WO2009054122A1 - 滑り軸受を具備した軸受機構 - Google Patents

滑り軸受を具備した軸受機構 Download PDF

Info

Publication number
WO2009054122A1
WO2009054122A1 PCT/JP2008/002981 JP2008002981W WO2009054122A1 WO 2009054122 A1 WO2009054122 A1 WO 2009054122A1 JP 2008002981 W JP2008002981 W JP 2008002981W WO 2009054122 A1 WO2009054122 A1 WO 2009054122A1
Authority
WO
WIPO (PCT)
Prior art keywords
bearing
peripheral surface
slide
housing
rack shaft
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/JP2008/002981
Other languages
English (en)
French (fr)
Inventor
Masahiko Hirose
Yoshihide Ohara
Masaaki Hashimoto
Takahiro Tanaka
Hidetoshi Kaida
Eiji Oki
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Oiles Corp
Oiles Industry Co Ltd
JTEKT Corp
Original Assignee
Oiles Corp
Oiles Industry Co Ltd
JTEKT Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Oiles Corp, Oiles Industry Co Ltd, JTEKT Corp filed Critical Oiles Corp
Priority to CN2008801134650A priority Critical patent/CN101835671B/zh
Priority to EP08842087.2A priority patent/EP2202129B1/en
Priority to US12/739,453 priority patent/US8272785B2/en
Publication of WO2009054122A1 publication Critical patent/WO2009054122A1/ja
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
    • B62D—MOTOR VEHICLES; TRAILERS
    • B62D3/00—Steering gears
    • B62D3/02—Steering gears mechanical
    • B62D3/12—Steering gears mechanical of rack-and-pinion type
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C29/00—Bearings for parts moving only linearly
    • F16C29/002—Elastic or yielding linear bearings or bearing supports
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C29/00—Bearings for parts moving only linearly
    • F16C29/02—Sliding-contact bearings
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C33/00—Parts of bearings; Special methods for making bearings or parts thereof
    • F16C33/02—Parts of sliding-contact bearings
    • F16C33/04—Brasses; Bushes; Linings
    • F16C33/20—Sliding surface consisting mainly of plastics
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C35/00—Rigid support of bearing units; Housings, e.g. caps, covers
    • F16C35/02—Rigid support of bearing units; Housings, e.g. caps, covers in the case of sliding-contact bearings
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C2208/00—Plastics; Synthetic resins, e.g. rubbers
    • F16C2208/20—Thermoplastic resins
    • F16C2208/58—Several materials as provided for in F16C2208/30 - F16C2208/54 mentioned as option
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C2208/00—Plastics; Synthetic resins, e.g. rubbers
    • F16C2208/20—Thermoplastic resins
    • F16C2208/66—Acetals, e.g. polyoxymethylene [POM]
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C2208/00—Plastics; Synthetic resins, e.g. rubbers
    • F16C2208/20—Thermoplastic resins
    • F16C2208/76—Polyolefins, e.g. polyproylene [PP]
    • F16C2208/78—Polyethylene [PE], e.g. ultra-high molecular weight polyethylene [UHMWPE]
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C2226/00—Joining parts; Fastening; Assembling or mounting parts
    • F16C2226/50—Positive connections
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C2326/00—Articles relating to transporting
    • F16C2326/20—Land vehicles
    • F16C2326/24—Steering systems, e.g. steering rods or columns
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C2361/00—Apparatus or articles in engineering in general
    • F16C2361/61—Toothed gear systems, e.g. support of pinion shafts
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H55/00—Elements with teeth or friction surfaces for conveying motion; Worms, pulleys or sheaves for gearing mechanisms
    • F16H55/02—Toothed members; Worms
    • F16H55/26—Racks
    • F16H55/28—Special devices for taking up backlash
    • F16H2055/281—Cylindrical or half-cylindrical bushings around the rack, e.g. using special wedges to reduce play

Landscapes

  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Transportation (AREA)
  • Support Of The Bearing (AREA)
  • Sliding-Contact Bearings (AREA)
  • Mounting Of Bearings Or Others (AREA)
  • Bearings For Parts Moving Linearly (AREA)

Abstract

　軸受機構１は、円筒状の内周面２を有したハウジング３と、ハウジング３内に挿着されていると共に円筒状の外周面４を有したラック軸５と、ハウジング３の内周面２とラック軸５の外周面４との間に介在された滑り軸受６とを具備している。
PCT/JP2008/002981 2007-10-23 2008-10-21 滑り軸受を具備した軸受機構 Ceased WO2009054122A1 (ja)

Priority Applications (3)

Application Number Priority Date Filing Date Title
CN2008801134650A CN101835671B (zh) 2007-10-23 2008-10-21 具有滑动轴承的轴承机构
EP08842087.2A EP2202129B1 (en) 2007-10-23 2008-10-21 Bearing mechanism with slide bearing
US12/739,453 US8272785B2 (en) 2007-10-23 2008-10-21 Bearing mechanism having sliding bearing

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2007-275000 2007-10-23
JP2007275000A JP5481777B2 (ja) 2007-10-23 2007-10-23 滑り軸受を具備した軸受機構

Publications (1)

Publication Number Publication Date
WO2009054122A1 true WO2009054122A1 (ja) 2009-04-30

Family

ID=40579230

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/JP2008/002981 Ceased WO2009054122A1 (ja) 2007-10-23 2008-10-21 滑り軸受を具備した軸受機構

Country Status (5)

Country Link
US (1) US8272785B2 (ja)
EP (1) EP2202129B1 (ja)
JP (1) JP5481777B2 (ja)
CN (1) CN101835671B (ja)
WO (1) WO2009054122A1 (ja)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106838000A (zh) * 2010-09-08 2017-06-13 奥依列斯工业株式会社 滑动轴承
JP2018021910A (ja) * 2016-08-01 2018-02-08 バテル・メモリアル・インスティテュート スナップイン・ブッシュ及び高圧及び／又は高温マジックアングルスピニング核磁気共鳴分光法
CN109340256A (zh) * 2018-11-22 2019-02-15 浙江长盛塑料轴承技术有限公司 一种具有预紧消隙功能的直线轴承系统
CN111065845A (zh) * 2017-09-07 2020-04-24 日本精工株式会社 齿条及其制造方法、以及操舵装置、车辆以及齿条的预成形用金属模具

Families Citing this family (37)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP5167754B2 (ja) * 2007-10-18 2013-03-21 オイレス工業株式会社 ブッシュ軸受
US9409267B2 (en) * 2010-06-17 2016-08-09 Bendix Spicer Foundation Brake Llc Snap-in center seal bushing
JP2012144132A (ja) * 2011-01-11 2012-08-02 Jtekt Corp ラック軸支持装置および車両用操舵装置
JP5664523B2 (ja) * 2011-01-19 2015-02-04 日本精工株式会社 ステアリング装置
FR2973767A1 (fr) * 2011-04-05 2012-10-12 Jtekt Europe Sas Palier de guidage d’un arbre
JP2013079024A (ja) * 2011-10-05 2013-05-02 Jtekt Corp ラック軸用のブッシュおよびラックアンドピニオン式のステアリング装置
JP2014047833A (ja) * 2012-08-30 2014-03-17 Oiles Ind Co Ltd ブッシュ軸受及びそれを用いた自動車のラック−ピニオン式操舵装置
EP2906459B1 (en) * 2012-09-30 2018-06-13 Saint-Gobain Performance Plastics Corporation Steering yoke assembly
JP6034812B2 (ja) * 2014-01-23 2016-11-30 株式会社ショーワ ブッシュ軸受の構造
GB2522501A (en) * 2014-01-23 2015-07-29 Showa Corp Structure of bush bearing
JP5810186B2 (ja) * 2014-03-06 2015-11-11 富士重工業株式会社 ステアリング装置
DE102014103216B4 (de) * 2014-03-11 2021-03-18 Dr. Ing. H.C. F. Porsche Aktiengesellschaft Antriebsvorrichtung zur motorischen Betätigung eines Funktionselementes eines Kraftfahrzeuges
JP2015189378A (ja) * 2014-03-28 2015-11-02 株式会社ショーワ ステアリング装置および軸受部材
US9873448B2 (en) * 2014-03-31 2018-01-23 Steering Solutions Ip Holding Corporation End of travel stop
WO2015163376A1 (ja) * 2014-04-23 2015-10-29 日本精工株式会社 軸受装置、搬送装置、検査装置、及び、工作機械
WO2015163377A1 (ja) 2014-04-23 2015-10-29 日本精工株式会社 軸受装置、搬送装置、検査装置、及び、工作機械
US10100873B2 (en) * 2014-12-09 2018-10-16 Ford Global Technologies, Llc Radially deflectable bushing and steering gear assembly using the same
JP6434327B2 (ja) * 2015-02-03 2018-12-05 オイレス工業株式会社 滑り軸受
DE102015006375B3 (de) * 2015-05-20 2016-09-15 Audi Ag Brennkraftmaschine
JP6634098B2 (ja) 2015-06-30 2020-01-22 サン−ゴバン パフォーマンス プラスティックス コーポレイション 滑り軸受け
JP2017019414A (ja) 2015-07-10 2017-01-26 株式会社ジェイテクト ラックブッシュ
JP6600522B2 (ja) * 2015-10-01 2019-10-30 オイレス工業株式会社 ブッシュ軸受およびそれを備える軸受機構
JP2017087972A (ja) * 2015-11-10 2017-05-25 株式会社ジェイテクト 転舵軸支持構造
KR101957349B1 (ko) * 2016-12-29 2019-06-19 이래에이엠에스 주식회사 전동식 파워 스티어링 시스템
CN106741129B (zh) * 2017-01-10 2019-09-10 上汽通用汽车有限公司 机械转向机
CN106763148B (zh) * 2017-03-28 2023-03-14 京信通信技术(广州)有限公司 一种天线
JP6823902B2 (ja) * 2017-04-03 2021-02-03 オイレス工業株式会社 滑り軸受
JP2018177019A (ja) * 2017-04-14 2018-11-15 株式会社ジェイテクト ステアリング装置
JP6783719B2 (ja) * 2017-08-03 2020-11-11 オイレス工業株式会社 軸受およびステアリング機構
JP6994932B2 (ja) * 2017-12-22 2022-01-14 株式会社シマノ ラインローラ
DE112019003665T5 (de) * 2018-07-20 2021-04-22 Nsk Ltd. Lenkgetriebeeinheit des Zahnstangentyps
US10663025B2 (en) * 2018-07-31 2020-05-26 Bendix Spicer Foundation Brake Llc Bushing assembly for a spring brake actuator of a vehicle air braking system
CN109333280B (zh) * 2018-12-17 2025-04-22 锐奇控股股份有限公司 一种模具电磨
DE102019108235A1 (de) * 2019-03-29 2020-10-01 Schaeffler Technologies AG & Co. KG Lenkungsaktuator
KR102173415B1 (ko) * 2019-06-04 2020-11-03 현대모비스 주식회사 차량용 조향장치의 랙부시
JP7344027B2 (ja) * 2019-07-12 2023-09-13 Ｋｙｂ株式会社 ステアリング装置
KR102207576B1 (ko) * 2019-11-07 2021-01-26 현대모비스 주식회사 차량용 조향장치의 랙부시

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2004255988A (ja) * 2003-02-25 2004-09-16 Koyo Seiko Co Ltd ラックピニオン式舵取装置
JP2004347105A (ja) 2002-08-28 2004-12-09 Oiles Ind Co Ltd 滑り軸受及びそれを具備した軸受機構
JP2006234152A (ja) * 2005-02-28 2006-09-07 Oiles Ind Co Ltd 滑り軸受を具備した軸受機構
JP2007040429A (ja) * 2005-08-03 2007-02-15 Oiles Ind Co Ltd 軸受装置及びこれに用いられる滑り軸受
JP2007050762A (ja) * 2005-08-18 2007-03-01 Jtekt Corp ステアリング装置

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2350898A (en) * 1943-09-13 1944-06-06 Cyrus C Jetter Pump
US4208075A (en) * 1978-09-25 1980-06-17 Burroughs Corporation Zero clearance linear bearing apparatus
US6485180B2 (en) * 2001-01-04 2002-11-26 Delphi Technologies, Inc. Expandable rack bushing
US7534383B2 (en) * 2004-12-08 2009-05-19 Delphi Technologies, Inc. Method of supporting a bushing against radial movement relative to a steering column jacket with a filler material
JP2007099216A (ja) * 2005-10-07 2007-04-19 Jtekt Corp ステアリング装置

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2004347105A (ja) 2002-08-28 2004-12-09 Oiles Ind Co Ltd 滑り軸受及びそれを具備した軸受機構
JP2004255988A (ja) * 2003-02-25 2004-09-16 Koyo Seiko Co Ltd ラックピニオン式舵取装置
JP2006234152A (ja) * 2005-02-28 2006-09-07 Oiles Ind Co Ltd 滑り軸受を具備した軸受機構
JP2007040429A (ja) * 2005-08-03 2007-02-15 Oiles Ind Co Ltd 軸受装置及びこれに用いられる滑り軸受
JP2007050762A (ja) * 2005-08-18 2007-03-01 Jtekt Corp ステアリング装置

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See also references of EP2202129A4 *

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106838000A (zh) * 2010-09-08 2017-06-13 奥依列斯工业株式会社 滑动轴承
JP2018021910A (ja) * 2016-08-01 2018-02-08 バテル・メモリアル・インスティテュート スナップイン・ブッシュ及び高圧及び／又は高温マジックアングルスピニング核磁気共鳴分光法
JP6996894B2 (ja) 2016-08-01 2022-01-17 バテル・メモリアル・インスティテュート スナップイン・ブッシュ及び高圧及び／又は高温マジックアングルスピニング核磁気共鳴分光法
CN111065845A (zh) * 2017-09-07 2020-04-24 日本精工株式会社 齿条及其制造方法、以及操舵装置、车辆以及齿条的预成形用金属模具
CN111065845B (zh) * 2017-09-07 2024-02-23 日本精工株式会社 齿条及其制造方法、以及操舵装置、车辆以及齿条的预成形用金属模具
CN109340256A (zh) * 2018-11-22 2019-02-15 浙江长盛塑料轴承技术有限公司 一种具有预紧消隙功能的直线轴承系统
CN109340256B (zh) * 2018-11-22 2024-06-11 浙江长盛塑料轴承技术有限公司 一种具有预紧消隙功能的直线轴承系统

Also Published As

Publication number Publication date
JP5481777B2 (ja) 2014-04-23
JP2009103206A (ja) 2009-05-14
EP2202129A1 (en) 2010-06-30
CN101835671B (zh) 2012-07-25
US20100278467A1 (en) 2010-11-04
US8272785B2 (en) 2012-09-25
EP2202129B1 (en) 2015-01-21
CN101835671A (zh) 2010-09-15
EP2202129A4 (en) 2012-12-05

Similar Documents

Publication Publication Date Title
USD613355S1 (en) Ball
USD572541S1 (en) Serving tray
USD573847S1 (en) Serving tray
USD578172S1 (en) Weighted exercise apparatus
USD598801S1 (en) Watch dial
USD546402S1 (en) Exercise roller
USD616312S1 (en) Watch
USD562152S1 (en) Dispensing device with ovoid body
USD597880S1 (en) Watch dial
USD612761S1 (en) Bracelet
EP1786335A4 (en) MEDICAL DEVICE WITH ARTICULATED SHAFT
EP1886033A4 (en) THRUST BEARING
EP1631743A4 (en) PUMP ENGINE WITH BEARING LOAD
SI2051751T1 (sl) Krvna ÄŤrpalka
IL190337A0 (en) Axial flow pump with multi-grooved rotor
WO2007121075A3 (en) Golf club shaft insert assembly
EP2051054A4 (en) STORAGE TEMPERATURE MONITORING DEVICE AND STORAGE DEVICE THEREWITH
EP2078962A4 (en) Rolling bearing with rotation sensor
EP2131182A4 (en) LUBRICANT REMOVAL DETECTOR AND BEARING WITH THE DETECTOR
USD549252S1 (en) Bearing housing for a pump
USD582921S1 (en) Mouse pad
PL2153007T3 (pl) Urządzenie zasłaniające mające część końcową z zespolonym wałkiem nawijającym
USD554152S1 (en) Ergonomic pressure calibration pump
USD585501S1 (en) Puzzle
USD616427S1 (en) Keypad

Legal Events

Date Code Title Description
WWE Wipo information: entry into national phase

Ref document number: 200880113465.0

Country of ref document: CN

121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 08842087

Country of ref document: EP

Kind code of ref document: A1

WWE Wipo information: entry into national phase

Ref document number: 2008842087

Country of ref document: EP

NENP Non-entry into the national phase

Ref country code: DE

WWE Wipo information: entry into national phase

Ref document number: 12739453

Country of ref document: US