JP4439435B2 - Engine intake system - Google Patents

Description

  The present invention relates to an engine intake device, and more particularly to an engine intake device that can perform a smooth start when warming up and restarting.

As shown in FIG. 8 to FIG. 11, some conventional engine intake devices have the following premise configuration as in the present invention.
As shown in FIG. 8, the choke valve shaft (2) is linked to the bimetal (not shown), the engaging portion (3) is fixed to the choke valve shaft (2), and the choke valve shaft (2) is fixed. The rotating body (4) is pivotally supported so that the rotating body (4) is provided with a locking portion (5), and the locking portion (5) is connected to the engaging portion (3) in the choke valve opening direction ( 6) Facing from the upper side, the rotating body (4) is linked to the negative pressure operating part (8) of the negative pressure actuator (7), and the negative pressure operating part (8) is connected to the negative pressure chamber (9). The negative pressure operating portion (8) is urged by the return spring (10) in the urging direction (12) opposite to the negative pressure operating direction (11), and the negative pressure chamber (9) is throttled. It communicates with the valve downstream (13).

  As shown in FIG. 8, at the start of cold start, the negative pressure operating portion (8) is stopped at the biasing position (8b) opposite to the negative pressure operating position (8a) by the biasing force of the return spring (10). As a result, the rotating body (4) is held in the starting start posture (4b) and the bimetal (1) maintains the cold shape so that the locking portion (5) and the engaging portion (3) are mutually connected. The choke valve (14) is in a fully closed position so as not to interfere.

  As shown in FIG. 9, at the completion of the start when the engine speed exceeds a predetermined speed, the negative pressure operating portion (8) is moved to the biased position (8) based on the negative pressure generated downstream of the throttle valve (13). 8b) to the negative pressure operating position (8a), and the operation of the negative pressure operating portion (8) rotates the rotating body (4) from the start start posture (4b) to the start completion posture (4a). The engaging portion (3) engaged with the locking portion (5) is moved in the choke valve opening direction (6) by the rotation of the rotating body (4), and the choke valve (14 is moved by the movement of the engaging portion (3). ) Is opened from a fully closed position to a valve opening position of a predetermined opening, and then the choke valve (14) is gradually opened to a fully opened position by thermal deformation of the bimetal (1) over time.

  During normal operation after warming up, the negative pressure operating position (8a) of the negative pressure operating section (8) is maintained based on the negative pressure generated downstream of the throttle valve (13), and the bimetal (1) is By maintaining the warm shape, the fully open posture of the choke valve (14) is maintained.

  In this type of apparatus, as shown in FIG. 9, when the start is completed, the choke valve (14) is immediately brought into a half choke posture by the negative pressure actuator (7), and thereafter, the choke valve (14) is moved due to thermal deformation of the bimetal. There is an advantage that the valve can be gradually opened and a smooth start can be performed.

  However, in the above conventional engine intake system, as shown in FIG. 11, the bimetal still maintains the warm shape when the warm-up restart is started within a predetermined time from when the engine is stopped. The valve (14) maintains the fully open position.

The above prior art has the following problems.
<Problem> Smooth start-up cannot be performed during warm-up restart.
As shown in FIG. 11, the choke valve (14) is kept fully open at the start of warm-up restart that is performed within a predetermined time from when the engine is stopped, so that the mixture concentration necessary for starting can be obtained. Therefore, a smooth start cannot be performed.

  An object of the present invention is to provide an engine intake device that can solve the above-described problems, that is, an engine intake device that can perform a smooth start at the time of warm-up restart.

The prerequisite structure of the invention according to claim 1 is as follows.
As illustrated in FIG. 6, the choke valve shaft (2) is interlocked and connected to the bimetal (1), and as shown in FIG. 1, the engaging portion (3) is fixed to the choke valve shaft (2). The rotating body (4) is pivotally supported on the choke valve shaft (2), and a locking portion (5) is provided on the rotating body (4). The locking portion (5) is connected to the engaging portion ( 3) facing the choke valve opening direction (6) from the upper side, the rotating body (4) is linked to the negative pressure operating part (8) of the negative pressure actuator (7), and this negative pressure operating part (8 ) Is exposed to the negative pressure chamber (9), and the negative pressure operating portion (8) is urged by the return spring (10) in the urging direction (12) opposite to the negative pressure operating direction (11). The negative pressure chamber (9) communicates with the throttle valve downstream (13).

  As illustrated in FIG. 1, at the start of cold start, the negative pressure operating portion (8) is stopped at the biasing position (8b) opposite to the negative pressure operating position (8a) by the biasing force of the return spring (10). As a result, the rotating body (4) is held in the starting start posture (4b), and the bimetal (1) maintains the cold shape so that the locking portion (5) and the engaging portion (3) are mutually connected. The choke valve (14) is in a fully closed position so as not to interfere with the valve.

  As illustrated in FIG. 2, at the completion of starting when the engine speed exceeds a predetermined speed, the negative pressure operating portion (8) is moved to the biasing position based on the negative pressure generated downstream of the throttle valve (13). (8b) to the negative pressure operating position (8a), and by the operation of the negative pressure operating portion (8), the rotating body (4) is rotated from the start start posture (4b) to the start completion posture (4a), The engaging portion (3) engaged with the locking portion (5) is moved in the choke valve opening direction (6) by the rotation of the rotating body (4), and the choke valve ( 14) is opened from the fully closed position to the open position with a predetermined opening, and then the choke valve (14) is gradually opened to the fully open position by thermal deformation of the bimetal (1) over time. .

  As illustrated in FIG. 3, during the normal operation after warming up, the negative pressure operating position (8a) of the negative pressure operating section (8) is maintained based on the negative pressure generated downstream of the throttle valve (13). At the same time, the bimetal (1) maintains the warm shape so that the choke valve (14) is kept fully open.

The present invention has the following characteristic configuration in the above-described engine intake system.
As illustrated in FIG. 1, the second engagement portion (15) is fixed to the choke valve shaft (2), and the second engagement portion (15) is connected to the locking portion (5) in the choke valve opening direction. (6) By facing from the upper side,
As illustrated in FIG. 4, when the engine is stopped, the negative pressure operating portion (8) is moved from the negative pressure operating position (8a) to the urging position (8b) by the urging force of the return spring (10). The rotating body (4) is rotated from the starting completion posture (4a) to the starting start posture (4b) by the movement of the operating portion (8), and the rotation of the rotating body (4) causes the elasticity of the bimetal (1) during warming. While resisting the restoring force, the second engaging portion (15) engaged with the locking portion (5) is moved in the choke valve closing direction (16), and the movement of the second engaging portion (15) Close the choke valve (14) from the fully open position to the open position of a predetermined opening;
As illustrated in FIG. 4, when the warm-up restart is started within a predetermined time from when the engine is stopped, the second engagement portion (15) is locked by the elastic restoring force of the bimetal (1) during the warm time. The open state of the choke valve (14) when the engine is stopped is maintained while being in pressure contact with the part (5).

(Invention according to Claim 1)
<Effect> Smooth start-up can be performed when warm-up is restarted.
As illustrated in FIG. 1, the second engagement portion (15) is fixed to the choke valve shaft (2), and the second engagement portion (15) is connected to the locking portion (5) in the choke valve opening direction. (6) By facing from the upper side, as illustrated in FIG. 4, when the engine is stopped, the choke valve (14) is closed from the fully open state to the valve opening posture of the predetermined opening degree, At the start of warm-up restart in time, the engine is stopped while the second engagement portion (15) is kept in pressure contact with the locking portion (5) by the elastic restoring force of the bimetal (1) during warm-up. Since the open state of the choke valve (14) is maintained, the air-fuel mixture concentration required for starting can be obtained, and smooth starting can be performed.

(Invention according to Claim 2)
In addition to the effect of the invention according to claim 1, the following effect is achieved.
<Effect> It is possible to suppress a problem that the rotation is abnormally reduced during normal operation after warm-up.
As illustrated in FIG. 1, since the second engagement portion (15) is fixed to the choke valve shaft (2), the following problem may newly occur.
That is, as illustrated in FIG. 3, during normal operation after warm-up, the throttle valve (20) is fully opened due to sudden acceleration, or when the throttle valve (20) is fully opened at low rotation, such as when driving on a slope. In this case, the negative pressure generated downstream of the throttle valve (13) decreases, and the negative pressure operating portion (8) is energized from the negative pressure operating position (8a) as in the case of the engine stop exemplified in FIG. It moves toward the position (8b), and the rotary body (4) rotates from the start completion posture (4a) toward the start start posture (4b) by the movement of the negative pressure operating portion (8). 4), the second engaging portion (15) engaged with the locking portion (5) is moved in the choke valve closing direction (16) by rotation of the second engaging portion (15), and the choke valve ( 14) may close from the fully open posture, and in this case, the intake air flow rate becomes insufficient and the rotation abnormally decreases.
However, in the present invention, as illustrated in FIG. 3, when the negative pressure generated downstream of the throttle valve (13) decreases during normal operation after warming up, the check valve (18) is closed. By suppressing the inflow of air from the throttle valve downstream (13) to the negative pressure chamber (9) with the valve, the negative pressure drop in the negative pressure chamber (9) is suppressed, and the rotating body (4) is in the start completion posture. Since the rotation from the start position (4a) to the start position (4b) can be suppressed, the above problem, that is, the choke valve (14) is closed from the fully open position and the rotation is abnormally reduced can be suppressed. it can.

<Effect> It is possible to prevent a trouble that prevents the next start.
With the check valve (18) alone, the negative pressure in the negative pressure chamber (9) does not decrease even after a long time has elapsed after the engine is stopped, and the rotating body (4) remains in the start completion posture (4a) at the start of the next start. ) And the choke valve (14) is greatly opened, so that the starting is disturbed.
Therefore, in the present invention, as illustrated in FIG. 1, a throttle hole (19) is provided in parallel with the check valve (18), and as illustrated in FIG. 13) Since air is introduced into the negative pressure chamber (9) from the throttle hole (19) through the throttle hole (19), the rotating body (4) can be returned to the starting start posture (4b). The trouble which is disturbed can be prevented.

  Embodiments of the present invention will be described with reference to the drawings. FIGS. 1 to 7 are diagrams for explaining an intake device for an engine according to an embodiment of the present invention. In this embodiment, an intake device for a single-cylinder gasoline engine will be described.

The outline of the intake device according to the embodiment of the present invention is as follows.
As shown in FIG. 1, the carburetor (22) is attached to the cylinder head (21), and the intake port (21a) of the cylinder head (21) is communicated with the downstream of the venturi passage (23) of the carburetor (22). An air cleaner (not shown) is connected upstream of (23). A choke valve (14) is provided at the inlet of the venturi passage (23), a throttle valve (20) is provided at the outlet, and a main nozzle (24) is provided at the center. The throttle valve (20) is linked to a speed control lever (not shown) via a mechanical governor (not shown). The choke valve (14) is opened by an auto choke mechanism (25).

The outline of the auto choke mechanism is as follows.
As shown in FIGS. 5 to 7, the auto choke mechanism (25) includes a rotating body (4), a negative pressure actuator (7), a valve chamber (17), a bimetal case (26), and the like. ) Is externally fitted to the choke valve shaft (2), and the negative pressure actuator (7) and the bimetal case (26) are both fixed to the carburetor (22) via the stay (27). The negative pressure actuator (7) communicates with the negative pressure introduction port (30) through the valve chamber (17), and as shown in FIG. 7, the negative pressure introduction port (30) is located at a position facing the intake port (21a). Is arranged. As shown in FIG. 6, the bimetal (1) is accommodated in the bimetal case (26). The bimetal (1) has a mainspring shape, the inner end is fixed to the bimetal case (26), and the outer end is linked to the choke valve shaft (2) via the linkage arm (28). An electric heater (29) is accommodated in the bimetal case (26), and the bimetal (1) is thermally deformed over time by energizing the electric heater (29).

The basic configuration and functions of the auto choke mechanism are as follows.
As shown in FIG. 6, the choke valve shaft (2) is interlocked and connected to the bimetal (1), and the engaging portion (3) is fixed to the choke valve shaft (2) as shown in FIG. A rotating body (4) is pivotally supported on the valve shaft (2), and a locking portion (5) is provided on the rotating body (4). The locking portion (5) is connected to the engaging portion (3). Facing the choke valve opening direction (6) from the upper side, the rotating body (4) is linked to the negative pressure operating part (8) of the negative pressure actuator (7), and the negative pressure operating part (8) is connected. The negative pressure chamber (9) is faced, and the negative pressure operating portion (8) is urged by the return spring (10) in the urging direction (12) opposite to the negative pressure operating direction (11). The chamber (9) is in communication with the throttle valve downstream (13). The negative pressure operating portion (8) is a diaphragm, and includes an output rod (31). A connecting plate (32) is interposed between the rotating body (4) and the output rod (31).

  As shown in FIG. 1, at the start of cold start, the negative pressure operating portion (8) is stopped at the biasing position (8b) opposite to the negative pressure operating position (8a) by the biasing force of the return spring (10). As a result, the rotating body (4) is held in the starting start posture (4b) and the bimetal (1) maintains the cold shape so that the locking portion (5) and the engaging portion (3) are mutually connected. The choke valve (14) is in a fully closed position so as not to interfere.

  As shown in FIG. 2, at the completion of the start when the engine speed exceeds a predetermined speed, the negative pressure operating portion (8) is moved to the biased position (8) based on the negative pressure generated downstream of the throttle valve (13). 8b) to the negative pressure operating position (8a), and the operation of the negative pressure operating portion (8) rotates the rotating body (4) from the start start posture (4b) to the start completion posture (4a). The engaging portion (3) engaged with the locking portion (5) is moved in the choke valve opening direction (6) by the rotation of the rotating body (4), and the choke valve (14 is moved by the movement of the engaging portion (3). ) Is opened from a fully closed position to a valve opening position of a predetermined opening, and then the choke valve (14) is gradually opened to a fully opened position by thermal deformation of the bimetal (1) over time. .

  As shown in FIG. 3, during normal operation after warming up, the negative pressure operating position (8a) of the negative pressure operating section (8) is maintained based on the negative pressure generated downstream of the throttle valve (13). At the same time, the bimetal (1) maintains the warm shape so that the choke valve (14) is kept fully open.

The devices and functions of the auto choke mechanism are as follows.
As shown in FIG. 1, the second engagement portion (15) is fixed to the choke valve shaft (2), and the second engagement portion (15) is connected to the locking portion (5) in the choke valve opening direction ( 6) Let it face from the upper side. As a result, as shown in FIG. 4, when the engine is stopped, the negative pressure operating portion (8) is moved from the negative pressure operating position (8a) to the biasing position (8b) by the biasing force of the return spring (10). The rotary body (4) is rotated from the start completion posture (4a) to the start start posture (4b) by the movement of the negative pressure operating section (8), and the rotation of the rotary body (4) causes the warm bimetal (1). The second engaging portion (15) engaged with the locking portion (5) is moved in the choke valve closing direction (16) while resisting the elastic restoring force of the second engaging portion (15). The movement causes the choke valve (14) to close from a fully open position to a predetermined open position. In addition, when the warm-up restart is started within a predetermined time from when the engine is stopped, the second engagement portion (15) is pressed against the locking portion (5) by the elastic restoring force of the bimetal (1) during the warm time. In this state, the open state of the choke valve (14) when the engine is stopped is maintained. If the bimetal (1) is cooled over a predetermined time, the choke valve (14) is fully closed due to the cold shape of the bimetal (1).

  Further, as shown in FIG. 1, a valve chamber (17) is provided between the negative pressure chamber (9) and the throttle valve downstream (13), and a check valve (18) is provided in the valve chamber (17). When the negative pressure generated in the downstream of the throttle valve (13) decreases during normal operation after warming shown in FIG. 3 in parallel with the throttle hole (19), the check valve (18) By closing the valve and suppressing the inflow of air from the downstream of the throttle valve (13) to the negative pressure chamber (9), the negative pressure reduction in the negative pressure chamber (9) is suppressed, and the rotating body (4) is completely started. The rotation from the posture (4a) to the starting start posture (4b) can be suppressed, and when the engine shown in FIG. 4 is stopped, the negative pressure chamber (9) from the throttle valve downstream (13) through the throttle hole (19). By introducing air into the rotor, the rotating body (4) can be returned to the starting start posture (4b). The check valve (18) is urged in the valve closing direction by a valve spring (33).

It is a cross-sectional top view of the intake device which concerns on embodiment of this invention, and is a thing at the time of a cold start start. This is a cross-sectional plan view when the start is completed. In the same cross-sectional plan view, it is during normal operation after warm-up. The same cross-sectional plan view is when the engine is stopped and when warm-up restart is started. It is a front view of the carburetor used with the air intake device which concerns on embodiment of this invention. It is a vertical side view of the carburetor. It is a rear view of the carburetor. It is a cross-sectional top view of the intake device which concerns on a prior art, and is a thing at the time of a cold start start. This is a cross-sectional plan view when the start is completed. In the same cross-sectional plan view, it is during normal operation after warm-up. The same cross-sectional plan view is when the engine is stopped and when warm-up restart is started.

Explanation of symbols

(1) Bimetal, (2) Choke valve shaft, (3) Engagement part, (4) Rotating body, (4a) Start complete posture, (4b) Start start posture, (5) Engagement Stop, (6) ... Choke valve opening direction, (7) ... Negative pressure actuator, (8) ... Negative pressure operating part, (8a) ... Negative pressure operating position, (8b) ... Energizing position, (9) ... Negative pressure chamber, (10) return spring, (11) negative pressure operating direction, (12) biasing direction, (13) downstream of throttle valve, (14) choke valve, (15) second engagement Joint, (16) ... Choke valve closing direction, (17) ... Valve chamber, (18) Check valve, (19) ... Throttle hole.

Claims (2)

The choke valve shaft (2) is linked to the bimetal (1), the engaging portion (3) is fixed to the choke valve shaft (2), and the rotating body (4) is freely rotatable on the choke valve shaft (2). The locking body (5) is provided on the rotating body (4), and the locking section (5) faces the engagement section (3) from the upper side of the choke valve opening direction (6). The rotating body (4) is linked to the negative pressure operating part (8) of the negative pressure actuator (7), and the negative pressure operating part (8) faces the negative pressure chamber (9). The portion (8) is urged by the return spring (10) in the urging direction (12) opposite to the negative pressure operating direction (11), and the negative pressure chamber (9) is communicated with the throttle valve downstream (13). ,
At the start of the cold machine start, the rotating body (4) is obtained by stopping the negative pressure operating part (8) at the biasing position (8b) opposite to the negative pressure operating position (8a) by the biasing force of the return spring (10). Is held in the starting start posture (4b), and the bimetal (1) maintains the cold shape so that the locking portion (5) and the engaging portion (3) do not interfere with each other. So that the valve (14) is in a fully closed position,
At the completion of starting when the engine speed exceeds a predetermined speed, the negative pressure operating portion (8) is moved from the biasing position (8b) to the negative pressure operating position based on the negative pressure generated downstream of the throttle valve (13). The rotating body (4) is rotated from the starting start posture (4b) to the starting completion posture (4a) by the operation of the negative pressure operating section (8), and the rotating body (4) is rotated. The engagement portion (3) engaged with the locking portion (5) is moved in the choke valve opening direction (6), and the movement of the engagement portion (3) moves the choke valve (14) from the fully closed position to a predetermined position. After opening the valve to the open position, the choke valve (14) is gradually opened to the fully open position by the thermal deformation of the bimetal (1) over time.
During normal operation after warming up, the negative pressure operating position (8a) of the negative pressure operating section (8) is maintained based on the negative pressure generated downstream of the throttle valve (13), and the bimetal (1) is In the intake system of the engine, in which the choke valve (14) is maintained in the fully open posture by maintaining the warm shape.
The second engaging portion (15) is fixed to the choke valve shaft (2), and the second engaging portion (15) is exposed to the locking portion (5) from the upper side of the choke valve opening direction (6). By not
When the engine is stopped, the negative pressure operating portion (8) is moved from the negative pressure operating position (8a) to the biasing position (8b) by the biasing force of the return spring (10). The rotating body (4) is rotated from the starting completion posture (4a) to the starting start posture (4b), and the rotating body (4) rotates against the elastic restoring force of the bimetal (1) during warming. The second engagement portion (15) engaged with the stop portion (5) is moved in the choke valve closing direction (16), and the movement of the second engagement portion (15) opens the choke valve (14). To a valve opening posture of a predetermined opening,
At the start of warm-up restart, which is performed within a predetermined time from when the engine is stopped, the second engagement portion (15) is brought into pressure contact with the locking portion (5) by the elastic restoring force of the bimetal (1) during warm-up. An engine intake system characterized in that the open state of the choke valve (14) when the engine is stopped is maintained. The engine intake device according to claim 1, wherein
A valve chamber (17) is provided between the negative pressure chamber (9) and the throttle valve downstream (13), and a check valve (18) and a throttle hole (19) are arranged in parallel in the valve chamber (17). And
When the negative pressure generated downstream of the throttle valve (13) decreases during normal operation after warming up, the check valve (18) is closed and the negative pressure chamber (9 ) Suppresses the negative pressure drop in the negative pressure chamber (9), and the rotating body (4) rotates from the start completion posture (4a) to the start start posture (4b). Can be suppressed,
When the engine is stopped, the rotary body (4) can be returned to the starting start posture (4b) by introducing air from the throttle valve downstream (13) through the throttle hole (19) to the negative pressure chamber (9). An air intake device for an engine characterized by that.

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