Drawn Cup Needle Roller Bearings for Throttle Bodies - NTN Global
NTN TECHNICAL REVIEW No.73（2005）
[ New Product ]
Drawn Cup Needle Roller Bearings for Throttle Bodies
Hideki AKAMATSU**
Drawn cup needle roller bearings have an outer ring that is precisely drawn from a thin steel plate. Of all bearings with outer rings, drawn cup needle roller bearings have the smallest cross sectional height, which enables both space and cost savings. This chapter introduces the features as well as the performance of sealed, low friction, low air leak drawn cup needle roller bearings for use in throttle bodies.
1. Introduction
2. Structure and features
A throttle valve is a device that controls the amount of air fed into an engine. To cope with recent growing needs for better fuel efficiency and lower emissions, electronically controlled throttle valves that are capable of fine adjustment of an air/fuel ratio are being used increasingly. As a result of the employment of electronic control, the means for driving throttle valves has changed from wires to motors. Rolling contact bearings, which feature decreased friction, are also being used increasingly to enable both a compact lightweight design and an improved response with the motor used for this purpose. Rolling contact bearings are being used in the systems that control the airflow into automotive engines as well. The support for the throttle blade must not allow air to leak, therefore rolling contact bearings must have good sealing performance. To address these needs, we have developed drawn cup needle roller bearings for throttle bodies that have seals with lower friction and less air leakage. This paper introduces the features and performance of these drawn cup needle roller bearings.
The rolling bearings used for electronically controlled throttle valves can be categorized as deep grooved ball bearings (hereafter, referred to as "ball bearings") and drawn cup needle roller bearings (hereafter, referred to as "drawn cup bearings") (Fig. 1). Compared with ball bearings, drawn cup bearings have smaller outside diameters, and as a result, the radial space of the housing can be smaller and the housing can be lighter. Ball bearings are narrower than drawn cup bearings, but their built-in seals alone cannot completely prevent air leakage so additional seals must be incorporated, which leads to the need for additional space and expense. Our newly developed drawn cup bearing assembly consists of a drawn cup bearing fabricated by the prebent technique* and a seal that does not have a core metal. This bearing does not need additional sealing, and it can contribute to environmental protection through cost reduction, space conservation and reduced weight. *Pre-bent technique: a technique in which a cage and rollers are
fit into a drawn cup outer ring, and then the assembly is subjected to heat treatment.
*Automotive Sales Headquarters Needle Roller Bearings Engineering Dept.
-76-
Drawn Cup Needle Roller Bearings for Throttle Bodies
Throttle blade
Throttle blade
Return spring
Motor
Return spring Separate seal
Motor Drawn cup bearing (w/ built-in seal)
Deep groove ball bearing
Control gearing
Drawn cup bearing application example
Control gearing
Deep groove ball bearing application example
Fig. 1 Structure of electronic throttle bodies
Table 1 Specification of drawn cup needle roller bearings for throttle bodies
Development target
Specifications
Dimensions Inscribed circle dia. 10×outside dia. 14×width 14 mm
Fig. 2 Structure of drawn cup needle roller bearings for throttle bodies
Outer ring
Chromium molybdenum steel
Cage
V-type welded cage
Rollers
Crowned
Seal
Fluorine rubber, no core metal
Rated load
Dynamic rated load Cr 4500 N Static rated load C0r 5100 N
Others
High performance grease applied
Friction
1.1 N-cm max.
Air leakage 0.8cm3/min. max.
3. Friction Performance Table 2 Test result of friction
The friction performance of the bearings that support the throttle blade is a critical factor in adopting a compact design and achieving quick response with the motor. A friction measurement value is obtained by inserting a torque gauge with a shaft of a specified diameter into a drawn cup bearing that is press-fitted into a standard ring, and turning the gauge 90 degrees. The friction value of these bearings is approximately 0.8 N-cm, which is sufficiently lower than the development target of 1.1 N-cm (Table 2)
-77-
Development target
1.1 N-cm max.
Number of samples (n)
30 pcs.
Mean value
0.78 N-cm
Max. value
0.85 N-cm
Min. value
0.70 N-cm
Standard deviation
0.054 N-cm
NTN TECHNICAL REVIEW No.73（2005）
4. Air Leakage Prevention Performance Because the throttle valve regulates the amount of air fed into the engine, the amount of air leakage from the supports of the throttle blade must be strictly controlled. The measuring method and resultant measurements of the air leakage on drawn cup bearings are summarized below. Before starting the air leakage measurements, each drawn cup bearing was press-fit into a ring of specified dimensions, and the shaft was inserted into the bearing of a specified diameter. This set was then mounted to a sufficiently rigid measuring head. The other measuring head was shut with a lid, and was used as a standard control. These heads were connected to an air leakage tester, the open space in each head was adjusted to a negative pressure, and then air leakage was measured. Photo 1 shows the air leakage tester, and Fig. 3 illustrates the measurement heads. The amount of air leakage with our drawn cup bearing was 0.01 cm3/min. or lower, which is sufficiently lower than the development target of 0.8 cm3/min (Table 3).
Suction
Standard control
Negative pressure Test bearing Suction Atmospheric pressure
Fig. 3 Measurement part Table 3 Test result of air leakage Bearing Diameter of shaft Air leakage inserted (mm) No. Development target: 0.8 cm3/min. max. 0.01cm3/min. max.
No.1 No.2
φ9.975
0.01cm3/min. max.
No.3
0.01cm3/min. max.
No.4
0.01cm3/min. max.
5. Conclusion This paper has introduced our unique drawn cup bearing assembly for a throttle valve. This assembly incorporates a compact, less expensive drawn cup bearing and a seal that features lower friction and air leakage prevention capabilities. Use of this bearing helps reduce the size of the throttle valve and improve the response speed. We believe that this bearing will offer better control of air-fuel ratios for automotive engines, helping realize better fuel efficiency and lower emissions and thus contributing to global environmental protection. Photo 1 Air leakage tester
Photos of author
Hideki AKAMATSU Automotive Sales Headquraters Needle Roller Bearings Engineering Dept.
-78-
[ New Product ]
Drawn Cup Needle Roller Bearings for Throttle Bodies
Hideki AKAMATSU**
Drawn cup needle roller bearings have an outer ring that is precisely drawn from a thin steel plate. Of all bearings with outer rings, drawn cup needle roller bearings have the smallest cross sectional height, which enables both space and cost savings. This chapter introduces the features as well as the performance of sealed, low friction, low air leak drawn cup needle roller bearings for use in throttle bodies.
1. Introduction
2. Structure and features
A throttle valve is a device that controls the amount of air fed into an engine. To cope with recent growing needs for better fuel efficiency and lower emissions, electronically controlled throttle valves that are capable of fine adjustment of an air/fuel ratio are being used increasingly. As a result of the employment of electronic control, the means for driving throttle valves has changed from wires to motors. Rolling contact bearings, which feature decreased friction, are also being used increasingly to enable both a compact lightweight design and an improved response with the motor used for this purpose. Rolling contact bearings are being used in the systems that control the airflow into automotive engines as well. The support for the throttle blade must not allow air to leak, therefore rolling contact bearings must have good sealing performance. To address these needs, we have developed drawn cup needle roller bearings for throttle bodies that have seals with lower friction and less air leakage. This paper introduces the features and performance of these drawn cup needle roller bearings.
The rolling bearings used for electronically controlled throttle valves can be categorized as deep grooved ball bearings (hereafter, referred to as "ball bearings") and drawn cup needle roller bearings (hereafter, referred to as "drawn cup bearings") (Fig. 1). Compared with ball bearings, drawn cup bearings have smaller outside diameters, and as a result, the radial space of the housing can be smaller and the housing can be lighter. Ball bearings are narrower than drawn cup bearings, but their built-in seals alone cannot completely prevent air leakage so additional seals must be incorporated, which leads to the need for additional space and expense. Our newly developed drawn cup bearing assembly consists of a drawn cup bearing fabricated by the prebent technique* and a seal that does not have a core metal. This bearing does not need additional sealing, and it can contribute to environmental protection through cost reduction, space conservation and reduced weight. *Pre-bent technique: a technique in which a cage and rollers are
fit into a drawn cup outer ring, and then the assembly is subjected to heat treatment.
*Automotive Sales Headquarters Needle Roller Bearings Engineering Dept.
-76-
Drawn Cup Needle Roller Bearings for Throttle Bodies
Throttle blade
Throttle blade
Return spring
Motor
Return spring Separate seal
Motor Drawn cup bearing (w/ built-in seal)
Deep groove ball bearing
Control gearing
Drawn cup bearing application example
Control gearing
Deep groove ball bearing application example
Fig. 1 Structure of electronic throttle bodies
Table 1 Specification of drawn cup needle roller bearings for throttle bodies
Development target
Specifications
Dimensions Inscribed circle dia. 10×outside dia. 14×width 14 mm
Fig. 2 Structure of drawn cup needle roller bearings for throttle bodies
Outer ring
Chromium molybdenum steel
Cage
V-type welded cage
Rollers
Crowned
Seal
Fluorine rubber, no core metal
Rated load
Dynamic rated load Cr 4500 N Static rated load C0r 5100 N
Others
High performance grease applied
Friction
1.1 N-cm max.
Air leakage 0.8cm3/min. max.
3. Friction Performance Table 2 Test result of friction
The friction performance of the bearings that support the throttle blade is a critical factor in adopting a compact design and achieving quick response with the motor. A friction measurement value is obtained by inserting a torque gauge with a shaft of a specified diameter into a drawn cup bearing that is press-fitted into a standard ring, and turning the gauge 90 degrees. The friction value of these bearings is approximately 0.8 N-cm, which is sufficiently lower than the development target of 1.1 N-cm (Table 2)
-77-
Development target
1.1 N-cm max.
Number of samples (n)
30 pcs.
Mean value
0.78 N-cm
Max. value
0.85 N-cm
Min. value
0.70 N-cm
Standard deviation
0.054 N-cm
NTN TECHNICAL REVIEW No.73（2005）
4. Air Leakage Prevention Performance Because the throttle valve regulates the amount of air fed into the engine, the amount of air leakage from the supports of the throttle blade must be strictly controlled. The measuring method and resultant measurements of the air leakage on drawn cup bearings are summarized below. Before starting the air leakage measurements, each drawn cup bearing was press-fit into a ring of specified dimensions, and the shaft was inserted into the bearing of a specified diameter. This set was then mounted to a sufficiently rigid measuring head. The other measuring head was shut with a lid, and was used as a standard control. These heads were connected to an air leakage tester, the open space in each head was adjusted to a negative pressure, and then air leakage was measured. Photo 1 shows the air leakage tester, and Fig. 3 illustrates the measurement heads. The amount of air leakage with our drawn cup bearing was 0.01 cm3/min. or lower, which is sufficiently lower than the development target of 0.8 cm3/min (Table 3).
Suction
Standard control
Negative pressure Test bearing Suction Atmospheric pressure
Fig. 3 Measurement part Table 3 Test result of air leakage Bearing Diameter of shaft Air leakage inserted (mm) No. Development target: 0.8 cm3/min. max. 0.01cm3/min. max.
No.1 No.2
φ9.975
0.01cm3/min. max.
No.3
0.01cm3/min. max.
No.4
0.01cm3/min. max.
5. Conclusion This paper has introduced our unique drawn cup bearing assembly for a throttle valve. This assembly incorporates a compact, less expensive drawn cup bearing and a seal that features lower friction and air leakage prevention capabilities. Use of this bearing helps reduce the size of the throttle valve and improve the response speed. We believe that this bearing will offer better control of air-fuel ratios for automotive engines, helping realize better fuel efficiency and lower emissions and thus contributing to global environmental protection. Photo 1 Air leakage tester
Photos of author
Hideki AKAMATSU Automotive Sales Headquraters Needle Roller Bearings Engineering Dept.
-78-
