JP3134712B2 - Control device for glow plug for methanol engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glow plug control device for assisting ignition of an internal combustion engine employing a compression ignition system, and more particularly to a glow for a methanol engine suitable for a diesel engine type methanol engine which compresses and ignites methanol fuel. The present invention relates to a plug control device.

[0002]

2. Description of the Related Art An internal combustion engine employing a compression ignition system, particularly a diesel engine type methanol engine using methanol fuel, has a glow plug for heating fuel particles in a fuel spray region where fuel particles from an injector scatter. , Which ensures ignitability. This kind of methanol engine, when cold start,
If the exhaust gas temperature is low, the activation of the oxidation catalyst is delayed, and the emission of formaldehyde and HC tends to increase.
Since the combustion chamber temperature is relatively low even after warm-up, it is first necessary to ensure ignitability, and ignition assistance by a glow plug is important. The glow plug assists the ignition by constantly applying a constant voltage when the engine key is turned on, but this may result in waste of power supply.

[0003] As a glow plug control device for a constantly energized methanol engine in order to reduce such waste, for example, there is one shown in FIG. The glow plug control device includes a switch transistor 103 disposed between a glow plug 100 and a power supply 102, and incorporates the glow plug 100 into a Wheatstone bridge circuit 104.
Reference voltage point 105 in Wheatstone bridge circuit 104
The comparator 107 detects the voltage difference between the voltage and the applied voltage point 106 of the glow plug 100, and applies the output of the comparator 107 to the switch transistor 103. In addition,
Reference numeral 108 denotes a sensing register for temperature correction,
Symbols 109 and 110 are voltage dividing resistors.

[0004] As shown in FIG.
Is almost proportional to the increase in the resistance value of the glow plug 100. For this reason, the reference voltage point 105
The switch transistor 103 is set to be turned on at a lower applied voltage point 106, and when the temperature of the glow plug 100 rises excessively, the resistance increases, and the applied voltage point 106 becomes higher than the reference voltage point 105. 10
7 generates an off output, closes the switch transistor 103, cuts off the current supply, and thereby keeps the temperature of the glow plug 100 constant. On the other hand, JP-A-59-
No. 54774 discloses that a semiconductor switch is arranged between a power supply and a glow plug, and the intermittent ratio of the semiconductor switch is changed in relation to the engine temperature so that the power supplied to the glow plug becomes a necessary and sufficient value. What controls is disclosed.

[0005]

However, in the case of the glow plug control device shown in FIG. 14, the control is performed on the assumption that the resistance of the glow plug 100 increases in proportion to the temperature. For this reason, when the glow plug itself is deteriorated with time or affected by a harness resistance or contact resistance other than the plug as a disturbance, the resistance is increased even though the temperature is not increased, and the power supplied to the glow plug is reduced. I will. In such a situation, there is a problem that the glow plug of the engine cannot maintain a required temperature, and sufficient ignition assistance is not provided. On the other hand, JP-A-59-54774 discloses that a semiconductor switch is arranged between a power supply and a glow plug, and the intermittent ratio of the semiconductor switch is changed in relation to the engine temperature.
Japanese Patent Application Laid-Open No. H11-157556 discloses a technique that controls the power supplied to a glow plug to a necessary and sufficient value. Also in this case, there is a problem that the engine temperature sensor and its harness resistance, contact resistance, and the like are susceptible to disturbances, and sufficient ignition assistance is not performed.

[0006] In addition to the influence of the harness resistance and contact resistance of the glow plug, the ignition assist is not available in some cylinders at a preset glow plug temperature due to the operating condition of the vehicle and the influence of the outside air temperature. It was enough to cause a misfire.

[0007] When the ignition assist of the glow plug becomes unstable or insufficient as described above, and the engine misfires intermittently, it is necessary to perform the ignition assistance capable of avoiding the misfire with good responsiveness. Improvement is desired.

A first object of the present invention is to provide a reliable control of a glow plug for a methanol engine which can sufficiently secure ignitability at the time of engine operation, can eliminate erroneous control due to disturbance, and also has excellent transient response characteristics. It is to provide a device.

A second object of the present invention is to provide a control device for a glow plug for a methanol engine, which is capable of performing ignition assistance capable of avoiding misfire during unstable combustion such as engine misfire with good responsiveness.

[0010]

In order to achieve the above object, the present invention is directed to a glow plug provided in a cylinder head of an engine and interposed in a fuel injection region injected from a fuel injection valve. Glow plug temperature detecting means for detecting the temperature of the glow plug, operating state detecting means for detecting an operating state of the engine, and a first control value for storing supply power with the glow plug as a target temperature as a first control value.
A power supply map, a second power supply map storing the power supplied to the glow plug corresponding to the operation state detected by the operation state detection means as a second control value, and the second power supply map obtained by the first power supply map. A control value comparison unit that compares a first control value with the second control value obtained from the second power supply map, wherein the control value comparison unit determines that the first control value is equal to or greater than the second control value A first temperature control unit that controls power supply of the glow plug based on the first control value when it is performed, and controls power supply of the glow plug based on the second control value otherwise. It is characterized by having.

According to the first aspect of the present invention, the glow plug temperature detecting means detects a resistance of the glow plug, and a resistance value detected by the resistance sensor and a correlation between a temperature and the resistance of the glow plug. The temperature of the glow plug may be detected based on the relationship.

According to a second aspect of the present invention, in the control device for a glow plug for a methanol engine according to the first aspect, the operating state detecting means includes a rotation sensor for detecting at least the number of revolutions of the engine. The power supply map is characterized in that the second control value is set corresponding to at least the number of rotations detected by the rotation sensor.

[0013]

[0014]

[0015]

[0016]

[0017]

[0018]

[0019]

[0020]

[0021]

According to the first aspect of the present invention, there is provided a glow plug provided in a cylinder head of an engine and interposed in a fuel injection region injected from a fuel injection valve, a glow plug temperature detecting means for detecting a temperature of the glow plug, and an engine. operating condition detecting means for detecting the operating state, a first power supply maps for storing the electric power supplied to the glow plug with the target temperature as the first control value, glow corresponding to the operation state detected by the operating condition detecting means A second power supply map that stores the power supplied to the plug as a second control value is compared with a first control value obtained from the first power supply map and a second control value obtained from the second power supply map. And a control value comparison unit that performs the first control value when the control value comparison unit determines that the first control value is equal to or greater than the second control value. Hazuki controls power supply of the glow plug, when other than the controls the power supply of the glow plug based on the second control value. Therefore, a relatively high level of electric power can be supplied to the glow plug.

According to the first aspect of the present invention, the glow plug temperature detecting means detects the resistance of the glow plug and a resistance value detected by the resistance sensor and a correlation between the temperature and the resistance of the glow plug. When the temperature of the glow plug is detected, the temperature of the glow plug can be detected relatively easily.

According to a second aspect of the present invention, in the control device for a glow plug for a methanol engine according to the first aspect, the operating state detecting means includes a rotation sensor for detecting at least the engine speed, and the second power supply map. Is set corresponding to at least the number of rotations detected by the rotation sensor, so that the second control value can be obtained relatively easily.

[0024]

[0025]

[0026]

[0027]

[0028]

[0029]

[0030]

[0031]

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A control device Ma of a glow plug for a methanol engine shown in FIG. 1 is mounted on an in-line four-cylinder methanol engine (hereinafter simply referred to as engine) 1. Here, the first cylinder will be mainly described since each cylinder has the same configuration. Here, the engine 1 is provided with a combustion chamber C for each cylinder, and the combustion chamber C is variably configured by a cylinder block 2, a cylinder head 3, and a piston 4 that slides in the cylinder block. A fuel injection valve 5 and a glow plug 6 are mounted on the cylinder head 3, and both of them are disposed to face the combustion chamber C. Here, the fuel injection valve 5 is connected to a fuel injection pump 7, and the glow plug 6 is connected to a glow plug control circuit 8.

On the other hand, an intake passage IR of the engine 1 is formed by an intake pipe 9 connected to the cylinder head 3 and an air cleaner (not shown) provided at the tip end of the pipe. 11 and a muffler (not shown). An intake throttle valve 12 is provided in the middle of the intake pipe 9 and can maintain the intake passage IR at a predetermined opening between a fully closed state and a fully opened state. The intake throttle valve 12 is connected to an air switching means 13 having an actuator (not shown) having an actuator capable of adjusting a valve opening degree in a stepwise manner. The air switching means 13 is connected to a controller 14 as a control means for outputting a control signal for switching the valve opening.

The oxidation catalyst 11, which is the main exhaust gas purification device provided in the exhaust system, has a sufficient capacity to reliably purify the exhaust of the engine in a steady state. It is to be noted that the oxidation catalyst 11 requires a predetermined time to complete activation at the time of startup. Therefore, a warm-up catalyst (not shown) having a small capacity is provided upstream of the oxidation catalyst 11, and the warm-up catalyst is configured to purify exhaust gas until the activation of the oxidation catalyst 11 is completed.

A second temperature sensor 15 which is a main part of the exhaust gas temperature detecting means is provided on the upstream side of the oxidation catalyst 11 and a first temperature sensor 16 is provided on the downstream side thereof.
To the controller 14, and the controller 14 supplies the second and first exhaust temperature T
_ex2, T _ex1 can output a signal. The fuel injection pump 7 for supplying fuel to the fuel injection valve 5 is connected to the controller 14,
The fuel injection amount and the injection timing are controlled. As shown in FIGS. 1 and 3, a glow plug drive circuit 8 and a controller 14 are connected to the glow plug 6.

As shown in FIG. 3, the glow plug drive circuit 8 has a configuration in which the glow plug 6 and the power supply B are connected, and a switch transistor 801 and a resistance sensor 802 for detecting the resistance of the glow plug 6 are connected in series. take. Note that the resistance sensor 802 has a function as glow plug temperature detection means for detecting the temperature of the glow plug. The resistance sensor 802 includes a Wheatstone bridge circuit, in which a reference voltage point p1 and an applied voltage point p2 are provided.
Is connected to the comparator 803, and the output terminal of the comparator 803 is connected to the controller 14.

Here, the comparator 803 calculates the voltage Vn at the applied voltage point p2 of the glow plug 6 and the voltage Vb at the reference voltage point p1.
And outputs an output Δv to the controller 14. Switch transistor 801
Has a target control value τ as a duty signal.
When o is input from the controller 14, the current I supplied to the glow plug 6 is intermittently controlled to control the power value. FIG.
Reference numeral 804 denotes a sensing register for temperature correction, and reference numerals 805 and 806 denote voltage dividing resistors.

The main part of the controller 14 shown in FIG. 1 is constituted by a microcomputer, and an RO (not shown)
In M, a flowchart of a glow plug control program described later (see FIG. 7), various maps, and set values are stored and processed. A predetermined reference voltage is applied to the controller 14 from a power supply B. Further, in addition to the above-described resistance sensor 802, an input / output circuit (not shown) serves as operating state detecting means for detecting operating state information of the engine. An engine rotation sensor 17 for detecting an engine speed Ne, a load sensor 18 for detecting a load L which is a lever opening degree of a fuel injection pump 7 (not shown), a key sensor 19 for outputting a key signal Sk of an engine key, and an engine water temperature Tw. The water temperature sensor 20, the second temperature sensor 15, and the first temperature sensor 16 described above are connected to each other.

Here, the controller 14 of FIG. 1 has the following functions. That is, the controller 14 of FIG.
Glow plug temperature detecting means 14a, operating state detecting means 14b for detecting an operating state of the engine in cooperation with the above-described sensors, a first power supply map m1 (see FIG. 6),
It has a second power supply map m2 (see FIG. 4), a control value comparison unit 14c, and each function as a first temperature control unit 14d (see the functional block in FIG. 2).

Here, the glow plug temperature detecting means 14a
Detects the resistance Rg of the glow plug by the resistance sensor 802. In this case, the above-described voltage difference Δv (= Vn−V
b), the current value In (the current value is calculated as τ × i from the current duty ratio% τ and the coefficient i) is determined, and the current value In is calculated from Δv and In along the resistance value calculation map m3 in FIG. The resistance of the glow plug 6, for example, the resistance Rg
1 and 2 are calculated. Further, the first power supply map m in FIG.
Along with 1, a first control value τ1 corresponding to the current resistance Rg is calculated.

The first power supply map m1 (not shown) is
The glow plug 6 is set to the target temperature Tgo (the same temperature and the resistance value Rg).
is stored as the first control value τ1. That is, the first control value τ1 is the current resistance value Rg
Can be corrected to a predetermined value Rgo (the temperature of the glow plug corresponding to this resistance value is set in advance as an appropriate temperature). Here, the first control value τ1 is a time width (duty ratio) for intermittently regulating the current flowing through the glow plug 6 receiving the applied voltage of the power supply B, and the larger the value (duty ratio%), the larger the current. I increases.

The second power supply map m2 stores the power supplied to the glow plug corresponding to the operating state with the engine speed Ne and the load L as a second control value τ2 (duty ratio). As shown in FIG. 4, the second control value τ2 is preset according to the engine speed Ne and the engine load L, and can be calculated from the current engine speed Ne and the engine load L. The second control value τ2 is set so as to increase as the rotation speed increases. The control value comparison unit 14c compares the magnitude of the first control value τ1 determined by the first power supply map m1 with the magnitude of the second control value τ2 determined by the second power supply map m2.

The first temperature control means 14d includes the control value comparing section 1
4a, when it is determined that the first control value τ1 is equal to or greater than the second control value τ2, the power supply of the glow plug 6 is controlled based on the first control value τ1, and otherwise, the power is reduced to the second control value τ2. The power supply of the glow plug is controlled based on the glow plug. Here, the operation of the present apparatus will be described with reference to the flowchart of the glow plug control program in FIG. The controller 14 enters the control of a main routine (not shown) by inputting a key-on signal, and reaches a glow plug control program at a predetermined time. In step s1, Δv (= Vn−V
b), a current value In (= τ × i) is obtained, and Δv and In
The resistance Rg of the glow plug 6 is calculated along the resistance value calculation map m3 of FIG. 5, and then the first power supply map m
Along with 1, a first control value τ1 corresponding to the resistance Rg is set.

In step s2, the engine speed Ne and the load L are fetched, and Ne, Ne along the τ2 calculation map m2.
The second intermittent signal τ2 corresponding to L is calculated. In steps s3 to s5, the magnitude of the first control value τ1 is compared with the magnitude of the second control value τ2. If τ2 ≧ τ1, the target control value τo is set to the second control value τ2. One control value is τ1. Thereafter, when the process reaches step s6, the switch transistor 801 is driven based on the target control value τo at this time, the amount of current supplied to the glow plug 6 is adjusted, and the process returns to the main routine (not shown).

As described above, the control apparatus for the glow plug for the methanol engine shown in FIG. 1 obtains the second control value τ2 corresponding to the first control value τ1 and the rotation speed Ne detected by the engine rotation sensor 17, and obtains the second control value τ2. The actual temperature of the glow plug obtained by the resistance sensor 802 can be adjusted to the target temperature Tgo by setting a large value in the above as the target value. For this reason, reliable ignition assistance can be performed when necessary, reliability against misfires is improved,
In addition, the second control value can be obtained relatively easily, and the configuration of the device can be simplified. FIG. 8 shows functional blocks of a control device Mb for a glow plug for a methanol engine according to a second embodiment of the present invention. Here, the control device Mb for the glow plug for the methanol engine includes a large number of the same members except for the control configuration different from the control device Ma for the glow plug for the methanol engine in FIG. Are denoted by the same reference numerals, and redundant description is omitted.

Here, in the control device Mb of the glow plug for the methanol engine, the controller 14b has the following functions instead of the controller 14 of FIG. That is, the controller 14b of FIG. 8 includes a glow plug temperature detecting unit 14a, an operating state detecting unit 14b that detects an operating state of the engine in cooperation with the above-described sensors, a first power supply map m1, and a second power supply map m1. The power supply map m2, the control value comparison unit 14c, the first temperature control unit 14d, the warm-up completion determination unit 14e, the engine combustion state detection unit 14f, the misfire determination unit 14g, and the second temperature control unit 14h Each function is provided.

Here, in particular, the warm-up completion determining means 14e determines warm-up completion based on the engine temperature (warm-up completion temperature Tw1) of the engine. Engine combustion state detecting means 14
f detects unstable combustion of the engine. Misfire determination unit 14
g basically determines the engine misfire state based on the combustion state detected by the engine combustion state detection unit 14f after the warm-up completion determination unit 14e determines that the warm-up is completed.

In this case, in particular, the misfire determination section 14g determines the catalyst temperature of the catalyst 11 inserted in the exhaust passage ER of the engine,
Or an exhaust temperature detecting means including a first temperature sensor 16 for detecting a downstream exhaust temperature on the downstream side thereof, wherein one of the catalyst temperature or the downstream exhaust temperature detected by the first temperature sensor and an operating state detecting means The first exhaust gas temperature comparing section 14g-a first exhaust gas temperature comparing section 14g-
When the temperature exceeds the first reference temperature, it is determined that the engine is misfired. In addition, the exhaust temperature detecting means detects an upstream exhaust temperature on the upstream side of the catalyst, a second temperature sensor, and one of the catalyst temperature or the downstream exhaust temperature detected by the first temperature sensor 16 and a second temperature. A deviation from the upstream exhaust gas temperature detected by the sensor 15 is calculated, and the deviation is calculated by the second exhaust gas temperature comparing section 14g-2 and the second reference temperature based on the operating state detected by the operating state detecting means 14b. If the difference exceeds the second reference temperature, it is determined that the engine is misfired. Here, the first and second reference temperatures are set respectively based on the engine speed Ne and the load L detected by the operating state detecting means 14b.

The second temperature control means 14h includes a misfire determination section 14
g, when it is determined that the engine is in a misfire state,
First control value τ obtained from first power supply map m1
1 is increased by a predetermined amount to control the power supply of the glow plug.

The operation of the control device Mb will now be described with reference to the flowchart of the glow plug control program shown in FIG. The controller 14b enters control of a main routine (not shown) by inputting a key-on signal, and reaches a glow plug control program at a predetermined time. Step a1, a
In FIG. 2, Δv and In are obtained, and based on these values, FIGS.
Of the glow plug 6 along the resistance calculation map m3 of FIG.
g is calculated, and then a first control value τ1 corresponding to the resistance Rg is set along the first power supply map m1. Furthermore,
According to the second power supply calculation map m2, the engine speed N
e and the second control value τ2 corresponding to the load L is calculated.

In steps a3 to a5, the first control value τ
1 and the second control value τ2, and sets the target control value τo to τ2
If ≧ τ1, the second control value is τ2, and if τ2 <τ1, the first control value is τ1. Thereafter, when the process reaches step a6, it is determined here whether or not the engine coolant temperature Tw has exceeded the warm-up completion temperature Tw1, and if not, the process proceeds to step a11. When the process reaches steps a7 and a8 after the warm-up, the first temperature sensor 16 detects the first exhaust temperature T _ex1 on the downstream side of the exhaust path of the catalyst 11 and is set in advance according to the current engine speed Ne and the load L. It is determined whether or not the first exhaust temperature _Tex1 exceeds the abnormal exhaust temperature T2. As a result, over the (T _ex2 ≧ T2), the temperature difference (T _ex2 -T _ex1) equivalent of the current supply amount of the bulking f (T _ex2 -T _ex1) fixes, at this point, with respect to the target control value τo The modified target control value τo is obtained by the following equation (1).

[0052] _{τo = τo + f (T ex2} -T ex1) ······· (1) On the other hand, the exhaust gas temperature T2 is the first exhaust temperature T _ex1 below (T
_ex1 <T2), the process directly proceeds to step a9.

Steps a7 and a8 show the function as the engine combustion state detecting means 14f. Here, unburned HC is generated in the combustion chamber C and flows to the exhaust pipe 10 side. When the HC is combusted there, the temperature in the exhaust path becomes abnormally high and exceeds a predetermined abnormal exhaust temperature T2. It will be. Such a situation may be caused by unstable combustion,
Often occurs during a misfire. In this case, when the current is supplied to the glow plug 6 in step a11 described later, the increased current is supplied. Step a9, a10
Then, the second temperature sensor 15 detects the exhaust temperature T _ex2 on the upstream side of the exhaust path of the catalyst 11, and the first temperature sensor 16 detects the first exhaust temperature T _ex1 on the downstream side of the exhaust path of the catalyst 11. It is determined whether the current second and first exhaust gas temperature differences ΔT (= T _ex2 −T _ex1 ) exceed an abnormal exhaust gas temperature difference ΔTex preset according to the engine speed Ne and the load L (FIG. 10). reference).

As a result, when (T ≧ ΔTex) is exceeded,
The correction of the increase in the current supply amount corresponding to the current second and first exhaust gas temperature difference ΔT is performed on the target control value τo at this time as in the following equation (2), and the corrected target control value τo is corrected. And if it falls below (T _ex2 <T2), step a1
Proceed to 1.

Τo = τo + f (ΔT) (2) Here, the ignitability in the combustion chamber C is reduced, a misfire occurs, and the untwisted gas reaches the oxidation catalyst 11, where As a result of the combustion, ΔT increases, and exceeds a preset abnormal post-exhaust gas temperature difference ΔTex. In such a situation, in order to respond to misfire with good responsiveness,
By increasing the amount of current supply corresponding to the exhaust gas temperature difference ΔT,
When the current is supplied to the glow plug 6 in step a11 described later, the increased current is supplied. Thereafter, the process reaches step a11. Here, the switch transistor 801 is determined based on the target control value τo at this time.
To adjust the amount of current supplied to the glow plug 6, and returns to the main routine (not shown).

As described above, the control device Mb for the glow plug for the methanol engine shown in FIG.
Although step a11 was configured to be able to be executed continuously, instead of this, as a modified example of the control device Mb of the glow plug for the methanol engine, control consisting of step a1 and step a6 to step a11 is simply performed. May be configured. Further, it may be configured to simply perform the control consisting of step a2 and step a6 to step a11. In these cases as well, a simplified glow plug control device can be performed only for control after warm-up, and the device can be simplified.

As described above, the control device Mb for the glow plug for the methanol engine has its misfire determination section 14.
g is determined to be the completion of warm-up by the warm-up completion determining means 14e, and then the engine misfire state is determined based on the combustion state detected by the engine combustion state detecting means 14f. Instead, the controller 1
4 ′, as shown in FIG. 11, steps a2, a5 ′,
a6, a9 'to a11 may be configured to be executed. In the case of this modification, a misfire determination unit (not shown) has a cylinder pressure sensor (indicated by a two-dot chain line Sp in FIG. 1) that detects the pressure in the combustion chamber C of the engine.
The in-cylinder pressure Pc detected by the in-cylinder pressure sensor Sp is:
The engine misfire may be determined when the reference pressure Pcα based on the operation state detected by the operation state detection means 14b is less than the reference pressure Pcα.

Further, as shown in FIG. 12, the controller 14 'performs steps a2, a5 ", a6, a9" through a1.
1 may be executed. In the case of this modification, a misfire determination unit (not shown) 14g "has a rotation fluctuation sensor (means for calculating from a crank angle), and this is based on the cycle of each cylinder of the engine at every predetermined crank angle. Then, the rate of change (fluctuation component) of the engine rotation is detected, and the rotation fluctuation ΔNe component detected by the rotation fluctuation sensor (not shown) is used as the reference rotation based on the operation state detected by the operation state detection means 14b. The engine misfire may be determined when the variation ΔNeα is not reached.

Further, as shown in FIG. 13, the controller 14 'performs steps a2, a5 "', a6, a9"'to a
11 may be configured to be executed. In this modification, it has an O ₂ sensor (not shown) misfire determining unit misfire determining unit 14 g "'detects an oxygen concentration in the exhaust passage of the engine (indicated by a two-dot chain line S _{A / F} in FIG. 1), When the oxygen concentration A / Fn detected by the O ₂ sensor S _{A / F} exceeds the reference oxygen concentration A / Fb based on the operation state detected by the operation state detection means 14b, it may be determined that the engine is misfired. As described above, the control device Mb for the glow plug for the methanol engine includes the misfire determination unit 14g ', 14g ", 14g instead of the misfire determination unit 14g.
The same effects as those of the control device Mb for the glow plug for the methanol engine shown in FIG.

[0060]

According to the first aspect of the present invention, there is provided a glow plug provided in a cylinder head of an engine and interposed in a fuel injection region injected from a fuel injection valve, and a glow plug temperature detecting means for detecting a temperature of the glow plug. Operating state detecting means for detecting an operating state of the engine, and a first control value for storing a supply electric power having a glow plug as a target temperature as a first control value.
A power supply map, a second power supply map storing the power supplied to the glow plug corresponding to the operation state detected by the operation state detection means as a second control value, and a first power supply map obtained by the first power supply map. A control value comparison unit that compares the control value with a second control value obtained from the second power supply map, and in particular, the first temperature control unit determines that the first control value is equal to the second control value in the control value comparison unit. When it is determined that the value is equal to or more than the value, the power supply to the glow plug is controlled based on the first control value, and otherwise, the power supply to the glow plug is controlled based on the second control value. Therefore, a relatively high level of electric power can be supplied to the glow plug when necessary, and reliable ignition assistance can be performed when necessary, thereby improving the reliability against misfiring.

According to the first aspect of the present invention, the glow plug temperature detecting means detects the resistance of the glow plug and a resistance value detected by the resistance sensor and a correlation between the resistance and the temperature of the glow plug. In the case where the temperature of the glow plug is detected, the temperature of the glow plug can be detected relatively easily, the ignition can be reliably assisted when necessary, and the effect that the configuration of the device can be simplified is obtained. be able to.

According to a second aspect of the present invention, in the control device for a glow plug for a methanol engine according to the first aspect, the operating state detecting means includes a rotation sensor for detecting at least the engine speed, and the second power supply map. Is set at least in accordance with the number of rotations detected by the rotation sensor, so that the second control value can be obtained relatively easily, and reliable ignition assistance can be performed when necessary. Can be facilitated.

[0063]

[0064]

[0065]

[0066]

[0067]

[0068]

[0069]

[0070]

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a main part of a control device for a glow plug for a methanol engine as one embodiment of the present invention.

FIG. 2 is a functional block diagram of a control device for a glow plug for a methanol engine in FIG. 1;

3 is a schematic configuration diagram of a glow plug drive circuit used by the control device for a glow plug for a methanol engine in FIG. 1;

FIG. 4 is a characteristic diagram of a second power supply map used by the control device of FIG. 1;

FIG. 5 is a characteristic diagram of a resistance calculation map used by the control device of FIG. 1;

FIG. 6 is a characteristic diagram of a first power supply map used by the control device of FIG. 1;

FIG. 7 is a flowchart of a control program executed by the control device of FIG. 1;

FIG. 8 is a functional block diagram of a control device for a glow plug for a methanol engine as another embodiment of the present invention.

FIG. 9 is a flowchart of a control program executed by the control device of FIG. 8;

FIG. 10 is a Ne-exhaust temperature characteristic diagram showing a relationship between a preset abnormal second first exhaust gas temperature difference and a current second first exhaust gas temperature difference.

FIG. 11 is a flowchart of a control program used by the control device of FIG. 8 as a modification.

FIG. 12 is a flowchart of a control program used by the control device of FIG. 8 as a modification.

FIG. 13 is a flowchart of a control program used by the control device of FIG. 8 as a modification.

FIG. 14 is a schematic circuit diagram of a conventional glow plug control device for a methanol engine.

FIG. 15 is a resistance-temperature diagram of a glow plug. Reference Signs List 1 engine 5 fuel injection valve 6 glow plug 8 glow plug drive circuit 801 switch transistor 802 resistance sensor 11 oxidation catalyst 14 controller 14 'controller 14a glow plug temperature detecting means 14b operating state detecting means 14c control value comparing section 14d first temperature controlling means 14e Warm-up completion determination means 14f Engine combustion state detection means 14g Misfire determination section 14h Second temperature control means 14g-1 First exhaust temperature comparison section 14g-2 Second exhaust temperature comparison section 15 Second temperature sensor 16 First temperature sensor 17 engine rotation sensor 18 load sensor 19 key switch 20 water temperature sensor τ1 first control value τ2 second control value τo target control value m1 first power supply map m2 second power supply map Δv voltage difference B power supply C combustion chamber ER exhaust passage In Current value IR intake passage Ma control device Mb control device Tw Engine water temperature Rg Glow plug resistance

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) F02P 19/02 301 F02P 19/02 304 F02P 19/02 311 F02P 19/02 321 F02D 45/00 301

Claims (2)

(57) [Claims] 1. A glow plug provided in a cylinder head of an engine and interposed in a fuel injection region injected from a fuel injection valve, a glow plug temperature detecting means for detecting a temperature of the glow plug, and detecting an operating state of the engine. Operating state detecting means, a first power supply map storing supply power having the glow plug as a target temperature as a first control value, supply to the glow plug corresponding to an operating state detected by the operating state detecting means A second power supply map for storing power as a second control value; a control for comparing the first control value obtained from the first power supply map with the second control value obtained from the second power supply map A value comparing section, when the control value comparing section determines that the first control value is equal to or greater than the second control value, A first temperature control means for controlling the power supply of the glow plug, and controlling the power supply of the glow plug based on the second control value at other times than the above, and a glow plug for a methanol engine. Control device. 2. The engine according to claim 2, wherein the operating state detecting means includes a rotation sensor for detecting at least a rotation speed of the engine, and wherein the second control value of the second power supply map is at least a rotation speed detected by the rotation sensor. The control device for a glow plug for a methanol engine according to claim 1, wherein the control device is set in accordance with the following.