JP3114780B2 - Exhaust gas temperature control device for vehicles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle exhaust temperature control apparatus, and more particularly to a vehicle exhaust temperature control apparatus suitable for controlling the exhaust temperature of a two-stroke engine mounted on a snowmobile at an optimum temperature. About.

[0002]

2. Description of the Related Art A two-stroke engine mounted on a snowmobile, for example, comprises a cylinder part 100, a crankcase part 101, a carburetor 102, an air cleaner 103, etc., as shown in FIG. An exhaust pipe 107 having an expansion section 104, a chamber 105, and a throttle section 106 is connected to an exhaust port (not shown) of the cylinder section 100. In this case, the two-stroke engine is disposed on the vehicle body front side of the snowmobile in a state of being covered by a hood having an opening for introducing outside air at a predetermined location.

FIG. 13 is a diagram showing the relationship between the exhaust pressure and the pressure oscillation of the chamber (exhaust pulse, negative pressure pulse, reflected pulse due to the throttle). In FIG. “SO” indicates that the scavenging valve is open, code “BDC” indicates bottom dead center, code “TDC” indicates top dead center, code “EC” indicates that the exhaust port is closed, and code “SC”.
Indicates that the scavenging valve is in the closed state. As shown in FIG. 13, when the reflected pulse is immediately before “EC”, the efficiency of charging the air mixed fuel from the carburetor 102 to the cylinder unit 100 is high, and a high output can be obtained.

[0004]

However, in the above-described prior art, the shape of the chamber and the opening / closing timing of the exhaust port are determined in accordance with the exhaust gas temperature determined according to the combustion state of the engine. There is a problem that the chamber effect can be obtained only in the engine rotation range, and the engine output decreases. Further, in the prior art, since a structure for merely providing an opening for introducing outside air is provided at a predetermined position of a hood covering an engine and a chamber of a snowmobile, the inside of the hood is affected by the vehicle speed of the snowmobile, the outside air temperature, and the like. As a result, the exhaust temperature changes and the exhaust temperature changes too high or too low, so that the chamber effect cannot be obtained at the set tuning speed.
There was a problem that the engine output decreased. For example,
As shown in FIGS. 14 and 15, when the exhaust gas temperature is high or when the exhaust gas temperature is low, the speed of the pressure wave propagating in the chamber also changes, and the reflected pulse becomes “EC” at the tuning speed.
, Which caused the engine output to drop.

[0005]

An object of the present invention is to improve the disadvantages of the above conventional example, and in particular, to control the exhaust gas to an optimum temperature to stabilize the combustion state of the engine and obtain a high output. It is an object of the present invention to provide a vehicle exhaust temperature control device.

[0006]

According to the present invention, there is provided a ventilator disposed on a hood for covering a two-stroke engine, an exhaust pipe and the like mounted on a vehicle and for introducing outside air into the hood.
An on-off valve disposed in the ventilator for adjusting the amount of outside air introduced by the ventilator, on-off valve driving means for driving the on-off valve, rotation speed detection means for detecting an engine speed, and an exhaust gas temperature in the exhaust pipe. Temperature detection means for detecting the temperature of the outside air introduced by the ventilator, and the on-off valve preset in advance corresponding to various engine speeds, exhaust temperatures and outside air temperatures. Storage means for storing the degree of opening, wherein the optimum degree of opening of the on-off valve corresponding to the engine speed, exhaust temperature and outside air temperature detected by the respective detecting means is read from the storage means. And an opening / closing valve control function for controlling the operation of the opening / closing valve driving means so that the opening degree of the opening / closing valve detected by the opening / closing valve opening detection means becomes the optimum opening degree. It has a configuration having a unit. This aims to achieve the above-mentioned object.

[0007]

According to the present invention, when the vehicle is running, the engine speed is detected by the speed detecting means, the exhaust temperature in the exhaust pipe is detected by the exhaust temperature detecting means, and the outside air introduced into the ventilator is detected by the outside temperature detecting means. When the temperature is detected, the control means reads from the storage means the optimum opening of the on-off valve corresponding to the detected engine speed, exhaust temperature, and outside air temperature. Then, the control means controls the operation of the on-off valve driving means so as to control the opening of the on-off valve of the ventilator to the optimum opening. That is, in order to control the opening degree of the on-off valve in the ventilator for introducing outside air provided in the hood of the vehicle to be an optimum opening degree corresponding to each engine speed, the exhaust temperature and the outside air temperature, the hood is controlled from outside the vehicle. The amount of outside air introduced into the inside of the exhaust pipe can be accurately adjusted, thereby controlling the exhaust gas temperature inside the exhaust pipe to be an optimum temperature. As a result, the combustion state of the engine can be stabilized, and the output of the engine can be improved.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment and a second embodiment to which the vehicle exhaust temperature control device of the present invention is applied will be described with reference to the drawings.

(1) First Embodiment First, the configuration of the main part of the snowmobile in the first embodiment is shown in FIG.
The hood 2 that covers the front part of the snowmobile 1
, A two-cycle engine 7 having a cylinder part 3, a crankcase part 4, a carburetor 5, and an air cleaner 6, and a chamber 8 arranged in a bent state in a substantially V shape.
, A second muffler 9 and a ventilator 11 having an on-off valve 10 which is opened and closed by an on-off valve controller 22 (see FIG. 1).
In the figure, reference numeral 12 denotes a caterpillar for driving a snowmobile, reference numeral 13 denotes a ski for sliding on snow (on ice), reference numeral 14 denotes a wind cap, and reference numeral 1
Reference numeral 5 denotes a steering handle.

A chamber 8 is connected to an exhaust port (not shown) of the cylinder unit 3, and a second muffler 9 is connected to the chamber 8.
Exhaust gas generated in the chamber 8 and the second muffler 9
, The air is exhausted to the outside of the snowmobile through an exhaust hole 2b provided below the hood 2.

As shown in FIG. 3, the ventilator 11 has a vehicle-side opening formed in a central portion in the longitudinal direction having a circular cross section and an opening 2a formed in a front upper surface of the hood 2. 11a, and a vehicle interior opening 11b that opens to the outer peripheral side of the bent portion of the chamber 8;
Outside air is introduced into the hood 2 from outside the vehicle. At the center in the longitudinal direction inside the ventilator 11, a circular on-off valve 10 fitted to the inner peripheral portion of the ventilator 11 is provided.
Is disposed via a mounting shaft 16 fixed to the diameter portion by screws 17 and 18.

As shown in FIG. 4, the mounting shaft 16 of the on-off valve 10 is fixed to a support member 20 via a nut 19, and a wire 21 is connected to the support member 20.
The wire 21 is a rotating member 23 of the on-off valve controller 22.
Are connected so as to be able to be wound up / out. The on-off valve controller 22 is connected to the wiring 25 from the electronic control unit 24.
By rotating the rotating member 23 in a predetermined direction and winding / unwinding the wire 21 based on the opening / closing command output through the
Is opened and closed.

An engine speed pickup 26 for detecting the engine speed is provided in the crankcase section 4, and an exhaust temperature sensor 27 for detecting the exhaust temperature is provided inside the chamber 8. Inside,
An intake air temperature sensor 28 for detecting the intake air temperature and an opening sensor 29 for detecting the opening of the on-off valve 10 are provided.

Next, the configuration of the control system around the engine, chamber and ventilator in the first embodiment will be described with reference to FIG.
An exhaust temperature sensor 27 outputs a signal corresponding to the detected exhaust temperature inside the chamber 8, and an intake air temperature sensor 28 outputs a signal corresponding to the detected intake air temperature inside the ventilator 11. , Opening sensor 29
Supplies a signal corresponding to the detected opening degree of the on-off valve 10 of the ventilator 11 to the electronic control unit 24.

The electronic control unit 24 includes a ventilator 1 adapted to each engine speed, each exhaust temperature, and each intake temperature.
Data relating to the optimal opening of the on-off valve 10 is stored in a map (storage means) in advance, and the optimal opening of the on-off valve 10 adapted to the engine speed, exhaust temperature, and intake air temperature detected during running on a snowmobile is calculated. A command signal read from the map and corresponding to the optimum opening is output to the on-off valve controller 22. Accordingly, the on-off valve controller 22
The opening of the on-off valve 10 of the ventilator 11 is adjusted so as to be an optimum opening. As a result, the inside of the chamber 8 is controlled to have an optimal exhaust temperature.

FIG. 5 is a graph showing the exhaust gas temperature and the engine output (PS) characteristics at various rotational speeds when the ventilator of the snowmobile is fully opened, half open, and fully closed. When the ventilator runs in the fully closed state, the output peaks at 8500 [rpm] (tuning speed), the exhaust temperature is relatively high , and when the ventilator runs at the half opening state, the exhaust temperature is low overall. the outputs of the peak -
Speed during click dropped to 8000 [rpm], the running result exhaust temperature at full open state ventilator more generally below
Rotational speed during rising output peak low below into 7500 [rpm]
It indicates that you want to.

Therefore, in the first embodiment, the exhaust temperature and the engine output characteristics as shown by the thick solid line in the figure are obtained by changing the opening of the on-off valve 10 of the ventilator 11 for each engine speed. It has become. That is, the opening degree of the on-off valve 10 of the ventilator 11 is controlled to adjust the outside air introduced into the hood 2 from the outside of the snow vehicle, and the exhaust temperature of the chamber 8 is adjusted to the optimum temperature at each engine speed. Thus, the efficiency of charging the air-mixed fuel from the carburetor 5 to the cylinder unit 3 is increased, and a high output is obtained from the engine 7.

Next, the operation of the first embodiment configured as described above will be described.

When the snowmobile 1 travels, the exhaust gas generated in the cylinder section 3 due to the driving of the engine is exhausted from the exhaust hole 2b to the outside of the vehicle through the chamber 8 and the second muffler 9. At this time, the engine speed pickup 26 detects the engine speed, the exhaust temperature sensor 27 detects the exhaust temperature inside the chamber 8, the intake temperature sensor 28 detects the intake temperature inside the ventilator 11, and the opening degree sensor 29. Opening / closing valve 1 of ventilator 11
0 is detected and each detection signal is transmitted to the electronic control unit 2
4 respectively.

The electronic control unit 24 reads from the map the optimal opening of the on-off valve 10 of the ventilator 11, which is suitable for the engine speed, the exhaust temperature, and the intake air temperature during running on a snowmobile, and issues a command signal corresponding to the optimal opening. Output to the on-off valve controller 22. Thereby, the on-off valve controller 22
By rotating the rotating member 23 in a predetermined direction and appropriately winding / unwinding the wire 21, the opening of the on-off valve 10 becomes the optimum opening via the support member 20 and the mounting shaft 16. Adjust to

Thus, the outside air of an amount corresponding to the optimal opening of the on-off valve 10 of the ventilator 11 is introduced from the outside of the snow vehicle to the chamber 8 side, so that the exhaust temperature of the chamber 8 is optimized at the engine speed. It is possible to control so that the exhaust gas temperature becomes high.

In this case, FIG. 6 shows the engine speed and the engine speed when the chamber with a ventilator according to the first embodiment is used, and when the high-speed and low-speed engine chambers according to the prior art are used. It is a characteristic diagram showing the relationship with the output, in the conventional example high output can only be obtained in a specific engine rotation range,
In the first embodiment, it is clear that high output can be obtained in a wide engine rotation range.

As described above, according to the first embodiment,
By controlling the degree of opening of the on-off valve 10 of the ventilator 11 according to each engine speed, the amount of outside air introduced into the hood 2 from outside the snowmobile is accurately adjusted, and the exhaust temperature of the chamber 8 is adjusted to the optimum temperature. As a result, the filling efficiency of the air-mixed fuel from the carburetor 5 to the cylinder unit 3 is increased, thereby making it possible to stabilize the combustion state of the engine. As a result, it is possible to improve the engine output more than before. It becomes possible. Further, it is possible to exert a chamber effect that an appropriate pressure vibration is obtained in the chamber 8 in a wide engine rotation range. Furthermore, since the same or higher performance can be exhibited without using an expensive variable valve as in the related art, the cost can be reduced.

In this case, in the first embodiment, the ventilator 11 has the shape shown in FIG.
7, the cross-sectional shape of the ventilator 31 is rectangular, the planar shape of the on-off valve 32 is rectangular, and the upper end of the on-off valve 32 is an on-off valve, as shown in FIG. Mounting shaft 3 rotated by controller
3 may be fixed. As shown in FIG. 8, for example, the cross-sectional shape of the ventilator 34 is rectangular, the planar shape of the on-off valve 35 is rectangular, and the central portion in the longitudinal direction of the on-off valve 35 is mounted on the mounting shaft rotated by the on-off valve controller. 36.

Further, in the first embodiment, a plurality of hot-wire heaters are fixed to the outer peripheral portion of the chamber 8 at a predetermined interval so as to be wound, and the hot-wire heaters are operated so that the inside of the chamber 8 has an optimum exhaust temperature. It is also possible to do so. As a result, when the exhaust gas temperature of the chamber 8 is reduced, the exhaust gas temperature can be raised to the optimum temperature, so that the combustion state of the engine can be stabilized in the same manner as described above. It is possible to improve the engine output more than before.

(2) Second Embodiment First, the configuration of the main part of the snowmobile in the second embodiment is shown in FIG.
11, a two-cycle engine 47 having a cylinder part 43, a crankcase part 44, a carburetor 45, and an air cleaner 46 is provided inside a hood 42 that covers the front part of the snowmobile 41. A chamber 48 having a plurality of hot-wire heaters 56, a second muffler 49, and a ventilator 51 having, for example, two electric fans 57, 58 are provided. In the figure, reference numeral 52 denotes a caterpillar for driving a snowmobile, reference numerals 53a and 53b denote skis for sliding on snow (on ice), reference numeral 54 denotes a wind cap, and reference numeral 55 denotes a control handle.

A chamber 48 is connected to an exhaust port (not shown) of the cylinder 43, and a second muffler 49 is connected to the chamber 48. Through a second muffler 49, the air is exhausted to the outside of the snowmobile from an exhaust hole 42b provided below the hood 42. A plurality of hot wire heaters 56
Are fixed in a wound state at predetermined intervals. Hot wire heater 5
6 is operated by a heater controller 66 (see FIG. 9).

The ventilator 51 has a vehicle-side opening 51a formed in an opening 42a formed in a front upper surface of the hood 42 and having a longitudinally central cross-section formed, for example, in a substantially elliptical shape. 48 are provided at the inside of the ventilator, and electric fans 57, 58 for introducing outside air into the hood 42 from outside the vehicle are disposed in the central portion in the longitudinal direction inside the ventilator. I have. The electric fans 57 and 58 are driven to rotate by an electric fan controller 65 (see FIG. 9). In this case, the shape of the ventilator 51 is not limited to the above shape.

An engine speed pickup 60 for detecting the engine speed is provided in the crankcase 44, and an exhaust temperature sensor 61 for detecting the exhaust temperature is provided inside the chamber 48. Inside, an outside air temperature sensor 62 for detecting outside air temperature is provided,
The throttle body of the carburetor 45 is provided with a throttle sensor 63 for detecting the opening of the throttle valve.

Next, the configuration of a control system around the engine, chamber and electric fan in the second embodiment will be described with reference to FIG. 9. The engine speed pickup 60 outputs a signal corresponding to the detected engine speed. The exhaust temperature sensor 61 has a signal corresponding to the detected exhaust temperature inside the chamber 48, the outside air temperature sensor 62 has a signal corresponding to the detected outside air temperature, and the throttle sensor 63 has a detected throttle valve opening. The signal is sent to the electronic control unit 64
To each other.

The electronic control unit 64 includes electric fans 57 and 58 adapted to each engine speed and each throttle opening.
The optimum rotation time and the optimum operation time of the hot-wire heater 56 are stored in a map (storage means) in advance, and the electric fan 57 adapted to the engine speed, exhaust temperature, outside air temperature, and throttle opening detected when the snowmobile runs. , 58 and the optimal operation time of the hot-wire heater 56 are read from the map, and command signals corresponding to the optimal rotation time and the optimal operation time are output to the electric fan controller 65 and the heater controller 66. Accordingly, the electric fan controller 65 controls the rotation of the electric fans 57 and 58, and the heater controller 66
The operation of is controlled. Thus, the inside of the chamber 48 is controlled so as to have an optimal exhaust temperature.

That is, in the second embodiment, the electric fan 5
The hood 42 of the snowmobile 41 is controlled by appropriately controlling the rotation of
By adjusting the amount of outside air introduced into the interior and appropriately controlling the operation of the hot-wire heater 56 to warm the chamber 48 to an optimum temperature, a stable engine output can be obtained particularly in a wide rotation range such as a middle rotation range or a low rotation range. It has become.

Next, the operation of the second embodiment configured as described above will be described.

For example, when the snowmobile 41 is traveling on a snowy road in a deep snow condition and the vehicle speed is not sufficient despite the fact that the engine is driven in a high speed range, the temperature inside the hood 42 rises because the temperature inside the hood 42 rises. The exhaust temperature inside 48 also increases. At this time, the engine speed is detected by the engine speed pickup 60, the exhaust temperature is detected by the exhaust temperature sensor 61, the outside temperature is detected by the outside temperature sensor 62, the throttle valve opening is detected by the throttle sensor 63, Each detection signal is supplied to the electronic control unit 64.

The electronic control unit 64 reads, from the map, the optimum rotation time of the electric fans 57 and 58 adapted to the engine speed, the exhaust temperature, the intake air temperature, and the throttle opening detected at the time of running on the snowmobile, and corresponds to the optimum rotation time. The command signal is output to the electric fan controller 65. Accordingly, the electric fan controller 65 controls the electric fans 57,
58 is driven to rotate. As a result, outside air is sufficiently introduced into the hood 42 of the snowmobile 41,
The internal exhaust temperature drops to an optimum temperature, and as a result, it becomes possible to obtain a sufficient engine output.

On the other hand, for example, when the snowmobile 41 is traveling on a snowy road or ice in a compact snow condition and the vehicle speed is high enough, the temperature inside the hood 42 is too low and the exhaust temperature inside the chamber 48 is also low. I do. At this time, the engine speed is detected by the engine speed pickup 60, the exhaust temperature is detected by the exhaust temperature sensor 61, the outside temperature is detected by the outside temperature sensor 62, the throttle valve opening is detected by the throttle sensor 63, Each detection signal is supplied to the electronic control unit 64.

The electronic control unit 64 reads, from the map, the optimal operation time of the hot-wire heater 56 suitable for the engine speed, exhaust temperature, intake air temperature, and throttle opening detected during running on a snowmobile, and issues a command corresponding to the optimal operation time. A signal is output to the heater controller 66. Along with this, the heater controller 66 operates the hot-wire heater 56. As a result, the chamber 48 is appropriately warmed, so that the exhaust temperature inside the chamber 48 rises to an optimum temperature, and as a result, a sufficient engine output can be obtained.

As described above, according to the second embodiment,
Electric fan 5 according to engine speed and throttle opening
Since the exhaust temperature of the chamber 48 is controlled to be an optimum temperature by rotating and driving the hot wire heaters 7 and 58 or the hot wire heater 56, regardless of the running conditions of the snowmobile 41, the carburetor 45 and the cylinder unit 43 can be controlled. The charging efficiency of the air-mixed fuel is increased, which makes it possible to stabilize the combustion state of the engine, and as a result, the engine output can be improved as compared with the conventional case. Further, it is possible to obtain a chamber effect that an appropriate pressure vibration is obtained in the chamber 48 in a wide engine rotation range.

[0039]

As described above, according to the vehicle exhaust temperature control apparatus of the present invention, the opening degree of the on-off valve in the ventilator for introducing outside air, which is disposed on the hood of the vehicle, is controlled by the engine speed and the exhaust temperature. In order to accurately control the amount of outside air introduced from the outside of the vehicle into the hood, the exhaust temperature inside the exhaust pipe is adjusted to the optimum temperature according to each engine speed. As a result, it is possible to stabilize the combustion state of the engine and to achieve an excellent effect that the engine output can be improved.

Further, in the vehicle exhaust temperature control apparatus of the present invention, even when an electric fan for adjusting the amount of outside air introduced is provided in the ventilator, the amount of outside air introduced into the hood from outside the vehicle can be accurately adjusted. As described above, it is possible to control the exhaust temperature inside the exhaust pipe to be an optimum temperature according to each engine speed as described above, and as a result, it is possible to stabilize the combustion state of the engine And the engine output can be improved.
The effect described above can be achieved.

In the vehicle exhaust temperature control apparatus of the present invention, when a hot-wire heater is provided on the outer peripheral portion of the exhaust pipe, and the hot-wire heater is operated for a predetermined time when the exhaust temperature in the exhaust pipe drops, Even when the exhaust gas temperature in the exhaust pipe decreases due to the temperature decrease in the hood, the exhaust gas temperature in the exhaust pipe can be raised to the optimum temperature by operating the hot-wire heater to heat the exhaust pipe. It is possible to stabilize the combustion state of the engine and to improve the engine output.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an exhaust gas temperature control system according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram showing a configuration of a main part of the snowmobile in the first embodiment.

FIG. 3 is a perspective view illustrating a configuration of a ventilator according to the first embodiment.

FIG. 4 is an explanatory diagram showing a configuration of an electronic control unit, an on-off valve controller, and an on-off valve in the first embodiment.

FIG. 5 is a diagram showing a relationship between an open / close state of a ventilator, an exhaust gas temperature, and an engine output.

FIG. 6 is a diagram showing a relationship between an engine speed and an engine output when a chamber with a ventilator and a high-speed / low-speed type chamber are used.

FIG. 7 is a perspective view showing a configuration of a ventilator according to a modification.

FIG. 8 is a perspective view showing a configuration of a ventilator according to another modification.

FIG. 9 is a block diagram illustrating a configuration of an exhaust gas temperature control system according to a second embodiment.

FIG. 10 is a schematic diagram showing a configuration of a main part of a snowmobile according to a second embodiment.

FIG. 11 is a schematic view showing an arrangement state of the electric fans in FIG. 10;

FIG. 12 is an explanatory diagram showing an attached state of a two-cycle engine and a chamber.

FIG. 13 is an explanatory diagram showing a relationship between exhaust pressure and pressure vibration.

FIG. 14 is an explanatory diagram showing a relationship between exhaust pressure and pressure oscillation when the exhaust temperature is high.

FIG. 15 is an explanatory diagram showing the relationship between exhaust pressure and pressure oscillation when the exhaust temperature is low.

[Explanation of symbols]

1,41 Snowmobile as a vehicle 2,42 Hood 7,47 Engine 8,48 Chamber as an exhaust pipe 10 Open / close valve 11,31,34,51 Ventilator 22 Open / close valve controller as open / close valve driving means 24,64 Control means Electronic control unit 26, 60 Engine speed pickup as rotation speed detecting means 27, 61 Exhaust temperature sensor as exhaust temperature detecting device 28 Intake air temperature sensor as outside air temperature detecting device 29 Opening sensor 56 Hot wire heater 62 Outside air temperature Outside temperature sensor as detecting means 63 Throttle sensor as throttle opening detecting means 65 Electric fan controller as electric fan driving means 66 Heater controller as heater operating means

Claims (4)

(57) [Claims] 1. A ventilator provided in a hood for covering a two-stroke engine and an exhaust pipe mounted on a vehicle for introducing outside air into the hood, and a ventilator provided in the ventilator for adjusting an amount of outside air introduced by the ventilator. Opening / closing valve, opening / closing valve driving means for driving the opening / closing valve, rotation speed detection means for detecting the engine rotation speed, exhaust temperature detection means for detecting the exhaust temperature in the exhaust pipe, and detection of the outside air introduced by the ventilator. An outside air temperature detecting means for detecting a temperature; and a storing means for storing an optimum opening degree of the on-off valve preset corresponding to each of various engine speeds, exhaust temperatures and outside air temperatures. An optimal opening reading function for reading from the storage means an optimal opening of the on-off valve corresponding to the engine speed, exhaust temperature and outside air temperature detected by Degrees is the optimum opening and the closing valve vehicle exhaust temperature adjusting apparatus characterized by comprising a control means having an on-off valve control function of controlling the operation of the drive means so. 2. An exhaust pipe is provided with a hot-wire heater on an outer peripheral portion thereof, and a heater operating means for operating the hot-wire heater is provided, wherein the control means controls the hot-wire heater when the exhaust temperature in the exhaust pipe decreases. 2. The exhaust temperature control device for a vehicle according to claim 1, further comprising a heater control function for controlling an operation of the heater operating means so as to operate the heater for a time. 3. A ventilator disposed on a hood for covering a two-stroke engine, an exhaust pipe and the like mounted on a vehicle, for introducing outside air into the hood, and adjusting an amount of outside air introduced by the ventilator disposed in the ventilator. Electric fan, electric fan driving means for driving the electric fan, rotational speed detecting means for detecting the engine rotational speed, exhaust temperature detecting means for detecting the exhaust temperature in the exhaust pipe, and the outside air introduced by the ventilator. Outside temperature detecting means for detecting a temperature, throttle opening detecting means for detecting an opening of a throttle valve of the engine, various engine speeds,
Storage means for storing an optimum rotation time of the electric fan preset in correspondence with each of an exhaust temperature, an outside air temperature, and a throttle opening, wherein an engine speed detected by each of the detection means, an exhaust temperature, an outside air An optimum rotation time reading function for reading the optimum rotation time of the electric fan corresponding to the temperature and the throttle opening from the storage means, and an operation of the electric fan drive means for rotating the electric fan for the optimum rotation time. An exhaust temperature control device for a vehicle, comprising: a control unit having an electric fan control function for controlling. 4. An exhaust pipe is provided with a hot-wire heater on an outer peripheral portion thereof, and a heater operating means for operating the hot-wire heater is provided, and the control means controls the hot-wire heater to a predetermined value when the exhaust temperature in the exhaust pipe decreases. 4. The exhaust temperature control device for a vehicle according to claim 3, further comprising a heater control function for controlling an operation of the heater operation means so as to operate the heater for a time.