JPH0631163Y2 - Small engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a small engine that facilitates starting by supplying starting fuel from a starting fuel chamber to a carburetor.

[Conventional technology]

2. Description of the Related Art Conventionally, as a small engine used for a brush cutter, a chain saw, or the like, one provided with an auto choke is known (see, for example, Japanese Patent Laid-Open No. 64-66455). In other words, in this type of small engine, starting fuel is stored in the starting fuel chamber in advance by manually operating the priming pump, and this starting fuel is supplied to the intake passage of the carburetor at the time of starting to generate a rich mixture. It is installed in the cylinder to facilitate starting. On the other hand, when the engine is warming up (30 ℃ -40 ℃)
If the starting fuel is supplied to the above, the spark plug fogging phenomenon is caused and the startability is deteriorated. Therefore, in the above-described prior art, the temperature of the engine cover is sensed by the temperature switch, and when the engine cover reaches or exceeds the set temperature, the supply of the starting fuel is stopped.

[Problems to be solved by the device]

However, in the above prior art, the engine cover and the temperature switch are exposed to the outside. Therefore, since the engine cover and the temperature switch have large heat radiation,
The temperature rise is significantly delayed compared to the cylinder. Therefore,
Even though the temperature in the cylinder is rising, since a rich mixture is supplied to the cylinder, the spark plug fogging phenomenon cannot be prevented.

Further, at the time of warm-up restart, the temperature switch having a small heat capacity cools much faster than the cylinder, so that a rich air-fuel mixture is supplied to the cylinder despite the engine being warmed up. Therefore, the fogging phenomenon of the spark plug cannot be prevented again.

In particular, when the outside air temperature is low, or when rainwater or wind hits the temperature switch or the like, the above-described fogging phenomenon may occur.

Therefore, there is known a technique in which a heat-sensitive actuator is fitted in a fitting hole provided in the cylinder, the temperature rise of the cylinder is detected, and the valve body of the actuator is used to close the fuel passage for starting the carburetor (actual opening 60-72954). issue). According to this technique, the actuator does not cool down much faster than the cylinder, but since the actuator extending from the cylinder to the carburetor is required, the size of the actuator becomes large.

The present invention has been made in view of the above-described conventional problems, and in a small engine that supplies starting fuel to a carburetor, it is possible to quickly stop the supply of starting fuel at the time of warming up, and at the time of restarting warming up. An object of the present invention is to provide a small engine that can keep the supply of starting fuel stopped and that can use a small actuator.

[Means for Solving the Problems]

In order to achieve the above object, in the present invention, first, a heat guide plate that transfers heat of the cylinder is attached to the engine, and the heat sensitive part is in contact with the heat guide plate. The contact portion of the heat guide plate with the heat sensitive portion and the heat sensitive portion are covered with a resin cover that suppresses heat radiation from the contact portion and the heat sensitive portion. When the temperature of the heat-sensitive part exceeds the set temperature, the actuator operates the valve element to close the starting fuel outlet passage.

[Action]

According to this invention, since the contact portion and the heat-sensitive portion of the heat guide plate are covered with the resin cover, the amount of heat radiation is small, so the temperature rises quickly as the engine warms up, and the warm-up restart is performed. Excellent heat retention. Furthermore, since the heat of the cylinder is introduced to the actuator by the heat guide plate,
The size of the actuator can be reduced as compared with the case of providing the actuator that extends over the cylinder and the carburetor.

〔Example〕

 An embodiment of the present invention will be described below with reference to the drawings.

1 to 4 show a first embodiment.

In FIG. 1, a recoil starter 11 and a shroud 12 are provided above the fuel tank 10 below the engine. The shroud 12 is made of a resin such as nylon or polybutylene terephthalate (PBT),
It covers a cylinder (not shown). On the left side of the shroud 12, that is, on the left side of the cylinder, an air cleaner 13 and a carburetor 14 are located, while the shroud 12
A muffler cover 15 is arranged on the right side of 12.

FIG. 2 is a sectional view taken along line II-II in FIG. As shown in FIG. 2, an actuator holder 16 and a priming pump P are fixed in front of the carburetor 14. The priming pump P is made of rubber and has a cap shape. The actuator holder 16 is provided with a starting fuel chamber 17.

As shown in FIG. 3, the fuel tank 10 communicates with a diaphragm chamber 18 that sucks fuel by the pulsation of an intake passage 19. The diaphragm chamber 18 communicates with the intake passage 19 of the carburetor 14 via the main fuel passage Fm, and also communicates with the starting fuel chamber 17 via the starting fuel passage Fs.

The starting fuel chamber 17 communicates with the intake passage 19 via the starting fuel outlet passage Fe, and also has a fuel suction passage.
It communicates with the inside of the priming pump P via Fb. The starting fuel chamber 17 has an air passage for introducing air.
A1 is open. The priming pump P communicates with the fuel tank 10 via a return passage Fr.

The fuel F or the air A (FIG. 2) is allowed to flow only in the direction of the arrow in the starting fuel passage Fs, the starting fuel outlet passage Fe, the fuel suction passage Fb, the return passage Fr and the air passage A1, respectively. A check valve V is provided. As clearly shown in FIG. 2, a valve body 21 for opening and closing the starting fuel outlet passage Fe faces the starting fuel chamber 17.

An actuator 20 that opens and closes the valve body 21 is mounted on the actuator holder 16. This actuator 20, the heat sensitive portion 22 made of a copper container, the valve body 21 is inserted from the opening 23,
Wax (not shown) is enclosed in the heat sensitive portion 22. The actuator 20 may be made of wax pellets (trade name) manufactured by Fuji Thomson Co., Ltd., or may be made of bimetal or shape memory alloy. The heat sensitive portion 22 projects from the actuator holder 16 and is in contact with the heat conducting plate 30.

The heat guide plate 30 is provided on the intake flange 41 of the intake pipe 40 of the cylinder.
And the insulator 42, the mounting portion 31 is sandwiched between the mounting portion 31 and the insulator 42, and the contact portion 32 that projects from the mounting portion 31 and comes into contact with the heat-sensitive portion 22 transmits heat from the cylinder. The contact portion 32 is bent to have a slight spring characteristic, and the heat-sensitive portion is
Abuts 22. The heat-conducting plate 30 is a thin plate of metal having a high thermal conductivity such as copper or aluminum (for example, 0.3 mm to
1,0 mm), with intake flange 41 and insulator 42
There is a seal between

The contact portion 32 and the heat sensitive portion 22 of the heat conducting plate 30 are covered with a resin cover 1A. In the case of this embodiment, the resin cover 1A is integrally formed with the shroud 12 that covers the cylinder, and has a U-shaped cross section as shown in FIG. The contact portion 32 and the heat sensitive portion 22 in FIG. 2 are arranged in front of and close to the insulator 42 made of, for example, a thermosetting resin. Therefore, the contact part
32 and heat-sensitive part 22 are made of resin actuator holder 1
6, the periphery thereof is covered with the cover 1A, the shroud 12, and the insulator 42.

The insulator 42 is provided between the intake flange 41 and the body 43 of the carburetor 14. The heat guide plate 30 is fastened together with the insulator 42 to the intake flange 41 by bolts 44. The insulator 42 above
To the carburetor 14 of FIG. 2 by means of the bolt 50 of FIG.
The body 43 of is fastened.

The insulator 42 has an intake passage for the intake pipe 40.
An intake passage 46 communicating with 45 is provided. The actuator holder 16 is made of, for example, a thermosetting resin.

Next, the operation of the above configuration will be described.

First, when the priming pump P is pushed, the starting fuel F in the diaphragm chamber 18 shown in FIG. 3 is generated by the negative pressure in the pump P.
(FIG. 2) is introduced into the starting fuel chamber 17. The fuel overflowing from the starting fuel chamber 17 is returned to the fuel tank 10 via the priming pump P. Next, when the engine is rotated by pulling the recoil rope, the main fuel and the starting fuel are discharged from the diaphragm chamber 18 and the starting fuel chamber 17 via the main fuel passage Fm and the starting fuel outlet passage Fe, respectively. F (FIG. 2) is supplied to the intake passage 19 of the carburetor 14. As a result, at the time of starting when the temperature of the cylinder is low, the rich mixture M is introduced into the cylinder to facilitate starting.

On the other hand, when the engine is started, the temperature of the intake pipe 40 of the cylinder shown in FIG. 2 rises, and the temperature of the heat conducting plate 30 and the heat sensitive section 22 also rises accordingly. The temperature of the heat sensitive portion 22 is set to a set temperature (for example, 30
(° C-40 ° C) or higher, the wax in the heat-sensitive portion 22 expands, the valve body 21 of the actuator 20 projects into the starting fuel chamber 17, and the starting fuel outlet passage Fe is closed. As a result, the starting fuel F is not supplied when the engine is warmed up.

In the above structure, in this invention, the contact portion 32 and the heat sensitive portion 22 of the heat conducting plate 30 are covered with the resin cover 1A. Therefore, heat radiation from the contact portion 32 and the heat-sensitive portion 22 is suppressed, and rainwater and wind are less likely to hit the heat-sensitive portion 22 and the like, so that the temperature of the contact portion 22 and the heat-sensitive portion 32 rises rapidly as the cylinder temperature rises. Therefore, the supply of the starting fuel F can be promptly stopped as the engine warms up.

Further, since the contact portion 32 and the heat-sensitive portion 22 are covered with the resin cover 1A, the heat-sensitive portion 22 and the like are excellent in heat retention. Therefore, when the engine is warmed up and restarted, the starting fuel F
Can be kept stopped.

Further, since the heat of the cylinder is introduced to the heat-sensitive portion 22 of the actuator 20 by the heat guide plate 30, the actuator 20 can be made smaller than in the case where the actuator that extends over the cylinder and the carburetor 14 is provided.

In particular, in this embodiment, the periphery of the heat sensitive portion 22 and the contact portion 32 is a resin actuator holder 16, a cover 1A,
Since it is covered with the shroud 12 and the insulator 42, the sensitivity and heat retention of the heat-sensitive portion 22 are further improved.

Further, in this embodiment, the mounting portion 31 of the heat conducting plate 30 is inserted between the intake flange 41 and the insulator 42.
Therefore, due to the large fastening force of the bolt 44 that fastens the insulator 42 to the intake flange 41, the heat conducting plate 30 is pressed against the intake flange 41, and the area of the mounting portion 31 of the heat conducting plate 30 is adjusted to match the intake flange 41 having a large area. And the side surface of the heat guide plate 30 opposite to the intake flange 41 is thermally insulated by the insulator 42. Therefore, the heat transfer effect of the heat guide plate 30 associated with the temperature rise of the cylinder is improved, so that the supply of the starting fuel F can be stopped more quickly during warm-up.

Also, in this embodiment, the shroud 12 covering the cylinder is
In addition, since the resin cover 1A is integrally formed, the number of parts does not increase.

5 and 6 show a second embodiment.

In FIG. 5, in this embodiment, the insulator cover 42 is also integrally formed with the resin cover 1B. The resin cover 1B projects from the insulator 42 and covers the upper and lower sides of the heat-sensitive portion 22. The resin cover 1A formed integrally with the shroud 12 covers the heat sensitive portion 22 from the outside of the resin cover 1A.

According to this embodiment, the portion of the gap S formed between the resin cover 1A of the shroud 12 and the insulator 42 can be covered with the resin cover 1B of the insulator 42. Therefore, the sensitivity and heat retention of the heat sensitive section 22 are further improved.

In addition, in the second embodiment, the other configurations are the same as those of the first embodiment.
The same parts as or corresponding parts are designated by the same reference numerals, and description and detailed illustration thereof will be omitted.

By the way, in each of the above embodiments, the resin covers 1A and 1B are integrally formed with the engine shroud 12 or the insulator 42, but it is not always necessary to do so. For example, a resin cover formed separately from the shroud 12 may be fixed to the engine body with bolts or the like.

Further, a resin cover may be provided on the heat conductive plate 30 and the heat sensitive portion 22 by coating except for the heat conductive surface of the heat conductive plate 30 from the engine and the contact surface between the heat conductive plate 30 and the heat sensitive portion 22. That is, the resin cover may be coated on the exposed portions of the heat conductive plate 30 and the heat-sensitive portion 22 without providing the resin covers 1A and 1B.

In each of the above embodiments, the mounting portion 31 of the heat conducting plate 30 of FIG.
However, it was held between the insulator 42 and the intake flange 41, but it is not always necessary to do so. The heat conducting plate 30 is a portion of the cylinder where heat can be sensed, for example, the muffler 15
(FIG. 1) or may be attached to the cylinder body.

[Effect of device]

As described above, according to the present invention, the heat-sensitive part of the actuator that stops the supply of the starting fuel when the temperature exceeds the set temperature and the contact part of the heat-conducting plate attached to the engine are covered by the resin cover. Since it is covered, the temperature of the heat-sensitive part rises quickly as the engine warms up, and the heat-retaining property of the heat-sensitive part at the time of warm-up restart is improved. Therefore, it is possible to quickly stop the supply of the starting fuel at the time of warming up, and it is possible to keep the supply of the starting fuel at the time of restarting the warming up. Moreover, since the heat-sensitive portion and the contact portion are not exposed to the outside, the aesthetic appearance is improved. Further, since the heat of the cylinder is introduced to the actuator by the heat conducting plate, the size of the actuator can be reduced as compared with the case where the actuator extending over the cylinder and the carburetor is provided.

[Brief description of drawings]

FIG. 1 is a front view of a small engine showing a first embodiment of the present invention, FIG. 2 is a sectional view taken along the line II-II of FIG. 1, and FIG. 3 is a schematic configuration diagram showing a fuel supply system. Fig. 4 is IV- in Fig. 2.
FIG. 5 is a cross-sectional view taken along line IV, FIG. 5 is a lateral cross-sectional view of a main part showing the second embodiment, and FIG. 1A, 1B …… resin cover, 14 …… carburetor, 17 …… starting fuel chamber, 19 …… intake passage, 20 …… actuator,
21 ... Valve, 22 ... Heat-sensitive part, 30 ... heat-conducting plate, 32 ... contact part, F ... starting fuel, Fe ... starting fuel outlet passage.

 ─────────────────────────────────────────────────── ─── Continuation of front page (56) Bibliography Sho 60-72954 (JP, U) Sho 56-109642 (JP, U)

Claims (1)

[Scope of utility model registration request] 1. A small engine for supplying starting fuel from a starting fuel chamber to an intake passage of a carburetor through a starting fuel outlet passage, the heat guide plate being mounted on the engine and transmitting heat of a cylinder. An actuator that has a heat-sensitive portion that comes into contact with the heat-conducting plate, operates the valve element to close the starting fuel outlet passage when the heat-sensitive portion exceeds a set temperature, and the heat-sensitive portion of the heat-conducting plate. A small engine provided with a resin cover that covers the contact portion and the heat-sensitive portion to suppress heat radiation from the contact portion and the heat-sensitive portion.