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GB1582140A - Light metal pistons - Google Patents

Light metal pistons Download PDF

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Publication number
GB1582140A
GB1582140A GB30948/76A GB3094876A GB1582140A GB 1582140 A GB1582140 A GB 1582140A GB 30948/76 A GB30948/76 A GB 30948/76A GB 3094876 A GB3094876 A GB 3094876A GB 1582140 A GB1582140 A GB 1582140A
Authority
GB
United Kingdom
Prior art keywords
piston
bands
light metal
band
skirt
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
GB30948/76A
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Federal Mogul Bradford Ltd
Original Assignee
Hepworth and Grandage Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Hepworth and Grandage Ltd filed Critical Hepworth and Grandage Ltd
Priority to GB30948/76A priority Critical patent/GB1582140A/en
Priority to IT50303/77A priority patent/IT1079329B/en
Priority to IN1115/CAL/77A priority patent/IN148225B/en
Priority to NZ184707A priority patent/NZ184707A/en
Priority to ZA00774415A priority patent/ZA774415B/en
Priority to DE19772733269 priority patent/DE2733269A1/en
Priority to BR7704827A priority patent/BR7704827A/en
Priority to CA283,390A priority patent/CA1067769A/en
Priority to AU27255/77A priority patent/AU507668B2/en
Priority to FR7722606A priority patent/FR2359334A1/en
Priority to ES460997A priority patent/ES460997A1/en
Priority to JP8790377A priority patent/JPS5314218A/en
Publication of GB1582140A publication Critical patent/GB1582140A/en
Expired legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16J—PISTONS; CYLINDERS; SEALINGS
    • F16J1/00—Pistons; Trunk pistons; Plungers
    • F16J1/04—Resilient guiding parts, e.g. skirts, particularly for trunk pistons
    • F16J1/06—Resilient guiding parts, e.g. skirts, particularly for trunk pistons with separate expansion members; Expansion members
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05C—INDEXING SCHEME RELATING TO MATERIALS, MATERIAL PROPERTIES OR MATERIAL CHARACTERISTICS FOR MACHINES, ENGINES OR PUMPS OTHER THAN NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES
    • F05C2201/00—Metals
    • F05C2201/04—Heavy metals
    • F05C2201/0433—Iron group; Ferrous alloys, e.g. steel
    • F05C2201/0448—Steel
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05C—INDEXING SCHEME RELATING TO MATERIALS, MATERIAL PROPERTIES OR MATERIAL CHARACTERISTICS FOR MACHINES, ENGINES OR PUMPS OTHER THAN NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES
    • F05C2251/00—Material properties
    • F05C2251/04—Thermal properties
    • F05C2251/042—Expansivity

Landscapes

  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • Pistons, Piston Rings, And Cylinders (AREA)

Description

(54) LIGHT METAL PISTONS (71) We, HEPWORTH & GRANDAGE LIMITED, a British Company of St. John's Works, Bradford BD4 8TU, West Yorkshire, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement : - This invention relates to light-metal pistons for reciprocating combustion engines or for reciprocating compressors, that is pistons made predominantly of aluminium, magnesium, or similar metals and their alloys.
Pistons having expansion control inserts, usually of steel, to control the thermal expansion of the piston skirt are well known.
Such pistons may either have transverse slot between the ring groove band and the piston skirt on one or both thrust faces of the piston, or the ring groove band and the skirt may be integral.
If the pistons have a transverse slot on one or both thrust faces, compressive forces are unsupported in this region and, due to the variation in pressure loading on the piston crown during each cycle of operation, the slot opens and closes slightly on each cycle. This ultimately leads to fatigue failure, usually at the ends of the slot. On the other hand, the transverse slot allows an expansion control insert to exert good control of the thermal expansion of the upper end of the skirt, because the skirt is not rigidly con nected to the ring band.
Where the ring groove band and the skirt are integral, compressive forces are supported and fatigue failure from the cause referred to is unlikely. But the control of the thermal expansion of the top end of the skirt by means of the insert is adversely affected, because the top end of the skirt is rigidly connected to the ring band and tends to expand with it. The problem is made worse because the ring band in operation usually becomes hotter than the skirt.
Moreover, hitherto expansion control in serts have been embedded in, and extend on each side of, the gudgeon pin bosses, there normally being two inserts, one associated with each boss.
Typical examples of pistons with expansion control inserts are found in British Patents Nos. 817,866, 869,008, 1,126,480 and 1,126,517. British Patent No. 1,126,480 clearly shows a piston having a transverse slot.
It is clearly difficult to reconcile good thermal expansion control of the top of the skirt with a piston which is strong in compression and resistant to fatigue failure.
Moreover, we have found that the practice of embedding the expansion control insert in the gudgeon pin boss tends to weaken the boss, which is one of the most highlystressed regions of the piston. It will also be well understood that the piston designs must be capable of manufacture on a production scale.
According to the invention, a light-metal piston for a combustion engine or compressor has a crown including an annular band in which piston ring grooves are formed, a skirt around the opposite thrust faces of the piston in a manner to provide with the crown a closed internal cavity, gudgeon pin bosses having bores opening into said cavity, and two expansion control inserts made of a material of lower coefficient of thermal expansion than the light metal, each insert having an upper elongated band and a lower elongated band, both bands extending generally circumferentially around the skirt, the upper and lower bands being interconnected, each band being continuous between its ends and extending from the thrust axis towards the respective gudgeon pin bosses, the upper band having its upper edge extending to the lower surface of the piston ring groove which is nearest to the skirt, whereby the inserts separate the light metal of the piston skirt from that of the annular band around the opposite thrust faces of the piston, the lower band being at a greater distance from the open end of the skirt than the part of the gudgeon pin boss nearer to the open end, and the inserts being substantially symmetrically disposed on each side of the thrust axis of the piston, the free ends of an insert being disposed on the same side of the longitudinal plane containing the gudgeon pin axis as one another.
Preferably the width of the upper band is equal to or greater than that of the lower band. Moreover, preferably the upper and lower bands are joined together at or near their ends.
A number of embodiments of the invention will now be described with reference to the accompanying drawings, of which: Figure 1A is a view of a first design of piston showing a cross-section on the thrust axis, and Figure 1B is a view of the same piston showing a cross-section on the gudgeon pin axis, Figures 2A and 2B show cross-sections on the lines IIA--IIA and lIB-lIB respectively of Figures 1A and 1B, Figure 3 is a developed view of the insert of the piston shown in Figures 1A, 1B, 2A and 2B, Figures 4A, 4B, 5A and 5B are views of a second design of piston, Figure 4A corresponding to Figure 1A, Figure 4B corresponding to Figure 1B, Figure 5A being a section in VA-VA, Figure 5B being a section on VB VB, and Figure 6 being a developed view of the insert, Figures 7A, 7B, 8A and 8B are views of a third design of piston, Figures 7A and 7B corresponding respectively to Figures 1A and 1B, Figure 8A being a section on VIIIA-- VIIIA and Figure 8B being a section on VIlIB-VIlIB, Figures 9, 10 and 11 are views of a fourth design of piston, Figure 9 corresponding to Figure 1A, Figure 10 being a section on X-X, and Figure 11 being a developed view of the insert of this design.
Figure 12 is a view of a fifth design of piston, corresponding to Figure 1A, and Figures 13 to 18 are views of a sixth design of piston, Figure 13 being a cross-section on the line XIII-XIII of Figure 14, Figure 14 being a cross-section on the line XIV-XIV of Figure 13, Figure 15 being a cross-section on the line XV-XV of Figure 14, Figures 16, 17 and 18 being views of the insert, Figure 16 looking on arrow XVI of Figure 18, Figure 17 looking on arrow XVII of Figure 16, and Figure 18 looking on arrow XVIIT of Figure 16.
Referring to Figures 1A, 1B, 2A, 2B and 3, the piston comprises a crown 20, an annular band 21 in which piston ring grooves 22 are formed, a skirt 23 integrally connected with the annular band, a pair of gudgeon pin bosses 24 formed integral with the skirt 23 and having coaxial bores, thrust faces 25 on the thrust axis of the skirt, which axis is at right angles to the gudgeon pin axis, and pillars 26 extending from the bosses 24 to the crown 20.
The piston is made of light alloy (e.g.
aluminium or its alloy) and is provided with a pair of inserts of a material having a lower coefficient of thermal expansion than the light alloy (e.g. of sheet steel).
In this embodiment each insert 27 has an upper elongated band 28, a lower elongated band 29, and a connecting portion 30. It will particularly be noted that contrary to the usual practice, the inserts 27 are symmetrical about the thrust axis of the piston, the connecting portions 30 lying on the thrust axis and the bands 28, 29, extending towards the respective gudgeon pin bosses. Part of the inner face of both the upper bands 28 and the lower bands 29 is open to the interior cavity of the piston, but the upper bands 38 break through into the lower piston ring groove and separate the light metal of the piston skirt 23 from that of the annular band 21 around the opposite thrust faces of the piston.The free ends of the bands 28, 29, may terminate either marginally within (as shown) or outside the gudgeon pin boss 24, and in this embodiment the upper bands are of the same length as the lower bands.
Referring now to Figures 4A, 4B, 5A, 5B and 6 the piston is similar to the first design except for the inserts. Moreover, the materials of the piston body and of the insert are as specified above.
In this embodiment, each insert 37 has an upper elongated band 38 and a lower elongated band 39, and these bands are joined together at both ends of each insert by connecting portions 40. The inserts 37 are symmetrical about the thrust axis of the piston; part of the inner face of both the upper band 38 and the lower band 39 is open to the interior cavity of the piston, but the upper band 38 breaks through into the lower piston ring groove and separates the light metal of the piston skirt 23 from that of the annular band 21 around the opposite thrust faces of the piston. The connection portions 40 marginally overlap the gudgeon pin bosses 24.
Referring to Figures 7A, 7B, 8A and 8B, the piston and inserts are exactly similar to those of the first design, except that the lower elongated bands 49 are shorter than the upper elongated bands 48.
Figure 8A also shows a modification which may be applied to any of the embodiments described herein. In this modification the distance between the two ends of the inserts 47 is reduced, and the light alloy is provided with fillets 51 between the thrust faces 25 and the gudgeon pin bosses 24 in which at least part of the upper bands 48 are embedded.
In another modification, which may be applied to any of the embodiments described herein, the upper faces of the upper bands are stepped, so that they break through into the lower piston ring groove for a distance on each side of the thrust axis, but not towards their ends remote from the thrust axis.
It will be understood that a small part of each insert may be removed during the machining of the lower piston ring groove.
This is shown in Fig. 12.
Referring now to Figures 9-11, the piston is again as described above except for the inserts 87. The latter are again symmetrical about the thrust axis, but each has two connecting portions 90 between the upper elongated band 88 and the lower elongated band 89. The bands 88, 89, are otherwise as described with reference to the first design.
The fifth design of piston, shown in Figure 12, is the same as that of the second design (shown in Figures 4A, 4B, 5A, 5B and 6) except that the connecting portions 100 are extended away from the piston crown to provide anchorage faces 101, and the upper faces of the upper bands 98 are stepped as described above.
In the embodiment of Figures 13 to 18, each insert 107 has an upper elongated band 108, a lower elongated band 109 and connecting portions 110 at the ends of the bands and 111 at their centre.
It will be noted that the inserts 107 are symmetrical about the thrust axis of the piston, the connecting portions 111 lying on the thrust axis and the bands 108, 109, extending towards the respective gudgeon pin bosses where they are joined at their ends by connecting portions 110. Part of the inner face of the upper bands 108 and of the lower bands 109 is open to the interior cavity of the piston, but the upper bands 108 break through into the lower piston ring groove and separate the light metal of the piston skirt 23 from that of the annular band 21 around the opposite thrust faces of the piston.
The ends of the inserts (formed by connection portions 110) may terminate either marginally within (as shown) or outside the gudgeon pin boss 24.
It will be noted that in each case the transverse slot commonly provided between the annular band and the skirt is omitted, and that the inserts separate the skirt from the annular band around the opposite thrust faces by breaking into the lowest piston ring groove.
Pistons having inserts in accordance with the present invention have been found to have greater stiffness on the thrust face than pistons having inserts which are centred on the gudgeon pin boss and extend partway round the circumference on each side of the gudgeon pin boss.
WHAT WE CLAIM IS: 1. A light metal piston for a combustion engine or a compressor having a crown including an annular band in which piston ring grooves are formed, a skirt around the opposite thrust faces of the piston in a manner to provide with the crown a closed internal cavity, gudgeon pin bosses having bores opening into said cavity, and two expansion control inserts made of a material of lower coefficient of thermal expansion than the light metal, each insert having an upper elongated band and a lower elongated band, both bands extending generally circumferentially around the skirt, the upper and lower bands being interconnected, each band being continuous between its ends and extending from the thrust axis towards the respective gudgeon pin bosses, the upper band having its upper edge extending to the lower surface of the piston ring groove which is nearest to the skirt, whereby the inserts separate the light metal of the piston skirt from that of the annular band around the opposite thrust faces of the piston, the lower band being at a greater distance from the open end of the skirt than the part of the gudgeon pin boss nearer to the open end, and the inserts being substantially symmetrically disposed on each side of the thrust axis of the piston, the free ends of an insert being disposed on the same side of the longitudinal plane containing the gudgeon pin axis as one another.
2. A light metal piston as claimed in Claim 1, in which the free ends of the upper and lower bands terminate outside the gudgeon pin bosses.
3. A light metal piston as claimed in Claim 1, in which the free ends of the upper and lower bands terminate marginally within the gudgeon pin bosses.
4. A light metal piston as claimed in any preceding claim, wherein an inter-connecting portion between the upper band and the lower band lies on the thrust axis of the piston.
5. A light metal piston as claimed in claim 4, wherein the connecting portion on the thrust axis is the only connection between the upper and the lower band and the bands are of the same length.
6. A light metal piston as claimed in claim 4, wherein the inter-connecting portion on the thrust axis is the only inter-connecting portion and the bands nearer the open end of the skirt are shorter than the bands nearer the crown end of the skirt.
7. A light metal piston as claimed in claim 4, there being inter-connecting portions between the upper and lower bands both on the thrust axis and at or near the ends of the bands.
8. A light metai piston as claimed in any of claims 1 to 3, wherein the upper and lower bands are joined together by two inter-connecting portions at or near the opposite ends of the insert.
9. A light metal piston as claimed in any preceding claim, in which the upper faces of the inserts are stepped so that they break through into the piston ring groove
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (16)

**WARNING** start of CLMS field may overlap end of DESC **. It will be understood that a small part of each insert may be removed during the machining of the lower piston ring groove. This is shown in Fig. 12. Referring now to Figures 9-11, the piston is again as described above except for the inserts 87. The latter are again symmetrical about the thrust axis, but each has two connecting portions 90 between the upper elongated band 88 and the lower elongated band 89. The bands 88, 89, are otherwise as described with reference to the first design. The fifth design of piston, shown in Figure 12, is the same as that of the second design (shown in Figures 4A, 4B, 5A, 5B and 6) except that the connecting portions 100 are extended away from the piston crown to provide anchorage faces 101, and the upper faces of the upper bands 98 are stepped as described above. In the embodiment of Figures 13 to 18, each insert 107 has an upper elongated band 108, a lower elongated band 109 and connecting portions 110 at the ends of the bands and 111 at their centre. It will be noted that the inserts 107 are symmetrical about the thrust axis of the piston, the connecting portions 111 lying on the thrust axis and the bands 108, 109, extending towards the respective gudgeon pin bosses where they are joined at their ends by connecting portions 110. Part of the inner face of the upper bands 108 and of the lower bands 109 is open to the interior cavity of the piston, but the upper bands 108 break through into the lower piston ring groove and separate the light metal of the piston skirt 23 from that of the annular band 21 around the opposite thrust faces of the piston. The ends of the inserts (formed by connection portions 110) may terminate either marginally within (as shown) or outside the gudgeon pin boss 24. It will be noted that in each case the transverse slot commonly provided between the annular band and the skirt is omitted, and that the inserts separate the skirt from the annular band around the opposite thrust faces by breaking into the lowest piston ring groove. Pistons having inserts in accordance with the present invention have been found to have greater stiffness on the thrust face than pistons having inserts which are centred on the gudgeon pin boss and extend partway round the circumference on each side of the gudgeon pin boss. WHAT WE CLAIM IS:
1. A light metal piston for a combustion engine or a compressor having a crown including an annular band in which piston ring grooves are formed, a skirt around the opposite thrust faces of the piston in a manner to provide with the crown a closed internal cavity, gudgeon pin bosses having bores opening into said cavity, and two expansion control inserts made of a material of lower coefficient of thermal expansion than the light metal, each insert having an upper elongated band and a lower elongated band, both bands extending generally circumferentially around the skirt, the upper and lower bands being interconnected, each band being continuous between its ends and extending from the thrust axis towards the respective gudgeon pin bosses, the upper band having its upper edge extending to the lower surface of the piston ring groove which is nearest to the skirt, whereby the inserts separate the light metal of the piston skirt from that of the annular band around the opposite thrust faces of the piston, the lower band being at a greater distance from the open end of the skirt than the part of the gudgeon pin boss nearer to the open end, and the inserts being substantially symmetrically disposed on each side of the thrust axis of the piston, the free ends of an insert being disposed on the same side of the longitudinal plane containing the gudgeon pin axis as one another.
2. A light metal piston as claimed in Claim 1, in which the free ends of the upper and lower bands terminate outside the gudgeon pin bosses.
3. A light metal piston as claimed in Claim 1, in which the free ends of the upper and lower bands terminate marginally within the gudgeon pin bosses.
4. A light metal piston as claimed in any preceding claim, wherein an inter-connecting portion between the upper band and the lower band lies on the thrust axis of the piston.
5. A light metal piston as claimed in claim 4, wherein the connecting portion on the thrust axis is the only connection between the upper and the lower band and the bands are of the same length.
6. A light metal piston as claimed in claim 4, wherein the inter-connecting portion on the thrust axis is the only inter-connecting portion and the bands nearer the open end of the skirt are shorter than the bands nearer the crown end of the skirt.
7. A light metal piston as claimed in claim 4, there being inter-connecting portions between the upper and lower bands both on the thrust axis and at or near the ends of the bands.
8. A light metai piston as claimed in any of claims 1 to 3, wherein the upper and lower bands are joined together by two inter-connecting portions at or near the opposite ends of the insert.
9. A light metal piston as claimed in any preceding claim, in which the upper faces of the inserts are stepped so that they break through into the piston ring groove
for a distance on each side of the thrust axis but not towards their ends remote from the thrust axis.
10. A light metal piston as claimed in any preceding claim, in which the piston is provided with fillets between the thrust faces and the gudgeon pin bosses in which at least part of the inserts are embedded.
11. A light metal piston substantially as hereinbefore described with reference to and as illustrated in Figures 1A, 1B, 2A, 2B and 3 of the accompanying drawings.
12. A light metal piston substantially as hereinbefore described with reference to and as illustrated in Figures 4A, 4B, 5A and 5B of the accompanying drawings.
13. A light metal piston substantially as hereinbefore described with reference to and as illustrated in Figures 7A, 7B, 8A and 8B of the accompanying drawings.
14. A light metal piston substantially as hereinbefore described with reference to and as illustrated in Figures 9, 10 and 11 of the accompanying drawings.
15. A light metal piston substantially as hereinbefore described with reference to and as illustrated in Figure 12 of the accompanying drawings.
16. A light metal piston substantially as hereinbefore described with reference to and as illustrated in Figures 13 to 18 of the accompanying drawings.
GB30948/76A 1976-07-24 1976-07-24 Light metal pistons Expired GB1582140A (en)

Priority Applications (12)

Application Number Priority Date Filing Date Title
GB30948/76A GB1582140A (en) 1976-07-24 1976-07-24 Light metal pistons
IT50303/77A IT1079329B (en) 1976-07-24 1977-07-15 IMPROVEMENT IN LIGHT ALLOY PISTONS
IN1115/CAL/77A IN148225B (en) 1976-07-24 1977-07-20
NZ184707A NZ184707A (en) 1976-07-24 1977-07-21 Light metal piston with two expansion control inserts, each insert having an upper band, and a lower band
ZA00774415A ZA774415B (en) 1976-07-24 1977-07-21 Light metal pistons
DE19772733269 DE2733269A1 (en) 1976-07-24 1977-07-22 LIGHT ALLOY PISTON
BR7704827A BR7704827A (en) 1976-07-24 1977-07-22 LIGHT METAL FLOORS
CA283,390A CA1067769A (en) 1976-07-24 1977-07-22 Light metal pistons
AU27255/77A AU507668B2 (en) 1976-07-24 1977-07-22 Light metal piston with insert between skirt and band
FR7722606A FR2359334A1 (en) 1976-07-24 1977-07-22 Light metal piston for engine or compressor - has expansion control inserts with lower coefficient of expansion than main body
ES460997A ES460997A1 (en) 1976-07-24 1977-07-23 Light metal piston
JP8790377A JPS5314218A (en) 1976-07-24 1977-07-23 Light metal piston

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB30948/76A GB1582140A (en) 1976-07-24 1976-07-24 Light metal pistons

Publications (1)

Publication Number Publication Date
GB1582140A true GB1582140A (en) 1980-12-31

Family

ID=10315609

Family Applications (1)

Application Number Title Priority Date Filing Date
GB30948/76A Expired GB1582140A (en) 1976-07-24 1976-07-24 Light metal pistons

Country Status (2)

Country Link
GB (1) GB1582140A (en)
ZA (1) ZA774415B (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4730547A (en) * 1983-04-12 1988-03-15 Ae Plc Pistons and piston castings

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4730547A (en) * 1983-04-12 1988-03-15 Ae Plc Pistons and piston castings

Also Published As

Publication number Publication date
ZA774415B (en) 1978-06-28

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