JPH0115892Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an intake burner for heating intake air flowing through the intake system of an internal combustion engine such as a diesel engine to improve engine startability. This invention relates to a new intake burner using a heater made of a ceramic body and a heating resistor made of tungsten embedded inside the heater.

[Technical background of the invention and its problems]

In general, internal combustion engines, and diesel engines in particular, generate spontaneous combustion only by compressing the intake air in the cylinder in environments where the temperature of the air being taken in is relatively low (cold regions, cold times, etc.). It is difficult to induce ignition, and a smooth engine start can hardly be expected.

In order to overcome this situation, as shown in Fig. 1, the intake system 2 of the engine 1 is equipped with a
The engine 1 uses this combustion heat to heat the circulating intake air and
An intake burner 3 is provided to improve startability.

Conventionally, as this type of intake burner, those illustrated in FIGS. 2 and 3 are known.
In FIG. 2, reference numeral 3a denotes an intake burner that is provided through the intake pipe 4 and has a combustion end 5 extending inward to the intake system 2 in order to burn the supplied fuel and heat the flowing intake air. The intake burner 3a includes a fuel supply tube 6 for guiding fuel supplied from a fuel pump or the like (not shown) to the combustion end 5, and a heat generating tube for surrounding and heating the fuel supply tube 6 from the outer circumferential side thereof. It has a resistor 7.
The heating resistor 7 is formed by winding a nichrome wire or the like into a coil, and is configured so that the entire body becomes red-hot when a voltage is applied from a power source (not shown). The fuel flowing in from the inlet 6a of the fuel supply tube 6 flows through the fuel supply tube 6 while being adjusted in flow rate by the orifice 6b, and is vaporized by being heated by the heat generating resistor 7 and reaches the combustion end 5. The vaporized fuel then flows out into the intake system 2, is further heated by the heating resistor 7, and is ignited, causing the internal combustion engine 1 to ignite.
The system was designed to heat the intake air supplied to the

However, such an intake burner 3a has the following problems.

(1) In order to effectively obtain thermal radiation, the heating resistor 7 was made of bare nichrome wire, etc., so if a high voltage was applied to shorten the engine starting period and the wire became red hot, it would oxidize and break. It was highly possible. For this reason, the heating resistor 7 has to be heated slowly, prolonging the engine starting period.

(2) Since the heat generating resistor 7 is directly exposed to low temperature intake air, when the starter motor is driven to start the engine, the heat generating resistor 7 is cooled down due to the accompanying increase in the amount of intake air, making it impossible to maintain combustion. The engine could not be started smoothly.

The intake burner 3b shown in FIG. 3 has a heater 10 in which the heating resistor 7 is inserted into a metal sheath 8, and the metal sheath 8 is compactly filled with magnesium oxide powder 9 to have a high heat capacity. are doing. This heater 10 has a vaporizing end 12 that faces a fuel supply nozzle body 11 provided outside the intake system 2 and vaporizes the fuel supplied from this. The fuel is guided to a fuel end 5 extending inward of the system 2 for ignition and combustion.

Even with such an intake burner 3b,
The following problems arose.

(1) The heating resistor 7 heats the metal sheath 8 via the magnesium oxide powder 9 filled in to insulate it from the atmosphere and hold and fix it inside the heater 10, so the temperature rise time is prolonged and startup is delayed. It was not possible to shorten the period.

(2) When manufacturing the heater 10, the metal sheath 8 is filled with magnesium oxide powder 9, so the pitch of the heating resistor 7 may be uneven, making it impossible to obtain an accurate pitch, or causing a short circuit within the sheath 8. Due to its structure, the temperature of the heater 10 could not be adequately controlled, and the temperature distribution from the vaporization end 12 to the combustion end 5 could not be set appropriately. Therefore, due to over-combustion, too much oxygen is consumed in the intake system 2, resulting in an oxygen deficiency state, or the heater 10
Smooth starting performance was often not achieved due to reasons such as insufficient heating of the entire engine.

[Purpose of invention]

The present invention was devised in view of the above-mentioned problems, and its purpose is to create a simple structure in which the entire heater is made of ceramic and a tungsten wire heating resistor is embedded within the heater. However, it is possible to quickly heat the heater, shorten the temperature rise time, maintain stable combustion, and improve engine startability. To provide an intake burner that can freely set the temperature distribution of the heater to properly heat and maintain the heater, can sufficiently control the temperature, and can also improve its structural reliability. .

[Means to solve the problem]

In order to solve the above-mentioned problems, this invention uses a heating resistor made of tungsten wire, in which the winding pitch of the fuel vaporization promoting part is formed tightly against the combustion part of the vaporized fuel, and a heater formed into a rod shape of a ceramic body. A multi-stage cylindrical metal support member is embedded on the axis and has a thin wall on the side of the combustion part and a thick wall on the end of the vaporization part. The intake burner consists of a cylindrical protective cover that fits into the thick part of the component and a fuel supply nozzle body that supplies fuel to the thin part.

[Effect]

The heat-generating resistor made of tungsten wire heats the vaporization promoting part of the heater made of a ceramic body in its dense pitched part more rapidly than the combustion part, and the supporting member surrounding the vaporizing promoting part heats up the fuel evaporation. After reaching the temperature, the fuel supplied from the fuel supply nozzle body to the vaporization end is vaporized and burned in the combustion part of the heater. On the other hand, the thick part of the vaporization promoting part conducts the heat accumulated by heating the dense part of the heat generating resistor to the thin part, which is the vaporization end side, so the temperature tends to decrease due to evaporation of the fuel. The temperature of the evaporation promoting portion of the support member is maintained at the evaporation temperature of the fuel.

In other words, the temperature of the thin wall portion that directly contributes to fuel evaporation can be stably maintained at the fuel evaporation temperature.

On the other hand, the support member protects the ceramic body, which is prone to heat cracks, from direct temperature changes caused by the fuel.

[Example of idea]

A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

As shown in FIG. 4, an intake burner 13 is inserted into the intake system 2 defined in the intake pipe 4 such as an intake manifold, and is used to heat the flowing intake air by burning the supplied fuel. .

This intake burner 13 is supported by having a hollow outer cylinder 14 forming its outer shell attached to the intake pipe 4 with a nut 15 screwed onto one end of the hollow outer cylinder 14 . This outer cylinder 14 is provided with a hollow cylindrical protective cover 16 at the end extending into the intake system 2, and a heater 17, which will be described later, is located approximately in the center of the outer cylinder 14 and located outside the intake system 2. A fuel supply nozzle body 19 is provided facing the vaporization end 18 of. In this fuel supply nozzle body 19, fuel is supplied from a fuel pump or the like (not shown) to a supply port 19a formed by extending radially outward from the outer cylinder 14, and the flow rate is adjusted by an orifice 19b provided inside the fuel supply port 19a. Heater 1
7 is configured to lead the fuel to the vaporization end 18 of 7. In addition, the protective cover 16 is provided with appropriate intake holes 16a on its circumferential side, and has heaters 17, which will be described later.
is configured to introduce a portion of the intake air into the combustion end 20 of the engine.

A heater 17, which is a feature of the present invention, is provided in a hollow portion 13a inside the intake burner 13, which is formed in series by the outer cylinder 14 and the protective cover 16. The heater 17 is formed into a rod shape extending inside and outside the intake system 2 along the longitudinal direction of the intake burner 13, and has one end facing the fuel supply nozzle body 19 for heating and vaporizing the supplied fuel. One end extending into the protective cover 16 on the opposite side from the vaporizing end 18 is used to bring the vaporized fuel led from the vaporizing end 18 into contact with a part of the intake air and burn it. It consists of a combustion end 20. The heater 17 is entirely formed of a ceramic body by hot pressing, and has a heating resistor 21 made of tungsten wire embedded therein. The ceramic body has high heat resistance and has the function of constantly maintaining the entire heater 17 at a high temperature to continue stable combustion. This ceramic body also has the function of surrounding and holding the heating resistor 21 inside thereof, preventing oxidation of tungsten, and increasing the heating rate of the heater 17 as much as possible. On the other hand, tungsten has a large temperature resistance coefficient and can instantly generate high heat, which quickly heats the highly heat-resistant ceramic body to instantly raise the surface temperature of the heater 17 and vaporize the fuel. It has the function of being able to ignite.

Furthermore, the present invention is characterized in that the heating resistor 21 made of tungsten wire is formed to have a higher resistance value distribution on the vaporization end 18 side than on the combustion end 20 side, as shown in FIG. More specifically, the heating resistors 21 are wired in a wavy manner, and the pitches thereof are set closer to the vaporizing end 18 than to the combustion end 20. For example, as shown in FIG.
1' are formed at equal pitches, the entire heater 17, that is, the vaporizing end 18, is heated by the applied voltage before fuel is supplied (indicated by the dashed line C in the figure).
However, once fuel starts to be supplied to the vaporizing end 18 (indicated by solid line D in the figure), only the vaporizing end 18 is partially cooled, and that part The resistance value decreases and the partial voltage drops, while the partial voltage on the combustion end 20 side increases and the amount of heat generated increases locally, causing tungsten to generate heat above the allowable temperature Tmax of the ceramic body, causing heat cracks or cracks in the ceramic body. Heat generating resistor 2
There is a possibility that the wire 1' may be disconnected. In the present invention, the heating resistor ₂₁ is wired as shown in FIG. Although the temperature on the vaporization end 18 side is raised more than on the combustion end 20 side within a range that does not exceed the temperature, by sequentially supplying fuel, the temperature on the combustion end 2 (indicated by solid line B in the figure) is increased.
Even though the temperature on the 0 side increases, the drop in the partial voltage on the vaporization end 18 side is suppressed, and the combustion end 20 side is kept within the range below the allowable temperature T _MAX of the ceramic body and above the ignition temperature T _F of the vaporized fuel. , so that the vaporization end 18 side is maintained higher than the lower limit temperature T _L sufficient to vaporize the fuel.

As shown in FIG. 4, the heater 17 configured in this manner is surrounded by a cylindrical holder 22 radially outward from the heater 17 at an appropriate interval and extending from the vaporization end 18 side to the combustion end 20 side. be done. This holder 22
is configured such that one end thereof is attached to the outer cylinder 14 and the fuel vaporized at the vaporization end 18 side is guided to the combustion end 20 inside the intake system 2. On the other hand, a cylindrical metal support member 23 is attached to the outer periphery of the intake system 2 on the side of the vaporization end 18 to cover it. This metal support member 23 has a large-diameter engagement portion 2 at one end thereof.
3a, and is pressed by a hollow bolt body 24 screwed from one end of the outer cylinder 14.
5 to be engaged with the stepped portion 14a of the outer cylinder 14 to support the heater 17 in a predetermined position. Further, an electrode plate 26 to which one end of the heating resistor 21 is connected is attached to the end portion 17a of the heater 17 extending further outward from the metal support member 23.
Nuts 27 and plates 28 are attached and abut against a rod 30 constituting the terminal 29. A lead wire 31 connected to a terminal 29 is connected to the electrode plate 26 so that a voltage is applied from a power source such as a battery (not shown). Furthermore, the earth end side of the heating resistor 21 is
It is grounded to the intake pipe 4 and the like via the metal support member 23 and the outer cylinder 14.

Next, the operation of the present invention will be described.

When starting the engine, turn on the key switch.
When turned ON, voltage is first applied to the heating resistor 21 from a power source such as a battery. When the temperature of the entire heater 17 made of ceramic body is rapidly raised by the heating resistor 21 made of tungsten wire as shown by the dashed line A in FIG. The fuel is led out to the vaporizing end 18 of the heater 17. The vaporization end 18 of the heater 17 heated by the heating resistor 21 is heated to a relatively high temperature before fuel supply, but is cooled by the sequentially supplied fuel and maintained at a lower limit temperature T _L or higher sufficient to vaporize the fuel. to vaporize the fuel. The vaporized fuel is guided into the holder 22 and reaches the combustion end 20 of the heater 17. Before the fuel is supplied, the temperature of the combustion end 2 is raised to a relatively lower temperature than that of the vaporization end 18, but as fuel is sequentially supplied to the vaporization end 18, the allowable temperature of the ceramic body is increased as shown by the solid line B in FIG. The temperature is raised to the range between Tmax and ignition temperature T _F ,
The vaporized fuel led out from the holder 22 and in contact with a portion of the intake air is ignited and combusted, thereby heating the flowing intake air.

By the way, in the present invention, the entire heater 17 is molded from a ceramic body, and the heating resistor 21 made of tungsten wire is buried inside the heater 17, so that the property of tungsten, that is, the ability to instantly generate high heat, is avoided. This makes it possible to quickly heat the entire heater 17 and shorten the temperature rise time, and also maintains stable combustion even when exposed to intake air by maintaining the entire heater at a high temperature due to the properties of ceramic, that is, its heat resistance. This makes it possible to improve the startability of the engine.

In addition, since the heater used in the intake burner of the present invention uses tungsten wire as the heating resistor 21, the resistance value distribution due to the structure, that is, the heater 17
It is possible to freely set the heating temperature distribution of the heater 17, and the temperature of the heater 17 can be accurately controlled.
Based on this, the heating resistor 21 is formed to have a higher resistance value distribution on the vaporization end 18 side than on the combustion end 20 side, thereby preventing a sudden temperature rise on the combustion end 20 side or heating exceeding the allowable temperature Tmax of the ceramic body. At the same time, the vaporizing end 18 side and the combustion end 20 side can be heated to a predetermined temperature, and the temperature can be sufficiently controlled, and the reliability of the structure of the heater 17 itself can be improved.

[Modification example]

In the above embodiment, the heating resistor is formed in a wavy shape, and the resistance values on the combustion end side and the vaporization end side are different by changing the pitch of the heating resistor, but the present invention is not limited to this. Of course, the low resistance value may be changed by changing the wire diameter, shape, etc. instead of the wire diameter, shape, etc.

[Effect of idea]

According to the present invention described above, the following excellent effects are exhibited.

(1) A heating resistor made of tungsten wire, in which the part that promotes vaporization of the fuel is tightly wound around the part that burns the vaporized fuel, is embedded on the axis of a heater made of ceramic and shaped into a rod. A multi-stage cylindrical metal support member is fitted into the vaporization promoting part of the heater, and the combustion part side is thin and the end of the vaporization promoting part is thick. Since a fuel supply nozzle body for supplying fuel to the thin-walled portion is provided on the cylindrical protective cover, the temperature of the vaporization promoting portion can be controlled while protecting the ceramic heater from direct temperature changes of the fuel. The temperature of the combustion part can be maintained at the evaporation temperature of the fuel, and the temperature of the combustion part can be adjusted to the ignition temperature of the evaporated fuel. Therefore, the intake air flowing through the intake system can be smoothly heated to improve the startability of the engine.

(2) Since the heating resistor is made by embedding tungsten wire, the heating temperature distribution of the heater can be freely set due to the structure, and the temperature of the heater can be adequately controlled.

(3) Therefore, since the heating resistor can be formed to have a higher resistance value distribution on the vaporization end side than on the combustion end side, it is possible to prevent the combustion end side from being heated above the permissible temperature of the ceramic body, and to prevent the heating resistor from heating up to the same temperature as the vaporization end side. The heater can be heated to a predetermined temperature, the heater can be heated to an appropriate temperature distribution, and its structural reliability can be improved.

(4) The structure is simple and can be easily adopted.

[Brief explanation of the drawing]

Fig. 1 is a schematic cross-sectional plan view showing the intake system of an internal combustion engine, Figs. 2 and 3 are partially cutaway side views showing a conventional example, and Fig. 4 is a partially cutaway side view showing a preferred embodiment of the present invention. A side view, Fig. 5 is a diagram showing the relationship between the wiring of the heating resistor adopted in the present invention and the temperature distribution of the heater based on it, and Fig. 6 is a diagram showing the wiring when the heating resistor is wired at equal pitches. It is a figure which shows the relationship with the temperature distribution of a heater based on it. In the figure, 1 is an internal combustion engine, 2 is an intake system, 13 is an intake burner, 17 is a heater, 18 is its vaporization end, 20 is its combustion end, and 21 is a heating resistor.

Claims (1)

[Scope of utility model registration request] A heating resistor made of tungsten wire, in which the winding pitch of the fuel vaporization promoting part is tightly formed with respect to the combustion part of the vaporized fuel, is buried on the axis of a heater formed into a rod shape from a ceramic body. A metal support member formed in a multi-stage cylinder shape with a thin wall on the side of the combustion part and a thick wall on the end of the vaporization promoting part is fitted to the vaporization promoting part, and a cylinder fitted to the thick part of the supporting member. An intake burner characterized in that the shaped protective cover is provided with a fuel supply nozzle body for supplying fuel to the thin walled portion.