JP2005076524A - Throttle device for general-purpose engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a throttle device for a general-purpose engine with a throttle valve connected to an actuator via a reduction gear, improving the responsiveness of the throttle valve fully closed when opened while using the actuator for opening/closing the throttle valve and reducing the size of the actuator. <P>SOLUTION: The throttle device for the general-purpose engine comprises the throttle valve 42 arranged in an intake passage for the general-purpose engine and connected to the actuator (an electric motor 44) via the reduction gear (a reduction gear mechanism 58), the throttle valve 42 being opened/closed to regulating the amount of intake air by driving the actuator 44. It has an energizing means (a return spring 76) for energizing the throttle valve 42 to its opening direction. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a throttle device for a general-purpose engine, and more particularly to a throttle device for a general-purpose engine in which a throttle valve is opened and closed by an actuator.

  For general-purpose engines (spark-ignition internal combustion engines) used as a drive source in various applications such as generators and agricultural machinery, the throttle valve opening is conventionally adjusted with a mechanical governor consisting of weights and springs. The engine speed was controlled.

  Recently, however, even in this type of general-purpose engine, it has been proposed to use an electronically controlled throttle device (electronic governor) that opens and closes a throttle valve with an actuator such as a stepping motor to accurately control the engine speed. Has been.

In such a technique, generally, a throttle shaft that supports a throttle valve and an actuator are connected by a reduction gear, and the output of the actuator is transmitted to the throttle valve. Further, the throttle valve is urged in the valve closing direction by urging means such as a return spring (see, for example, Patent Documents 1 and 2).
JP 2001-263098 A (paragraph 0008 etc.) JP 2003-83093 A (paragraph 0007 and the like)

  When opening the throttle valve from the fully closed position, if the throttle valve is energized in the closing direction (or even if no energizing force is applied), it will actually be affected by the backlash of the reduction gear. There was a problem that a time delay occurred before the throttle valve was opened and the responsiveness was not good.

  Further, the torque (pressure) in the valve closing direction acts on the throttle valve by the flow of intake air. Therefore, in order to open the throttle valve, a driving force larger than the resultant force of the urging means and the intake air pressure is required, so that the actuator for opening and closing the throttle valve needs to be enlarged. It was.

  Accordingly, an object of the present invention is to eliminate the above-mentioned disadvantages. The throttle valve and the actuator are connected via a reduction gear, and the throttle valve is opened from the fully closed position while the throttle valve is opened and closed by the actuator. Another object of the present invention is to provide a throttle device for a general-purpose engine that improves the response when the valve is operated and reduces the size of the actuator.

  In order to solve the above-mentioned object, in claim 1, a throttle valve disposed in an intake passage of a general-purpose engine, a throttle shaft that supports the throttle valve, and a throttle gear connected to the throttle shaft A throttle device for a general-purpose engine that adjusts the intake air amount by opening and closing the throttle valve by rotating the throttle shaft via the reduction gear by driving the actuator. An urging means for urging the throttle valve in the valve opening direction is provided.

  More specifically, in the throttle device for the general-purpose engine, one of the driven gear and the throttle shaft of the reduction gear is connected to a case in which the reduction gear is accommodated, and the throttle valve is opened. A return spring that biases in the direction is provided.

  The present invention includes a throttle valve disposed in an intake passage of a general-purpose engine, a throttle shaft that supports the throttle valve, and an actuator that is connected to the throttle shaft via a reduction gear. In the throttle device of a general-purpose engine that adjusts the intake air amount by opening and closing the throttle valve by rotating the throttle shaft via the reduction gear by driving the throttle valve, the throttle valve is attached in the valve opening direction. Since the biasing means is provided, the throttle valve is not affected by the backlash of the reduction gear when the throttle valve is opened from the fully closed opening, and therefore the throttle valve is not opened from the fully closed opening. Responsiveness can be improved. Further, since the torque in the valve closing direction acting on the throttle valve and the urging force (torque in the valve opening direction) acting on the throttle valve are canceled by the flow of the intake air, it is necessary to open the throttle valve. The driving force can be reduced, and thus the actuator for opening and closing the throttle valve can be reduced in size.

  The best mode for carrying out the throttle device for a general-purpose engine according to the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a schematic view generally showing a throttle device for a general-purpose engine according to a first embodiment of the present invention.

  In FIG. 1, reference numeral 10 indicates a general-purpose engine (hereinafter referred to as “engine”). The engine 10 includes a single cylinder (cylinder) 12, and a piston 14 is accommodated therein so as to be capable of reciprocating. A combustion chamber 16 is formed between the head of the piston 14 and the cylinder wall surface, and an intake valve 18 and an exhaust valve 20 are disposed on the cylinder wall surface, and a space between the combustion chamber 16 and the intake passage 22 or the exhaust passage 24 is provided. Open and close. The engine 10 is specifically a water-cooled four-cycle single-cylinder OHV type internal combustion engine, and has a displacement of 196 cc.

  The piston 14 is connected to a crankshaft 28, and the crankshaft 28 is connected to a camshaft 30 through a gear. A flywheel 32 is attached to the crankshaft 28, and a recoil starter 34 for manually starting the engine 10 is attached to the front end side of the flywheel 32. A power generation coil (alternator) 36 is disposed inside the flywheel 32 to generate an alternating current. The alternating current generated by the power generation coil 36 is converted into a direct current through a processing circuit (not shown), and then supplied as an operating power source to an ECU, a motor driver (not shown), an ignition circuit (not shown), and the like.

  A throttle body 40 is disposed upstream of the intake passage 22. A throttle valve 42 is accommodated in the throttle body 40, and the throttle valve 42 is connected to an electric motor 44 (actuator, specifically, a stepping motor or a DC motor) via a throttle shaft and a reduction gear mechanism which will be described later. Further, a carburetor assembly (not shown in FIG. 1) is provided upstream of the throttle valve 42 in the throttle body 40. The carburetor assembly is connected to a fuel tank (not shown) and injects gasoline fuel into the intake air according to the opening of the throttle valve 42 to generate an air-fuel mixture. The generated air-fuel mixture is sucked into the combustion chamber 16 of the cylinder 12 through the throttle valve 42, the intake passage 22 and the intake valve 18.

  A throttle opening sensor 46 is disposed in the vicinity of the electric motor 44 and outputs a signal corresponding to the opening θTH of the throttle valve 42 (hereinafter referred to as “throttle opening”). A crank angle sensor 48 made of an electromagnetic pickup is disposed near the flywheel 32 and outputs a pulse signal at every predetermined crank angle.

  An ECU (electronic control unit) 50 is disposed in the vicinity of the engine 10. The ECU 50 is formed of a microcomputer and includes a CPU, ROM, RAM, a counter, and the like (not shown).

  The outputs of the throttle opening sensor 46 and the crank angle sensor 48 described above are input to the ECU 50. The ECU 50 counts the output pulses of the crank angle sensor 48 and detects (calculates) the engine speed NE.

  The ECU 50 calculates the energization command value of the electric motor 44 based on the detected engine speed NE and the throttle opening θTH so that the engine speed NE matches the target speed NED and the calculated energization command value. Output to the electric motor 44 to control the driving of the electric motor 44.

  As described above, in this embodiment, the throttle valve 42 is opened and closed by the electronically controlled throttle device (electronic governor) including the throttle body 40, the ECU 50, and various sensors, and the intake air amount of the engine 10 is adjusted. The engine speed NE is controlled by measuring the amount.

  Next, the throttle device for a general-purpose engine according to this embodiment will be described in detail with reference to FIG. FIG. 2 is a plan view showing the throttle body 40 of the device. 3 is a cross-sectional view taken along line III-III in FIG.

  As shown in FIG. 3, a throttle valve 42 is disposed in the middle of the intake passage of the throttle body 40. The throttle valve 42 is supported by a throttle shaft 54. Further, the carburetor assembly 56 is attached upstream of the throttle valve 42 in the intake passage of the throttle body 40.

  As shown in FIGS. 2 and 3, the throttle shaft 54 is connected to the output shaft 44 </ b> S of the electric motor 44 via the reduction gear mechanism 58. The electric motor 44, the reduction gear mechanism 58, and a part of the throttle shaft 54 are accommodated in a unit case 60 that is integrally attached to the throttle body 40.

  The reduction gear mechanism 58 includes four gears. The reduction gear mechanism 58 will be described in detail. A first gear 66 is attached to the output shaft 44S of the electric motor, and the first gear 66 is rotatably supported inside the unit case 60. Is engaged with the gear 68. A third gear 70 is attached coaxially with the second gear 68, and the third gear 70 is engaged with a fourth gear 72 attached to the throttle shaft 54. As a result, the output of the electric motor 44 is transmitted to the throttle shaft 54 while being decelerated in accordance with the gear ratio of each gear, so that the throttle valve 42 is opened and closed.

  The third gear 70 and the fourth gear 72 are eccentric gears as well shown in FIG. More specifically, in the third gear 70 and the fourth gear 72, the rotation angle of the fourth gear 72 with respect to the rotation angle of the third gear 70 becomes smaller (reduction ratio) as the throttle opening θTH becomes smaller. Is set to be larger). This is because the pressure difference between the upstream side and the downstream side of the throttle valve 42 decreases as the throttle opening θTH increases, and eventually saturates (that is, the amount of change in the amount of intake air that passes through the throttle valve 42 is reduced). Therefore, when the throttle opening θTH is small, precise opening adjustment is performed, and when the throttle opening θTH is large, quick opening and closing is performed. The opening degree can be adjusted at speed, and the target engine speed can be accurately followed and responsive.

  As shown in FIG. 3, a return spring 76 is disposed on the outer periphery of the throttle shaft 54 inside the unit case 60. As shown in FIG. 4, the return spring 76 is a torsion coil spring. One end 76 a of the return spring 76 is connected to a fourth gear 72 attached to the throttle shaft 54, and the other end 76 b is connected to a hook pin 78 protruding inside the unit case 60. Note that the winding direction of the return spring 76 is set so that the throttle shaft 54 is rotated in the direction in which the throttle valve 42 is opened.

  That is, in this embodiment, the throttle valve 42 disposed in the intake passage 22 of the engine 10, the throttle shaft 54 that supports the throttle valve 42, and the throttle shaft 54 are connected via the reduction gear mechanism 58. And the electric motor 44 is driven to rotate the throttle shaft 54 via the reduction gear mechanism 58, thereby opening and closing the throttle valve 42 to adjust the intake air amount. In the general-purpose engine throttle device, a return spring 76 for biasing the throttle valve 42 in the valve opening direction (fully open direction) is provided. Hereinafter, this reason will be described.

  FIG. 5 is a schematic diagram showing the third gear 70, the fourth gear 72, and the throttle valve 42. As shown in FIG. 5, by driving the third gear 70 in a direction in which the throttle valve 42 is closed by the electric motor 44 (not shown in the figure), the throttle valve 42 is moved to the fourth gear. 72, the valve is positioned at the fully closed opening degree.

  Here, when the throttle valve 42 is urged in the closing direction by the return spring 76 as in the prior art, the direction in which the throttle valve 42 is opened after the throttle valve 42 is fully closed. 4, the fourth gear 72 does not start rotating immediately under the influence of the backlash with the third gear 70 as shown in FIG. 6. That is, there is a problem that a time delay occurs between when the throttle valve 42 is requested to open and when it is actually opened, resulting in poor response.

  On the other hand, when the throttle valve 42 is urged in the valve opening direction by the return spring 76, when the third gear 70 is driven in the direction in which the throttle valve 42 is opened after the throttle valve 42 is fully closed, FIG. 4, the fourth gear 72 starts rotating while following the rotation of the third gear 70 by the urging force of the return spring 76. That is, by urging the throttle valve 42 in the valve opening direction by the return spring 76, the throttle valve 42 starts to open immediately without being affected by the backlash of the third gear 70 and the fourth gear 72. .

  Further, a torque (pressure) in the valve closing direction acts on the throttle valve 42 by the flow of intake air. FIG. 8 is a graph showing the relationship between the pressure PB in the intake pipe (path) and the torque in the valve closing direction acting on the throttle valve 42. As shown in the figure, when the intake pipe pressure PB (indicated by a solid line) decreases (negative pressure increases), torque in the valve closing direction (indicated by a broken line) acts on the throttle valve 42. Such torque becomes resistance to opening the throttle valve 42, and the electric motor 44 needs to generate a large driving force.

  However, in this embodiment, since the throttle valve 42 is urged in the valve opening direction by the return spring 76, the torque in the valve closing direction acting on the throttle valve 76 by the flow of intake air and the return The urging force (torque in the valve opening direction) of the spring 76 can be canceled out, and thus the driving force required to open the throttle valve 42 can be reduced.

  As described above, in the first embodiment of the present invention, the return spring 76 for biasing the throttle valve 42 in the valve opening direction is provided, so that the throttle valve is opened from the fully closed opening degree. In addition, it is not affected by the backlash of the reduction gears (the third reduction gear 70 and the fourth reduction gear 72), so that the responsiveness until the throttle valve 42 is opened from the fully closed opening can be improved. Further, since the torque in the valve closing direction acting on the throttle valve 42 by the flow of the intake air cancels out the biasing force (torque in the valve opening direction) of the return spring 76, the throttle valve 42 is opened. The required driving force can be reduced, and the electric motor 44 that opens and closes the throttle valve 42 can be reduced in size.

  In the above description, the one end 76a of the return spring 76 is connected to the fourth gear 72. However, it may be connected to the throttle shaft 54, or there may be other members fixed to the throttle shaft 54. For example, it may be connected to it.

  Further, although the return spring 76 is a torsion coil spring, other types of springs may be used. Further, instead of the spring, other elastic bodies such as rubber may be used.

  As described above, in the first embodiment of the present invention, the throttle valve (42) disposed in the intake passage (22) of the general-purpose engine (10) and the throttle shaft (42) supporting the throttle valve (42). 54) and an actuator (electric motor 44) connected to the throttle shaft (54) via a reduction gear (reduction gear mechanism 58), and the reduction gear (58) is driven by driving the actuator (44). In the throttle device of a general-purpose engine that adjusts the intake air amount by opening and closing the throttle valve (42) and thus opening and closing the throttle valve (42), the throttle valve (42) is opened in the valve opening direction. An urging means (return spring 76) for urging is provided.

  More specifically, in the throttle device of the general-purpose engine, any one of the driven gear (fourth gear 72) and the throttle shaft (54) of the reduction gear (58) and the reduction gear (58) are provided. A return spring (76) for urging the throttle valve (42) in the valve opening direction is connected to a case (unit case 60. More specifically, a hook pin 78 projecting from the case). It was configured as follows.

  In the above description, the electric motor 44 is exemplified as the actuator for opening and closing the throttle valve 42. However, other actuators such as a rotary solenoid may be used.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view showing a general purpose engine throttle device according to a first embodiment of the present invention. It is a top view of a throttle body among the apparatuses shown in FIG. 3 is a cross-sectional view taken along line III-III in FIG. FIG. 4 is an enlarged side view of the return spring shown in FIG. 3. It is a schematic diagram of the 3rd gear shown in FIG. 3, a 4th gear, and a throttle valve. Similarly, it is a schematic diagram of a third gear, a fourth gear and a throttle valve shown in FIG. Similarly, it is a schematic diagram of a third gear, a fourth gear and a throttle valve shown in FIG. 2 is a graph showing the relationship between the pressure in the intake pipe (path) of the apparatus shown in FIG. 1 and the torque in the valve closing direction acting on the throttle valve.

Explanation of symbols

10 General-purpose engine 22 Intake passage 42 Throttle valve 44 Electric motor (actuator)
54 Throttle shaft 58 Reduction gear mechanism (reduction gear)
76 Return spring (biasing means)

Claims (1)

  A throttle valve disposed in an intake passage of a general-purpose engine, a throttle shaft that supports the throttle valve, and an actuator connected to the throttle shaft via a reduction gear, and driving the actuator to reduce the reduction gear In the throttle device of a general-purpose engine that adjusts the intake air amount by opening and closing the throttle valve and thereby opening and closing the throttle valve, biasing means for biasing the throttle valve in the valve opening direction is provided. A throttle device for a general-purpose engine characterized by comprising

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