JP4232968B2 - Auto choke device - Google Patents

Description

  The present invention relates to an auto choke device, and more particularly, to an auto choke device capable of performing good air-fuel ratio control corresponding to temperature against engine temperature rise after starting.

  An auto choke device used at the time of cold start of an engine controls a solenoid actuator and a diaphragm actuator that operate a choke valve in accordance with a temperature detected by a temperature detection element such as a thermostat. The engine can be stably started by controlling the air-fuel ratio in the direction of increasing the air-fuel mixture by the auto choke device at the cold start.

For example, Japanese Patent Laid-Open No. 5-280425 discloses a case where a cold state of an engine is detected by a sensor composed of a thermistor that outputs a detection signal corresponding to the temperature of a cylinder head, and the throttle valve is in a fully closed state. An auto choke device is disclosed in which the choke solenoid is automatically actuated only when it is cold, i.e., when it is necessary to activate the choke when starting the engine.
JP-A-5-280425

  As in the apparatus described in Patent Document 1, it is common to control a choke valve using a solenoid actuator. However, since the solenoid is controlled to be on or off, there is a problem that the choke becomes excessive near the end of the period in which the choke needs to be operated, that is, just before the choke is released.

  On the other hand, it is also attempted to control the choke valve continuously by using a bimetal as an actuator. However, since bimetals have poor responsiveness to temperature changes, the timing for releasing choke is delayed both after cold start and after restart at a high engine temperature, and as a result, sufficient output is obtained. There is a problem that it takes time.

  The present invention has been made in view of such problems, and an object of the present invention is to provide an auto choke device capable of finely controlling a choke valve following an engine temperature.

  The present invention relates to an auto choke device that controls the opening of a choke valve provided in an intake passage of an engine according to temperature information representative of the engine temperature at the time of starting the engine. Is determined based on temperature information representative of the engine temperature at the time of starting the engine, and an electric motor for controlling the opening of the choke valve is provided.

  Further, the present invention has a second feature in that the time until the choke is released by changing the opening degree of the choke valve from the opening degree at the time of starting the engine to the fully open state is determined based on the temperature information. .

  Further, according to the present invention, the engine is controlled to be converged to a preset reference rotational speed, and a time until the choke is released becomes shorter as the reference rotational speed becomes higher in accordance with the reference rotational speed. There is a third feature in that it is determined to be longer as it is lower.

  Further, the present invention has a fourth feature in that the choke valve is arranged in series with the throttle valve. Furthermore, the fifth feature is that the choke release is performed toward the opening target in two stages, and the operation time of the choke valve until reaching each opening target is set individually.

  According to the present invention, the opening degree of the choke valve at the start is determined and controlled according to the engine or the environmental temperature of the engine. In particular, according to the second feature, the time from the opening at the start of the engine to the choke valve fully open, that is, the time from the choke state to the choke release is determined according to the environmental temperature of the engine. Since the choke valve opening can be appropriately set according to the engine operating state represented by the engine temperature, the air-fuel ratio is controlled to the optimum. Further, since the choke state is gradually released by controlling the choke valve with an electric motor, it is possible to prevent the air-fuel ratio from becoming small due to excessive choke immediately before the choke valve is fully opened.

  Further, according to the third feature, for example, in an engine generator in which the engine can be shifted so that it can follow a load when it fluctuates, the choke is released early when the rotational speed changes to a higher level. When the transition is low, the choke is released later, so that the choke release time is appropriately corrected according to the operating state.

  According to the 4th characteristic, it arrange | positions along with a throttle valve in an intake pipe, and a structure is simple.

  Further, according to the fifth feature, since the time until the choke is released can be set finely, more appropriate start-up air-fuel ratio control according to the operating state can be performed.

  Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing a system configuration of an auto choke device according to an embodiment of the present invention. In the figure, an engine 1 is used as a drive source for a generator. The engine 1 is provided with a temperature sensor 2 for detecting the engine temperature. The temperature sensor 2 is provided in the cylinder head 2a, for example. Further, the cylinder head 2a is provided with an ignition plug 3, an intake valve 4, and an exhaust valve 5.

  A carburetor 7 is connected to the intake pipe 6 provided with the intake valve 4. The carburetor 7 includes a throttle valve 8 disposed on the downstream side and a choke valve 9 disposed on the upstream side. The throttle valve 8 is driven by a stepping motor 10 to be opened and closed, and the choke valve 9 is driven by a stepping motor 11 to be opened and closed.

  A generator 12 also serving as a starter motor (starter motor) for the engine 1 includes an outer rotor 12a in which a magnet is attached to an inner peripheral portion of a flywheel coupled to a crankshaft 1a of the engine 1, and a generator coil wound around the generator 12 The stator 12b. A recoil starter (not shown) for manual start can be connected to the crankshaft 1a.

  The outer rotor 12a of the generator 12 is provided with a reluctator 14 for detecting the ignition timing, and a pre-top dead center position detection sensor (BTDC sensor) 15 for detecting the reluctor 14 is provided around the rotor.

  The ignition timing of the spark plug 3 and the opening of the choke valve 9 are controlled by the operation control unit 16. The choke control unit 17 drives the stepping motor 11 according to the engine temperature detected by the temperature sensor 2 and the engine speed detected by the output of the BTDC sensor 15 so as to obtain an appropriate air-fuel ratio corresponding to the temperature. Actuate valve 9. The control of the choke control unit 17 will be further described later.

  The stepping motor 10 is controlled by an electronic governor so as to maintain the engine speed at a predetermined reference speed. This reference rotational speed is variable depending on the size of the load (electric load connected to the output side of the inverter 13).

  The ignition control unit 18 optimally controls the ignition timing based on the AC output waveforms of the BTDC sensor 15 and the generator 12. The waveform shaping units 19 and 20 respectively shape the output waveform of the BTDC sensor 15 and the AC output waveform of the generator 12. Although the ignition timing is controlled by the timing of the waveform supplied from the waveform shaping sections 19 and 20, it is not a main part of the present invention, so the details are omitted.

  The power source unit 21 forms a power source necessary for the operation control unit 16, and is a regulator for using the rectified voltage of the battery 25 and the generator 12 (the input side voltage of the inverter 13) as a control power source of a predetermined voltage. Including. The operation control unit 16 can be provided with a liquid crystal display 22 that displays the operation state of the generator 12 and the like. Further, an interface 24 for connecting the remote control device 23 can be provided so that the generator 12 can be remotely controlled. The choke control unit 17 and the ignition control unit 18 can be configured by a microcomputer.

  FIG. 2 is a flowchart showing the operation of the choke control unit 17. This process is started when the power supply unit 21 is energized by the power supplied from the battery 25. Further, when the battery 25 is overdischarged, the engine 1 is rotated by a recoil starter, and the power supply unit 21 is energized by the power generation output of the generator 12 at that time.

  First, in step S1, the temperature detected by the temperature sensor 2 is read. In step S2, the position (starting opening) of the choke valve 9 corresponding to the detected temperature is determined. The starting opening is read from a preset table, for example. The position of the choke valve 9 is represented by the number of steps supplied to the stepping motor 11.

  In step S3, the operation time (basic choke release time) until the choke release corresponding to the engine temperature is determined.

  In step S4, the stepping motor 11 is driven for initialization, and the stepping motor 11 is driven to rotate the choke valve 9 to the start opening.

  When the engine is started by driving the starter motor with a battery, the engine is started after the stepping motor 11 is initialized and the choke valve 9 is moved to the start opening. On the other hand, when power cannot be supplied from the battery, the stepping motor 11 is driven and ignited by the power generation output obtained by manual rotation by the recoil starter, so that the choke valve 9 drive and the engine start are performed almost simultaneously.

  Then, after the engine is started, in step S5, it is determined whether or not the choke valve 9 has reached half open. This determination is made based on the number of pulses supplied to the stepping motor 11. If the opening of the choke valve 9 is less than half open, the process proceeds to step S6, and the engine speed is detected. The engine speed can be detected based on the output period of the BTDC sensor 15, but the detection method may be any known method. In step S7, the motor drive conditions until the choke valve 9 reaches half open are determined.

  In the determination of the motor driving conditions until half open, the basic choke release time determined in step S3 (operation time from the start opening to half open) is corrected. In this correction, the basic choke release time is shortened as the engine speed increases, and the basic choke release time is extended as the engine speed decreases.

  The number of drive pulses supplied to the stepping motor 11 every drive cycle (for example, 0.7 seconds) is based on this drive cycle and the basic choke release time extended or shortened corresponding to the increase or decrease of the engine speed. It is determined. Increasing the number of pulses supplied per drive cycle can move quickly to the choke release side, and decreasing the number of pulse supplies per drive cycle can move slowly to the choke release side.

  In this way, the number of pulses for each driving cycle supplied to the stepping motor 11 in the operation until the choke valve 9 is half-opened is determined. In step S8, the determined motor driving condition (the determined number of driving pulses). Then, the stepping motor 11 is driven.

  If it is determined in step S5 that the choke valve 9 has reached half open, the process proceeds to step S9, and it is determined whether or not the choke valve 9 has reached full open. Similar to the determination of whether or not it is half open, this determination is made based on the number of pulses supplied to the stepping motor 11. If the opening of the choke valve 9 is less than full open, the process proceeds to step S10 and the engine speed is detected. In step S11, a motor driving condition until the choke valve 9 is fully opened is determined. In step S11 as well as step S7, the basic choke release time (operation time from half-open to full-open) is corrected by the engine speed, and the number of output drive pulses for each drive cycle for the stepping motor 11 is calculated. In step S12, the stepping motor 11 is driven with the determined motor driving condition (the determined number of pulses). If it is determined that the choke valve 9 has been fully opened, the choke control ends.

  FIG. 3 is a diagram showing the position of the choke valve 9 at each engine temperature at the time of engine start, that is, the starting opening degree by the number of steps of the stepping motor 11. In this example, the choke valve 9 is fully closed (number of steps = 110) when the engine temperature is in the range of minus 25 ° C. to 20 ° C., and the choke valve 9 is slightly opened when the engine temperature is 30 ° C. or higher. It has been. When the engine temperature is 60 ° C., the choke valve 9 is half open (the number of steps = 55). Above that, the choke valve 9 is opened step by step up to “35”.

  FIG. 4 is a diagram illustrating an example of the choke release time corresponding to the engine temperature. Here, an example of the basic choke release time when the engine speed is controlled by the electronic governor to be the reference speed 3300 rpm is shown. Therefore, when the reference rotational speed fluctuates due to fluctuations in the load connected to the generator 12, the basic choke release time (both operating time until half-opening and operating time from half-opening to full-opening) depends on the engine speed. It is corrected. That is, the choke release time is shortened when the load increases and the engine speed changes higher than the reference speed, and the choke release time when the load decreases and the engine speed changes lower than the reference speed. Lengthen. Thus, the choke release time is corrected so as to be appropriate according to the operating state of the generator 12, that is, the engine 1.

  FIG. 5 is a graphical representation of the example of FIG. As shown in this figure, the choke release time is determined by the engine temperature at the start.

  In this embodiment, an example in which a stepping motor is used as a choke valve drive source has been described. However, this is not limited to a stepping motor, and may be, for example, a servo motor.

  The engine temperature is represented by the temperature of the cylinder head 2a. However, the engine temperature for controlling the choke valve is not limited to the temperature at this position. For example, a temperature sensor may be attached to an oil pan or a water jacket for engine water cooling to detect the temperature of the lubricating oil or the temperature of the engine cooling water, thereby representing the engine temperature. In addition, the temperature information detected in the engine case portion that can represent the engine temperature can be used for the choke valve control of the present invention.

It is a block diagram which shows the system configuration | structure of the auto choke apparatus which concerns on one Embodiment of this invention. It is a flowchart which shows operation | movement of a choke control part. It is a figure which shows the position of the choke valve for every engine temperature at the time of engine starting. It is a figure which shows the example of the chalk cancellation | release time corresponding to engine temperature. It is a graph which shows the example of the chalk cancellation | release time corresponding to engine temperature.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Engine, 2 ... Temperature sensor, 6 ... Intake pipe, 7 ... Carbator, 8 ... Throttle valve, 9 ... Choke valve, 11 ... Stepping motor, 12 ... Generator, 13 ... Inverter, 17 ... Choke control part

Claims (3)

In an auto choke device having a choke valve provided in an intake passage of an engine and a stepping motor for controlling the opening of the choke valve according to temperature information representative of the engine temperature at the time of engine start,
While determining the opening of the choke valve when starting the engine based on temperature information representative of the engine temperature when starting the engine,
The time until the choke is released by changing the opening of the choke valve from the opening at the time of starting the engine to full opening is determined based on the temperature information,
The auto choke device, wherein the choke release is performed in accordance with respective predetermined operation times from an opening degree at the time of starting the engine to a half-open state and from a half-open state to a full-open state, and the two operation times are individually set. The engine is controlled to converge to a preset reference speed,
The time until the choke is released by changing the opening degree of the choke valve from the opening degree at the time of starting the engine to the fully open state is determined to be shorter as the reference rotational speed becomes higher and longer as the reference rotational speed becomes lower. The auto choke device according to claim 1, wherein   The auto choke device according to claim 1, wherein the choke valve is arranged in series with a throttle valve.

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