CN105697373A

CN105697373A - Screw of screw vacuum pump

Info

Publication number: CN105697373A
Application number: CN201610121074.XA
Authority: CN
Inventors: 巫修海; 马云芳; 张宝夫
Original assignee: Taizhou Vocational and Technical College
Current assignee: Taizhou Huanqiu Vacuum Equipment Manufacture Co Ltd
Priority date: 2014-11-25
Filing date: 2014-11-25
Publication date: 2016-06-22
Anticipated expiration: 2034-11-25
Also published as: CN104454523A; CN105697373B; CN104454523B

Abstract

The invention provides a screw of a screw vacuum pump, which belongs to the technical field of vacuum pumps. It solves the problem of too long heating time of the existing screw vacuum pump. The screw of the screw vacuum pump includes a cylindrical rod body, a spiral groove is formed on the outer surface of the rod body, and the number of turns of the spiral groove on the transition part of the curved surface is 0.04 to 0.375 turns. Compared with the prior art, the vacuum pump adopting the variable-pitch screw can shorten the heat-up time by at least 40% through a large number of tests. The suction part and the exhaust part are connected by a curved surface transition part, so that the spiral groove on the suction part and the spiral groove on the exhaust part transition smoothly, which can not only make the screw easier to manufacture, but also effectively ensure the stable operation of the vacuum pump sex. At the same time, the length of the compression transition part is greatly shortened, and the length of the screw can be shortened without reducing the total number of turns of the screw, thereby making the volume of the vacuum pump smaller.

Description

The screw of a screw vacuum pump

技术领域technical field

本发明属于真空泵技术领域，涉及一种螺杆真空泵，特别是一种螺杆真空泵的螺杆。The invention belongs to the technical field of vacuum pumps, and relates to a screw vacuum pump, in particular to a screw of the screw vacuum pump.

背景技术Background technique

螺杆真空泵具有维护周期长且方便、环保、高度可靠、高效率和容易操控等优点，因而在很多工艺参合，螺杆真空泵取代水环真空泵、滑阀真空泵、其它湿式真空泵成为必然趋势。Screw vacuum pumps have the advantages of long maintenance period and convenience, environmental protection, high reliability, high efficiency and easy control. Therefore, in many processes, screw vacuum pumps have become an inevitable trend to replace water ring vacuum pumps, slide valve vacuum pumps, and other wet vacuum pumps.

申请人曾提出了一种干式螺杆真空泵变螺距螺杆，并记载在中国专利文献中(申请公布号：CN102937094A)，采用该螺杆的真空泵相对与之前的真空泵提供了能量需求、噪声、内部工作温度、结构空间以及制造费用的最佳选择，还具有应用领域较为广泛的优点。在实际生产中，客户认为上述真空泵的热机时间过长，影响生产效率，进而申请人希望能缩短热机时间。The applicant once proposed a dry-type screw vacuum pump with a variable pitch screw, which was recorded in the Chinese patent literature (application publication number: CN102937094A). Compared with the previous vacuum pump, the vacuum pump using this screw provides energy demand, noise, and internal working temperature. , structural space and manufacturing costs, and also has the advantages of a wide range of applications. In actual production, the customer thinks that the warm-up time of the above-mentioned vacuum pump is too long, which affects the production efficiency, and the applicant hopes to shorten the warm-up time.

发明内容Contents of the invention

本发明提出了一种螺杆真空泵的螺杆，本发明要解决的技术问题是如何缩短螺杆真空泵的热机时间。The invention proposes a screw of a screw vacuum pump, and the technical problem to be solved by the invention is how to shorten the heat-up time of the screw vacuum pump.

本发明的要解决的技术问题可通过下列技术方案来实现：The technical problem to be solved in the present invention can be realized through the following technical solutions:

本螺杆真空泵的螺杆，包括呈圆柱状的杆体，杆体的外侧面上开有一条螺旋槽，螺旋槽的两端口分别位于杆体的两端面上，杆体的一端部为吸气部，另一端部为排气部，吸气部上螺旋槽的螺距不变，排气部上螺旋槽的螺距不变，排气部上螺旋槽的螺距小于吸气部上螺旋槽的螺距；吸气部与排气部之间具有曲面过渡部；曲面过渡部上螺旋槽一端与吸气部上螺旋槽相接，另一端与排气部上螺旋槽相接，曲面过渡部上螺旋槽从一端到另一端螺距非线性逐渐缩小；曲面过渡部上螺旋槽的圈数为0.04～0.375圈。The screw of the screw vacuum pump includes a cylindrical rod body. There is a spiral groove on the outer surface of the rod body. The two ports of the spiral groove are respectively located on the two ends of the rod body. Exhaust part, the pitch of the spiral groove on the suction part is constant, the pitch of the spiral groove on the exhaust part is constant, the pitch of the spiral groove on the exhaust part is smaller than the pitch of the spiral groove on the suction part; the suction part and the exhaust There is a curved surface transition part between the parts; one end of the spiral groove on the curved surface transition part is connected with the upper spiral groove of the suction part, and the other end is connected with the upper spiral groove of the exhaust part, and the spiral groove on the curved surface transition part is from one end to the other. The linear gradually shrinks; the number of turns of the spiral groove on the transition part of the curved surface is 0.04 to 0.375 turns.

本螺杆真空泵的螺杆的吸气部和排气部之间通过较小螺旋角度的曲面过渡部相连；大幅度地缩短了热通道长度；进而有效地缩短了热机时间。The suction part and exhaust part of the screw of the screw vacuum pump are connected by a curved surface transition part with a small helix angle; the length of the hot channel is greatly shortened; and the heat-up time is effectively shortened.

本螺杆真空泵的螺杆为一体式结构，采用金属锻造圆棒加工而成，避免了铸造加工而成的螺杆存在的造成材质不均、有孔和疏松等问题。同时还避免了分体制造而造成制造难度和装配难度高、精度难保证及间隙难控制等问题。The screw of the screw vacuum pump has an integrated structure, which is processed by metal forging round rods, which avoids the problems of uneven material, holes and looseness caused by the screw rods processed by casting. At the same time, problems such as high difficulty in manufacturing and assembly, difficulty in ensuring precision, and difficulty in controlling gaps caused by separate manufacturing are avoided.

在上述的螺杆真空泵的螺杆中，所述曲面过渡部上螺旋槽包缠曲线非线性变化规律符合下式：In the above-mentioned screw of the screw vacuum pump, the non-linear change law of the wrapping curve of the spiral groove on the transition part of the curved surface conforms to the following formula:

$f f ((t t)) = = {cpt cpt}_{11} + + {t t}_{22} [[c c p p ((\frac{t t}{{t t}_{22}} - - \frac{{t t}_{11}}{{t t}_{22}})) - - \frac{((c c - - 11)) p p {((\frac{t t}{{t t}_{22}} - - \frac{{t t}_{11}}{{t t}_{22}}))}^{33}}{22} + + \frac{((c c - - 11)) p p {((\frac{t t}{{t t}_{22}} - - \frac{{t t}_{11}}{{t t}_{22}}))}^{33} ((\frac{t t}{{t t}_{22}} - - \frac{{t t}_{11}}{{t t}_{22}} - - 11))}{22}]],, {t t}_{11} \leq \leq t t \leq \leq {t t}_{11} + + {t t}_{22};;$

其中：t为杆体上螺旋槽的缠绕圈数；t₁为吸气部上螺旋槽的圈数；t₂为曲面过渡部上螺旋槽的圈数；c为干式螺杆真空泵的整体压缩比；p₁为进气部上螺旋槽的螺距；p为排气部上螺旋槽的螺距。Among them: t is the number of winding turns of the spiral groove on the rod body; _t1 is the number of turns of the spiral groove on the suction part; _t2 is the number of turns of the spiral groove on the curved surface transition part; c is the overall compression ratio of the dry screw vacuum pump; p ₁ is the pitch of the helical groove on the intake part; p is the pitch of the helical groove on the exhaust part.

在上述的螺杆真空泵的螺杆中，所述曲面过渡部上螺旋槽螺距非线性变化规律符合下式：In the screw of the above-mentioned screw vacuum pump, the non-linear variation law of the pitch of the helical groove on the transition part of the curved surface conforms to the following formula:

$\begin{matrix} {f f}^{' '} ((t t)) = = c c p p - - \frac{33 ((c c - - 11)) p p {((\frac{t t}{{t t}_{22}} - - \frac{{t t}_{11}}{{t t}_{22}}))}^{33}}{22} + + \frac{33 ((c c - - 11)) p p {((\frac{t t}{{t t}_{22}} - - \frac{{t t}_{11}}{{t t}_{22}}))}^{22} ((\frac{t t}{{t t}_{22}} - - \frac{{t t}_{11}}{{t t}_{22}} - - 11))}{22} + + \frac{((c c - - 11)) p p {((\frac{t t}{{t t}_{22}} - - \frac{{t t}_{11}}{{t t}_{22}}))}^{33}}{22},, \\ {t t}_{11} \leq \leq t t \leq \leq {t t}_{11} + + {t t}_{22};; \end{matrix}$

曲面过渡部上螺旋槽包缠曲线非线性变化规律和曲面过渡部上螺旋槽螺距非线性变化规律还可采用下述方案替换：所述曲面过渡部上螺旋槽包缠曲线非线性变化规律符合下式：The non-linear variation law of the wrapping curve of the spiral groove on the transition part of the curved surface and the nonlinear variation law of the pitch of the helical groove on the transition part of the curved surface can also be replaced by the following scheme: the non-linear variation law of the wrapping curve of the helical groove on the transition part of the curved surface conforms to the following Mode:

$f f ((t t)) = = {cpt cpt}_{11} + + \frac{c c + + 11}{22} p p ((t t - - {t t}_{11})) + + \frac{{t t}_{22}}{π π} \frac{((c c - - 11)) p p}{22} s the s i i n no ((\frac{π π}{{t t}_{22}} t t - - \frac{{πt πt}_{11}}{{t t}_{22}})),, {t t}_{11} \leq \leq t t \leq \leq {t t}_{11} + + {t t}_{22};;$

在上述的干式螺杆真空泵变螺距螺杆中，所述曲面过渡部上螺旋槽螺距非线性变化规律符合下式：In the variable-pitch screw of the above-mentioned dry screw vacuum pump, the non-linear change law of the pitch of the helical groove on the transition part of the curved surface conforms to the following formula:

${f f}^{' '} ((t t)) = = \frac{c c + + 11}{22} p p + + \frac{((c c - - 11)) p p}{22} c c o o s the s ((\frac{π π}{{t t}_{22}} t t - - \frac{{πt πt}_{11}}{{t t}_{22}})),, {t t}_{11} \leq \leq t t \leq \leq {t t}_{11} + + {t t}_{22};;$

在上述的螺杆真空泵的螺杆中，所述杆体上螺旋槽的螺旋总圈数大于等于5圈，吸气部上螺旋槽的缠绕圈数为1～3圈。In the above-mentioned screw of the screw vacuum pump, the total number of helical turns of the helical groove on the rod body is greater than or equal to 5 turns, and the number of winding turns of the helical groove on the suction part is 1-3 turns.

采用本变螺距螺杆的真空泵通过大量的试验证实与现有技术相比至少能缩短热机时间40％以上。Compared with the prior art, the vacuum pump adopting the variable-pitch screw can shorten the heat-up time by at least 40% through a large number of tests.

吸气部和排气部之间通过曲面过渡部相连，使吸气部上的螺旋槽和排气部上的螺旋槽平缓过渡，既能使螺杆更容易制造，又有效地保证真空泵运行的稳定性。同时大幅度地缩短了曲面过渡部的长度，在不减少螺杆螺旋总圈数的情况，能缩短螺杆的长度，进而能使真空泵体积更小。The suction part and the exhaust part are connected by a curved surface transition part, so that the spiral groove on the suction part and the spiral groove on the exhaust part transition smoothly, which can not only make the screw easier to manufacture, but also effectively ensure the stable operation of the vacuum pump sex. At the same time, the length of the transition portion of the curved surface is greatly shortened, and the length of the screw can be shortened without reducing the total number of turns of the screw, thereby making the volume of the vacuum pump smaller.

附图说明Description of drawings

图1是本螺杆真空泵的螺杆的结构示意图。Fig. 1 is a structural schematic diagram of the screw of the screw vacuum pump.

图2是本螺杆真空泵的螺杆的轴向位置与缠绕圈数的关系变化示意图。Fig. 2 is a schematic diagram of the relationship between the axial position of the screw of the screw vacuum pump and the number of winding turns.

图3是本螺杆真空泵的螺杆的螺距与缠绕圈数的关系变化示意图。Fig. 3 is a schematic diagram of the relationship between the pitch of the screw and the number of winding turns of the screw vacuum pump.

图中，1、杆体；2、螺旋槽；3、吸气部；4、曲面过渡部；5、排气部。In the figure, 1. Rod body; 2. Spiral groove; 3. Suction part; 4. Surface transition part; 5. Exhaust part.

具体实施方式detailed description

以下是本发明的具体实施例并结合附图，对本发明的技术方案作进一步的描述，但本发明并不限于这些实施例。The following are specific embodiments of the present invention and in conjunction with the accompanying drawings, further describe the technical solution of the present invention, but the present invention is not limited to these embodiments.

如图1所示，本螺杆真空泵的螺杆包括呈圆柱状的杆体1，杆体1的外侧面上开有一条螺旋槽2，螺旋槽2的两端口分别位于杆体1的两端面上，杆体1的一端部为吸气部3，另一端部为排气部5，吸气部3上螺旋槽2的螺距不变，排气部5上螺旋槽2的螺距不变，排气部5上螺旋槽2的螺距小于吸气部3上螺旋槽2的螺距；吸气部3与排气部5之间具有曲面过渡部4；曲面过渡部4上螺旋槽2一端与吸气部3上螺旋槽2相接，另一端与排气部5上螺旋槽2相接，曲面过渡部4上螺旋槽2从一端到另一端螺距非线性逐渐缩小。As shown in Figure 1, the screw of the screw vacuum pump includes a cylindrical rod body 1, a spiral groove 2 is opened on the outer surface of the rod body 1, and the two ports of the spiral groove 2 are respectively located on both ends of the rod body 1. One end is the suction part 3, and the other end is the exhaust part 5. The pitch of the spiral groove 2 on the suction part 3 is constant, the pitch of the spiral groove 2 on the exhaust part 5 is constant, and the spiral groove on the exhaust part 5 is constant. The pitch of 2 is smaller than the pitch of the spiral groove 2 on the suction part 3; there is a curved surface transition part 4 between the suction part 3 and the exhaust part 5; one end of the spiral groove 2 on the curved surface transition part 4 is connected to the spiral groove 2 on the suction part 3 The other end is in contact with the helical groove 2 on the exhaust part 5, and the helical groove 2 on the curved surface transition part 4 gradually decreases in pitch non-linearly from one end to the other end.

本螺杆真空泵的螺杆为一体式结构，采用金属锻造圆棒加工而成。The screw of the screw vacuum pump has an integrated structure, which is processed by metal forging round rods.

杆体1上螺旋槽的螺旋总圈数为5圈，吸气部3上螺旋槽2的缠绕圈数为1圈；曲面过渡部4上螺旋槽2的圈数为0.04圈；排气部5上螺旋槽2的缠绕圈数为3.96圈。The total number of spiral turns of the spiral groove on the rod body 1 is 5 turns, the number of turns of the spiral groove 2 on the suction part 3 is 1 turn; the number of turns of the spiral groove 2 on the curved surface transition part 4 is 0.04 turns; The number of winding turns of the spiral groove 2 is 3.96 turns.

图2中的w表示螺杆的长度，t表示杆体1上螺旋槽2的缠绕圈数。曲面过渡部4上螺旋槽2包缠曲线非线性变化规律符合下式：W in FIG. 2 represents the length of the screw rod, and t represents the number of turns of the helical groove 2 on the rod body 1 . The nonlinear change law of the wrapping curve of the spiral groove 2 on the surface transition part 4 conforms to the following formula:

$\begin{matrix} f f ((t t)) = = c c p p + + 0.04 0.04 \times \times [[c c p p ((2525 t t - - 2525)) - - \frac{((c c - - 11)) p p {((2525 t t - - 2525))}^{33}}{22} + + \frac{((c c - - 11)) p p {((2525 t t - - 2525))}^{33} ((2525 t t - - 2626))}{22}]],, \\ 11 \leq \leq t t \leq \leq 1.04 1.04;; \end{matrix}$

其中：c为干式螺杆真空泵的整体压缩比，即p₁为进气部上螺旋槽2的螺距；p为排气部5上螺旋槽2的螺距；作为优选1.5≤c≤10。Where: c is the overall compression ratio of the dry screw vacuum pump, namely p ₁ is the pitch of the helical groove 2 on the intake part; p is the pitch of the helical groove 2 on the exhaust part 5; preferably 1.5≤c≤10.

如图3所示，图3中的w’表示螺旋槽2的螺距，t表示杆体1上螺旋槽2的缠绕圈数。曲面过渡部4上螺旋槽2螺距非线性变化规律符合下式：As shown in Figure 3, w' in Figure 3 represents the pitch of the helical groove 2, and t represents the number of turns of the helical groove 2 on the rod body 1. The non-linear variation law of the pitch of the helical groove 2 on the curved surface transition part 4 conforms to the following formula:

$\begin{matrix} {f f}^{' '} ((t t)) = = c c p p - - \frac{33 ((c c - - 11)) p p {((2525 t t - - 2525))}^{22}}{22} + + \frac{33 ((c c - - 11)) p p {((2525 t t - - 2525))}^{22} ((2525 t t - - 2626))}{22} + + \frac{((c c - - 11)) p p {((2525 t t - - 2525))}^{33}}{22},, \\ 11 \leq \leq t t \leq \leq 1.04 1.04;; \end{matrix}$

其中：c为干式螺杆真空泵的整体压缩比，即p₁为进气部上螺旋槽2的螺距；p为排气部5上螺旋槽2的螺距。Where: c is the overall compression ratio of the dry screw vacuum pump, namely p ₁ is the pitch of the helical groove 2 on the intake part; p is the pitch of the helical groove 2 on the exhaust part 5 .

实施例二Embodiment two

本实施例同实施例一的结构及原理基本相同，不一样的地方在于：杆体1上螺旋槽的螺旋总圈数为6圈；吸气部3上螺旋槽2的缠绕圈数为1.5圈；曲面过渡部4上螺旋槽2的圈数为0.25圈；排气部5上螺旋槽2的缠绕圈数为4.25圈。The structure and principle of this embodiment are basically the same as that of Embodiment 1, except that: the total number of spiral turns of the spiral groove on the rod body 1 is 6 turns; the number of winding turns of the spiral groove 2 on the suction part 3 is 1.5 turns; The number of turns of the spiral groove 2 on the curved surface transition part 4 is 0.25 turns; the number of turns of the spiral groove 2 on the exhaust part 5 is 4.25 turns.

曲面过渡部4上螺旋槽2包缠曲线非线性变化规律符合下式：The non-linear change law of the wrapping curve of the spiral groove 2 on the surface transition part 4 conforms to the following formula:

$f f ((t t)) = = 1.5 1.5 c c p p + + 0.25 0.25 \times \times [[c c p p ((44 t t - - 66)) - - \frac{((c c - - 11)) p p {((44 t t - - 66))}^{33}}{22} + + \frac{((c c - - 11)) p p {((44 t t - - 66))}^{33} ((44 t t - - 77))}{22}]],, 1.5 1.5 \leq \leq t t \leq \leq 1.75 1.75;;$

其中：t表示杆体1上螺旋槽2的缠绕圈数；c为螺杆真空泵的整体压缩比，即p₁为进气部上螺旋槽2的螺距；p为排气部5上螺旋槽2的螺距。Among them: t represents the number of winding turns of the spiral groove 2 on the rod body 1; c is the overall compression ratio of the screw vacuum pump, that is p ₁ is the pitch of the helical groove 2 on the intake part; p is the pitch of the helical groove 2 on the exhaust part 5 .

曲面过渡部4上螺旋槽2螺距非线性变化规律符合下式：The non-linear change law of the pitch of the helical groove 2 on the surface transition part 4 conforms to the following formula:

${f f}^{' '} ((t t)) = = c c p p - - \frac{33 ((c c - - 11)) p p {((44 t t - - 66))}^{22}}{22} + + \frac{33 ((c c - - 11)) p p {((44 t t - - 66))}^{22} ((44 t t - - 77))}{22} + + \frac{((c c - - 11)) p p {((44 t t - - 66))}^{33}}{22},, 1.5 1.5 \leq \leq t t \leq \leq 1.75 1.75;;$

实施例三Embodiment Three

本实施例同实施例一的结构及原理基本相同，不一样的地方在于：杆体1上螺旋槽的螺旋总圈数为7圈；吸气部3上螺旋槽2的缠绕圈数为2圈。曲面过渡部4上螺旋槽2的圈数为0.375圈。排气部5上螺旋槽2的缠绕圈数为4.625圈。The structure and principle of this embodiment are basically the same as those of Embodiment 1, except that: the total number of helical turns of the helical groove on the rod body 1 is 7; the number of winding turns of the helical groove 2 on the suction part 3 is 2 turns. The number of turns of the spiral groove 2 on the curved surface transition portion 4 is 0.375 turns. The number of turns of the spiral groove 2 on the exhaust part 5 is 4.625 turns.

曲面过渡部4上螺旋槽2包缠曲线非线性变化规律符合下式：The nonlinear change law of the wrapping curve of the spiral groove 2 on the surface transition part 4 conforms to the following formula:

$\begin{matrix} f f ((t t)) = = 22 c c p p + + 0.375 0.375 \times \times [[c c p p ((\frac{t t - - 22}{0.375 0.375})) - - \frac{((c c - - 11)) p p {((\frac{t t - - 22}{0.375 0.375}))}^{33}}{22} + + \frac{((c c - - 11)) p p {((\frac{t t - - 22}{0.375 0.375}))}^{33} ((\frac{t t - - 22}{0.375 0.375} - - 11))}{22}]],, \\ 22 \leq \leq t t \leq \leq 2.375 2.375;; \end{matrix}$

${f f}^{' '} ((t t)) = = c c p p - - \frac{33 ((c c - - 11)) p p {((\frac{t t - - 22}{0.375 0.375}))}^{22}}{22} + + \frac{33 ((c c - - 11)) p p {((\frac{t t - - 22}{0.375 0.375}))}^{22} ((\frac{t t - - 22}{0.375 0.375} - - 11))}{22} + + \frac{((c c - - 11)) p p {((\frac{t t - - 22}{0.375 0.375}))}^{33}}{22},,$

其中：t表示杆体1上螺旋槽2的缠绕圈数；c为螺杆真空泵的整体压缩比，即p₁为进气部上螺旋槽2的螺距；p为排气部5上螺旋槽2的螺距。 Among them: t represents the number of winding turns of the spiral groove 2 on the rod body 1; c is the overall compression ratio of the screw vacuum pump, that is p ₁ is the pitch of the helical groove 2 on the intake part; p is the pitch of the helical groove 2 on the exhaust part 5 .

实施例四Embodiment Four

本实施例同实施例三的结构及原理基本相同，不一样的地方在于：曲面过渡部4上螺旋槽2包缠曲线非线性变化规律符合下式：The structure and principle of this embodiment are basically the same as those of Embodiment 3, except that the non-linear change law of the wrapping curve of the spiral groove 2 on the curved surface transition part 4 conforms to the following formula:

$f f ((t t)) = = 22 c c p p + + \frac{c c + + 11}{22} p p ((t t - - 22)) + + 0.375 0.375 \frac{((c c - - 11)) p p}{22} s the s i i n no ((\frac{π π}{0.375 0.375} t t - - \frac{22 π π}{0.375 0.375})),, 22 \leq \leq t t \leq \leq 2.375 2.375;;$

其中：t表示杆体1上螺旋槽2的缠绕圈数；c为螺杆真空泵的整体压缩比；p为排气部5上螺旋槽2的螺距；Among them: t represents the number of winding turns of the helical groove 2 on the rod body 1; c is the overall compression ratio of the screw vacuum pump; p is the pitch of the helical groove 2 on the exhaust part 5;

${f f}^{' '} ((t t)) = = \frac{c c + + 11}{22} p p + + \frac{((c c - - 11)) p p}{22} c c o o s the s ((\frac{π π}{0.375 0.375} t t - - \frac{22 π π}{0.375 0.375})),, 22 \leq \leq t t \leq \leq 2.375 2.375;;$

Claims

1. the screw rod of a screw vacuum pump, including the cylindrical body of rod (1), the lateral surface of the body of rod (1) has a helicla flute (2), the two-port of helicla flute (2) lays respectively in the both ends of the surface of the body of rod (1), the one end of the body of rod (1) is suction unit (3), the other end is exhaust portion (5), the pitch of the upper helicla flute (2) of suction unit (3) is constant, the pitch of the upper helicla flute (2) of exhaust portion (5) is constant, the pitch of the upper helicla flute (2) of exhaust portion (5) is less than the pitch of the upper helicla flute (2) of suction unit (3)；There is between suction unit (3) and exhaust portion (5) surface blending portion (4)；Upper helicla flute (2) one end, surface blending portion (4) connects with the upper helicla flute (2) of suction unit (3), the other end connects with the upper helicla flute (2) of exhaust portion (5), and surface blending portion (4) upper helicla flute (2) passes through, and pitch is non-linear gradual to be reduced；It is characterized in that, the number of turns of surface blending portion (4) upper helicla flute (2) is 0.04～0.375 circle；Upper helicla flute (2) the looping curve non-linear change tendencies of described surface blending portion (4) meets following formula:

f (t) = {cpt}_{1} + \frac{c + 1}{2} p (t - t_{1}) + \frac{t_{2}}{π} \frac{(c - 1) p}{2} s i n (\frac{π}{t_{2}} t - \frac{{πt}_{1}}{t_{2}}), t_{1} \leq t \leq t_{1} + t_{2};

Wherein: t is the winding number of turns of the upper helicla flute (2) of the body of rod (1)；T₁The number of turns for the upper helicla flute (2) of suction unit (3)；T₂The number of turns for surface blending portion (4) upper helicla flute (2)；C is the reduced overall ratio of dry screw vacuum pump；p₁Pitch for helicla flute on intake section (2)；P is the pitch of the upper helicla flute (2) of exhaust portion (5)。

2. the screw rod of screw vacuum pump according to claim 1, it is characterised in that the screw rod of this screw vacuum pump is integral type structure, adopts metal forging pole to process。

3. the screw rod of screw vacuum pump according to claim 1, it is characterised in that upper helicla flute (2) the pitch non-linear change tendencies of described surface blending portion (4) meets following formula:

f^{'} (t) = \frac{c + 1}{2} p + \frac{(c - 1) p}{2} c o s (\frac{π}{t_{2}} t - \frac{{πt}_{1}}{t_{2}}), t_{1} \leq t \leq t_{1} + t_{2};

4. the screw rod of the screw vacuum pump according to any one in claims 1 to 3, it is characterized in that, the spiral number of total coils of the upper helicla flute (2) of the body of rod (1) encloses be more than or equal to 5, and the winding number of turns of the upper helicla flute (2) of suction unit (3) is 1～3 circle。