JPS6160818A - Method for hardening cylinder block in water-cooled internal-combustion engine with laser - Google Patents

Abstract

PURPOSE:To prevent reduction in the durability of an irradiating tube due to damage or the like by circulating a fluid for cooling such as water or air through a water jacket in a cylinder block. CONSTITUTION:Laser light 8 is irradiated on the surface of the bore 2 of a cast cylinder block 1 having a water jacket 3 for cooling an engine through an irradiating tube 12 which is moved back and forth in the bore 2 to carry out laser hardening. At this time, a fluid for cooling such as water or air is circulated through the water jacket 3 in the cylinder block 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for forming a hardened portion using a laser beam on a bore surface of a cylinder block in a water-cooled internal combustion engine.

[Conventional technology]

The present inventor previously proposed in Japanese Patent Application No. 59-128148 to form a laser hardened portion on the bore surface of a flaky graphite cast iron cylinder block of an internal combustion engine by moving a laser beam.

According to this, on the bore surface of the cylinder block made of flaky graphite cast iron, it is possible to form laser-hardened portions in the form of linear lines at an appropriate area ratio and at appropriate intervals in the area of the sliding surface with the piston ring. The laser-hardened bore surface layer has a mixed structure of cast iron such as hard martensite and loose flake graphite, which improves wear resistance and lubricity against contact with piston rings. .

By the way, in a laser hardening device for this purpose, the laser beam irradiation cylinder part is placed facing the inner diameter part of the bore of the cylinder block so as to substantially coincide with the cylinder axis, and the irradiation cylinder part is rotatable around the cylinder axis and the axis is If the inner peripheral surface of the bore is irradiated with a laser beam from a window opened on one side of the irradiation cylinder part, the laser beam irradiation cylinder part moves around the cylinder axis. By the combination of rotation and movement along the axis, it is possible to form laser-hardened portions in various patterns on the bore surface, such as an annular five-arc shape, a spiral shape, or a longitudinal linear shape along the cylindrical axis. .

[Problem that the invention seeks to solve]

In this case, if a laser beam is irradiated from the inner diameter part of the cylinder block bore at an appropriate moving speed, the cylinder block bore surface will be locally heated by the energy of the laser beam, and after the laser beam has passed, the heated portion will be spread around the surrounding area. However, even if local heating is caused by laser beam irradiation, radiant heat radiates from the high-temperature area until the bore surface is cooled down, and this radiant heat is transferred to the bore. Lasers remain trapped inside and are difficult to release to the outside, and the radiated heat heats the irradiation tube inserted into the cylindrical hole, causing thermal distortion and stress and damaging it. There are problems in that the durability of the hardening device is impaired, and the thermal distortion causes the position of the focusing lens for laser beam irradiation to be misaligned, making it impossible to achieve a predetermined hardness or width of the laser hardened portion.

The present invention seeks to solve this problem.

[Means for solving problems]

That is, in the present invention, a laser beam is moved and irradiated from a laser beam irradiation cylinder inserted into the inner diameter of the bore onto the bore surface of a cylinder block that has been cast so as to form a water jacket for cooling the engine in advance. When performing laser hardening, a method is adopted in which a cooling fluid such as water or air is passed through a water jacket in the cylinder block.

[Effect]

Normally, the cylinder block of a water-cooled internal combustion engine has a water jacket formed around the outer periphery of the bore in order to cool the cylinder block during operation of the internal combustion engine. If laser hardening is performed while a cooling fluid such as water or air is flowing through the bore, even if the circumferential surface of the bore is heated by irradiation with the laser beam, the material of the cylinder block on the outer periphery will not be used for cooling. Since the temperature is forcibly maintained at a low temperature by the fluid, heat conduction from the heated portion is good, and the locally heated portion is rapidly cooled.

Therefore, the generation of radiant heat itself can be suppressed,
This makes it possible to suppress the temperature rise in the laser beam irradiation barrel and its interior, thereby reducing deformation and damage to that part.

〔Example〕

Next, an embodiment of the present invention will be described. In the figure, 1 is a cylinder block made of flake graphite cast iron, 2 is a bore thereof, and 3 is a water jacket formed to be recessed on the outside of the bore 2. It is formed when the block 1 is cast. 4 and 5 are openings that communicate from the cooling water passage 3 to the upper surface of the cylinder block 1, and the opening 4.5 communicates with the cooling water passage of a cylinder head (not shown) that covers the upper surface of the cylinder block 1. It is configured.

Reference numeral 6 denotes a laser hardening device for laser hardening the surface of the bore 2, and the device 6 reflects the laser beam 8 emitted from the laser emitting head 7 such as the GO2 laser emitting head door.
9, 10, consists of an irradiation cylinder part 12 that guides the outside through a condensing lens 11 etc., the irradiation cylinder part 12 faces the inner diameter part of the bore 2 of the cylinder block, and the laser beam 8 from the laser transmitting hand door is irradiated. It is configured so that it can irradiate outward from the window 13 of the cylindrical portion 12. Alternatively, the laser hardening device 6 may be configured to be rotatable around the cylindrical axis 14 of the cylinder block bore 2 and can be moved up and down, or the cylinder block 1 placed on a table (not shown) may be moved around the cylindrical axis 14 of the bore. By adjusting these rotational speeds and vertical movement speeds, the laser beam 8 creates a laser hardening pattern of appropriately narrow stripes on the surface of the bore 2 in a circular manner. It is possible to change various shapes such as arc shape, circular shape, spiral shape, etc., and the irradiation movement speed at that time can be changed by UIi.
Configure it so that it can be divided into sections.

Furthermore, the condenser lens 1 in the laser hardening device 6
1, the spot diameter of the laser beam 8 on the surface of the bore 2 can be adjusted in size, and depending on the size of the spot diameter and the slow irradiation movement speed of the laser beam 8, the laser beam on the surface of the bore 2 can be adjusted. It is possible to adjust the hardening width in a direction substantially perpendicular to the moving direction of the light beam 8 and the hardening depth.

Then, the irradiation cylinder part 12 is made to face the inner diameter part of the bore 2,
During laser hardening by moving and irradiating the laser beam 5 while rotating and descending or ascending, water, oil, or air at a low temperature such as room temperature is introduced into the water jacket 3 in the cylinder block 1 from one opening 4. Bore 2 with constant flow
After forcibly cooling the outside, it is discharged from the other opening 5.

As a result, a temperature gradient is created that decreases from the heated surface of the bore 2 toward the water jacket 3, and the heat from the high-temperature area is removed extremely quickly and radiated from there (reducing the energy of the radiation heat itself). It can be suppressed as follows.

Therefore, less heat is trapped in the inner diameter portion of the bore 2, and the temperature rise of the laser beam irradiation tube portion 12 therein is also extremely reduced.

In this case, if air is used as the cooling fluid flowing into the water jacket 3, there is no need for recovery equipment like in the case of water when releasing this air to the outside of the cylinder block. There is no risk of getting the equipment wet and causing rust.

(Effects of the Invention) In summary, according to the present invention, the area around the bore of the cylinder block is forcibly cooled by using the water jacket that is usually formed in advance on the cylinder block itself of a water-cooled internal combustion engine. The part heated as a result of laser beam irradiation is cooled extremely quickly, and heat is not trapped in the inner diameter of the bore, thus preventing the temperature of the irradiation cylinder itself and its interior from increasing. , thermal distortion in the irradiation cylinder part in the laser hardening device, the mirror 5 condensing lens itself, or their supporting members.

This has the effect of eliminating the occurrence of thermal stress, preventing errors in spot diameter due to errors in setting the focal length of the laser beam, and preventing deterioration in durability due to damage to the irradiation barrel.

[Brief explanation of drawings]

The drawing is a schematic cross-sectional view of a laser hardening device and a cylinder block in an embodiment of the present invention. Engineering...Cylinder block, 2...Bore, 3...
... Water jacket, 4.5 ... Opening, 6. Group laser hardening device, 7. ... Laser beam transmission head, 8.
...Laser beam, 9.10...Reflector, 11...
- Condensing lens, 12... Irradiation cylinder section, 14... Cylinder axis line.

Claims (1)

[Claims] (1) Laser hardening is performed by irradiating a moving laser beam from a laser beam irradiation cylinder inserted into the inner diameter of the bore onto the bore surface of the cylinder block, which has been cast to form a water jacket for cooling the engine in advance. A method for laser hardening a cylinder block in a water-cooled internal combustion engine, characterized in that a cooling fluid such as water or air is passed through a water jacket in the cylinder block.