JPH0775958A - Honing method and cylinder bore - Google Patents

Abstract

PURPOSE:To heighten the articulation of cross hatches, formed on the inner surface of a cylinder bore by the rotation and axial movement of a honing head, only on the necessary part so as to reconcile the decrease of oil consumption and initial scuffing with productivity. CONSTITUTION:At the time of machining the inner surface of a cylinder bore 1 from the upper end of the cylinder bore 1 down to a part to which a piston ring slides, in the vicinity of the top dead center of a piston, the rotating speed and vertical moving speed of a honing head are lowered to perform machining. Cross hatches formed by the locus of a grinding wheel supported by the honing head are thereby articulated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to honing for grinding an inner surface of a cylinder bore by rotating and axially moving a honing head to which the grinding wheel is attached while applying a predetermined working pressure to the inner surface of the cylinder bore by the grindstone. The present invention relates to a processing method and a cylinder bore according to the processing method.

[0002]

2. Description of the Related Art Generally, honing is used for precision finishing of the inner surface of a cylinder bore of an engine. In the honing process, the inner surface of the processed hole is ground by using a grindstone, and this grindstone is usually a rectangular parallelepiped having a plurality of equal intervals in the circumferential direction with the central axis direction of the machined hole as the longitudinal direction. The plurality of grindstones are inserted into the machining hole and pressed against the inner surface of the machining hole by a tool called a horn that is radially arranged with respect to the center axis of the grindstone. The inner surface of the hole is processed smoothly and accurately.

As a cylinder bore inner surface honing treatment, there is one disclosed in Japanese Utility Model Laid-Open No. 58-2343. This is because the surface roughness of the portion where the piston ring slides on the inner surface of the cylinder bore is made finer than the surface roughness of the portion where the piston skirt slides, so that the oil holding force is reduced in the portion where the piston ring slides. This is effective in reducing friction loss, fuel consumption, and oil consumption. On the other hand, in the portion where the piston skirt slides, the amount of oil retained is large and seizure resistance is effective.

By the way, the grindstone used for the honing process is usually made of abrasive grains such as diamond.
Since the honing head to which the grindstone is attached rotates and moves up and down by the rotary motor and the vertical movement cylinder, the trajectory of the abrasive grains becomes helical, and the inner surface of the machining hole where the honing head moves is schematically illustrated in FIG. As shown, a crosshatch peculiar to honing is formed. This crosshatch is formed on the inner surface of the machined hole by intersecting two types of helical grinding traces a and b having different inclination directions. On the inner surface of the cylinder bore of the engine, an oil that helps retain and spread the oil. Act as a pit.

[0005]

There is no particular problem with such a cross hatch when the inclination angle and the thickness are uniform and clear as shown in FIG. 6, but as shown in FIG. If the angles are not uniform, and the thickness is not uniform and it is unclear, the cylinder bore inner surface will not fully function as an oil pit and the oil will not be retained sufficiently, increasing the oil consumption. It also causes an initial scuff of the piston.

When the clarity of the crosshatch is improved, the oil holding power is improved, so that the oil consumption and the initial scuffing are improved as shown in FIG. 8, but the productivity is deteriorated as shown in FIG. Tends to become. In other words, in order to improve productivity, it is necessary to sacrifice the clarity of crosshatch to some extent. This is because in order to improve the clarity of the cross hatch, it is necessary to stabilize the honing head rotation speed and vertical movement speed to an extremely high level.
This is because it is necessary to reduce the rotation speed and the vertical movement speed in order to stabilize, and therefore, if the machining operation at such a low speed is performed over the entire area of the cylinder bore, the machining time becomes long.

For this reason, when the clarity of the crosshatch is constant over the entire cylinder bore, it is difficult to achieve both oil consumption and initial scuffing and productivity.

On the other hand, in the technique described in the above-mentioned publication, the crosshatch is not taken into consideration, and moreover, the surface roughness of the entire portion where the piston ring slides is made fine, and this surface roughness is made fine. Even if the cross hatch is replaced by the cross hatch clarification, the clarification area becomes wider, the processing time becomes longer, and the productivity is reduced.

Therefore, according to the present invention, in the crosshatch formed on the inner surface of the cylinder bore by rotating and axially moving the grindstone, the clarity is increased only in a necessary portion, so that the oil consumption and the initial scuffing property are improved. The purpose is to balance productivity.

[0010]

In order to achieve the above-mentioned object, according to the present invention, a honing head for supporting a grindstone pressed against an inner surface of a cylinder bore, which is a workpiece, with a predetermined working pressure is first provided. In the honing method for performing grinding on the inner surface of the cylinder bore while rotating around the central axis of the cylinder and moving in the axial direction, the honing is performed on the inner surface of the cylinder bore where the piston ring slides near the piston top dead center. This is a honing method that reduces the rotational speed and axial speed of the head.

Secondly, the grindstone pressed against the inner surface of the cylinder bore with a predetermined processing pressure rotates and moves axially around the central axis of the cylinder bore, whereby two kinds of helical grindstones having different inclination directions are formed on the inner surface of the cylinder bore. In a cylinder bore having a crosshatch formed by intersecting loci, the crosshatch is made clear on the inner surface of the cylinder bore where the piston ring slides near the top dead center of the piston. Here, the clarification of the crosshatch means that the inclination angle of the crosshatch and the thickness of the processing locus are uniform.

[0012]

According to the first honing method or the second cylinder bore, the rotational speed and the axial direction of the honing head supporting the grindstone are machined when machining the inner surface of the cylinder bore where the piston ring slides near the piston top dead center. The crosshatch formed on the inner surface of the cylinder bore where the piston ring slides in the vicinity of the piston top dead center by reducing the speed stabilizes the movement.
The inclination angle and the thickness of the processing locus become uniform and are clarified.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic overall configuration diagram of a honing machine showing an embodiment of the present invention. This figure is
The state where the honing head 3 is inserted into the processing hole 1a forming the cylinder bore 1 of the engine which is the workpiece is shown. The honing head 3 includes a main body 5, two taper cones 7 that are vertically inserted into a central hole 5a of the main body 5, and downward movement of the taper cone 7 pushes the honing heads 3 toward the inner surface of the machining hole 1a and arranges a plurality of them in the circumferential direction. The shoe 9 and a grindstone 11 which is attached to the outer peripheral surface of the shoe 9 and which grinds the inner surface of the processing hole 1 and has a rectangular parallelepiped shape that is long in the vertical direction in the drawing.

The taper cone 7 is formed with an inclined surface 7a facing downward so that the diameter of the lower side is small, and on the shoe 9, an inclined surface 9a facing upward is formed so as to come into contact with the inclined surface 7a. There is.

A cylindrical portion 7b is formed on the inclined surface 7a of the tapered cone 7, and the outer peripheral surface of the cylindrical portion 7b is in sliding contact with the central hole 5a of the main body 5. The taper cone 7 is
The central shaft 13 is supported, and the upper end of the central shaft 13 is connected to a piston 17 of an expansion pressure cylinder 15 hydraulically driven.

The shoe 9 is disposed in a vertically long groove formed in the main body 5, and when the taper cone 7 descends, the shoe 9 moves outward in the radial direction of the central shaft 13 to process the grindstone 11. It is pressed with a predetermined pressing pressure, that is, expansion pressure, toward the inner surface of the hole 1a.

A rod 19 is provided on the upper surface of the expansion pressure cylinder 15.
Is connected, a rotary motor 23 is connected in the middle of the rod 19 via a power transmission mechanism 21 such as a gear, and the upper end of the rod 19 is connected to a piston 27 of a hydraulically driven vertical moving cylinder 25. . Rod 19
The lower rod 19a and the upper rod 19b are rotatably connected to each other by a connecting portion 29 above the power transmission mechanism 21. The honing head 3 is a rotary motor 2
3 by driving the lower rod 19a and the expansion pressure cylinder 1
While rotating via 5, the vertical movement cylinder 25 is driven to move up and down via the rod 19 and the expansion pressure cylinder 15, and in the course of these operations, the inner surface of the processing hole 1a is ground and the grinding locus of the grindstone 11 is ground. As a result, the cross hatch as shown in FIG. 5 is formed.

The rotary motor 23 is drive-controlled by a control circuit 31 including a microcomputer, and the vertical moving cylinder 25 is drive-controlled by the control circuit 31 via a hydraulic mechanism 33 including a hydraulic pump and an electromagnetic control valve. .

At the rising end position and the descending end position of the honing head 3, a proximity switch provided by detecting a detected portion 35 provided on the upper rod 19b above the connecting portion 29 and being fixed to a honing machine body (not shown). The control circuit 31, which is respectively detected by 37 and 39 and receives these detection signals, controls the hydraulic mechanism 33 to cause the hoisting head 3 to perform a predetermined vertical reciprocating motion by the vertical moving cylinder 25 to form the cylinder bore 1. The entire inner surface of the processed hole 1a is ground.

Below the proximity switch 37 for detecting the rising end position of the honing head 3, a proximity switch 41 for detecting the detected portion 35 is fixed to the main body of the honing machine like the other proximity switches 37 and 39. Has been. The proximity switch 41 detects a state in which the honing head 3 is located below the rising end position by a predetermined length α, and this length α is, as shown in FIG. It corresponds to the dimension from the upper end to the portion where the piston ring 45 slides near the top dead center of the piston 43.

The inner surface of the cylinder bore 1 at length α is
In the range of the length β from the upper end of the cylinder bore 1, the piston ring 4 is moved in the process of the piston 43 moving up and down.
5 is an unsliding portion of the piston ring that does not contact, and forms an inner wall surface of the combustion chamber together with the inner surface 47a on the cylinder head 47 side. Therefore, the region of the size corresponding to α-β is the portion where the piston ring 45 slides near the piston top dead center.

Then, the control circuit 31 uses the proximity switch 4
1 detects the detected portion 35 in the ascending process of the honing head 3, reduces the rotation speed and the vertical movement speed of the honing head 3, and detects the detected portion 35 in the descending process of the honing head 3, The hydraulic mechanism 33 is controlled so that the rotation speed and the vertical movement speed of the head 3 are returned to the original speed. In other words, the machining over the range of the length α from the upper end of the cylinder bore 1 is performed by lowering the rotation speed and the vertical movement speed of the honing head 3.

For example, the total length of the cylinder bore 1 is 120 m.
In the case of α = 20 mm and β = 5 mm in FIG.
Also, as shown in FIG. 4, the rotational speed and the vertical movement speed of the honing head 3 are 100 m from the lower end of the cylinder bore 1.
60 m / min and 2 respectively in the area up to the position of m
5 m / min, and from this position to the upper end of the cylinder bore 1 including the region where the piston ring 45 slides near the top dead center, 38 m / min and 16 m / min, respectively.
And

As described above, the honing head 3 is rotated and moved up and down in a stable state by performing the processing over the range of the length α from the upper end of the cylinder bore 1 while lowering the rotation speed and the vertical movement speed of the honing head 3. The crosshatch that moves and is formed in this region has a uniform inclination angle and thickness as shown in FIG. 6 and becomes clear.

The range of the length α from the upper end of the cylinder bore 1 includes a portion where the piston ring 45 slides in the vicinity of the piston top dead center. The piston ring 45 and the inner surface of the cylinder bore 1 are easily brought into metal contact with each other under the condition that the oil film is easily broken. When the crosshatch is made clear on the inner surface of the cylinder bore 1 under such conditions, the holding power of oil is increased, the oil consumption is improved, and the initial scuffing property is also improved.

On the other hand, in the portion other than the above, that is, in the region from the lower end of the cylinder bore 1 to the position of 100 mm, compared to the portion where the piston ring 45 near the piston top dead center slides, it is less affected by heat and the oil film is also formed. Since it is difficult to cut, it is not necessary to clarify the cross hatch, and it may be unclear as shown in FIG. 7. Therefore, the rotational speed and the vertical movement speed of the honing head 3 remain high and the stability of the movement is not increased, whereby the processing time for this portion can be shortened.

As described above, the crosshatch is made clear by reducing the rotational speed and the vertical movement speed of the honing head 3 only in a necessary portion on the inner surface of the cylinder bore 1, whereby the oil consumption and the initial scuffing property are improved. Since the crosshatch does not need to be made clear for other parts and is processed at normal rotation speed and vertical movement speed, the overall processing time is shortened,
Productivity improvements will be achieved at the same time.

In the above embodiment, the length α from the upper end of the cylinder bore 1 is set to 20 mm to clarify the cross hatch in this region, but at least α = 15 mm.
As a result, the cross hatch in this area may be made clear.

[0030]

As described above, according to the present invention, when machining the inner surface of the cylinder bore where the piston ring slides in the vicinity of the top dead center of the piston, the honing head that supports the grindstone rotates and moves vertically. Since it was done at a reduced speed, the crosshatch formed in this part was clarified, which can improve the oil consumption and the initial scuffing property, and the crosshatch is unclear in other parts. Since the processing is often performed at a normal speed, the total processing time is shortened and the productivity can be improved at the same time.

[Brief description of drawings]

FIG. 1 is a schematic overall configuration diagram of a honing apparatus showing an embodiment of the present invention.

2 is an explanatory diagram showing the relationship between the vertical position of a cylinder bore whose inner surface is ground by the honing device of FIG. 1 and the clarity of a cross hatch corresponding to this position.

FIG. 3 is an explanatory diagram showing a rotation speed of a honing head corresponding to vertical positions of a cylinder bore in the honing device of FIG. 1.

4 is an explanatory diagram showing vertical movement speeds of a honing head corresponding to vertical positions of cylinder bores in the honing device of FIG. 1. FIG.

FIG. 5 is a schematic view of a general cross hatch.

6 is a detailed view of a clarified crosshatch formed on the inner surface of the cylinder bore by the honing device of FIG. 1. FIG.

7 is a detailed view of an unclear cross hatch formed on the inner surface of the cylinder bore by the honing device of FIG. 1. FIG.

FIG. 8 is an explanatory diagram showing the relationship between the clarity of crosshatch, oil consumption, and initial scuffing property.

FIG. 9 is an explanatory diagram showing the relationship between the clarity of cross hatch and productivity.

[Explanation of symbols]

 1 Cylinder Bore (Workpiece) 1a Machining Hole 3 Honing Head 11 Grindstone 43 Piston 45 Piston Ring

Claims (2)

[Claims] 1. A honing head, which supports a grindstone pressed against an inner surface of a cylinder bore, which is a workpiece, with a predetermined processing pressure, grinds the inner surface of the cylinder bore while rotating and axially moving about a central axis of the cylinder bore. In the honing method for performing the machining, the rotational speed and the axial speed of the honing head are lowered when machining the inner surface of the cylinder bore where the piston ring slides near the top dead center of the piston. 2. A locus of two kinds of helical grindstones having different inclination directions on the inner surface of the cylinder bore by rotating and axially moving the grindstone pressed against the inner surface of the cylinder bore with a predetermined processing pressure. In a cylinder bore having a cross hatch formed by intersecting with each other, the cross hatch is clarified on the inner surface of the cylinder bore where the piston ring slides near the piston top dead center.