine (not shown), these energizing terminals 3a to 6
a and 3b to 6b are electrically independent.

The current-carrying terminals 3a to 6a of each of these glow plugs
are commonly connected to the output terminal 11 of the glow plug energization control device 1, and the other energization terminals 3b to 6
b are connected in common and connected to the output terminal 12 of the energization control device 1.

The current supplied from the battery 2 is applied to the output terminals 11-12.
The positive direction from the output terminal 11 to the output terminal 12 or the output terminal 12 is caused by the glow plugs 3 to 6 connected between them.
The glow plug energization control device 1 includes a set of switches disposed between the battery 2 and the glow plugs 3 to 6 so that the power can be supplied in either direction from the battery 2 to the output terminal 11 in the opposite direction. 13.14. The movable contact 13a of the switch 13 is connected to the positive electrode of the battery 2, its fixed contact 13b is connected to the output terminal 11, and the other fixed contact 13c is connected to the positive electrode of the battery 2.
6 to the output terminal 12. On the other hand, the movable contact 14a of the switch 14 is connected to the negative electrode of the battery 2 and grounded, and its fixed contacts 14b and 14c are connected to the fixed contacts 13C and 13b of the switch 13, respectively. These switches 13 and 14 are switched as shown by solid lines or dotted lines depending on the energization state of the relay coil 17. In the illustrated embodiment, switches 13,14 are respectively switched as shown in solid lines when relay coil 17 is deenergized, and when relay coil 17 is energized by switch control circuit 18, which will be described below. Switches 13, 14 are each switched as indicated by the dotted lines.

Thus, when switches 13, 14 are switched as shown by the solid lines, they supply current from battery 2 in the positive direction to each glow plug, while switch 13
．． 14 is switched as shown by the dotted line, the current from the battery 2 can be supplied to each glow plug in the opposite direction.

The switch 16 is a switch for turning on and off the supply of rapid preheating current to the glow plugs 3 to 6, and is a switch for turning on and off the supply of rapid preheating current to the glow plugs 3 to 6. Turns on in response to preheating control signal S.

It will be turned off. After the rapid preheating operation of the glow plugs 3 to 6 is completed, a switch 20 and a current limiting resistor 21 are connected in parallel with the switch 16 for the purpose of performing afterglow operation, etc.
A series circuit with is connected. turning on the switch 20;
The off control is performed by the second preheating control signal S2 from the preheating control unit 19, and the switch 20 is
The switch 16 is once closed for the rapid preheating operation, and then when the switch 16 is opened due to the end of the rapid preheating operation, it is closed by the second preheating control signal S2 and is maintained in the closed state for a predetermined time.

The above-mentioned control operation of the preheating control unit 19, which outputs the first and second preheating control signals S, S, as described above in response to the operation of the key switch 22, is performed by a conventional preheating control unit of this type. This can be easily realized, and therefore, detailed explanation of the configuration of the preheating control unit 19 will be omitted here.

The second preheating control signal S2 also
is also entered. The switch control circuit 18 is composed of an astable/multi-by-break circuit that outputs a pulse signal with a predetermined cycle, and when the second preheating control signal Sz is in the first state in which the switch 20 is opened, the second preheating control signal S2 As a result, the generation of the pulse signal is suppressed, and the relay 15 is deenergized. On the other hand, when the second preheating control signal S2 is in the second state in which the switch 2° is closed, the switch control circuit 18 is brought into a state in which it outputs the pulse signal ps by the second preheating control signal s2, and the pulse signal ps is The relay 15 is repeatedly energized and deenergized according to the cycle, and the switch 13.
14 are switched periodically. As a result, in this embodiment, the glow plug 3 in the case of rapid preheating operation
The direction of the current supplied to 6 to 6 is the positive direction, but during the preheating operation period after rapid preheating, the direction of the supplied current is periodically switched between positive and reverse according to the period of the pulse signal PS. It will be done.

According to the above-described configuration, the glow plug energization control device 1 includes:
During the preheating operation period after the rapid preheating operation, the glow plug 3
The direction of the heating current supplied to the heating devices 6 through 6 is alternately switched between forward and reverse at regular intervals. Since the rapid preheating operation period is extremely short compared to the entire energization control period by the glow plug energization control device 1, when the supply direction of the supply current is alternately switched between forward and reverse as described above, the amount of energization flowing in each direction is The respective integrated values are approximately equal.

As a result, deterioration in each ceramic heater part of the glow plug is effectively prevented, and even after long-term use, glow plugs 3 to 6 do not suffer from any defects, and the lifespan of the glow plugs is reduced compared to conventional energization control devices. This can be significantly extended compared to when using .

In the above embodiment, the direction of supplying current to the glow plug is regularly changed only after rapid preheating, but the present invention is not limited to this configuration. In other words, the period of reversal of the direction of current supply to the glow plug is set to a relatively long period so that the integrated value of the amount of energization in the forward direction and the integrated value of the amount of energized in the reverse direction match at an appropriate time interval. Alternatively, the current supply direction may also be reversed during the rapid preheating operation. Therefore, for example, a configuration may be adopted in which the direction of the current supplied to the glow plug is reversed each time the engine is started.

Furthermore, although this example describes the case where a two-terminal type glow plug is used, even in the case of a single-pole type glow plug, the housing should be attached to the engine cylinder so that it is electrically insulated from the engine casing. Of course, by attaching it, a circuit configuration as shown in FIG. 1 can be easily realized.

FIG. 2 shows a circuit diagram of another embodiment of the glow plug energization control device according to the present invention. The glow plug energization control device 30 shown in FIG. 2 is installed between the battery 2 and the ceramic heater type glow plugs 3 to 6 for the same purpose as the glow plug energization control device shown in FIG. ing.

In FIG. 2, the same parts as those in FIG. 1 are designated by the same reference numerals, and their explanations will be omitted. In this embodiment, the glow plugs 3, 4 and 5, 6 are connected in parallel and divided into two groups as shown in the figure, and the glow plug energization control bag R3
0 is a configuration in which these two sets of glow plugs are connected in parallel for preheating during rapid preheating, and on the other hand, these two sets of glow plugs are connected in series for preheating during afterglow operation after completion of rapid preheating. .

The glow plug energization control device 30 has three output terminals 31.
32 and 33, and the output terminal 31 has one terminal 3a of each of the glow plugs 3 and 4.

4a are commonly connected, and terminals 5a and 6a of each of the glow plugs 5 and 6 are commonly connected to the output terminal 32. The other terminals 3b to 6b of the glow plugs 3 to 6 are commonly connected to the output terminal 33, and this output terminal 33 is connected to the negative terminal of the grounded batch I72 via an on/off switch 34. It is connected.

The output terminals 31 and 32 are connected to the movable contacts 35 of the first switch 35 and the second switch 36 arranged correspondingly.
a and 36a, respectively. 1st switch 3
5 and the fixed contact 35b of each one of the second switch 36, 3
6b are commonly connected and grounded, and each other fixed contact 35c.

36c are commonly connected and connected to the positive electrode of the battery 2.

On, off switch 34, first and second switches 35.
36 is a control signal U output from the control unit 37;
, U, and U, respectively. In the illustrated embodiment, each switch is configured to be in the switching state indicated by a solid line when the level of the corresponding control signal is rLJ, and to be in the switching state indicated by a dotted line when the level of the corresponding control signal is rHJ. .

On the other hand, a key switch 38 is connected to the control unit 37, and the control unit 37 can determine the position of the key switch 38, and depending on the operation of the key switch 38, the above-mentioned It outputs control signals Ul to U3 for operating each switch.

In FIGS. 3(a) to 3(d), the key switch 38
Control signals U, to U obtained for the operation of.

3(a) to 3(d) below.
The operation of the glow plug energization control device 30 will be explained based on the time chart shown in FIG.

Time 1=1. When the key switch 38 is switched from the OFF position to the ON position, the level of the control signal U23U3 both changes from rLJ to rHJ, and the first and second
The switch terminals 35 and 36 are both switched as shown by dotted lines, and the output terminals 31 and 32 have the same potential as the positive electrode of the battery 2.

At this time, the level of the control signal U remains rLJ,
Since the on/off switch 34 is in the closed state, each of the glow plugs 3 to 6 is directly connected to the battery 2 and is in a rapid preheating state. Thereafter, when the key switch 38 is switched to the ST position at 1=12, at 1=1° after a predetermined time Δt, the level of the control signal U becomes rHJ and at the same time the level of the control signal U2 becomes rLJ.

As a result, the switch 34 is opened and the first switch 35 enters the switching state shown by the solid line, so that the glow plug 3.
The parallel circuit of 4 and the parallel circuit of 5.6 glow plugs are connected in series to the battery 2. Therefore, the value of the current supplied to each glow plug is 1. <1
<3, and enters an afterglow operating state in which the temperature of the glow plug is maintained at a predetermined value without overheating the glow plug.

During the afterglow operation period, the curvature of the voltage appearing between the output terminals 31 and 32 is periodically reversed, and the supply direction of the heating current supplied to the glow plug is periodically reversed. The levels of the control signals uz, u:l are inverted synchronously at a predetermined period. For this reason, for example, when 1=14, the first switch 35 is switched as shown by the dotted line, and the second switch 36 is switched as shown by the solid line, and the supply direction of the supply current to the glow plugs 3 to 6 is is reversed.

In this way, 1=1. Since the direction of the supply current to the glow plugs 3 to 6 is reversed at the required time interval until the power supply is stopped at , the integrated values of the amount of power supplied in the forward and reverse directions to each glow plug are approximately equal; Deterioration of each ceramic heater of the glow plugs 3 to 6 can be effectively prevented.

FIG. 4 shows still another embodiment of the glow plug energization control device according to the present invention. In Figure 4, the first
Components corresponding to the respective parts in the figure are given the same reference numerals as those used in FIG. 1, and their explanations will be omitted. The glow plug energization control device 40 has switches 41.42, each of which has a movable contact 4.1a.
, 42a are connected to output terminals 43.44. The fixed contacts 41a, 42a of each one of the switches 41, 42 are connected in common to the positive electrode of the battery 2, and the other fixed contacts 41b, 42b of the switches 41, 42 are grounded together with the negative electrode of the battery 2. The switches 41 and 42 are configured to be switched and controlled by control signals V, V2 from a control unit 44 connected to the key switch 43, respectively.

The switches 41 and 42 are in the switching state shown by the dotted line when the level of the applied control signal is rLJ, and are in the switching state shown by the dotted line when the level is "H". Glow plugs 3 to 6 are connected in parallel between output terminals 43 and 44, and heating current is supplied to glow plugs 3 to 6 according to the switching state of switch 41, 42.

5(b) and 5(c) show how the levels of the control signals V, V2 outputted from the control unit 40 in response to the operation of the key switch 43 are changed. Hereinafter, the operation of the glow plug energization control device 40 will be explained based on the time charts shown in FIGS. 5(a) to 5(c).

Time 1=1. When the key switch 43 is switched from the leaf F position to the ON position, only the level of the control signal (2) becomes rHJ, and only the switch 41 is switched as shown by the dotted line. Therefore, the preheating current is supplied in the direction from the output terminals 43 to 44, and the glow plugs 3 to 6 are rapidly preheated. When the preheating is completed at 1=1h and the key switch 43 is further switched to the ST position, the level of the control signal 1 changes at a predetermined period, and the preheating flows intermittently to the glow plugs 3 to 6.
To maintain the required temperature without overheating the glow plug. When the starting operation by the key switch 43 is completed at 1=1c, the control signals V, , V2 are as shown in FIG. 5(b).
As shown in (c), the current is intermittently supplied to the glow plugs 3 to 6, and the range of the supplied current and the amount of power are alternately reversed each time the power is supplied. That is, when the key switch 43 is switched from the ST position to the ON position (t=tC), the level of the control signal 2 becomes rLJ, and the energization to the glow plugs 3 to 6 is stopped. After that, 1d<1<1. During this period, only the level of the control signal (2) becomes rHJ, and during this period, current is supplied to the glow plugs 3 to 6 from the output terminals 44 to 43. Then, when (,<1<1g, only the level of the control signal v1 becomes rHJ, and the output terminal 43
Current is supplied to the glow plugs 3 to 6 from 44 to 44.

Thereafter, the relays 41 and 42 are operated in the same manner, and the preheating current is intermittently supplied to the glow plugs 3 to 6 alternately in the forward or reverse direction. As a result, the respective integrated values of the amount of power supplied in the forward and reverse directions to each glow plug become approximately equal, and deterioration of the quality of each ceramic heater of the glow plugs 3 to 6 can be effectively prevented.

In addition, in the embodiment described above, the power supply direction is not changed during rapid preheating, but since the rapid preheating period is a very small period compared to the entire preheating time, no particular problem occurs. .

(Effects) According to the present invention, as described above, by reversing the direction of the current supplied to the ceramic heater at appropriate time intervals, the integrated values of the amount of current in each of the forward and reverse directions become approximately equal. Therefore, deterioration of the ceramic member of the ceramic heater can be effectively prevented, and the ceramic glow plug can be used stably for a long period of time.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing one embodiment of a glow plug energization control device according to the present invention, FIG. 2 is a circuit diagram showing another embodiment of the present invention, and FIGS. 3(a) to 3(d) is a time chart for explaining the operation of the device shown in FIG. 2, FIG. 4 is a circuit diagram showing still another embodiment of the present invention, and FIGS. 3 is a time chart for explaining the operation of the device shown in the figure. 1.30.40...Glow plug energization control device, 3 to 6...Glow plug, 13,14,41.42...
- Switch, 18... Switch control circuit, 35...
1st switch, 36... 2nd switch.

Claims (1)

[Claims] 1. In a glow plug energization control device that performs energization control for preheating a glow plug having a ceramic heater, a glow plug energization control device is provided between a DC power source and the glow plug to control the supply direction of the preheating current supplied from the DC power source to the glow plug. A switch means for reversing the direction, and the switch means is operated for a required period of time so that the integrated value of the amount of current applied to the glow plug in the forward direction and the integrated value of the amount of current applied in the reverse direction to the glow plug are substantially equal. A glow plug energization control device comprising: switch control means for controlling switching at intervals.