JP2015140672A - Auto choke device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an auto choke device for improving fuel consumption and exhaust gas property by performing a fast transition from a closed state to an open state of a choke valve.SOLUTION: An auto choke device having a choke valve 63 installed in an intake flow passage of an engine 1 so as to reduce a flow passage sectional area while being transmitted from an open state to a closed state comprises: choke valve driving means 130 capable of driving the choke valve to show a desired degree of opening; rotational speed detecting means 120 for detecting a rotational speed of an engine output shaft 10; temperature detecting means 110 for detecting a temperature of the engine; and control means 100 for holding a target opening degree map in which a target opening degree of the choke valve is set according to the rotational speed and the temperature and controlling the choke valve driving means so as to cause the opening degree of the choke valve to become the target opening degree.

Description

  The present invention relates to an auto choke device provided in a general-purpose engine, and more particularly, to an apparatus that improves the fuel consumption and exhaust gas properties by speeding up the transition of a choke valve from a closed state to an open state.

For example, in an engine that supplies fuel by a carburetor, such as an industrial general-purpose engine, it is necessary to squeeze the choke valve immediately after the cold start to temporarily enrich the mixture (choking).
Such choking is performed by closing the choke valve for a predetermined time of, for example, several seconds to several tens of seconds after the engine is started, and then the choke valve is opened during normal operation.

Conventionally, in order to improve user convenience, for example, a temperature sensing device such as a bimetal or wax provided in a cylinder head, a muffler, or the like is used to detect the warm-up state of the engine and automatically perform the choke valve opening operation An auto choke device as described above has been proposed.
However, bimetal or the like has a relatively slow response to temperature changes, and a delay in choke release timing becomes a problem during cold start and restart after warm-up.

Moreover, as a prior art regarding such an automatic opening operation of a choke valve, for example, Patent Document 1 describes an auto choke device that drives a choke valve using a stepping motor.
In Patent Document 1, the choke valve opening at the time of starting is determined according to the engine temperature, and a preset choke release time is corrected according to the engine opening, so that it is fully opened at the corrected release time. Describes that the choke valve is driven.
In Patent Document 2, a choke valve is opened and closed according to the opening and load of a throttle valve of a carburetor, thereby enabling variable fuel injection and realizing a desired air-fuel ratio under a wide range of operating conditions. It is described.

JP 2005-256757 A International Publication No. WO11 / 048871

During the above-described choking, the air-fuel ratio becomes richer than that during normal operation, so the fuel consumption and exhaust gas properties deteriorate. Therefore, there is a demand for the choke valve to be fully opened at an early stage to end choking and shift to normal operation.
However, when the opening operation of the choke valve is excessively advanced, ignition and combustion become unstable, and there is a concern about the occurrence of engine stall. For this reason, in the conventional auto choke device, it is necessary to set a sufficient choke release time in consideration of safety, and the choke tends to be excessive, and it is difficult to improve fuel consumption and exhaust gas.
However, in recent years, general-purpose engines mounted on generators and the like have been generally equipped with microcomputers for various types of control, and a technique for appropriately controlling a choke valve using such microcomputers has been obtained. If it is possible, the driving of the choke valve can be optimized to improve fuel consumption and exhaust gas.
An object of the present invention is to provide an auto choke device that improves the fuel consumption and exhaust gas properties by speeding up the transition of the choke valve from the closed state to the open state.

The present invention solves the above-described problems by the following means.
The invention according to claim 1 is an auto choke device having a choke valve that is provided in an intake flow path of an engine and reduces a cross-sectional area of the intake flow path by transitioning from an open state to a closed state, A choke valve driving means capable of driving the choke valve to have a desired opening; a rotational speed detecting means for detecting the rotational speed of the output shaft of the engine; and a temperature detecting means for detecting the temperature of the engine; Maintaining a target opening map in which the target opening of the choke valve is set according to the rotational speed and the temperature, and controlling the choke valve driving means so that the opening of the choke valve becomes the target opening. An auto choke device comprising a control means for controlling.
According to this, by setting the target opening degree of the choke valve from the target opening degree map based on the current engine temperature and speed, an appropriate choke valve can be obtained by feedback control following temperature rise and rotational fluctuation. The opening degree can be set, and the choke valve can be quickly and smoothly shifted to the fully open state.
As a result, the operating time in the excessive choking state (air-fuel ratio rich state) can be shortened, and fuel consumption and exhaust gas can be improved.
In addition, by opening the choke valve early, if the combustion becomes unstable and the rotation speed is reduced, the choke valve is controlled to move in the closing direction for stable operation. Can be secured.

According to a second aspect of the present invention, the control means continues the state in which the target opening set by the target opening map is changed according to a change in at least one of the rotational speed and the temperature for a predetermined time or more. 2. The auto choke device according to claim 1, wherein the choke valve is driven by the choke valve driving means only when the choke valve is driven.
The invention according to claim 3 is the auto choke according to claim 1 or 2, wherein the control means controls the choke valve driving means so that the opening degree of the choke valve is changed. Device.
According to each of these inventions, after changing the target opening, the engine speed cannot be maintained at the target opening, and control hunting that immediately returns to the original target opening is prevented. it can.

  As described above, according to the present invention, it is possible to provide an auto choke device that improves the fuel consumption and exhaust gas properties by speeding up the transition from the closed state to the open state of the choke valve.

It is sectional drawing which shows the structure of the general purpose engine in which the Example of the auto choke apparatus to which this invention is applied is provided. It is a block diagram which shows the structure of the auto choke apparatus of an Example. It is a flowchart which shows the control outline | summary of the auto choke apparatus of an Example.

  It is an object of the present invention to provide an auto choke device that improves the fuel consumption and exhaust gas properties by accelerating the transition from the closed state to the open state of the choke valve, and the target of the choke valve from the temperature of the cylinder head and the engine speed. The problem was solved by setting the target opening based on the map from which the opening is read and controlling the choke valve with a stepping motor so that the opening of the choke valve approaches the set target opening.

Embodiments of an auto choke device to which the present invention is applied will be described below.
The auto choke device according to the embodiment is applied to, for example, an industrial general-purpose engine mounted on a portable generator or the like.
FIG. 1 is a cross-sectional view showing a configuration of a general-purpose engine provided with an auto choke device of an embodiment.
The engine 1 is, for example, a single-cylinder four-stroke OHC industrial general-purpose engine that uses gasoline as fuel.
As shown in FIG. 1, the engine 1 includes a crankshaft 10, a piston 20, a connecting rod 30, a crankcase 40, a cylinder head 50, a carburetor 60, an air cleaner 70, a heat insulator 80, a muffler 90, and the like. .

The crankshaft 10 is an output shaft of the engine 1, and both ends thereof are rotatably supported by bearings.
In addition, a crank pin to which the large end portion of the connecting rod 30 is connected, a crank arm that supports the crank pin, and a crank weight are formed at an intermediate portion of the crank shaft 10.
The piston 20 reciprocates in the cylinder and transmits the pressure of the combustion gas to the crankshaft 10.
The connecting rod 30 has a small end portion connected to the piston 20 via the piston pin and a large end portion connected to the crank pin of the crankshaft 10, and connects them.

The crankcase 40 is a container-like member that houses the crankshaft 10 and the like, and is a part that constitutes the main body of the engine 1.
In the upper part of the crankcase 40, a cylinder part 41 is formed in which the piston 20 is inserted and reciprocates inside. The cylinder part 41 has a central axis arranged substantially along the vertical direction.
A cylindrical cylinder sleeve 42 is inserted on the inner diameter side of the cylinder portion 41, and the piston 20 is inserted therein.

The cylinder head 50 is provided at an upper end portion of the cylinder portion 41 and is fastened to the cylinder portion 41 with a head gasket sandwiched therebetween.
The cylinder head 50 includes a combustion chamber 51, an intake port 52, an exhaust port 53, an intake valve 54, an exhaust valve 55, and the like.
The combustion chamber 51 is a recess formed by recessing a region facing the crown surface of the piston 20 of the cylinder head 50, and is a portion where the air-fuel mixture is combusted inside.
The combustion chamber 51 is provided with a spark plug (not shown).

The intake port 52 is a passage through which the air-fuel mixture generated in the carburetor 60 (in which fuel atomized and vaporized exists in the combustion air) is introduced into the combustion chamber 51.
The inlet of the intake port 52 opens to the side surface of the cylinder head 50 on the carburetor 60 side, and the outlet opens to the upper portion of the combustion chamber 51. The intake port 52 is formed in a curved portion at the middle portion thereof.

The exhaust port 53 is a passage that produces burned gas (exhaust gas) from the combustion chamber 51.
The inlet of the exhaust port 53 opens to the upper portion of the combustion chamber 51 opposite to the intake port 52, and the outlet opens to the side surface of the cylinder head 50 on the muffler 100 side. It is curved.

  The intake valve 54 and the exhaust valve 55 are driven by a valve drive system such as a camshaft and rocker arms 54a and 55a (not shown), and open and close the ends of the intake port 52 and the exhaust port 53 on the combustion chamber 51 side, respectively. It is.

The carburetor 60 supplies an air-fuel mixture to the engine 1.
The carburetor 60 is formed with a venturi portion 62 having an inner diameter smaller than that of the other portion at a middle portion of a passage (barrel) 61 through which fresh air passes, and a choke valve 63 and a throttle valve 64 are provided on the upstream side and the downstream side, respectively. It is arranged and configured.
The choke valve 63 and the throttle valve 64 are butterfly valves that can swing around a rotation shaft that is disposed substantially horizontally.
The choke valve 63 performs choking to reduce the flow passage cross-sectional area of the passage 61 when the engine 1 is started, and enriches the air-fuel mixture to improve ignitability and combustion stability.

  The air cleaner 70 is provided on the inlet side of the carburetor 60 and removes dust and the like from the introduced outside air and introduces it into the passage 61 of the carburetor 60.

  The heat insulator 80 is a member that is fixed in a state of being sandwiched between the cylinder head 50 and the carburetor 60 in order to prevent the carburetor 60 from being heated by heat conduction from the cylinder head 50.

  The muffler 90 reduces the acoustic energy of the exhaust gas discharged from the exhaust port 53 and discharges it to the outside.

The engine 1 described above includes an auto choke device described below.
FIG. 2 is a block diagram illustrating a configuration of the auto choke device according to the embodiment.
As shown in FIG. 2, the auto choke apparatus includes a choke control unit 100, a head temperature sensor 110, an engine rotation sensor 120, an actuator 130, and the like.

The choke control unit 100 controls the actuator 130 based on outputs from the head temperature sensor 110 and the engine rotation sensor 120.
The choke control unit 100 is a microcomputer having information processing means such as a CPU, storage means such as RAM and ROM, an input / output interface, and a bus connecting them.
The storage means holds a map (data table) from which the target opening degree of the choke valve 63 is read from the engine temperature and the rotational speed.
The function of the choke control unit 100 can be provided as a function of a microcomputer having other functions such as power generation control of a generator.

  The head temperature sensor 110 measures a temperature in the cylinder head 50 in the vicinity of the intake port 52 (hereinafter referred to as “head temperature”), which is a part where the influence of the intake air temperature is easily reflected.

The engine rotation sensor 120 detects the number of rotations (rotational speed) of the crankshaft 10.
The engine rotation sensor 120 detects the number of rotations of the crankshaft 10 based on, for example, the period of the ignition primary signal output from the ignition coil.

The actuator 130 drives the choke valve 63 to open and close.
The actuator 130 can adjust the opening of the choke valve 63 with an intermediate opening so as to coincide with an arbitrary target opening.
The actuator 130 includes, for example, a stepping motor and a reduction gear train.

Next, an outline of control of the auto choke device of the embodiment will be described.
FIG. 3 is a flowchart showing an outline of control of the auto choke device of the embodiment. This control is started every time the engine is started.
Hereinafter, the steps will be described step by step.

<Step S01: Initialization>
The choke control unit 100 sets the choke valve 63 to a fully closed state in which the flow path cross-sectional area is the smallest, and sets the opening degree of the choke valve 63 at this time as the reference position (opening degree 0%).
Thereafter, the process proceeds to step S02.

<Step S02: Head Temperature Measurement>
The choke control unit 100 acquires information related to the temperature of the cylinder head 50 (head temperature) from the head temperature sensor 110.
Thereafter, the process proceeds to step S03.

<Step S03: Head Temperature Determination>
If the head temperature is 0 ° C. or lower, the process proceeds to step S11. If the head temperature is higher than 0 ° C., the process proceeds to step S04.

<Step S04: Head Temperature Determination>
If the head temperature is 10 ° C. or lower, the process proceeds to step S21. If the head temperature is higher than 10 ° C., the process proceeds to step S05.

<Step S05: Head Temperature Determination>
If the head temperature is 25 ° C. or lower, the process proceeds to step S31. If the head temperature is higher than 25 ° C., the process proceeds to step S06.

<Step S06: Head Temperature Determination>
If the head temperature is 50 ° C. or lower, the process proceeds to step S41. If the head temperature is higher than 50 ° C., the process proceeds to step S07.

<Step S07: Choke opening degree 100%>
The choke control unit 100 controls the actuator 130 by setting the target opening degree to 100%, and shifts the choke valve 63 to fully open (opening degree 100%).
Thereafter, the series of processing is terminated.

<Step S11: Number of revolutions determination>
When the engine speed is 200 rpm or less, the process proceeds to step S15, and when it exceeds 200 rpm, the process proceeds to step S12.

<Step S12: Judgment of rotational speed>
When the engine speed is 300 rpm or less, the process proceeds to step S16, and when it exceeds 300 rpm, the process proceeds to step S13.

<Step S13: Judgment of rotational speed>
If the engine speed is 400 rpm or less, the process proceeds to step S17, and if it exceeds 400 rpm, the process proceeds to step S14.

<Step S14: Judgment of rotational speed>
If the engine speed is 500 rpm or less, the process proceeds to step S18. If the engine speed exceeds 500 rpm, the process proceeds to step S19.

<Step S15: Choke opening 0%>
The choke control unit 100 controls the actuator 130 by setting the target opening degree to 0%, fully closes the choke valve 63 (opening degree 0%), returns to step S02, and repeats the subsequent processing.

<Step S16: Choke opening 10%>
The choke control unit 100 controls the actuator 130 by setting the target opening to 10%, sets the choke valve 63 to 10%, returns to step S02, and repeats the subsequent processing.

<Step S17: Choke opening 20%>
The choke control unit 100 controls the actuator 130 by setting the target opening to 20%, sets the choke valve 63 to 20%, returns to step S02, and repeats the subsequent processing.

<Step S18: Choke opening 25%>
The choke control unit 100 controls the actuator 130 by setting the target opening to 25%, sets the choke valve 63 to 25%, returns to step S02, and repeats the subsequent processing.

<Step S19: Choke opening 30%>
The choke control unit 100 controls the actuator 130 by setting the target opening to 30%, sets the choke valve 63 to 30%, returns to step S02, and repeats the subsequent processing.

<Step S21: Judgment of rotational speed>
When the engine speed is 200 rpm or less, the process proceeds to step S25, and when it exceeds 200 rpm, the process proceeds to step S22.

<Step S22: Number of rotations determination>
If the engine speed is 300 rpm or less, the process proceeds to step S26, and if it exceeds 300 rpm, the process proceeds to step S23.

<Step S23: Revolution Determination>
When the engine speed is 400 rpm or less, the process proceeds to step S27, and when it exceeds 400 rpm, the process proceeds to step S24.

<Step S24: Judgment of rotational speed>
When the engine speed is 500 rpm or less, the process proceeds to step S28, and when it exceeds 500 rpm, the process proceeds to step S29.

<Step S25: Choke opening 25%>
The choke control unit 100 controls the actuator 130 by setting the target opening to 25%, sets the choke valve 63 to 25%, returns to step S02, and repeats the subsequent processing.

<Step S26: Choke opening 30%>
The choke control unit 100 controls the actuator 130 by setting the target opening to 30%, sets the choke valve 63 to 30%, returns to step S02, and repeats the subsequent processing.

<Step S27: Choke opening 35%>
The choke control unit 100 controls the actuator 130 by setting the target opening to 35%, sets the choke valve 63 to 35%, returns to step S02, and repeats the subsequent processing.

<Step S28: Choke opening 40%>
The choke control unit 100 controls the actuator 130 by setting the target opening to 40%, sets the choke valve 63 to 40%, returns to step S02, and repeats the subsequent processing.

<Step S29: Choke opening 45%>
The choke control unit 100 controls the actuator 130 by setting the target opening to 45%, sets the choke valve 63 to 45%, returns to step S02, and repeats the subsequent processing.

<Step S31: Revolution Determination>
When the engine speed is 200 rpm or less, the process proceeds to step S35, and when it exceeds 200 rpm, the process proceeds to step S32.

<Step S32: Judgment of rotational speed>
If the engine speed is 300 rpm or less, the process proceeds to step S36, and if it is greater than 300 rpm, the process proceeds to step S33.

<Step S33: Revolution Determination>
When the engine speed is 400 rpm or less, the process proceeds to step S37, and when it exceeds 400 rpm, the process proceeds to step S34.

<Step S34: Judgment of rotational speed>
When the engine speed is 500 rpm or less, the process proceeds to step S38, and when it exceeds 500 rpm, the process proceeds to step S39.

<Step S35: Choke opening 50%>
The choke control unit 100 controls the actuator 130 by setting the target opening to 50%, sets the choke valve 63 to 50%, returns to step S02, and repeats the subsequent processing.

<Step S36: Choke opening 55%>
The choke control unit 100 controls the actuator 130 by setting the target opening to 55%, sets the choke valve 63 to 55%, returns to step S02, and repeats the subsequent processing.

<Step S37: Choke opening 60%>
The choke control unit 100 controls the actuator 130 by setting the target opening to 60%, sets the choke valve 63 to 60%, returns to step S02, and repeats the subsequent processing.

<Step S38: Choke opening 70%>
The choke control unit 100 controls the actuator 130 by setting the target opening to 70%, sets the choke valve 63 to 70%, returns to step S02, and repeats the subsequent processing.

<Step S39: Choke opening degree 75%>
The choke control unit 100 controls the actuator 130 by setting the target opening to 75%, sets the choke valve 63 to 75%, returns to step S02, and repeats the subsequent processing.

<Step S41: Revolution Determination>
If the engine speed is 200 rpm or less, the process proceeds to step S43, and if it exceeds 200 rpm, the process proceeds to step S42.

<Step S42: Rotational Speed Judgment>
If the engine speed is 300 rpm or less, the process proceeds to step S44, and if it exceeds 300 rpm, the process proceeds to step S45.

<Step S43: Choke opening 90%>
The choke control unit 100 controls the actuator 130 by setting the target opening to 90%, sets the choke valve 63 to 90%, returns to step S02, and repeats the subsequent processing.

<Step S44: Choke opening degree 95%>
The choke control unit 100 controls the actuator 130 by setting the target opening to 95%, sets the choke valve 63 to 95%, returns to step S02, and repeats the subsequent processing.

<Step S45: Choke opening degree 100%>
The choke control unit 100 controls the actuator 130 by setting the target opening degree to 100%, and shifts the choke valve 63 to fully open (opening degree 100%).
Thereafter, the series of processing is terminated.

In the control described above, the relationship between the head temperature, the engine speed, and the target opening of the choke valve 63 is read from a map held in the storage means of the choke control unit 100.
Also, in order to prevent hunting in which the choke valve opening is frequently changed, the target opening should be changed (the previous target opening (actual choke valve opening) is different from the current target opening. The choke valve 63 is driven only when a predetermined time (for example, several seconds) continues.

According to the embodiment described above, the choke valve target opening is determined from the map of the target opening held by the choke control unit 100 based on the current temperature of the cylinder head 50 of the engine 1 and the rotation speed of the crankshaft 10. Thus, it is possible to set an appropriate opening of the choke valve 63 by feedback control that follows temperature rise and rotational fluctuation. As a result, the choke valve 63 can be quickly and smoothly shifted to the fully open state.
As a result, the operating time in the excessive choking state (air-fuel ratio rich state) can be shortened, and fuel consumption and exhaust gas can be improved.
Further, when the choke valve 63 is opened early, if the combustion becomes unstable and the rotation speed is reduced, the choke valve 63 is controlled so as to be slightly operated in the closing direction. Stability can be ensured.
Further, by driving the choke valve 63 only when the state in which the target opening degree should be changed continues for a predetermined time or more, it is possible to prevent the control hunting and to drive the choke valve 63 stably.

(Modification)
The present invention is not limited to the embodiments described above, and various modifications and changes are possible, and these are also within the technical scope of the present invention.
For example, the configurations of the engine and the choke valve control device are not limited to the above-described embodiments, and can be changed as appropriate.
Further, the correlation between the temperature, the rotational speed and the choke valve opening in the embodiment is also an example, and can be appropriately changed according to the characteristics of the engine to be applied.
Further, as the engine temperature, the temperature of a part other than the cylinder head or the temperature of the lubricating oil may be used.
In the embodiment, the choke valve is driven only when the state in which the target opening should be changed continues for a predetermined time or more as a countermeasure against hunting. Instead of this or in combination with this, the target opening is When the degree is changed, the choke valve 63 may be driven at a very low speed to change the opening degree.

DESCRIPTION OF SYMBOLS 1 Engine 10 Crankshaft 20 Piston 30 Connecting rod 40 Crankcase 41 Cylinder part 42 Cylinder sleeve 50 Cylinder head 51 Combustion chamber 52 Intake port 53 Exhaust port 54 Intake valve 54a Rocker arm 55 Exhaust valve 55a Rocker arm 60 Carburetor 61 Passage 62 Venturi part 63 Choke valve 64 Throttle valve 70 Air cleaner 80 Heat insulator 90 Muffler 100 Choke control unit 110 Head temperature sensor 120 Engine rotation sensor 130 Actuator

Claims (3)

An auto choke device having a choke valve that is provided in an intake passage of an engine and reduces a cross-sectional area of the intake passage by transitioning from an open state to a closed state,
Choke valve driving means capable of driving the choke valve to have a desired opening;
Rotation speed detection means for detecting the rotation speed of the output shaft of the engine;
Temperature detecting means for detecting the temperature of the engine;
Maintaining a target opening map in which the target opening of the choke valve is set according to the rotational speed and the temperature, and controlling the choke valve driving means so that the opening of the choke valve becomes the target opening. An auto choke device comprising: control means for controlling. The control means drives the choke valve only when a state in which the target opening set by the target opening map is changed according to a change in at least one of the rotational speed and the temperature continues for a predetermined time or more. The auto choke device according to claim 1, wherein the choke valve is driven by means. The auto choke device according to claim 1 or 2, wherein the control means controls the choke valve driving means so that an opening degree of the choke valve is changed.

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