August 4, 2006

Newly Developed Laminated Connecting Rod Module Ideal for Low Emissions is Gentle on the Environment

The NTN Corporation (NTN) has developed a "Laminated Connecting Rod Module Ideal for Low Emission Engines". This product combines a long-life bearing usable under thin lubrication oil conditions to meet tough environmental regulations with a laminated connecting rod designed to be compact for use in 2-cycle engines in agricultural equipment such as trimmers and spray equipment.

In recent years, the state of California (USA) has placed strict environmental regulations (less engine exhaust pollution) on 2-cycle engines for farm equipment. This has led to a trend to reduce the oil level in the oil/gas mixture. Yet reducing the oil level lowers the lubricant level and leads to damage from engine seizure.

To reduce the roller skew (side-slip), which is a cause of seizure in needle bearings, NTN optimized the cage's roller guide design and upgraded the drawn cup(*) outer ring precision. These steps succeeded in stabilizing the roller action.

NTN then confirmed in testing that no seizure occurred under conditions where oil lubrication was reduced 75% in the gas mixture. This low oil lubricant level is a condition 4 times harsher than current levels.

There are also strong customer demands to make the connecting rod (into which the bearing is assembled) more compact. In fine blanking, which is the conventional inexpensive manufacturing method, the minimum width, or connecting rod contour dimensions, is restricted by the machining characteristics so the part cannot be made any smaller.

NTN however succeeded in developing a unique laminated connecting rod with thin plates by press machining. This allows the making of a compact connecting rod whose minimum width is 17% smaller (outer contour dimensions 6% smaller) than rods made by fine blanking.

By providing this low-lubricant, drawn-cup needle bearing into a laminated connecting rod made in-house by press-fitted as a modularized product for its customers, NTN is not only responding to market needs but also helping to make its customer's products more sophisticated, compact and VA/VE (value analysis/value engineering) oriented.

(*)	Drawn-cup: raceway made by precision blanking and drawing from thin steel plate.

[Features]

Offers great protection from seizure under low lubricant conditions (oil cut 75% in oil/gas mixture) 4 times harsher than current conditions by a high precision outer ring and an optimized cage design of drawn-cup needle bearing.
Connecting rod minimum width is 17% (6% for outer contour) less than rods made by conventional fine blanking since NTN's connecting rod is press machined from thin plate to form a unique laminated structure.
In offering this low-lubricant, drawn-cup needle bearing press-fitted into a unique laminated connecting rod as a modularized product for its customers, NTN is helping to make compact, sophisticated, and VA/VE oriented products.

[Applications]

Ideal for 2-cycle engines in farm equipment (trimmers, spray equipment, chainsaws, etc.)

[Product Photo]

"Laminated Connecting Rod Module Ideal for Low Emissions"

[Advantages]

Drawn-cup needle bearing operates even under light lubricant conditions to meet tough environmental regulations
Connecting rod is compact since it uses an in-house laminated structure
Total VA/VE design planning by combining the bearing and connecting rod

[How it is used]

[Cross sectional view of 2-cycle engine for farm machinery]

[Goal and solution]

Goal 1:
- Prevent bearing seizure under light lubricant conditions.
  ⇒ Suppress roller skew (tilting)
Solution:
- (1) Optimize cage's roller-guiding design and
  (2) Make a high precision drawn-cup outer ring
  to stabilize the roller orientation and suppress roller skew.

Goal 2:
- Make engine more compact ⇒ Shrink connecting rod dimensions
  Bridge width in ordinary press processing must be 2.5 times the plate width

Solution: NTN press process uses thin steel plates to allow shrinking bridge width (when center hole diameter is 14mm)

Example:

Fine blanking process:For plate thickness of 4.8mm,

bridge width is 3.6mm ⇒ Outer diameter 21.2

Unique laminated structure: For plate thickness of 1.2mm,

bridge width is 3mm ⇒ Outer diameter 20

[Dimensions cut by 17%] [Dimensions cut by 6%]