JPH0949485A - Glow plug control device for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely prevent particularly a misfire by assisting ignition with glow plug control, by using a glow plug in a combustion chamber of a compression ignition engine even when it is operated except when started. SOLUTION: A device comprises a λ sensor 13 provided in an exhaust system of an engine 1 to detect an excess air factor λ, glow plug 5 arranged in a combustion chamber C of the engine for increasing a temperature of fuel supplied to this combustion chamber to promote combustion and a control unit 14 performing carrying of a current in the glow plug 5 when the excess air factor λdetected by the λ sensor 13 is smaller than a prescribed value λ1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a glow plug of an engine, and more particularly to a control device for a glow plug suitable for assisting ignition at the time of starting an engine for compression ignition.

[0002]

2. Description of the Related Art In a compression ignition engine, for example, a diesel engine, intake air is compressed in a combustion chamber to a high temperature and a high pressure. ing. However, at the time of starting this diesel engine, especially at cold start, the temperature of the combustion chamber itself is low, and due to the low rotation, the high pressure and high temperature due to compression do not proceed relatively, and the ignitability easily deteriorates, causing a problem in starting. was there. Therefore, a glow plug for heating the fuel particles is generally installed in the fuel spray area of the combustion chamber, and this glow plug is driven during low temperature starting when the temperature of the combustion chamber is low, which assists ignition during starting. I'm trying to do.

It is known that the ignition assistance by the glow plug is continuously performed for a certain time when the engine key is turned on, or the glow plug is continuously energized until the engine water temperature reaches a set temperature. An example of energization control of a glow plug of a diesel engine is disclosed in Japanese Patent Publication No. 3-7026.

[0004]

By the way, the compression ignition type engine of this kind has a low ignition load in a low load and low revolution range where the temperature of the combustion chamber is relatively low even after the engine is started, and the engine has no misfire margin. There was a possibility of misfire, and there was a problem of increased emissions of HC due to misfire. Furthermore, when the intake passage facing portion of the supercharger acts as an intake throttle in the initial stage of starting, or when the intake passage is equipped with an intake throttle valve, when this intake throttle valve operates in a predetermined operating range However, the temperature of the combustion chamber did not rise, the ignitability deteriorated, and an engine with no allowance for misfires misfired, possibly increasing the amount of HC emissions.

As described above, if the ignition performance is lowered in some cylinders due to the change in the operating condition of the vehicle and the influence of the outside air temperature, and a misfire is caused, there is a possibility that the amount of HC discharged during traveling will increase. In this way, the ignition assistance of the glow plug becomes unstable,
Alternatively, if it becomes insufficient and engine misfires occur intermittently, it is necessary to perform ignition assistance that can avoid misfires with good responsiveness, and improvement thereof is desired. The purpose of the present invention is
It is an object of the present invention to provide a reliable glow plug control device for an engine, which can sufficiently secure the ignitability of the engine and can reliably prevent misfire.

[0006]

In order to achieve the above object, the present invention according to claim 1 provides an oxygen sensor provided in an exhaust system of an engine for detecting an excess air ratio and a combustion chamber of the engine. There is provided a glow plug that is provided and that raises the temperature of the fuel supplied to the combustion chamber to promote combustion, and control means that energizes the glow plug when the excess air ratio detected by the oxygen sensor is smaller than a predetermined value. It is characterized by having done.

The invention according to claim 2 is the glow plug control device for a diesel engine according to claim 1,
The control means energizes the glow plug when the excess air ratio detected by the oxygen sensor is higher than a predetermined value and lower than a predetermined engine speed and lower than a predetermined accelerator opening.

According to a third aspect of the present invention, an oxygen sensor provided in an intake system or an exhaust system of the engine for detecting an excess air ratio and a fuel provided in the combustion chamber of the engine are provided. A glow plug that raises temperature and promotes combustion, an engine speed detection unit that detects an engine speed, an accelerator opening detection unit that detects an accelerator opening,
Prior to the excess air ratio, there is provided control means for energizing the glow plug in accordance with both outputs of the engine speed and the accelerator opening.

According to a fourth aspect of the present invention, in the engine glow plug control device according to the third aspect, the control means is such that the engine speed is equal to or lower than a predetermined speed and the accelerator opening is equal to or lower than a predetermined opening. At this time, the glow plug is energized.

According to a fifth aspect of the present invention, in the engine glow plug control device according to any one of the first and fourth aspects, the control means continues energizing for a predetermined period after energizing the glow plug. It is characterized by

According to a sixth aspect of the present invention, there is provided a glow plug which is disposed in a combustion chamber of the engine and which raises a temperature of fuel supplied to the combustion chamber to promote combustion, and a misfire detecting means for detecting misfire of the engine. And a control means for energizing the glow plug for a predetermined time in response to a detection signal of the misfire detection means.

The invention according to claim 7 is the glow plug control device for a diesel engine according to any one of claims 1 and 6, further comprising cooling water temperature detecting means for detecting a cooling water temperature of the engine. The control means always energizes the glow plug when the cooling water temperature detected by the cooling water temperature detecting means is lower than a predetermined value.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The engine glow plug control system of FIG. 1 is installed in an in-line 4-cylinder diesel engine (hereinafter simply referred to as engine) 1. The first cylinder will be mainly described because each cylinder in this engine has the same configuration. Here, the engine 1 is provided with a combustion chamber C for each cylinder, and the combustion chamber C is configured to have a variable volume by a cylinder block 2, a cylinder head 3, and a piston 4 that slides in the cylinder block. The cylinder head 3 is equipped with an intake / exhaust valve, a fuel injection valve 4 and a glow plug 5, which are not shown, and these are arranged so as to face the combustion chamber C. Here, the fuel injection valve 4 is connected to a fuel injection pump 7 via an injection pipe (not shown), and the glow plug 5 is connected to a glow plug energization circuit 8.

The intake passage IR of the engine 1 is formed by an intake pipe 9 connected to the cylinder head 3, an intercooler 6 in the middle of the pipe, an air cleaner 10 on the tip side, and the like.
The exhaust passage ER is formed by the exhaust pipe 11, an unillustrated oxidation catalyst, a muffler, and the like. A compressor 121 of the supercharger 12 is provided in the middle of the intake passage IR, and a turbine 122 of the supercharger 12 is provided in the middle of the exhaust passage ER. A λ sensor 13 as an oxygen sensor is installed in the middle of the exhaust passage ER, and this sensor is connected to a control unit 14 which constitutes a control means and can output a signal corresponding to the excess air ratio λ to the control unit 14.

The fuel injection pump 7 for supplying fuel to the fuel injection valve 5 is connected to the control unit 14 and the fuel injection amount and injection timing are controlled. A glow plug energizing circuit 8 and a control unit 14 are connected to the glow plug 5. The glow plug energizing circuit 8 connects between the glow plug 5 and the power source B, and forms an intermittent switching circuit using a known switch transistor or the like.

The control unit 14 shown in FIG. 1 is constructed of a microcomputer as its main part, and a ROM (not shown) stores a flow chart (see FIG. 6) of a later-described glow plug control program and various maps and set values are stored. It A predetermined reference voltage is applied from the power source B to the control unit 14, and an engine speed Ne, which is information on the operating state of the engine, is input to an input / output circuit (not shown) from the engine speed sensor 17 by the engine speed sensor 17. The accelerator opening LPS corresponding to the lever opening (corresponding to the accelerator opening) is input from the load sensor 18, and the engine water temperature Tw is input from the water temperature sensor 19.

Here, the control unit 14 of FIG.
Has the following functions. That is, when the excess air ratio λ detected by the λ sensor 13 as the control means is smaller than the predetermined value λ1 (for example, 1.5 (equivalent to stoichio)), the control unit 14 regards it as a misfire area, and sends it to the glow plug 4. Energize. In this case, in particular, when the excess air ratio λ detected by the λ sensor 13 is larger than the predetermined value λ1 (not the misfire region from the excess air ratio λ) and is equal to or lower than the predetermined engine speed Ne1 and the predetermined accelerator opening LPS1. The glow plug 5 is also energized (in a region where there is a high possibility of misfire).

Further, the control unit 14 continues energizing for a predetermined period (Te) after energizing the glow plug. Further, the control unit 14 includes a water temperature sensor 19
When the cooling water temperature Tw detected by is smaller than a predetermined value Tw1 (for example, warm-up completion water temperature), the glow plug 5 is always energized.

Here, the control unit 14 presets a glow plug drive range calculation map m-1 for determining the drive range of the glow plug 5, and uses this map m-1 to determine the drive range of the glow plug 5. It is calculated. The map m-1 here is for calculating the low rotation and low load region M1 in which the increase in HC emissions due to misfire is a problem, and this also functions as misfire detection means, and the engine speed Ne is the predetermined engine speed. An operating range that is equal to or less than Ne1 (threshold value in the low speed range) and an accelerator opening LPS that is equal to or less than a predetermined accelerator opening LPS1 (threshold value in the low load range) is determined. The glow plug drive range calculation map for determining the drive range of the glow plug 5 is appropriately set according to each engine characteristic, for example, the low rotation medium load range M2 shown by the chain double-dashed line in FIG. Is also good. Furthermore, as shown in FIG. 3, the engine braking range e1 may be excluded, and a map m-2 may be used in consideration of misfire prevention in the range e2 in which the vehicle keeps traveling uphill with a medium rotation and medium load.

As shown in FIG. 4, the glow plug 5 has a temperature rise time Tg peculiar to the glow plug, and after the temperature rise, there is a predetermined period Te after energization, which is the time for the ignition peculiar to the engine to stabilize. . Therefore, in this case,
The energization time Δt is set as a time obtained by adding the temperature increase time Tg and the predetermined period Te, that is, Δt = Tg + Te. It should be noted that, during the predetermined period Te after the power supply, the glow temperature Tg
May be feedback-controlled to the set value Tg1. In this case, the glow resistance value Rg is based on the proportional relationship between the glow temperature Tg and the glow resistance value Rg as shown in FIG.
The glow temperature Tg is calculated from the above, and the duty ratio, which is the open / close ratio of the switch transistor (not shown) in the glow plug energizing circuit 8, is increased / decreased according to the difference between the value and the set value Tg1, and the glow temperature Tg is changed as shown in FIG. Set value Tg1
You may keep it.

Here, the operation of this apparatus will be described with reference to the flow chart of the glow plug control program of FIG. The control unit 14 enters the control of a main routine (not shown) and reaches the glow plug control program at a predetermined time. In step s1, the water temperature Tw is fetched from the water temperature sensor 19 and stored in a predetermined storage area. In step s2, it is determined whether or not the water temperature Tw1 after completion of warm-up is exceeded, and if it exceeds, the process proceeds to step s4, and in the following, the glow plug 5 is energized in step s3, and the process proceeds to step s4. That is, in step s3, the glow plug is operated at the cold start.

In step s4, it is judged whether or not the glow plug 5 has already been driven. If the glow plug 5 is already driven, this flow is ended, and the process proceeds to step s1 to take in the water temperature Tw and the driving of the glow plug 5 at the time of cold start is completed. Then, when the power is off, the process proceeds to step s5. In step s5, the engine speed Ne, the accelerator opening LPS, and the excess air ratio λ are taken in, and the process proceeds to step s6. In step s6, it is determined whether or not the latest excess air ratio λ is less than a predetermined value λ1 (for example, 1.5 (equivalent to stoichio)), and if Yes, step s1
If No, go to step s10.

Since the engine is on the rich side, from step s6, or when it is regarded as a misfire area and each reaches step s13 from step s11, step s7 is reached unless the flag F indicating the energized state is "1", H
In order to promptly suppress the discharge of C, the glow plug 5 is energized, and it is assumed that the glow plug has been switched from the non-energized state to the energized state, the process proceeds to step s14, the flag F is set to "1", and the process proceeds to step s8. In steps s8 and s9, an on-timer (not shown) is started in response to the glow plug 5 being turned on, and waits until the count value CUT of the on-timer exceeds the glow energization time Δt. Here, since the glow plug 5 requires a desired time from energization to heat generation, after the glow plug 5 is turned on, the glow plug 5
Is set to be the glow energization time Δt, or the time from when the glow plug 5 is turned on to when the glow plug operates and a predetermined time elapses. Until Δt elapses in step s9, that is, if Yes, step s
9 is looped, and if Δt passes and becomes No, step s
Return to 5.

On the other hand, if the excess air ratio λ does not fall below the predetermined value λ1 in step s6, that is, if it is in the lean operation range, and when step s10 is reached, the current engine speed Ne and accelerator opening LPS are called here. , Whether or not the operating range corresponding to the same value is in the low rotation / low load range M1 is calculated using the glow plug control range calculation map m-1. Next, at step s11, the current operation range is the low rotation / low load range M.
If it is judged to be 1, the judgment is made in step s13, and if it is judged not to be in the misfire area, it is judged in steps s12 and s
After 15, the control of this time is terminated and the process returns to the main routine. If the glow plug 5 is already energized at the time when step s12 is reached, this is turned off, and the flag F is returned to "0" at step s15.

If the result of determination in step s11 is in the low rotation / low load region M1 which is regarded as the misfire region, the process proceeds to the above-mentioned step s13 side, and unless the flag F is "1", the process reaches step s7 and the glow plug Drive 5 and take measures against misfire,
The discharge of HC is promptly suppressed, the flag F is set in step s14, and the process proceeds to steps s8 and s9. Step s8,
In s9, when the count value CUT exceeds the glow energization time Δt after the timer starts, the process returns to step s5 on the No side. Here, each value of Ne, LPS, and λ is fetched again, and if the fetched value of λ is not <1.5, s1
0, go to s11, determine the control range from Ne, LPS,
If No, it is determined that the region is not in the misfire region, and the energization of the glow plug is terminated in step s12.

The flag F is "1" in step s13.
However, when the glow plug is continuously energized after the glow energization time Δt has elapsed in step s9, the glow plug ON control in step s7 is skipped, and only the timer is used. Will start again. Further, the flag F is returned to "0" in step s15 after turning off the glow plug.

As described above, after it is determined Yes in step s9, whether the glow plug is continuously energized from the latest values of λ, Ne, and LPS after the glow plug is energized for Δt time, or is it ended? The determination is made in steps s6 and s11. If the warm-up is insufficient, the process proceeds to steps s13, s8 and s9 again, and the glow plug is continuously energized. As a modified example of the glow plug control device for the engine of this embodiment, step s in FIG.
The steps 6, s10 and s11 may be performed in the reverse order.

That is, in this case, first, it is determined whether or not to energize the glow plug according to both outputs of the engine speed and the accelerator opening, from a map according to the engine speed and the accelerator opening, After that, the configuration may be such that the determination is made based on whether or not the excess air ratio λ is less than 1.5. In this case, the energization amount according to the engine speed and the accelerator opening can be mapped to determine the drive range of the glow plug with good responsiveness. In particular, it is possible to determine with good responsiveness a drive range such as low load and low rotation where the engine speed is equal to or lower than a predetermined speed and the accelerator opening is equal to or lower than a predetermined opening, and the glow plug is driven with good responsiveness during engine operation. You can take measures against misfire.
In the above description, the engine glow plug control device is provided in the diesel engine 1, but it is also applicable to other compression ignition engines, for example, compression ignition type methanol engine.

[0029]

According to the first aspect of the present invention, a glow plug is installed in the combustion chamber to detect the excess air ratio of the exhaust system of the engine by the oxygen sensor and raise the temperature of the fuel supplied to the combustion chamber to promote combustion. Since the control means energizes the glow plug when the excess air ratio detected by the oxygen sensor is smaller than the predetermined value, the glow plug is operated during operation in which the excess air ratio is smaller than the predetermined value and can be regarded as a misfire. To drive.
For this reason, it is possible to improve the startability with good responsiveness during the operation that can be regarded as a misfire.

According to a second aspect of the present invention, in the engine glow plug control device according to the first aspect, particularly, the excess air ratio detected by the oxygen sensor by the control means is larger than a predetermined value and the predetermined engine speed. Since the glow plug is energized below and below the predetermined accelerator opening, the glow plug is driven during an operation in which the excess air ratio is smaller than a predetermined value and the engine is surely regarded as a misfire such as at low rotation and low load. . For this reason, it is possible to improve the startability with good responsiveness during the operation that can be surely regarded as a misfire.

According to the third and fourth aspects of the present invention, an oxygen sensor detects the excess intake ratio of the exhaust system of the engine, and the glow plug for increasing the temperature of the fuel supplied to the combustion chamber to promote combustion is used. The engine speed detecting means detects the engine speed, the accelerator opening detecting means detects the accelerator opening, and the controlling means detects the engine speed and the accelerator opening prior to the excess air ratio. Since the glow plug is energized in accordance with both outputs, the energization amount according to the engine speed and the accelerator opening can be mapped to determine the drive range of the glow plug with good responsiveness. In particular, the control means is capable of responsively determining a drive range such as a low load / low rotation in which the engine speed is equal to or lower than a predetermined speed and the accelerator opening is equal to or lower than a predetermined opening. Therefore, the glow plug can be driven with good responsiveness when the engine is operating, and measures against misfire can be taken.

According to a fifth aspect of the present invention, in the glow plug control device for a diesel engine according to any of the second and third aspects, in particular, the control means continues energization for a predetermined period after energizing the glow plug. To do. Therefore, the startability can be stabilized by energization for a predetermined period after energization, and disconnection / connection hunting after energization can be prevented.

According to a sixth aspect of the present invention, a glow plug that raises the temperature of the fuel supplied to the combustion chamber to promote combustion is provided in the combustion chamber, and the misfire detection means detects misfire of the engine and controls it. According to the misfire detection output of the misfire detection means, the glow plug is energized for a predetermined time, so that the glow plug is driven at the time of operation which can be regarded as misfire. For this reason, it is possible to improve the startability with good responsiveness during the operation that can be regarded as a misfire.

According to a seventh aspect of the present invention, in the glow plug control device for a diesel engine according to any of the first and sixth aspects, in particular, a cooling water temperature detecting means for detecting the cooling water temperature of the engine is further provided. The control means can always energize the glow plug when the cooling water temperature is lower than a predetermined value. For this reason, the glow plug can be reliably driven at low temperatures where the possibility of misfire is relatively high, and measures against misfire can be taken.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a glow plug control device for an engine as a first embodiment of the present invention.

FIG. 2 is a characteristic diagram of a glow plug drive range calculation map used in the glow plug control device of FIG.

FIG. 3 is a characteristic diagram of a glow plug drive range calculation map as a modified example used in the glow plug control device of FIG.

FIG. 4 is a characteristic diagram of a glow temperature of a glow plug used in the glow plug control device of FIG.

5 is a resistance-temperature characteristic diagram of a glow plug used in the glow plug control device of FIG.

6 is a flowchart of a glow plug control program used by the control unit of the glow plug control device in FIG.

[Explanation of symbols]

 1 Engine 5 Glow Plug 7 Fuel Injection Pump 8 Glow Plug Drive Circuit 13 λ Sensor 14 Control Unit 17 Engine Rotation Sensor 18 Load Sensor 19 Water Temperature Sensor Δt Glow-Electrification Time λ Air Excess Ratio λ1 Predetermined Value m-1 Glow Plug Drive Range Calculation Map C Combustion chamber M1 Low rotation and low load range Ne Engine speed LPS Accelerator opening Tw Engine water temperature Tw Cooling water temperature Te Predetermined period after energization Tg Temperature rising time ER Exhaust system

Claims (7)

[Claims] 1. An oxygen sensor provided in an exhaust system of an engine for detecting an excess air ratio, and a glow plug arranged in a combustion chamber of the engine for increasing a temperature of fuel supplied to the combustion chamber to promote combustion. A control means for energizing the glow plug when the excess air ratio detected by the oxygen sensor is smaller than a predetermined value. 2. The engine glow plug control device according to claim 1, wherein the control means is such that the excess air ratio detected by the oxygen sensor is greater than a predetermined value and less than or equal to a predetermined engine speed and a predetermined accelerator opening degree. A glow plug control device for an engine, wherein the glow plug is energized when: 3. An oxygen sensor provided in an exhaust system of an engine for detecting an excess air ratio, and a glow plug arranged in a combustion chamber of the engine for increasing a temperature of fuel supplied to the combustion chamber to promote combustion. , Engine speed detecting means for detecting the engine speed, accelerator opening detecting means for detecting the accelerator opening, and prior to the excess air ratio, depending on both outputs of the engine speed and the accelerator opening. A glow plug control device for an engine, comprising: a control means for energizing the glow plug. 4. The engine glow plug control device according to claim 3, wherein the control means energizes the glow plug when the engine speed is equal to or lower than a predetermined speed and the accelerator opening is equal to or lower than a predetermined opening. A glow plug control device for an engine, which is characterized in that: 5. The engine glow plug control device according to any one of claims 1 to 4, wherein the control means continues energization for a predetermined period after energization of the glow plug. Glow plug control device. 6. A glow plug which is arranged in a combustion chamber of an engine to raise the temperature of fuel supplied to the combustion chamber to promote combustion, a misfire detecting means for detecting misfire of the engine, and a misfire detecting means. A glow plug control device for an engine, comprising: a control unit that energizes the glow plug for a predetermined time in accordance with a detection signal. 7. The glow plug control device for an engine according to claim 1, further comprising a cooling water temperature detecting means for detecting a cooling water temperature of the engine, wherein the control means comprises the cooling means. A glow plug control device for an engine, wherein the glow plug is energized at all times when the cooling water temperature detected by the water temperature detecting means is lower than a predetermined value.