JP4169193B2 - Engine driven work machine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an engine-driven work machine, and more particularly, to an engine-driven work machine that facilitates engine starting.
[0002]
[Prior art]
Engine-driven work machines such as a lawn mower that drives a blade cutter with an engine and a snow remover that drives an auger with an engine are known. In this type of work machine, when the engine is started by a starter motor, a starting torque sufficient to overcome the top dead center of the compression stroke of the engine is required when the engine is started. If the output of the starter motor is increased, it is possible to start with a sufficient margin, but on the other hand, it is also conceivable to reduce the influence of the load torque at the start. For example, Japanese Patent Laid-Open No. 7-71350 proposes a starting device that once rotates a starter motor in a direction of decreasing load torque and then rotates the starter motor in a normal engine rotation direction. According to this device, the compression stroke can be overcome by utilizing the inertial force obtained by starting the rotation from the light load position and increasing the rotational speed to some extent.
[0003]
[Problems to be solved by the invention]
In the starting device described in the above-mentioned publication, it is necessary to rotate the load once in the direction in which the load is reduced, that is, to reverse the engine. Therefore, there is an interval between the starting operation and the actual starting of the engine. Therefore, there is a problem that the operator feels uncomfortable and that it takes time to start practically.
[0004]
In addition, when using a generator combined motor as a starter motor, especially when the generator winding and the starter winding are shared, the starting torque of the motor is increased by increasing the diameter of the winding due to the power generation capacity. There is also a limitation that cannot be increased. This is because the power generation output decreases when the diameter of the winding is increased.
[0005]
An object of the present invention is to provide an engine-driven work machine that can solve the above-described problems and reduce the engine starting torque.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides an engine driven working machine in which an output shaft of an engine that drives a load is connected to a rotating shaft of a generator / motor. The first feature is that the point is detected, and when the compression top dead center is detected, the winding of the generator / motor is short-circuited to apply the electric brake.
[0007]
According to the first feature, since the electric brake is suddenly applied at the compression top dead center, the engine can be stopped at the crank angle immediately after passing through the compression top dead center.
[0008]
Further, the present invention operates the electric generator as a motor in response to the engine stop instruction to operate the generator / motor as a motor in accordance with a fine speed target value that is lower than the cranking rotational speed of the engine. There is a second feature in that it is configured to energize.
[0009]
According to the second feature, when the generator motor is operated as a motor by setting a low target rotation speed, regenerative braking works and the engine speed is rapidly reduced. Thus, since the electric brake is applied after the speed is reduced, the engine can be stopped at a crank angle immediately after passing through the compression top dead center with higher accuracy.
[0010]
According to a third aspect of the present invention, the compression top dead center detecting means is configured to detect the compression top dead center of the engine based on a current waveform of the generator / motor that is rotating at a low speed. There are features.
[0011]
In the present invention, the compression top dead center detection means determines a current peak based on the current waveform during the low-speed rotation as a temporary compression top dead center, and determines a plurality of the temporary compression top dead centers, And a means for estimating a next compression top dead center based on an interval between a plurality of temporary compression top dead centers, wherein the electric brake is configured to start energizing at the estimated compression top dead center. There is a fourth feature in this point. According to the third and fourth characteristics, the compression top dead center can be detected as a point in time when the motor current representing the load at the compression top dead center increases.
[0012]
Further, the present invention has a fifth feature in that the engine is operated at a substantially constant speed, and a lawn mowing blade cutter or a snow removing auger is connected to the output shaft of the engine as a work tool. According to the fifth feature, the blade cutter of the lawn mower and the auger of the snowplow having a large moment of inertia can be quickly stopped.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 2 is an overall perspective view of a lawn mower as an engine-driven working machine according to an embodiment of the present invention, and FIG. 3 is a plan view of a main part of the lawn mower. In FIG. 2, a pair of front wheels Wf, Wf are suspended at the front portion of the cutter housing 1 of the lawn mower, and a pair of rear wheels Wr, Wr are suspended at the rear portion. A vertical engine E is mounted at the center of the cutter housing 1, and an engine cover C is placed on the upper projecting portion of the engine E. Further, on both sides of the rear portion of the cutter housing 1, there are provided operating handles H extending rearward and rearwardly, and further, on the rear portion of the cutter housing 1, a glass bag B for storing the cut grass is provided.
[0014]
In FIG. 3, the center portion of the cutter housing 1 is a hollow cylindrical space whose bottom surface, that is, the ground side is open, and a cutter chamber 3 in which a blade cutter (work machine main body) 4 is accommodated is formed. The blade cutter 4 is connected to the crankshaft 5 of the engine E via a clutch (not shown), and is driven by the engine to rotate in the cutter chamber 3. A rotor of a starter motor / generator, which will be described later, is connected to the end, that is, the upper end of the crankshaft 5 opposite to the side to which the blade cutter 4 is connected.
[0015]
On the right side of the cutter housing 1 in the direction of travel, a turf discharge port 2 is formed extending rearward from the outlet of the cutter chamber 3 and leading to the glass bag B. The turf and the like cut by the blade cutter 4 are collected in the glass bag B through the turf discharge port 2.
[0016]
Rear wheel support members 14, 14 are disposed on the left and right sides of the rear portion of the cutter housing 1, and axles 16, 16 of the rear wheels Wr, Wr are mounted on the support members 14, 14. The left and right support members 14 and 14 are coupled to each other by a connecting shaft 19, and output shafts 17 and 18 are provided in parallel with the connecting shaft 19. One end of the output shafts 17 and 18 is coupled to the motor 7, and the other end of the output shafts 17 and 18 extends to the support members 14 and 14 side of the rear wheels Wr and Wr via the reduction gear mechanism 8, respectively. It is connected to axles 16 and 16.
[0017]
A recoil starter (not shown) is accommodated in the engine cover C that covers the upper portion of the engine E. The engine cover C holds a starter grip 15 that is coupled to a starter rope (not shown) of a recoil starter.
[0018]
FIG. 4 is a block diagram showing the overall system of the lawn mower. In the figure, a generator G is connected to the engine E. The generator G is, for example, an outer rotor type three-phase AC generator and also serves as a starter motor. A control circuit 10 is connected to the generator G, and a battery 27 is connected to the control circuit 10. The control circuit 10 includes a rectifier circuit and a regulator described later. When the generator G operates as a starter motor, power is supplied from the battery 27 via the control circuit 10. On the other hand, when the generator G generates power, the power generation output is connected to the battery 27 via the control circuit 10, and the battery 27 is charged.
[0019]
Connected to the control circuit 10 is an engine operation switch 33 for instructing start and stop of the engine E. The engine operation switch 33 is provided above the operation handle H. The motor 7 for driving the rear wheel Wr is controlled by a drive circuit (not shown) supplied with power from the battery 27 so as to maintain the target rotational speed.
[0020]
FIG. 5 is an exploded front view showing an example of the generator G. The generator G includes a flywheel rotor 20 formed in the shape of a bowl with a bottomed cylinder, 18 permanent magnets 21 arranged on the inner peripheral surface of the rotor 20, and the rotor 20 facing the magnet 21. And a stator 22 disposed on the inner periphery. The rotor 20 is provided with a sleeve 23 coupled to the crankshaft 5 of the engine E. The magnet 21 is configured such that the N pole and the S pole are polarized on the outer peripheral side and the inner peripheral side, and the magnets 21 adjacent to each other face different polarities. The stator core 24 of the stator 22 includes 27 salient poles 25 that extend radially and are arranged to face the inner peripheral side surface of the magnet 21. A winding 26 is wound around each salient pole 25.
[0021]
When the generator G operates as a motor, it is driven by sensorless control that does not have a rotor pole position detection sensor. Therefore, during the rotation of the rotor, the position of the rotor magnetic pole is detected from the back electromotive voltage induced in the winding 26 of each phase, and at the time of start-up, the position of the rotor magnetic pole is converted into the relative current of each phase of the generator G. Estimate based on. For example, the magnetic pole is estimated from the ratio of currents flowing in the U phase and the W phase, respectively. This activation technique is known as “vector control”. In addition, by providing a magnetic sensor or the like for detecting the position of the rotor magnetic pole, control may be performed based on the detection signal of the sensor from the time of startup to during operation.
[0022]
FIG. 6 is a circuit diagram illustrating an example of the control circuit 10. In the figure, the control circuit 10 has a switching circuit 28. The switching circuit 28 includes six MOSFETs or metal oxide semiconductor field effect transistors (hereinafter simply “FETs”) 281 to 286. The FETs 281 to 283 are disposed on the upper side, and the FETs 284 to 286 are disposed on the lower side. Flyback diodes D1, D2, D3, D4, D5, and D6 are connected in parallel to the FETs 281 to 286, respectively. A driver 29 for applying a driving voltage to the gates of the FETs 281 to 286 is provided.
[0023]
The driver 29 sequentially applies drive voltages to the gates of the FETs 281 to 286 when the generator G is used as a starter motor. The arithmetic unit 30 that can be configured by a DSP has a function of determining a period for generating a drive voltage, that is, a switching period of the FETs 281 to 286 and outputting the determined period to the driver 29. The arithmetic unit 30 further has a function of detecting a current waveform from the current of the generator G detected through the shunt 31.
[0024]
When charging the battery 27 with the power generation output of the generator G, the driver 29 stops the drive voltage in order to turn off all of the FETs 281 to 286. As a result, the power generation output of the generator G is rectified by the flyback diodes D <b> 1 to D <b> 6 and supplied to the battery 27. The control circuit 10 has a regulator circuit 32 for setting the voltage of the battery 27 to a predetermined value. The regulator circuit 32 includes a photocoupler 321 and an FET 322. The FET 322 is on / off controlled in response to the on / off of the photocoupler 321, and the power from the generator G supplied to the battery 27 is controlled by the on time of the FET 322. The arithmetic unit 30 has a function of controlling the FET 322 to have a shorter on-time when the battery voltage is higher than a predetermined value, and to control the FET 322 to have a longer on-time when the battery voltage is lower than a predetermined value.
[0025]
FIG. 7 is a waveform diagram after rectification of the generator output showing a method of switching control of the FET 322 for maintaining the battery voltage at a predetermined value. The FET 322 arbitrarily sets a fixed period T in the output of the rectified generator G, and is turned on for a predetermined time t within the period T. By changing the ON operation time t, that is, the ratio of the ON time t in the period T, the power supplied to the battery 27 is adjusted. Note that the on operation time t is not limited to an arbitrary period. For example, the zero cross of the generator output may be detected, and the FET 322 may be turned on for a time t from the zero cross timing.
[0026]
Next, control when the engine E is stopped will be described. If the engine E is stopped and the engine is allowed to stop naturally, the crank angle at the time of stop is indefinite. If the stop crank position is before the compression top dead center, the load may be excessive at the time of starting, and the starting may fail because the moment of inertia cannot be fully utilized. In this embodiment, the engine is controlled so as to stop immediately after the compression top dead center so that the moment of inertia necessary for getting over the top dead center can be obtained.
[0027]
FIG. 8 is a flowchart of engine stop control. In step S1, it is determined whether or not to stop the engine, that is, whether or not the engine operation switch 33 has been switched to the off (stop) position. If this determination is affirmative, the process proceeds to step S2, and all the FETs 281 to 286 are turned off to enter the stop mode. In step S3, the target engine speed of the engine speed is set to a fine speed value. The fine speed value is preferably less than the target rotational speed at the time of cranking, for example. As an example, 300 rpm is preferable. In step S4, the FETs 281 to 286 are switched (switched) to enter the drive mode, that is, the normal operation mode. In step S4, since the target value is operated at a very low speed value, a large load is applied to the engine E that has been rotating at a high speed (for example, 3000 rpm), and so-called regenerative braking is applied. Reduce speed. If the slow speed value is less than the cranking speed, the regenerative braking time is about 100 to 200 milliseconds. In step S5, it is determined whether or not the engine speed has decreased to a target fine speed value.
[0028]
If step S5 becomes affirmative, the routine proceeds to step S6, where it is determined whether or not the crank position is a compression top dead center position. The determination of the compression top dead center position will be described later. If step S6 is affirmative, the process proceeds to step S7 to apply an electric brake to the engine. That is, a brake mode is set in which all the upper FETs 281 to 283 are turned off and all the lower FETs 284 to 286 are turned on among the FETs 281 to 286. As a result, a short circuit brake is applied to the generator G, and the engine E is suddenly stopped. In step S8, it is determined whether or not the engine speed has become lower than a stop speed (stop determination level) set lower than the fine speed value. If step S8 is affirmative, the process proceeds to step S9, where all the FETs 281 to 286 are turned off to enter the stop mode.
[0029]
FIG. 9 is a flowchart of stop control when the engine is stalled. In step S10, it is determined whether an engine stall has occurred. If it is determined that an engine stall has occurred, the process proceeds to step S11, where the target engine speed is set to a very low speed value. In step S12, it is determined whether or not the engine speed is a target fine speed value. If step S12 is affirmative, the routine proceeds to step S13, where it is determined whether or not the crank position is a compression top dead center position. If step S13 is affirmative, the process proceeds to step S14 to apply an electric brake to the engine. In step S15, it is determined whether or not the engine speed has become lower than the stop speed (stop determination level). If step S15 is affirmative, the process proceeds to step S16, and all the FETs 281 to 286 are turned off to enter the stop mode.
[0030]
FIG. 10 is a timing chart relating to the determination of compression top dead center. The vertical axis represents the current flowing through the motor when the generator G is operated as a motor, that is, the fine speed value is set to the target value of the motor rotation speed, The axis is time. The current represents the size of the load. The motor current becomes higher than other regions in accordance with the load increasing at the compression top dead center. Therefore, the electric brake is applied at the peak of the motor current regarded as the compression top dead center. In this example, when the peak of the motor current exceeding the predetermined threshold is detected at timing t0, the timer is started. The timer operates until the next peak detection time (t1) to detect the peak period. When this period is substantially the same for a plurality of times (for example, twice), that is, when the difference is small, it is determined that the peaks correspond to the same timing. That is, it is determined that the peak corresponds to a high load at the compression top dead center. In this example, the periods between timings t0 and t1 are compared with the periods between timings t1 and t2.
[0031]
Then, the electric brake is applied when the next peak is detected (t3). The electric brake is released when the engine speed falls below the stop determination level.
[0032]
If the plurality of cycles substantially coincide with the cycle between the compression top dead centers corresponding to the engine speed, it can be determined whether the current peak corresponds to the compression top dead center or another noise peak. Therefore, this determination may be replaced with the determination based on the difference between the plurality of cycles.
[0033]
FIG. 11 is a timing chart according to a modification of compression top dead center determination. In this modification, the compression top dead center can be suitably detected even when the difference between the motor current peak at the compression top dead center and the motor current peak due to noise is small. In the figure, the motor current is sampled at a predetermined cycle. When the current sampling value SA0 is smaller than the previous sampling value SA-1 and the previous sampling value is larger than the previous sampling value SA-2, it is determined that the sampling value SA1, that is, the current detected at the timing t10 is a peak. Using the sampling value at timing t10 as a temporary compression top dead center, a timer is started for period measurement. Similarly, when a temporary compression top dead center is detected next at timing t11, the timer value at that time is set as the first cycle detection value A. Similarly, when a temporary compression top dead center is detected at the next timing t12, the timer value at that time is set as the second cycle detection value B.
[0034]
Note that whether the sampling value is high or low is determined based on whether or not there is a higher or lower fluctuation in consideration of fluctuations in the motor current at the normal time excluding the compression top dead center.
[0035]
When the periods A and B are substantially the same (A = B ± α), the peak corresponding to the high load at the compression top dead center is determined. In other words, if the compression top dead center is determined, the temporary compression top dead center is estimated as the actual compression top dead center by the third peak detection. If the actual compression top dead center is estimated at the timing t12, the average period of the period A and the period B is calculated, and the timing t13 after the average period from the timing t12, that is, the time when it is regarded as the compression top dead center. Apply the brakes. When the electric brake is applied, there may be a deviation from the actual compression top dead center, but the deviation is slight, and the engine E stops at a position where the crank angle exceeds the compression top dead center.
[0036]
FIG. 1 is a block diagram showing the main functions of the present invention. The engine operation switch 33 is a three-position switch for start, on and off. When the engine operation switch 33 is switched to the off position, the stop instruction determination unit 34 outputs a stop instruction signal in response to this switching. The regenerative braking unit 35 operates the generator G as a motor in response to the stop instruction signal and applies regenerative braking. That is, the target value of the motor control unit 36 that controls the rotation speed of the generator G as a motor to the rotation target value is switched to the fine speed value. The top dead center determination unit 37 detects the compression top dead center based on the current waveform of the generator G. Then, the electric brake unit 38 outputs an electric brake instruction to the motor control unit 36 in response to the compression top dead center detection. The motor control unit 36 applies a short-circuit brake, which is an electric brake, by short-circuiting the winding of the generator G according to an instruction from the electric brake unit 38.
[0037]
In this embodiment, after detecting the compression top dead center, regenerative braking is applied and the engine is suddenly stopped by the short-circuit brake. However, the short-circuit brake may be applied without regenerative braking. Further, the compression top dead center position of the engine may be constantly monitored, and the compression top dead center position of the engine may be detected from this monitoring data in response to the engine stop instruction.
[0038]
Further, the present invention is not limited to the engine-driven generator / starter motor mounted on the lawn mower, and can be widely applied to work machines equipped with the engine-driven generator / starter motor. For example, it is suitable for accurately stopping the engine of a snowplow that drives an auger with a large moment of inertia at a crank position that exceeds the compression top dead center of the engine.
[0039]
【The invention's effect】
As is clear from the above description, according to the inventions of claims 1 to 6, since the sudden braking by the electric brake is applied on the basis of the compression top dead center at the time of stop instruction, the start load immediately after the compression stroke is increased. The engine can be stopped at a small position. Therefore, the start using the moment of inertia can be effectively performed, and the current required for the start can be suppressed. Therefore, the winding is thinned and the power generation winding and the motor winding can be used easily.
[0040]
According to the invention of claim 2, by operating as a constant speed rotation motor, regenerative braking is applied to the inertial rotation, and the engine can be decelerated rapidly. And since the electric brake by a coil short circuit is applied at the time of this low speed rotation, the engine can be stopped with higher accuracy immediately after the compression top dead center.
[0041]
According to the third and fourth aspects of the present invention, the compression top dead center can be detected in a state where the engine rotation is reduced, so that the positional accuracy can be improved. In particular, since no sensor is required, the configuration can be simplified.
[0042]
According to the fifth and sixth aspects of the present invention, even an engine connected with a work implement having a large moment of inertia can be accurately stopped at a position exceeding the compression top dead center.
[Brief description of the drawings]
FIG. 1 is a block diagram showing functions of a main part of a working machine according to an embodiment of the present invention.
FIG. 2 is a perspective view of a lawn mower according to an embodiment of the present invention.
FIG. 3 is a plan view of a main part of a lawn mower according to an embodiment of the present invention.
FIG. 4 is a block diagram showing an overall system of a lawn mower.
FIG. 5 is an exploded front view showing an example of a generator.
FIG. 6 is a circuit diagram showing an example of a control circuit.
FIG. 7 is an explanatory diagram of an FET control method.
FIG. 8 is a flowchart of engine stop control.
FIG. 9 is a flowchart of engine stop control when the engine is stalled.
FIG. 10 is a timing chart of determination of compression top dead center.
FIG. 11 is a timing chart according to a modified example of compression top dead center determination.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Cutter housing, 2 ... Turf discharge port, 3 ... Cutter chamber, 4 ... Blade cutter, 5 ... Crankshaft, 7 ... Motor, 8 ... Reduction gear mechanism, 10 ... Drive circuit, 27 ... Battery, 29 ... Driver, 30 Reference numeral 31: Shunt, 32: Regulator circuit, 33: Engine operation switch, 34: Stop instruction determination unit, E: Engine, G: Generator

Claims (3)

In the engine-driven work machine in which the output shaft of the engine that drives the load is connected to the rotating shaft of the generator / motor,
Instruction means for instructing to stop the engine;
A compression top dead center detecting means for detecting a compression top dead center of the engine in response to an engine stop instruction by the instruction means;
Means for operating the generator combined motor in response to the engine stop instruction as a motor in accordance with a low speed rotation target value that is lower than the cranking rotation speed of the engine;
Electric brake means for short-circuiting the winding of the generator combined motor when the compression top dead center is detected by the compression top dead center detection means during low speed rotation according to the slow speed target value ;
Current waveform detection means for detecting the current waveform of the generator combined motor,
The compression top dead center detecting means is
Means for determining a current peak based on a current waveform during the low-speed rotation as a temporary compression top dead center;
A plurality of temporary compression top dead centers, and a means for estimating a next compression top dead center based on an interval between the plurality of temporary compression top dead centers;
An engine-driven work machine , wherein the electric brake is configured to start energizing at the estimated compression top dead center . 2. The engine-driven work machine according to claim 1 , wherein the engine is operated at a substantially constant speed, and a blade cutter for lawn mowing is connected to the output shaft of the engine as a work tool . The engine-driven work machine according to claim 1 , wherein the engine is operated at a substantially constant speed, and a snow removing auger is connected to the output shaft of the engine as a work tool .

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