JP3426450B2 - Engine braking device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a braking device for an engine mounted on a power working machine such as a power lawnmower, and more particularly to a brake on one side wall of a crankcase supporting a crankshaft having a flywheel fixed to one end. The shoe is pivotally supported so that it can be swung between a braking position in which it is pressed against the outer peripheral surface of the flywheel and a release position in which it is spaced from the outer peripheral surface, and the pivot shaft is radially inward from the outer peripheral surface of the flywheel. The present invention relates to an improvement in which the pressure contact portion of the brake shoe with respect to the outer peripheral surface of the flywheel is offset from the pivot in the rotational direction of the flywheel while being arranged in the position.

[0002]

2. Description of the Related Art A braking device for such an engine has already been proposed by the present applicant (see Japanese Utility Model Laid-Open No. 8-172846).

[0003]

In such a braking system for an engine, since the pivot axis of the brake shoe is arranged inward of the outer peripheral surface of the flywheel, the operating arm of the brake shoe is slightly moved from the outer peripheral surface of the flywheel. Only by projecting it, the effective length of the operating arm can be sufficiently secured. Moreover, the offset arrangement of the pressure contact part of the brake shoe with respect to the pivot axis makes the brake shoe a leading type, and self-guides during braking. There is an advantage that a large braking force can be exerted by the action.

However, in such an engine braking device, the pressure contact portion of the brake shoe inevitably occupies a position axially separated from the pivot shaft due to its structure. The braking reaction force causes a tilting moment to tilt the brake shoe toward the crankcase side, which causes a large frictional resistance between the axis and the brake shoe, which increases the braking force by the self-induction action of the brake shoe. May not be fully performed.

The present invention has been made in view of the above circumstances, and the tension of a brake spring is used to suppress the occurrence of a tilting moment of a brake shoe during braking without detracting from the above-mentioned advantages, and self-induction. An object of the present invention is to provide a braking device for the engine, which is capable of effectively increasing the braking force by the action.

[0006]

In order to achieve the above object, the present invention provides a brake shoe on one side wall of a crankcase that supports a crankshaft having a flywheel fixed to one end thereof, and a brake shoe on the outer peripheral surface of the flywheel. A brake spring is supported between the crankcase and the brake shoe so that the brake shoe can swing between a pressing position in which it is pressed and a release position that is separated from the outer peripheral surface, and a brake spring that urges the brake shoe toward the braking position is placed between the crankcase and the brake shoe. In the braking device of the engine, the pivot shaft is arranged radially inward from the outer peripheral surface of the flywheel, while the pressure contact portion of the brake shoe with respect to the outer peripheral surface of the flywheel is offset from the pivot shaft in the rotational direction of the flywheel. , The brake spring is pushed by the tension so that the press contact portion moves away from the supporting surface for the pivot of the crankcase. Kishu the first characterized in that arranged to urge the.

According to this feature, the tension of the brake spring imparts to the brake shoe a tilting moment that tends to tilt it to the side opposite to the crankcase, but this moment is due to the braking reaction force from the flywheel during braking. It is possible to balance the tilting moment of the brake shoe toward the crankcase side, or to significantly reduce the moment.

According to the present invention, in addition to the above characteristics, when the brake shoe is viewed from the outside along a straight line connecting both axes of the crankshaft and the pivot, the line of tension of the brake spring acts on the brake shoe of the pivot. The second feature is that the brake spring is arranged so as to pass through the support point.

According to this feature, the tilting moment of the brake shoe due to the tension of the brake spring can be reduced as much as possible during non-braking.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below based on the embodiments of the present invention shown in the accompanying drawings.

First, referring to FIG. 1, a walk-behind power lawn mower 1 includes a housing 4 supported by front wheels 2 and rear wheels 3.
Have. A vertical engine 5 having a crankshaft 6 arranged vertically is mounted on the upper surface of the housing 4.
The rotary cutting blade 7 attached to the lower end of the crankshaft 6 is arranged in the housing 4. A turf bag 9 is attached to the steering handle 8 fixed to the rear end of the housing 4, and the turf cut by the cutting blade 7 is stored therein.

2 to 5, a flywheel 10 is fixed to the upper end of a crankshaft 6 of the engine 5, and a large number of blades 11 constituting a cooling fan are integrally projected on the upper end surface thereof. Further, a ring gear 12 with which a pinion of a starting motor (not shown) meshes is integrally formed on the outer periphery of the lower end portion.

A cylindrical outer peripheral surface 1 of the flywheel 10
A brake shoe 13 that cooperates with the shaft 0a is attached to a crankcase 14 that supports the crankshaft 6 via a pivot 15.

The pivot 15 is located inward of the outer peripheral surface 10a of the flywheel 10 in the radial direction.
4 is screwed to a boss 16 formed on the upper wall.

The brake shoe 13 is supported by the pivot 15 and extends between the crankcase 14 and the flywheel 10 and extends outwardly from the outer peripheral surface 10a of the flywheel 10, and the arm 13a is bent from the tip of the arm 13a. The flywheel 10 has a pressure contact portion 13b facing the outer peripheral surface 10a, and a lining 17 is bonded to the pressure contact portion 13b.

As shown in FIG. 3, the brake shoe 13 has a braking position B where the lining 17 is pressed against the outer peripheral surface 10a of the flywheel 10 and a release position A where the lining 17 is separated from the outer peripheral surface 10a. And the brake shoe 13 is formed so that the press contact portion 13b is offset in the rotational direction R of the flywheel 10 from the pivot shaft 15 at least at the braking position B thereof. .

In FIG. 5, the brake shoe 13 has
A brake spring 19 that urges this toward the braking position B is connected as follows. That is, the brake spring 19 is composed of a tension coil spring, and both ends of the brake spring 19 are connected to the connecting piece 18 formed at the front end of the pressure contact portion 13b of the brake shoe 13.
And the locking pin 2 protruding from the upper wall of the crankcase 14.
7 and. At that time, the connecting piece 18 and the locking pin 2
When the brake shoe 13 is viewed from the outside along a straight line L (FIG. 3) connecting the crankshaft 6 and the pivot shaft 15, the tension action line F of the brake spring 19 indicates that the brake shoe 13 is the brake shoe 13 of the pivot shaft 15. Is arranged so as to incline away from the upper surface of the crankcase 14 in the direction of rotation R of the flywheel 10 from the support point P for.

Further, as shown in FIG. 3, the brake shoe 1
The operation arm 20 is integrally formed with the third arm portion 13a. The operating arm 20 extends on the radial line of the flywheel 10 that crosses the center of the pivot 15 and projects to the outside of the outer peripheral surface 10 a of the flywheel 10 and also covers the crankcase 14 that covers one side of the flywheel 10.
It is formed so as to penetrate through the window 22 formed in 1. An operation wire 24 that is pulled by a brake release lever 23 (see FIG. 1) attached to the steering handle 8 is connected to the tip of the operation arm 20. The operation wire 24 is arranged substantially along the tangent line of the outer peripheral surface of the flywheel 10, and therefore is substantially perpendicular to the operation arm 20. Thus, when the operation wire 24 is pulled, the brake shoe 13 can be swung to the release position A via the operation arm 20.

An engine stop switch 25 for disabling an ignition circuit (not shown) is installed on the upper surface of the crankcase 14, and an operating lever 25a of this switch and the connecting piece 18 of the brake shoe 13 are linked by a coil spring. It is connected via 26. As a result, the engine stop switch 25 is linked to the braking position B and the releasing position A of the brake shoe 13 and is automatically switched between an operating state and a non-operating state.

Next, the operation of this embodiment will be described.

The brake release lever 23 is turned to the steering handle 8
If the operator grasps the operation wire 24 and pulls the operation wire 24, the brake shoe 13 is held at the release position A, and the engine stop switch 25 is in the inoperative state.
Can be started to perform lawn mowing work with the cutting blade 7.

Now, if the brake release lever 23 is released to stop the operation of the engine 5, the brake shoe 1
3 swings to the braking position B with the tension of the brake spring 19, and accordingly, the engine stop switch 25 operates to deactivate the ignition circuit, so that the brake shoe 13 gives friction to the outer peripheral surface 10a of the flywheel 10. The braking force can quickly stop the inertial rotation of the crankshaft 6 system.

At this time, the pressure contact portion 13 of the brake shoe 13
Since b is offset from the pivot 15 in the rotation direction R of the flywheel 10, the brake shoe 13 is of a leading type, and a self-induction action occurs during braking. That is, the brake shoe 13 is encouraged to swing in the pressure contact direction with the flywheel 10 due to the frictional force with the flywheel 10, and can exert a large braking force.

By the way, in this engine braking device,
As shown in FIG. 5, because of its structure, the pressure contact portion 13b of the brake shoe 13 overhangs above the crankcase 14 from the support point P of the pivot 15 for the brake shoe 13 by a distance s. Sometimes
The braking reaction force from the flywheel 10 exerts a tilting moment m _{1 on} the brake shoe 13 in order to tilt it to the crankcase 14 side. However, the brake spring 19 connected to the brake shoe 13 has its tension acting line F Is obliquely arranged so as to be separated upward from the crankcase 14 toward the rotational direction R side of the flywheel 10, so that the tension of the brake spring 19 causes the brake shoe 1 to move.
3 gives a tilting moment m ₂ which is in the opposite direction to the tilting moment m ₂ which tends to tilt it to the side opposite to the crankcase 14. As a result, both moments m ₁ and m ₂ are balanced, or the former moment m ₁
Can be significantly reduced. Thus, the swinging resistance of the brake shoe 13 around the pivot 15 due to the braking reaction force is reduced, so that the braking force can be effectively increased in combination with the self-induction action of the brake shoe 13.

In this engine braking system, the pivot 15 of the brake shoe 13 has the outer peripheral surface 10 of the flywheel 10.
The effective length of the operation arm 20 can be ensured to be sufficiently large because the operation arm 20 is arranged inward of a and the operation arm 20 projects from the outer peripheral surface 10a of the flywheel 10. Therefore, even if the operating wire 24 is arranged along the tangent line of the outer peripheral surface of the flywheel 10 while suppressing the protrusion of the operating arm 20 to the outer periphery of the flywheel 10 as much as possible,
The traction force is efficiently transmitted to the brake shoes 13,
The release operation can be performed lightly against the tension of the brake spring 19.

Moreover, in FIG. 5, the brake spring 19 has a line of tension F in which the brake shoe 13 of the pivot 15 is located.
Since it is arranged so as to pass through the support point P with respect to, the fall of the brake shoe 13 to the upper side of the crankcase 14 due to the tension of the brake spring 19 can be prevented as much as possible in the brake released state, and the swing can be smoothly performed.

The present invention is not limited to the above embodiment, but various design changes can be made without departing from the scope of the invention. For example, the engine stop switch 25 can be interlocked with the brake release lever 23.

[0028]

As described above, according to the first aspect of the present invention, the brake shoe tension is utilized to attach the brake shoe in the direction in which the pressure contact portion of the brake shoe moves away from the supporting surface for the pivot of the crankcase. The moment of tilting the brake shoe to the opposite crankcase side due to the tension of the brake spring balances the tilting moment of the brake shoe to the crankcase side due to the braking reaction force from the flywheel during braking, or By significantly reducing the moment, the swinging resistance of the brake shoe around the pivot axis due to the braking reaction force can be reduced, and the braking force can be effectively increased in combination with the self-induction action of the brake shoe.

Further, according to the second aspect of the present invention, when the brake shoe is viewed from the outside along a straight line connecting both axes of the crankshaft and the pivot, the line of tension of the brake spring is the brake shoe of the pivot. Since the brake spring is arranged so as to pass through the support point for, the tilting moment of the brake shoe due to the tension of the brake spring can be reduced as much as possible during non-braking, and the swing can be performed smoothly.

[Brief description of drawings]

FIG. 1 is a side view of a power lawnmower equipped with the device of the present invention.

FIG. 2 is a side view of an engine of the power lawnmower.

3 is a sectional view taken along line 3-3 of FIG.

4 is a sectional view taken along line 4-4 of FIG.

5 is a view on arrow 5 of FIG.

[Explanation of symbols]

5 ... Engine 6 ... Crankshaft 10 ... Flywheel 10a ... outer peripheral surface 13 ... Brake shoes 13a ... Arm part 13b ... Pressure contact part 14 ... Crankcase 15 ... Axis 19 ... Brake springs 20 ... Operation arm 24 ... Operating wire A: Release position B: Braking position F ... tension acting line L: straight line P: Support point R: Direction of rotation

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) F16D 49/00 A01D 34/68 A01D 34/76 F02B 77/00

Claims (2)

(57) [Claims] 1. A crankcase (14) for supporting a crankshaft (6) having a flywheel (10) fixed to one end thereof.
The brake shoe (13) is attached to the braking position (B) where it comes into pressure contact with the outer peripheral surface (10a) of the flywheel (10).
And a release position (A) separated from the outer peripheral surface (10a) of the crankcase (14) and the brake shoe (13). A brake spring (19) for urging toward the braking position (B) is stretched, and the pivot shaft (15) is arranged radially inward from the outer peripheral surface (10a) of the flywheel (10), while the brake shoe ( 13) of the flywheel (10) outer peripheral surface (10a) pressure contact portion (13
In a braking device for an engine, in which b) is offset from the pivot shaft (15) in the direction of rotation (R) of the flywheel (10), a brake spring (19) causes the tension of the brake spring (19) to cause the pressure contact portion (13b) to crank. Brake shoes (13) away from the support surface for the pivot (15) of the case (14)
An engine braking device, which is arranged to urge the engine. 2. The brake according to claim 1, wherein when the brake shoe (13) is viewed from the outside along a straight line (L) connecting both axes of the crankshaft (6) and the pivot (15). Brake spring (19), characterized in that the brake spring (19) is arranged such that the line of tension (F) of the spring (19) passes through the support point (P) of the pivot (15) for the brake shoe (13). .