JP2018061477A - Multi-blade grass mower - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multi-blade grass mower that satisfies a demand for reducing noise since it may be used in a residential area.SOLUTION: A multi-blade includes: a plurality of blades rotatably supported to a mower deck downward of the mower deck that is supported to a travelling machine body; and a power feed section 30 for feeding rotation power to a blade. At least one of the blades rotates at a rotation speed different from a rotation speed of the other blades.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a multi-blade mower having a plurality of blades rotatably provided on a mower deck supported by a traveling machine body.

  Patent Document 1 discloses a lawnmower in which a mower deck is provided on a machine frame including an engine and wheels so as to be movable up and down via a link mechanism. On the mower deck, two rotating shafts fixed with blades are rotatably supported. Rotational power from the engine is transmitted to two rotating shafts via a belt transmission mechanism. One blade is rotated clockwise and the other blade is rotated counterclockwise. The rotational speed (rotational speed) of both blades is the same.

  Patent Document 2 discloses a riding electric lawn mower. The body of this riding electric lawn mower is supported by drive wheels driven by a traveling electric motor, and a mower unit is suspended from this body. The mower unit includes three blades and three blade motors that individually drive the blades. The three blade motors are driven by constant speed control (ON / OFF control) so that each blade rotates at a constant rotational speed. As another embodiment, it has been proposed to exceptionally increase the rotational speeds of the three blade motors as the traveling speed decreases. Although increasing the rotational speed of the three blade motors is disclosed, it is not disclosed that the rotational speed difference of the three blades is different.

  Since multi-blade mowers are sometimes used in residential areas, there is a demand for noise reduction.

JP 2014-143984 A JP 2012-187026 A

  The subject of this invention is provision of the technique which suppresses the expansion of blade noise by each noise which arises from a some braid | blade with rotation in a multiblade mower.

A multi-blade mower according to the present invention provides a traveling machine body, a mower deck supported by the traveling machine body, a plurality of blades rotatably supported by the mower deck below the mower deck, and rotational power to the blades. A power supply unit,
The rotational speed of at least one of the plurality of blades is different from the rotational speed of the other blades.

  In the multi-blade mower, the noise generated with the rotation of the blade includes many frequency components, and the frequency component (hereinafter referred to as the peak frequency) showing a particularly strong sound pressure is the nth order of the blade rotation frequency. It is known that it is a component (n is a natural number of 1 or more). When a plurality of blades are rotated at the same rotation speed, the peak frequencies of noise generated by the respective blades overlap, and the sound pressure at this peak frequency is doubled. Such peak frequency is related to the rotational speed of the blade. According to the present invention, by making the rotation speed of at least one of the plurality of blades different from the rotation speed of the other blades, it is possible to avoid the overlap of peak frequencies and to obtain a noise reduction effect. Based on knowledge. If the peak frequency of the noise of one blade and the peak frequency of the noise of the other blade are shifted by half of the period, the other peak frequency is sandwiched between the one peak frequency, so the overlap of the peak frequencies is minimal It becomes. However, since the blade rotation speed is also related to the mowing performance, in practice, it is preferable to shift the rotation speed by about 1/10 to 1/3 of the cycle.

  Most of the traveling type multi-blade mowers are a two-blade mower having two blades arranged in a direction transverse to the traveling direction and a three-blade mower having three blades arranged. Even in a multi-blade mower having three or more blades, in order to obtain a more effective noise reduction effect, it is preferable that the rotation speeds of all the blades are different from each other. However, even if the rotational speed of at least one blade is different from the rotational speed of the other blades, it is possible to obtain a noise reduction effect.

  Further, in the mower, a standard rotational speed appropriate for mowing is calculated based on the specifications of the blade and the traveling speed. Therefore, even when the rotation speeds of the blades are made different from each other, it is not preferable to leave the rotation speed as far as possible. From this, in one of the preferred embodiments of the present invention, the rotational speed difference between the plurality of blades increases the rotational speed of one blade with respect to the standard rotational speed suitable for mowing and the other blade. Produced by lowering the number of revolutions.

  In one of the specific configurations for making the rotational speed of at least one blade different from the rotational speed of other blades, the power supply unit separately supplies a common drive source and rotational power from the drive source. And a separate power transmission unit that supplies the blades with a speed change. In this configuration, when the engine or the like is used as a drive source, the speed is changed by a gear transmission mechanism or the like after or after the rotational power from the engine is branched to each blade. This configuration is advantageous when the present invention is applied to a conventional engine-mounted multi-blade mower.

  In another one of the specific configurations for making the rotation speed of at least one blade different from the rotation speed of the other blade, the power supply unit includes a plurality of electric motors assigned to the blades. . In this configuration, since the rotation speed of each blade can be controlled independently, the blade rotation speed difference for obtaining the noise reduction effect can be easily optimized. At that time, power supply to the drive wheels may be performed by an engine or an electric motor.

  The blade rotation speed difference for obtaining the noise reduction effect may vary depending on the structure of the mower deck and the structure of the mower. For this reason, in order to obtain an appropriate noise reduction effect, it is preferable that the rotation speed of each blade can be arbitrarily adjusted within a range of the rotation speed that does not substantially affect the mowing performance. Therefore, in one preferred embodiment of the present invention, the blade motor control unit that controls the electric motor has a rotational speed difference that provides low noise within a predetermined rotational speed range of the blade in mowing work. It is comprised so that the rotation speed of the said electric motor may be controlled.

It is a side view of a 2-blade mower. It is a top view of a 2 blade mower. It is a systematic diagram which shows the electric system and power system of a 2-blade mower. It is a functional block diagram of the control system of a 2-blade mower. It is a graph which shows the frequency analysis result of a blade noise. It is a systematic diagram which shows the electric system and power system of a 3-blade mower.

  Next, one specific embodiment of the multi-blade mower according to the present invention will be described with reference to the drawings. FIG. 1 is a side view of a two-blade mower as an example of a multi-blade mower, and FIG. 2 is a plan view. This mower has a front wheel unit 1 composed of a freely castable left front wheel 1a and a right front wheel 1b, a drive wheel unit 2 composed of a left rear wheel 2a and a right rear wheel 2b, and a front wheel unit 1 and a drive. A traveling machine body 10 supported by the wheel unit 2 is provided. Further, a battery 20 is disposed at the rear of the traveling machine body 10, and a driver seat 11 is disposed at an intermediate portion of the traveling machine body 10, and a fall protection frame 12 is erected from the rear of the driver seat 11. In the lower space of the traveling machine body 10 between the front wheel unit 1 and the drive wheel unit 2, the mower unit 3 suspended from the traveling machine body 10 is arranged so as to be movable up and down via a lifting link mechanism as the lifting mechanism 13. ing.

  In front of the driver's seat 11, a floor plate is provided as a footrest for the driver, and a brake pedal 14 protrudes therefrom. On both sides of the driver's seat 11, a steering unit 15 including a left steering lever 15 a and a right steering lever 15 b that swings around a horizontal swing axis in the transverse direction of the aircraft is disposed. Further, a blade operation lever (which may be a switch type) 16 is disposed around the driver seat 11.

  This mower is an electric mower in which the drive wheel unit 2 and the mower unit 3 are driven by electric power. FIG. 3 is a system diagram showing an electrical system and a power system of the 2-blade mower. FIG. 4 is a functional block diagram of the control system of the 2-blade mower. The left motor 21 and the right motor 22 which are these tutors are equipped. The rotation speeds of the left motor 21 and the right motor 22 are changed depending on the amount of electric power supplied via the inverter 4 independently. Therefore, the rotational speeds of the left rear wheel 2a and the right rear wheel 2b can be made different, and the direction of the mower is changed by the difference between the left and right rear wheel speeds. In FIG. 3, the left motor 21 and the right motor 22 are depicted as in-wheel motors for the sake of simplicity, but they need not be in-wheel motors. In this embodiment, as is clear from FIG. 1, the left motor 21 and the right motor 22 are disposed on the center side of the traveling machine body 10, and between the left motor 21 and the left rear wheel 2 a and between the right motor 22 and the right rear wheel. A traveling drive mechanism is provided for transmitting power to and from 2b.

  In this embodiment, the mower unit 3 is a two-blade side discharge type as shown in FIGS. 2 and 3, and includes a mower deck 3a, plate-like first blades 31a, and second blades 32a. Yes. The mower deck 3a includes a ceiling surface and a vertical wall extending downward from the front edge of the ceiling surface. Cutting blade tips are formed at both ends of the first blade 31a and the second blade 32a, and a wind-up blade is formed behind each cutting blade tip.

  The first blade 31a is fixed to the lower end portion of the first rotation shaft 31b that vertically penetrates the ceiling surface of the mower deck 3a, and the first blade 31a is the second rotation that vertically penetrates the mower deck 3a. It is fixed to the lower end of the shaft 32b. The first rotating shaft 31b and the second rotating shaft 32b are rotatably supported by the mower deck 3a via boss bearings. The upper end of the first rotating shaft 31b is connected to the output shaft of the first blade motor 31 that is an electric motor, and the upper end of the second rotating shaft 32b is connected to the output shaft of the second blade motor 32 that is an electric motor. Has been. In other words, in this embodiment, the power supply unit 30 that supplies rotational power to the first blade 31a and the second blade 32a includes the first rotational shaft 31b, the first blade motor 31, and the second rotational shaft 32b, respectively. A two-blade motor 32 is used. Of course, a belt transmission mechanism or the like may be interposed in the power transmission between the first rotating shaft 31b and the first blade motor 31 and between the second rotating shaft 32b and the second blade motor 32.

  At the time of mowing work, the cut grass by running the mower while rotating the first blade 31a and the second blade 32a, the wind generated by the wind blades of the first blade 31a and the second blade 32a, Guided by the baffle plate, the interior of the mower deck 3a is transported to the lateral one end side where the discharge port is located, and discharged from the discharge port to the lateral outer side of the mower deck 3a.

  Blade noise is generated by rotating the first blade 31a and the second blade 32a. The noise of the two blades is doubled compared to the blade noise of each blade when the blade rotation speed is the same. This is thought to be because the peak frequencies of the blade noise overlap. FIG. 5 shows the experimental results of blade noise. FIG. 5 shows the result of frequency analysis of blade noise. A thin solid line indicates blade noise for one blade, and a thick solid line indicates blade noise for two blades at the same rotational speed. A dotted line is a blade stop state and indicates background noise. The blade noise shows a peak value (peak frequency) at the nth order of the blade rotation speed (n is a natural number of 1 or more), but the peak frequency overlaps with 2 blades at the same rotation speed. Compared with the noise sound pressure is doubled. By paying attention to this, in the present invention, a difference is provided in the blade rotation speed in the multi-blade to avoid the overlap of the peak frequencies. Although it is preferable that the peak frequency of one blade noise is in the middle of the peak frequency of the other blade noise, the noise reduction effect can be obtained even if it is not exactly in the middle. Since there is an optimum rotational speed region in order to maintain satisfactory mowing performance, the set rotational speed difference should be balanced between the noise reduction effect and the mowing performance. For example, the effect of noise reduction can be obtained by shifting the peak frequencies of each other by about 1/10 to 1/3 of the period.

  As shown in FIGS. 3 and 4, power is supplied to the left and right motors 21 and 22 for driving and the first blade motor 31 and the second blade motor 32 as drive sources for supplying rotational power to the blades. This is performed by inverter control by the controller 5 which is also called. For this reason, the inverter 4 connected to the battery 20 supplies power to the blade motor power supply unit 40 that supplies power to the first blade motor 31 and the second blade motor 32, left wheel power supply unit 41 that supplies power to the left motor 21, and right motor 22. A right wheel power feeding unit 42 is provided.

  As shown in FIG. 4, the controller 5 is connected to the traveling state detection sensor group 7, the steering state detection sensor group 8, and the blade state detection sensor group 9. The traveling state detection sensor group 7 includes a left rear wheel rotation detection sensor 70a (see FIG. 3) for detecting the rotation speed of the left rear wheel 2a, and a rotation speed of the right rear wheel 2b as a right rear wheel rotation detection sensor 70b (FIG. 3). Sensor) for detecting information related to travel, for example. The steering state detection sensor group 8 includes a left steering angle detection sensor 80a that detects a swing angle of the left control lever 15a, a right steering angle detection sensor 80b that detects a swing angle of the right control lever 15b, and the like. . The blade state detection sensor group 9 also includes rotation speed sensors 91 a and 91 b that detect the blade rotation speed, and sensors (not shown) that detect the operation state of the blade operation lever 16. The rotation speed sensors 91a and 91b for detecting the blade rotation speed are used for setting the blade rotation speed, but may be omitted.

  The controller 5 includes functional units such as an input signal processing unit 51, a left wheel speed calculation unit 52, a right wheel speed calculation unit 53, a travel control unit 54, a blade rotation number setting unit 55, and a blade motor control unit 56. These functional units are constructed by hardware or software. The input signal processing unit 51 includes a sensor information processing function and an operation input processing function. The input signal processing unit 51 processes signals from the outside such as the traveling state detection sensor group 7, the steering state detection sensor group 8, and the blade state detection sensor group 9, and converts them into information that can be used inside the controller 5. .

  The left wheel speed calculation unit 52 is based on the operation information through the left steering angle detection sensor 80a that detects the operation amount of the left steering lever 15a by the driver, that is, the rotation speed (number of rotations) of the left rear wheel 2a, that is, the left motor 21. Obtain the rotation speed (number of rotations). The right wheel speed calculation unit 53 also uses the right steering angle detection sensor 80b for detecting the amount of operation of the right steering lever 15b by the driver, based on the operation information through the right steering angle detection sensor 80b, that is, the right motor 22. The rotation speed (number of rotations) of is calculated.

  The travel control unit 54 supplies the electric power necessary for realizing the rotation speed of the left motor 21 and the rotation speed of the right motor 22 obtained by the left wheel speed calculation unit 52 and the right wheel speed calculation unit 53 to the left motor 21 and the right motor. 22, a control signal for sending is supplied to the left wheel feeding unit 41 and the right wheel feeding unit 42.

  The blade rotation speed setting unit 55 sets a first rotation speed that is the rotation speed (rotation speed) of the first blade motor 31 and a second rotation speed that is the rotation speed (rotation speed) of the second blade motor 32, and This is given to the blade motor control unit 56. The first rotational speed is larger (or smaller) by a predetermined value than the standard rotational speed suitable for mowing, and the second rotational speed is smaller (or larger) by a predetermined value than the standard rotational speed. As described above, the predetermined value is a value set so that the peak frequencies of the blade noise do not overlap, and can be adjusted. The blade motor control unit 56 gives a control signal to the blade motor power supply unit 40 so that the first blade motor 31 is driven at the first rotational speed and the second blade motor 32 is driven at the second rotational speed. For easy understanding, the blade rotation number setting unit 55 and the blade motor control unit 56 are separate function units here, but the blade rotation number setting unit 55 is a function incorporated in the blade motor control unit 56. You may comprise as.

  When a signal from a noise sensor for detecting blade noise is input to the input signal processing unit 51, control for adjusting the rotational speed difference between the first blade motor 31 and the second blade motor 32 so as to obtain as low noise as possible. Functions may be built in the blade rotation number setting unit 55 and the blade motor control unit 56. At that time, it is preferable that the set rotational speed difference is limited so as to be a rotational speed difference within a rotational speed range in which a predetermined mowing performance is obtained.

[Another embodiment]
(1) In the above-described embodiment, an electric mower has been handled, but an engine may be used as a common drive source for the traveling system and the mower drive system. In this case, in FIG. 3, an engine is used instead of the battery 20 and the inverter 4, and a power transmission unit (gear type, pulley) having a transmission unit is used instead of the left motor 21, the right motor 22, and the blade motors 31 and 32. Formula). That is, in the engine-type mower, the power supply unit 30 includes an engine and a power transmission unit that transmits power from the engine to the blade rotation shaft (the first rotation shaft 31b and the second rotation shaft 32b).
(2) In the above-described embodiment, a two-blade mower is handled, but a multi-blade mower equipped with three blades or more blades may be used. For example, FIG. 6 shows a system diagram showing an electrical system and a power system of a 3-blade mower. Compared to the two-blade mower shown in FIG. 3, a third blade motor 33, a third blade 33a, and a third rotating shaft 33b are added. In the 3-blade mower, the rotation speed of the three blades may be controlled to be different so that the peak frequency of each blade noise is shifted from each other, or at least one blade may be controlled to be different from the other blades. Good.
(3) In the above-described embodiment, the multi-blade mower is a mid-mount type in which the mower unit 3 is disposed between the front wheel and the rear wheel, but the front mower type in which the mower unit 3 is disposed in front of the front wheel. It may be.
(4) In the above-described embodiment, the left rear wheel 2a and the right rear wheel 2b of the drive wheel unit 2 are so-called zero-turn type vehicles that can be driven independently, but the left rear wheel 2a and the right rear wheel 2b. May be connected to each other by a differential mechanism.

  The present invention is applied to a multi-blade mower having a plurality of blades.

3: Moor unit 4: Inverter 5: Controller 7: Traveling state detection sensor group 8: Steering state detection sensor group 9: Blade state detection sensor group 10: Traveling machine body 15: Steering unit 15a: Left steering lever 15b: Right steering lever 20 : Battery 21: Left motor 22: Right motor 30: Power supply unit 31: First blade motor 31a: First blade 32: Second blade motor 32a: Second blade 40: Blade motor power supply unit 51: Input signal processing unit 52 : Left wheel speed calculation unit 53: right wheel speed calculation unit 54: travel control unit 55: blade rotation speed setting unit 56: blade motor control unit 91a: rotation speed sensor 91b: rotation speed sensor

Claims (6)

Traveling aircraft,
A moor deck supported by the traveling body;
A plurality of blades rotatably supported by the mower deck below the mower deck;
A power supply unit for supplying rotational power to the blade;
In a multi-blade mower with
A multi-blade mower in which the rotational speed of at least one of the plurality of blades is different from the rotational speed of the other blades.   The multi-blade mower according to claim 1, wherein all the rotation speeds of the plurality of blades are different.   The rotational speed difference between the plurality of blades is created by increasing the rotational speed of one blade relative to a standard rotational speed suitable for mowing and decreasing the rotational speed of the other blade. The described multi-blade mower.   The said power supply part consists of a common drive source and the separate motive power transmission part which changes separately the rotational motive power from the said drive source, and supplies it to each said braid | blade. Multi-blade mower.   The multi-blade mower according to any one of claims 1 to 3, wherein the power supply unit includes a plurality of electric motors assigned to the blades.   The blade motor control unit that controls the electric motor controls the rotational speed of the electric motor so as to obtain a rotational speed difference that provides low noise within a predetermined rotational speed range of the blade in mowing work. The described multi-blade mower.

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