# US 10,869,424 B2 · Power tool, lawn mower, and control method thereof

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- Number: US 10,869,424 B2
- Document ID: US10869424B2
- Status: Granted
- Kind: B2
- Application number: 16/142,131
- Filed: 2018-09-26
- Published: 2019-01-24
- Granted: 2020-12-22
- Earliest claimed: 2016-05-16
- Assignees: Nanjing Chervon Industry Co., Ltd.
- Applicants: Nanjing Chervon Industry Co., Ltd.
- Inventors: Haishen Xu; Zhao Hu; Yangzi Liu; Toshinari Yamaoka
- Web page: https://patentgrep.com/patent/US10869424B2

## CPC

- A01D 34/006: {Control or measuring arrangements}
- A01D 34/69: with motor driven wheels
- A01D 2101/00: Lawn-mowers
- A01D: HARVESTING; MOWING

## Abstract

A lawn mower includes a blade configured to cut grass, a chassis, configured to accommodate the blade, and front and rear wheels connected to the chassis. A motor is configured to drive at least the rear wheel to rotate. A detection apparatus detects the rotational speed of the front wheel and a controller controls the motor. Accordingly, the speed of a front wheel is detected to control a moving speed of the lawn mower, thereby enhancing the performance of the lawn mower and improving the user's experience.

## Claims

### Claim 1

A self-propelled lawn mower, comprising:
a blade configured to cut grass;
a chassis configured to accommodate the blade;
a front wheel connected to a front side of the chassis;
a rear wheel connected to a rear side of the chassis;
a motor at least configured to drive the rear wheel to rotate;
a detection apparatus configured to detect a rotational speed of the front wheel; and
a controller configured to control the motor to decelerate when the rotational speed of the front wheel decreases, wherein
the motor is operably connected to the rear wheel, and the detection apparatus is electrically connected to the controller.

### Claim 2 (depends on 1)

The lawn mower according to claim 1,
further comprising:
a fixed assembly configured to rotate along with the front wheel, wherein
the detection apparatus comprises:
a sensor configured to generate a signal when the fixed assembly passes across a predetermined position; and
the sensor is fixedly connected to the chassis.

### Claim 3 (depends on 1)

The lawn mower according to claim 1, wherein the sensor is disposed at a position near the front wheel.

### Claim 4 (depends on 2)

The lawn mower according to claim 2, wherein the fixed assembly comprises a magnetic member, an infrared reflection member or a photoelectric reflection member.

### Claim 5 (depends on 2)

The lawn mower according to claim 2, wherein the sensor comprises a Hall sensor, an infrared sensor or a photoelectric sensor.

### Claim 6 (depends on 1)

The lawn mower according to claim 1,
further comprising:
a handle for a user to push the lawn mower, wherein
the handle is operably connected to the chassis.

### Claim 7

A self-propelled power tool, comprising:
a handle configured to operate the power tool;
a chassis is connected to the handle;
a front wheel operably connected to a front side of the chassis;
a rear wheel operably connected to a rear side of the chassis;
a motor at least configured to drive the rear wheel to rotate;
a detection apparatus configured to detect a rotational speed of the front wheel;
a controller configured to adjust, according to the detected rotational speed of the front wheel, a current for driving the motor, and
a fixed assembly configured to roll along with the front wheel, wherein
the detection apparatus comprises a sensor configured to generate a signal when the fixed assembly passes across a predetermined position.

### Claim 8

A method for controlling a self-propelled lawn mower, the lawn mower comprising:
a front wheel operably connected to a front side of a chassis;
a rear wheel operably connected to a rear side of the chassis; and
a motor at least configured to drive the rear wheel to rotate; and
the method comprising:
detecting a rotational speed of the front wheel;
determining whether the detected rotational speed of the front wheel is less than a predetermined value; and
when the rotational speed of the front wheel is less than the predetermined value, reducing a drive current of the motor.

### Claim 9 (depends on 8)

The control method according to claim 8, wherein a duty cycle of a drive signal for driving the motor is reduced to reduce the drive current of the motor.