JPH06108959A - Glow plug control device for engine - Google Patents

Abstract

PURPOSE:To realize a stable ignition state constantly in the whole operating region by controlling the current carrying quantity taking account of the external cooling degree such as the change of intake air quantity. CONSTITUTION:In an engine 11 using fuel such as methanol of low cetane value force-ignited by glow plugs 11 in the whole operating region, the current carrying quantity to the glow plugs 11 is adjusted according to the change of intake quantity at the time of executing intake throttle or the like. The heating temperature is thereby kept always to the desired ignition temperature regardless of the external cooling degree.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine glow plug control device.

[0002]

2. Description of the Related Art For example, in a diesel engine, when a fuel having a low cetane number such as methanol is used as an alternative fuel, compression ignition is generally difficult. Therefore, normally, a spark assist system using a spark plug or a glow assist system using a glow plug is adopted as a forced ignition device (for example, see Japanese Utility Model Laid-Open No. 58-79022).

[0003]

By the way, when the glow plug as the ignition assist system as described above is used for the fuel having a low cetane number, it is required to control the energization not only at the time of starting but also in the entire operating range. In addition, if the proper energization amount is not maintained in each operation range, there is a problem that misfire due to insufficient glow temperature, overheat deterioration (burnout) due to too high glow saturation temperature, and disconnection may occur.

In this regard, depending on the load range of the engine,
In particular, in the high load region, there is already a device for improving the combustibility under high engine load and improving the durability of the glow plug by lowering the temperature of the glow plug (for example, Japanese Patent Laid-Open No. 3-33447). reference).

On the other hand, if an intake throttle valve is provided in the engine intake passage and the intake air amount is reduced especially at low load, the concentration of the air-fuel mixture around the glow plug is increased and the combustibility is improved. In that case, it is not preferable to increase the energization amount because it is in the low load region.

[0006]

Claims 1 and 2 of the present application
The inventions described in the respective items were made for the purpose of solving the above problems, and are configured as follows.

(1) Structure of an engine glow plug control device according to a first aspect of the present invention: An engine glow plug control device according to the present invention is a glow plug for forcibly igniting air-fuel mixture in an engine combustion chamber, and an operating state of the engine. In an engine having an intake throttle valve that throttles the intake air amount to the engine according to the above, the energization amount control means for controlling the energization amount to the glow plug to be smaller as the intake air throttle amount of the intake throttle valve is larger. Is provided.

(2) Structure of an engine glow plug control device according to a second aspect of the present invention is the engine glow plug control device according to the first aspect of the present invention, wherein the temperature of the glow plug is predetermined. It is characterized in that feedback control means for performing feedback control to the temperature is provided.

[0009]

The glow plug control device for an engine according to the first and second aspects of the invention of the present application is configured as described above, and as a result, the following actions are performed corresponding to the respective configurations.

(1) Operation of the engine glow plug control device according to the first aspect of the invention In the configuration of the engine glow plug control device according to the present invention,
First, as a basic configuration, a glow plug as an ignition assisting means for electrically heating an air-fuel mixture in an engine combustion chamber and forcibly igniting the mixture over the entire operating region, and intake to the engine depending on the operating condition of the engine such as a load region An intake throttle valve that throttles the amount of air is provided.

For example, when the air-fuel mixture concentration around the glow plug is low and the load is low, when the intake throttle valve is operated to limit the intake air flow rate, the air-fuel mixture concentration around the glow plug increases and the combustibility is improved. be able to. Therefore, the startability at the time of cold by the glow plug is also improved. At the same time, in the same cold / low load region, if the intake throttle is performed, the amount of surplus air that does not contribute to combustion can be reduced, so that the exhaust gas temperature easily rises and the activation of the catalyst is promoted. . As a result, the amount of HC generated during cold can be effectively reduced.

In addition, in the glow plug control device for an engine according to the invention of claim 1, in addition to the same configuration, the energization amount to the glow plug is further increased when the throttle amount of the intake air amount by the intake throttle valve is large. When the amount of intake air is reduced, the degree of cooling of the glow plug is low, and the concentration of the air-fuel mixture around the plug is high, resulting in good ignition performance. The amount of electricity supplied to is also reduced to prevent overheating and improve durability.

(2) Operation of the engine glow plug control device according to the second aspect of the present invention In the configuration of the engine glow plug control device according to the second aspect of the present invention, in the configuration of the first aspect of the invention, Further, feedback control means for feedback-controlling the temperature of the glow plug to a predetermined temperature is provided to maintain the temperature of the glow plug at a predetermined proper target temperature corresponding to the warm-up state, load, and intake air amount state with high accuracy. ing.

Therefore, it is possible to always ensure good ignitability and durability of the glow plug over the entire operating region.

[0015]

As a result of the above, according to the engine glow plug control apparatus of the present invention, good ignitability is always obtained regardless of changes in the glow plug cooling degree even when a fuel having a low cetane number such as methanol is used. In addition to being maintainable, good exhaust gas purification performance can be secured, and the reliability of the glow plug itself is also improved.

[0016]

Embodiments of the present invention will now be described with reference to the drawings. First, FIG. 1 is an overall configuration diagram of an alcohol diesel engine equipped with a glow plug control device according to an embodiment of the present invention.

In FIG. 1, reference numeral 1 is an engine,
The intake passage 2 downstream of the air cleaner 39 of the engine 1 is provided with an intake throttle valve 3, and the exhaust passage 4 is provided with an oxidation catalyst 5. Also, the exhaust passage 4 and the intake passage 2
Exhaust gas recirculation passage (EGR passage) that connects them to
6 is provided, and an EGR valve 7 is arranged in the middle of the EGR passage 6. The intake throttle valve 3 is opened and closed by the intake throttle actuator 8 and the EGR valve 7 is opened and closed by the EGR actuator 9.

The specific construction of the engine 1 is shown in detail in FIG. 3, where 21 is a cylinder block, 22 is a cylinder head, 23 is a piston having a stratified combustion chamber 23a formed on its top, and 24 is a camshaft. , 25 is a rocker arm, 26 is a push rod for driving the rocker arm 25, and 27 is an intake valve. In addition, the engine 1 has a fuel injection valve 10 for each cylinder and a glow plug 11 having a mixture storage space 11a as shown in FIG.
Further, each of the fuel injection valves 10 is provided with a fuel injection pump 12 for pressurizing, measuring and delivering a methanol fuel having a low cetane number. The fuel injection pump 12 is
Although it has a structure known per se, illustration and detailed description thereof are omitted, but an electronic governor for controlling the fuel injection amount, a timer for controlling the fuel injection timing are additionally provided, and the timer is
An injection timing control valve that controls the hydraulic pressure is connected. Further, 42 is a methanol fuel tank, 41 is a fuel filter, 40
Is a priming pump.

On the other hand, reference numeral 13 is an engine control unit. The input circuit section of the engine control unit 13 has an engine speed N, an accelerator opening (engine load) A, an intake air temperature TA, an engine water temperature TW, and an engine oil temperature. , Intake pressure B, glow voltage Vg, rack position LP of the electronic governor, etc. (not shown)
The engine control unit 13 receives the detection signals from the intake throttle actuator 8, the EGR actuator 9, the glow plug control unit 30, the electronic governor of the fuel injection pump 12, and the injection timing control valve based on the detection signals. And so on. Glow plug 11
Are controlled via the glow plug control unit 30 as described below.

Next, FIG. 2 is a block diagram showing the construction of the control system of the glow plug 11 centering on the engine control unit 13.

The glow plug control system is composed of a target current calculation system formed by the engine control unit 13 and a glow temperature feedback control system formed by the glow control unit 30.

The target current calculation system includes an input circuit 31 to which the accelerator opening A, the engine speed N, the engine water temperature TW, the rack position LP, and the intake pressure B are input, and the input circuit 31 based on these inputs. It is composed of a target current calculator 33 that calculates a target current Ig based on the target resistance value Rg calculated by the target resistance calculator 32 that calculates a target resistance Rg from the output.

Further, the glow temperature feedback control system uses the target current Ig calculated by the target current calculator 33.
And an actual current I to the glow plug 11 are input to output a deviation current ΔI (ΔI = Ig ± I) between them, and the deviation current ΔI is input to correspond to the deviation current ΔI. The glow plug drive circuit 35 supplies the electric current I to the glow plug 11.

The target resistance calculation unit 32 of the above target current calculation system
Has a glow plug temperature Tg calculation unit 32A and a target resistance value Rg calculation unit 32B. Rack position LP
Using the engine speed N and the engine speed N as load determination parameters, the basic target temperature Tgo for determining the basic energization amount is read from the target temperature base map of FIG. 5, and the engine warm-up progress state is read with respect to the basic target temperature Tgo. The target glow plug temperature Tg is calculated by subtracting the water temperature correction value Tgw (Tg = Tgo-Tgw) determined by using the engine water temperature TW as a parameter in consideration of the map of FIG.

Next, the target resistance value Rg calculating section 32B inputs the final target glow plug temperature Tg calculated as described above, and based on this, the target resistance value Rg is calculated using the glow resistance map of FIG. Glow plug for achieving temperature Tg 1
The resistance value Rg of 1 is calculated (indirectly converted into a resistance value).

Further, in the subsequent target current calculation unit 33, the power supply voltage (applied voltage = constant) Vg to the glow plug 11 is divided by the resistance value Rg (Vg / Rg) to control the supply to the glow plug 11. The target current Ig is calculated.

Then, the difference ΔI between the actual current I and the target current Ig corresponding to the present operating state is calculated by the comparator 34.
Detected by the glow plug drive circuit according to the difference ΔI
The (drive current variable control circuit) 35 is feedback-controlled for each cylinder, the actual current I is controlled so as to converge to the target current value Ig, and the surface temperature of the glow plug 11 is maintained at the target temperature Tg.

As a result, even when the engine is cold, an appropriate glow plug temperature is realized regardless of changes in the intake flow rate due to intake throttle control, and problems such as misfire, deterioration of durability due to overheating, and disconnection occur. Disappear.

[Brief description of drawings]

FIG. 1 is an overall control system diagram of an engine glow plug control device according to an embodiment of the present invention.

FIG. 2 is a control circuit diagram of a main part of the device.

FIG. 3 is a schematic cross-sectional view of an engine to which the same device is applied.

4 is an enlarged cross-sectional view of a glow plug portion of the engine of FIG.

FIG. 5 is a basic target temperature map used in the control of the glow plug control device.

FIG. 6 is a same water temperature correction map.

FIG. 7 is the same glow resistance map.

[Explanation of symbols]

1 is an engine, 11 is a glow plug, 13 is an engine control unit, 30 is a glow control unit, 31 is an input circuit, 32 is a target resistance calculation unit, 33 is a target current calculation unit, 34 is a comparator, and 35 is a glow plug drive circuit. Is.

Claims (2)

[Claims] 1. An engine comprising a glow plug for forcibly igniting an air-fuel mixture in an engine combustion chamber in all operating regions, and an intake throttle valve for reducing an intake air amount to the engine according to an operating state of the engine, A glow plug control device for an engine, comprising an energization amount control means for controlling the energization amount to the plug to be smaller as the intake air amount of the intake throttle valve is larger. 2. The glow plug control device for an engine according to claim 1, further comprising feedback control means for feedback controlling the temperature of the glow plug to a predetermined temperature.