US3655466A

US3655466A - Universal joint cross of power transmissions and a method of its heat treatment

Info

Publication number: US3655466A
Application number: US872889A
Authority: US
Inventors: Alexandr Moiseevich Bysink; Grigory Arkadievich Ostrovsky; Konstantin Zakh Shepelyakovsky; Anatoly Georgievich Orlovsky; Stanislav Ivanovich Smirnov; Vladimir Fillippovich Nikonov; Veniamin Davydovich Kalner; Isaak Nokhimovich Shklyarov; Anatoly Loginovich Stepin
Original assignee: Individual
Current assignee: Individual
Priority date: 1968-10-31
Filing date: 1969-10-31
Publication date: 1972-04-11
Anticipated expiration: 1989-04-11
Also published as: DE1955010A1; GB1223960A; DE1955010B2; DE1955010C3; FR2022061A1

Abstract

A universal joint cross for power transmissions, said cross including a base having arms adapted to be engaged by bearing needles, said cross being made of a steel consisting essentially of 0.4 to 1.2 percent carbon and 0.1 to 0.3 percent manganese, the surface hardness of the arms at their points of contact with said bearing needles being in the range of 60 to 67 Rockwell C, and at the points near the base being in the range of 50 to 56 Rockwell C. The method of heat treatment comprises the steps of heating said cross to its hardening temperature, cooling said cross to obtain a hardened surface layer and then nonuniformly tempering said cross.

Description

United States Patent Ostrovsky et al.

[54] UNIVERSAL JOINT CROSS OF POWER TRANSMISSIONS AND A METHOD OF ITS HEAT TREATMENT Oct. 31, 1969 Appl. No.: 872,889

[22] Filed:

[30] Foreign Application Priority Data Oct. 31, 1968 U.S.S.R ..l279470 [151 3,655,466 [451 Apr. 11,1972

[52] U.S.Cl ..148/145,148/36, 148/39, 148/146, 148/150, 148/152, 148/154 [51] Int. Cl. ..C21d H18 [58] Field ofSearch ..148/l43, 145, 146, 150, 152, 148/154, 36, 39

[5 6] References Cited UNITED STATES PATENTS 3,466,202 9/1969 Hrusovsky ..l48/152 Primary Examiner-Richard 0. Dean Attorney-Waters, Roditi, Schwartz & Nissen [5 7] ABSTRACT A universal joint cross for power transmissions, said cross including a base having arms adapted to be engaged by bearing needles, said cross being made of a steel consisting essentially of 0.4 to 1.2 percent carbon and 0.1 to 0.3 percent manganese, the surface hardness of the arms at their points of contact with said bearing needles being in the range of 60 to 67 Rockwell C, and at the points nearthe base being in the range of 50 to 56 Rockwell C. The method of heat treatment comprises the steps of heating said cross to its hardening temperature, cooling said cross to obtain a hardened surface layer and then nonuniformly tempering said cross.

5 Claims, 4 Drawing Figures UNIVERSAL JOINT CROSS OF POWER TRANSMISSIONS AND A METHOD OF ITS HEAT TREATMENT The present invention relates to the universal joint crosses of power transmissions and to the methods of their heat treatment.

In the course of operation, the arms of the universal joint cross are bent to a certain extent and the bearing sleeves with needles turn in relation to the surface of said arms. This causes heavy static, impact and contact loads. To withstand these loads, the crosses have been manufactured up to the present time from case-hardened alloy steels. Practical experience in using the universal joint crosses has shown that high resistance to contact loads can be attained by case-hardening 1.8 2.2 mm deep which calls for a long holding time (over 20 hours) and a low-temperature tempering. However, the increased depth of the carburized layer increases brittleness of the cross and reduces its resistance to the static and impact loads.

The known cross is of a uniform hardness throughout its surface; this fails to ensure an optimum combination of surface hardness with strength of the cross since the different sections of the latter are subjected to different loads. The cylindrical surfaces of the cross arms in the zone of the bearing needles are subjected to heavy contact loads. Hence, these sections of the cross must be especially hard. On the other hand, the sections near the base of the cross arm must have a higher resistance to static and impact bending. Therefore, the hardness of these sections must be lower in order to reduce brittleness.

The known cross is made of expensive alloy steels; its heat treatment, including case hardening, hardening and low-temperature tempering takes much time; still this process fails to ensure the optimum strength of the cross.

An object of the present invention is to eliminate the aforesaid disadvantages.

The main object of the present invention resides in providing a universal joint cross with a higher structural strength and a longer service life along with a lower cost by changing the grade of steel and introducing a special method of its heat treatment.

An object of the present invention resides in providing a universal joint cross with a higher structural strength and a longer service life and featuring a higher resistance to static and impact loads.

Another object of the invention is to provide a cheaper universal joint cross made from cheap steel, and to simplify the process of its heat treatment.

Other objects and advantages of the present invention will become apparent from the description that follows and the accompanying drawings.

The abovementioncd and other objects are achieved by providing a universal joint whose different sections are subjected to different loads which, according to the invention, is made of a low-hardening steel containing 0.4 to 1.2% carbon and 0.1 to 0.3% manganese and which has arms whose surface hardness at the point of contact with the bearing needles varies from 60 to 67 Rock.C. while near the base of the arms it ranges from 50 to 56 Rock.C.

It is preferable that the metal of the cross should contain 0.6% carbon, 0.17% manganese, 0.13%C chromium, 0.2% nickel and 0.04% titanium.

For manufacturing said cross we hereby claim a method of its heat treatment wherein the cross is hardened and then tempered. According to the invention, the cross arms in the zones of contact with the bearing needles are heated to l-200 C within 6 12 seconds while in the sections near the arm bases to a temperature of 450 to 650 C also in the course of 6 to 12 seconds.

It is practicable that tempering should be carried out by heating the entire cross simultaneously.

The present invention is based on the characteristics of the steel proposed for making the crosses and on the principle of conformity of the properties of the material in every area of the article with the nature and the value of the leads acting thereon.

The steel, having the content of components according to the present invention, for example, 0.6% carbon, 0. l7% manganese; 0.13% chrome; 0.2% nickel; 0.04% titanium, has a high decomposition rate of austenite in the 500-700 C. temperature range, where the formation of perlite structure takes place. Such a steel has a lower hardenability than common carbon steels.

This, in effect, means that a cross made from such a steel acquires a martensite structure upon intensive cooling after through heating for hardening, having a hardness of more than 60 Rockwell C only in the surface layer, but not throughout its cross-section. In deep layers of the cross made from the proposed steel, the transformation of austenite takes place in accordance with the perlite mechanism, which results in formation of a troostite-sorbite mixture having a hardness of 35-40 Rockwell C.

The cross made from the proposed steel has the same distribution of hardness throughout the section of the cross arms as if it were made of a case-hardened alloy steel, i.e., a shell having a high degree of hardness in its surface layer, and a strong and viscous core in its deep layers. Such a hardness distribution through the cross-section of the arms of the cross insures the provision of compressive residual stresses in the surface layer. This prevents a cracking when the cross is being hardened, and concurrently increases the resistance of the cross to cyclic (fluctuating) and contact forces.

The non-uniform distribution of hardness in the surface layer of the cross, along the length of the arm, as proposed in the present invention, may be explained by the following reasons:

In proximity to the base of the arm working stresses act which are conditioned by the action of the bending moments. In order to increase the resistance of the cross in response to the working tensile stresses it is necessary to increase the viscosity of the steel in these areas, or essentially to increase the resistance to embrittlement fractures. The simplest way to do this is to reduce the hardness of the martensite-hardened steel to 50-56 Rockwell C. The hardness reduction at the base of the arms only leads to an increase in resistance to static and bending loads of the entire cross. In the areas of the arms where bearing needles are supported, the value of tensile stresses is considerably lower than at the base of the arm. In this region destruction of the steel is caused by high contact stresses, the resistance to which is correlated with the hardness on the basis of the higher the hardness, the greater the contact durability of the steel. Therefore, the cross arms are provided with a hardness of 60-65 Rockwell C, at the points of contact with the bearing needles, and with the properties of the steel in every area or region of the cross arm being adapted to correspond with the character of the leads acting thereon.

Thus, realization of the present invention improves radically the structural strength and extends the service life of the universal joint cross, reduces considerably its cost owing to the use of the cheap carbon steel instead of the expensive alloy steel, decreases the amount of work required for heat treatment and allows a possibility of automating the process of cross manufacture directly in the production line.

Now the invention will described by way of example with reference to the accompanying drawings in which:

FIG. 1 is a schematic view of the universal joint cross complete with a needle bearing;

FIG. 2 is a diagram of induction heating of the universal joint cross for nonuniform tempering according to the claimed method;

FIG. 3 is the macrostructure of the universal joint cross made of low-hardening steel heat-treated according to the claimed method;

FIG. 4 is the macrostructure of the universal joint cross made of alloy steel and heat-treated according to the known method.

The universal joint cross is a solid body 1 (FIG. 1) with four protruding arms 2. Mounted on each arm is a bearing 3 with a sleeve 4 and needles 5. Glands 6 and 7 are intended to keep the lubricant inside the bearing. The bearings 3 are provided on all the four arms 2 of the cross.

High contact stresses are originated during the operation on the section of the arm 2 contacting the bearing needles 5. The sections of the arm 2 free of the bearing needles (those located under the sealing glands 6 and 7) are not subjected to high contact stresses. The static and impact loads create maximum stresses at the base of the arms 2 along section I-l, that is at the points where high resistance to contact loads is not required. The sections of the arm 2 with a high resistance to the contact loads may have a lower resistance to the tensile stresses originated by the bending forces; conversely, the sections effectively withstanding the tensile stresses may possess a low resistance to contact loads. Therefore, if we retain a high hardness 60 Rock.C.) of the arms 2 at the points of contact with the bearing needles 5 and reduce it to 50-56 Rock.C. near the arm where maximum tensile stresses occur, we can combine a high resistance to contact loads with a higher hardness of the entire article. A reduction of hardness to 50-56 Rock.C. near the arm base is quite allowable because at these points the arms contact the sealing glands 6 and 7 and are not subjected to heavy contact loads.

These requirements are satisfied by the claimed universal joint cross illustrated in FIG. 1. This cross is made of a lowhardening steel containing 0.4 to 1.2% carbon, preferably section contacting the bearing needles remains above 60 Rock.C. while at its base it drops to 50-56 Rock.C.

For the sake of comparison, FIG. 4 shows the macrostructure of the universal joint cross made of an alloy steel and heat treated by a known method. In this macrostructure the carburized layer of martensite 12 with a hardness exceeding 60 Rock.C. occupies the entire surface of the cross; the deeper layers are constituted by low-carbon martensite 13 with a hardness of 35-40 Rock.C.

It can be seen from the above that the surface hardness of the arm 2 at the points of contact with the bearing needles 5 and that of the core of the claimed cross are equal to the hardness of the corresponding sections of a case-hardened cross.

However, the claimed cross is considerably cheaper, it is made of anon-alloy steel, it does not require prolonged case hardening and its surface layer near the arm base has a lower hardness which raises the strength of the entire article.

The tests have shown that the claimed universal joint cross,

com ared with the cross made of alloy steel with a casehar ened layer 1.6-2.0 mm deep has a resistance to static bending 75-80 percent higher, while the resistance to impact failure is 300 percent higher, the resistance to brinel1ing being equal. This can be seen from the appended Table.

TABLE [Strength characteristics of universal joint cross obtained by static and impact bending tests] Max-imum bending moment Impact under static strength 'Iime, Steel Method of heat treatment load, kgm. kgm. hours Low-hardening steel, Hardening after deep induction heating, non-uniform eIectric tempering ensuring 1, 250 75 90 distribution of hardness along cross arm to suit operational requirements from 63 to Mn=0.17%, 50 Rock. 0. with a hardened layer 2 mm deep and deeper. Cr=0.13%, Ni=0.2%, Ti=0.04%. C =0 2%, Cr=1 0%, Case hardening 1.6-2 mm. deep, hardening, uniform electric tempering in oil quenching 700 90 1= .0%, bath at 180 0. within 90 minutes to 61 Rock. 0. Ti=0.05%, P 0.003%.

1 Before brinelling appears during closedcircuit stand tests with 220 kgm. torque on cross.

0.6%, and from 0.1 to 0.3 manganese, preferably 0.17%. Besides, the metal of the cross contains 0.13% chromium, 0.2% nickel and 0.04% titanium. The hardness of the cross arms 2 at the points of contact with the bearing needles 5 is within 60 and 67 Rock.C. while on the sections near the arm base it is from 50 to 56 Rock.C.

The method of heat treatment of the universal joint cross made from the above-mentioned low-hardening steel and possessing nonuniform hardness along the arm 2 consists in hardening followed by induction heating for tempering, in which the temperature near the arm base reaches 450-650 C while at the points of the arm contact with the bearing needles 5 it ranges from 100 to 200 C, the heating time being 6 to 12 seconds.

For the implementation of this method, the inductor conductors 8 (FIG. 2) provided with magnetic circuits 9 are placed near the cross as shown in FIG. 2. With such an an rangement of the inductor, the current density is higher near the base of the arms 2, being lower at their face ends. In view of a short heating time (6 to 12 seconds) the equalizing effect of heat conduction is virtually nonexistent so that the sections of the arm contacting the bearing needles 5 and located near the face ends, are tempered at comparatively low temperatures l00-200 C) while their sections located near the cross centre are tempered at considerably higher temperatures (450 to 650 C).

When the cross made of a low-hardening steel is being hardened, its entire surface becomes covered with a layer of martensite 10 (FIG. 3) with a hardness of 65-67 Rock.C. more than 1.5 mm deep, while under this layer there is a layer of troostite with a hardness of -40 Rock.C. After this nonuniform induction tempering the hardness of the arm 2 on the What we claim is:

l. A universal joint cross for power transmissions whose various sections support different loads in operation, said cross including a base having arms adapted to be engaged by bearing needles; said cross being made of a steel consisting essentially of 0.4 to 1.2% carbon and 0.1 to 0.3% manganese, the surface hardness of the arms at their points of contact with said bearing needles being in the range of from to 67 Rockwell C, and at the points near the base being in the range of from 50 to 56 Rockwell C.

2. A universal joint cross according to claim 1 comprising essentially 0.6% carbon and 0.17% manganese.

3. A universal joint cross according to claim 1 comprising essentially 0.13% chromium, 0.2% nickel, and 0.04% titani- 4. A method of heat treatment of a universal joint cross for power transmissions having different sections adapted to carry different loads in operation, said cross inciuding a base having arms adapted to be engaged by bearing needles, and said cross being made of a steel consisting essentially of 0.4 to 12% carbon and 0.1 to 0.3% manganese, said method comprising the steps of: heating said cross to its hardening temperature, intensively cooling said cross to obtain a hardened surface layer, heating said cross for tempering to a range in which the cross arms at their points of contact with the bearing needles are heated to a temperature of to 200 C. for a period of 6 to 12 seconds, and at their points adjacent the base to 450 to 650 C. for a period of 6 to 12 seconds.

5. A method according to claim 4 comprising simultaneously heating the entire cross for tempering.

Claims

2. A universal joint cross according to claim 1 comprising essentially 0.6% carbon and 0.17% manganese.
3. A universal joint cross according to claim 1 comprising essentially 0.13% chromium, 0.2% niCkel, and 0.04% titanium.
4. A method of heat treatment of a universal joint cross for power transmissions having different sections adapted to carry different loads in operation, said cross including a base having arms adapted to be engaged by bearing needles, and said cross being made of a steel consisting essentially of 0.4 to 1.2% carbon and 0.1 to 0.3% manganese, said method comprising the steps of: heating said cross to its hardening temperature, intensively cooling said cross to obtain a hardened surface layer, heating said cross for tempering to a range in which the cross arms at their points of contact with the bearing needles are heated to a temperature of 100* to 200* C. for a period of 6 to 12 seconds, and at their points adjacent the base to 450* to 650* C. for a period of 6 to 12 seconds.
5. A method according to claim 4 comprising simultaneously heating the entire cross for tempering.