專業(yè)英語電子轉(zhuǎn)向系統(tǒng)

1、電子信息工程專業(yè)英語期末考查 第15頁 電子動力轉(zhuǎn)向系統(tǒng) 院（系）名稱 專業(yè)班級 學(xué)生姓名 學(xué)號2013年 6月 14 日電子動力轉(zhuǎn)向系統(tǒng)電動轉(zhuǎn)向系統(tǒng)使用的電動馬達(dá)直接驅(qū)動動力轉(zhuǎn)向液壓泵或轉(zhuǎn)向聯(lián)動裝置。動力轉(zhuǎn)向功能，因此獨立的發(fā)動機轉(zhuǎn)速，產(chǎn)生顯著的能源節(jié)約。它是如何工作的： 傳統(tǒng)的動力轉(zhuǎn)向系統(tǒng)中使用的發(fā)動機附件皮帶驅(qū)動泵，提供加壓流體操作的活塞中的動力轉(zhuǎn)向齒輪或致動器，以輔助駕駛員。電動液壓轉(zhuǎn)向，由一個電動馬達(dá)驅(qū)動的電動轉(zhuǎn)向概念使用一個高效率的泵。泵的轉(zhuǎn)速的調(diào)節(jié)由一個電動控制器，以改變泵的壓力和流量，提供專為不同的駕駛的情況下的轉(zhuǎn)向工作。該泵可在低速運行或關(guān)閉，在直線行駛時節(jié)約能源（這是世界大

2、部分市場的大部分的時間）。直接電動轉(zhuǎn)向使用電動馬達(dá)經(jīng)由齒輪機構(gòu)（沒有泵或流體）連接到轉(zhuǎn)向齒條。多種類型的電機和齒輪傳動裝置是可能的。微處理器控制轉(zhuǎn)向動力和驅(qū)動程序的效果。輸入包括車速，轉(zhuǎn)向，車輪扭矩，角度位置和轉(zhuǎn)彎速度。詳細(xì)的工作：一個“轉(zhuǎn)向傳感器”位于輸入軸即進入變速箱殼體的地方。轉(zhuǎn)向傳感器實際上是在一個兩位一體的傳感器：“轉(zhuǎn)矩傳感器”的輸入的轉(zhuǎn)向轉(zhuǎn)矩和它的方向轉(zhuǎn)換成電壓信號，并轉(zhuǎn)換成電壓信號的旋轉(zhuǎn)速度和方向的“旋轉(zhuǎn)傳感器”。共用同一個殼體的一個“接口”電路的信號轉(zhuǎn)換成控制電子裝置來自扭矩傳感器和旋轉(zhuǎn)傳感器的可以處理的信號。來自轉(zhuǎn)向傳感器的輸入信號被一個微處理器控制單元消化，它也監(jiān)視車輛的速

3、度傳感器的輸入。該傳感器的輸入，然后比較，以確定需要多大的權(quán)力，輔助是根據(jù)在控制單元的內(nèi)存里的預(yù)編程的“力地圖”，?？刂茊卧缓蟀l(fā)送相應(yīng)的命令給“動力裝置”，然后提供電動機電流。電機推壓機架的右側(cè)或左側(cè)根據(jù)這種方式電壓流量（換向旋轉(zhuǎn)電機的電流的相反方向）。隨著電動機電流的增加，電力輔助量也跟著增加。該系統(tǒng)具有三種操作模式：“正?！钡目刂颇Ｊ街?，向左或向右的功率助推被提供作為對轉(zhuǎn)向扭矩和旋轉(zhuǎn)感應(yīng)器的輸入信號的響應(yīng)，一個“返回”控制模式，它被用于在一個轉(zhuǎn)向后協(xié)助完成轉(zhuǎn)彎；和“阻尼器”的控制模式，它沒用于改變車速，以改善道路的感覺，抑制回旋。如果方向盤被打開并保持在充分鎖定位置和轉(zhuǎn)向輔助達(dá)到最大值

4、，則控制單元減少向電動馬達(dá)輸送的電流，以防止過載的情況下，可能會損壞電機?？刂茊卧脑O(shè)計也可以保護，防止由有故障的發(fā)電機或充電問題引起的電壓突波。這種電子轉(zhuǎn)向控制單元是能夠自我診斷故障通過監(jiān)測系統(tǒng)的輸入和輸出和電動馬達(dá)的驅(qū)動電流。如果出現(xiàn)問題，控制單元通過電源單元驅(qū)動故障安全繼電器將系統(tǒng)關(guān)閉。這消除了所有的輔助電源，使系統(tǒng)恢復(fù)到手動轉(zhuǎn)向。破折號EPS警告燈同時亮起，以提醒駕駛員。對于要診斷的問題，技術(shù)員來到服務(wù)檢查連接器的端子上，就可以讀出故障碼電子能源轉(zhuǎn)向系統(tǒng)希望能在不增加成本的情況下，減輕重量，節(jié)省燃料和包裝的靈活性。歐洲的高的燃油價格和小型車輛為電動轉(zhuǎn)向提供了廣闊的測試平臺，汽車制造商承

5、諾的節(jié)省重量和燃油經(jīng)濟性收益的技術(shù)。在很短的時間，在美國也將使電動轉(zhuǎn)向取得成功。在密歇根州薩吉諾主任德爾福沙基諾從事轉(zhuǎn)向系統(tǒng)的研究和開發(fā)的編輯Aly Badawy說：“它僅僅只是一個時間問題，”現(xiàn)在這個問題是在我們身后的費用問題。到2002年，在這里，在美國電子能源轉(zhuǎn)向的成本將絕對超過液壓洗。今天，電動和混合動力汽車（EV），包括豐田的普銳斯和通用汽車公司的EV-1是電子能源轉(zhuǎn)動的完美的代表。但到2010年，TRW公司內(nèi)部研究估計，在世界上生產(chǎn)的每三輛汽車將配備一個某種形式的電動助力轉(zhuǎn)向?？死蛱m的供應(yīng)商聲稱其新的轉(zhuǎn)向系統(tǒng)可以提高燃油經(jīng)濟性高達(dá)2英里，同時增強處理能力。有真正的底線收益，以及為

6、汽車制造商降低整體成本，并減少裝配時間，因為不需要泵，軟管和流體“另一個宣傳的優(yōu)點是縮短開發(fā)時間。例如，德爾福集團開發(fā)的E-TUNE，乘坐和處理的軟件包，可以運行一臺筆記本電腦。 “他們可以把那臺電腦，插上電源，連接到控制器，并改變所有的處理參數(shù) - 努力水平，回正，阻尼 - 上飛”，Badawy說。 “這需要幾個月的時間?！钡聽柛Ｓ幸粋€OEM客戶，在99年開始小批量生產(chǎn)。電動轉(zhuǎn)向裝置通常放置在三個位置：列驅(qū)動器，齒輪驅(qū)動器和機架驅(qū)動。哪個系統(tǒng)將成為常態(tài)，目前仍不清楚。短期來看，整合到現(xiàn)有的平臺OEM廠商最容易的是選擇轉(zhuǎn)向系統(tǒng)。顯然，更大的潛力來自系統(tǒng)設(shè)計，成一個全新的平臺?！焙諣柭┦空f斯特

7、雷克爾Gmuend的施瓦本，德國采埃孚轉(zhuǎn)向系統(tǒng)事業(yè)部的集團副總裁說：“我們所有三種正在考慮的設(shè)計，哪個版本終將使用和制造的市場和原始設(shè)備制造商（OEM）。”“大廠家都抓住了他們考慮的核心技術(shù)，在密歇根州斯特林高地TRW公司的副總裁詹姆斯解釋說：“大廠家都抓住了他們考慮的核心技術(shù)，電動助力轉(zhuǎn)向，他的公司提供了一系列的電動轉(zhuǎn)向系統(tǒng)（混合動力電動，機架，小齒輪，和列驅(qū)動器）。 TRW公司仍然認(rèn)為它最初集中在最純粹的工程解決方案 - 電動轉(zhuǎn)向齒條驅(qū)動系統(tǒng)。該系統(tǒng)有時也指直接驅(qū)動或球/螺母驅(qū)動器。不過，這個冬天TRW對沖賭注，形成一個合資企業(yè)，LucasVarity。英國供應(yīng)商收到5000萬美元的外匯，

8、其電動的列驅(qū)動轉(zhuǎn)向技術(shù)和套。列和齒輪傳動電動轉(zhuǎn)向系統(tǒng)的初始生產(chǎn)預(yù)計于2000年在英國伯明翰開始。當(dāng)前發(fā)明與提供的供給動力的援助一電子功率驅(qū)動器馬達(dá)關(guān)連給車操縱機構(gòu)。根據(jù)當(dāng)前發(fā)明的一個方面，那里為提供供給動力的援助提供一個電子功率驅(qū)動器機制給有車的操縱機構(gòu)一名手動地可旋轉(zhuǎn)的成員為操作操縱機構(gòu)、傳動機構(gòu)包括可行扭矩的傳感器感覺手動地被申請于可旋轉(zhuǎn)的成員的扭矩，一個電子功率驅(qū)動器馬達(dá)操縱著被連接到可旋轉(zhuǎn)的成員和安排控制主驅(qū)動電動機自轉(zhuǎn)速度和方向以回應(yīng)從扭矩傳感器收到的信號的控制器，扭矩傳感器包括為與可旋轉(zhuǎn)的成員的連接適應(yīng)的傳感器軸形成引伸因此，以便扭矩通過前述傳感器軸被傳送，當(dāng)時 可旋轉(zhuǎn)的成員被轉(zhuǎn)動

9、，并且應(yīng)變儀在導(dǎo)致的信號傳感器軸手動地登上表示通過前述軸被傳送的相當(dāng)數(shù)量扭矩。傳感器軸不旋轉(zhuǎn)更好地登上在一個軸向末端在第一名聯(lián)結(jié)成員和不旋轉(zhuǎn)地登上在它的相反軸向末端在第二名聯(lián)結(jié)成員，第一和第二名聯(lián)結(jié)成員相互允諾允許有限的自轉(zhuǎn)之間連接，以便在一個被預(yù)先決定的極限之下的扭矩由僅傳感器軸傳送，并且，以便在前述被預(yù)先決定的極限之上的扭矩通過第一和第二名聯(lián)結(jié)成員被傳送。更適宜地安排第一和第二名聯(lián)結(jié)成員作為操縱的連接的第一和第二個部分的一座橋梁互相的旋轉(zhuǎn)式成員。合適的傳感器軸是通常在多數(shù)的長方形橫斷面它的長度中。應(yīng)變儀包括一個或更多的適應(yīng)地看見了諧振器綁到傳感器軸上。好的馬達(dá)操縱的被連接到可旋轉(zhuǎn)的成員通過

10、傳動器。馬達(dá)更好地包括一個工具箱和同心地被安排相對可旋轉(zhuǎn)的成員。當(dāng)前發(fā)明的Various方面此后將描述，關(guān)于伴隨的圖畫， ：圖1是一個車操縱機構(gòu)的一個圖表看法包括一個電子功率驅(qū)動器機制根據(jù)當(dāng)前發(fā)明，圖 2是說明在圖顯示的傳動機構(gòu)的各種各樣的組分的之間流程圖互作用1上，圖 3是一個軸截面通過在圖顯示的傳動機構(gòu)1，圖4上是一張截面圖被采取沿著線IV-IV在表3，圖5是在圖顯示的輸入推進聯(lián)結(jié)的一張更加詳細(xì)的分解圖3上，和圖 6是顯示在表3.的傳動器的一張更加詳細(xì)的分解圖。 圖1的最初Referring，那里顯示一個車操縱機構(gòu)10操縱的被連接到一個對易操縱的路輪子12。這個顯示的操縱機構(gòu)包括一個齒條和

11、齒輪匯編14被連接到路輪子12通過聯(lián)接15。 鳥翼末端(沒顯示)匯編14可旋轉(zhuǎn)地駕駛一名手動地可旋轉(zhuǎn)的成員以駕駛桿18的形式哪些由方向盤19手動地轉(zhuǎn)動。這個駕駛桿18包括包括一臺電主驅(qū)動電動機的一個電力的傳動機構(gòu)30 (沒顯示在駕駛的鳥翼末端圖1)上以回應(yīng)在駕駛桿18的扭矩裝貨為了為機械人員提供力量援助，當(dāng)轉(zhuǎn)動方向盤19時。如概要地被說明在表2，電力的傳動機構(gòu)包括測量駕駛桿申請的扭矩18，當(dāng)駕駛鳥翼末端時并且提供信號給控制器40的扭矩傳感器20。 控制器40被連接到主驅(qū)動電動機50并且控制電流被提供給馬達(dá)50控制馬達(dá)50和它的自轉(zhuǎn)的方向扭矩引起的相當(dāng)數(shù)量。馬達(dá)50 操縱的更適宜地被連接到駕駛桿

12、18通過工具箱60，更適宜地一個周轉(zhuǎn)齒輪箱子和傳動器70。 在一定條件下傳動器70在正常運行時更適宜地永久地接合并且是有效的隔絕從馬達(dá)50的驅(qū)動使鳥翼末端通過傳動機構(gòu)30手動地被駕駛。 這是使機制的安全特點起作用在試圖的馬達(dá)50情形下駕駛太快速的駕駛桿并且/或者在錯誤的方向或在案件 電動機和工具箱占領(lǐng)了。扭矩傳感器20更適宜地是一個匯編包括在扭矩應(yīng)用達(dá)到的傳感器軸登上應(yīng)變儀能夠準(zhǔn)確測量張力在一個被預(yù)先決定的范圍之內(nèi)的一個短的傳感器軸。被測量扭矩的被預(yù)先決定的范圍是0-lONm; 更好是關(guān)于l-5Nm。被測量的扭矩的范圍更好地對應(yīng)于大約0-1000微指令，并且傳感器軸的建筑更好被選擇這樣5Nm扭

13、矩比在軸的2°導(dǎo)致較少的轉(zhuǎn)彎，少于1 °。好的應(yīng)變儀是鋸諧振器，在WO91/13832被描述的一臺適當(dāng)?shù)匿徶C振器。 類似在圖顯示的那WO91/13832 3上更好地運用配置，二看見諧振器被安排在對軸軸的45°和在90°對互相。諧振器經(jīng)營與在200-400 MHz之間共鳴頻率和被安排導(dǎo)致信號到控制器1 MHz 40 ± 500 KHz根據(jù)傳感器軸的自轉(zhuǎn)方向的自我調(diào)節(jié)。 因此，當(dāng)傳感器軸不被扭轉(zhuǎn)的歸結(jié)于缺乏扭矩時，它導(dǎo)致一個1 MHz信號。當(dāng)它導(dǎo)致在1.0到1.5 MHz之間的一個信號的傳感器軸在一個方向被扭轉(zhuǎn)。 當(dāng)傳感器軸在相反方向時被扭轉(zhuǎn)它導(dǎo)致

14、在1.0到0.5 MHz之間的一個信號。 因而同樣傳感器能導(dǎo)致信號表示程度扭矩并且傳感器軸的自轉(zhuǎn)的方向。好的馬達(dá)扭矩引起的相當(dāng)數(shù)量以回應(yīng)在0-10Nm之間被測量的扭矩是0-40Nm，并且為在l-5Nm之間被測量的扭矩是0-25Nm。反饋電路提供自我調(diào)節(jié)，借以馬達(dá)使用的電流由控制器40測量并且比較保證馬達(dá)在正確方向運行并且提供期望功率協(xié)助。 控制器更好地行動使被測量的扭矩降低到零和如此控制馬達(dá)增加它的扭矩產(chǎn)品減少被測量的扭矩。 (沒顯示)更適宜地提供車速傳感器哪些寄發(fā)一個信號表示車速到控制器。 控制器使用這個信號修改程度力量協(xié)助提供以回應(yīng)被測量的扭矩。將提供在低車速最大力量協(xié)助的，因而，并且將提

15、供高車速極小的力量協(xié)助。更適宜地是邏輯順序器有一個現(xiàn)場可編程序的門數(shù)組例如XC 4005如Xilinx供應(yīng)這個控制器。 這樣控制器不依靠軟件和，因此能更起作用可靠地在汽車車環(huán)境里。 被想象也許使用有邏輯的序列一個現(xiàn)場可編程序的列陣。一個電力傳動機構(gòu)10的A具體建筑在表3.被說明EPS電子助力轉(zhuǎn)向系統(tǒng)（EPS），和液壓動力轉(zhuǎn)向系統(tǒng)（HPS）相比，EPS具有更多優(yōu)點。EPS的優(yōu)點是：1）高效率。高壓鈉燈的效率非常低，一般在60至70，而EPS和電氣連接，效率高，有的可高達(dá)90。2）能量消耗少。汽車交通的實際過程中，約5的時間旅行的時候，HPS系統(tǒng)，發(fā)動機運轉(zhuǎn)，水泵將始終處于工作狀態(tài)，石油管道一直在

16、流通，使車輛的燃油消耗率4至6，而每股盈利僅在需要時為能源，車輛的燃油消耗率只增加了0.5。3）“路感”好。因為車內(nèi)部剛性的使用，使系統(tǒng)的滯后可以由軟件控制，可用于根據(jù)操作的驅(qū)動程序來調(diào)節(jié)。4）回好。 EPS結(jié)構(gòu)簡單，內(nèi)阻小，是一個很好的背，拿回來是最好的特點，提高了車輛的操控性和穩(wěn)定性。5）環(huán)境污染少。 HPS液壓回路中的液壓軟管和連接器，油泄漏的存在，但無法恢復(fù)液壓軟管，在一定程度上對環(huán)境的污染，而EPS幾乎沒有對環(huán)境造成污染。6）可以是獨立的發(fā)動機的工作。 EPS為電池供電的設(shè)備，只要電量充足，不管是什么條件，發(fā)動機都可以產(chǎn)生動力的作用。7）有一個廣泛的范圍。8）易于組裝和良好的布局?，F(xiàn)

17、在，一些汽車的動力轉(zhuǎn)向系統(tǒng)已經(jīng)成為標(biāo)準(zhǔn)制定，全世界約有一半的汽車使用動力轉(zhuǎn)向。隨著汽車電子技術(shù)的發(fā)展，一些汽車已經(jīng)采用電動助力轉(zhuǎn)向齒輪，汽車的經(jīng)濟性，動力和流動性有所改善。汽車電動助力轉(zhuǎn)向裝置在汽車上是一個新的動力轉(zhuǎn)向系統(tǒng)設(shè)備，近年來在國內(nèi)外發(fā)展迅速，由于其采用可編程的電子控制裝置，與此同時它的靈活性也有了安全隱患。在分析這種獨特的產(chǎn)品的特點，制作者結(jié)合電子控制裝置的特性和安全檢查，指出了有關(guān)安全性因素的問題,提出了處理安全性的措施,并討論了一些涉及安全的具體問題。結(jié)果是：現(xiàn)有的標(biāo)準(zhǔn)不能滿足電動動力轉(zhuǎn)向裝置的安全需求，并提出了對電動助力轉(zhuǎn)向裝置進行安全性測評的思。研究關(guān)于電動助力轉(zhuǎn)向裝置的發(fā)展

18、和評估工作具有參考價值英語原文Electronic power steering system Electrically powered steering uses an electric motor to drive either the power steering hydraulic pump or the steering linkage directly. The power steering function is therefore independent of engine speed, resulting in significant energy savings.How i

19、t works:Conventional power steering systems use an engine accessory belt to drive the pump, providing pressurized fluid that operates a piston in the power steering gear or actuator to assist the driver.In electro-hydraulic steering, one electrically powered steering concept uses a high efficiency p

20、ump driven by an electric motor. Pump speed is regulated by an electric controller to vary pump pressure and flow, providing steering efforts tailored for different driving situations. The pump can be run at low speed or shut off to provide energy savings during straight ahead driving (which is most

21、 of the time in most world markets).Direct electric steering uses an electric motor attached to the steering rack via a gear mechanism (no pump or fluid). A variety of motor types and gear drives is possible. A microprocessor controls steering dynamics and driver effort. Inputs include vehicle speed

22、 and steering, wheel torque, angular position and turning rate. Working In Detail:A "steering sensor" is located on the input shaft where it enters the gearbox housing. The steering sensor is actually two sensors in one: a "torque sensor" that converts steering torque input and i

23、ts direction into voltage signals, and a "rotation sensor" that converts the rotation speed and direction into voltage signals. An "interface" circuit that shares the same housing converts the signals from the torque sensor and rotation sensor into signals the control electronics

24、 can process. Inputs from the steering sensor are digested by a microprocessor control unit that also monitors input from the vehicle's speed sensor. The sensor inputs are then compared to determine how much power assist is required according to a preprogrammed "force map" in the contr

25、ol unit's memory. The control unit then sends out the appropriate command to the "power unit" which then supplies the electric motor with current. The motor pushes the rack to the right or left depending on which way the voltage flows (reversing the current reverses the direction the m

26、otor spins). Increasing the current to the motor increases the amount of power assist.The system has three operating modes: a "normal" control mode in which left or right power assist is provided in response to input from the steering torque and rotation sensor's inputs; a "return

27、" control mode which is used to assist steering return after completing a turn; and a "damper" control mode that changes with vehicle speed to improve road feel and dampen kickback.If the steering wheel is turned and held in the full-lock position and steering assist reaches a maximum

28、, the control unit reduces current to the electric motor to prevent an overload situation that might damage the motor. The control unit is also designed to protect the motor against voltage surges from a faulty alternator or charging problem.The electronic steering control unit is capable of self-di

29、agnosing faults by monitoring the system's inputs and outputs, and the driving current of the electric motor. If a problem occurs, the control unit turns the system off by actuating a fail-safe relay in the power unit. This eliminates all power assist, causing the system to revert back to manual

30、 steering. A dash EPS warning light is also illuminated to alert the driver. To diagnose the problem, a technician jumps the terminals on the service check connector and reads out the trouble codesElectric power steering systems promise weight reduction, fuel savings and package flexibility, at no c

31、ost penalty.Europe's high fuel prices and smaller vehicles make a fertile testbed for electric steering, a technology that promises automakers weight savings and fuel economy gains. And in a short time, electric steering will make it to the U.S., too. "It's just just a matter of time,&q

32、uot; says Aly Badawy, director of research and development for Delphi Saginaw Steering Systems in Saginaw, Mich. "The issue was cost and that's behind us now. By 2002 here in the U.S. the cost of electric power steering will absolutely be a wash over hydraulic."Today, electric and hybr

33、id-powered vehicles (EV), including Toyota's Prius and GM's EV-1, are the perfect domain for electric steering. But by 2010, a TRW Inc. internal study estimates that one out of every three cars produced in the world will be equipped with some form of electrically-assisted steering. The Cleve

34、land-based supplier claims its new steering systems could improve fuel economy by up to 2 mpg, while enhancing handling. There are true bottom-line benefits as well for automakers by reducing overall costs and decreasing assembly time, since there's no need for pumps, hoses and fluids.Another cl

35、aimed advantage is shortened development time. For instance, a Delphi group developed E-TUNE, a ride-and-handling software package that can be run off a laptop computer. "They can take that computer and plug it in, attach it to the controller and change all the handling parameters - effort leve

36、l, returnability, damping - on the fly," Badawy says. "It used to take months." Delphi has one OEM customer that should start low-volume production in '99.Electric steering units are normally placed in one of three positions: column-drive, pinion-drive and rack-drive. Which system

37、 will become the norm is still unclear. Short term, OEMs will choose the steering system that is easiest to integrate into an existing platform. Obviously,greater potential comes from designing the system into an all-new platform. "We have all three designs under consideration," says Dr. H

38、erman Strecker, group vice president of steering systems division at ZF in Schwaebisch Gmuend, Germany. "It's up to the market and OEMs which version finally will be used and manufactured." "The large manufacturers have all grabbed hold of what they consider a core technology,&quo

39、t; explains James Handy sides, TRW vice president, electrically assisted steering in Sterling Heights, Mich. His company offers a portfolio of electric steering systems (hybrid electric, rack-, pinion-, and column-drive). TRW originally concentrated on what it still believes is the purest engineerin

40、g solution for electric steering-the rack-drive system. The system is sometimes refer to as direct drive or ball/nut drive. Still, this winter TRW hedged its bet, forming a joint venture with LucasVarity. The British supplier received $50 million in exchange for its electric column-drive steering te

41、chnology and as sets. Initial production of the column and pinion drive electric steering systems is expected to begin in Birmingham, England, in 2000.The present invention relates to an electrically powered drive mechamsm for providing powered assistance to a vehicle steering mechanism. According t

42、o one aspect of the present invention, there is provided an electrically powered driven mechanism for providing powered assistance to a vehicle steering mechanism having a manually rotatable member for operating the steering mechanism, the drive mechanism including a torque sensor operable to sense

43、torque being manually applied to the rotatable member, an electrically powered drive motor drivingly connected to the rotatable member and a controller which is arranged to control the speed and direction of rotation of the drive motor in response to signals received from the torque sensor, the torq

44、ue sensor including a sensor shaft adapted for connection to the rotatable member to form an extension thereof so that torque is transmitted through said sensor shaft when the rotatable member is manually rotated and a strain gauge mounted on the sensor shaft for producing a signal indicative of the

45、 amount of torque being transmitted through said shaft. Preferably the sensor shaft is non-rotatably mounted at one axial end in a first coupling member and is non-rotatably mounted at its opposite axial end in a second coupling member, the first and second coupling members being inter-engaged to pe

46、rmit limited rotation there between so that torque under a predetermined limit is transmitted by the sensor shaft only and so that torque above said predetermined limit is transmitted through the first and second coupling members. The first and second coupling members are preferably arranged to act

47、as a bridge for drivingly connecting first and second portions of the rotating member to one another. Preferably the sensor shaft is of generally rectangular cross-section throughout the majority of its length. Preferably the strain gauge includes one or more SAW resonators secured to the sensor sha

48、ft. Preferably the motor is drivingly connected to the rotatable member via a clutch .Preferably the motor includes a gear box and is concentrically arranged relative to the rotatable member. Various aspects of the present invention will hereafter be described, with reference to the accompanying dra

49、wings, in which :Figure 1 is a diagrammatic view of a vehicle steering mechanism including an electrically powered drive mechanism according to the present invention, Figure 2 is a flow diagram illustrating interaction between various components of the drive mechanism shown in Figure 1 ,Figure 3 is

50、an axial section through the drive mechanism shown in Figure 1, Figure 4 is a sectional view taken along lines IV-IV in Figure 3,Figure 5 is a more detailed exploded view of the input drives coupling shown in Figure 3, and Figure 6 is a more detailed exploded view of the clutch showing in Figure 3.

51、Referring initially to Figure 1 , there is shown a vehicle steering mechanism 10 drivingly connected to a pair of steerable road wheels The steering mechanism 10 shown includes a rack and pinion assembly 14 connected to the road wheels 12 via joints 15. The pinion(not shown) of assembly 14 is rotata

52、bly driven by a manually rotatable member in the form of a steering column 18 which is manually rotated by a steering wheel 19.The steering column 18 includes an electric powered drive mechanism 30 which includes an electric drive motor (not shown in Figure 1) for driving the pinion in response to t

53、orque loadings in the steering column 18 in order to provide power assistance for the operative when rotating the steering wheel 19.As schematically illustrated in Figure 2, the electric powered drive mechanism includes a torque sensor20 which measures the torque applied by the steering column 18 wh

54、en driving the pinion and supplies a signal to a controller 40. The controller 40 is connected to a drive motor 50 and controls the electric current supplied to the motor 50 to control the amount of torque generated by the motor 50 and the direction of its rotation. The motor 50 is drivingly connect

55、ed to the steering column 18 preferably via a gear box 60, preferably an epicyclic gear box, and a clutch 70. The clutch 70 is preferably permanently engaged during normal operation and is operative under certain conditions to isolate drive from the motor 50 to enable the pinion to be driven manuall

56、y through the drive mechanism 30. This is a safety feature to enable the mechanism to function in the event of the motor 50 attempting to drive the steering column too fast and/or in the wrong direction or in the case where the motor and/or gear box have seized.The torque sensor 20 is preferably an

57、assembly including a short sensor shaft on which is mounted a strain gauge capable of accurately measuring strain in the sensor shaft brought about by the application of torque within a predetermined range. Preferably the predetermined range of torque which is measured is 0-lONm; more preferably is

58、about l-5Nm.Preferably the range of measured torque corresponds to about 0-1000 microstrain and the construction of the sensor shaft is chosen such that a torque of 5Nm will result in a twist of less than 2° in the shaft, more preferably less than 1 ° .Preferably the strain gauge is a SAW

59、resonator, a suitable SAW resonator being described in WO91/13832. Preferably a configuration similar to that shown in Figure 3 of WO91/13832 is utilised wherein two SAW resonators are arranged at 45° to the shaft axis and at 90° to one another. Preferably the resonators operate with a resonance frequency of between 200-400 MHz and are arranged to produce a signal to the controller 40 of 1 MHz ± 500 KHz depending upon the direction of rotation of the sensor shaft. Thus, when the sensor shaft is not being twisted due to the abse