JPH0775959A - Honing method and cylinder bore - Google Patents

Abstract

PURPOSE:To improve the oil consumption, seizure and the initial scuffing of a piston. CONSTITUTION:The inclination of cross hatches, formed on the inner surface of a cylinder bore 1 by the locus of a honing wheel at the time of the honing wheel moving vertically while rotating, in relation to the face orthogonal to the center axis of a cylinder bore 1 is set to approximately 30 deg. so as to be easy in an area of length alpha. from the upper end of the cylinder bore 1, where a piston ring does not slide, and set to 45 deg. in the sliding area of the piston ring 45.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention applies a predetermined working pressure to the inner surface of a cylinder bore of an engine, which is a workpiece, while rotating and axially moving a honing head to which the whetstone is attached. The present invention relates to a honing method for grinding the inner surface of a cylinder bore and a cylinder bore according to the 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 done by making the surface roughness of the part where the piston ring slides on the inner surface of the cylinder bore finer than the surface roughness of the part where the piston skirt slides, so that the oil holding force will not increase in the part where the piston ring slides. This is effective in reducing friction loss, fuel consumption, and oil consumption. On the other hand, in the area 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 as shown in FIG. A crosshatch peculiar to honing processing will be formed.
This crosshatch has different inclination directions on the inner surface of the machined hole.
The helical grinding traces a and b of a kind are formed by intersecting each other, and serve as an oil pit for holding and spreading oil on the inner surface of the cylinder bore of the engine.

In terms of oil consumption, such a cross hatch has a smaller inclination angle R with respect to the horizontal plane, that is, grinding marks a, when the cylinder bore center axis is the vertical direction.
It is effective that b is closer to horizontal because oil is easily retained. FIG. 5 shows the relationship between the crosshatch inclination angle and oil consumption. According to this, it can be seen that the oil consumption is small when the inclination angle is about 30 degrees.
On the other hand, in terms of seizure property and initial scuffing of the piston, it is effective that the inclination angle is large, that is, the grinding marks a and b are close to the vertical direction which is the sliding direction of the piston. Figure 6
Shows the relationship between the crosshatch inclination angle and the initial scuffing performance. According to this, it is understood that the initial scuffing property is good when the inclination angle is about 45 degrees or more.

[0006]

As described above, the oil consumption property, the seizure property, and the piston initial scuffing property are contradictory to each other depending on the inclination angle of the crosshatch. Therefore, in the past, in order to satisfy both the oil consumption, seizure property, and initial scuffing property of the piston to some extent, the honing head rotation speed and vertical movement were adjusted so that the crosshatch inclination angle became an intermediate value between them. The speed and are set. Therefore, the individual performances of oil consumption, seizure, and initial scuffing of the piston are not sufficient, and there is room for improvement.

On the other hand, regarding the cylinder bore described in the above-mentioned conventional publication, the crosshatch is not taken into consideration, and actually, the piston ring slides on the inner surface of the cylinder bore above the piston ring at the top dead center of the piston. Since there is a part that does not move and forms the wall surface of the combustion chamber, when oil flows into the combustion chamber side through the gap between the piston ring and the inner surface of the cylinder bore, it burns and increases oil consumption. Therefore, as in the case of the above publication, it is not sufficient in terms of oil consumption to consider the surface roughness only of the sliding portions of the piston ring and the piston skirt.

Therefore, an object of the present invention is to further improve both the oil consumption property, the seizure property and the piston initial scuffing property.

[0009]

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 that grinds the inner surface of the cylinder bore while rotating and moving axially about the center axis of the piston, the inner surface of the cylinder bore where the piston ring above the piston ring at the piston top dead center does not slide is Rather than machining the inner surface of the cylinder bore where the piston ring below the piston ring at top dead center slides,
The honing method is performed by reducing the ratio of the axial moving speed to the rotating speed of the honing head.

Secondly, the grindstone pressed against the inner surface of the cylinder bore with a predetermined processing pressure rotates and moves in the axial direction around the center axis of the cylinder bore, so that the inner surface of the cylinder bore has two kinds of helical grindstones having different inclination directions. In a cylinder bore having a crosshatch formed by trajectories intersecting each other, an inclination angle with respect to a plane orthogonal to the cylinder bore center axis of the crosshatch at the cylinder bore inner surface where the piston ring above the piston ring at the piston top dead center does not slide, The cylinder bore is smaller than the same inclination angle of the cross hatch on the inner surface of the cylinder bore where the piston ring below the piston ring slides at the piston top dead center.

Thirdly, in the second cylinder bore, the inclination angle of the crosshatch at the cylinder bore inner surface where the piston ring above the piston ring at the piston top dead center does not slide with respect to the plane orthogonal to the cylinder bore center axis is about 45 degrees. The cross hatch has the same inclination angle of about 30 degrees on the inner surface of the cylinder bore where the piston ring below the piston ring slides at the top dead center of the piston.

[0012]

According to the honing method and the cylinder bore as described above, the inner surface of the cylinder bore of the piston ring non-sliding portion above the piston ring at the top dead center of the piston is higher than the inner surface of the cylinder bore of the sliding portion of the piston ring. By performing honing with the head having a small ratio of the axial movement speed to the rotation speed, the crosshatch formed on the inner surface of the cylinder bore is
The tilt angle with respect to the plane orthogonal to the center axis of the cylinder bore is
The non-sliding part of the piston ring is smaller than the sliding part of the piston ring. This allows the oil to flow into the combustion chamber through the gap between the piston ring and the inner surface of the cylinder bore.
The grinding marks forming the cross hatch in the non-sliding portion of the piston ring are less likely to occur because the inclination angle is such that the oil does not flow in, and the oil consumption is reduced.
On the contrary, the same inclination angle of the cross hatch on the inner surface of the cylinder bore of the sliding portion of the piston ring is larger than the inclination angle of the cross hatch of the non sliding portion of the piston ring, and the grinding marks forming the cross hatch are relatively offset in the moving direction of the piston. Therefore, the seizure property and the initial scuffing property when the piston slides are improved.

[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 machined hole 1a forming the cylinder bore 1 of the engine 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. Shoe 9 and shoe 9
And a grindstone 11 in the shape of a rectangular parallelepiped which is attached to the outer peripheral surface of the machine and grinds the inner surface of the machined hole 1a.

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. Thus, the cross hatch as shown in FIG. 7 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 upper surface of the piston ring 45 at the top of the piston 43 at the top dead center position. That is, the inner surface of the cylinder bore 1 at this length α is a piston ring non-sliding portion with which the piston ring 45 does not come into contact in the process of the piston 43 moving up and down, and together with the inner surface 47a on the cylinder head 47 side, the inner wall surface of the combustion chamber. Form.

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, lowers 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 to return the vertical movement speed to the original speed.
That is, the piston ring non-sliding portion over the range of the length α from the upper end of the cylinder bore 1 is processed by slowing the vertical movement speed of the honing head 3.

For example, the total length of the cylinder bore 1 is 120 m.
m and α = 10 mm, as shown in FIG. 3, the vertical movement speed of the honing head 3 is 25 m / in a region including a portion where the piston ring 43 slides from the lower end of the cylinder bore 1 to a position of 110 mm. min, and the area of the piston ring non-sliding part from this position to the upper end is 16 m
/ Min. On the other hand, the rotation speed of the honing head 3 is constant at 60 m / min in the entire region from the lower end to the upper end of the cylinder bore 1 as shown in FIG.

The relationship between the constant rotational speed of the honing head 3 and the two vertical movement speeds as described above is shown in FIG. 2 (b).
As shown in FIG. 7, the inclination angle (corresponding to the inclination angle R in FIG. 7) of the crosshatch with respect to the plane orthogonal to the cylinder bore center axis in the region including the portion where the piston ring 45 slides from the lower end of the cylinder bore 1 to 110 mm is 45. The angle of inclination of the cross hatch is approximately 30 degrees in the non-sliding portion where the piston ring 45 does not slide up to 10 mm from the upper end of the cylinder bore 1.

Since the crosshatch in the non-sliding part of the piston is set to 30 degrees to make the inclination relatively gentle, the inflow of oil from the gap between the piston ring 45 and the cylinder bore 1 to the combustion chamber side causes the inclination of the crosshatch. It is less likely to occur depending on the angle, and oil consumption is reduced. On the contrary, the same inclination angle of the cross hatch below the non-sliding part of the piston ring is larger than the inclination angle of the cross hatch of the non-sliding part of the piston ring, and the grinding marks forming the cross hatch are relatively offset in the moving direction of the piston 43. Therefore, the seizure property and the initial scuffing property when the piston 43 slides are improved.

In the above embodiment, the honing head 3 is rotated at a constant speed and the vertical movement speed is reduced in the region of the length α from the upper end. However, the vertical movement speed of the honing head 3 is kept constant. In such a state, by increasing the rotation speed in the region of length α from the upper end, the inclination angle of the crosshatch in the region of length α from the upper end can be made gentle. However, if you lower the vertical movement speed,
It is preferable because the cross hatch becomes clear.

[0027]

As described above, according to the present invention, the crosshatch formed on the inner surface of the cylinder bore is
The tilt angle with respect to the plane orthogonal to the center axis of the cylinder bore is
Since the non-sliding part of the piston ring is smaller than the sliding part of the piston ring, the inflow of oil from the gap between the piston ring and the cylinder bore to the combustion chamber side is less likely to occur due to the inclination angle of the crosshatch. ,
Oil consumption can be reduced. On the contrary, the same inclination angle of the cross hatch on the inner surface of the cylinder bore of the sliding portion of the piston ring is larger than the inclination angle of the cross hatch of the non sliding portion of the piston ring, and the grinding marks forming the cross hatch are relatively offset in the moving direction of the piston. Therefore, the seizure property and the initial scuffing property when the piston slides can be improved.

[Brief description of drawings]

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

2 shows a relationship between a piston ring non-sliding part and a part including a sliding part in a cylinder bore whose inner surface is ground by the honing device of FIG. 1 and a cross hatch inclination angle corresponding to each of these parts. It is an explanatory view shown.

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

FIG. 4 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.

FIG. 5 is an explanatory diagram showing a relationship between an inclination angle of a cross hatch and oil consumption.

FIG. 6 is an explanatory diagram showing a relationship between an inclination angle of a cross hatch and an initial scuff.

FIG. 7 is an explanatory diagram of a general cross hatch.

[Explanation of symbols]

 1 Cylinder Bore 1a Machining Hole (Inner Surface) 3 Honing Head 11 Grinding Stone 43 Piston 45 Piston Ring

Claims (3)

[Claims] 1. A honing head, which supports a grindstone pressed against the inner surface of a cylinder bore, which is a workpiece, with a predetermined working pressure, grinds the inner surface of the cylinder bore while rotating and axially moving around the central axis of the cylinder bore. In the honing method that performs the above, the machining on the cylinder bore inner surface where the piston ring above the piston ring at the piston top dead center does not slide is performed more than the machining on the cylinder bore inner surface where the piston ring below the piston ring at the piston top dead center slides. Also, the honing processing method is performed by reducing the ratio of the axial movement speed to the rotation speed of the honing head. 2. A locus of two types 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, the tilt angle of the cross hatch on the inner surface of the cylinder bore where the piston ring above the piston ring at the top dead center of the piston does not slide with respect to the plane orthogonal to the cylinder bore center axis is A cylinder bore characterized in that it is smaller than the same inclination angle of the cross hatch on the inner surface of the cylinder bore where the piston ring below the piston ring at the dead point slides. 3. The piston at top dead center of the piston has an inclination angle of about 45 degrees with respect to a plane orthogonal to the center axis of the cylinder bore of the crosshatch on the inner surface of the cylinder bore where the piston ring above the piston ring does not slide at top dead center of the piston. 3. The cylinder bore according to claim 2, wherein the cross hatch has the same inclination angle of about 30 degrees on the inner surface of the cylinder bore where the piston ring below the ring slides.