JPH0541627Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a power transmission device for a working machine such as a lawn mower, and particularly relates to a power transmission device for driving a working tool such as a cutter blade with a belt.

[Prior art] Conventionally, power transmission devices for working machines were
Something like the one described in Publication No. 15008 was known. In this power transmission device, a braking surface is provided on the pulley of the electric main shaft so that the brake shoe faces each other, and the brake arm that supports the brake shoe and the pulley arm that supports the tension pulley of the transmission belt are connected to each other. The pulley arm is supported so as to swing together, and the pulley arm is biased by a return spring and connected to the operating lever via a wire.

This power transmission device transmits and cuts off power by adjusting the tension of the transmission belt using a tension pulley, and when the power is cut off, the pulley is braked by a brake shoe that is driven together with the tension pulley. .

[Problems to be solved by the invention] However, in such conventional power transmission devices for working machines, the brake arm and the pulley arm are integrally formed, and these arms are not allowed to swing against the return spring. Therefore, there was a problem in that a large amount of force was required to operate the control lever, which placed a heavy burden on the driver.

This invention was made in view of the above-mentioned problems, and aims to provide a power transmission device for a working machine that can be operated with a small operating force, thereby reducing the burden on the driver.

[Means for Solving the Problems] In order to solve the above-mentioned problems, this invention provides a system in which a transmission belt is hung between a drive pulley driven by an engine and a driven pulley connected to a working tool, and the transmission belt is A clutch arm having a tension roller that engages with the transmission belt to adjust the tension of the transmission belt, and a brake arm that engages with the driven pulley and brakes the driven pulley are swingably arranged, In a power transmission device for a working machine that transmits and cuts off power to the work tool by driving an arm, and also drives the brake arm to brake the driven pulley when the power is cut off, the brake arm is approximately It has a bow shape, one end of which is rotatably supported by a frame, and a cam surface formed on the other end of the brake arm on the driven pulley side, which urges the brake arm toward the driven pulley and presses the clutch arm against the clutch arm. consists of a first arm and a second arm, the first arm has its base end rotatably attached to the frame via a spindle, and the second arm has an intermediate portion that rotates coaxially with the spindle of the first arm. In addition to being able to be attached freely,
A cam roller that rolls on the cam surface is provided at one end of the clutch arm, and is supported so that the angle formed by the first arm and the second arm can be adjusted and fixed, and a tension roller separates the clutch arm from the transmission belt. The gist is that the device is biased in the direction of

[Function] According to the power transmission device for a work machine according to this invention, the clutch arm is driven by the operation of an operating lever connected by a wire etc., but the brake arm is driven by a cam roller provided on the clutch arm that is connected to the cam surface. It is driven by rolling. Therefore, the force required to drive the brake arm is small, and a small operating force is sufficient as a whole, reducing the burden on the driver.

[Example] Hereinafter, an example of this invention will be described based on the drawings.

Figures 1 to 3 show a power transmission device for a working machine according to an embodiment of this invention, in which Figure 1 is an overall perspective view of the working machine, Figure 2 is a sectional view of the working machine, and Figure 3 is a sectional view of the working machine. It is an enlarged view of the main part.

In FIG. 1, reference numeral 1 represents a lawn mower as a working machine, and the lawn mower 1 has an engine 3 mounted on the rear upper part of the upper frame 2, and wheels 4 supported on the rear lower part of the frame 2. Also, in frame 2,
A pair of handle pipes 5, 5 extend rearward and upward from the left and right rear ends, and these handle pipes 5,
A main clutch lever 6 is attached to one side of the clutch lever 5, and a blade clutch lever 7 is attached to the other side.
Further, an arm 8 extends forward from the front end of the frame 2, and a guide wheel 10 is attached to the tip of the arm 8. A cutter housing 11 is provided between the guide wheel 10 and the aforementioned wheel 4. Supported. A cutter blade 19 driven by the engine 3 is housed in the cutter housing 11, as will be described later.

As shown in FIG. 2, the engine 3 has a crankshaft 12 hanging down.
A two-stage drive pulley 13 consisting of a large diameter pulley 13a and a small diameter pulley 13b is provided. This drive pulley 13 is a large diameter pulley 13
Driven pulley 1 for the front cutter blade is shown at a.
A transmission belt 20 is hung between the small diameter pulley 13b and a driven pulley 18 for running at the rear.
A driven pulley 16 for the cutter blade is fitted onto the upper end of a shaft 15 that is rotatably supported by a bearing 14 fixed at the center of the cutter housing 11, and a cutter blade 19 is fixed to the lower end of the shaft 15. There is. The driven pulley 18 for running is connected to a shaft 17 connected to a reduction mechanism for the wheels 4.
is attached to.

Furthermore, as shown in FIG. 3, the frame 2 includes a brake arm 22 and a crank arm 23 near the driven pulley 16 for the cutter blade.
are swingably supported. The brake arm 22 has one end rotatably supported by the frame 2 and a cam surface 22a formed at the other end. The brake arm 22 has a substantially arcuate shape with a radius of curvature substantially equal to the radius of curvature of the driven pulley 16, and has a friction surface that can come into frictional contact with the outer peripheral surface of the driven pulley 16 on the driven pulley 16 side. The brake arm 22 is biased toward the driven pulley 16 by a spring (not shown), engages its friction surface with the driven pulley 16, and brakes the driven pulley 16. clutch arm 2
3 is constructed by connecting a first arm 24 and a second arm 25 with a bolt 26 in a substantially dogleg shape so that their relative positions can be adjusted. The first arm 24 has a base end rotatably attached to the support shaft 23a of the frame 2, a tension roller 27 that engages with the transmission belt 20 is rotatably supported at the distal end, and a bolt 26 is inserted through the middle part. A long hole 24a is formed.
The second arm 25 has an intermediate portion rotatably attached to a support shaft 23a of the frame 2 coaxial with the first arm 24, and has one end attached to the cam surface 23a of the brake arm 22.
A cam roller 28 rolling on a is rotatably supported, and a screw hole into which a bolt 26 is screwed is formed at the other end. The clutch arm 23 consisting of the first arm 24 and the second arm 25 is biased by a spring (not shown) in a direction in which the tension roller 27 is separated from the transmission belt 20. Further, the clutch arm 23 is connected to the blade clutch lever 7 via a small hole 25a of a second arm 25 constituting the clutch arm 23, a wire (not shown), and the like.

Next, the operation of this embodiment will be explained.

In this power transmission device, when the blade clutch lever 7 is operated, the clutch arm 23 swings counterclockwise in FIG. 3 against the elastic force of the spring, and as shown by the solid line in FIG. While the transmission roller 27 presses the transmission level 20,
The cam roller 28 is connected to the cam surface 2 of the brake arm 22.
2a to rotate the brake arm 22 clockwise. Therefore, the transmission belt 20 is tensed and power is transmitted from the engine 16 to the driven pulley 16, and the brake arm 22 releases the driven pulley 16, causing the driven pulley 16 to rotate. At this time, the cam roller 28 rolls on the cam surface 22a of the brake arm 22 to drive the brake arm 22, so the force required to drive the brake arm 22 is small, reducing the burden on the driver. In particular, since the brake arm 22 has the cam surface 22a formed at the farthest position from the point of support to the frame 2, the force required to drive the brake arm 22 is smaller, as is clear from the lever principle. Become.

When the blade clutch lever 7 is released, the clutch arm 23 swings clockwise as shown by the two-dot chain line in FIG. 3 due to the elastic force of the spring, the transmission belt 20 is relaxed, and the cam roller 28 is It is separated from the brake arm 22. Therefore, the power from the engine 3 to the driven pulley 16 is cut off, and the brake arm 22 engages with the driven pulley 16 to brake the driven pulley 16.

[Effects of the Invention] As is clear from the above description, the power transmission device for a working machine according to the present invention provides the following effects.

Since the cam roller provided on the clutch arm contacts and engages with the cam surface formed on the brake arm, and the cam roller drives the brake arm, the force required to drive the brake arm is reduced, reducing the burden on the driver.

The second arm, which acts on the cam surface, is connected to the middle part of the first arm across the support shaft to the frame, so the length of the first and second arms is determined by the tension on the belt and the attachment to the clutch arm. It can be set independently depending on the faction, reducing the operating force.

[Brief explanation of drawings]

Figures 1 to 3 show a power transmission device for a working machine according to an embodiment of this invention, with Figure 1 being an overall perspective view, Figure 2 being a sectional view, and Figure 3 being an enlarged plan view of the main parts. be. 1... Lawn mower (work machine), 3... Engine, 7
...Blade clutch lever, 13...Drive pulley, 16...Driven pulley, 19...Cut blade (work tool) 20...Transmission belt, 22
...Brake arm, 22a...Cam surface, 23...
...Clutch arm, 23a...Spindle, 25a...
Small hole, 26... bolt (insertion member), 27... tension roller, 28... cam roller.

Claims (1)

[Scope of utility model registration request] A transmission belt is hung between a drive pulley driven by an engine and a driven pulley connected to a working tool, and a tension roller is provided that engages with the transmission belt to adjust the tension of the transmission belt. A clutch arm and a brake arm that engages with the driven pulley and brakes the driven pulley are swingably arranged, and the clutch arm is driven to transmit and cut off power to the working tool, In a power transmission device for a working machine that drives the brake arm to brake the driven pulley when power is cut off, the brake arm has a substantially bow shape, one end of which is rotatably supported by a frame, and the other A cam surface is formed on the driven pulley side of the end, and this brake arm is biased toward the driven pulley. The second arm is rotatably attached to the frame via a support shaft, and the second arm has an intermediate portion rotatably attached coaxially with the support shaft of the first arm, and a cam roller that rolls on the cam surface is attached to one end of the second arm. the first arm and the second arm are supported so that the angle formed by the first arm and the second arm can be adjusted and fixed, and the tension roller biases the clutch arm in a direction in which it moves away from the transmission belt. power transmission device for work equipment.