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may Bua dong coc diesel

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20. may Bua dong coc diesel

a. Cau tao chung

May bua dong coc diesel thuong gom ba phan chinh:

- May co so: thuong dung can truc xich hoac may dao mot gau, co khi chi dung toa quay lap tren gia di chuyen bang banh sat dat tren duong ray (hinh 6-2). Hinh 6-2. Cau tao chung cua may dong coc dat tren duong ray

1- Khung duoi; 2- Banh sat; 3- Gia bua; 4,5- Co cau dieu chinh gia bua; 6- Toa quay.

- Gia bua: gom he thanh dan huong cho dau bua trong qua trinh dong coc; thanh xien; thanh ngang; thanh nay co the dieu chinh goc nghieng cua gia (ve phia truoc hay phia sau), thuong khoang 50 khi can dong coc xien. De dieu chinh duoc co the dung tangdo hoac xy lanh thuy luc.

- Dau bua: la bo phan truc tiep gay ra luc de dong coc.

Cac may bua dong coc diesel deu co nguyen ly lam viec chung cua dong co diesel. Loi dung su roi tu do cua bua de nen khong khi toi ap suat va nhiet do cao, nhien lieu duoc phun vao gap nhiet do va ap suat cao tu boc chay, tao ap luc khi lon day bua len cao. Thoi diem bua dap vao dau coc xay ra truoc khi nhien lieu boc chay. Uu diem cua loai may bua nay la cau tao gon, de van chuyen. Nhuoc diem la khoi dong kho, dac biet la khi gap dat mem, cong dong coc nho, toc do dong cham, thuong chi dat 5080 lan/ph, nhien lieu dat tien. Khi dong coc o nen dat yeu va ve mua dong bua kho no, do luc dong coc lon nen dau coc de bi vo gay anh huong toi cong trinh xung quanh. Co ba loai bua dong coc diesel: loai hai coc dan, loai ong dan va loai xylanh dan; trong do loai hai coc dan va loai ong dan duoc dung nhieu hon.

b. Bua dong coc diesel hai coc dan (h.6-3, a):

Hinh 6-3. Bua dong coc diesel

a. Loai hai coc dan; b. Loai ong dan; 1- Be bua; 2- Day bua (duc lien voi pittong 12) ; 3- Lo phun dau; 4- Coc dan huong; 5- Chot; 6- Moc khoi dong; 7- Xa ngang; 8- Cap treo; 9- Don dieu khien moc; 10- Xylanh; 11- Chot (thanh gat); 12- Pittong; 13- Duong dau; 14- Bom dau cao ap; 15- Kep dau coc; 16- Dinh vau; 17- Phan be; 18- Lo thoat khi; 19- Binh dau; 20- Moc keo; 21- Xylanh dan huong; 22- Pittong-dau bua; 23- Don bom.

Gom co hai coc dan huong 4 lien ket voi day 2 duoc duc lien voi pittong 12. Khoi day pittong ty len be bua 1 va kep coc 15. Xylanh 10 truot theo hai coc dong thoi lam nhiem vu dau bua. Phia tren coc la xa ngang 7 co cap treo 8, moc khoi dong 6 va don dieu khien moc 9. Khi tha cap roi xuong doc theo hai coc dan, moc 6 tu dong moc vao chot 5, sau do nang ca xa ngang va xylanh den vi tri tren cung. Giat don 9, chot 5 truot khoi moc 6, xylanh 10 roi tu do theo hai coc dan huong chup vao pittong 12 de dong coc va nen khong khi trong buong xylanh. Khi dat toi ap suat va nhiet do cao, dong thoi chot 11 danh vao don 14, dau duoc phun vao trong buong xy lanh duoi dang suong mu, gap khong khi o nhiet do va ap suat cao tu boc chay (no) sinh ra ap luc lon day tung xylanh len. Khi het da, xylanh - dau bua lai roi xuong tiep tuc nen khi, dong coc, no... Loai bua nay co nang luong tuong doi thap chi phu hop voi dat yeu.

c. Bua dong coc diesel ong dan (h.6-3b):

Gom co phan va dap la pittong - dau bua 22 truot trong xylanh dan huong 21. Phan be 17 nam trong xylanh co lo lom hinh ban cau. Pittong 22 lam nhiem vu dau bua, phia tren co bo phan boi tron tu dong, phia duoi co phan loi ra hinh cau tuong ung voi phan lom o be 17. Bua duoc dinh tam voi coc boi dinh vau 16. Khi khoi dong, cap 8 keo moc 20 dua dau bua

len cao, sau do tha cho pittong 22 roi tu do doc theo xylanh; pittong ep vao don bom 23, mo bom 14 lam dau tu binh dau 19 duoc bom vao xylanh hoa tron voi khong khi chay vao phan lom cua be 17.

Pittong tiep tuc di xuong che kin lo thoat khi 18 lam khong khi bi nen toi ap suat va nhiet do cao. Khi phan lom cua he bua 17 thi thuc hien dong coc dong thoi lam cho dau ban tung toe duoi dang suong mu gap khong khi co ap suat va nhiet do cao no tu boc chay day tung pittong len. Khi chaytrong xylanh duoc thoat ra ngoai qua lo 18. Khi pittong het da thi no tu roi xuong va tiep tuc mot chu ky lam viec moi, moi lan pittong roi la mot lan coc duoc dong sau vao trong nen dat. Qua trinh lam viec cua bua diesel loai ong dan duoc the hien tren hinh 6-4.

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