JPS61123797A - High vacuum exhaust equipment - Google Patents

Abstract

PURPOSE:To increase pressure ratio and exhaust volume by making the capacity of molecular pumps and the blade angle of disks bigger as they are closer to the air suction side and making both of them smaller as they are closer to the exhaust side. CONSTITUTION:In a high vacuum exhaust equipment having plural stages of molecular pumps 21 and connecting pipes 23, the number of molecular pumps 21 is largest at the side of a suction opening 24 and is getting smaller as they become closer to an exhaust opening 25. Also, the blade angle of disks is getting bigger as they are located closer to the suction opening 24 from the exhaust opening 25. Under this arrangement, pressure ratio and exhaust volume can be increased. Since disks can be of the same size, it is possible to mass-produce them and eventually reduce their production cost.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention has a multi-stage molecular pump in which the exhaust port and intake port of each adjacent stage are connected by a single header, and each molecular pump has a large This invention relates to a high vacuum evacuation device that obtains a high vacuum by evacuation of a volume.

(Prior art) A conventional molecular pump will be explained with reference to FIGS. 4 and 5.
) is the rotor, (2) is the casing, (3) is the rotor attached to the rotor (1), and (4) is the casing (2).
), (5) is a bearing that rotatably supports the rotor (1), (6) is a motor that rotates the rotor (1), and (7) is installed on the rotor (1). (8) is an exhaust port provided on the rotor (1), and the rotor (3) is composed of a large number of vanes having angles of attack with respect to nine rotational directions. Further, the stationary impeller (4) is composed of a large number of vanes having a blade angle opposite to that of the cooperating impeller (3). The same molecular pump.

Due to the rotation of the rotor (1), gas molecules are pushed in one direction due to the deviation in molecular motion caused by the inclination angles of the rotor (3) and stationary rotor (4). As a result, a flow is generated from the intake air a (7) to the exhaust port (8), and exhaust is performed. The relationship between the blade angle (α) of the impeller and the exhaust characteristics is shown in Figures 6 and 7.

In FIG. 6, QmaX is the theoretical maximum exhaust and air velocity efficiency, and is an index of the volumetric flow rate that can flow. Also(
Pz/Pt)-X is.

This is the theoretical maximum pressure ratio before and after the impeller. Also, ω is 1 mouth (
1) is the rotation speed. As is clear from Fig. 6.7, the smaller the blade angle (α) of the impeller, the greater the pressure reduction effect, and, conversely, the smaller the exhaust capacity (volume flow rate). However, Q
max has a peak value with respect to the blade angle. In the same molecular pump.

Considering the relationship between blade angle and exhaust characteristics, low pressure side (intake side)
In this case, the blade angle is designed to be large in order to maximize the exhaust volume flow rate, and the blade angle is designed to be small on the high pressure side (exhaust side) to increase the pressure reduction effect.

(Problems to be Solved by the Invention) The pressure ratio between the exhaust side and the intake side of the molecular pump is generally given by the product of the membrane pressure ratios.

It is normal for it to be 10' or more. On the other hand.

Since the exhaust mass flow rate is given by the product of the pressure of each stage and the pumping speed efficiency (constant for all stages), it is suppressed at the maximum pumping speed efficiency on the lowest pressure side (intake side). Even if the blade angle of the impeller on the intake side is maximized within the limit, the maximum exhaust speed efficiency Qmax
can only be increased by about 10 times at most (see Figure 6), so the pumping speed efficiency on the high overwhelm (exhaust side) will take a value significantly smaller than its maximum capacity value (Qmax), and the high pressure of the equipment This means that the exhaust capacity of the side portions is hardly used effectively. In particular, when a plurality of molecular pumps are used to perform large-capacity evacuation, or when a large-sized molecular pump is manufactured, the evacuation capacity of the high-pressure side portion is not used effectively, and the efficiency of the device is significantly reduced.

(Means for Solving the Problems) The present invention addresses the above-mentioned problems, and includes a multi-stage molecular pump in which the exhaust port and intake port of each adjacent stage are connected by one header. In the high vacuum evacuation system that generates a high vacuum by evacuation of a large volume using each molecular pump, the capacity of the molecular pump is increased toward the most upstream suction side, and the blade angle of the impeller of the molecular pump is increased. This is a high-vacuum evacuation system that is characterized by the capacity of the molecular pump becoming smaller and the blade angle of the impeller of the molecular pump becoming smaller as it moves toward the downstream exhaust side. You can make it bigger. Another object of the present invention is to provide an improved high vacuum evacuation device that can reduce manufacturing costs.

(Example) Next, the high vacuum evacuation device of the present invention will be explained using an example shown in Figures 1.2.3. (21) is a multi-stage molecular pump, (22) is a molecular pump at each stage (21) (23) is the header for each stage (
22), (24) is the most upstream intake port of the main high vacuum evacuation device, (25) is the most downstream exhaust port of the main high vacuum evacuation device, (26) is the shaft and bearing (28) (27) is a stator vane wheel fixed to the equipment side, and the number of monomolecular pumps (21) is 5, which is the largest on the intake port (24) side of the high vacuum pumping equipment. , decreases toward the exhaust port (25). In addition, if the diameter of the molecular pump (21) is made larger toward the most upstream intake port (24) of the high vacuum evacuation device, a triple molecular pump (21) can be obtained.
21) There is no need to increase the number of units. In addition, the blade angle of the impeller is five, from the exhaust port (25) side of the high vacuum exhaust system to the intake port (25) side.
4) It gets bigger towards the side. Note that the blade angle of the impeller may have the same tendency in the molecular pump (21) having the same role.

(Function) Next, the function of the high vacuum evacuation device will be explained. Intake port (2
4) Due to the large pumping velocity efficiency and large pumping area, a large flow rate of high vacuum air molecules are sucked in and flowed downstream. The blade angle of the molecular pump (21) becomes smaller as the high-vacuum air molecules move toward the downstream side, so the pressure ratio becomes larger. Further, since the pressure of the same high-vacuum air molecules increases as they go downstream, they flow in balance with the upstream side (intake side) even with a small number of molecular pumps (21) or a small capacity molecular pump (21). The pumping speed efficiency at this time is sufficiently achieved by the ability of the impeller of the molecular pump (21) with a small blade angle.

(Effects of the Invention) As described above, the present invention connects the exhaust port and intake port of each adjacent stage to one
It has a multi-stage molecular pump connected by a book header,
In the high vacuum evacuation system that generates a high vacuum by evacuation of a large volume using each molecular pump, the capacity of the molecular pump is increased toward the most upstream suction side, and the blade angle of the impeller of the molecular pump is increased. The capacity of the molecular pump is made smaller toward the downstream exhaust side, and the blade angle of the impeller of the molecular pump is made smaller, and the above-mentioned effects are performed, so that the pressure ratio and the exhaust flow rate can be increased. Also, the impellers of molecular pumps in the same stage can have the same shape.

Although the present invention has been described with reference to embodiments as it can be mass-produced and has the effect of reducing manufacturing costs, it goes without saying that the present invention is not limited to such embodiments and can be modified without departing from the spirit of the present invention. It is a model with various design modifications.

[Brief explanation of the drawing]

Fig. 1 is a partially longitudinal side view showing an embodiment of the high vacuum evacuation device according to the present invention, Fig. 2 is an explanatory view showing the blade angle of the impeller of the molecular pump, and Fig. 3 is a bottom view of the molecular pump. , Fig. 4 is a vertical side view of a conventional molecular pump, Fig. 5 is an explanatory diagram showing the blade angle of the impeller of the same molecular pump, Fig. 6 is an explanatory diagram showing the maximum pumping efficiency, and Fig. 7 is an explanatory diagram showing the impeller of the same molecular pump. It is an explanatory view showing the theoretical maximum pressure ratio before and after. (21)...Molecular pump, (24)...Most upstream intake port, (25)...Most downstream exhaust port,
(26) ...Rotor wheel, (27) ...Stator blade bundle. Sub-Agent Patent Attorney Okamoto, 3 people outside of Japan - Figure 4 Figure 6 mox

Claims (1)

[Claims] This is the best high-vacuum evacuation system that has multiple stages of molecular pumps in which the exhaust port and inlet of each adjacent stage are connected by a single header, and each molecular pump pumps out a large volume to achieve a high vacuum. The closer you get to the upstream intake side, the larger the capacity of the molecular pump is, and the blade angle of the impeller of the molecular pump is increased.
A high-vacuum pumping device characterized in that the capacity of the molecular pump is made smaller toward the most downstream exhaust side, and the blade angle of the impeller of the molecular pump is made smaller.