JP4199689B2 - 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 according to an engine temperature detected by a temperature detecting element. 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 a stepping for controlling the opening of the choke valve in an auto choke device that controls the opening of the choke valve provided in the intake passage of the engine based on temperature information representative of the engine temperature at the time of engine start. A motor and means for setting a pulse rate of a drive pulse to be supplied to the stepping motor, so that a low value in a pulse rate setting range is used in a preset torque shortage factor environment of the stepping motor Composed.

  The torque shortage factor environment is a state where the temperature information is equal to or lower than a preset value, or a voltage of a driving power source of the stepping motor is equal to or less than a preset value.

  The drive power supply is electric power generated by a recoil starter provided in the engine.

  Further, in the present invention, the time until the choke is released is determined based on the temperature information.

  According to the present invention, when the stepping motor is in a torque shortage factor environment, the torque for driving the choke valve is increased by decreasing the pulse rate, that is, decreasing the motor speed by reducing the number of output pulses per unit time. Step-out can be prevented.

  Considering the low temperature state of the engine as a torque shortage factor environment, for example, torque can be secured in response to an increase in shaft friction that hinders the operation of the choke valve at low temperatures, and step-out can be prevented.

  Further, by considering the voltage drop of the drive power supply as a torque shortage factor environment, it is possible to secure the largest possible torque and prevent the step-out when the output torque of the stepping motor itself is lowered.

  Further, even when the power generated when manually rotating with the recoil starter is small, the choke valve can be driven with as much torque output as possible.

  Furthermore, it is possible to appropriately set the time until the choke release is reached based on temperature information representative of the engine temperature, and it is possible to control to the optimum air-fuel ratio according to the state of the engine.

  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.

  The engine 1 is connected to a generator 12, and the generator 12 is driven by the engine 1 to generate alternating current. This alternating current is once rectified and then controlled to a predetermined frequency (a commercial frequency of 50 or 60 Hz) by the inverter 13 to output a commercial power supply voltage.

  A generator 12 also serving as a starter motor of the engine 1 includes an outer rotor 12a in which a magnet is attached to an inner peripheral portion of a flywheel coupled to the crankshaft 1a of the engine 1, and a stator 12b around which a generator coil is wound. Become. 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 in accordance with 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 of the drive signal 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 starting opening of the choke valve 9.

  In the initialization of the stepping motor 11 in step S4, as will be described in detail later, the stepping motor 11 is caused to move the choke valve 9 to the fully closed side or the fully open side, and at least the step corresponding to the fully closed position. Number) of drive signals. As a result, the choke valve 9 is fully closed or fully opened. The starting opening of the choke valve 9 is determined based on the fully closed or fully opened position.

  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 steps of the drive signal 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 steps of the drive signal supplied to the stepping motor 11 every drive cycle (for example, 0.7 seconds) is equal to the drive cycle and the basic choke release time extended or shortened according to the increase or decrease of the engine speed. To be determined. When the number of steps of the drive signal supplied for each driving cycle is increased, the step can be quickly moved to the choke release side, and when the number of steps is reduced, the step is slowly moved to the choke release side.

  Thus, in step S7, the number of steps of the drive signal for each drive cycle supplied to the stepping motor 11 is determined in the operation until the choke valve 9 is half-opened from the starting opening degree, and in step S8, the determined number is determined. The stepping motor 11 is driven under this driving condition (the determined number of steps of the driving signal).

  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. This determination is made based on the number of steps of the drive signal supplied to the stepping motor 11 as with the determination of whether or not the half-open state has been reached.

  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. Also in step S11, as in 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 steps of the drive signal output to the stepping motor 11 for each drive cycle is calculated. And do. In step S12, the stepping motor 11 is driven with the determined motor drive condition (the determined number of steps of the drive signal). If it is determined that the choke valve 9 has been fully opened, the choke control ends.

  FIG. 3 is a detailed flowchart of initialization of the stepping motor 11 (step S4). In the figure, in step S41, the pulse rate of the stepping motor 11 is determined according to the engine temperature. An example of a table in which the pulse rate of the stepping motor 11 corresponding to the temperature is set is shown in FIG.

  In step S42, it is determined whether or not the starting opening determined in step S2 is less than a predetermined value (for example, half open). If the starting opening is less than half open, the process proceeds to step S43, and if the starting opening is not less than half open, the process proceeds to step S44.

  In step S43, the stepping motor 11 is initialized on the fully closed side of the choke valve 9. That is, the choke valve 9 is rotated to the fully closed side at the pulse rate determined in step S41. In step S44, the stepping motor 11 is initialized on the fully open side of the choke valve 9. That is, the choke valve 9 is rotated to the fully open side at the pulse rate determined in step S41.

  As described above, when the starting opening determined based on the engine temperature is on the fully closed side, the choke valve 9 is driven to the fully closed position, and the stepping motor 11 is initialized there. Further, when the starting opening degree determined based on the engine temperature is the fully open side, the choke valve 9 is driven to the fully open position, and the stepping motor 11 is initialized there. Since the initialization is performed on the side closer to the starting opening in this way, there is an effect that the choke valve 9 can be moved in a short time to the starting opening after the initialization.

  The reason why the pulse rate is set as a function of the engine temperature in the initialization of the stepping motor 11 is as follows. Since the stepping motor is controlled in an open loop, even if the rotation angle is deviated from a desired position as a result of step-out due to disturbance or a decrease in torque of the stepping motor, it cannot be detected.

  In particular, when the temperature is low, the frictional force of the shaft of the choke valve 9 tends to increase. If the frictional force in this case increases to about the output torque of the stepping motor 11, a step-out is likely to occur. Further, it is known that the stepping motor has a characteristic that the output torque decreases as the pulse rate increases, that is, as the pulse interval decreases.

  Therefore, as shown in FIG. 4, the pulse rate was determined by a function of the engine temperature. In FIG. 4, the pulse rate of the stepping motor 11 is set between the first rate R1 and the second rate R2. The pulse rate is set to the lowest first rate R1 when the temperature is lower than the first temperature TL, and is set to the highest second rate R2 when the temperature is higher than the second temperature TH higher than the first temperature TL. . And between 1st temperature TL and 2nd temperature TH, it sets so that a pulse rate may increase gradually from 1st rate R1 to 2nd rate R2 as engine temperature becomes high.

  Thus, when the engine temperature is low, the output rate is increased by decreasing the pulse rate. Thereby, step-out can be suppressed.

  The pulse rate of the stepping motor 11 is not limited to low only at low temperatures. The stepping motor 11 is not limited to a high pulse rate but may cause torque shortage due to other factors. For example, the output torque decreases even when the power supply voltage for driving the stepping motor 11 is insufficient. The power supply voltage is decreased when the voltage of the battery 25 is decreased or when the power is not sufficiently generated due to weak rotational force when the recoil starter is used. Therefore, this power supply voltage is detected, and when the power supply voltage is lower than a predetermined voltage, the pulse rate is reduced so that sufficient torque can be obtained.

  It should be noted that when the stepping motor 11 is initialized and when the choke valve 9 is moved to the starting opening, a torque shortage factor environment other than a low engine temperature or a low power supply voltage can be planned. An increase in friction due to deterioration over time is one of the factors that hinder the choke valve 9 from operating smoothly.

  FIG. 5 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 drive signal 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”. As can be understood from this figure, when the engine temperature is 60 ° or less, the starting opening is closer to full closing than half open, and therefore the stepping motor 11 is initialized on the fully closed side of the choke valve 9. Further, when the engine temperature is 60 ° or more, the starting opening degree is closer to the full opening than the half opening, so that the stepping motor 11 is initialized on the full opening side of the choke valve 9.

  FIG. 6 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.

  In the present embodiment, 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 flowchart which shows the process which drives to the initialization of a stepping motor, and a starting opening degree. It is a table which shows the example of the pulse rate of the stepping motor corresponding to engine temperature. 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.

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 based on temperature information representative of the engine temperature when the engine is started.
Means for setting a pulse rate of a drive pulse supplied to the stepping motor,
An auto choke device using a low value of a pulse rate setting range in a torque shortage factor environment of the stepping motor in which the temperature information is not more than a preset value . The auto choke device according to claim 1 , wherein the driving power source is electric power generated by a recoil starter provided in the engine . The time for the choke valve is moved from the opening at the start of the engine until the choke release opening, automatic choke apparatus according to claim 1, wherein Rukoto determined based on the temperature information.

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