GB2149058A

GB2149058A - Piston engine having a phosphatized cylinder wall

Info

Publication number: GB2149058A
Application number: GB08427169A
Authority: GB
Inventors: Richard Carl Fox
Original assignee: Teledyne Industries Inc
Current assignee: TDY Industries LLC
Priority date: 1983-11-02
Filing date: 1984-10-26
Publication date: 1985-06-05
Also published as: NZ210074A; CA1234730A; SE8405305D0; FR2554168B1; GB2149058B; GB8427169D0; IT1183728B; DE3439021A1; BR8405687A; SE8405305L; FR2554168A1; AU3487684A; JPS60221583A; IT8483631A0

Abstract

A method for constructing and breaking-in piston engines includes applying an integral phosphate layer 26 to the interior cylinder wall 28, prior to the insertion of the piston into a cylinder. Engines so constructed are particularly suited for use as aircraft engines. <IMAGE>

Description

SPECIFICATION Piston Engine having a Phosphatized Cylinder Wall Field of the invention.

The present invention is directed to piston engines, and more particularly, to aircraft engines having a rust-resistant cylinder wall with superior piston ring seatilg properties; Description of the prior art.

Piston engines, and in particular internal combustion engines, typically comprise a multiplicity of cylinder assemblies; These cylinder assemblies conventionally comprise at least one cylinder head and at least one steel cylinder attached to the head. Because the weight of the engine is a significant factor for the overall performance and efficiency of the engine, attempts are often made to reduce the overall weight of the engine; In aircraft engines, for example, the cylinder head or heads are often constructed of aluminium, or aluminium or other alloy.

For various reasons, steel remains the material of choice for the cylinder itself.

One problem with the steel cylinders conventionally used in aircraft engines is that the cylinders are susceptible to rust or rust-type corrosion of the cylinder bores, especially during storage or during the first few hours of operation of the engine. The problem is particularly acute when the engine is run briefly, for example, after assembly, and then allowed to sit idle for some period of time. If this corrosion is allowed to develop, pits may be formed in the cylinder barrel surface. This corrosion is sometimes severe enough adversely to affect piston ring wear and oil control.

There are, of course, several ways of inhibiting rust formation on a steel surface, but the nature of the cylinder assembly of aircraft engines renders these ways less than useful; Painting the cylinder walls may interfere with the sealing function of the piston rings, and can be abraded from the wall during the first few hours of operation. Provision of an oxide coating on the cylinder barrels may not be possible, because of the nature of typical aircraft engine manufactuing procedures. One of the first steps assembling an engine is to assemble the steel cylinder or cylinders to the aluminium cylinder head. The chemicals employed in creating an oxide layer on the barrel surface are often corrosive to aluminium, and their use is therefore prohibited.

The application of a layer of crystalline phosphate to a ferrous surface is known, for example, to a steel engine combustion chamber head, as in U.S. Patent No. 3,082,128 to Craig; Craig disclosed phosphatizing the combustion chamber head for the purpose of reducing carbon build-up in the head during operation of the engine. But no reference has been found in which the cylinder barrel, and in particular the cylinder wall, has been phosphatized; Moreover, as noted by Blum et al in U.S. Patent No. 3,297 493, at column 1, lines 28 through 33, phosphate-type coatings are usually characterized as being relatively fragile. A phosphorous coating on a cylinder wall could be expected to wear away during operation of the engine, under the abrasive friction of the piston rings, or could be expected adversely to affect piston ring wear.

The potential for interference with the sealing function of the piston rings could also be expected from such a coating.

Summary of the present invention.

The present invention aims to overcome these and other problems by providing an engine having a cylinder assembly which is rust-resistant and also has superior wear and sealing characteristics. The cylinder assembly comprises an aluminium cylinder head and a steel cylinder barrel attached thereto. The surface of at least the interior cylinder wall is converted to an integral layer of crystalline phosphate subsequent to the attachment of the cylinder barrel to the cylinder head; Thus, in accordance with one aspect of the present invention there is provided a piston engine comprising: at least one cylinder head; at least one steel cylinder attached to each of said at least one cylinder head, said at least one steel cylinder having an interior cylinder wall and a surface on said wall; a piston disposed in each of said at least one steel cylinder; and a piston ring disposed between said piston and said cylinder wall; wherein said cylinder wall bears an integral layer of crystalline phosphate on said surface.

The phrase 'integral layer of crystalline phosphate' means the layer existing on a ferrous cylinder wall surface subsequent to treatment by either the phosphatizing method described hereinafter, or any other phosphatizing method now known or hereafter discovered. The phosphatizing method employed in the present invention comprises: rendering the aluminium cylinder head inert to phosphatizing; attaching a steel cylinder to it; and applying a solution of water, zinc and phosphoric acid to the cylinder assembly so formed.

The process for constructing the engine includes attaching at least one steel cylinder to each of at least one cylinder head, applying a phosphatizing solution to the cylinder assembly so formed, and inserting a piston and its associated piston ring into each of said at least one cylinder. The process of breaking-in an engine includes the steps of constructing an engine, in accordance with the previously described steps, and then controlling the oper ation of the engine during its period of initial use.

The present invention also provides a process for manufacturing an engine in accordance with the invention, comprising the steps of: attaching at least one unphosphatized steel cylinder to one of said at least one aluminium cylinder head, thereby forming a cylinder assembly; honing the wall of said unphosphatized cylinder; and subsequently converting the surface of said wall to an integral layer of crystalline phosphate; The invention also includes within its scope a process for breaking-in an engine, comprising the steps of constructing said engine and controlling the operation of said engine during a period of initial use, wherein said constructing step includes insertion of a piston and an associated piston ring into a cylinder assembly of said engine, said cylinder assembly comprising at least one cylinder head and at least one steel cylinder assembled to each of said at least one cylinder head; characterised by the step of applying an integral phosphate layer to the surface of said cylinder subsequent to its assembly to said at least one cylinder head, but before insertion of said piston and said piston ring into said cylinder.

Brief description of the drawing.

A better understanding of the present invention will be had upon reference to the following detailed description, when read in conjunction with the accompanying drawing, in which the Figure is a partial cross-sectional block diagram of the preferred embodiment of the present invention.

Detailed description of the preferred embodiment of the present invention A piston engine 10 according to the present invention has at least one cylinder assembly 12, each of which comprises a cylinder head 14 having at least one steel cylinder 16 attached to it. Subsequent discussion of the engine and processes of the present invention will be restricted to the example of an aircraft engine comprising a multiplicity of cylinder assemblies, each assembly consisting of an aluminium cylinder head attached to a single steel cylinder. It should be clear that the utility of the present invention is not limited to this type of engine, however, but can be employed in an engine having one or more cylinder heads, each cylinder head having one or more cylinders attached to it.

One of the first steps in constructing an aircraft engine is the assembly of the steel cylinder 1 6 to the aluminium cylinder head 14. The cylinder assembly 1 2 so constructed is subject to subsequent manipulative steps, for example, the honing of a cylinder wall 18.

The interior diameter of the cylinder 1 6 is slightly larger than the diameter of a piston 20 to be inserted therein, during subsequent engine construction. The piston 20 bears at least one piston ring 22 thereon which is intended to operatively seal a combustion chamber 24 created by the cylinder wall 1 2, the cylinder head 14, and the piston 20.

The novel feature in the engine construction and processes of the present invention is the provision of an integral layer of crystalline phosphate 26 upon an inner steel cylinder wall surface or bore 28. This layer 26 is provided as follows: 1. The aluminium cylinder head 14 is separately rendered inert to phosphatizing, preferably by providing it with a chromate conversion coating as is known in the art. Alternatively, the head 14 can be rendered inert by anodizing or by another method.

2. The steel cylinder 1 6 is attached to the aluminium cylinder head 14 to form a cylinder assembly 12. This assembly is honed and washed subsequent to this attachment. Preferably, this washing comprises brush scrubbing the cylinder bore 28 using a detergent solution. Any detergent, soap or cleaning solution or fluid which does not corrode the cylinder assembly 1 2 and does not leave a residue thereon will be useful. The concentration of the cleaning solution or fluid should be sufficient to render the cylinder bore free of contaminants.Preferably, the detergent solution comprises two (2) ounces per gallon (15 grams per litre) of Ridoline No. 53 (a proprietary product of Amchem Products, Inc.), or equivalent, in water at about approximately 1 50'F (66 'C); 3. (a) If storage or transportation of the cylinder assemblies 1 2 is desired, the cylinder assemblies 1 2 can be preserved by the application of an oil thereto. Preferably, an oil conforming to Military Specification VV-L-800 is applied to the inside diameter of the cylinder bore 28, although other oils may be substituted.

(b) The preserving oil must be removed from the cylinder assembly 12 prior to subsequent treatment of the cylinder assemblies.

Any detergent, soap or dealing solution or fluid which does not corrode the cylinder assembly 1 2 and does not leave a residue thereon, and sufficiently removes the preserving oil so that the oil does not interfere with the phosphatizing steps, will be useful; The preferred preserving oil can be preferably removed by immersion of the cylinder assembly 1 2 for about five (5) minues in a solution comprising about four to six (4-6) ounces per gallon (30 to 45 grams per litre) of Ridoline No; 53, or an equivalent cleaner, at about 150"F to about 160'F(66'Cto 71'C) This or an equivalent cleaner can alternatively be applied by a multiple stage power cleaner or by some other means.

(c) Preferably, when a water based or water soluble cleaner is employed, the cylinder assembly 1 2 is thoroughly rinsed in cold water subsequent to the washing step.

4. The cleaned cylinder assembly 1 2 is then immersed in a phosphatizing solution for a sufficient period of time in order to produce a uniform gray-crystalline layer on the assembly. Preferably, the solution comprises at least one zinc salt in a phosphoric acid solution at a pH of about 2.8 to 3.0, which is maintained at a temperature of about 155 F to about 170 F (68'C to 77"C) The phosphatizing solution can also contain one or more accelerators, such as nickel or the like. A preferred concentrate for the phosphatizing solution is Turco 4333, a proprietary product of Turco Products, which is a division of Purex Corporation.A three (3%) per cent solution of Turco 4333 will be expected to provide a phosphate layer of about one thousand (1,000) milligrams per square foot (1.08 mg per square centimetre) of surface area, when the assembly is immersed for about five (5) to eight (8) minutes.

5. The cylinder assembly 1 2 is then rinsed in water, to terminate the phosphatizing of the cylinder bore 28. This rinse can be a hot water rinse at about 180"F (82"C), and the cylinder assembly 1 2 can then be air dried, if it is to be painted after phosphatizing. Preferably, however, the rinse is cold water rinse, and the cylinder 1 2 is oil-preserved as described below.

6. The cylinder assembly 1 2 can be oilpreserved by immersion into a solution of a water soluble oil at room temperature; Preferably, the water-soluble oil solution contains about ten (10%) per cent by volume of Turco 4454, a water-soluble oil which is a proprietary product of Turco Products, a division of Purex Corporation.

Alternatively, the cylinder assembly 1 2 can be preserved by the application of a waterdisplacing preservative oil.

The engine 10 according to the present invention incorporates the cylinder assembly 12 prepared in accordance with this procedure. This engine, when so constructed, exhibits unusual and unexpected properties. The integral layer of crystalline phosphate 28 is resistant to the abrasive wear from the piston ring 22, in contrast to the expectation that the relatively soft phosphate layer would be easily worn away. Instead, the phosphate crystals remain visible on inspection of the interior cylinder wall 18 after a substantial period of operation of the engine so constructed. The entire portion of the cylinder wall within the ring travel area typically exhibits a visible phosphate layer for at least about one hundred (100) hours of operation.After about two hundred (200) hours of engine operation, phosphate crystals will typically remain visible in valleys and grooves of the cross-hatch pattern within the ring travel area. Additionally, the engine constructed according to the present invention has superior oil consumption characteristics and improved piston ring seating during break-in because of this phosphate layer.

Another aspect of the present invention is an improvement in the methods of breaking-in engines. Breaking-in methods conventionally comprise engine assembly and then the controlled use of the engine for some defined period of time. The improvement in those methods comprises the step of creating an integral layer of crystalline phosphate on the cylinder wall prior to the assembly of the engine. More specifically, the improvement comprises creating such a layer prior to the insertion of the engine piston(s) into the cylinder(s) so treated. The creation of the phosphate layer preferably occurs as previously described.

The present invention thus provides an engine having a rust-resistant cylinder assembly, which also has improved piston ring seating and oil consumption characteristics. The invention having been described, however, many modifications thereto will become apparent to those skilled in the art to which it pertains without deviation from the scope of the invention as defined by the appended

Claims

claims. CLAIMS

1. A piston engine comprising: at least one cylinder head; at least one steel cylinder attached to each of said at least one cylinder head, said at least one steel cylinder having an interior cylinder wall and a surface on said wall; a piston disposed in each of said at least one steel cylinder; and a piston ring disposed between said piston and said cylinder wall; wherein said cylinder wall bears an integral layer of crystalline phosphate on said surface.

2. An engine as claimed in claim 1, wherein said surface of said cylinder head is free from corrosion from the process employed for the creation of said integral layer of crystalline phosphate.

3. An engine as claimed in claim 1, wherein said engine is an aircraft engine.

4. An engine as claimed in claim 3, wherein said surface of said cylinder head is free from corrosion from the composition employed for the creation of said integral layer of crystalline phosphate.

5. An engine as claimed in any one of the preceding claims, wherein said integral layer of crystalline phosphate is characterized by resistance to wear by said piston ring during operation of said engine.

6. An engine as claimed in any one of the preceding claims, wherein said integral layer is of the type assisting the seating of said piston ring in said cylinder.

7. An engine as claimed in any one of the preceding claims, wherein said engine is an internal combustion engine.

8. An engine as claimed in any one of the preceding claims, wherein said cylinder head is an aluminium cylinder head.

9. An engine as claimed in claim 8, wherein said aluminium cylinder head bears a chromate conversion coating thereon.

10. An engine as claimed in any one of the preceding claims when fitted to an aircraft.

11. A process for manufacturing an engine as claimed in claim 1, comprising the steps of: attaching at least one unphosphatized steel cylinder to one of said at least one aluminium cylinder head, thereby forming a cylinder assembly; honing the wall of said unphosphatized cylinder; and subsequently converting the surface of said wall to an integral layer of crystalline phosphate.

1 2. A process as claimed in claim 11, wherein said converting step comprises the steps of: (a) applying a phosphatizing solution to said cylinder assembly; said solution comprising water, zinc, and phosphoric acid, and having a pH of about 12.8 to 3.0; at a temperature of about 155 F to 170"F (68"C to 77"C); (b) permitting said solution to contact said cylinder assembly for at least about five minutes; and (c) washing said solution from said cylinder assembly.

1 3. A process as claimed in claim 11 or 12, comprising the preliminary step of washing the cylinder assembly prior to said application step.

14. A process as claimed in claim 11, 1 2 or 13, comprising the subsequent step of application of an oil to the cylinder assembly.

15. A process as claimed in claim 14, wherein said oil application step comprises the immersion of said cylinder assembly into a solution of a water-soluble oil.

1 6. In a process for breaking-in an engine, comprising the steps of constructing said engine and controlling the operation of said engine during a period of initial use, wherein said constructing step includes insertion of a piston and an associated piston ring into a cylinder assembly of said engine, said cylinder assembly comprising at least one cylinder head and at least one steel cylinder assembled to each of said at least one cylinder head; characterised by the step of applying an integral phosphate layer to the surface of said cylinder subsequent to its assembly to said at least one cylinder head, but before insertion of said piston and said piston ring into said cylinder.

17. An engine constructed arranged and adapted to operate substantially as herein described with reference to and as illustrated in the accompanying drawings.

1 8. A process for manufacturing an engine substantially as herein described.

1 9. A process for breaking-in an engine substantially as herein described.