JPH09228836A - Muffler cooling device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the loss of cooling wind in a minimum level, in an engine in which a fly wheel fan is employed. SOLUTION: A cooling clearance 10 for leading cooling wind is formed between a muffler main body part 7 and a heat resistance cover 8 along the whole circumference of the muffler main body part 7, and a wind leading pipe 15 is arranged on a nearly right side position from the lowest position of a fan case 3 so as to lead air pushed out by a fly wheel fan 2 to the cooling clearance 10. It is thus possible to reduce rotational resistance of the fly wheel fan 2, and reduce power loss. It is also possible to use positive pressure which only becomes power loss for cooling the muffler main body part 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a muffler cooling device for cooling the temperature of a muffler body and the temperature of exhaust gas discharged from the muffler body.

[0002]

2. Description of the Related Art Conventionally, a muffler containing a catalyst for removing harmful components of exhaust gas, and a heat shield cover provided outside the muffler body to cool the muffler body, is cooled in a cooling gap between the muffler body and the heat shield cover. A muffler device that sends wind has been proposed. As a specific configuration, there is known a configuration in which power is taken from the crankshaft of the engine and the power is used to drive an air pump to send cooling air to the cooling gap between the muffler body and the heat insulating cover. As another configuration, in the air-cooled engine, a part of the cooling air generated for cooling the cylinder head is guided to a cooling gap by a cooling fan such as a centrifugal flywheel fan to cool the muffler. .

[0003]

However, in the structure for driving the air pump, providing a new air pump only for cooling increases the manufacturing cost. Therefore, in the case of a general-purpose engine in which low cost is important, it is a reality. Not relevant. Further, in the configuration in which a part of the cooling fan air generated for cooling the cylinder head is introduced into the cooling gap to cool the muffler, a part of the cooling air that cools the highest temperature part of the engine such as the cylinder head is partly exhausted by the muffler. Since it is used for cooling, there is a problem that the cooling performance of the cylinder head and the like deteriorates.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and a first object of the present invention is to minimize the loss of cooling air when the cooling air of a cooling fan is used for muffler cooling. It is to provide a muffler cooling device that can perform. Secondly, when using an air pump for cooling the muffler, the manufacturing cost can be reduced and
An engine capable of reducing harmful components of exhaust gas may be provided.

[0005]

A muffler cooling device according to claim 1 for achieving the above first object will be described with reference to, for example, FIG. 1 and FIG. A heat insulating cover 8 is provided so as to cover the muffler main body 7, and a cooling gap 10 for cooling the muffler main body 7 is formed between the muffler main body 7 and the heat insulating cover 8. A fan 2 driven by the crankshaft 13 and a fan case 3 for guiding the cooling air generated by the fan 2 to the cylinder head 5 side are provided so that the outlets 12 for the cooling air flowing through 10 coincide with each other. At the position, the gap between the fan 2 and the fan case 3 is formed to be narrow so that the air is blown by the fan 2 to increase the pressure in the narrow portion, and the pressure (positive pressure) guides the cooling air to the cooling gap 10. Characterized by comprising a baffle means (Shirubefukan 15).

A muffler cooling device according to claim 2 for achieving the above-mentioned second object will be described, for example, with reference to FIG. 3. A heat insulating cover 8 is provided so as to cover the muffler body 7 from the outside. A cooling gap 10 for cooling the muffler body 7 is formed between the muffler body 7 and the heat shield cover 8, and an exhaust gas discharge port 9 of the muffler body 7 and a cooling air discharge port 12 flowing through the cooling gap 10 are formed. And a part of the air passing through the air cleaner 32 is supplied to the cooling gap 10 by the air pump 35, and the air of the same air pump 35 is supplied to the oxidation catalyst arranged in the muffler body 7. Is characterized by.

[0007]

According to the muffler cooling device of the first aspect, the heat shield cover 8 is provided so as to cover the muffler body 7 from the outside, and the muffler body 7 is cooled between the muffler body 7 and the heat shield cover 8. By forming the cooling gap 10, cooling air can be passed through the cooling gap 10 and the temperature of the heat insulating cover 7 can be lowered. Further, an exhaust gas discharge port 9 of the muffler body 7 and a cooling air discharge port 12 flowing through the cooling gap 10
The exhaust gas emitted from the muffler main body 7 and the cooling air flowing through the cooling gap 10 by the exhaust port 12
In this case, the temperature of the exhaust gas can be lowered.

Further, by forming a narrow gap between the fan 2 and the fan case 3 at a predetermined position of the fan case 3 (the lowermost position of the fan case in FIG. 1), there is a place where the pressure becomes high in the narrowed place. Then, the air guide means 1 for communicating the high pressure portion with the cooling gap 10
By providing 5, positive pressure, which would otherwise be wasted, can be used for cooling the muffler. In the arrangement of the fan 2 and the fan case 3, the engine and the crankshaft 1
Depending on the arrangement position of the engine 3, there is often a place where the distance between the fan 2 and the fan case 3 becomes narrower in the engine lower position, but in the present invention, the fact that the pressure is positively increased in the narrow place is utilized to Is for cooling.

According to the muffler cooling device of the second aspect, a part of the air that has passed through the air cleaner 32 is supplied to the cooling gap 10 through the air pump 35, and the compressed air from the same air pump 35 is distributed in the muffler body 7. Since the air pump that supplies oxygen to the oxidation catalyst and the air pump that cools the muffler body 7 can be shared by one air pump, the power loss of the engine can be suppressed. Manufacturing cost can be reduced.

[0010]

As described in the above operation, according to the invention of claim 1, the following unique effects are exhibited. (A) By passing cooling air through the cooling gap, the temperature of the heat insulating cover can be lowered, and the exhaust gas discharged from the muffler main body and the cooling air flowing through the cooling gap are mixed at the exhaust port. The temperature can be lowered. (B) Since an undesired positive pressure can be reduced by the air guide means, the rotation resistance of the fan can be reduced and the power loss can be reduced. Further, a positive pressure enough to cause a power loss can be used for cooling the muffler, and the utilization efficiency of the cooling air can be improved as compared with the case where a part of the cooling air for the cylinder head is used as the muffler cooling air.

According to the invention of claim 2, the above-mentioned (a) is similarly applied.
The effect can be achieved. In addition, since one air pump can be used for supplying oxygen to the oxidation catalyst and for cooling the muffler, it is possible to prevent the muffler from becoming high heat and to provide an engine that can reduce harmful components of exhaust gas at low cost. There is.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a partially longitudinal sectional front view showing a first embodiment in which the muffler cooling device of the present invention is applied to an overhead valve type diesel engine, and FIG. 2 is a schematic transverse sectional view of the muffler.

This overhead valve type diesel engine E is provided with a centrifugal flywheel fan 2 and a fan case 3 on the front side of an engine body 1, a radiator 6 is provided on the upper front side of a cylinder head 5, and is raised by the flywheel fan 2. The cooling air is guided by the fan case 3 and is divided into the outer circumference of the cylinder block 4, the cylinder head 5 and the radiator 6.

In FIG. 1, a muffler body 7 is provided on the upper right side of the engine E, and a heat insulating cover 8 is provided so as to cover the entire circumference of the muffler body 7 from the outside. A cooling gap 10 for guiding cooling air is provided between the muffler body 7 and the heat insulating cover 8.
Are formed over the entire circumference of the muffler body 7. As shown in FIG. 2, since the outlet 12 of the cooling gap 10 extends so as to cover the exhaust gas outlet 9 of the muffler body 7, the cooling air flowing through the cooling gap 10 is exhausted at the outlet 12. The temperature of the exhaust gas can be lowered by mixing with the exhaust gas emitted from the discharge port 9.

At the lowermost position of the fan case 3, a narrow space is formed between the fan case 3 and the flywheel fan 2, so that the tip of the crankshaft 13 is located at the horizontal center of the fan case 3. It has become. The flow of air pushed out by the fan 3 is moved to the right side of the lowermost part of the fan case 3 by the cooling gap 1
The inlet 16 of the air guide tube 15 that leads to 0 is provided, and the outlet 17 is connected to the upstream side position of the heat insulating cover 8 in the cooling gap 10.

The operation of the muffler cooling device having the above structure will be described. The flywheel fan 2 is rotated by the rotation of the crankshaft 13.
1 rotates clockwise in FIG. 1, a centrifugal air flow is generated, and the fan case 3 forms a cooling air flow 20 toward the cylinder block 4 and the cylinder head 5 side. , Cool the radiator 6. Here, in the right area of the fan case 3, due to the rotation of the flywheel fan 2, a flow of wind is generated, and the pressure is slightly higher on the right side than the lowermost position of the fan case 3. Therefore,
When the positive pressure portion and the cooling gap 10 are communicated with each other by the air guide tube 15, the inlet 16 and the outlet 17 of the air guide tube 15 are connected.
A flow of cooling air can be generated toward the.

With this structure, the pressure at the positive pressure portion can be lowered by the air guide tube 15, the rotational resistance of the flywheel fan 2 can be reduced, and the power loss can be reduced. In addition, a positive pressure that is not useful and can cause power loss can be used to cool the muffler body 7, and the flywheel fan 2 and the fan case 3 must be arranged as shown in FIG. 1 in the engine specifications. In the configuration that does not obtain the above, the utilization efficiency of the cooling air can be improved as compared with the case where a part of the cooling air flow 20 is the muffler cooling air.

Further, when the cooling air for cooling the cylinder head 5 or the like is used for cooling the muffler, the cooling air is warmed up, so that the cooling effect of the muffler is small. On the other hand, in the configuration of this embodiment, the fan case 3 is used. Since the air having the lowest temperature introduced from the outside air intake port (not shown) of (1) can be used as cooling air for muffler cooling and exhaust gas temperature reduction, it is also advantageous in this respect.

[0019]

Second Embodiment FIG. 3 is a schematic configuration diagram showing a second embodiment of the muffler cooling device according to the present invention. One feature of this muffler cooling device is that it is applied to a catalytic muffler that supplies air for promoting oxidation to an oxidation catalyst. This catalytic muffler is configured as follows.

Muffler body 7 communicating with the exhaust manifold
First exhaust chamber 26, three-way catalyst chamber 27, second expansion chamber 28, oxidation catalyst chamber 29, third expansion chamber 3
0 is provided, and the catalyst air introduction pipe 31 is inserted into the second expansion chamber 28. The air passing through the air cleaner 32 is taken into the combustion chamber of the engine E by the intake pipe 33. The intake pipe 33 is provided with an air intake pipe 34, and the air in the intake pipe 33 is sucked by the air pump 35. The catalyst air introduction pipe 31 supplies air to the second expansion chamber 28, and the cooling gap air introduction pipe 36 supplies air to the cooling gap 10.

Therefore, the air pump 35 has an air pressure feed port 37 of the catalyst air introduction pipe 32 and a cooling gap air introduction pipe 36.
It has two pressure feed ports of the air pressure feed port 38. The catalyst air introduction pipe 31 has a reed valve 39 in the middle thereof, and the cooling gap air introduction pipe 36 has a control valve 40. That is, by using a large capacity air pump 35, the function of supplying air to the oxidation catalyst,
It also has the function of supplying cooling air to the cooling gap 10.

With this structure, one air pump 35 can supply air for the oxidation catalyst and cool the muffler, which can be performed at low cost.
Further, in this embodiment, the exhaust gas reduces nitrogen oxides (NOx) by the three-way catalyst in the three-way catalyst chamber 27, and reduces hydrocarbons (HC) and oxygen monoxide (CO) by the oxidation catalyst in the oxidation catalyst chamber 29. Since it can be reduced, there is an advantage that harmful components in exhaust gas can be efficiently reduced. That is, even in a general-purpose engine that is often operated at an air-fuel ratio that deviates from the ideal air-fuel ratio, NOx, HC, and CO can be sufficiently reduced by the two-stage catalyst configuration of the three-way catalyst and the oxidation catalyst. Of.

The present invention is not limited to the above embodiment, and various design changes can be made without departing from the scope of the present invention. Hereinafter, such an embodiment will be described. (1) An embodiment obtained by combining the first embodiment and the second embodiment can also be used. That is, in the third embodiment, the muffler body 7 is cooled by the cooling air from the air pump 35 in the cooling gap 10 and the cooling air from the air guide tube 15 communicating with the positive pressure portion of the fan case 3. is there. In this configuration, the cooling air from the air pump 35 can be used only to reduce the temperature of the exhaust gas, and the temperature of the exhaust gas can be further increased compared to the configuration in which the temperature of the exhaust gas is reduced by the cooling air that has passed through the cooling gap 10. Can be suppressed.

Further, in the fourth embodiment, the air sent from the air pump 35 is used only for the oxidation catalyst, and the muffler body 7 is moved by the cooling air from the air guide pipe 15 communicating with the positive pressure portion of the fan case 3. A cooling configuration can also be adopted. With this configuration, oxygen can be supplied to the oxidation catalyst and the temperature rise of the muffler body 7 can be suppressed. (2) In the second embodiment, the cooling air flowing through the cooling gap 10 need not always flow. When the temperature around the engine is low, the temperature of the muffler body 7 is also low, so the control valve 4
0 may be closed to increase the amount of air flowing to the oxidation catalyst.
In the case of such a configuration, the temperature sensor for detecting the temperature of the muffler or the engine and the control valve 40 based on the detected temperature.
Means are provided for controlling.

[Brief description of drawings]

FIG. 1 is a partial vertical sectional front view showing a first embodiment in which a muffler cooling device of the present invention is applied to an overhead valve type diesel engine.

FIG. 2 is a schematic cross-sectional view of a muffler.

FIG. 3 is a schematic configuration diagram showing a second embodiment of a muffler cooling device according to the present invention.

[Explanation of symbols]

2 ... Centrifugal flywheel fan, 3 ... Fan case, 5
... Cylinder head, 7 ... Muffler body, 8 ... Heat-proof cover, 9 ... Exhaust gas discharge port, 10 ... Cooling gap, 12 ... Exhaust port, 13 ... Crank shaft, 15 ... Bladder tube, 32 ... Air cleaner, 35 ... Air pump , E ... engine.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location F01P 5/02 F01P 5/02 A F02B 77/11 F02B 77/11 D

Claims (2)

[Claims] 1. A muffler main body (7) in a muffler cooling device for cooling a muffler of an engine (E) with cooling air.
A heat insulating cover (8) is provided so as to cover the outside of the muffler, and a cooling gap (10) for cooling the muffler main body (7) is formed between the muffler main body (7) and the heat shield cover (8) to form a muffler. The exhaust gas discharge port (9) of the main body (7) and the discharge port (12) of the cooling air flowing through the cooling gap (10) are aligned,
The fan (2) driven by the crankshaft (13) and the cooling air generated by the fan (2) are supplied to the cylinder head (5).
A fan case (3) for guiding air to the side, and the fan (2) and the fan case (3) are formed to have a narrow gap at a predetermined position of the fan case (3), and the fan (2) blows air to narrow A muffler cooling device, characterized in that it is provided with a high pressure at a location, and is provided with an air guide means (15) for guiding the cooling air to the cooling gap (10) by the pressure. 2. A muffler cooling device for cooling a muffler of an engine (E) with cooling air, the muffler body (7)
A heat insulating cover (8) is provided so as to cover the outside of the muffler, and a cooling gap (10) for cooling the muffler main body (7) is formed between the muffler main body (7) and the heat shield cover (8) to form a muffler. The exhaust gas discharge port (9) of the main body (7) and the discharge port (12) of the cooling air flowing through the cooling gap (10) are aligned,
Part of the air passing through the air cleaner (32) is supplied to the cooling gap (10) by the air pump (35), and the air of the same air pump (35) is supplied to the oxidation catalyst arranged in the muffler main body (7). A muffler cooling device having the above structure.