JP2965768B2 - Crankshaft for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crankshaft for an internal combustion engine in which a pin member and a crank arm are joined by shrink fitting.

[0002]

BACKGROUND OF THE INVENTION When crankshafts for internal combustion engines are joined by shrink fit, the crankshaft is generally assembled as either a fully assembled crankshaft or a semi-assembled crankshaft. The former forms each throw by firmly shrink-fitting the crankpins into the bores of the two crank arms, and then separates the individual throws by means of main bearing journal pins, which are likewise fixed by shrink-fitting into the bores of the crank arms. Join the throws. In the latter, a forged or cast throw is joined to a bore of a crankshaft by a pin shrink-fitted. Each throw may be joined by a ring-shaped pin member, as disclosed in British Patent No. 1345768. This pin member is firmly shrink-fitted from the outside onto two axially opposite pins of each throw.

In view of the need to maintain the mutual angles of the throws during operation of the engine, the torque carrying capacity of the shaft is, inter alia,
It is limited by the area of the shrinking surface to engage and the shrinking force acting at right angles to this surface. There is a direct relationship between the desired shrink force and the required thickness of the material surrounding the shrink holes, as it is not desirable for the material to float around the shrink surface. Reducing the ratio between the crankshaft weight and the torque transmitted by the crankshaft is a persistent requirement, but this requires the crankshaft to be cast, as compared to a fully assembled or semi-assembled crankshaft. It will be expensive.

[0004] It is an object of the present invention to provide such a crankshaft having a reduced ratio between shaft weight and maximum allowable torque.

[0005]

From this viewpoint, the crankshaft according to the present invention is characterized in that a friction increasing material is added to at least one of the contracted surfaces to be engaged.

[0006] Compared with conventional crankshafts, the crankshaft has the same coefficient of friction due to the increased frictional coefficient between the shrinking surfaces, i.e., the lower surface pressure between the shrinking surfaces of the assembled crankshaft, due to the increased coefficient of friction. The torque and the contraction surface area can be simultaneously maintained. As a result, the stress level of the crank arm is reduced, so that the cross-sectional area of the arm, in particular the arm portion where a relatively small moment load is often applied during operation of the engine, can be reduced, and therefore the weight can be reduced.

If it becomes possible to reduce the weight of the crankshaft,
It is particularly advantageous for large low-speed combustion engines, which in some cases require the crankshaft to be divided into two parts and mounted on the bottom frame of the engine for handling reasons.

In a conventional crankshaft lathe and crankshaft assembly bench, the maximum lifting capacity is 180 t corresponding to the weight of a well-known shrink fit shaft for an 8 to 9 cylinder engine.
If the engine is made up of 10 to 12 cylinders, the shaft must be divided into two parts and assembled into a chainwheel located in the center of the engine for camshaft chain drive. According to the present invention, the number of cylinders requiring division increases because the shaft becomes lighter. Therefore, even in the case of the engine having a large number of cylinders, the crankshaft can be formed by an undivided crankshaft and a chain wheel disposed at an end of the engine, thereby reducing the manufacturing cost of the shaft and shortening the overall length of the engine. be able to.

In addition, the center level between the crankpin and the main bearing journal can be reduced by reducing the stress level of the crank arm. For this reason, a small engine with a reduced connecting rod can be realized.

When the pin member is designed as an axially extending pin that is firmly shrink-fitted into the axially extending bore of the crank arm, the only manufacturing and cost considerations are that only the shrinking surface at the peripheral edge of the pin is used. Is to add a friction-increasing material. In a preferred embodiment, the effect of the present invention is further enhanced by the application of a friction-increasing material to both the peripheral edge of the pin and the constricting surface that engages the cylindrical inner surface of the lumen.

In an embodiment, the friction-increasing material may be a coating of nickel that exhibits high friction when sliding on steel and exhibits greater friction when sliding on nickel. The nickel coating can be formed in any thickness. If the crankshaft is small, a relatively thin layer can be applied, for example by plasma coating or chemical precipitation, whereas if the crankshaft is larger, a thermal coating can be applied.

In a second embodiment, the friction enhancing material comprises particles that are substantially harder than the base material of the crankshaft or journal member, preferably a carborundum powder. Prior to shrink fitting, the particles are distributed on one or both of the shrinking surfaces that engage and then engage a viscous liquid, such as fat, or are adhered to the surface. When the members are joined by shrink fit, the hard particles penetrate both shrink surfaces to form certain microprojections that greatly increase the torque carrying capability of the shrink surfaces. Carborundum powder is particularly preferred as the particle material. This is because the carborundum powder crystallizes into a very hard and chemically very stable diamond structure, which is transformed and absorbed around the surrounding steel structure during the life of the engine, High safety against particles is obtained.

In a third embodiment, the particles are preferably embedded in a metal substrate which is a nickel coating, so that the above-mentioned friction-increasing properties can be realized with the same coating.

[0014]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of an embodiment of the present invention;

The throw 1 for a semi-assembled crankshaft shown in FIGS. 1 and 2 is manufactured by forging or casting and comprises two arms 2 and a connecting crankpin 3. Each arm 2 has a lumen 4 extending in the axial direction, the substantially circular cylindrical inner surface of this lumen 4 constituting one of two corresponding contracting surfaces. FIG.
Shows a pin 5 with three substantially circular cylindrical parts separated in the axial direction, the central part of which is the journal surface and the two opposite parts 7 of the peripheral edge of the pin are in the assembled state of the shaft. Each of the other contraction surfaces restrained in the corresponding lumen 4 is formed.

The individual throws 1 hold the crankshaft in the crankshaft assembly bench at the right angles to each other and heat the crankshaft arm and / or cool the pin 5 and then replace the part 7 of the pin 5 with the bore 4 By being moved in, it is coupled to the complete axis in a conventional manner. With respect to the lumen, the dimensions of the pins are designed to be large so that when the parts reach the same temperature, the shrinkage stress required to firmly connect the parts occurs.

Hereinafter, members having the same functions as those described above are given the same reference numerals, regardless of whether the shaft is fully assembled or semi-assembled. In the throw 1 for a fully assembled crankshaft as shown in FIG. 4, the main bearing journal pin is formed together with the crankpin as a pin member 5 that is shrink-fitted into the bore of the crank arm 2.

FIGS. 5 to 7 show enlarged views of the transition between the pin member 5 and the crank arm 2 so that the friction-increasing material emerges from the corresponding shrink surface.

In FIG. 5, the contracted surface 7 of the pin member 5 is coated with a nickel layer 8, and the inside of the lumen 4 is similarly coated with a nickel layer 9. Nickel coating on both parts is about 200 mm between surfaces compared to the known uncoated steel surface.
%, Which is usually a pin member, but if only one surface is coated, an increase in friction coefficient of about 50% can be expected. The required shrinkage stress or shrinkage surface area can be varied in inverse proportion to the change in the coefficient of friction, which means that the weight of the off-the-shelf crankshaft for the same allowable torque is reduced. If both parts are coated with nickel, the weight of the arm material located in the annular portion of the radially outer half of the pin member 5 is reduced, for example, by about 20%.

Nickel coating can be performed by electrodeposition or by thermal coating using plasma coating or thermal spraying.

As shown in FIG. 6, the coefficient of friction is further increased because particles 10 which are substantially harder than the base material of the arm 2 or the pin member 5 are added to at least one of the shrinking surfaces. The particles form some kind of microprojections when pressed against both parts as described above and lock both parts when the same temperature is reached.

When a hard ferromagnetic material such as chromium dioxide is used as the granular material, a binder is required to give particles to at least one shrinking surface and to hold the particles on the shrinking surface when joining the shaft. And not. Placing the two parts on a crankshaft bench magnetizes at least one of the parts so that after dispersing the ferromagnetic particles, these particles are magnetized on the shrink surface until both parts are inserted into each other. . Heating one of the components during shrinkage will magnetize the colder component. Magnetization is performed using an electromagnet or an electric coil wound around one component. This method of applying a friction enhancing material to a shrink surface is advantageous in that it is readily applicable to existing machinery for manufacturing crankshafts simply by supplementing the source of magnetization.

FIG. 7 shows a third embodiment, wherein the shrinking surfaces are provided with metal coatings 11, 12 containing hard particles 10. This means that particles 1 such as carborundum powder
This is advantageous when it is necessary to fix the "0" to the shrinking surface and pre-manufacture the arm and the pin member before transporting them to the assembly site of the shaft. A uniform thick layer of metal substrate having the correct thickness may be provided so that the shrinkage stress of the finished shaft reaches a predetermined magnitude. The particle-containing coating film may be provided on the shrink surface using plasma spraying.

The torque transfer capability of the shrinking surface is improved by the geometrical locking of the corresponding surface by the particles, which means that the metal substrate can be nickel-plated so that the coefficient of friction is higher at the part of the substrate surface free of particles. It can be further enhanced by forming from. Although the drawing shows the substrate coating on both parts 2, 5, it is of course possible to apply only the shrink surface of one part.

Alternatively, the crankshaft may be formed by shrink-fitting a ring-shaped pin member on the outer surface of the two axially opposite pins associated with each crankshaft. In this case, the corresponding crank surface consists of the inner surface of the ring and the outer surface of the pin, but at least one of the engaging shrinking surfaces is exactly the same as the surface containing the friction-enhancing material described above.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional side view of a throw for a semi-assembled crankshaft according to the present invention.

FIG. 2 is an end view of a slot for the semi-assembled crankshaft shown in FIG. 1;

FIG. 3 is a side view of a main bearing journal pin.

FIG. 4 is a side view of a throw for an assembled crankshaft according to the present invention.

FIG. 5 is an enlarged sectional view through a contraction surface of a crankshaft according to the present invention.

FIG. 6 is an enlarged sectional view through a contraction surface of a crankshaft according to the present invention.

FIG. 7 is an enlarged sectional view through a contraction surface of a crankshaft according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Throw 2 Arm 3 Crank pin 4 Lumen 5 Pin member 6 Journal surface 7 Shrink surface 8,9 Nickel layer 10 Particles 11,12 Metal coating

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F16C 3/10 F16B 4/00

Claims (10)

(57) [Claims] 1. A crankshaft for an internal combustion engine in which a pin member (5) and a crank arm (2) are joined by shrink fitting, wherein at least one of engaging shrinking surfaces has a friction increasing material (8, 9; 10; 11, 12). 2. The crankshaft of an axially extending pin (5) shrink-fit into an axially extending bore (4) of a crank arm, said pin member comprising: Friction increasing material (8,
9. The crankshaft according to claim 1, wherein 9; 10; 11, 12) are added. 3. The crankshaft of a ring externally shrink-fitted on two axially opposite pins associated with each throw, the pin member being an inner surface of the ring and an outer surface of the pin. 2. The crankshaft according to claim 1, wherein a friction increasing material is added to a contraction surface with which the boss engages. 4. The crankshaft of an axially extending pin (5) fixed by shrink fitting in a bore (4) of a crank arm, said pin member comprising two cylindrical contracting surfaces of said pin. 2. The crankshaft according to claim 1, wherein the friction-enhancing material is added to (7), but this material is not added to the intermediate journal surface (6). 5. The crankshaft according to claim 1, wherein the friction increasing material is a coating of nickel (8, 9). 6. A crank arm (2) wherein said friction increasing material is a crank arm (2).
And particles (1) substantially harder than the base material of the pin member (5).
The crankshaft according to any one of claims 1 to 4, wherein the crankshaft comprises: 7. The friction-increasing material is a coating consisting of a metal substrate (11, 12) embedded with particles (10) substantially harder than the base material of the crank arm (2) and the pin member (5). The crankshaft according to any one of claims 1 to 4, wherein the crankshaft is provided. 8. The method according to claim 1, wherein the particles are carborundum powder (SiC).
The crankshaft according to any one of claims 6 and 7, wherein the crankshaft comprises (10). 9. The crankshaft according to claim 7, wherein said metal substrate (11, 12) contains nickel. 10. The friction-increasing material is chromium dioxide (Cr).
The crankshaft according to any one of claims 1 to 9, wherein the crankshaft is made of O2) (10).