JPH0478790A - Driving gear device for outboard motor - Google Patents

Abstract

PURPOSE:To improve the durability and reliability of a driving gear device by heavily carboquenching a bevel pinion, ordinarily carboquenching a forward and a reverse gear which mesh with the above pinion, and sharply elongating a time when a pitting action occurs on the tooth surface of the bevel pinion. CONSTITUTION:A bevel pinion 2 is heavily carboquenched, and a forward and a reverse gear 3, 4 which mesh with the pinion 2 are ordinarily carboquenched. Thus tooth surfaces of the gears 3, 4 wears slightly early in comparison with the tooth surface of the pinion 2 to reduce local oil pressure, and the pitting resistance of the tooth surface of the pinion 2 can therefore be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an outboard motor or a propulsion gear device provided in a propulsion section of an outboard/outboard motor.

[Conventional technology]

In a conventional propulsion device such as an outboard motor, for example, as shown in FIG.
Dog teeth 3.4. bevel gears (forward gear and reverse gear) 3.4 are opposed and meshed with each other, and the forward gears 3, 4 are provided with splines 5.4. The propeller shaft 5 having the above-mentioned dog teeth 3 is fitted on both end faces. ．． 4. Dog teeth that mesh with 6. ,6. Dog clutch 6 with
is slidably provided on the spline 5I of the propeller shaft 5, and a first bushing rod 7 and a second bushing rod 8 engaged therewith are attached from the end surface of the propeller shaft 5.
On the other hand, a long through hole 5. is inserted into the sliding portion of the dog clutch 6 of the propeller shaft 5. is provided,
A cross pin 9 is provided passing through the first bushing rod 7 and the dog clutch 6. The second bushing rod 8 is connected to a shift lever mechanism 10. Note that the bevel pinion 2 and the forward gear and reverse gear 3.4 are straight bevel gears or spiral bevel gears.

And these bevel teeth binions 2. The forward gear and reverse gears 3 and 4 are usually carburized and quenched to harden their surfaces before use.

C invention tries to solve the problem! I! u) However, in outboard motor drive gears, pinions have fewer teeth than forward gears and reverse gears (and the problem is that the pitting resistance of the tooth surface is relatively low due to the large load and high slip rate). As a solution to this problem, the combination of a bevel-toothed pinion that was conventionally carburized and quenched, and its forward gear and reverse gear, had problems with durability as the pinion resistance of the tooth surface of the pinion was significantly lacking. Therefore, when the bevel gear, forward gear, and reverse gear were both highly carburized and quenched, the pitting resistance improved, but it was still insufficient.

The present invention aims to further improve this pinting resistance and provide a drive gear device for an outboard motor that is highly durable and reliable.

[Means to solve the problem]

The present invention provides a drive gear for an outboard motor consisting of a bevel pinion of a drive shaft, and a forward gear and a reverse gear that mesh oppositely with the bevel pinion, wherein the bevel pinion is highly carburized and quenched, and the forward gear and reverse gear are It is a normal carburized and quenched product.

[For production]

The bevel tooth pinion has undergone high-concentration carburizing and quenching, and the forward gear and reverse gear of this gear have undergone normal carburizing and quenching, so the forward gear and reverse gear side have been slightly hardened first compared to the bevel tooth pinion side. wear on the tooth surface, reducing local surface pressure and improving pinting resistance on the tooth surface on the bevel tooth pinion side.

〔Example〕

Hardenable structural steel material SCM420H<Carbon content i1
0.2%) to manufacture bevel tooth pinions, forward gears, and reverse gears, and the tooth surfaces of the bevel tooth pinions are subjected to high-concentration carburizing and quenching, and after heat treatment, the carbide on the tooth surface surface is reduced to 2 to 2.
The carbides on the 0 surface, which were made to have a carbon content of 4%, were in a state in which carbides of Cr and Fe were precipitated within martensite, and the area ratio was set to be 20 to 40%. Next, for bevel tooth forward gears and reverse gears, normal carburizing and quenching (surface carbon concentration 0.9 to 1
．． 0wt%) and heat treated. There is no carbide precipitation on the tooth surface.

The inventors conducted a binting occurrence test using a gear testing machine as shown in FIG. In other words, the pinion, forward and reverse gears are all carburized and quenched, and both are carburized and quenched. Experiments were conducted on three types. As a result, it was found that the combination of high concentration for the pinion and normal carburizing and quenching for the forward and reverse gears resulted in the least amount of binding (pinion). To clarify the reason, the amount of tooth surface wear of forward gears subjected to normal and high-intensity carburizing and quenching was measured as shown in FIG.

As a result, compared to the high-concentration carburizing and quenching, the normal carburizing and quenching showed about 5 times the wear amount. In this case, it is thought that the initial wear of the forward gear and reverse gear causes a reduction in the local surface pressure on the tooth surface, extending the pinion life of the pinion.

Figure 1 shows the bevel tooth binion (scM420H9 high concentration carburizing and quenching) of the present invention and the forward gear (SCM420H
, usually carburized and quenched).

In the highly carburized and quenched &Il weave, the carbides on the surface are distributed in granular form, and the outermost surface (depth θ ~ 0.02 m from the surface)
) The carbide on the 0 surface (tooth surface) increases as the carbon concentration approaches 2 to 4% (wt). Regarding the area ratio of carbide, if it is less than 20%, hardness is insufficient, and if it is more than 40%, it becomes brittle, which is not preferable.

〔Effect of the invention〕

In the present invention, the bevel tooth pinion is carburized and quenched at a high concentration, and the forward gear and reverse gear that mesh with this are usually carburized and quenched, so the time for pitting to occur on the tooth surface of the bevel tooth pinion is significantly extended. This enabled us to provide an outboard motor drive gear with high durability and reliability.

[Brief explanation of drawings]

Figure 1 is a pinion and gear hardness distribution diagram according to the present invention, Figure 2 is a tooth surface wear test graph of a forward gear, Figure 3 is a pitting occurrence experiment graph, and Figure 4 is a conventional outboard motor. It is an explanatory diagram of a drive gear for use. 2...Bevel pinion, 3.4...F, forward and reverse gear.

Claims (2)

[Claims] (1) In an outboard motor drive gear consisting of a bevel-toothed pinion of a drive shaft, and a forward gear and a reverse gear that mesh with the bevel-toothed pinion, the beveled pinion is highly carburized and quenched, and the forward gear and reverse gear are normally A drive gear device for an outboard motor, characterized in that it is carburized and quenched. (2) The drive gear device for an outboard motor according to claim 1, wherein the area ratio of carbide precipitation on the tooth surface portion of the bevel toothed pinion is 20 to 40%.