CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National Phase Application of PCT/JP2017/041321, filed Nov. 16, 2017, which claims the benefit of priority to JP Application No. 2016229549, filed Nov. 25, 2016, the contents of which are hereby expressly incorporated by reference in their entirety.

TECHNICAL FIELD

The present invention relates to walk-behind power equipment, such as lawn mowers, grass cutters, snow blowers, tillers, etc.

BACKGROUND ART

A walk-behind lawn mower including a main body provided with a pair of left and right front wheels and a pair of left and right rear wheels, a blade provided in a lower part of the main body, a drive source that drives the blade and the rear wheels, and a handle extending rearward and upward from the main body is known (for example, Patent Document 1). Many of such walk-behind lawn mowers are not provided with a steering mechanism. Therefore, the operator changes the direction of the main body by a turning operation including pressing down the handle to tilt the main body rearward and lift the front wheels from the ground, pushing the handle left or right in that state to change the direction of the main body, and bringing the front wheels into contact with the ground after finishing the change of the direction.

PRIOR ART DOCUMENT(S)

Patent Document(s)

Patent Document 1: JP2011-206018A

SUMMARY OF THE INVENTION

Task to be Accomplished by the Invention

In a lawn mowing operation using the aforementioned lawn mower, the operator moves the lawn mower straight forward to mow the lawn in a straight line with a predetermined mowing width, and causes the lawn mower to make a U-turn at an end of the field through the above-described turning operation. At this time, it is preferred to control the direction and position of the lawn mower accurately such that an edge of the next swath overlaps with an edge of the previous swath, and the next travel path is in parallel with the previous travel path. However, because the rear wheels are rotated by the power from the drive source during the turning operation also, the operator is required to have a certain level of skill to properly operate the lawn mower. In addition, there is a problem that in the turning operation, the blade is moved away from the ground and exposed, and therefore, the noise due to driving of the blade becomes large. Thus, there is a problem in the power equipment such as a walk-behind lawn mower in regard to commercial acceptability such as operability and noise level during turning operation.

In view of the above background, an object of the present invention is to improve commercial acceptability of walk-behind power equipment during turning operation.

Means to Accomplish the Task

To achieve the above object, one embodiment of the present invention provides a walk-behind power equipment, comprising: a main body provided with a front wheel and a rear wheel; a work unit provided on the main body; a work motor that drives the work unit; a travel motor that rotates the rear wheel; a handle provided on the main body to extend rearward and upward; a posture detection means that detects a rearward tilted state of the main body in which the rear wheel is in contact with a ground and the front wheel is spaced from the ground; and a control unit that drive-controls the work motor and the travel motor, wherein when the main body is in the rearward tilted state, the control unit causes a rotational speed of the travel motor to be reduced compared to when the front wheel is in contact with the ground, or causes a rotational speed of the work motor to be reduced compared to when the front wheel is in contact with the ground.

According to this arrangement, when the rearward tilted state of the main body is detected, the rotational speed of the rear wheel is reduced, whereby the turning operation of the power equipment by the operator becomes easy, or when the rearward tilted state of the main body is detected, the rotational speed of the blade is reduced, whereby the noise caused by the blade is reduced.

Further, in the above arrangement, preferably, the posture detection means includes a tilt angle detection means that detects a tilt angle of the main body about a lateral axis, and when the tilt angle is greater than or equal to a predetermined tilt angle determination value, the control unit causes the speed of the travel motor to be reduced compared to when the tilt angle is smaller than the tilt angle determination value.

According to this arrangement, the rearward tilted state of the main body is detected based on the tilt angle detected by the tilt angle detection means.

Further, in the above arrangement, preferably, the posture detection means includes a tilt angle detection means that detects a tilt angle of the main body about a lateral axis, and during a period from when the tilt angle becomes greater than or equal to a predetermined tilt angle determination value and a change rate of the tilt angle becomes greater than or equal to a predetermined change rate determination value to when the tilt angle becomes smaller than or equal to a predetermined restoration determination value, the control unit causes the speed of the travel motor to be reduced compared to when the tilt angle is smaller than the tilt angle determination value.

According to this arrangement, when it is determined whether the power equipment is in a state in which the rotational speed of the travel motor should be reduced, it is possible to take into account the background when the main body is placed into the tilted state because not only the tilt angle but also the change rate of the tilt angle is taken into account. For instance, in a case where the operator pushes down the handle and the main body is tilted thereby, the change rate of the tilt angle of the main body is large, and accordingly, the rotational speed of the travel motor is reduced. On the other hand, in a case where the ground on which the main body travels is sloped and the main body tilts gradually as a result of travel of the main body on the ground such that the tilt angle becomes greater than or equal to the tilt angle determination value, the rotational speed of the travel motor is not reduced.

Further, in the above arrangement, preferably, the tilt angle detection means is an acceleration sensor that outputs a signal corresponding to an acceleration, and the control unit performs low-pass filtering process on the signal from the acceleration sensor to remove at least a portion of the signal corresponding to a dynamic component of the acceleration, and calculates the tilt angle based on the signal that has been subjected to the filtering process.

According to this arrangement, the tilt angle detection means can be made compact and simple.

Further, in the above arrangement, preferably, the power equipment further comprises an operation input means that inputs a signal corresponding to an operation by an operator to the control unit, wherein the control unit drive-controls the travel motor according to the signal from the operation input means, and changes a filter used in the low-pass filtering process according to the signal from the operation input means.

According to this arrangement, when it is determined based on the operation signal from the operation input means that the travel motor is under acceleration or deceleration and a fore-and-aft acceleration is generated in the main body, the filter is changed such that the dynamic component of the acceleration detected by the acceleration sensor is removed even more reliably.

Further, in the above arrangement, preferably, the control unit increases a removal ratio of a high-frequency component of the signal from the acceleration sensor by changing the filter when acceleration or deceleration of the travel motor is determined based on the signal from the operation input means.

According to this arrangement, when it is determined that the travel motor is under acceleration or deceleration and a fore-and-aft acceleration is generated in the main body, the dynamic component of the acceleration detected by the acceleration sensor is removed even more reliably.

Further, in the above arrangement, preferably, the posture detection means includes a load detection means that detects a downward load applied to the handle, and when the load is greater than or equal to a predetermined load determination value, the control unit causes the speed of the travel motor to be reduced compared to when the load is smaller than the load determination value.

According to this arrangement, the rearward tilted state of the main body can be detected based on the downward load applied to the handle.

Further, in the above arrangement, preferably, the posture detection means includes a load detection means that detects a downward load applied to the handle and a tilt angle detection means that detects a tilt angle of the main body about a lateral axis, and when the load is greater than or equal to a predetermined load determination value and the tilt angle is greater than or equal to a predetermined tilt angle determination value, the control unit causes the speed of the travel motor to be lowered compared to when the load is smaller than the load determination value or the tilt angle is smaller than the tilt angle determination value.

According to this arrangement, the rearward tilted state of the main body can be detected even more reliably based on the downward load applied to the handle and the tilt angle of the main body.

Effect of the Invention

According to the foregoing arrangement, the turning operation of the walk-behind lawn mower becomes easy.

