JP3042275B2 - Honing method and cylinder bore - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a honing head to which a grindstone is mounted, while applying a predetermined working pressure to an inner surface of a cylinder bore of an engine, which is a workpiece, while rotating and axially moving the grindstone. The present invention relates to a honing method for grinding an inner surface of a cylinder bore and a cylinder bore formed by the method.

[0002]

2. Description of the Related Art Honing is generally used for precision finishing of the inner surface of a cylinder bore of an engine. In the honing process, the inner surface of a processing hole is ground using a grindstone, and the whetstone is usually a rectangular parallelepiped and is arranged at a plurality of equal intervals in a circumferential direction with a central axis direction of the processing hole as a longitudinal direction. The plurality of whetstones are inserted into the processing hole and pressed against the inner surface of the processing hole by a tool called a horn arranged radially with respect to the center axis thereof, and are processed by rotating and reciprocating in the axial direction. The inner surface of the hole is processed smoothly and accurately.

[0003] An example of an inner surface of a cylinder bore that has been honed is described in Japanese Utility Model Laid-Open No. 58-2343. This is because the surface roughness of the part where the piston ring slides on the inner surface of the cylinder bore is made smaller than the surface roughness of the part where the piston skirt slides, so that the oil retaining force is reduced at the part where the piston ring slides. When secured, it 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 increased, which is effective in seizure resistance.

By the way, a grinding stone used for honing is usually made of abrasive grains such as diamond.
Since the honing head on which the grinding wheel is mounted is rotated and moved up and down by the rotary motor and the vertical moving cylinder, the trajectory of the abrasive grains becomes helical, and the inner surface of the processing hole where the honing head moves is as shown in FIG. A cross hatch peculiar to the honing process is formed.
This cross hatch has a different inclination direction on the inner surface of the processing hole.
The helical grinding traces a and b are formed to intersect with each other, and serve as an oil pit that assists oil retention and spreading on the inner surface of the cylinder bore of the engine.

In such a cross hatch, in terms of oil consumption, the smaller the inclination angle R with respect to the horizontal plane, that is, the grinding marks a and
It is more effective for b to be close to horizontal because the oil can be easily held. FIG. 5 shows the relationship between the inclination angle of the cross hatch and oil consumption. According to this, it is understood that oil consumption is small when the inclination angle is about 30 degrees.
On the other hand, in terms of the seizure and the initial scuff of the piston, it is more effective that the inclination angle is larger, that is, the grinding marks a and b are closer to the vertical direction in which the piston slides. FIG.
Shows the relationship between the inclination angle of the cross hatch and the initial scuff 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, the seizure and the initial scuffing of the piston are contradictory depending on the inclination angle of the cross hatch. For this reason, in the past, in order to satisfy both oil consumption, seizure and piston initial scuffing to some extent, the rotation speed of the honing head and the vertical movement were adjusted so that the inclination angle of the cross hatch was an intermediate value between the two. Set the speed and. For this reason, 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 cross hatch is not considered, and the piston ring slides on the inner surface of the cylinder bore above the piston ring at the piston top dead center. Since there is a portion that does not move and forms a combustion chamber wall surface, if oil flows into the combustion chamber through a gap between the piston ring and the inner surface of the cylinder bore, it burns and increases oil consumption. For this reason, it is not sufficient in terms of oil consumption to consider only the surface roughness of each sliding portion of the piston ring and the piston skirt as in the above publication.

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

[0009]

In order to achieve the above object, the present invention firstly provides a honing head for supporting a grindstone pressed with a predetermined working pressure against an inner surface of a cylinder bore as a workpiece by a cylinder bore. In the honing method for performing grinding on the inner surface of the cylinder bore while rotating and moving in the axial direction about the center axis of the piston, the processing 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 is performed by the piston. Rather than machining the inner surface of the cylinder bore where the piston ring below the piston ring at top dead center slides,
This is a honing method in which the ratio of the axial movement speed to the rotation speed of the honing head is reduced.

Second, two types of helical grindstones having different inclination directions are formed 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 around the center axis of the cylinder bore. In a cylinder bore having a cross hatch formed by intersecting trajectories, the inclination angle with respect to a plane perpendicular to the cylinder bore center axis of the cross hatch on the inner surface of the cylinder bore where the piston ring above the piston ring at the piston top dead center does not slide 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 in which the piston ring below the piston ring at the piston top dead center slides.

Third, in the second cylinder bore, the inclination 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 perpendicular to the cylinder bore center axis is about 30 degrees. The inclination angle of the cross hatch on the inner surface of the cylinder bore in which the piston ring slides below the piston ring at the piston top dead center is about 45 degrees.

[0012]

According to the honing method and the cylinder bore described above, the inner surface of the cylinder bore in the non-sliding portion of the piston ring above the piston ring at the top dead center of the piston is smaller than the inner surface of the cylinder bore in the sliding portion of the piston ring. By performing honing with the ratio of the axial movement speed to the rotation speed of the head being small, the cross hatch formed on the inner surface of the cylinder bore is
The inclination angle with respect to the plane orthogonal to the cylinder bore center axis is
The non-sliding portion of the piston ring is smaller than the sliding portion of the piston ring. As a result, oil flows into the combustion chamber from the gap between the piston ring and the inner surface of the cylinder bore,
Since the grinding marks forming the cross hatch of the non-sliding portion of the piston ring have such an inclination angle as to hinder the inflow of oil, they are less likely to occur, and oil consumption is reduced.
Conversely, the same inclination angle of the cross hatch on the inner surface of the cylinder bore of the piston ring sliding part is larger than the inclination angle of the cross hatch on the non-sliding part of the piston ring, and the grinding mark that forms the cross hatch is compared with the movement direction of the piston Since it is close, seizure and initial scuffing at the time of piston sliding 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 apparatus showing an embodiment of the present invention. This figure is
The state where the honing head 3 is inserted into the processing hole 1a which forms the cylinder bore 1 of the engine is shown. The honing head 3 includes a main body 5, two tapered cones 7 that are vertically movably inserted into a center hole 5 a of the main body 5, and a plurality of circumferentially arranged pressing down toward the inner surface of the processing hole 1 a by descending the tapered cone 7. Shoe 9 and shoe 9
And a rectangular parallelepiped grinding wheel 11 which is attached to the outer peripheral surface of the workpiece and grinds the inner surface of the processing hole 1a.

The tapered cone 7 is formed with a downwardly inclined surface 7a so as to reduce the diameter on the lower side, while the shoe 9 is formed with an upwardly inclined surface 9a which comes into contact with the inclined surface 7a. I have.

A cylindrical portion 7b is formed above 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 center hole 5a of the main body 5. The taper cone 7 is
The center shaft 13 is supported, and the upper end of the center shaft 13 is connected to a piston 17 of a hydraulically driven expansion pressure cylinder 15.

The shoe 9 is disposed in a vertically long groove formed in the main body 5 and moves outward in the radial direction of the center shaft 13 as shown by an arrow A by machining the taper cone 7 to process the grindstone 11. It is pressed against the inner surface of the hole 1a with a predetermined pressing pressure, that is, an expanded pressure.

A rod 19 is provided on the upper surface of the expansion cylinder 15.
The rotation motor 23 is connected to 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 vertically driven cylinder 25 which is hydraulically driven. . The 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 drives the lower rod 19a and the expanded pressure cylinder 1
5, while moving through the rod 19 and the expansion pressure cylinder 15 by the driving of the vertical movement cylinder 25, the inner surface of the processing hole 1 a is ground in the course of these operations, As a result, a cross hatch as shown in FIG. 7 is formed.

The driving of the rotary motor 23 is controlled by a control circuit 31 composed of a microcomputer or the like, and the driving of the vertically moving cylinder 25 is controlled by the control circuit 31 via a hydraulic mechanism 33 composed of a hydraulic pump or an electromagnetic control valve. .

The rising end position and the falling end position of the honing head 3 are detected by a detected portion 35 provided on the upper rod 19b above the connecting portion 29, and a proximity switch fixedly provided on a honing board body (not shown). The control circuit 31, which is detected by the detection signals 37 and 39, respectively, and receives these detection signals, controls the hydraulic mechanism 33 to cause the vertical movement cylinder 25 to perform a predetermined vertical reciprocating movement of the honing head 3, thereby forming the cylinder bore 1. The entire inner surface of the processed hole 1a is ground.

Below the proximity switch 37 for detecting the raised end position of the honing head 3, a proximity switch 41 for detecting the detected portion 35 is fixedly provided on the honing board body like the other proximity switches 37 and 39. Have been. The proximity switch 41 detects a state in which the honing head 3 is located below the raised end position by a predetermined length α, and the 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 having the length α is a non-sliding portion of the piston ring in which the piston ring 45 does not contact in the process of moving the piston 43 up and down, and the inner wall surface of the combustion chamber together with the inner surface 47a on the cylinder head 47 side. Form.

The control circuit 31 includes the proximity switch 4
When the hoisting head 3 detects the detected portion 35 in the rising process of the honing head 3, the vertical movement speed of the honing head 3 is reduced. The hydraulic mechanism 33 is controlled to return the vertical movement speed to the original speed.
That is, the machining of the unslidable portion of the piston ring over the range of the length α from the upper end of the cylinder bore 1 is performed by lowering the vertical movement speed of the honing head 3.

For example, the total length of the cylinder bore 1 is 120 m
m, α = 10 mm, as shown in FIG. 3, the vertical movement speed of the honing head 3 is 25 m / m in an area including a portion where the piston ring 45 slides from the lower end of the cylinder bore 1 to a position of 110 mm. min, and the area of the piston ring unslidable portion from this position to the upper end is 16 m
/ Min. On the other hand, the rotation speed of the honing head 3 is set to a constant 60 m / min in the entire region from the lower end to the upper end of the cylinder bore 1 as shown in FIG.

FIG. 2B shows the relationship between the constant rotational speed of the honing head 3 and the two vertical moving speeds.
As shown in FIG. 7, the inclination angle (corresponding to the inclination angle R in FIG. 7) of the cross hatch with respect to the plane perpendicular 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. So that the inclination angle of the cross hatch in an unslidable portion where the piston ring 45 does not slide up to 10 mm from the upper end of the cylinder bore 1 becomes approximately 30 degrees.
Each is set.

Since the cross hatch in the non-sliding portion of the piston is set at a relatively gentle inclination with a cross hatch of 30 degrees, the inflow of oil from the gap between the piston ring 45 and the cylinder bore 1 to the combustion chamber side is caused by the inclination of the cross hatch. It is less likely to occur depending on the angle, and oil consumption is reduced. Conversely, the same inclination angle of the cross hatch below the non-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 compared with the moving direction of the piston 43. Because of the closeness, seizure and initial scuffing at the time of sliding of the piston 43 are improved.

In the above embodiment, the rotation speed of the honing head 3 is kept constant and the vertical movement speed in the region of the length α from the upper end is reduced, but the vertical movement speed of the honing head 3 is kept constant. In this state, the inclination angle of the cross hatch in the region having the length α from the upper end can be made gentler by increasing the rotation speed in the region having the length α from the upper end. However, lowering the vertical movement speed
This is preferable because the cross hatch becomes clear.

[0027]

As described above, according to the present invention, the cross hatch formed on the inner surface of the cylinder bore is:
The inclination angle with respect to the plane perpendicular to the cylinder bore center axis is
Since the non-sliding portion of the piston ring is made smaller than the sliding portion 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 cross hatch. ,
Oil consumption can be reduced. Conversely, the same inclination angle of the cross hatch on the inner surface of the cylinder bore of the piston ring sliding part is larger than the inclination angle of the cross hatch on the non-sliding part of the piston ring, and the grinding mark that forms the cross hatch is compared with the movement direction of the piston Because of the closeness, seizure and initial scuffing during sliding of the piston can be improved.

[Brief description of the drawings]

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

FIG. 2 shows a relationship between a non-sliding portion of a piston ring and a portion including a sliding portion in a cylinder bore whose inner surface is ground by the honing device of FIG. 1, and a tilt angle of a cross hatch corresponding to each of the portions. FIG.

FIG. 3 is an explanatory diagram showing a vertical movement speed of a honing head corresponding to a vertical position of a cylinder bore in the honing apparatus of FIG. 1;

FIG. 4 is an explanatory diagram showing a rotation speed of a honing head corresponding to a vertical position of a cylinder bore in the honing apparatus of FIG. 1;

FIG. 5 is an explanatory diagram showing a relationship between a tilt 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]

 DESCRIPTION OF SYMBOLS 1 Cylinder bore 1a Machining hole (inner surface) 3 Honing head 11 Grinding stone 43 Piston 45 Piston ring

Claims (3)

(57) [Claims] 1. A honing head for supporting 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 processing method, the processing on the inner surface of the cylinder bore in which the piston ring above the piston ring does not slide at the piston top dead center is compared with the processing on the inner surface of the cylinder bore in which the piston ring below the piston ring slides at the piston top dead center. A honing processing method wherein the ratio of the axial moving speed to the rotational speed of the honing head is reduced. 2. A trajectory 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 around the central axis of the cylinder bore. In the cylinder bore having a cross hatch formed by crossing, the inclination angle of the cross hatch relative to a plane perpendicular to the cylinder bore center axis on 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 determined by the piston. A cylinder bore characterized in that the cross hatch has a smaller inclination angle on the inner surface of the cylinder bore in which the piston ring slides below the piston ring at the top dead center. 3. The inclination angle of the cross hatch on the inner surface of the cylinder bore at which the piston ring above the piston ring does not slide at the piston top dead center with respect to the plane orthogonal to the cylinder bore center axis is about 30 degrees. 3. The cylinder bore according to claim 2, wherein the inclination angle of the cross hatch on the inner surface of the cylinder bore on which the piston ring slides below the ring is about 45 degrees.