JP2005264819A - Auto choke device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform minute control of a choke valve suitable for the operating state of an engine. <P>SOLUTION: The choke valve 9 is provided in series with a throttle valve 9 on an intake pipe 6. The opening of the choke valve 9 is controlled by a stepping motor 11. The choke valve opening (starting opening) at the start of the engine is determined according to the temperature of the engine. The driving pulse rate of the stepping motor 11 is also determined according to the temperature of the engine. When the engine temperature is lower than engine temperature TL, the pulse rate is set to a first rate lowest in a setting range. The pulse rate is set gradually larger up to a second rate TH according to the engine temperature. When carrying out choke release gradually in warming up, the pulse rate is lowered to obtain choke opening of high accuracy with high torque. <P>COPYRIGHT: (C)2005,JPO&NCIPI

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 a choke valve provided in an intake passage of the engine based on temperature information representative of the engine temperature when the engine is started. A motor and means for setting a pulse rate of a drive pulse to be supplied to the stepping motor, the stepping motor is initialized on the fully closed side or the fully open side of the choke valve, and the pulse rate setting means includes In the initialization of the stepping motor when the engine starting power is turned on, the first feature is that the pulse rate of the stepping motor is set larger than that during the warm-up operation after the initialization.

  A second feature is that a pulse rate at the time of initialization of the stepping motor is determined based on the temperature information.

  Further, the present invention is characterized in that the starting opening of the choke valve is determined based on the temperature information, and a large pulse rate at the time of initialization is maintained until the choke valve moves to the starting opening. There are three features.

  In addition, the present invention has a fourth feature in that a full open command for driving the choke valve to the full open side is output at a predetermined timing after the choke state by the choke valve is released.

  According to the present invention, initialization of a stepping motor driven in an open loop can be performed quickly at a large pulse rate, and stable opening degree adjustment is achieved by lowering the pulse rate and obtaining a large torque during warm-up operation. It can be performed.

  The choke valve can be quickly moved from the initialization position of the stepping motor to an appropriate starting opening degree corresponding to the temperature.

  Even if a step-out occurs in the process of moving the choke valve to the starting opening, etc., and the choke valve does not actually fully open after the warm-up is completed, it will be The choke valve can be reliably moved to the fully open position by the output fully open command.

  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 a 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. The pulse rate of the stepping motor 11 when the initialization and the choke valve 9 are moved to the starting opening, that is, the number of output pulses per unit time, is set larger than the pulse rate in the choke release operation during the warm-up operation. Since the stepping motor 11 is driven in an open loop, the pulse rate is set to be large at the time of initialization and movement to the starting opening where it is desired that the choke valve 9 operate quickly.

  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.

  If the choke valve 9 is moved to the starting opening, the pulse rate of the stepping motor 11 during the warm-up operation is determined in step S5. The pulse rate during the warm-up operation is set to a fixed value lower than the pulse rate during the movement up to the initialization and start opening. During the warm-up operation, the choke valve 9 is slowly opened over the basic choke release time, so that the stepping motor 11 is not required to be driven at high speed regardless of the engine temperature. Therefore, the pulse rate is set low so that the stepping motor 11 is reliably driven with sufficient torque according to the supply of the drive pulse during the warm-up operation.

  Then, after the engine is started, in step S6, 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 S7, 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 S8, the motor drive conditions until the choke valve 9 reaches half open are determined.

  In determining the motor driving conditions until half open, the basic choke release time determined in step S3 (operation time from 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.

  As described above, in step S8, 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, and in step S9, this determined drive is determined. The stepping motor 11 is driven under conditions (the determined number of steps of the drive signal).

  If it is determined in step S6 that the choke valve 9 has reached half open, the process proceeds to step S10 to determine whether 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 S11 and the engine speed is detected. In step S12, a motor driving condition until the choke valve 9 is fully opened is determined. In step S12, as in step S8, the basic choke release time (operation time from half-open to full-open) based on the engine speed is corrected, 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 S13, the stepping motor 11 is driven under 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.

  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 torque reduction 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. It is also 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.

  As described above, when the starting opening determined based on the engine temperature is 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.

  By the way, a stepping motor that is normally used may cause a step-out because the rotation of the rotor cannot catch up with excitation when the pulse rate is large in the relationship between the output torque and the pulse rate. In this case, in the stepping motor that is open-controlled, the rotor does not rotate by a desired angle corresponding to the number of steps of the applied drive signal. That is, when the choke is released, the choke valve 9 may not be fully opened due to the step-out even though the driving signal corresponding to the number of steps corresponding to the fully open is sent to the stepping motor 11.

  Therefore, after it is determined that the choke valve 9 is fully opened (after outputting a drive signal having a number of steps corresponding to the fully opened state), a control for periodically maintaining this fully opened state (hereinafter referred to as “fully opened feed control”). ) Was started.

  FIG. 5 is a flowchart showing main processing of the choke control unit for full opening feed control. In step S20, it is determined whether or not it is a full-open feed cycle for supplying a drive signal to the stepping motor 11 in full-open feed control. The fully open feed period can be determined by determining whether or not the timer means is provided with a timer means of, for example, 2 seconds in the choke controller 17 and the timer means has timed out. If it is a scheduled full-open feed cycle, the process proceeds to step S21 to output a command (full-open command) to the stepping motor 11 for full-open feed. That is, a preset number of drive signals for moving the choke valve 9 to the fully open side are sent to the stepping motor 11. The number of drive signals for full opening feed is, for example, 5 steps.

  It should be noted that the fully-open feed may be performed at a predetermined timing after the engine is started, and is not necessarily limited to one that is periodically performed.

  FIG. 6 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. 7 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 table which shows the example of the pulse rate of the stepping motor corresponding to engine temperature. 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 flowchart of the full open feed control which drives a choke valve to a full open side periodically. 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 (4)

In the auto choke device that controls the opening degree of the choke valve provided in the intake passage of the engine based on temperature information representative of the engine temperature when starting the engine,
A stepping motor for controlling the opening of the choke valve;
Means for setting a pulse rate of a drive pulse supplied to the stepping motor,
Initializing the stepping motor on the fully closed side or fully open side of the choke valve,
The auto choke characterized in that the pulse rate setting means sets the pulse rate of the stepping motor larger in the initialization of the stepping motor when the engine starting power is turned on than in the warm-up operation after the initialization. apparatus.   The auto choke device according to claim 1, wherein a pulse rate at the time of initialization of the stepping motor is determined based on the temperature information.   The start pulse of the choke valve is determined based on the temperature information, and a large pulse rate at the time of initialization is maintained until the choke valve moves to the start valve opening. Auto choke device.   4. The auto choke device according to claim 3, wherein a full open command for driving the choke valve to the full open side is output at a predetermined timing after the choke state by the choke valve is released.

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