JP2015025373A - Choke mechanism of engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a choke mechanism capable of keeping a constant opening speed of an opening by delaying a rotating speed of a choke plate in comparison with that in an intermediate period of rotation, at an initial period and a latter period of the rotation when the rotating speed of the choke plate is generally increased.SOLUTION: A choke mechanism of an engine including a base portion 30 having an opening 31, a choke lever 50 rotatably disposed on the base portion 30, and a choke plate 35 driven by the choke lever 50 to be rotated, and opening and closing the opening 31, further has a projection 56 for a first cam, and a first cam receiving portion 41 engaged with the projection 56 for the first cam from the initial period of the rotation of the choke lever 50 to the intermediate period of the rotation. A pressure angle between the projection 56 for the first cam and the first cam receiving portion 41 in the initial period of the rotation of the choke lever 50 is smaller than a pressure angle in the intermediate period of the rotation of the choke lever 50.

Description

  The present invention relates to an engine choke mechanism used in a mower or the like.

  Patent Document 1 discloses a choke mechanism including a choke plate that opens and closes an opening communicating with an air cleaner box, and a flat bar-shaped choke lever that meshes with a gear provided at an end of the choke plate and rotates the choke plate. Have been described.

  However, in the choke mechanism described in Patent Document 1, the choke plate and the choke lever are engaged with each other via a gear, and therefore, as shown by a straight line L10 in FIG. The rotation angle of the same. Therefore, since the choke plate rotates according to the operation amount of the choke lever, when the choke lever is operated at a constant speed, the choke plate also rotates at a constant speed.

  For this reason, at the initial stage of rotation of the choke lever, a large force acts on the choke lever to rotate fast, and accordingly the choke plate also rotates fast, so the opening speed of the opening is faster than in the middle of operation. Become. In addition, in the latter half of the rotation of the choke lever, acceleration is applied in the rotation direction of the choke lever, and the choke lever and the choke plate rotate faster, so that the opening speed of the opening becomes faster than in the middle operation. Thus, the opening speed of the opening by the choke plate varies.

Japanese Patent No. 3764572

  The present invention has been made in view of the above-mentioned conventional problems, and in general, the rotation speed of the choke plate is compared with that of the rotation middle period at the early and late rotation stages when the rotation speed of the choke plate is increased. It is an object of the present invention to provide a choke mechanism that keeps the opening speed constant by slowing down.

A base having an opening for taking in air from the outside;
A choke lever rotatably disposed on the base,
A choke plate that is pivotally disposed at the base, rotates in accordance with the choke lever, and opens and closes the opening;
In an engine choke mechanism equipped with
A first cam projection formed on the choke lever and projecting toward the choke plate;
A first cam receiving portion that is formed on the choke plate and engages with the first cam projection from an initial rotation to an intermediate rotation of the choke lever;
The pressure angle between the first cam projection and the first cam receiving portion at the initial rotation of the choke lever is smaller than the pressure angle at the middle rotation of the choke lever.

  Here, the pressure angle is an angle formed by the rotation direction of the choke plate and the common tangent line of the first cam receiving portion and the first cam projection.

  In general, since the pressure angle between the first cam projection and the first cam receiving portion is smaller in the initial stage of rotation when the rotation speed of the choke plate is higher than in the middle period of rotation, the rotation speed of the choke plate is slower. Become. Therefore, the opening speed of the opening can be kept constant.

The choke mechanism further includes
A second cam projection formed on the choke lever and projecting toward the choke plate;
A second cam receiving portion that is formed on the choke plate and engages with the second cam projection from the middle stage to the late stage of rotation of the choke lever;
The pressure angle between the second cam projection and the second cam receiving portion in the later stage of rotation of the choke lever is smaller than the pressure angle in the middle stage of rotation of the choke lever.

  Here, the pressure angle is an angle formed by the rotation direction of the choke plate and the common tangent line of the second cam receiving portion and the second cam projection.

  In general, the rotation speed of the choke plate is slower in the latter half of the rotation when the rotation speed of the choke plate is higher, because the pressure angle between the second cam projection and the second cam receiving portion is smaller than in the middle rotation. Become. Therefore, the opening speed of the opening can be kept constant.

  Further, the cam projection is constituted by a first cam projection and a second cam projection, and the cam receiving portion is constituted by a first cam receiving portion and a second cam receiving portion. Therefore, the wear caused by the engagement between the cam projection and the cam receiving portion is distributed to the two cam projections and the cam receiving portion, so that the durability can be improved.

The first cam protrusion and the second cam protrusion are cylindrical.
It is preferable that the first cam receiving portion and the second cam receiving portion include a wall portion constituting an arc-shaped groove portion formed in the choke plate.
Thus, the choke lever and the choke plate can be engaged with each other with a simple configuration.

  For example, the groove portion starts from a point that is a distance r1 away from the center of the mounting hole, which is the center of rotation of the choke plate, and is intermediate between the groove portions so that the distance from the center of the mounting hole increases in the clockwise direction. It is preferable that the first groove portion extends to the point.

  For example, the groove portion further extends from the intermediate point in a clockwise direction so that the distance from the center of the mounting hole becomes small, and ends at a point separated from the center of the mounting hole by a distance r2 smaller than the distance r1. It is preferable to include a second groove portion.

  According to the present invention, the pressure angle between the first cam projection and the first cam receiving portion is smaller in the early and late turning stages when the turning speed of the choke plate is generally higher than in the turning middle stage. Therefore, the rotation speed of the choke plate becomes slow. Further, since the pressure angle between the second cam projection and the second cam receiving portion is generally smaller in the later stage of rotation when the rotation speed of the choke plate is higher than in the middle period of rotation, the rotation speed of the choke plate is reduced. Becomes slower. Therefore, the opening speed of the opening can be kept constant.

1 is a schematic view of an engine according to an embodiment of the present invention. The disassembled perspective view of the choke mechanism with which the engine of FIG. 1 is mounted. The exploded perspective view which looked at the choke mechanism of Drawing 2 from a different direction. The expansion perspective view of a chalk plate. The enlarged front view of a chalk plate. The expansion perspective view of a chalk lever. The enlarged view which shows the relationship between the choke plate and the choke lever with the choke plate closing the opening. The enlarged view which shows the relationship between the chalk plate in the state which rotated the chalk plate 10 degree | times, and a chalk lever. The enlarged view which shows the relationship between the chalk plate in the state which rotated the chalk plate 20 degree | times, and a chalk lever. The enlarged view which shows the relationship between the chalk plate in the state which rotated the chalk plate 25 degree | times, and a chalk lever. The enlarged view which shows the relationship between the chalk plate in the state which rotated the chalk plate 40 degree | times, and a chalk lever. The enlarged view which shows the relationship between the chalk plate in the state which rotated the chalk plate 60 degree | times, and a chalk lever. The enlarged view which shows the relationship between the choke plate and the choke lever in a state where the choke plate is rotated 70 degrees and the opening is opened. The graph which shows the rotation angle of the chalk plate with respect to the rotation angle of a choke lever.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  As shown in FIG. 1, the engine 1 according to the present embodiment includes a cylinder block 11, a cylinder head 15 positioned at the upper part of the cylinder block 11, and a crankshaft housing portion 22 disposed at the lower part of the cylinder block 11. I have.

  A piston 13 is accommodated in the bore 12 in the cylinder block 11 so as to be able to reciprocate. The reciprocating motion of the piston 13 is converted into the rotational motion of the crankshaft 23 accommodated in the crankshaft accommodating portion 22 by the connecting rod 14.

  The cylinder head 15 is provided with an intake valve 16 and an exhaust valve 17 that can reciprocate in the vertical direction. The intake passage 18 in which the intake valve 16 is disposed communicates with an air cleaner box 25 that houses an air cleaner that takes air from outside into the engine 1 and purifies it. An exhaust passage 18 in which the exhaust valve 17 is disposed communicates with a muffler 21 that discharges combustion air in the engine 1 to the outside.

  When the intake valve 16 is operated by the driving force of the crankshaft 23, the air taken from the air cleaner box 25 is sent into the bore 12. When the exhaust valve 17 is activated, combustion air flows out from the bore 12 and is discharged from the muffler 21.

  A choke mechanism 27 according to the present invention is disposed on the side wall of the air cleaner box 25. As shown in FIGS. 2 and 3, the choke mechanism 27 includes a base 30, a choke plate 35 rotatably disposed on the base 30, and a choke lever 50 that operates the position of the choke plate 35. I have.

  The base 30 is substantially plate-shaped and constitutes the side wall of the air cleaner box 25. The base 30 has an opening 31 provided substantially at the upper center, a plate shaft hole 32 provided next to the opening 31, and a lever provided next to the plate shaft hole 32 opposite to the opening 31. A shaft hole 33 is provided. The opening 31 is a circular hole that communicates the air cleaner box 25 and the intake passage 18. The amount of air flowing into the bore 12 from the air cleaner box 25 through the intake passage 18 is adjusted by opening and closing the opening 31 by the choke plate 35. A choke plate 35 is rotatably supported in the plate shaft hole 32. A choke lever 50 is rotatably supported in the lever shaft hole 33.

  The choke plate 35 includes a substantially fan-shaped drive unit 36 that is driven by being engaged with the choke lever 50, and a closing unit 44 that is continuous with the drive unit 36 via a smooth curve.

  4 is a perspective view of the choke plate 35 viewed from the choke lever 50 side, and FIG. 5 is a front view of the choke plate 35 viewed from the opposite side of the choke lever 50. In FIG. 5, wall portions (including the first cam receiving portion 41 and the second cam receiving portion 42) constituting the groove portions 37 and 38 to be described later should be originally shown by dotted lines, but are shown by solid lines for convenience of explanation. .

  The surface of the drive unit 36 facing the choke lever 50 starts from a l point that is a distance r1 away from the center O point of the mounting hole 46, and the distance from the center O point increases in the clockwise direction. A first groove portion 37 extending to an intermediate m point, an n point that extends from the point m in a clockwise direction so that the distance from the center O point becomes smaller, and is separated from the center O point of the mounting hole 46 by a distance r2 smaller than r1. A second groove 38 is formed as a terminal end. A first cam receiving portion 41 that is engaged with a first cam projection 56 of a choke lever 50, which will be described later, is formed in the wall portion constituting the first groove portion 37 in the initial stage of opening the opening 31 from the closed state. Yes. A second cam receiving portion 42 that engages with the second cam projection 57 of the choke lever 50 is formed on the wall portion that constitutes the second groove portion 38 in the later stage of opening the opening 31. By forming the cam receiving portion from the first cam receiving portion 41 and the second cam receiving portion 42, wear caused by engaging with the cam projections 56, 57 is distributed to the two cam receiving portions 41, 42. Thus, the durability of the respective cam receiving portions 41 and 42 can be improved.

  The first cam receiving portion 41 is formed on the outer wall portion of the first groove portion 37, and the second cam receiving portion 42 is formed on the inner wall portion of the second groove portion 38. As shown in FIG. 5, the first cam receiving portion 41 includes a linear area A and a linear area B that forms a predetermined angle with the area A. The second cam receiving portion 42 includes an arcuate region C centered on the point Pc and an arcuate region D centered on the point Pd. In addition, the shape of the area | region A to the area | region D is not specifically limited. The linear region A and the region B may be formed in an arc shape. Further, the arc-shaped region C and the region D may be formed in a straight line shape.

  A small-diameter air hole 45 is formed in the center of the closing portion 44 of the choke plate 35. The choke plate 35 is disposed in a plate shaft hole 32 of the base 30 via a pin (not shown) inserted into a mounting hole 46 formed in the drive unit 36 so as to be rotatable around the plate shaft hole 32. Established.

  As shown in FIG. 6, the choke lever 50 includes a linearly extending arm portion 51, an operation portion 52 that is provided at the distal end of the arm portion 51 and can be gripped from the outside of the engine 1, and a base end of the arm portion 51. And a cam portion 53 provided.

  The cam portion 53 includes a cylindrical portion 54 that protrudes from the arm portion 51 toward the choke plate 35 and a pair of cam protrusions 56 and 57 provided on the outer periphery of the cylindrical portion 54 on the end surface 55 side. The cam protrusions 56 and 57 have a columnar shape and protrude toward the choke plate 35 from the end surface 55 of the cylindrical portion 54. As described above, the cam projections 56 and 57 are cylindrical, and the cam receiving portions 41 and 42 are wall portions constituting the groove portions 37 and 38. Therefore, the choke lever 50 and the choke plate 35 can be easily engaged with each other. Yes. Further, since the cam projection is composed of the first cam projection 56 and the second cam projection 57, the wear caused by engaging with the cam receiving portions 41, 42 is caused to the two cam projections 56, 57. It is possible to improve the durability of the cam projections 56 and 57 by dispersing.

  The choke lever 50 is disposed in the base 30 so as to be rotatable around the lever shaft hole 33 by fitting the cylindrical portion 54 into the lever shaft hole 33. The choke lever 50 is attached to the lever shaft hole 33 by inserting the arm portion 51 from the operation portion 52 into the lever shaft hole 33 from the front side to the back side in FIG. In the state where the choke lever 50 is attached to the air cleaner box 25 via the base portion 30, the operation portion 52 projects sideways from the side portion of the engine 1.

  The choke plate 35 and the choke lever 50 are attached to the base 30 to assemble the choke mechanism 27, and the choke mechanism 27 is fixed to the wall of the air cleaner box 25. When starting the engine 1, the choke lever 50 is operated to close the opening 31 (see FIG. 7). At this time, the air cleaner box 25 and the intake passage 18 communicate with each other through the air hole 45. When the engine 1 is started in this state, the air flowing into the bore 12 from the air cleaner box 25 through the intake passage 18 is small, and the fuel concentration in the bore 12 is increased, so that the startability of the engine 1 is improved.

  An operation for returning the choke lever 50 after the engine 1 is started will be described.

  As shown in FIG. 7, when the operation portion 52 of the choke lever 50 is operated in the clockwise direction in the drawing, the choke lever 50 rotates around the lever shaft hole 33. As a result, the first cam projection 56 of the choke lever 50 presses the first cam receiving portion 41, and the drive portion 36 rotates counterclockwise around the plate shaft hole 32 (mounting hole 46). The plate 35 rotates.

  As shown in FIG. 8, when the choke lever 50 is rotated 10 degrees (initial stage of rotation), the pressure angle θ1 is 18.16 degrees, which is smaller than the pressure angle θ2 described later. Here, the pressure angle θ means the rotation direction R of the choke plate 35 and the common tangent line T of the first cam receiving portion 41 and the first cam projection 56 or the second cam receiving portion 42 and the second cam protrusion 57. The angle formed by the common tangent line T. Moreover, the initial stage of rotation refers to a range in which the choke lever 50 is rotated from 0 degree to 15 degrees.

  Hereinafter, the relationship between the pressure angle θ1 and the rotation speed of the choke plate 35 will be described. It is assumed that a force F1 is applied from the first cam projection 56 to the first cam receiving portion 41. This force F1 is the force F2 in the rotation direction R of the choke plate 35 and the force in the direction orthogonal to the rotation direction R, that is, the first cam receiving portion 41 and the first cam projection 56 from the center of the mounting hole 46. It can be divided into force F3 in the direction toward the contact point. Here, the angle formed by the force F1 and the force F3 is θ1. Therefore, when the pressure angle θ1 increases, the force F2 also increases, and the rotation speed of the choke plate 35 increases.

  As described above, when the pressure angle θ1 is small, the force F2 is also small, and the rotation speed of the choke plate 35 is slower than that in the middle rotation period described later.

  As shown in FIG. 9, when the choke lever 50 is rotated by 20 degrees (mid rotation period), the pressure angle θ2 is 19.08 degrees larger than θ1. Therefore, the rotation speed of the choke plate 35 is faster than that at the initial rotation. The middle rotation period refers to a range in which the choke lever 50 is rotated from 15 degrees to 55 degrees.

  As described above, since the pressure angle between the first cam projection 56 and the first cam receiving portion 41 is generally smaller in the initial stage of rotation when the rotation speed of the choke plate 35 is generally faster than in the middle period of rotation, The rotation speed of the choke plate 35 becomes slow. Therefore, the opening speed of the opening 31 can be kept constant.

  As shown in FIG. 10, when the choke lever 50 is rotated 25 degrees, the cam projection 56 that has been engaged with the first cam receiving portion 41 is separated from the first cam receiving portion 41. The cam projection 57 engages with the second cam receiving portion 42 instead of the first cam receiving portion 41.

  As shown in FIG. 11, when the choke lever 50 is rotated by 40 degrees (middle period of rotation), the pressure angle θ3 is 27.37 degrees, which is larger than the pressure angle θ4 described later. Accordingly, the rotation speed of the choke plate 35 is faster than the later rotation period described later.

  Hereinafter, the relationship between the pressure angle θ3 and the rotation speed of the choke plate 35 will be described. It is assumed that a force F4 is applied from the second cam projection 57 to the second cam receiving portion 42. This force F4 is generated from the force F5 in the rotation direction R of the choke plate 35 and the force in the direction orthogonal to the rotation direction R, that is, from the contact point between the second cam receiving portion 42 and the second cam projection 57. It can be divided into force F6 in the direction toward the center of the. Here, the angle formed by the force F4 and the force F6 is θ3. Therefore, when the pressure angle θ3 decreases, the force F5 also decreases, and the rotation speed of the choke plate 35 decreases.

  As shown in FIG. 12, when the choke lever 50 is rotated by 60 degrees (late rotation period), the pressure angle θ4 is smaller than θ3 and 22.73 degrees. Accordingly, the rotation speed of the choke plate 35 is slower than that in the middle rotation period. The latter term of rotation refers to a range in which the choke lever 50 is rotated from 55 degrees to 70 degrees.

  As described above, the pressure angle between the second cam projection 57 and the second cam receiving portion 42 is generally smaller in the latter half of the turn when the turning speed of the choke plate 35 is generally faster than in the middle turn. The rotation speed of the choke plate 35 becomes slow. Therefore, the opening speed of the opening 31 can be kept constant.

  Finally, as shown in FIG. 13, when the choke lever 50 is rotated 70 degrees, the choke plate 35 is also rotated 70 degrees to completely open the opening 31.

  The relationship between the rotation angle of the choke lever 50 and the rotation speed of the choke plate 35 will be described in comparison with a conventional example. As shown in FIG. 14, when the choke lever 50 is rotated from 0 degrees to 15 degrees (initial stage of rotation), the rotation speed of the choke plate 35 is slower than the rotation speed of the conventional choke plate. When the choke lever 50 is rotated from 15 degrees to 55 degrees (middle rotation period), the rotation speed of the choke plate 35 is faster than the rotation speed of the conventional choke plate. When the choke lever 50 is rotated from 55 degrees to 70 degrees (late rotation period), the rotation speed of the choke plate 35 is slower than the rotation speed of the conventional choke plate.

  From the above, compared to the conventional case, the rotation speed of the choke plate 35 is generally reduced in the early and late rotation stages when the rotation speed of the choke plate 35 is generally increased, and the opening speed of the opening 31 is kept constant. It can be said that it is possible.

DESCRIPTION OF SYMBOLS 1 Engine 27 Choke mechanism 30 Base 31 Opening 35 Choke plate 37 1st groove part 38 2nd groove part 41 1st cam receiving part 42 2nd cam receiving part 50 Choke lever 56 1st cam protrusion 57 2nd cam protrusion

In order to solve the above problems, the present invention provides:
A base having an opening for taking in air from the outside;
A choke lever rotatably disposed on the base,
A choke plate that is pivotally disposed at the base, rotates in accordance with the choke lever, and opens and closes the opening;
In an engine choke mechanism equipped with
A first cam projection formed on the choke lever and projecting toward the choke plate;
The said formed in the choke plate, the engaged with the projection for the first cam from rotating and early turning mid choke lever, rotating the choke plate being driven by the movement of the first protrusion cam 1 cam receiving part,
Have
A pressure angle that is an angle formed by the rotation direction of the choke plate at the initial rotation of the choke lever and the common tangent line of the first cam receiving portion and the first cam projection is a middle rotation of the choke lever. Kushida small in comparison with the pressure angle.

The choke mechanism further includes
A second cam projection formed on the choke lever and projecting toward the choke plate;
The said formed in the choke plate, it said engaged with the protrusion for the second cam from rotating metaphase toward turning late choke lever, rotating the choke plate being driven by the movement of the projection for the second cam With two cam receivers,
A pressure angle, which is an angle formed by a rotation direction of the choke plate at a later stage of rotation of the choke lever and a common tangent line of the second cam receiving portion and the second cam projection, is a middle rotation period of the choke lever. It is preferable that the pressure angle is small .

For example, the grooves, the points distance r1 away from the center of the choke plate rotation center and becomes the mounting hole of the starting point, of the so that the distance from the center of the mounting hole in the clockwise direction increases the groove Preferably, the first groove portion extends to an intermediate point.

For example, the groove further, extending from said intermediate point such that the distance from the center of the mounting hole in a clockwise direction decreases, end point point spaced the distance r1 is smaller than the distance r2 from the center of the attachment hole It is preferable to include the 2nd groove part.

The choke lever 50 and the opposing surfaces of the driving portion 36, the l (el) points from the central point O distance r1 away of the mounting hole 46 and start point, so that the distance from the center point O in the clockwise direction increases A first groove portion 37 extending to an intermediate m point, and extending from the point m in a clockwise direction so that the distance from the center O point becomes smaller, and being separated from the center O point of the mounting hole 46 by a distance r2 smaller than r1. a second groove portion 38 to a final point is formed a. A first cam receiving portion 41 that is engaged with a first cam projection 56 of a choke lever 50, which will be described later, is formed in the wall portion constituting the first groove portion 37 in the initial stage of opening the opening 31 from the closed state. Yes. A second cam receiving portion 42 that engages with the second cam projection 57 of the choke lever 50 is formed on the wall portion that constitutes the second groove portion 38 in the later stage of opening the opening 31. By forming the cam receiving portion from the first cam receiving portion 41 and the second cam receiving portion 42, wear caused by engaging with the cam projections 56, 57 is distributed to the two cam receiving portions 41, 42. Thus, the durability of the respective cam receiving portions 41 and 42 can be improved.

Claims (5)

A base having an opening for taking in air from the outside;
A choke lever rotatably disposed on the base,
A choke plate that is pivotally disposed at the base, rotates in accordance with the choke lever, and opens and closes the opening;
In an engine choke mechanism equipped with
A first cam projection formed on the choke lever and projecting toward the choke plate;
A first cam receiving portion that is formed on the choke plate and engages with the first cam projection from an initial rotation stage to an intermediate rotation stage of the choke lever;
Have
An engine choke characterized in that a pressure angle between the first cam projection and the first cam receiving portion in the initial stage of rotation of the choke lever is smaller than the pressure angle in the middle stage of rotation of the choke lever. mechanism. The choke mechanism further includes
A second cam projection formed on the choke lever and projecting toward the choke plate;
A second cam receiving portion that is formed on the choke plate and engages with the second cam projection from the middle stage to the late stage of rotation of the choke lever;
2. The pressure angle between the second cam projection and the second cam receiving portion in the later stage of rotation of the choke lever is smaller than the pressure angle in the middle stage of rotation of the choke lever. The engine choke mechanism described in 1. The first cam protrusion and the second cam protrusion are cylindrical.
3. The engine choke according to claim 1, wherein the first cam receiving portion and the second cam receiving portion include a wall portion forming an arc-shaped groove portion formed in the choke plate. 4. mechanism.   The groove portion starts at a point that is a distance r1 from the center of the mounting hole, which is the center of rotation of the choke plate, and is located at an intermediate point of the groove portion so that the distance from the center of the mounting hole increases in the clockwise direction. The engine choke mechanism according to claim 3, further comprising a first groove portion extending to the top.   The groove portion further extends in a clockwise direction from the intermediate point so that the distance from the center of the mounting hole becomes small, and ends at a point separated from the center of the mounting hole by a distance r2 smaller than the distance r1. The engine choke mechanism according to claim 4, comprising two grooves.

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