Keys(键)

 Functions of keys(键的用途)

A key joint is a removable joint as shown in Fig.7-36. It goes through the shaft and the hub's keyway, joining the shaft with the rotors (gears,pulleys and a clutch), and transferring torques.

如图7-36所示,键联接是一种可拆联接。这种联接是将键同时嵌入轴与轮毂的键槽中,将轴及轴上的转动零件如齿轮、带轮、联轴器等联接在一起,以传递转矩。

Types of keys(键的种类)

Commonly used keys are square and rectangular keys,, woodruff keys—Normal form and taper keys for general use (see Fig. 7-37). One should select appropriate keys according to their features during the design process.

常用的键有普通型平键、普通型半圆键和普通型楔键,如图7-37所示。设计时可根据其特点合理选用。

Marks of keys(键的标记)

The square and rectangular keys, woodruff keys and taper keys for general use are standard components. You can purchase them according to their marks.Key marks generally include: 

普通型平键、普通型半圆键和普通型楔键都是标准件,使用时按其标记直接外购即可。键的完整标记通式为:

Table 7-7 lists the types and specified symbols of commonly used keys.

表7-7列出了常用键的形式和规定标记。

Drawing of key joints(键联接的画法)

Drawings of square and rectangular key, woodruff key-normal form and taper keys for general use are shown in Fig.7-38 and 7-39. If the cut is longitudinal, it is drawn without section lines.If the cut is cross sectional, section lines is required.

普通型平键、半圆键和普通型楔键联接的画法如图7-38、7-39所示。当沿着键的纵向剖切时,按不剖画;当沿着键的横向剖切时,则要画上剖面线。

Generally, the depth of the keyway and its union with other components are conveyed by local sectional views. Both sides of the square and rectangular key and the woodruff key-normal form are working faces. The top face is not a working face. Therefore, clearance between the key and the keyway is not allowed, and you should draw a line in accordance with the interface. Clearance between the top surfaces of both the key and the hub keyway should be maintained. 

通常用局部剖视图表示轴上键槽深度及与其他零件之间的联接关系。普通型平键和普通型半圆键的两侧面为工作面,而顶面是非工作面,故键与键槽侧面之间不留间隙,应按接触面画一条线;而键的顶面与轮毂的键槽顶面之间应留有间隙。

The top surface of the taper keys for general use has a 1:100 slope. Drive the key into the keyway,while joining them. Since the top and bottom surfaces of the taper keys for general use are working faces, there is no clearance between them and the bottom of the keyway. The two sides of the key are not working faces. Clearance should be maintained between them and the two sides of the keyway. See Fig. 7-39.

普通型楔键顶面有1100的斜度。连接时将键打入键槽。普通型楔键的顶面和底面同为工作面,与槽底没有间隙。而键的两侧为非工作面,与键槽两侧面应留有间隙,如图7-39所示。

 Choosing  dimensions of the key and keyway(键的选取和键槽尺寸的确定)

One usually first selects the type and specifications of a key according to the diameter of the axis and relevant design requirements of the standard to be used. An appropriate mark symbol is then determined. The dimension of the keyway should be determined following relevant standards.Detailed information on dimensions is provided in appendix table 2-12 to table 2-14,in the appendices.

根据轴径的大小和有关设计要求,按标准选取键的类型和规格,并给出正确的标记。键槽的尺寸也必须按标准确定。具体尺寸系列见附录表2-12~表2-14。

The keyway on the hub is generally machined on a machine with a slotting cutter. The keyway on the shaft is generally machined on a milling machine. The dimension of the keyway coincides with the dimension of the key. The depth of the keyway should be determined according to the relevant standards. The machining methods for the keyway and the relevant dimensions are shown in Fig. 7-40.

轮毂上的键槽一般是用插刀在插床上加工出来的,轴上的键槽一般是在铣床上加工出来的。键槽的尺寸应与键的尺寸一致,键槽的深度要按标准查表确定。键槽的加工方法和有关尺寸如图7-40所示。