键、花键和销联接key, spline and pin joints

§12 键、花键和销联接Key, spline and pin joints §12-1 键联接Key joints
§12-2 花键联接Spline joints §12-3 销联接Pin joints
§12-4 其它联接Other joints
§12-1 键联接Key joints
¾分类Types of the key joints
¾平键联接的尺寸选择和强度计算Option of sizes and strength calculations for straight key joints
* Selection of sizes and strength & Calculations for straight key joints
一、分类Types of the key joints
Key joints Loose joints Tight joints
Straight key joints
Woodruff key joints
Ordinary straight key
joints
Guiding and sliding straight key joints
Taper key Taper key joints Tangent double-
taper key joints
1.普通平键联接Ordinary straight key joints
平键的两侧面是工作面，靠键和键槽之间的互压传递转矩。

The load is carried by the sides of straight keys. The both side surfaces of key and keyway press each other, through which the torque is transmitted.
Rounded end Square end One rounded and
one square end
2.导向平键和滑键Guiding and sliding straight key
3. 半圆键Woodruff key
4. 楔键联接Taper key joint
楔键联接上下面为工作面，靠键、轴和毂之间的摩擦力以及键受到的偏压传递扭矩。

Torque is transmitted by friction of above and below surfaces on the key, shaft and hub.
5. 切向键联接Tangent double-taper key joint
切向键的工作面是两个楔键组成矩形的窄面，工作面上的挤压力沿轴的切线方向，靠挤压传递扭矩。

Tangent double-taper key joint comprises two taper keys. The tow taper keys compose a rectangle and the small face of the rectangle is its operating surface. Torque is transmitted by the pressure between the operating surfaces of the key , shaft and hub.
二、平键联接的尺寸选择和强度计算Selection of sizes and strength calculations for straight key joints
失效形式Types of failure
⑴主要失效形式The main types of failure：
工作面压溃Crushing（静联接Fixed joints）工作面磨损Wear（动联接Sliding joints）
⑵有时：键剪断shear failure of the key（一般不作计算，重要时验算No such strength calculations are required in designing.）
工作面的压溃或磨损发生在键、轴和毂三者中较弱的零件上，一般为毂。

Crushing or wear of the operating surfaces usually take place on the elements of which the strength is weakest among the key, shaft and hub. And it usually occurs on the hub.
2. 计算公式Calculations
假设压力在键的接触长度范围内分布均匀，则根据挤压强度或耐磨性的条件性计算It is assumed that the pressure is uniformly distributed over the surfaces of contact between the sides of the key and the hub and the shaft. Then the strength conditions to resist crushing and wear respectively are：
Height of key
Allowable pressing stress
Contact height of key and hub
3. 平键联接的计算步骤
Design procedure for straight key joints
§12-2 花键联接Spline joints
依靠轴和毂上齿的互压传递转矩，可用于动联接和静联接。

The teeth of shaft and hub press each other, through which the torque is transmitted. The spline joints can be used for both fixed and sliding joints.
¾花键联接的特点Features of spline joints
¾花键联接的分类Types of spline joints
一、花键联接的特点
Features of spline joints
With respect to straight key joints:
Uniform force distribution
Less stress concentration
More accurately centered Teeth are difficult to be manufactured
二、花键联接的分类Types of spline joints
（矩形花键Rectangle spline、渐开线花键Involute spline、三角形花键Triangle spline）
三、花键的定心方式
Centering methods of spline
Major diameter fit Minor diameter fit Fit on sides of spline
矩形花键定心方式
Major diameter fit Side fit 渐开线花键定心方式
§12-3 销联接Pin joints
¾销联接的功用Functions of pin joints ¾销的分类Types of pin joints
（1）定位Locating （2）安全装置Safety device
（3）传递不大的载荷
Transmit relatively small loads 一、销联接的功用Functions of pin joints
二、销的分类Types of pin
（1）普通圆柱销Plain cylindrical pins
（多次装拆，定位精度下降
Locating precision is lowered after disassembled many time （2）普通圆锥销Plain taper pins
（锥度1：50 、自锁、可以多次装拆
With a taper of 1:50,selflocking,
may be disassembled for many times）
（3）特殊形式销Special types of pin
①孔未开通或拆卸困难时：
螺尾锥销With thread for disassembly ②冲击、振动或变载荷时：
开尾锥销、槽销或弹性圆柱销（防松）With open slot for fastening
§12-4 其它联接Other joints
¾成形联接Shaped joints
¾过盈联接Interference fit joints
¾焊接Welded joints
一、成形联接Shaped joints
二、过盈联接Interference fit joints
三、焊接Welded joints
To join (metals) by applying heat, sometimes with pressure and sometimes with an intermediate or filler metal having a high melting point.
思考题。