JP2001165434A - Vaporizing combustor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem that in an vaporizing combustor in which a combustion is started after a liquid fuel is vaporized, vapor fuel fed in a premixing chamber is condensed to be liquefied at a time of ignition action, and fuel supply to a catalytic combustion part in response to a requested combustion rate is made impossible. SOLUTION: Fuel is fed to a premixing chamber 14 in an amount more than a requested fuel amount suitable to ignition by a control of ECU 40 during the time from an ignition actuation to a combustion stabilization. Thereby even though an evaporated fuel is partly condensed in the chamber 14 and liquefied, the amount of the liquefied content is supplemented by correction of fuel increase. Thus vapor fuel in correspondence with the requested amount is fed to the catalytic combustion part 6, and air-fuel ratio is maintained appropriately, and further the degradation of the ignition performance can also be resolved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an evaporative combustion apparatus for evaporating liquefied fuel and burning the evaporated fuel.

[0002]

2. Description of the Related Art An evaporative combustion apparatus comprises a combustion section for burning evaporative fuel, evaporative fuel supply means for evaporating and supplying liquid fuel to a premixing chamber upstream of the combustion section, and an evaporative fuel supply section upstream of the combustion section. Air supply means for supplying air to the mixing chamber, wherein the heat obtained in the combustion section is used, for example, for heating a vehicle or for warming up a vehicle component.

[0003]

When the combustion in the combustion section is stabilized, the heat of combustion is transmitted to the premixing chamber and the like and becomes high temperature, so that the steam fuel supplied into the premixing chamber and the like is maintained as steam. Is done. However, at the time of ignition start, the inside of the premixing chamber to which the evaporated fuel is supplied has not reached an atmospheric temperature at which the evaporated fuel is maintained as vapor as it is. Therefore, at the time of ignition start, the vapor fuel supplied to the premixing chamber or the like condenses and liquefies again, and it becomes impossible to supply the vapor fuel corresponding to the required combustion amount to the combustion unit. If such a phenomenon occurs, an appropriate air-fuel ratio cannot be obtained at the time of ignition start, and a phenomenon that ignition performance is deteriorated may also be caused. If this problem is specifically described, for example, in the case of using a catalytic combustion section in which a catalyst is supported in the combustion section, an appropriate air-fuel ratio cannot be obtained due to liquefaction condensation, and a mixture having a fuel-lean air-fuel ratio becomes catalytic combustion. When supplied to the department
High temperature combustion occurs in the catalytic combustion section, and the life of the catalytic combustion section is degraded. In addition, the fuel-rich air-fuel ratio is easier to ignite at the time of ignition in both the catalytic combustion section and the burner combustion section that performs high-temperature combustion, but the ignition performance deteriorates when the fuel becomes lean due to liquefaction condensation. Resulting in.

[0004] On the other hand, when combustion is started upon ignition, the combustion heat is transmitted to a premixing chamber and the like. Then, the fuel condensed and liquefied in the premixing chamber or the like is re-evaporated. When such a phenomenon occurs, steam fuel re-evaporated in the premixing chamber or the like is supplied to the combustion section in addition to the steam fuel supplied from the premixing chamber. That is, in the initial stage of the combustion start, excessive evaporative fuel is supplied to the combustion part, so that an appropriate air-fuel ratio cannot be obtained, and problems such as deterioration of emission occur.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and a first object of the present invention is to provide a combustion unit that can supply steam fuel corresponding to a required combustion amount even if the steam fuel condenses and liquefies at the time of ignition start. Another object of the present invention is to provide an evaporative combustion apparatus capable of maintaining an appropriate air-fuel ratio. A second object of the present invention is to provide a combustion section in which fuel condensed and liquefied in a premixing chamber or the like is re-evaporated by combustion heat at an early stage of combustion. It is an object of the present invention to provide an evaporative combustion apparatus capable of maintaining an appropriate air-fuel ratio even when supplied to a combustion chamber.

[0006]

[Means for Solving the Problems] [Means for Claims 1 to 4]
According to the first to fourth aspects of the present invention, at the time of ignition start, fuel larger than the required combustion amount is supplied to the premixing chamber. With this arrangement, even when the vapor fuel supplied to the premixing chamber and the like condenses and liquefies at the time of ignition start, the liquefied component is supplemented by the increase control of the fuel, and the required combustion amount is required by the combustion unit. Is supplied, and the air-fuel ratio is maintained at an appropriate level. In addition, deterioration of the ignition performance can be eliminated by optimizing the air-fuel ratio.

[0007] According to the second aspect of the present invention, when the environmental temperature at the time of ignition start is low, the amount of fuel larger than the required combustion amount is further taken into consideration in consideration of the temperature difference at the time of normal temperature control. An increased amount of fuel may be provided to the premixing chamber. During a low temperature start, the amount of liquefaction in the premixing chamber or the like increases. Therefore, by adopting the second aspect of the present invention, the fuel vapor having increased the amount of liquefaction is supplied by the fuel vapor supply means. As a result, even at a low temperature start, steam fuel corresponding to the required combustion amount is supplied to the combustion section, so that the air-fuel ratio is maintained at an appropriate level, and the ignition performance is deteriorated due to the optimization of the air-fuel ratio. Can be resolved.

According to a third aspect of the present invention, in a region where combustion starts and fuel condensed and liquefied in a premixing chamber or the like re-evaporates due to combustion heat, the fuel supply to the evaporative fuel supply means is performed. The liquid fuel supply amount may be reduced, or the supply of the liquid fuel to the evaporative fuel supply means may be stopped. With this provision, in the region where the condensed and liquefied fuel is re-evaporated by the heat of combustion, the amount of the evaporated fuel is cut, and the combustion portion is supplied with the vapor fuel corresponding to the required combustion amount. . This keeps the air-fuel ratio at an appropriate level.

According to a fourth aspect of the present invention, in a region where combustion starts and fuel condensed and liquefied in a premixing chamber or the like re-evaporates due to heat of combustion, air is supplied by air supply means. It may be provided to increase the supply amount.
With this provision, in a region where the condensed and liquefied fuel is re-evaporated by the heat of combustion, the amount of air corresponding to the amount of evaporated fuel to be re-evaporated and supplied to the combustion part is increased and supplied. This keeps the air-fuel ratio at an appropriate level.

[Means of claim 5] In the invention of claim 5,
In the region where the combustion starts and the fuel condensed and liquefied in the premixing chamber or the like re-evaporates due to the heat of combustion, the supply amount of the liquid fuel to the evaporative fuel supply means is reduced, or the supply of the liquid fuel to the evaporative fuel supply means is reduced. It is provided to stop the supply. By providing in this manner, in the region where the condensed and liquefied fuel is re-evaporated by the heat of combustion, the amount of fuel vapor that is re-evaporated and supplied to the combustion unit is cut,
Steam fuel corresponding to the required combustion amount is supplied to the combustion section. This keeps the air-fuel ratio at an appropriate level.

[Means of Claim 6] In the invention of Claim 6,
In the region where the combustion is started and the fuel condensed and liquefied in the premixing chamber or the like is re-evaporated by the heat of combustion, the amount of air supplied by the air supply means is increased. With this provision, in a region where the condensed and liquefied fuel is re-evaporated by the heat of combustion, the amount of air corresponding to the amount of evaporated fuel to be re-evaporated and supplied to the combustion part is increased and supplied. This keeps the air-fuel ratio at an appropriate level.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] FIGS. 1 to 5 show a first embodiment. First, a hot water heating apparatus using an evaporative combustion apparatus will be described with reference to FIG. The upper side in the embodiment indicates the upper side in FIG. 3, and the lower side indicates the lower side in FIG.

The hot water heating apparatus shown in this embodiment employs a multi-pipe structure, and includes a combustion tube 1, an exhaust tube 2, and a hot water tube 3 from the inside. The combustion cylinder 1 is a cylinder that internally burns fuel, and the exhaust cylinder 2 is a cylinder that forms an annular combustion gas passage 4 between the combustion cylinder 1 and an outer air guide cylinder 9 described below. The tube 3 is a tube that forms an annular hot water passage 5 with the exhaust tube 2.

The combustion cylinder 1 is a cylinder made of a heat-resistant metal (stainless steel or the like) composed of an upper (fuel supply side) small diameter cylinder 1a and a lower (combustion gas discharge side) large diameter cylinder 1b. The diameter of the small-diameter cylinder 1a and the large-diameter cylinder 1b changes via the step portion 1c. Inside the small-diameter cylinder 1a, a catalytic combustion unit 6 and a fuel evaporating unit 7 are arranged. Around the small-diameter cylinder 1a slightly lower than the catalytic combustion unit 6 and the fuel evaporating unit 7,
A plurality of secondary air outlets 8 for allowing secondary air to flow into the combustion cylinder 1 are formed.

A large-diameter cylinder 1b is provided around the small-diameter cylinder 1a.
A double cylinder comprising an outer air guide cylinder 9 having the same diameter as the inner air guide cylinder 11 and an inner air guide cylinder 11 having a diameter slightly larger than the small diameter cylinder 1a is arranged. The outer air supply passage 10 between the outer air guide tube 9 and the inner air guide tube 11 is provided with a turn portion 12 on the upper side of the step portion 1c while exchanging heat supplied from above with the combustion gas.
Lead to. The inner air supply passage 13 between the inner air guide cylinder 11 and the small-diameter cylinder 1a has a turn portion 12
The air that has been turned in is guided upward.

Here, the inside air supply passage 13
1 for guiding air to the premixing chamber 14 above the next air outlet 8
The secondary air supply passage 15 corresponds to primary air supply means. The amount of air supplied to the premixing chamber 14 is adjusted so as to have an air-fuel ratio (an air-fuel ratio lower than the stoichiometric air-fuel ratio) at which the amount of fuel supplied becomes excessive with respect to the amount of fuel supplied to the premixing chamber 14. Things.

On the other hand, the secondary air outlet 8 is
Corresponds to secondary air supply means for supplying secondary air necessary for completely burning unburned fuel into the combustion completion chamber 16 on the downstream side of the combustion chamber. The amount of supplied air is adjusted to be an air-fuel ratio (higher than the stoichiometric air-fuel ratio) necessary to completely burn unburned fuel. In this embodiment, the premixing chamber 1
The ratio between the primary air supplied to the combustion chamber 4 and the secondary air supplied from the secondary air outlet 8 into the combustion cylinder 1 is set to about 1: 2.

The exhaust pipe 2 is a closed-end cylindrical body whose lower side (downstream of exhaust gas) is closed, and has a gas heat transfer fin 17 formed on the inner surface for transmitting the heat of the combustion gas to the exhaust pipe 2. A water-side heat transfer fin 18 for guiding the hot water passage 5 in a spiral shape is formed on the outer surface. An exhaust pipe exhaust hole 19 for discharging the combustion gas guided upward by the combustion gas passage 4 to the outside is formed at the upstream end of the exhaust pipe 2.

The hot water cylinder 3 is, like the exhaust pipe 2, a bottomed cylindrical body in which the lower side of the combustion pipe 1 is closed, and has a hot water pipe exhaust hole 20 communicating with the exhaust pipe exhaust hole 19 of the exhaust pipe 2. I have. A hot water inlet 21 that guides hot water to the hot water passage 5 is formed below the hot water cylinder 3, and a hot water outlet 22 that guides hot water to the outside is formed above the hot water cylinder 3.

The upper sides of the premixing chamber 14, the exhaust pipe 2, and the hot water pipe 3 are closed by an end plate 23. An air pump 24 (corresponding to an air supply means) is provided outside the end plate 23.
An air inflow cylinder 26 through which air for combustion is supplied via an air inflow port 25 is mounted, and the air supplied into the air inflow cylinder 26 is supplied to an air supply tube formed in the end plate 23. It is led to the outside air supply passage 10 through the hole 27.

On the other hand, inside the end plate 23, a fuel evaporating means 7 extending into the small-diameter cylinder 1a of the combustion cylinder 1 is attached. The fuel evaporator 7 constitutes an evaporative fuel supply unit together with a fuel pump 34 described later.
The fuel evaporating means 7 evaporates the liquid fuel by heat and then guides the liquid fuel to the premixing chamber 14 upstream of the catalytic combustion unit 6. The fuel evaporating means 7 is connected to the end plate 23 via a plurality of insulating materials 28 a and 28 b. A central electrode tube 29 to be attached; an evaporating cylinder 30 receiving supply of liquid fuel from the central electrode tube 29 and insulated and held by the central electrode tube 29 via an insulating material 28c; An evaporation heater 31 that generates heat when energized from the center electrode tube 29 is provided. In addition, the center electrode tube 29 has a flow path 29a through which liquid fuel passes at the center.

The lower end of the evaporation cylinder 30 is a closed end surface 30a facing the inside of the combustion cylinder 1, and the upper side of the evaporation cylinder 30 has
Fuel injection hole 3 for guiding fuel evaporated inside to premixing chamber 14
2 are provided. The evaporating cylinder 30 is grounded via the catalytic combustion section 6, the combustion cylinder 1, and the like. When a voltage is applied to the center electrode tube 29, the evaporating heater 31 is energized together with the catalytic combustion section 6. .

A liquid fuel (eg, light oil) stored in a fuel tank 33 is provided at the upper open end of the flow path 29 a of the center electrode tube 29 so as to be supplied by a fuel pump 34. The lower open end of the flow path 29 a of the center electrode tube 29 inside the evaporating cylinder 30 is closed end face 3 of the evaporating cylinder 30.
0a, and separated by a predetermined distance,
It is insulated from the evaporating cylinder 30. On the other hand, the center electrode tube 29 is provided so as to receive a voltage via the power supply terminal 35. The power supply terminal 35 is disposed so as to penetrate through the air inflow cylinder 26 via an insulating material 36, and is sandwiched by a plurality of fixing nuts 37a and 37b to hold the central electrode tube 29.
It is fixed to.

The evaporating heater 31 is provided in a substantially honeycomb shape having a large number of through-holes. As shown in FIG. 5A, for example, a current-carrying resistance made of a Fe—Cr—Al ferrite stainless steel is used. Heat generating flat plate 38a and corrugated plate 3
8b on the surface of a pair of metal foils (for example, 50 μm thick)
A thin insulating layer of alumina or the like is provided, and this is
It is provided by being wrapped around. The flat plate 38a
FIG. 4 (b) shows an outline of a honeycomb composed of a honeycomb and a corrugated plate 38b.

A catalytic combustion section 6 is arranged between the small-diameter cylinder 1a and the evaporation cylinder 30. The catalytic combustion unit 6 includes a catalyst (noble metal such as Pt, Pd, Rn, etc.) that promotes ignition combustion and a partial oxidation reaction on the surface of an energized heating element which is provided in a substantially honeycomb shape having a large number of through holes and generates heat by energization. N
i, metals such as Cu, oxides such as alumina and zirconia)
Is carried. Furthermore, a partial oxidation reaction is possible even if an oxide layer of alumina or the like forming the insulating layer is used as it is. Therefore, the catalyst refers to the metal and the oxide layer.

More specifically, as shown in FIG. 5B, for example, a pair of metal foils (for example, 50 μm thick) of a flat plate 38 a and a corrugated plate 38 b that generate heat by a current-carrying resistance made of, for example, Fe—Cr—Al ferritic stainless steel. ), A thin insulating layer such as alumina is provided on the surface, and a plurality of catalysts supporting Pt, Pd or the like are wound around the evaporating cylinder 30. The inside of the catalytic combustion section 6 is connected to the evaporating cylinder 30, and the outside is connected to the combustion cylinder 1 through the outer peripheral electrode 39. It is provided so as to generate heat.

The energization control of the evaporation heater 31 and the catalytic combustion section 6 and the energization control of the air pump 24 and the fuel pump 34 are performed by control means 40 (hereinafter, ECU). The ECU 40 operates in conjunction with the start of the engine or during the heating operation. The ECU 40 includes a water temperature sensor 42 for detecting the temperature of hot water in the hot water passage 5 and an exhaust gas temperature sensor 43 for detecting the temperature of combustion gas in the combustion gas passage 4. Have.

In the evaporative combustion apparatus, rapid ignition and improvement of rapid combustion are attempted. In order to realize the rapid ignition and the rapid combustion, the ECU 40 is provided so as to supply the same amount of steam fuel to the catalytic combustion unit 6 at the time of ignition as during normal operation. When combustion is stable, the premixing chamber 1
Since the combustion heat is transmitted to 4 and becomes high temperature, the steam fuel supplied into the premixing chamber 14 is maintained as steam.
However, since the inside of the premixing chamber 14 at the time of ignition start has not reached an atmospheric temperature sufficient to maintain the evaporated fuel as it is as steam, much of the vapor fuel supplied to the premixing chamber 14 condenses and liquefies again. However, a phenomenon occurs in which the steam fuel corresponding to the required combustion amount (combustion amount suitable for rapid ignition and rapid heating) cannot be supplied to the catalytic combustion unit 6.

Therefore, the ECU 40 controls the fuel pump 34 constituting the evaporative fuel supply means so as to supply more fuel than the required combustion amount to the premixing chamber 14 at the time of ignition start, so that the same as at the time of steady operation. Is provided so as to be supplied to the catalytic combustion section 6. Here, the fuel larger than the required combustion amount is defined as a fuel corresponding to the required combustion amount.
In this case, the increased fuel (a) is a correction fuel that is condensed and liquefied and decreases, and the increased fuel (a) is, for example, 0.2 to 0.1.
5th place. That is, the ECU 40 determines the time from ignition start to combustion stabilization (time t1 in FIG.
The fuel pump 34 is controlled so that the fuel larger than the required combustion amount is supplied to the premixing chamber 14 until the combustion is stabilized (after the time t1 in FIG. 1). The fuel pump 34 is controlled so that the fuel corresponding to the amount is supplied to the premixing chamber 14.

Next, the control performed by the ECU 40 when starting the evaporative combustion device will be described with reference to the time chart of FIG. 1 and the flowchart of FIG. When a start instruction is given (start), a voltage is applied to the center electrode tube 29 to energize the evaporating heater 31 and the catalytic combustion section 6 (step a1, shown as EHCON in FIG. 2). Subsequently, the air pump 24 is turned on (step a2, blower ON in FIG. 2).
Display). Subsequently, the fuel pump 34 is turned on (step a3). At this time, the fuel pump 34 is controlled such that fuel larger than the required combustion amount (a combustion amount suitable for rapid ignition and rapid heating) is supplied to the premixing chamber 14. Specifically, the fuel pump 34 is controlled so that the fuel corresponding to the required combustion amount × (1 + a) is supplied.

Next, a predetermined time t1 after the start of the operation.
It is determined whether or not (time suitable for stabilizing combustion) has elapsed (step a4). If the result of this determination is NO, the combustion is not yet stable, and step a
Returning to 3, the fuel pump 34 is controlled so that fuel larger than the required combustion amount is supplied to the premixing chamber 14. Judgment result
If YES, the combustion is in a stable state, and the fuel pump 34 is controlled so that the fuel corresponding to the required combustion amount is supplied to the premixing chamber 14 (step a5). Thereafter, the process proceeds to step a6, where steady combustion control is performed.

In this embodiment, an example is shown in which the heater 31 and the catalytic combustion section 6 are always energized during the operation of the evaporative combustion apparatus (ignition source FULL in FIG. 1), but the combustion is stabilized. In the state, the combustion heat is transmitted to the evaporation heater 31 and the catalyst combustion unit 6 and the evaporation heater 31 and the catalyst combustion unit 6 are maintained at a high temperature. The energization of the unit 6 may be stopped. In this case, the energization may be stopped after ignition is confirmed by the detection value of the exhaust gas temperature sensor 43, or the energization may be stopped by timer control.

Next, the characteristic effects according to the first embodiment will be described. As described above, the evaporative combustion apparatus has a required combustion amount (a combustion amount suitable for rapid ignition and rapid heating) at the time of ignition start (until a predetermined time t1 at which combustion stabilizes after operation is started). ) More fuel is in the premix chamber 1
4 is supplied. Thereby, at the time of ignition start, the premix chamber 1
Even if the vapor fuel supplied to the fuel cell 4 is condensed and liquefied, the liquefied component is supplemented by the increase control of the fuel, and as a result, the vapor fuel corresponding to the required combustion amount is supplied to the catalytic combustion unit 6. This keeps the air-fuel ratio at an appropriate level,
By optimizing the air-fuel ratio, deterioration of ignition performance can be eliminated.

Further, the evaporative combustion apparatus of the prior application (Japanese Patent Application No.
No. 1566651), the fuel supply amount and the air supply amount are increased stepwise to increase the combustion amount without deteriorating the emission at the start. However, in recent years, since rapid temperature rise is desired, in the present embodiment, the same steam fuel as in the steady operation is supplied to the catalytic combustion unit 6 at the time of ignition start to start combustion. Thereby, rapid ignition and rapid combustion can be improved.

[Second Embodiment] In the second embodiment, in addition to the normal temperature start, the condensed and liquefied component is corrected at the low temperature start to maintain the ignition start performance as the original performance. The ECU 40 includes a temperature detecting unit that detects an environmental temperature at the time of starting ignition, and when the environmental temperature at the time of starting ignition is low,
The fuel pump 34 is controlled so as to supply the premixing chamber 14 with fuel in which the amount of fuel larger than the required combustion amount is further increased by an amount corresponding to the temperature difference from that at the time of normal temperature control.

In this embodiment, the exhaust gas temperature sensor 4 is used as temperature detecting means for detecting the environmental temperature at the time of starting ignition.
Although the example using the detected temperature of No. 3 is shown, the environmental temperature at the time of starting may be detected from other sensors (for example, the water temperature sensor 42 or the like). Further, in this embodiment, when the environmental temperature at the time of ignition start is equal to or lower than a predetermined temperature (-20 ° C. or lower), an example in which the correction fuel at a lower temperature is added is shown. It may be provided that the correction fuel at the time of low temperature increases as the size increases.

The starting control by the ECU 40 in the second embodiment will be described with reference to the time chart of FIG. 6 and the flowchart of FIG. When a start instruction is given (start), a voltage is applied to the center electrode tube 29 to energize the evaporation heater 31 and the catalytic combustion unit 6 (step b).
1, EHCON in FIG. 7). Subsequently, the air pump 24 is turned on (step b2, shown in FIG. 7 as blower ON).

Next, it is determined whether the environmental temperature at the time of starting is a low temperature or a normal temperature (step b3). That is, it is determined whether or not the temperature detected by the exhaust gas temperature sensor 43 at the time of starting is −20 ° C. or less. If the result of this determination is NO (normal temperature at start-up), the fuel pump 34 is turned on (step b4). At this time, the fuel pump 34 is controlled so that fuel larger than the required combustion amount (a combustion amount suitable for rapid ignition and rapid heating) is supplied to the premixing chamber 14.
Specifically, the fuel pump 34 is controlled such that fuel corresponding to the required combustion amount × (1 + a) is supplied.

Next, a predetermined time t1 after the start of the operation.
It is determined whether or not (time suitable for stabilizing combustion) has elapsed (step b5). If the result of this determination is NO, the combustion is not yet stable, and step b
Returning to FIG. 4, the fuel pump 34 is supplied so that fuel (correction fuel a at normal temperature) larger than the required combustion amount is supplied to the premixing chamber 14.
Control. If the decision result in the step b5 is YES,
The fuel pump 34 is in a state in which the combustion has shifted to the stable combustion, and the fuel corresponding to the required combustion amount is supplied to the premixing chamber 14.
Is controlled (step b6). Thereafter, the process proceeds to step b7 to perform steady combustion control.

On the other hand, when the result of the judgment at step b3 is YES (low temperature at start-up), the fuel pump 34 is turned on (step b8). At this time, the fuel pump 34 reserves the fuel corresponding to the required combustion amount (combustion amount suitable for rapid ignition and rapid heating) in addition to the normal temperature corrected fuel and the low temperature corrected fuel. It is controlled so as to be supplied to the mixing chamber 14. Specifically, the required combustion amount × (1 + a +
The fuel pump 34 is supplied so that the fuel corresponding to b) is supplied.
Is controlled.

Next, a predetermined time t1 after the start of the operation.
It is determined whether (a time suitable for stabilizing combustion) has elapsed (step b9). If the determination result in step b9 is NO, the combustion is not yet stable, and the process returns to step b8 so that fuel in which the amount of fuel larger than the required combustion amount is further increased is supplied to the premixing chamber 14. The fuel pump 34 is controlled. The judgment result of step b9 is YE
In the case of S, the state has shifted to stable combustion, and the processing shifts to step b6, where the fuel pump 34 is controlled so that the fuel corresponding to the required combustion amount is supplied to the premixing chamber 14, and thereafter, step b7 Then, the steady combustion control is performed.

Next, the characteristic effects according to the second embodiment will be described. During the low temperature start, the liquefaction amount in the premixing chamber 14 further increases as compared with the normal temperature start. However, as described above, in the second embodiment, when the environmental temperature at the time of the ignition start is low, the liquefaction amount is higher than at the normal temperature start. In consideration of the temperature difference, the fuel is supplied to the premixing chamber 14 with the fuel further increased than the required combustion amount. As a result, even at the time of low-temperature start-up, steam fuel corresponding to the required combustion amount (combustion amount suitable for rapid ignition and rapid heating) is supplied to the combustion section, and the air-fuel ratio is maintained at an appropriate level. In addition, the deterioration of the ignition performance can be eliminated by optimizing the air-fuel ratio.

[Third Embodiment] In the third embodiment, deterioration of emission due to liquefied fuel condensed at the time of ignition start being re-evaporated and burned by combustion heat is suppressed. The ECU 40 starts the combustion and starts the premixing chamber 14.
In the region where the fuel condensed and liquefied in the above is re-evaporated by the heat of combustion (time t1 to t2 in FIG. 8), the supply amount of the liquid fuel to the fuel evaporator 7 is made lower than the required combustion amount (or to the fuel evaporator 7). The fuel pump 34 is controlled so as to stop the supply of the liquid fuel. In this embodiment, an example is shown in which the fuel is reduced in a stepless manner. However, the fuel may be reduced in a stepwise manner in accordance with the re-evaporation amount of the fuel.

The control at the time of starting by the ECU 40 in the third embodiment will be described with reference to the time chart of FIG. 8 and the flowchart of FIG. This control is performed immediately before step b6 in the flowchart (see FIG. 7) shown in the second embodiment described above so that the fuel pump 34 reduces the supply amount of the liquid fuel to the fuel evaporating means 7 from the required combustion amount. Are added to the steps c1 and c2 for controlling.

That is, from the time (t1) at which the fuel condensed and liquefied in the premixing chamber 14 is re-evaporated by the heat of combustion to the time (t2) at which the re-evaporation is completed, the fuel pump 34 supplies the fuel less than the required combustion amount. It is controlled so as to be supplied to the premixing chamber 14. Specifically, in step c1, the fuel pump 34 is controlled so that the fuel corresponding to the required combustion amount × (1-c) is supplied. Then, step c2
Then, it is determined whether or not a predetermined time t2 (time when the re-evaporation is almost completed) has elapsed since the start of the operation. If the determination result is NO, the process returns to step c1, and the determination result is YE
In the case of S, the process proceeds to step b6.

Next, the characteristic effects according to the third embodiment will be described. In the region t1 to t2 in which the condensed and liquefied fuel is re-evaporated by the combustion heat, the amount of the evaporated fuel is cut by the control of the fuel pump 34. Will be supplied. As a result, an appropriate air-fuel ratio is maintained even in the region t1 to t2 where the condensed and liquefied fuel is re-evaporated.

[Fourth Embodiment] In the third embodiment, an example is described in which the air-fuel ratio is optimized by reducing the supply amount of the liquid fuel in a region t1 to t2 in which the condensed and liquefied fuel is re-evaporated. As described above, in the fourth embodiment, the air-fuel ratio is optimized by increasing the supply amount of air in the region t1 to t2 where the condensed and liquefied fuel is re-evaporated. The ECU 40 determines the range from t1 to t1 in which the fuel condensed and liquefied in the premixing chamber 14 after the start of combustion is re-evaporated by combustion heat.
In 2, the air pump 24 is controlled so that the supply amount of air is increased from an air amount corresponding to the required combustion amount (hereinafter, required air amount). In this embodiment, an example is shown in which the amount of air is increased steplessly, but it may be provided so that the amount of air is increased stepwise according to the amount of re-evaporation of fuel.

Referring to the time chart of FIG. 10 and the flowchart of FIG.
The control at the time of starting will be described. This control is performed between steps b1 and b7 in the flowchart (see FIG. 7) shown in the second embodiment above, in steps d1 to d7 for controlling the air pump 24 so as to increase the supply amount of air from the required air amount. d3 is added.

That is, from the time (t 1) at which the fuel condensed and liquefied in the premixing chamber 14 is re-evaporated by the heat of combustion to the time (t 2) at which the re-evaporation is completed, the air pump 24 controls the amount of air suitable for the required air amount. It is controlled so that a large amount of air is supplied. More specifically, in step d1, the air pump 24 is controlled so that air corresponding to the required air amount × (1 + d) is supplied. Next, in step d2, it is determined whether or not a predetermined time t2 (a time when the re-evaporation is almost completed) has elapsed since the start of the operation. If the determination result is NO, the process returns to step d1, and the determination result is returned. Is YES
In the case of (1), the operation proceeds to step d3, where the air pump 24 is controlled so that the required air amount is supplied, and thereafter, the operation proceeds to step b7.

Next, the characteristic effects according to the fourth embodiment will be described. In the region t1 to t2 in which the condensed and liquefied fuel is re-evaporated by the combustion heat, the amount of air corresponding to the re-evaporated fuel is increased by the control of the air pump 24. As a result, the condensed and liquefied fuel is re-evaporated in the regions t1 to t1.
Also in 2, the air-fuel ratio is kept at an appropriate level.

[Other Embodiments] In the above embodiment, the present invention is applied to the evaporative combustion apparatus having the catalytic combustion section 6, but the present invention is applied to an evaporative combustion apparatus having a burner combustion section for performing high-temperature combustion. The invention may be applied.

[Brief description of the drawings]

FIG. 1 is a time chart for explaining an operation (first example);
Embodiment).

FIG. 2 is a flowchart for explaining an operation (first example)
Embodiment).

FIG. 3 is a schematic sectional view of a hot water heating device using an evaporative combustion device (first embodiment).

FIG. 4 is an enlarged sectional view of a main part of the evaporative combustion device (first example).
Embodiment).

FIG. 5 is a perspective view for explaining the assembly of the evaporation heater and the catalytic combustion section (first embodiment).

FIG. 6 is a time chart for explaining the operation (second chart);
Embodiment).

FIG. 7 is a flowchart for explaining the operation (second
Embodiment).

FIG. 8 is a time chart for explaining the operation (third chart);
Embodiment).

FIG. 9 is a flowchart for explaining the operation (third embodiment);
Embodiment).

FIG. 10 is a time chart for explaining the operation (fourth embodiment).

FIG. 11 is a flowchart illustrating an operation (fourth embodiment).

[Explanation of symbols]

 6 Catalytic Combustion Unit 7 Fuel Evaporation Means (Components of Evaporative Fuel Supply Means) 14 Premix Chamber 24 Air Pump (Air Supply Means) 34 Fuel Pump (Components of Evaporative Fuel Supply Means) 40 ECU (Control Means) 43 Exhaust Temperature Sensor (Temperature detection means)

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Yoshifumi Ito 1-1-1 Showa-cho, Kariya-shi, Aichi F-term in DENSO Corporation (Reference) 3K003 EA07 FA01 FB04 FB05 FC04 FC05 GA04 HA03 3K005 AB06 AB16 AC06 BA01 BA05 BA06 BA08 CA05 DA01 3K052 AA01 AB04 AB08 AB10 AB11 AB12 AB14 AC05 FA01 GA01 GC01 GD01 GE01 JA01 JA04 3K068 FA01 FB06 FC06 FD04 GA01 HA06 JA06

Claims (6)

[Claims] An evaporative fuel supply means for evaporating and supplying liquid fuel to a premixing chamber upstream of the combustion section; and a premixing chamber upstream of the combustion section. Air supply means for supplying air; control means for controlling the evaporative fuel supply means such that, at the time of ignition start, fuel larger than a required combustion amount required for the combustion section is supplied to the premixing chamber. An evaporative combustion device comprising: 2. The evaporative combustion apparatus according to claim 1, wherein said control means includes a temperature detection means for detecting at least an environmental temperature at the time of ignition start, and when the environmental temperature at the time of ignition start is low, the control means is more controlled than at the time of normal temperature control. An evaporative combustion apparatus characterized in that the evaporative fuel supply means is controlled such that fuel in which an amount of fuel larger than the required combustion amount is further increased is supplied to the premixing chamber in consideration of the temperature difference. 3. The evaporative combustion apparatus according to claim 1 or 2, wherein the control means includes: in a region where combustion is started and fuel condensed and liquefied in the premixing chamber is re-evaporated by heat transmission, An evaporative combustion apparatus characterized in that the supply amount of liquid fuel to the evaporative fuel supply means is made lower than the required combustion amount, or the supply of liquid fuel to the evaporative fuel supply means is stopped. 4. The evaporative combustion apparatus according to claim 1, wherein the control means controls the air supply means in addition to the evaporative fuel supply means, and combustion starts. In a region where the fuel condensed and liquefied in the premixing chamber is re-evaporated by the transfer of heat, the amount of air supplied by the air supply means is increased from the amount of air corresponding to the required combustion amount. Evaporative combustion device. 5. A combustion section for burning the vaporized fuel, evaporative fuel supply means for evaporating and supplying the liquid fuel to a premixing chamber upstream of the combustion section, and an evaporative fuel supply means for supplying the vaporized fuel to the premixing chamber upstream of the combustion section. Air supply means for supplying air, and in a region where combustion starts and fuel condensed and liquefied in the premixing chamber is re-evaporated by heat transfer, the supply amount of liquid fuel to the evaporated fuel supply means Control means for lowering the required combustion amount required for the combustion part or for stopping supply of liquid fuel to the evaporative fuel supply means. 6. A combustion section for burning the evaporated fuel, evaporative fuel supply means for evaporating and supplying liquid fuel to a premixing chamber upstream of the combustion section, and Air supply means for supplying air; and control means for increasing the amount of air supplied by the air supply means in a region where combustion starts and fuel condensed and liquefied in the premixing chamber is re-evaporated by heat transmission. An evaporative combustion device comprising: