JP2010017118A - Lawn mower - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lawn mower which can switch the speed of rotations into a low speed without lowering the power of a motor, when it is desired to reduce noises, and can change a set speed of rotations without relating to frequency. <P>SOLUTION: Provided is the lawn mower which has a handle extended in the oblique rear direction of a body and mows lawns with a rotary blade interlocked with the rotation of an electric motor in a state that the handle is held, characterized in that the motor is driven with a circuit comprising an AC power source, a triac and a resistor for detecting an electric current so that a rotation controller connected between the switch and the motor in parallel can control the speed of rotations to a high speed or a low speed by switching the shift switch for changing rotary speed on the body, and a rotation control IC for controlling the rotation of the motor can control the conducting angle of the triac on the basis of an electric current value detected with the electric current-detecting resistor for detecting the electric current of the motor and a set value set with a rotation setting circuit. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to control of the number of rotations of a motor of a lawn mower that cuts grass.

A conventional lawn mower has a handle pivotally supported in the upper rear of the main body so as to be rotatable in the front-rear direction. The turf is cut by rotating blades that are linked to the rotation of the blades or by sliding the rotating blades and fixed blades.
However, when using a lawn mower, the rotating speed is constant and the rotating blade and fan noise, and the sliding noise between the rotating blade and fixed blade are loud. It was necessary to carry out the pruning work with care.
In order to solve such a problem, there is a rotation speed control by a diode as described in Patent Document 1. Thereby, the operator can change the rotation speed to a low speed by switching the rotation speed change switch.

Akisho 50-64071

However, while the rotational speed control configured as described above can reduce the rotational speed and suppress noise, it is a half-wave rectification by a diode, so the rotational speed is reduced and the motor power is also reduced. It was. For this reason, when applied to a lawn mower, there is a problem that the lawn mowing work is restricted during low-speed rotation.
In addition, since the set rotational speed varies depending on the frequency, it is necessary to prepare specifications for 50 Hz and 60 Hz in order to control to the same rotational speed.

  An object of the present invention is to provide a lawn mower capable of switching the rotation speed to a low speed without lowering the motor power when it is desired to suppress noise and changing the rotation speed to a set rotation speed regardless of the frequency. It is.

  Of the inventions disclosed in the present application, typical features will be described as follows.

According to one aspect of the present invention, the present invention includes a switch for changing the number of rotations of the motor, and a semiconductor element for controlling a voltage applied to the motor between the motor and the switch and a current flowing in the motor are detected. A rotation speed control device provided with a current detection means for outputting a current detection signal and a phase control means for controlling the conduction angle of the semiconductor element based on the output signal, the phase control means depending on the frequency of the input power supply. This is achieved by making it possible to control.

  According to the first aspect of the present invention, the switch for changing the rotational speed of the motor is provided, the semiconductor element for controlling the voltage applied to the motor between the motor and the switch, the current flowing through the motor is detected, and the current detection signal A rotation speed control device is provided that includes a current detection means that outputs current and a phase control means that controls the conduction angle of the semiconductor element based on the output signal. The phase control means controls the conduction angle according to the frequency of the input power supply. By doing so, the rotational speed can be switched to a low speed without reducing the power of the motor. For this reason, when you want to mow the grass in the early morning or in a densely populated area, you can change the motor speed to a lower speed by switching the motor speed to a lower speed. When you want to perform lawn mowing work powerfully, such as in a place, the speed can be increased by switching the motor speed change switch at high speed. Selection becomes possible.

  According to the invention of claim 2 and claim 3, the phase control means controls the conduction angle of the semiconductor element according to the frequency of the input power supply, so that the number of rotations when different power supply frequencies typified by 50 Hz and 60 Hz are used. Can be prevented.

According to the invention of claim 4, since the rotation speed control device is provided with the function of cutting off the current when the current detection signal output from the current detection means is greater than or equal to the set value, it is inexpensive and does not require a normally used breaker. Can provide a lawn mower.

  An embodiment of the lawn mower according to the present invention will be described with reference to FIGS.

  FIG. 1 is a partial sectional side view of a main body according to an embodiment of the present invention, FIG. 2 is a working state diagram of a lawn mower according to an embodiment of the present invention, and FIG. 3 is a configuration of a rotation speed control device according to the embodiment of the present invention. FIG.

  1 and 2, the lawn mower 1 has a handle 4 pivotally supported by a handle bar 3 so as to be rotatable with respect to the front-rear direction obliquely rearward and upward of the main body 2, and the safety lock switch 5 shown in FIG. By turning on the main switch 6 while pressing, the power outlet and the power cord 7 are connected via the extension cord 8, and the electric power is supplied to the motor 9 built in the main body 2, so that the rotation directly connected to the motor 9 shaft The blade 10 rotates, and the turf can be trimmed by running the main body 2 along the ground so as to hold the handle 4 and push it forward. Further, the cut grass is collected in the grass collection bag 13 through the discharge port 12 at the rear of the main body 2 by the wind force of the fan 11 interposed between the motor 9 and the rotary blade 10.

  Further, by operating the changeover switch 14 for changing the rotation speed at the top of the main body 2, the rotation speed control device 15 connected in parallel between the switch 14 and the motor 9 controls the rotation speed between the high speed mode and the low speed mode. It is configured to be able to.

  In FIG. 3, a rotation speed control device 15 is a device for controlling the rotation speed of the motor 9, and includes a changeover switch 14, a triac 17, a current detection resistor 18, a rotation speed setting circuit 19, and a rotation speed control IC 20. Consists of The motor 9 is driven by a circuit comprising an AC power supply 16, a triac 17 and a current detection resistor 18, and the rotation speed control device 15 rotates the current value detected by the current detection resistor 18 for detecting the current of the motor 9 and the rotation. Based on the set value set by the number setting circuit 19, the rotation speed control IC 20 that controls the rotation of the motor 9 is configured to control the rotation angle of the motor 9 by controlling the conduction angle of the triac 17. Yes.

  The rotation speed control IC 20 compares the current value detected by the current detection resistor 18 with the setting value set by the rotation speed setting circuit 19, and if the current value is high, the conduction angle of the triac 17 is increased and the current value is increased. Is low, the rotation angle of the motor 9 with respect to the increase or decrease of the load is suppressed by reducing the conduction angle of the triac 17. According to such a configuration, even when the changeover switch 14 is set to the low speed mode, the airflow is not insufficient due to the decrease in the rotational speed at the no-load rotational speed, and the grass collection rate is not decreased. You can keep the lawn mowing work. Further, since the problem of noise due to an increase in the rotational speed is less likely to occur from a region where the load applied to the motor 9 is large, the low-speed mode control is performed at a rotational speed-torque curve characteristic similar to that of the high-speed mode control. The lack of power in the mode is prevented.

  Further, the rotation speed control IC 20 compares the current value detected by the current detection resistor 18 with the overcurrent setting circuit 21 and the set value set by the overcurrent setting circuit 21. If the current value is high, the triac 17 An overcurrent protection function for interrupting the continuity of the motor 9 and stopping the number of rotations of the motor 9 is added, and a circuit can be configured without separately providing an overcurrent protection device such as a bouker. According to this, since the rotation speed control IC 20 used for the rotation speed control can be used for overcurrent protection, it is possible to provide an inexpensive lawn mower with a mode switching mechanism.

Further, a frequency conversion circuit 22 is provided between the input AC power supply 16 and the rotational speed setting circuit 19 so that the set value set by the rotational speed setting circuit 19 can be corrected. It is possible to prevent the rotation speed from fluctuating with respect to the set value set by the rotation speed setting circuit 19 with the frequency of 16. According to this, it is possible to provide a lawn mower with stable performance that is not affected by an input power frequency such as 50 Hz or 60 Hz.

It is a partial section side view of the main part concerning the embodiment of the present invention. It is a work state figure of the lawn mower which concerns on embodiment of this invention. It is a block diagram of the rotation speed control apparatus which concerns on embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Lawn mower 2 Main body 3 Handlebar 4 Handle 5 Safety lock switch 6 Main switch 7 Power cord 8 Extension cord 9 Motor 10 Rotary blade 11 Fan 12 Discharge port 13 Grass collection bag 14 Changeover switch 15 Rotational speed control device 16 AC power source 17 Triac 18 Current detection resistor 19 Rotation speed setting circuit 20 Rotation speed control IC 21 Overcurrent setting circuit 22 Frequency conversion circuit 23 Circuit power supply

Claims (4)

A main body having a discharge part to which a bag for collecting grass can be connected, a motor accommodated in the main body, and a rotary blade that rotates in conjunction with the rotation of the motor, and is cut by the rotary blade. In a lawn mower that collects grass in the bag for collecting grass,
A switch for changing the number of rotations of the motor, a semiconductor element for controlling a voltage applied to the motor between the motor and the switch, and a current for detecting a current flowing through the motor and outputting a current detection signal A lawnmower comprising: a rotation speed control device including detection means and phase control means for controlling a conduction angle of the semiconductor element based on an output signal.
2. The lawn mower according to claim 1, wherein the phase control unit controls a conduction angle of the semiconductor element according to a frequency of an input power source.
The frequency conversion circuit for correcting the setting value set by the rotation speed setting circuit is provided between the AC power supply and the rotation speed setting circuit for setting the rotation speed. Lawn mower.
  The rotation speed control device is provided with a function of cutting off current when a current detection signal output from the current detection means is equal to or greater than a set value. A lawn mower according to claim 1.

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