JP3047916B2 - Intake air preheating device for internal combustion engine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intake air preheating apparatus for an internal combustion engine (predominantly a diesel engine) used for preheating the intake air and smoothly starting the internal combustion engine.

[Related Art] An internal combustion engine (mainly a diesel engine) is difficult to start when the outside temperature is low such as in winter. As a countermeasure, conventional diesel engines (mainly direct injection diesel engines) have an electric heating element in the intake passage,
An intake air preheating device (air heater) or the like was installed to preheat the intake air and send high-temperature air into the combustion chamber to smoothly start the internal combustion engine.

When preheating the intake air with the electrothermal heating element, the nearby air is heated by radiant heat.In order to improve the heating efficiency, it is important that the temperature of the heating element itself be high and the surface area of the heating element is large. is there. Further, in order to shorten the preheating time, it is desirable that a large amount of electric power flows at the beginning of energization, quickly raises the temperature to a predetermined temperature, and radiates a large amount of heat.
In order to further improve the startability in cold weather, if the preheating time is extended, the amount of power is suppressed when the temperature is raised to a predetermined temperature, and the temperature rise of the heating element is suppressed to an appropriate temperature range. It is desirable that the load on the battery due to the heat generation is small and the heating element can be prevented from being damaged due to excessive temperature rise.

Conventionally known intake preheating devices include (a) a metal heating element made of nickel chromium or iron chromium, or (b) PT
There are many types using a heating element of C ceramic heater material (JP-A-57-163841).

[Problems to be Solved by the Invention] However, in the conventional intake air preheating device, it is difficult to achieve both the reduction of the preheating time and the durability against the extension of the energization time. For example, in the case of (a) the metal heating element made of nickel chromium or iron chromium, the temperature coefficient of resistance (8 × 10 ⁻⁶ / ° C.)
(Approximately 450 × 10 ⁻⁶ / ° C.), and the electric power after the start of energization is almost constant. Therefore, the preheating time is determined by the heater capacity. When the amount of power is increased to shorten the preheating time, the amount of current increases, and the load on the battery increases during after-heat after the engine is started. there were.

As a countermeasure against the above drawbacks, a system with a complicated control mechanism such as that of Japanese Utility Model Laid-Open No. 57-193958 has been devised, but the system becomes complicated and costly, and the heating element on the rapid heating side is continuously connected. When the rated voltage was applied to the heating element, there was a problem that the heating element was melted and damaged.

In the case of (b) the heating element made of the PTC ceramic heater material, the relationship between the resistance value and the temperature at the time of energization changes logarithmically. Temperature is about 150 ° C, the effect of heating the air near the heater by radiant heat is extremely small, so it is not possible to improve the startability even if preheating for a long time. is there.

The present invention has been made to solve the above-described problems, and it is possible to obtain a large amount of electric power in the initial stage of energization, rapidly raise the temperature of the heating element to a desired temperature, shorten the preheating time, and improve the startability in cold weather. When the preheating time is extended, the power consumption is suppressed by the self-control action of the heating element, which increases its electrical resistance as the temperature rises, and the temperature rise of the heating element is suppressed to an appropriate temperature range without a complicated control mechanism. Accordingly, an object of the present invention is to provide an intake preheating device for an internal combustion engine, which can reduce a load on a battery due to extension of a preheating time, prevent a heating element from being damaged by an excessive temperature rise, and simplify a control mechanism.

Means for Solving the Problems In order to solve the above problems, an intake preheating device for an internal combustion engine according to the present invention includes a frame or a rod-shaped electric resistance material provided on a frame constituting a part of an intake passage of the internal combustion engine. In an intake preheating apparatus for an internal combustion engine, wherein an electric heating element having a bent and meandering shape is electrically insulated and supported, the heating element is mainly composed of nickel chromium or iron chromium having a small temperature coefficient of resistance. And a second heating element mainly composed of nickel or iron and having a large temperature coefficient of resistance.
The heating element and the second heating element are arranged in two or more stages in series such that the first heating element is arranged on the upstream side with respect to the airflow to be heated, and the second heating element is arranged on the downstream side. It is more preferable that the range of the temperature coefficient of resistance of the first heating element is set to 8 × 10 ⁻⁶ / ° C. to 450 × 10 ⁻⁶ / ° C.
Range of 6 × 10 ^-2 / ° C to 5 × 10
^-3 / ° C is a technical measure.

[Action and Effect of the Invention] In the intake air preheating apparatus according to claim 1 of the present invention, a first heating element having a small temperature coefficient of resistance is arranged upstream of an intake air flow, and a second heating element having a large temperature coefficient of resistance is arranged. Has the following effects by arranging on the downstream side.

Since the heating element having a small resistance temperature coefficient is arranged on the upstream side, low-temperature air always comes into contact with the first heating element on the upstream side first. For the first heating element to efficiently transmit air energy, the larger the temperature difference between the air and the heating element, the better. Therefore, by disposing the first heating element on the upstream side,
This has the effect that the temperature difference between the heating element and the air can be increased, and the temperature rise characteristics and energy efficiency can be improved.

By disposing the heating element having a large resistance temperature coefficient on the downstream side, the second heating element on the downstream side is exposed to the airflow warmed by the first heating element.
The temperature rises strongly due to the temperature rise of the heating element. Since the second heating element has a function of controlling the first heating element so as not to overheat, it is necessary to detect the temperature rise of the first heating element early. Therefore,
Arranging the second heating element on the downstream side is effective in preventing the first heating element from being excessively heated. By the way, even if the second heating element is arranged on the upstream side, it is not always possible to detect an excessive temperature rise because it is heated by the radiant heat received from the first heating element, but the second heating element is arranged on the downstream side. In this case, since the resistance value increases with good responsiveness to the temperature rise of the first heating element, the controllability with respect to the temperature can be improved, the preheating time can be shortened, and the excessive temperature rise can be prevented.

Therefore, even if a complicated control mechanism is not provided, the burden on the battery due to long-time power supply is small, and damage to the heating element due to excessive temperature rise can be prevented. Therefore, the production cost is low, a long preheating or a long afterheating can be performed, and the startability can be improved at a low outside air temperature.

Further, in the intake preheating apparatus according to the second aspect, the range of the temperature coefficient of resistance of the first heating element is set to 8 × 10 ⁻⁶ / ° C. to 450 × 10 ⁻⁶ / ° C.
And the range of the temperature coefficient of resistance of the second heating element is 6 × 10 ⁻² /
C. to 5 × 10 ⁻³ / ° C., when the rated voltage is applied, the amount of electric power (W) at the start of energization is 60%.
Since the electric energy (W) after seconds to 90 seconds is reduced to 0.4 to 0.6 times, if the preheating time is extended or after-heated, the temperature range necessary for intake air heating is maintained, and the overheating of the heating element is prevented. Has practically suitable performance to prevent.

As described above, the intake preheating device for an internal combustion engine according to the present invention is low in cost, can shorten the preheating time, can prevent excessive heating of the heating element, and can improve startability.

Next, a first embodiment of an intake preheating device for an internal combustion engine according to the present invention will be described with reference to FIGS.

In the intake air preheating device A, 1 is a body (frame) made of an aluminum alloy. The body 1 has a circular shape having four protrusions on the outer periphery, and has a hole 1a that forms an intake passage at the center. In the hole 1a of the body 1, a first heating element 21 and a second heating element 22 of different materials are arranged in series in the direction of the intake passage, and a pair of ceramic insulators 31, 3 facing each other.
2. It is sandwiched between the wave springs 41 and 42 and the metal bracket 5.

Of the two heating elements, the heating element 21 is arranged on the upstream side of the intake flow, and the heating element 22 is arranged on the downstream side. In addition, the heating element 21,
Reference numeral 22 denotes a meandering shape formed by continuously bending a band of a thin sheet material having a rectangular cross section in the present embodiment, and has a large contact area with the intake air and a small projected area in the flow direction of the intake air. The bent portions 21a and 22a are respectively provided with the ceramic insulator 3
Embedded in 1, 32. Ceramic insulator 3
1 and 32 are fitted into the metal bracket 5 adjacent to each other. The metal bracket 5 is fitted to face the upper and lower sides of the body 1 in FIG. Two heating elements 21,
22 is urged toward the center by wave springs 41 and 42 between the ceramic insulators 31 and 32 and the metal bracket 5 to suppress vibrations generated during operation. On both sides of the body 1 in FIG. 1 (a), opposite terminals 61a and 61b of the first heating element 21 and opposite terminals 62a and 62b of the second heating element 22 are respectively provided with insulating packings. 7 and attached through. The two heating elements 21 and 22 are electrically connected in series, the terminal 61a and the terminal 62a are connected, the terminal 61b is connected to a power source (not shown), and the terminal 62b is grounded. 8 is a connection cord for grounding.

In this embodiment, the first heating element 21 is made of a heating material mainly composed of iron chromium, and has a temperature coefficient of resistance of (8 × 10 ⁻⁶ / ° C.).
~ 450 × 10 ^-6 / ° C). Its composition is formed by adding 17-26% of chromium (Cr), 2-8% of aluminum (Al) and 0.1% or less of other trace substances (C, Si, P, S) to iron (Fe). .

In the present embodiment, the second heating element 22 is made of a heating material mainly composed of iron (Fe), and has a temperature coefficient of resistance of (6 × 10 ⁻² / ° C.).
~ 5 × 10 ^-3 / ° C). Its composition is as follows. Aluminum (Al) and titanium (Ti) are added to iron (Fe), which is the main component, at 0.2-0.4% each, and manganese (Mn) is added at 0.1-0.3%, and other trace substances (C, Si, Nickel plating is applied to the surface of the iron alloy resistor containing 0.1% or less of (P, S) to improve corrosion resistance and electric current durability.

Next, an intake pipe portion and a combustion chamber of a direct injection diesel engine incorporating the intake preheating device A will be described with reference to FIG.

B is a direct injection diesel engine, 10 is an intake pipe, 13
Is an intake port, 14 is an injector for fuel injection, 15 is a piston having an omega-type combustion chamber 16, 17 is an exhaust port, 18
Is an exhaust valve.

 First, the assembly structure will be described.

The intake preheating device A is an intake pipe 10 of the diesel engine B.
The holes 1a are connected in series. Further, a bolt nut 12 is clamped between a flange portion 10 a provided at an intake end of the intake pipe 10 and the air cleaner 11.

Next, the operation of the engine and the operation of the intake air preheating device A will be described.

At the time of starting, when the key is operated, the preheating contact is closed, the two heating elements 21 and 22 are energized for a predetermined time, and the surrounding air C is heated by the heat generation. When the two heating elements 21 and 22 reach a predetermined temperature at which they can be started, and the key is turned to the contact for the starter, the starter is activated and the heated air (arrow D) flows through the intake pipe.
The engine is operated by being drawn into the omega-type combustion chamber 16 from the intake port 13 through the suction port 13. Thereafter, when the key is released, the operating contact is closed and normal operation is continued.

The first heating element 21 has a small temperature coefficient of resistance (8 × 10 ⁻⁶ / ° C. to 450 × 10 ⁻⁶ / ° C.) due to the above composition,
The heating element 22 has a large temperature coefficient of resistance (6 × 10 ⁻² / ° C. to 5 × 10 ⁻³ / ° C.) due to the above composition, and operates as follows.

At the start of energization, there is no heat, so the resistance value is small,
A large current flows, and the first heating element 21 rapidly generates heat in a short time and rapidly generates heat to a set temperature. Since the resistance value of the heating element 2 increases in proportion to the temperature rise due to the rapid heat generation, the amount of current rapidly decreases in inverse proportion.

The two heating elements used in the above embodiment are shown in the graph of FIG.
Heating characteristics (solid line a = heated temperature) and energizing characteristics (solid line b = current, solid line c = voltage of the first heating element 21 when 22 VDC is applied between the terminals 61b and 62b of the terminals 21 and 22; The dashed line d = voltage of the second heating element 22), the heating characteristic (dashed line e = heating temperature) and the energization characteristic (dashed line f = current) of the conventional heating element (made of iron chrome) are shown.

At the start of energization, there is no heat, so the resistance value is small,
A large current flows, and the first heating element 21 rapidly generates heat in a short time and reaches 800 ° C. in about 13 seconds. The temperature further rises when the energization is further continued, but since the resistance value of the second heating element increases in proportion to the temperature rise due to the rapid heat generation, the amount of current rapidly decreases in inverse proportion. As a result, the temperature of the first heating element 21 reaches a peak (1056 ° C.) 30 seconds after energization, then slowly decreases, and drops to 980 ° C. 60 seconds after energization. The energization is continued and the temperature reaches 935 ° C after 90 seconds. At that time, the energizing current (solid line b) is reduced to 53.5 A from the initial 97 A, and the voltage (dotted line d) and the resistance value of the second heating element 21 are 12.28 V (0.23 Ω) from the initial 4.3 V (0.044 Ω). ).

 Effect of the embodiment.

The preheating time is short, and the initial heating temperature (about 1056
C) is high, so that the startability is greatly improved.

 The present invention includes the following modifications in addition to the above embodiments.

It is sufficient that the frame body can support the heating element so as not to come off due to vibration during operation, and the outer shape of the frame body may be rectangular, hexagonal, elliptical, oval, or the like having a hole that forms an intake passage.

In the above-described embodiment, the first heating element and the second heating element are arranged in two rows in series in the intake direction.
The first heating element and / or the second heating element may be divided and arranged in three or more rows in series.

The shape of the heating element is such that the contact area with the intake air is large and therefore the heat dissipation is good, and the projected area in the flow direction of the intake air should be small so that the intake resistance is small.
A thin strip material such as a teardrop shape may be curved and formed into a continuous meandering shape as in the above embodiment.

In addition to the present embodiment, the material of the first heating element may be nickel chrome, and the material of the second heating element may be mainly nickel.

[Brief description of the drawings]

1 (a) is a front view showing an intake preheating device for an internal combustion engine according to the present invention, FIG. 1 (b) is a right side view thereof, FIG. 1 (c) is a left side view thereof, and FIG. FIG. 3 is a cross-sectional view showing an intake pipe portion of a direct injection diesel engine and an intake preheating device for an internal combustion engine according to the present invention. FIG. 3 is a graph comparing the characteristics of the intake preheating device of the present invention with those of a conventional example. In the figure, A: intake preheating device, B: direct injection type diesel engine, 1: body (frame), 5: metal bracket, 7: insulating packing, 21: first heating element, 22 …
... second heating element, 31, 32 ... ceramic insulator, 41, 42 ... wave spring, 61a, 61b, 62a, 62b ...
Terminal

Continuation of front page (56) References JP-A-57-26326 (JP, A) JP-A-59-56615 (JP, A) JP-A-63-290327 (JP, A) (U) U.S.A. 59-187085 (JP, U) U.S.A. 61-159657 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H05B 3/12 F02M 31/12 301

Claims (2)

(57) [Claims] 1. An internal combustion engine comprising: a frame constituting a part of an intake passage of an internal combustion engine; an electrically heating type heating element in which a band-shaped or rod-shaped electric resistance material is bent and meandered; In the air intake preheating device, the heating element includes a first heating element mainly composed of nickel chromium or iron chrome and having a small temperature coefficient of resistance, and a second heating element mainly composed of nickel or iron having a large temperature coefficient of resistance. Are electrically connected in series, and the first heating element and the second heating element are connected to the heated airflow by the first heating element.
Wherein the second heating element is arranged in two or more stages in series such that the second heating element is arranged on the downstream side. 2. A range of the temperature coefficient of resistance of the first heating element is set to 8 × 10 ⁻⁶ / ° C. to 450 × 10 ⁻⁶ / ° C., and a range of the temperature coefficient of resistance of the second heating element is set to 6 ×. 2. The intake preheating apparatus for an internal combustion engine according to claim 1, wherein the temperature is set to 10 ^-2 / ° C. to 5 × 10 ⁻³ / ° C.