JP4129244B2 - Vaporizer choke valve control device - Google Patents

Description

  According to the present invention, when the engine is started, the choke lever connected to the choke valve is rotated to the closed position corresponding to the fully closed position of the choke valve. After the engine is started, the choke lever is automatically moved in the opening direction of the choke valve. The present invention relates to an improvement of a choke valve control device for a carburetor, which is configured to rotate in a straight line.

In a general carburetor, a choke spring that urges the choke lever in the opening direction and a choke lever that is held in a closed position immediately before starting the engine are automatically operated in cooperation with the choke spring after starting. For example, as disclosed in Japanese Patent Application Laid-Open No. H10-228707, a damper that is connected to a damper that opens slowly is already known.
Japanese Utility Model Publication No. 63-24354

  In the above-mentioned prior art, the choke lever after the engine start is controlled to open slowly by cooperation with the damper together with the choke spring, so that the opening speed is constant, so the choke valve opening is always set to the engine. It cannot be controlled in response to changes in temperature, and it is difficult to satisfy the stability of engine warm-up and low fuel consumption.

  The present invention has been made in view of such circumstances, so that the opening degree of the choke valve can be rationally controlled in response to changes in the engine temperature, so that warm-up operation can be stabilized and fuel consumption can be reduced. It is an object of the present invention to provide a carburetor choke valve control device that can improve the efficiency of the carburetor.

  To achieve the above object, the choke valve control device for a carburetor according to the present invention includes a choke lever connected to the choke valve of the carburetor and spring-biased in the opening direction of the choke valve. A choke closed state holding means for holding the choke lever in the closed position when it is rotated to the closed position corresponding to the closed position, and then releasing the holding of the choke lever by a throttle operation of the vaporizer; and a fixed structure The choke lever released from the choke closed state holding means is restricted to an intermediate position corresponding to the half-open position of the choke valve, and is choked at the high temperature position. A control lever that restricts the lever to the open position corresponding to the fully open position of the choke valve, and urges the control lever toward the low temperature position 1 control spring, which is under the influence of the engine temperature and is in a shape recovery state when the engine temperature reaches a predetermined high temperature, and is a spring force that rotates the control lever to the high temperature position against the biasing force of the first control spring It consists of the 2nd control spring made from a shape memory alloy which exhibits 1st characteristic.

  According to the present invention, in addition to the first feature, the choke closed state holding means is connected to a throttle arm connected to a throttle valve of a carburetor, and is connected to a choke lever. When the choke lever is turned to the closed position when the throttle valve is in the open position corresponding to the fully open position of the throttle valve, the lock lever is configured to be locked to prevent reverse rotation. A governor spring that urges the valve in the opening direction and a governor that generates an output that urges the throttle lever in the closing direction of the throttle valve in response to an increase in the engine speed are connected. The second feature is that the lock arm releases the arm to be locked by rotating in the closing direction.

  The fixed structure corresponds to the support plate 25 in the embodiment of the present invention described later, the control lever corresponds to the third control lever 53, and the governor corresponds to the centrifugal governor 45.

  According to the first feature of the present invention, after the engine is started, the choke lever accompanying the throttle operation is immediately held at the intermediate position corresponding to the half-open state of the choke valve by the control lever occupying the low temperature position. Therefore, since the choke valve can be controlled to a half-open state suitable for warm-up operation immediately after starting, deterioration of fuel efficiency due to delay in opening the choke valve can be avoided.

  At the end of engine warm-up operation, the memory spring control spring immediately exerts its original spring function, and the choke lever is held in the open position using the control lever rotated to a high temperature position. The opening degree of the engine can be rationally controlled in response to changes in the engine temperature, so that both the warm-up operation of the engine and the low fuel consumption can be satisfied. Moreover, the configuration is relatively simple, and the choke valve control device can be provided at a low cost.

  According to the second feature of the present invention, when the engine is started, the throttle lever is automatically rotated in the closing direction from the open position by the operation of the governor. Since the holding is released, the release can be automatically performed. Therefore, the transition to the intermediate position of the choke lever can be performed quickly and the warm-up operation can be started well.

  Embodiments of the present invention will be described below on the basis of preferred embodiments of the present invention shown in the accompanying drawings.

  FIG. 1 is a side view of a power lawn mower equipped with an engine equipped with a choke valve control device according to a first embodiment of the present invention, FIG. 2 is a partially broken plan view of the engine, and FIG. FIG. 4 is an enlarged view of the main part of FIG. 2, FIG. 5 is a sectional view taken along line 5-5 of FIG. 4 (showing the operating state of the braking mechanism), and FIG. FIG. 7 is a view corresponding to FIG. 5 showing the previous state, FIG. 7 is a view taken along arrow 7 in FIG. 6, FIG. 8 is a view corresponding to FIG. FIG. 10 is a view corresponding to FIG. 5, FIG. 10 is a view taken in the direction of the arrow 10 in FIG. 9, FIG. 11 is a view corresponding to FIG. FIG. 12 is a view taken in the direction of arrow 12; FIG. 13 is a view corresponding to FIG. 5 showing a high-temperature stop state of the engine; FIG. FIG. 16 is a sectional view taken along the line 16-16 in FIG. 15, FIG. 17 is an explanatory view of the operation of the choke lever closed position holding means, and FIG. 16 (a) is a sectional view taken along the line aa in FIG. (C) is a sectional view taken along the line cc of FIG. 7, and FIG. 18 is a view corresponding to FIG. 17, showing a second embodiment of the present invention.

  First, the description starts with the description of the first embodiment of the present invention. In FIG. 1, a walking type power lawn mower 1 as a power working machine has a housing 3 supported by a front wheel 2f and a rear wheel 2r. A vertical engine 4 having a crankshaft 5 disposed in the vertical direction is mounted on the upper surface of the housing 3, and a rotary cutting blade 7 attached to the lower end of the crankshaft 5 is disposed in the housing 3. A turf bag 8 is attached to the steering handle 6 coupled to the rear end of the housing 3 so as to store the turf cut by the cutting blade 7.

  2 to 5, a flywheel 9 that also serves as a cooling fan is fixed to the upper end of the crankshaft 5 of the engine 4, and an engine cover 10 that covers the upper surface of the engine 4 together with the flywheel 9 is fixed to the engine 4. The A recoil starter 11 that can drive the crankshaft 5 via a flywheel 9 and a starter cover 12 that covers the starter 11 are attached to the engine cover 10. The starter cover 12 is provided with a large number of cooling air intakes 13. When the flywheel 9, that is, the cooling fan is rotated, cooling air is drawn into the engine cover 10 from the cooling air intakes 13. The wind is guided to each part of the engine 4 by the engine cover 4. In FIG. 2, reference numeral 11 a is a rope pulling grip of the starter 11.

  A brake shoe 16 that cooperates with the cylindrical outer peripheral surface of the flywheel 9 is attached to a bracket 14 fixed to the engine 4 below the flywheel 9 via a pivot 17. The pivot 17 is disposed at a position closer to the inner side than the outer peripheral surface of the flywheel 9.

  The brake shoe 16 includes an arm 16a that extends between the bracket 14 and the flywheel 9 and extends outward from the outer peripheral surface of the flywheel 9, and a pressure contact portion that is bent from the tip of the arm 16a and faces the outer peripheral surface of the flywheel 9. 16b, and a lining 18 is bonded to the pressure contact portion 16b.

  Thus, the brake shoe 16 is released from the braking position A (see FIGS. 4 and 5) where the lining 18 of the pressure contact portion 16b is pressed against the outer peripheral surface of the flywheel 9 and the brake release for separating the lining 18 from the outer peripheral surface. It can be swung around the pivot 17 between the position B (see FIG. 6). A brake spring 19 that biases the brake shoe 16 toward the braking position A is connected to the front end of the pressure contact portion 16 b of the brake shoe 16. The brake shoe 16, the flywheel 9 and the brake spring 19 constitute a braking mechanism 15 that stops the rotation of the crankshaft 5.

  Further, an operating arm 16c is integrally formed on the brake shoe 16, and an operation wire 21 that is pulled by a brake release lever 20 (see FIG. 1) pivotally supported by the steering handle 6 is provided at the tip thereof. Is connected and the operation wire 21 is pulled, the brake shoe 16 can be rotated to the brake release position B via the operating arm 16c.

  As shown in FIG. 4, an engine kill switch 22 is installed on the upper surface of the bracket 14. When the brake shoe 16 reaches the braking position A, the engine kill switch 22 deactivates the engine ignition circuit (not shown) and stops the operation of the engine 4 in conjunction therewith.

  As shown in FIGS. 2 to 4, a carburetor 23 is attached to the left and right sides of the engine 4, an exhaust muffler 26 is attached to the other side, and an air cleaner 24 is connected to the upstream end of the carburetor 23.

  The carburetor 23 includes a carburetor body 30 having an intake passage 30a, a butterfly choke valve 31 that opens and closes an upstream portion of the intake passage 30a, and a butterfly throttle valve 32 that opens and closes the downstream side thereof. Further, the valve shafts 31 a and 32 a of the choke valve 31 and the throttle valve 32 are rotatably supported on the carburetor body 30 in the vertical direction in the same manner as the crankshaft 5 of the engine 4.

  As shown in FIGS. 14 to 16, the valve shaft 31 a of the choke valve 31 is arranged offset to one side from the center line of the intake passage 30 a, and the choke valve 31 is in the fully closed state of the choke valve 31. The side with the larger radius is inclined with respect to the center line of the intake passage 30a so as to come to the downstream side of the intake passage 30a with respect to the side with the smaller radius. A choke lever 33 is attached to an outer end portion of the valve shaft 31a protruding outside the carburetor body 30. The choke lever 33 includes a bottomed cylindrical hub 33a that is rotatably fitted to the valve shaft 31a, and a lever arm 33b that protrudes integrally on one side surface of the hub 33a. Inside the hub 33a, a pair of stopper projections 34, 34 'are formed in the circumferential direction with a certain interval, and a relief lever 35 that is rotatable only between the stopper projections 34, 34' is provided. A relief spring 36 is provided between the hub 33a and the relief lever 35 so as to be fixed to the valve shaft 31a and urged so that the relief lever 35 is brought into contact with one stopper projection 34 located on the closed side of the choke valve 31. It is done.

  A pair of stopper walls 37, 37 ′ are formed on the outer periphery of the lower portion of the hub 33 a so as to be spaced apart from each other in the circumferential direction. A stopper pin 38 disposed between the stopper walls 37, 37 ′ is a carburetor body 30. Projected on the outer surface.

  Thus, when one stopper wall 37 abuts against the stopper pin 38, the closing position C of the choke lever 33 for fully closing the choke valve 31 is defined, and the other stopper wall 37 'abuts against the stopper pin 38. Thus, the opening position O of the choke lever 33 that fully opens the choke valve 31 is defined.

  If the intake negative pressure of the engine exceeds a certain value when the choke valve 31 is fully closed or small, the rotation moment due to the intake negative pressure acting on the larger radius side of the choke valve 31 and the radius of the choke valve 31 are reduced. The difference from the rotational moment due to the intake negative pressure acting on the smaller side overcomes the rotational moment due to the relief spring 36 and increases the opening of the choke valve 31. It is regulated by contacting 34 '.

  4 and 5 again, a throttle lever 40 is fixed to an outer end portion of the valve shaft 32a of the throttle valve 32 protruding outside the carburetor main body 30. The throttle lever 40 is supported by the engine 4. A long arm portion 42 a of the governor lever 42 fixed to the outer end of the rotation support shaft 41 is connected via a link 43. The governor lever 42 is connected to a governor spring 44 that urges the lever 42 with a predetermined load in the opening direction of the throttle valve 32. Further, an output shaft 45 a of a known centrifugal governor 45 driven by the crankshaft 5 of the engine 4 is connected to the short arm portion 42 b of the governor lever 42, and the centrifugal governor 45 increases as the rotational speed of the engine 4 increases. The output acts on the short arm portion 42b in the closing direction of the throttle valve 32. Therefore, when the engine 4 is stopped, the throttle lever 40 is held at the closed position C of the throttle valve 32 by the set load of the governor spring 44. However, during operation of the engine 4, the governor lever 42 by the output of the centrifugal governor 45 is used. The opening degree of the throttle valve 32 is automatically controlled by a balance between this moment and the moment of the governor lever 42 due to the load of the governor spring 44.

  Now, a choke valve control device 27 according to an embodiment of the present invention that automatically opens and closes the choke valve 31 will be described.

  3 to 5, a support plate 25 that is coupled to the bracket 14 and extends in the vertical direction is sandwiched between the vaporizer 23 and the air cleaner 24. First to third control levers 51 to 53 are rotatably attached to the inner surface of the support plate 25 via first to third pivots 54 to 56, respectively, and the second control lever 52 is a first control lever 51. The third control lever 53 is disposed immediately below the second control lever 52.

  The front end of the first control lever 51 extends to the second control lever 52 side, and the base of the first control lever 51 engages and disengages with the front end edge of the release arm 16c when the brake shoe 16 occupies the braking position A. 51a is formed. Connected to the first control lever 51 is a first return spring 57 that urges the claw 51a in the direction of engagement with the release arm 16c. The first control lever 51 pushes the claw portion 51a by rotating the claw portion 51a to the front end of the release arm 16c at the braking position A and the release arm 16c to the brake release position B. The second position E is rotated between the first position E and the second position E.

  The second control lever 52 includes an upper arm portion 52a and a lower arm portion 52b that extend upward and downward, respectively, and a flexible elastic arm portion 52c that extends toward the first control lever 51. ing. The upper arm 52a is provided with an arc-shaped elongated hole 59 concentric with the second pivot 55, and the other end of the link 46 slidably connected to the elongated hole 59 is connected to the choke lever 33. The lever arm 33b is connected to the distal end portion. The elastic arm 52c is pushed by the first control lever 51 when the first control lever 51 is rotated from the first position D to the second position E, and the second control lever 52 is linked to the link 46 by the pushing. The choke lever 33 is rotated toward the closed position C via the.

  The lower arm portion 52 b of the second control lever 52 is formed with a contact wall 60 erected in the axial direction of the second pivot 55, and this contact wall 60 is used as an upper arm portion 53 a of the third control lever 53, which will be described later. A second return spring 58 is provided between the second control spring 67 and the support plate 25 to urge the second control lever 52 to rotate in the direction of contact with the second control lever 52.

  The throttle lever 40 is provided with a lock arm 49 that is flexible in the axial direction of the valve shaft 32a, and a locked arm 50 corresponding to the lock arm 49 is formed integrally with the choke lever 33. The locked arm 50 is held by the lock arm 49 when the choke lever 33 is rotated to the closed position C with the throttle valve 32 fully opened. That is, as shown in FIG. 17, when the throttle lever 40 is in the fully open position, the lock arm 49 intervenes in the rotation path of the locked arm 50, and the rotation direction of the lock arm 49 A slope 61 that is pushed up from the locked arm 50 when the locked arm 50 rotates toward the closed position C of the choke lever 33 is formed on one side, and the locked arm 50 is locked on the other side. Immediately after passing below 49, a contact surface 62 that receives the arm 50 to be locked and holds the choke lever 33 in the closed position C is formed.

  4 and 5 again, the third control lever 53 includes an upper arm portion 53a and a lower arm portion 53b extending above and below the third pivot 56, respectively, and the tip of the upper arm portion 53a is connected to the second control lever 53a. The lever 52 comes into contact with the contact wall 60 of the lower arm portion 52b of the lever 52 from the vaporizer 23 side.

  The support plate 25 is fixedly provided with a stopper member 64 having first and second stopper walls 64a and 64b for receiving the lower arm portion 53b and limiting the rotation angle of the third control lever 53. The position of the third control lever 53 when the lower arm 53b is brought into contact with the first stopper wall 64a on the vaporizer 23 side is referred to as a low temperature position L, and the lower arm 53b is located on the opposite side to the vaporizer 23. 2 The position of the third control lever 53 when brought into contact with the stopper wall 64b is referred to as a high temperature position H.

  Further, a spring locking member 65 arranged on the opposite side of the vaporizer 23 is fixed to the third control lever 53 on the support plate 25. The spring locking member 65 also has an upper arm portion 65a and a lower arm portion 65b corresponding to the upper arm portion 53a and the lower arm portion 53b of the third control lever 53, and a tension coil spring is provided between the upper arm portions 52a and 65a. The both ends of the 1st control spring 66 which consists of are connected, and the both ends of the 2nd control spring 67 which consists of a tension coil spring are connected between lower arm parts 52b and 65b. The set load of the first control spring 66 is set larger than that of the second return spring 58.

  The second control spring 67 is made of a shape memory alloy, and the spring function is lost when the temperature is lower than the shape recovery temperature corresponding to the atmospheric temperature at the end of the warm-up operation of the engine 4. A set load (tensile force) stronger than that of the first control spring 66 is exhibited.

  In the above, the brake release lever 20, the operation wire 21 and the release arm 16c constitute the brake release means 70 for releasing the brake of the brake shoe 16 against the flywheel 9, and the first and second control levers 51, 52 and the link. 46 constitutes an automatic choke closing means 71 that rotates the choke lever 33 to the closed position C in conjunction with the operation of the brake releasing means 70. The lock arm 49 and the arm to be locked 50 close the choke lever 33 to the closed position C. The choke valve closed state holding means 72 is configured to hold the link 46 and the long hole 59 so that the choke lever 33 is held at the closed position C, and then the second control lever 52 is returned by the second return spring 58. A lost motion means 73 that allows movement, a second return spring 58, a third control lever 53, The first stopper wall 64a and the first control spring 66 constitute warm-up control means 74 that holds the choke lever 33 at the half-opening degree of the choke valve 31 immediately after the engine 4 is started, and the third control lever 53, second stopper The wall 64b and the second control spring 67 constitute a choke automatic opening means 75 that rotates the choke lever 33 to the open position O after the warm-up operation of the engine 4 is completed.

  Next, the operation of the first embodiment will be described.

  As shown in FIGS. 3 to 5, when the brake shoe 16 is at the braking position A and the braking force is applied to the flywheel 9 and the engine 4 is stopped, the first control lever 51 is By the urging force of the 1 return spring 57, the claw portion 51a is held at the first position D where it is engaged with the front end edge of the release arm 16c. The second control lever 52 causes the contact wall 60 of the lower arm portion 52 b to contact the tip of the upper arm portion 53 a of the third control lever 53 by the biasing force of the second return spring 58. However, if the engine 4 is in a low temperature state, the ambient temperature is as low as less than the shape recovery temperature of the second control spring 67, so the second control spring 67 has lost its spring function, and therefore the third control lever 53 is Due to the urging force of the first control spring 66, the lower arm 53b is held at the low temperature position L in contact with the first stopper wall 64a, and the upper arm 53a of the third control lever 53 is farthest from the vaporizer 23. The lower arm 52b of the second control lever 52 is received at the position.

  On the other hand, in the carburetor 23, the choke lever 33 is urged to rotate in the opening direction of the choke valve 31 by the urging force of the choke spring 39, but the link 46 is in the slot 59 of the upper arm portion 52 a of the second control lever 52. By contacting one inner end wall, the choke valve 31 is held in a half-open state.

  In order to operate the power lawnmower 1, first, the brake release lever 20 is grasped together with the steering handle 6 and the operation wire 21 is pulled to operate the release arm 16c and rotate the brake shoe 16 to the brake release position B. It moves to release the braking force on the flywheel 9 and frees the crankshaft 5. At this time, the engine kill switch 22 is deactivated by the brake shoe 16 (the ignition circuit can be activated), and at the same time, the release arm 16c of the brake shoe 16 has a claw 51a, that is, a first portion as shown in FIG. Since the first control lever 51 is rotated in the clockwise direction, the first control lever 51 is rotated in the elastic arm portion 52c, that is, the second control lever 52 in the counterclockwise direction. The link 46 is pressed to rotate the choke lever 33 to the closed position C as shown in FIG. In the meantime, as shown in FIG. 17, the locked arm 50 integrated with the choke lever 33 slides on the slope 61 of the lock arm 49 of the throttle lever 40 and bends so as to push the lock arm 49 upward (see FIG. 17). 17 (b)), and after passing, the contact surface 62 comes into contact with the locked arm 50 (see FIG. 17 (c)) due to the return of the lock arm 49 to the original state, and the choke lever (see FIG. 17 (c)). 33 is held in the closed position C.

  Even after the choke lever 33 is held at the closed position C, if the clockwise rotation of the first control lever 51 further proceeds, the first control lever 51 deflects the elastic arm portion 52c of the second control lever 52. , The elastic arm portion 52c is passed, that is, the elastic arm portion 52c is released to reach the second position E.

  The second control lever thus released from the first control lever 51 returns to the original position by the urging force of the second return spring 58 (see FIG. 8). At this time, since the long hole 59 of the second control lever 52 moves relative to the link 46 connected to the choke lever 33, the second control lever 52 leaves the choke lever 33 at the closed position C, and links It is possible to return to the original position without being obstructed by 46.

  Thus, if the brake release lever 20 is operated to release the braking force of the engine 4 against the flywheel 9, the choke lever 33 can be automatically held at the closed position C in conjunction therewith. The person does not need to touch the choke lever 33 when starting the engine 4, and therefore does not worry about forgetting to close the choke valve 31.

  After the brake release lever 20 is operated, the recoil starter 11 is then operated to crank the engine 4. At this time, since the choke valve 31 is already fully closed in the intake passage 30a of the carburetor 23, a rich air-fuel mixture suitable for cold start is generated, and the engine 4 that has sucked it can start quickly. it can.

  As shown in FIGS. 9 and 10, when the engine 4 is started, the centrifugal governor 45 generates an output corresponding to the rotational speed of the crankshaft 5, and the governor lever 42 due to this output and the governor lever 44 due to the load of the governor spring 44 are generated. The governor lever 42 rotates to the point where the moment of 42 is balanced, and the throttle valve 32 is automatically closed, so that the arm 50 to be locked of the choke lever 33 is released from the restraint by the lock arm 49 of the throttle lever 40. As a result, the choke lever 33 is rotated by the urging force of the choke spring 39 so as to open the choke valve 31, and the right movement in FIG. 9 of the link 46 associated therewith is the long hole 59 of the second control lever 52. The choke valve 31 is held in a half-open state immediately after the engine is started. Therefore, the air-fuel mixture generated in the intake passage 30a of the carburetor 23 is adjusted to a concentration suitable for the warm-up operation of the engine, can ensure a stable warm-up operation state, and the opening delay of the choke valve 31 It is possible to avoid the deterioration of fuel efficiency due to.

  Thus, when the engine 4 is started, the crankshaft 5 drives the cutting blade 7 to rotate, so that the operator pushes and moves the power lawn mower 1 while grasping the steering handle 6 together with the brake release lever 20, Work can be done.

  When the engine is warmed to a predetermined temperature or higher due to the warm-up operation, the ambient temperature also rises, and the second control spring 67 is heated to the shape recovery temperature or higher. Then, the second control spring 67 exhibits its original spring function and generates a set load (tensile force) stronger than that of the first control spring 66. Therefore, as shown in FIG. The arm portion 53b rotates counterclockwise against the set load of the first control spring 66 until the high temperature position H at which the arm portion 53b contacts the second stopper wall 64b. As a result, the upper arm portion 53a of the third control lever 53 moves backward from the abutting wall 60 of the lower arm portion 52b of the second control lever 52, so that the second control lever 52 has the urging force of the second return spring 58. , The contact wall 60 is rotated so as to follow the retreat of the upper arm portion 53a, and the end portion of the link 46 in the long hole 59 is made free. Therefore, the choke lever 33 is rotated to the open position O by the urging force of the choke spring 39, so that the choke valve 31 is automatically fully opened, and the concentration of the air-fuel mixture generated in the carburetor 23 becomes a normal value. Become. Moreover, since the shape of the second control spring 67 is restored relatively slowly as the engine ambient temperature increases, the transition of the choke valve 31 to the fully open state is also slow, and therefore the change in the concentration of the air-fuel mixture is also slow. Therefore, malfunction of the engine due to a sudden change in the air-fuel mixture concentration can be prevented.

  Thus, at the end of the warm-up operation of the engine 4, the choke valve is utilized by using the third control lever 53 rotated to the high temperature position H by causing the second control spring 67 made of memory alloy to exhibit its original spring function. 31 is automatically controlled to the fully open state, so that the opening degree of the choke valve 31 is rationally controlled according to the degree of increase in the engine temperature. Both fuel efficiency can be satisfied.

  The choke valve control device 27 is mechanically constituted by the first to third control levers, the first and second control springs 66 and 67, etc., and can be provided with a relatively simple structure at a low cost. In addition, the control of the choke valve can be stabilized without being affected by the pulsation of the intake negative pressure of the engine.

  When the work by the power work machine 1 is finished and the operator releases his / her hand from the brake release lever 20 that has been towed, the brake shoe 16 is pressed against the flywheel 9 by the urging force of the brake spring 19. Since the engine kill switch 22 is operated while returning to A, the engine 4 is immediately held in the operation stop state. At this time, the release arm 16c of the brake shoe 16 releases the claw portion 51a of the first control lever 51, so that the second control lever 52 pushes the claw portion 51a to the brake shoe 16 by the urging force of the first return spring 57. The second control lever 52 is restrained by the third control lever 53 at the high temperature position H, and the elastic arm portion 52c is moved to the first control lever 51. Since the second control lever 52 is out of the rotation path, the second control lever 52 can return to the original position without hitting the elastic arm 52c.

  Accordingly, when the engine 4 is not completely cooled from the high temperature state, that is, when the engine 4 is in the hot state, in order to operate the power work machine 1 again, the brake release lever 20 is operated to the brake release position B, and the first control lever 51 is operated. The second control lever 52 is positioned by the third control lever 53 at the high temperature position H and continues to release the choke lever 33 at the open position O even when the lever is rotated again to the second position E. Therefore, the recoil starter 11 When the engine 4 is cranked by operating the above, the intake passage 30a of the carburetor 23 generates a relatively lean air-fuel mixture suitable for hot start, so that the engine 4 can be hot-started accurately.

  If the engine 4 is completely cooled after the operation is stopped, the ambient temperature also decreases, and if the second control spring 67 falls below the shape recovery temperature, the spring 67 loses its spring function. The third control lever 53 moves under the control of the first control spring 66 and is rotated to the low temperature position L. As a result, the upper arm portion 53a of the third control lever 53 returns the second control lever 52 to its original position against the urging force of the second return spring 58 along with the rotation. The choke lever 33 can return to the initial position shown in FIGS. 4 and 5 corresponding to the half-open state of the choke valve 31.

  Next, a second embodiment of the present invention shown in FIG. 18 will be described.

  In the second embodiment, in the choke valve closed state holding means 72, the relief spring 36 (see FIG. 14) in the hub 33a of the choke lever 33 is affected by the movement of the locked arm 50 in the vertical direction (the axial direction of the choke valve 31). (See) expansion and contraction. That is, the lock arm 49 and the arm to be locked 50 are both given rigidity, but an inclined surface 61 having a slope opposite to that of the first embodiment is formed on one side of the arm to be locked 50 integrated with the hub 33a. . Since the other configuration is the same as that of the first embodiment, portions corresponding to those of the first embodiment are denoted by the same reference numerals in FIG.

  Thus, when the choke lever 33 is rotated toward the closing position C by the pulling operation of the brake release lever 20, the slope of the arm 50 to be locked is shown in FIGS. When 61 abuts on the lock arm 49, the inclined surface 61 is pressed upward by the lock arm 49, so that the hub 33 a compresses the relief spring 36 and moves upward, while the arm to be locked 50 is moved to the lock arm 49. Pass above. When the choke lever 33 reaches the closed position C, the hub 33a is returned to the lower position by the urging force of the relief spring 36, and the abutment surface 62 of the locked arm 50 is brought into contact with the lock arm 49. The lever 33 can be held at the closed position C.

  As shown in the first and second embodiments, both the choke valve closed state holding means 72 are connected to the lock arm 49 connected to the throttle lever 40 and the choke lever 33, and the throttle lever 40 is connected to the throttle lever 40. When the choke lever 33 is turned to the closed position C when the valve 32 is in the open position corresponding to the fully open position, the lock arm 49 is elastically moved over the lock arm 49 and is prevented from being rotated backward by the lock arm 49. Since the lock arm 50 is used, the structure is simple and the choke valve control device 27 can be reduced in cost.

  The present invention is not limited to the above-described embodiments, and various design changes can be made without departing from the scope of the invention.

The side view of the power lawn mower carrying the engine provided with the choke valve control device according to the first embodiment of the present invention. The partially broken top view of the said engine. FIG. 3 is a sectional view taken along line 3-3 in FIG. 2. The principal part enlarged view of FIG. FIG. 5 is a cross-sectional view taken along line 5-5 in FIG. 4 (showing the operating state of the braking mechanism). FIG. 6 is a view corresponding to FIG. 5 showing a state before the brake mechanism is released and the engine is not cold started. FIG. 7 is a view taken in the direction of arrow 7 in FIG. FIG. 6 is a diagram corresponding to FIG. 5 showing a state when the engine is cold started. Correspondence figure with FIG. FIG. 6 is a diagram corresponding to FIG. 5 showing the warm-up operation state of the engine. FIG. 10 is a view taken in the direction of arrow 10 in FIG. 9. FIG. 6 is a correspondence diagram with FIG. 5 showing a state where the engine warm-up operation ends. FIG. 12 is a view taken in the direction of arrow 12 in FIG. 11. FIG. 6 is a diagram corresponding to FIG. 5 showing a high-temperature stop state of the engine. FIG. 14 is an enlarged sectional view taken along line 14-14 of FIG. FIG. 15 is a sectional view taken along line 15-15 in FIG. 14; FIG. 16 is a sectional view taken along line 16-16 in FIG. 15; FIG. 5 is an explanatory diagram of the operation of the choke lever closed position holding means, in which FIG. FIG. 18 is a view corresponding to FIG. 17 showing a second embodiment of the present invention.

Explanation of symbols

4 ... Engine 23 ... Vaporizer 27 ... Choke valve control device 31 ... Choke valve 32 ... Throttle valve 33 ... Choke lever 39 ... Choke Spring 40 ... Throttle lever 44 ... Governor spring 45 ... Governor (centrifugal governor)
49 ... Lock arm 50 ... Locked arm 53 ... Control lever (third control lever)
66... First control spring 67... Second control spring 72.

Claims (2)

  The choke lever (33) connected to the choke valve (31) of the carburetor (23) and spring-biased in the valve opening direction of the choke valve (31) corresponds to the fully closed position of the choke valve (31). When the choke lever (33) is rotated to the closed position (C), the choke lever (33) is held at the closed position (C), but the choke lever (33) is released from the hold by the subsequent throttle operation of the vaporizer (23). The choke closed state holding means (72) and the fixed structure (25) are pivotally supported to rotate between the low temperature position (L) and the high temperature position (H). The choke lever (33) released from (72) is regulated to an intermediate position (M) corresponding to the half-open position of the choke valve (31), and the choke lever (33) is moved to the choke valve (31) at the high temperature position (H). In the fully open position Under the influence of the engine temperature, the control lever (53) that regulates to the corresponding open position (O), the first control spring (66) that urges the control lever (53) toward the low temperature position (L), and Thus, when the engine temperature reaches a predetermined high temperature, the shape is restored, and the spring force that rotates the control lever (53) to the high temperature position (H) against the biasing force of the first control spring (66) is exhibited. A choke valve control device for a carburetor, comprising a second control spring (67) made of a shape memory alloy. In the carburetor choke valve control device according to claim 1,
The choke closed state holding means (72) is connected to the lock arm (49) connected to the throttle lever (40) connected to the throttle valve (32) of the carburetor (23) and to the choke lever (33). When the throttle lever (40) is in the open position corresponding to the fully open position of the throttle valve (32), when the choke lever (33) is rotated to the closed position (C), the lock arm (49) rotates backward. The throttle lever (40) includes a governor spring (44) that urges the throttle lever (40) in the opening direction of the throttle valve (32), and increases the engine speed. In response, the throttle lever (40) is connected to a governor (45) that generates an output that biases the throttle valve (32) in the closing direction, and the throttle by the output of the governor (45) is By the rotation of the closing direction of Rureba (40), the locking arm (49) is characterized in that to release the locked arm (50), the carburetor choke valve control device.

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