ELECTRIC MOWER WITH AUTOMATIC BLADE UNBLOCKING AND METHOD FOR CONTROLLING THE MOWER

Abstract

An electric mower has an electric motor driving at least one rotary cutting blade. A method for controlling the mower includes: a rest phase during which the electric motor is not powered; a mowing phase during which the electric motor is controlled to rotate in a first direction of rotation, corresponding to the rotation of the cutting blade in a plant cutting direction; and a temporary blade start phase, in which the electric motor is temporarily controlled to rotate in a second direction opposite the first direction of rotation. The mower and method are applicable to mowers and brushcutter mowers.

Claims

1. Electric mower comprising: at least one rotary cutting blade; a rotary electric motor for driving the cutting blade; an electronic control unit of the electric motor configured to control a rotation of the electric motor in a first direction of rotation during a mowing phase, and for controlling a rotation of said electric motor in a second direction of rotation opposite to the first direction of rotation, during a blade startup phase, characterized in that: the electric motor is of the brushless type; and the control unit is equipped with a measuring circuit of an induction current in at least one winding of the electric motor and configured to initiate the blade start-up phase in response to an absence of induction current in the winding of the electric motor.

2. Mower according to claim 1 in which the control unit is also configured to initiate the blade startup phase automatically during each start of the electric motor.

3. Mower according to claim 1, in which the control unit is configured to detect a blockage situation of the blade during the blade startup phase and to cause a dislodging operation comprising the control of a sequence of rotations of the electric motor alternately in the first and in the second direction of rotation.

4. Mower according to claim 1, including an electric adjustment mechanism of a cutting height configured for a transitory lifting of a cutting height of the mower during a blade startup phase.

5. Mower according to claim 1, including a control interface connected to the motor control unit, the control interface including a trigger element of the blade startup phase.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0077] FIG. 1 is a perspective view of a walk-behind mower according to the invention.

[0078] FIG. 2 is a partial view of the mower of FIG. 1 passing through the drive shafts of cutting blades.

[0079] FIG. 3 is a flow chart illustrating the main aspects of a method for controlling the mower.

DETAILED DESCRIPTION OF MODES OF IMPLEMENTATION OF THE INVENTION

[0080] Identical or similar portions of the different figures are marked with the same reference signs so that it is possible to refer from one figure to the other.

[0081] The mower of FIG. 1 is a mower 10 of the walk-behind type. It comprises a cutting unit 20 mounted on a frame 14. The cutting unit is connected to the frame by a parallelogram suspension not visible on FIG. 1. It presents freedom of vertical travel relative to the frame 14 so as to be able to move it closer to or further away from the ground and thereby modify the cutting height. The vertical travel of the cutting unit is performed by an electric jack mechanism 16.

[0082] An interface 18 located at the end of a handlebar includes various controls and possibly a visual display unit. It enables the operator to operate the mower by regulating, as needed, its operating parameters.

[0083] As shown even better on FIG. 2, the cutting unit 20 includes a cutter casing 22 housing two cutting blades 24a, 24b and presenting an elimination channel 25 of the mowed grass clippings towards a collection bin 26 visible on FIG. 1. The cutting unit 20 includes also a blade drive motor 30. It is an electric motor, and in the example shown, it is a brushless motor.

[0084] The blade drive motor 30 includes a motor shaft 32a at the end of which is mounted one of the cutting blades 24a. A transmission system 34 with toothed wheels joins together in rotation the motor shaft 32a and a second shaft 32b on which the second cutting blade 24b is mounted. The set of toothed wheels of the transmission system may be replaced by a belt drive. Thus, the two cutting blades 24a and 24b are integral in rotation with each other and in rotation with the drive motor 30.

[0085] The cutting unit 20 finally includes a control unit 40 of the electric motor. The control unit includes a first electronic card 42 dedicated to the management of the electric power supply to the motor from a battery 44 visible on FIG. 1. The first electronic card 42 is capable of controlling voltages and a sequence of voltages applied to the different windings of the stator of the motor 30 to set the rotation of the motor, the direction of rotation of the motor and the rotation speed of the motor.

[0086] The control unit 40 also includes a second electronic card 47 intended for the determination of an induction current by the rotor in one or more windings of the stator of the motor 30. The second electronic card includes one or more current measuring circuits connected to one or more stator windings. It also receives control data of the motor from the first electronic card 42. Based on the measured currents and based on the induction current derived from it, the second electronic card 47 is able in particular to estimate the position of the rotor in rotation and its movement. This is equivalent to measuring the rotation or absence of rotation of the blades integral in rotation with the motor 30.

[0087] The second electronic card 47 and the current measuring circuits may also be used to determine a global supply current of the motor and derive a blockage situation of the motor from an abnormal increase of this current.

[0088] Other electronic cards 48 of the control unit 40 are provided for accessory functions of the control unit such as the control of electric motors propelling the mower forward, the control of the electric jack 16 mentioned previously or also of the interface 18.

[0089] The flowchart of FIG. 3 illustrates the operation of the mower and in particular the control of the electric blade drive motor 30.

[0090] The reference 100 of FIG. 3 corresponds to a rest phase of the electric motor 30 in which it is not supplied with power. The motor and the blades do not turn. The rest phase 100 is used for example while the mower is in storage, when it is not in use or during a human intervention on the cutting blades for example.

[0091] A startup of the motor can be caused, for example, by an action of the operator on a push button or a key switch of the interface 18 shown on FIG. 1. The startup of the electric motor marks the passage from the rest phase 100 to a mowing phase 102 during which the electric blade drive motor is supplied with power for a rotation in a first direction of rotation. The first direction of rotation corresponds also to a direction of rotation of the blades that is suitable for mowing. In the mowing phase, the mower is usable for mowing plants, and if applicable, for collecting the mowed plant material in the collection bin 26.

[0092] In the example shown, the passage from the rest phase 100 to the mowing phase 102 at the moment of startup may take place in three ways.

[0093] According to a first possibility, indicated by an arrow 104, the passage from the rest phase to the mowing phase may be immediate. The cutting blades are then activated in rotation in the plant cutting direction.

[0094] According to a second possibility indicated by an arrow 106, the passage from the rest phase to the mowing phase may take place through the intermediary of a blade startup phase 108.

[0095] As mentioned previously, the startup phase 108 is a transitory phase of short duration during which the electric blade drive motor is powered for a rotation in the second direction of rotation, opposite to the first direction of rotation. The blade startup phase may be accompanied by the command of a lifting 150 of the cutting unit thereby limiting, if necessary, the cut resistance at the cutting blades.

[0096] According to a third possibility indicated by an arrow 110, the passage through the startup phase 108 may be conditional on a step 112 of verification of no blade blockage. The verification takes places, for example, by powering the electric motor for a rotation in the first direction of rotation, and by verifying whether the rotation sensor 46 (FIG. 2) emits a rotation signal. When there is no blockage, the verification step 112 is immediately followed by the mowing phase 102 as indicated by an arrow 114. In the opposite case, the verification step may be followed by the blade startup phase 108, as indicated by the arrow 116.

[0097] At the end of the blade startup phase 108 the electric motor may pass directly to the mowing phase 102 as an arrow 118 indicates. The startup phase may also include, or be followed by a step 122 of verification of no blockage as indicated by the arrow 120. This step is comparable to the step 112 of verification of no blockage mentioned previously.

[0098] As an arrow 124 shows, the verification step 122 of no blockage of the blade startup phase 108 is followed by the mowing phase in the absence of a blockage.

[0099] In the opposite case, that is to say when there is a blockage, the blade startup phase 108 is followed, as indicated by an arrow 126, by a dislodging phase 128. The dislodging operation 128 includes, as mentioned previously, a rapid sequence of powering the electric motor in the first and in the second direction of rotation. The dislodging operation amounts, in some way, to repeating several times a blade startup operation in opposite directions of rotation.

[0100] A new step 132 of verification of no blade blockage, indicated by the arrow 130, is provided at the end of the dislodging step.

[0101] When the verification step 132 is able to observe-an unblocking, that is to say a rotation of the motor, and thus by the blades, it is followed, as the arrow 134 shows, by the mowing phase 102.

[0102] Inversely, a failure to unblock noted in the verification step 132, after a predetermined number of rotation attempts in the opposite direction, or after a predetermined duration, is followed, as the arrow 136 shows, by a return to the rest phase so as to possibly perform a maintenance or manual operation to unblock the blades. This return phase is possibly associated to the presentation of a defect signal to the operator (visual or acoustic signal, . . . ).

[0103] The reference 142 indicates a possible control operation of the rotation which, as the arrow 140 shows, may take place during the mowing phase 102. This may be a continuous or periodic verification of the rotation of the blade drive motor or a rotation of the blades. It is comparable to the verification steps 112, 122 and 132 mentioned previously.

[0104] In case of normal rotation, the mowing phase 102 is continued as indicated by an arrow 144.

[0105] In case of a sudden blockage, the control of the motor may repeat the blade startup phase 108 as indicated by an arrow 146. It may possibly be accompanied by a lifting 150 of the cutting unit.

[0106] It bears repeating that FIG. 3 only illustrates one particular possibility of controlling the blade drive motor.