Cardan shaft joint

Abstract

The invention relates to mechanical engineering, more particularly, cardan shaft joints and can be used in transmissions of various vehicles.

Description

[0001] The present invention relates to mechanical engineering, namely cardan shaft joints and can be used in transmissions of various vehicles.

[0002] Known in the art is a cardan shaft joint including a cross with a needle bearing mounted on each and every pin thereof (cf. USSR inventorship certificate No 1832083, 1993). However, the known cardan shaft joint has insufficient durability and reliability and also poor contact fatigue strength; its cost is high owing to the use, for the manufacture of parts thereof, of construction steels, such as steel, containing 0.95-1.05% C, 0.17-0.37% Si, 0.2-0.4% Mn, 1.3-1.65% Cr, ≦0.3% Ni and ≦0.25% Cu, and low-alloy construction case-hardened steels, such as steel, containing 0.18-0.24% C, 0.17-0.37% Si, 0.8-1.1% Mn, 0.4-0.7% Cr, 0.4-0.7% Ni, 0.03-0.09% Ti and ≦0.3% Cu.

[0003] The technical task of the invention is to create a cardan shaft joint free of the above-listed drawbacks and featuring a high durability and also necessary and prescribed reliability and contact fatigue strength, with a reduced cost thereof at the same time.

[0004] A technical result is achieved owing to the fact that in the proposed cardan shaft joint comprising a cross with a needle bearing mounted on every pin thereof, a distinctive specific feature resides in making the cross, the outer ring and needle rollers of the needle bearing from a carbon construction steel having a lower hardenability and, along with this, the carbon content in the construction steel chosen for manufacturing the cross and the outer ring of the needle bearing is equal while the carbon content in the construction steel chosen for manufacturing the needle rollers is 1.21-1.33 of the carbon content in the construction steel chosen for making the cross and the outer ring of the needle bearing. Also, the microstructure of the surface layer of the cross's pins, the entire volume of the outer ring and the needle bearing needle rollers is a tempered martensite with an austenitic effective grain size varying from 0.0027 to 0.0069 mm. And the microstructure of the surface layer of the outer ring of the needle bearing is a tempered martensite with an austenitic effective grain size ranging from 0.0027 to 0.0069 mm, while the microstructure of the inner layer of the outer ring of the neddle bearing is a troostite having a hardness of 44-47 HRC. Further, the microstructure of the core of pins and the cross body is troostite, troostosorbite or sorbite, with a hardness of the surface of the needle bearing needle rollers exceeding in 2-3 HRC that of the cross pins and the outer ring of the needle bearing.

[0005] The experimental bench and then full-scale comparison tests of the proposed and known designs of a cardan shaft joint have shown that the use of all the distinctive features resulted in creating the cardan shaft joint construction displaying a 18-20% increased durability, a necessary prescribed reliability and a 20-25% improved contact fatigue strength when used within the cardan shafts of automobiles having a different load-carrying capacity, with a concurrently achieved considerable reduction of the cost of the cardan shaft joint, for which protection is being sought.

[0006] The comparison tests for the contact fatigue strength of the conventional and claimed constructions of a cardan shaft joint were conducted in recurrent cycles, with the testing estimated time of 105 hours under the following conditions:

	M twist.,	4790	3687	2107	1318	921
	N m
	n, min−1	500	500	1000	1500	1800
	time, min	1	1	3	7	15

[0007] Tests for durability were conducted with a constant twisting moment till the temperature achieved on the surface of an outer ring is 90° C.

[0008] The comparison test results of the claimed and prior art constructions of a cardan shaft joint are given in the Table.

Joint parts parameters	Conventional joint	Claimed joint
1. Cross pin, dia., mm	33.6	33.6
2. Number of needle rollers, pcs.	29	29
3. Needle roller, dia., mm	4.075	4.075
4. Outer ring wall, thickness, mm	4.1	4.1
5. Material:
cross	steel, containing 0.18-0.24%	steel, containing
	C, 0.17-0.37% Si, 0.8-1.1%	0.62% C, 0.1-0.3% Si,
	Mn, 0.4-0.7% Cr, 0.4-0.7%	≦0.2% Mn, ≦0.15% Cr,
	Ni, 0.03-0.09% Ti, ≦0.3%	≦0.3% Ni, ≦0.2% Cu,
	Cu.	≦0.04% S, ≦0.035% P
needle roller	steel, containing 0.95-1.05%	steel, containing
	C, 0.17-0.37% Si, 0.2-0.4%	0.80% C, 0.1-0.3% Si,
	Mn, 1.3-1.65% Cr, Ni ≦ 0.3%,	≦0.2% Mn, ≦0.15% Cr,
	Cu ≦ 0.25%, ≦0.02% S, ≦	≦0.3% Ni, ≦0.2% Cu,
	0.027% P	≦0.04% S, ≦0.035% P
outer ring	steel, containing 0.12-	steel, containing
	0.19% C, 0.17-0.37% Si, 0.8-	0.62% C, 0.1-0.3% Si,
	1.2% each Mn, Ni and Cr,	≦0.2% Mn, ≦0.15% Cr,
	≦0.3% Cu, ≦0.35% each S	≦0.3% Ni, ≦0.2% Cu,
	and P	0.04% S, ≦0.035% P
6. Heat treatment
a) cross	case-hardening followed by	volume-surface
	hardening with furnace	hardening with tempering
	heating and oil cooling
b) needle roller	hardening with furnace	volume-surface
	heating and oil cooling	hardening with furnace
		tempering
c) outer ring	case-hardening followed by	volume-surface
	hardening with furnace	hardening with furnace
	heating and oil cooling	tempering
7. Hardness, HRC:
a) cross pin surface	60 . . . 61	61 . . . 62
b) needle roller surface	62 . . . 63	63 . . . 64
c) outer ring inner	61 . . . 62	61 . . . 62
surface
d) outer ring core	—	44 . . . 46
8. Microstructure:
a) cross:
surface layer	martensite fine needle +	martensite
	residual austenite	structureless tempered
pins core	troostite + ferrite	troostite
body	troostite + ferrite	troostosorbite
b) needle roller	martensite fine-needle	martenisite
	type + residual austenite	structureless tempered
c) outer ring:
surface layer	martensite average needle +	martensite
	residual austenite	structureless, tempered
core	troostite + ferrite	troostite fine-needle type
9. Effective austenitic grain
size, mm:
cross	0.099-0.0138	0.0049-0.0069
needle roller	0.0069-0.0099	0.0032-0.0049
outer ring	0.0099-0.0138	0.0032-0.0049
10. State of joint parts after
tests:
a) cross pins:
“pitting” of effective	42-50	30-38
area, %
b) needle rollers:
destructed, %	2-4	no
those featuring point	11-13	no
chipping, %
c) outer ring inner
surface:
“pitting” of effective area, %	42-50	30-38
11. Durability of joint, hrs.	405	479

[0009] The invention will now be described in detail with reference to the accompanying drawing illustrating a specific embodiment thereof, in which

[0010] FIG. 1 is a general view of the standard-type cardan shaft joint as proposed.

[0011] The cardan shaft joint is comprised of a cross 1 with a needle bearing 3 mounted on every pin 2 thereof, which includes an outer ring 4 and needle rollers 5. The cross 1 of the joint and also the outer ring 4 and the needle rollers 5 of the needle bearing 3 are made from a structural carbon steel having a lower hardenability. The cross 1 of the joint and the outer ring 4 of its needle bearing 3 are made of the structural carbon steel with the same carbon content. To make the needle rollers 5 of the needle bearing 3, use is made of the structural carbon steel with a carbon content selected within the limits of 1.21-1.33 of the carbon contained in the steel which has been utilized to manufacture the cross 1 and the outer ring 4 of the needle bearing 3 and, along with this, in a surface layer of the pins 2 of the cross 1 of the joint and also in the entire volume of the outer ring 4 and the needle rollers 5 of the needle bearing 3 there is created a microstructure of a martensite tempered with the size of the effective austenitic grain being from 0.0027 to 0.0069 mm.

[0012] At the same time, the outer ring of a needle bearing in another embodiment has a microstructure of the surface layer in the form of a martensite tempered with the size of the effective austenitic grain being from 0.0027 to 0.0069 mm, and the microstructure of an inner layer—a troostite having a hardness of 44-47 HRC. The core of the pins 2 and the body of the cross 1 contain a microstructure of troostite, troostosorbite or sorbite. The surface hardness of the needle rollers 5 of the needle bearing 3 has been chosen to exceed 2-3 HRC the hardness of the surface of contact of the pins 2 of the cross 1 and the hardness of the surface of contact of the outer ring 4 of the needle bearing 3.

Claims

1. A cardan shaft joint including a cross with a needle bearing mounted on every pin thereof, wherein the cross, outer ring and the needle rollers of the needle bearing are made from a structural carbon steel having a lower hardenability, subjected to volume-surface hardening and tempering, and a carbon content in the structural steel selected for manufacturing the cross and outer ring of the needle bearing is equal while the carbon contained in the structural steel selected for making the needle rollers is 1.21-1.33 of the carbon contained in the structural steel selected for manufacturing the cross and the outer ring of the needle bearing.

2. The cardan shaft joint of claim 1, wherein the microstructure of the surface layer of the cross pins, the entire volume of the outer ring and the needle rollers of the needle bearing is a martensite tempered with the size of the effective austenitic grain being from 0.0027 to 0.0069 mm.

3. The cardan shaft joint of claim 1, wherein the microstructure of the surface layer of the cross pins, the needle rollers and the microstructure of the surface layer of the outer ring of the needle bearing is a martensite tempered with the size of the effective austenitic grain being from 0.0027 to 0.0069 mm while the microstructure of the core of the needle bearing outer ring is a troostite having a hardness varying from 44 to 47 HRC.

4. The cardan shaft joint of claim 1, wherein the microstructure of the core of pins and the cross body is troostite, troostosorbite or sorbite.

5. The cardan shaft joint of claim 1, wherein the surface hardness of the needle rollers of the needle bearing exceeds by 2-3 HRC the surface hardness of cross pins and that of the outer ring of the needle bearing.