Description:TECHNICAL FIELD
[001] The embodiments herein generally relate to manufacturing process for synchronizer rings and more, particularly to a heat treatment process for the synchronizer ring used in a power transmission unit (gearbox).
BACKGROUND
[002] Generally, a manual transmission used in an automobile incorporates synchronizer devices so that a drive shaft and a transmission gear rotate in synchronization with each other during a gear shift operation. Typically, the synchronizer device includes synchronizer ring which can effectively reduce vibration, impact and noise in the gear shifting process of the automobile, thereby improving the operating stability and the driving safety of the automobile. In transmissions used for vehicles with powerful engines, the synchronizer rings are subject to increased wear, on account of a high frictional load. The same is also applicable for automatic manual transmissions (AMT). For example in a transmission of a commercial vehicle or in a transmission of a passenger automobile in which high gearshift forces are applied, wearing of friction surface (groove) in synchronizer ring is a common failure mode. The wearing of the friction surface (groove) in the synchronizer ring results in hard shifting or gear slippage. It is customary for synchronizer rings to be made from metal, preferably from brass which may increase the service life of highly stressed synchronizer rings and therefore also that of the transmission, with an additional friction layer protecting the support from wear. However, choosing high strength material or surface coating to synchronizer ring is expensive.
[003] Therefore, there exists a need for a heat treatment process for the synchronizer ring, which obviates the aforementioned drawbacks.
OBJECTS
[004] The principal object of embodiments herein is to provide a heat treatment process for synchronizer ring.
[005] Another object of embodiments herein is to provide the heat treated synchronizer ring which has high surface hardness thereby resulting in high abrasion resistance.
[006] Another object of embodiments herein is to provide a synchronizer ring material composition.
[007] Another object of embodiments herein is to provide the heat treated synchronizer ring which has uniform grain distribution of predefined shape across entirety of the heat treated synchronizer ring.
[008] Another object of embodiments herein is to provide the heat treated synchronizer ring which consists of more than 95% hard beta phase structure and Mn5Si3 precipitates.
[009] These and other objects of embodiments herein will be better appreciated and understood when considered in conjunction with following description and accompanying drawings. It should be understood, however, that the following descriptions, while indicating embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications.
BRIEF DESCRIPTION OF DRAWINGS
[0010] The embodiments are illustrated in the accompanying drawings, throughout which like reference letters indicate corresponding parts in various figures. The embodiments herein will be better understood from the following description with reference to the drawings, in which:
[0011] Fig. 1 depicts a flowchart indicating steps of a heat treatment process for a synchronizer ring used in a power transmission unit (gearbox) of a vehicle, according to embodiments as disclosed herein;
[0012] Fig. 2a depicts a microstructure of a conventional synchronizer ring without heat treatment; and
[0013] Fig. 2b depicts a microstructure of the heat treated synchronizer ring, according to embodiments as discloses herein.
DETAILED DESCRIPTION
[0014] The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
[0015] The embodiments herein achieve a heat treatment process for synchronizer ring. Referring now to the drawings Figs. 1 through 2b, where similar reference characters denote corresponding features consistently throughout the figures, there are shown embodiments.
[0016] Fig. 1 depicts a flowchart indicating steps of a heat treatment process (100) for a synchronizer ring used in a power transmission unit (gearbox) of a vehicle, according to embodiments as disclosed herein. For the purpose of this description and ease of understanding, the heat treatment process (100) is explained herein with below reference to synchronizer ring used in power transmission unit (gearbox) of a vehicle. However, it is also within the scope of the invention to use/practice heat treatment process for synchronizer rings used in power transmission unit (gearbox) of industrial machines or to use the heat treatment process (100) for any other transmission members or any other component used in vehicles, industrial machines or any other applications, where enhancement of surface hardness with high wear resistance is required, without otherwise deterring the intended function of heat treatment process (100) as can be deduced from the description and corresponding drawings. At step (102), the heat treatment process (100) includes, heating synchronizer ring work piece at a temperature range of 665 to 755° C for a time period range of 75 to 100 minutes. At step (104), the heat treatment process (100) includes, quenching the heated synchronizer ring work piece in a temperature controlled fluid at a temperature range of 25 to 90° C. At step (106), the heat treatment process (100) includes, cooling the quenched synchronizer ring work piece at room temperature for a predefined time period. At step (108), the heat treatment process (100) includes, stress relieving on the room temperature cooled synchronizer ring work piece by heating the room temperature cooled synchronizer ring work piece at a temperature range of 250 to 320° C for a time period range of 60 to 90 minutes. At step (110), the heat treatment process (100) includes, air cooling the stress relieved synchronizer ring work piece after the method step (108). For the purpose of this description and ease of understanding, the temperature controlled fluid is considered to be water. It is also within the scope of the invention to use any other liquids or fluids instead of water without otherwise deterring the intended function of the temperature controlled fluid as can be deduced from the description and corresponding drawings.
[0017] The method step (102) of heating synchronizer ring work piece at the temperature range of 665 to 755° C for the time period range of 75 to 100 minutes includes, maintaining heating rate at less than or equal to 160° C/ m. The method step (104) of quenching the heated synchronizer ring work piece in the temperature controlled fluid at the temperature range of 25 to 90° C includes, maintaining quenching rate at greater than or equal to 110° C/s. The synchronizer ring work piece is made of brass alloy.
[0018] Further, the method step (106) of cooling the quenched synchronizer ring work piece at room temperature for the predefined time period includes, storing the quenched synchronizer ring work piece in storage rack(s) at the room temperature for the predefined time period which is less than or equal to 4 hours.
[0019] The heat treatment process (100) is performed after hot forging process and before machining process of synchronizer ring work piece. A microstructure of the heat treated synchronizer ring work piece consists of more than 95% hard beta phase structure (as shown in fig. 2b) and Mn5Si3 precipitates. The heat treated synchronizer ring work piece has uniform grain distribution of predefined shape across entirety of the heat treated synchronizer ring work piece, (as shown in fig. 2b).
[0020] A manufacturing process for synchronizer ring includes brass alloy casting process, hot extrusion of tube process, tube cutting into rings process, hot forging process, heat treatment process (100) and machining process.
[0021] In an embodiment, synchronizer ring material composition comprises, 61.5 to 63.5 wt% of copper (Cu), 3.0-3.3 wt% of aluminium (Al), 0.38-0.45 wt% of nickel (Ni), 3.1-3.5 wt% of manganese (Mn), 0.14-0.18 wt% of chromium (Cr), 0.6-1.2 wt% of silicon (Si) and Zinc (Zn): balance wt% of the total composition. The Al, Si, Ni & Cr strengthens base matrix structure while Mn & Si forms Mn5Si3 hard precipitates.

Property Existing synchronizer ring
(without heat treatment) Heat treated synchronizer ring Remarks
Hardness, HRB 88 - 90 97 - 99 ↑ 7 to 10 HRB

[0022] From the above table, the hardness (HRB) of the synchronizer ring is 88 to 90 HRB, and the hardness (HRB) of the heat treated synchronizer ring according to embodiments discloses herein is 97 to 99 HRB. Therefore, it is clearly evident that the hardness of the heat treated synchronizer ring has increased by 7 to 10 HRB.
[0023] The technical advantage of the heat treatment process (100) is as follows. The heat treated brass alloy synchronizer ring has high surface hardness thereby resulting in high abrasion (wear) resistance. The heat treated synchronizer ring has uniform grain distribution of predefined shape across entirety of the heat treated synchronizer ring. The heat treated synchronizer ring consists of more than 95% hard beta phase structure and Mn5Si3 precipitates.
[0024] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modifications within the spirit and scope of the embodiments as described herein.
, Claims:We claim:
1. A heat treatment process (100) for synchronizer ring, said heat treatment process (100) comprising:
heating synchronizer ring work piece at a temperature range of 665 to 755° C for a time period range of 75 to 100 minutes;
quenching the heated synchronizer ring work piece in a temperature controlled fluid at a temperature range of 25 to 90° C;
cooling the quenched synchronizer ring work piece at room temperature for a predefined time period; and
stress relieving on the room temperature cooled synchronizer ring work piece by heating the room temperature cooled synchronizer ring work piece at a temperature range of 250 to 320° C for a time period range of 60 to 90 minutes.
2. The heat treatment process (100) as claimed in claim 1, wherein said heating synchronizer ring work piece at the temperature range of 665 to 755° C for the time period range of 75 to 100 minutes includes,
maintaining heating rate at less than or equal to 160° C/ m.
3. The heat treatment process (100) as claimed in claim 1, wherein said quenching the heated synchronizer ring work piece in the temperature controlled fluid at the temperature range of 25 to 90° C includes,
maintaining quenching rate at greater than or equal to 110° C/s.
4. The heat treatment process (100) as claimed in claim 1, wherein said heat treatment process (100) includes,
air cooling the stress relieved synchronizer ring work piece(s) after said stress relieving on the room temperature cooled synchronizer ring work piece by heating the room temperature cooled synchronizer ring work piece at the temperature range of 250 to 320° C for the time period range of 60 to 90 minutes.

5. The heat treatment process (100) as claimed in claim 1, wherein said synchronizer ring work piece is made of brass alloy.
6. The heat treatment process (100) as claimed in claim 1, wherein said cooling of the quenched synchronizer ring work piece at said room temperature for the predefined time period includes,
storing the quenched synchronizer ring work piece in storage rack(s) at the room temperature for the predefined time period which is less than or equal to 4 hours.
7. The heat treatment process (100) as claimed in claim 1, wherein a microstructure of the heat treated synchronizer ring work piece consists of more than 95% hard beta phase structure and Mn5Si3 precipitates; and
the heat treated synchronizer ring work piece includes uniform grain distribution of predefined shape across entirety of the heat treated synchronizer ring work piece.
8. The heat treatment process (100) as claimed in claim 1, wherein said heat treatment process (100) is performed after hot forging process and before machining process of synchronizer ring work piece.
9. A manufacturing process for synchronizer ring according to claim 1, wherein said manufacturing process includes brass alloy casting process, hot extrusion of tube process, tube cutting into rings process, hot forging process, heat treatment process (100) and machining process.
10. A synchronizer ring material composition comprising:
(a) 61.5 to 63.5 wt% of copper (Cu);
(b) 3.0-3.3 wt% of aluminium (Al);
(c) 0.38-0.45 wt% of nickel (Ni);
(d) 3.1-3.5 wt% of manganese (Mn);
(e) 0.14-0.18 wt% of chromium (Cr);
(f) 0.6-1.2 wt% of silicon (Si); and
(g) Zinc (Zn): balance wt% of the total composition.