JPH0573933B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for setting the pitch of a timing belt that is applied to a vehicle engine or the like.

(Prior Art) A typical example of a timing belt that is applied to a vehicle engine or the like will be explained with reference to FIG.

A drive pulley 2, an intake shaft pulley 3, an exhaust shaft pulley 4, and a pump pulley 5 are provided at the shaft ends of a drive shaft, an intake camshaft, an exhaust shaft, and a water pump shaft, respectively, which are incorporated into the vehicle engine 1. It is fitted.

A timing belt 50 is wrapped around these pulleys, and the driving force of the drive pulley 2 is transmitted to the pulleys 3 and 4 and the pump pulley 5 via the timing belt 50.

In addition, 6 is the tensioner, and the timing belt is 50
This prevents sagging.

The structure of the timing belt 50 will be explained with reference to FIG.

The timing belt 50 is formed by molding a sawtooth rubber part 52 around a tensile body 51 made of steel wire or glass fiber cord as a core, and covering the tooth side surface of the rubber part 52 with a canvas 53. be.

The rubber portion 52 is formed by integrally molding a round tooth portion 52a and a flat plate portion 52b.

The timing belt 50 having this configuration has expansion and contraction restricted by the action of the tensile member 51, and wear of the rubber portion 52 is prevented by the action of the canvas 53.

Next, a conventional timing belt pitch setting method will be explained.

FIG. 4 is an enlarged view of the timing belt 50 and drive pulley 2.

Let G be the distance between the center of the tensile member 51 and the outer surface of the canvas 53 attached to the flat plate portion 52b.

Let H be the distance between the tip points 52c, 52c of the round tooth portion 52a of the timing belt 50.

Let F be the distance between the bottom points 2a of the pulley 2.

The above G is called the PLD value and is standardized in the industry. For example, with pitch code L, the PLD value is 0.381
mm, the PLD value at pitch code H is 0.686 mm, and is determined in stages.

Therefore, in the past, the pitch H of the timing belt was uniquely determined according to the pitch code, and the pitch F of the pulley was determined to be equal to the pitch H.

In other words, as shown in Fig. 1, in the past, even if the number of teeth and outer diameter of multiple pulleys varied, the pitch of the pulleys and the pitch of the belt were not corrected every time, and only the rubber part was adjusted. The meshing has been maintained through elastic deformation of 52.

However, in recent years, as engines have become faster and more powerful, there has been a strong desire to increase the strength of timing belts.

In order to meet this demand, conventional timing belts as shown in Japanese Patent Application Laid-Open No. 53-82951 and the
A timing belt with an increased PLD value G is being used on a trial basis.

(Problems to be Solved by the Invention) The timing belt disclosed in Japanese Patent Application Laid-open No. 53-82951 maintains the PLD value, uses a stronger material for the tensile body, and has a structure in which the canvas is overlapped. This is what I did. However, since the PLD value is limited, there is a limit to reinforcement.

The latter increases the PLD value G and increases the thickness of the timing belt. However, as the PLD value G increases, the timing belt 50 shown in FIG.
As shown in FIG. 6, the meshing state of the drive pulley 2 deteriorates, causing the belt to resonate, doubling the noise, and eventually causing a tooth skipping phenomenon. Therefore, in the latter method, when increasing the PLD value G, the rate of increase is suppressed as much as possible, so the reinforcement rate becomes low.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention wraps the timing belt around the pulley, bends the tension body inside the timing belt, and in this state, the center of the pulley is bent. Extend a line segment passing through the bottom point of the pulley from the point, find the intersection of this line segment and the above tensile body, define the arc length of the tensile body at the adjacent intersection points,
This specified arc length is defined as the tooth pitch of the timing belt.

If the tensile member is located further away from the pulley, the pitch of the teeth of the timing belt will be set larger. Therefore, the present invention increases the PLD value of the timing belt without changing the pulley pitch.

(Example) When a timing belt 50 having a structure similar to that described in the prior art section is placed around a vehicle engine 1 as shown in FIG. 1, the pitch of the timing belt 50 is described below. Set in the method.

FIG. 2 is an operational diagram according to an embodiment of the present invention,
The timing belt 50 meshes with the drive pulley 2.

Tensile body 5 forming the core of the timing belt 50
Let B be the distance between the center line A of 1 and the outer surface of the canvas 53. The center line A of the tensile member 51 draws an arc whose radius is the radius of the drive pulley 2 plus the distance B.

On the other hand, starting from the center point 2b of the drive pulley 2,
The line segments passing through the adjacent tooth bottom points 2a, 2a of the drive pulley 2 are defined as a line segment C and a line segment D, respectively.

Let E be the length obtained by dividing the arcuate center line A into a line segment C and a line segment D.

At the distance B and division length E defined above,
In the present invention, when the PLD value of the timing belt is B, the pitch of the teeth of the timing belt 50 is set equal to the division length E.

That is, in the method of this embodiment, the pitch F of the drive pulley is
The timing belt tooth pitch is set according to the change in B, which corresponds to the PLD value, without changing B from the conventional value.

In this embodiment, the driving pulley is used as the reference, but the invention is not limited to this, and other driven pulleys may be used as the reference.

(Effects of the Invention) As described above, the present invention wraps the timing belt around the pulley, curves the tensile member inside the timing belt, and in this state passes from the center point of the pulley to the bottom point of the pulley. Extend the line segment to
The intersection point between this line segment and the tensile body is determined, the arc length of the tensile body is defined at the adjacent intersection points, and the defined arc length is set as the pitch of the teeth of the timing belt, For example, if the tensile member is located further away from the pulley, the pitch of the teeth of the timing belt will be set larger.
In other words, in the present invention, the pitch of the teeth was determined uniquely in the past, but in the present invention, the pitch of the teeth is determined while the belt is wrapped around the pulley, so it is possible to determine the belt dimensions that match the pulley. In addition to reducing belt resonance and noise generation and preventing tooth skipping, it is also possible to easily design a timing belt with a desired strength, making it possible to create an extremely useful timing belt.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a vehicle engine, FIG. 2 is an explanatory diagram of the pitch of a timing belt according to an embodiment of the present invention, and FIG. 3 is an explanatory diagram of the structure of a timing belt.
FIG. 4 is an explanatory diagram of the timing belt pitch according to the conventional method, and FIGS. 5 and 6 are action diagrams according to the conventional method. In the figure, 1 is a vehicle engine, 2 is a drive pulley, 2a is a tooth bottom point, 2b is a center point, 3 is an intake side shaft pulley, 50 is a timing belt, and 51
is a tensile member, A is the center line of the tensile member, C and D are line segments passing through the tooth bottom point, and E is the pitch of the teeth of the timing belt.

Claims (1)

[Claims] 1. A method for setting the pitch of a timing belt of a transmission device that transmits the driving force of a driving pulley to a driven pulley using a timing belt, the timing belt being wound around the pulley to create a tensile member inside the timing belt. In this state, extend a line segment passing from the center point of the pulley to the bottom point of the pulley, find the intersection of this line segment and the above tensile body, and calculate the arc length of the tensile body at the adjacent intersection points. The specified arc length is used as the pitch of the teeth of the timing belt, and if the tensile member is provided at a position further away from the pulley, the pitch of the teeth of the timing belt is A timing belt pitch setting method characterized by setting a larger pitch.