Cooling apparatus for vacuum pump

Abstract

A cooling apparatus, for cooling a vacuum pump, in which a cooler 44 is arranged on a rotor housing 12, a cooler 45 is arranged on a rear housing 14 and a drive unit 33, a cooler 46 is arranged on a controller 37, a cooler 47 is arranged on an inverter 38, and a cooler 48 is mounted on the peripheral surface of an electric motor M is disclosed. The coolers 46, 47, 48 are arranged midway in a main supply pipe 49. The coolers 44, 45, on the other hand, are arranged midway in a subsidiary supply pipe 50. The energization and deenergization of an electromagnetic three-way valve 51 arranged at the diverging point of the main supply pipe 49 and the subsidiary supply pipe 50 is controlled by the controller 37.

Description

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a cooling apparatus for cooling a vacuum pump, which performs a sucking operation, by the transfer operation of gas transfer member.

[0003] 2. Description of the Related Art

[0004] The vacuum pump disclosed in Japanese Unexamined Patent Publication No. 5-118290 is rotated with a pair of rotors in mesh with each other. The rotation of a plurality of rotors in mesh with each other moves an exhaust gas. Such a vacuum pump includes a cooling apparatus for removing the heat generated during the process for compressing the exhaust gas. The cooling apparatus generally cools the surface of the housing into which the rotors are built.

[0005] In the vacuum pump for driving the rotors with an electric motor, it is necessary to cool the electric motor and a controller for controlling the electric motor electrically. An attempt to cool the housing, the electric motor and the controller by a cooling apparatus having a plurality of independent coolant supply systems would make the vacuum pump bulky. The bulkiness of the vacuum pump can be suppressed by a cooling apparatus having a single coolant supply system for cooling the housing, the electric motor and the controller. In view of the fact that the cooling areas including the housing, the electric motor and the controller have different required amounts of the coolant, however, all the cooling areas cannot be properly cooled by a single coolant supply system.

SUMMARY OF THE INVENTION

[0006] The object of the present invention is to provide a cooling apparatus for properly cooling a plurality of cooling areas of a vacuum pump with a single coolant supply system.

[0007] According to a first aspect of the invention, there is provided a cooling apparatus for a vacuum pump, comprising a main coolant supply path arranged to cool at least one of a plurality of cooling areas of a vacuum pump, a subsidiary coolant supply path arranged to cool at least one of a plurality of the cooling areas by supplying the coolant from the main coolant supply path, and supply switching means for switching between the supply permit mode in which the coolant can be supplied to the subsidiary coolant supply path and the supply prohibit mode in which the coolant cannot be supplied to the subsidiary supply path.

[0008] As long as the supply switching means is in the supply permit mode, the coolant in the main supply path is supplied to the subsidiary supply path. While the supply switching means is in the supply prohibit mode, on the other hand, the coolant in the main supply path is not supplied to the subsidiary supply path. The configuration in which the supply switching means is switched between the supply permit mode and the supply prohibit mode is effective for properly cooling, with a single coolant supply system, the cooling areas cooled by supplying the coolant to the subsidiary supply path.

[0009] According to a second aspect of the invention, there is provided a cooling apparatus for a vacuum pump, further comprising switching control means for electrically switching the supply switching means between the supply permit mode and the supply prohibit mode, and temperature detection means for detecting the temperature of the subsidiary supply path or the cooling areas cooled by the coolant supplied to the subsidiary supply path, wherein the switching control means controls the supply switching means in such a manner that the temperature of the cooling areas cooled by the coolant supplied to the subsidiary supply path is converged to a predetermined temperature, based on the temperature detection information from the temperature detection means.

[0010] In the case where the temperature detected by the temperature detection means exceeds a predetermined level, the switching control means turns the supply switching means to the supply permit mode. Once the supply switching means is turned to the supply permit mode, the coolant is supplied to the subsidiary supply path, thereby decreasing the temperature of the cooling areas cooled by the coolant supplied to the subsidiary supply path. In the case where the temperature detected by the temperature detection means fails to reach a predetermined level, on the other hand, the switching control means turns the supply switching means to the supply prohibit mode. Once the supply switching means turns to the supply prohibit mode, the temperature of the cooling areas increases.

[0011] According to a third aspect of the invention, there is provided a cooling apparatus for a vacuum pump, wherein the switching control means is cooled by the coolant on the main supply path, and the switching control means is arranged upstream of the supply switching means in the main supply path.

[0012] An increase in the temperature of the switching control means for electrically controlling the supply switching means leads to a control failure. The configuration in which the switching control means is cooled upstream of the supply switching means is effective for positively avoiding the control failure which otherwise might be caused by an increased temperature of the switching control means.

[0013] According to a fourth aspect of the invention, there is provided a cooling apparatus for a vacuum pump, in which gas transfer members are driven by an electric motor which in turn is cooled by the coolant on the main supply path, and the electric motor is arranged upstream of the supply switching means in the main supply path.

[0014] An increased temperature of the electric motor shortens the service life of the electric motor. The configuration in which the electric motor is cooled upstream of the supply switching means is effective for avoiding the shortening of the service life of the electric motor which otherwise might be caused by an increased temperature of the electric motor.

[0015] The present invention may be more fully understood from the description of preferred embodiments of the invention, as set forth below, together with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In the drawings:

[0017] FIG. 1 is a plan view of a cooling apparatus for a vacuum pump according to a first embodiment of the present invention.

[0018] FIG. 2 is a sectional view of a multistage Roots pump.

[0019] FIG. 3A is a sectional view taken in line A-A in FIG. 2,

[0020] FIG. 3B a sectional view taken in line B-B in FIG. 2, and

[0021] FIG. 3C a sectional view taken in line C-C in FIG. 2.

[0022] FIG. 4 is a sectional view taken in line D-D in FIG. 1.

[0023] FIG. 5A is a control circuit diagram showing an electromagnetic three-way valve in a deenergized state, and

[0024] FIG. 5B a control circuit diagram with an electromagnetic three-way valve in an energized state.

[0025] FIG. 6 is a plan view of a cooling apparatus for a vacuum pump according to a second embodiment of the invention.

[0026] FIG. 7A is a control circuit diagram showing an electromagnetic valve in a deenergized state, and

[0027] FIG. 7B a control circuit diagram with an electromagnetic valve in an energized state.

[0028] FIG. 8 is a plan view of a cooling apparatus for a vacuum pump according to a third embodiment of the invention.

[0029] FIG. 9 is a control circuit diagram showing electromagnetic valves 54, 55 in deenergized states.

[0030] FIG. 10 is a control circuit diagram showing electromagnetic valves 54, 55 in energized states.

[0031] FIG. 11 is a control circuit diagram showing the electromagnetic valve 54 in an energized state and the electromagnetic valve 55 in a deenergized state.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] A first embodiment of the present invention implemented with a multistage Roots pump will be explained below with reference to FIGS. 1 to 5.

[0033] As shown in FIG. 2, a front housing 13 is coupled to the front end of a rotor housing 12 of a multistage Roots pump 11. A seal member 10 is coupled to the front housing 13. A rear housing 14 is coupled to the rear end of the rotor housing 12. The rotor housing 12 includes a cylinder block 15 and a plurality of partitioning walls 16. As shown in FIGS. 3A, 3B and 3C, the cylinder block 15 includes a pair of block pieces 17, 18. As shown in FIGS. 3A and 3B, each partitioning wall 16 includes a pair of wall pieces 161, 162. As shown in FIG. 2, the space between the front housing 13 and one of the partitioning walls 16, the spaces between the adjoining partitioning walls 16, and the space between the rear housing 14 and the remaining partitioning wall 16 constitute pump chambers 39, 40, 41, 42, 43, respectively.

[0034] A pair rotary shafts 19, 20 are supported rotatably on the front housing 13 and the rear housing 14 through radial bearings 21, 21A, 22, 22A. The rotary shafts 19, 20 are arranged in parallel to each other through the partitioning walls 16.

[0035] The rotary shaft 19 is integrally formed with a plurality of rotors 23, 24, 25, 26, 27. The rotary shaft 20 is integrally formed with as many rotors 28, 29, 30, 31, 32. The rotors 23 to 32 have the same shape and the same size as viewed along the axes 191, 201 of the rotary shafts 19, 20. The rotors 23, 24, 25, 26, 27 have progressively smaller thicknesses in that order, and so do the rotors 28, 29, 30, 31, 32. The rotors 23, 28 are in mesh with each other and are encased in the pump chamber 39. The rotors 24, 29 are in mesh with each other and are encased in the pump chamber 40. The rotors 25, 30 are in mesh with each other and are encased in the pump chamber 41. The rotors 26, 31 are in mesh with each other and are encased in the pump chamber 42. The rotors 27, 32 are in mesh with each other and are encased in the pump chamber 43.

[0036] A drive unit 33 is assembled on the rear housing 14. The rotary shafts 19, 20 are projected into the drive unit 33 through the rear housing 14. The ends of the projected portions of the rotary shafts 19, 20 are fixedly secured with gears 34, 35 in mesh with each other. The rotary shaft 19 is rotated in the direction of arrow R1 in FIGS. 3A, 3B, 3C by an electric motor M shown in FIGS. 1 and 4. The turning effort of the rotary shaft 19 is transmitted through gears 34, 35 to the rotary shaft 20, which in turn is rotated in the direction reverse to that of the rotary shaft 19, as indicated by arrow R2 in FIGS. 3A, 3B, 3C.

[0037] As shown in FIGS. 2 and 3B, the partitioning walls 16 are each formed with a path 163 therein. As shown in FIG. 3B, the partitioning walls 16 are each formed with an inlet 164 and an outlet 165 of the path 163. The adjoining pump chambers 39, 40, 41, 42, 43 communicate with each other through the paths 163.

[0038] AS shown in FIG. 3A, the block piece 18 is formed with a gas intake port 181 in such a manner as to communicate with the pump chamber 39. As shown in FIG. 3C, the block piece 17 is formed with a gas exhaust port 171 in such a manner as to communicate with the pump chamber 43. The gas that has been introduced from the gas intake port 181 into the pump chamber 39 is transferred to the adjoining pump chamber 40 from the inlet 164 of the partitioning wall 16 by way of the outlet 165 through the path 163 by the rotation of the rotors 23, 28. In similar fashion, the gas is transferred to the pump chambers 40, 41, 42, 43 which have progressively smaller volumes in that order. The gas that has been transferred to the pump chamber 43 is discharged outside from a gas exhaust port 171. The rotors 23 to 32 are gas transfer members for transferring the gas.

[0039] As shown in FIG. 1, the multistage Roots pump 11 is accommodated in the case 36. The case 36 has mounted therein a controller 37 and an inverter 38 for controlling the electric motor M. A cooler 44 is mounted on the upper surface of the rotor housing 12, and another cooler 45 is mounted on the upper surface of the rear housing 14 and the drive unit 33. Still another cooler 46 is mounted on the upper surface of the controller 37. Yet another cooler 47 is mounted on the inverter 38, and a further cooler 48 is mounted on the peripheral surface of the electric motor M.

[0040] The cooler 46 for cooling the controller 37, the cooler 47 for cooling the inverter 38 and the cooler 48 for cooling the electric motor M are arranged midway of a main supply pipe 49 for supplying the coolant. The cooler 45 for cooling the rear housing 14 and the drive unit 33 and the cooler 44 for cooling the rotor housing 12 are arranged midway of a subsidiary supply pipe 50 for supplying the coolant. The electromagnetic three-way valve 51 is arranged at the diverging point of the main supply pipe 49 and the subsidiary supply pipe 50. A convergence pipe 52 having the function of blocking the reverse flow is arranged at the converging point of the main supply pipe 49 and the subsidiary supply pipe 50.

[0041] The electromagnetic three-way valve 51 can be switched between the deenergized state (supply prohibit mode) in which the supply of the coolant to the subsidiary supply pipe 50 is prohibited, as shown in FIG. 5A, and the energized state (supply permit mode) in which the supply of the coolant to the subsidiary supply pipe 50 is permitted, as shown in FIG. 5B. The main supply pipe 49 is supplied with the coolant from a coolant source not shown. The coolant source sends the coolant at a predetermined temperature and at a predetermined rate (the amount supplied per unit time) to the main supply pipe 49. The coolant sent to the main supply pipe 49 passes through the cooler 46, the cooler 47 and the cooler 48 in that order. As long as the electromagnetic three-way valve 51 is in supply prohibit mode (deenergized state), the coolant that has passed through the cooler 48 flows to the convergence pipe 52 through the main supply pipe 49. As long as the electromagnetic three-way valve 51 is in supply permit mode (energized state), on the other hand, the coolant that has passed through the cooler 48 flows to the coolers 45, 44 through the subsidiary supply pipe 50.

[0042] A temperature detector 53 is mounted on the surface of the rotor housing 12. The temperature detector 53 detects the surface temperature of the rotor housing 12. The temperature detection information obtained from the temperature detector 53 making up temperature detection means is sent to the controller 37. The controller 37 controls the energization and deenergization of the electromagnetic three-way valve 51 based on the temperature detection information obtained from the temperature detector 53.

[0043] In the case where the temperature Tx detected by the temperature detector 53 exceeds a preset target temperature T1, the controller 37 gives an instruction to energize the electromagnetic three-way valve 51. In response to the energizing instruction from the controller 37, the electromagnetic three-way valve 51 is energized. The electromagnetic three-way valve 51 thus energized allows the coolant to flow to the subsidiary supply pipe 50 from the main supply pipe 49 while at the same time blocking the flow of the coolant to the convergence pipe 52 through the main supply pipe 49. As a result, the temperature in the coolers 45, 44 decreases thereby to enhance the cooling operation of the coolers 45, 44. In the case where the detection temperature Tx is not higher than the target temperature range T1, on the other hand, the controller 37 gives an instruction to deenergize the electromagnetic three-way valve 51. The electromagnetic three-way valve 51 is deenergized in response to the deenergizing instruction from the controller 37. The deenergized electromagnetic three-way valve 51 prohibits the flow of the coolant from the main supply pipe 49 to the subsidiary supply pipe 50, while at the same time allowing the coolant to flow to the convergence pipe 52 through the main supply pipe 49. Thus, the coolers 45, 44 increase in temperature, so that the cooling effect of the coolers 45, 44 decreases. By controlling the cooling operation in this way, the surface temperature of the rotor housing 12 is converged to the target temperature T1.

[0044] The controller 37 constitutes switching control means for electrically switching the electromagnetic three-way valve 51 between the supply permit mode and the supply prohibit mode. The electromagnetic three-way valve 51 in turn constitutes supply switching means arranged at the diverging point of the main supply pipe 49 and the subsidiary supply pipe 50. The main supply pipe 49 and the coolers 46, 47, 48 make up a main supply path. The subsidiary supply pipe 50 and the coolers 44, 45 make up a subsidiary supply path.

[0045] The first embodiment has the following effects.

[0046] (1-1) The coolant of a predetermined temperature sent at a predetermined supply rate from the coolant source to the main supply pipe 49 is passed through the coolers 46, 47, 48 thereby to cool the controller 37, an inverter 38 and the electric motor M. In the case where the electromagnetic three-way valve 51 making up supply switching means is in supply permit mode, the coolant in the main supply pipe 49 that has been passed through the electric motor M is supplied to the subsidiary supply pipe 50. As long as the electromagnetic three-way valve is in supply prohibit mode, on the other hand, the coolant in the main supply pipe 49 is not supplied to the subsidiary supply pipe 50. The rotor housing 12 and the drive unit 33 cooled by the coolant passed through the subsidiary supply pipe 50 constitute a cooling area cooled by the coolant supplied to the subsidiary supply path. The rotor housing 12 and the drive unit 33 are cooled by intermittently supplying the coolant to the subsidiary supply pipe 50 by appropriately switching the electromagnetic three-way valve 51 between supply permit mode and supply prohibit mode.

[0047] The controller 37, the inverter 38 and the electric motor M constitute a simple cooling area where the only condition to be met is to cool to not higher than a desired temperature. In the pump chambers 39 to 43 for compressing the gas, however, an excessively low temperature may solidify the exhaust gas depending on the type of the exhaust gas (perfluorocarbon (PFC) gas, for example). The solidification of the exhaust gas shortens the service life of the vacuum pump. Therefore, the rotor housing 12 is not a simple cooling area where the only condition to be met is to cool to not higher than the desired temperature.

[0048] Also, the exhaust gas is liable to intrude into the drive unit 33 along the peripheral surface of the rotary shafts 19, 20, so that the cooling operation is required taking into consideration the solidification of the exhaust gas intruded into the drive unit 33. In other words, the drive unit 33 is also not a simple cooling area where the only condition to be met is to cool to not higher than the desired temperature.

[0049] By appropriately controlling the energization and deenergization of the electromagnetic three-way valve 51 that can be switched between supply permit mode and supply prohibit mode, the rotor housing 12 and the drive unit 33 can be properly cooled. The configuration in which the coolant is intermittently supplied to the coolers 45, 44 by switching the electromagnetic three-way valve 51 between energization and deenergization makes it possible to properly cool each cooling area of the controller 37, the inverter 38, the electric motor M, the drive unit 33 and the rotor housing 12 with a single coolant supply system including the main supply pipe 49 and the subsidiary supply pipe 50.

[0050] (1-2) A temperature detector 53 is mounted on the surface of the rotor housing 12 cooled by the coolant supplied to the subsidiary supply pipe 50, and the temperature of the rotor housing 12 is detected by the temperature detector 53. The controller 37 controls the supply of the coolant to the subsidiary supply pipe 50 based on the temperature of the rotor housing 12. The configuration in which the temperature of the cooling area constituted of the rotor housing 12 is controlled while detecting the temperature of the same cooling area is suitable for performing the proper cooling operation of the cooling area constituted of the rotor housing 12.

[0051] (1-3) A CPU is used as the controller 37 for giving an instruction to the electromagnetic three-way valve 51 based on the temperature detection information. An increased temperature of the controller 37 or the inverter 38 for controlling the electric motor M causes a control failure. The controller 37 making up the switching control means is arranged upstream of the electromagnetic three-way valve 51 in the main supply pipe 49, so that the controller 37 and the inverter 38 are constantly cooled by the coolant in the main supply pipe 49. The configuration in which the controller 37 and the inverter 38 are constantly cooled upstream of the electromagnetic three-way valve 51 is effective for positively avoiding the control failure which otherwise might be caused by an increased temperature of the controller 37 and the inverter 38.

[0052] (1-4) An increased temperature of the electric motor M shortens the service life of the electric motor M. The electric motor M is arranged upstream of the electromagnetic three-way valve 51 in the main supply pipe 49, so that the electric motor M is constantly cooled by the coolant in the main supply pipe 49. The configuration in which the electric motor M is constantly cooled upstream of the electromagnetic three-way valve 51 is effective for positively avoiding the shortening of the service life of the electric motor which otherwise might be caused by an increased temperature of the electric motor M.

[0053] (1-5) The multistage Roots pump 11 which can perform the operation of sucking while compressing the exhaust gas is a suitable object of application of the present invention.

[0054] (1-6) The single electromagnetic three-way valve 51 is suitable as supply switching means.

[0055] Now, a second embodiment will be explained with reference to FIGS. 6, 7A and 7B. The same component parts as those in the first embodiment are designated by the same reference numerals, respectively.

[0056] According to this embodiment, an electromagnetic valve 54 is arranged on the subsidiary supply pipe 50. The energization and deenergization of the electromagnetic valve 54 is controlled by a controller 37A. In the case where the temperature Tx detected by the temperature detector 53 exceeds a preset target temperature T1, the controller 37A gives an instruction to energize the electromagnetic valve 54. The electromagnetic valve 54 is thus energized in response to the energizing instruction from the controller 37A. As shown in FIG. 7B, the electromagnetic valve 54 thus energized allows the coolant to flow from the main supply pipe 49 to the subsidiary supply pipe 50. As a result, the temperature in the coolers 45, 44 is decreased thereby to enhance the cooling operation of the coolers 45, 44. In the case where the detection temperature Tx is not higher than the target temperature T1, on the other hand, the controller 37A gives an instruction to deenergize the electromagnetic valve 54. The electromagnetic valve 54 is thus deenergized in response to the deenergizing instruction from the controller 37A. As shown in FIG. 7A, the electromagnetic valve 54 thus deenergized prohibits the coolant from flowing from the main supply pipe 49 to the subsidiary supply pipe 50. As a result, the temperature in the coolers 45, 44 increases, so that the cooling effect of the coolers 45, 44 is decreased. By controlling the cooling operation in this way, the surface temperature of the rotor housing 12 is converged to the target temperature T1.

[0057] The controller 37A constitutes switching control means for electrically controlling the switching of the electromagnetic valve 54 between supply permit mode and supply prohibit mode. The electromagnetic valve 54 constitutes supply switching means arranged midway of the subsidiary supply pipe 50.

[0058] The second embodiment also produces the same effect as the effects of the first embodiment described in (1-1) to (1-5). Also, the electromagnetic valve 54 is preferable as supply switching means.

[0059] Now, a third embodiment shown in FIGS. 8 to 11 will be explained. The same component parts as the corresponding parts of the second embodiment are designated by the same reference numerals, respectively.

[0060] As shown in FIG. 8, a first electromagnetic valve 54 is arranged on the subsidiary supply pipe 50, and a second electromagnetic valve 55 is arranged on the main supply pipe 49 downstream of the diverging point of the main supply pipe 49 and the subsidiary supply pipe 50. The energization and deenergization of the first electromagnetic valve 54 and the second electromagnetic valve 55 is controlled by a controller 37B. A temperature detector 56 is mounted on the electric motor M. The temperature detector 56 detects the temperature of the electric motor M. The controller 37B controls the energization and deenergization of the electromagnetic valves 54, 55 based on the temperature detection information obtained from the temperature detectors 53, 56.

[0061] Assume that the temperature Ty detected by the temperature detector 56 exceeds a preset reference temperature T2. In the case where the temperature Tx detected by the temperature detector 53 exceeds the preset target temperature T1, the controller 37B gives an instruction to energize the first electromagnetic valve 54 and the second electromagnetic valve 55. The first electromagnetic valve 54 and the second electromagnetic valve 55 are energized in response to the energize instruction from the controller 37B. As shown in FIG. 10, the first electromagnetic valve 54 thus energized allows the coolant to flow from the main supply pipe 49 to the subsidiary supply pipe 50, while the second electromagnetic valve 55 energized blocks the flow of the coolant to the convergence pipe 52 through the main supply pipe 49. As a result, the temperature in the coolers 45, 44 decreases, thereby enhancing the cooling effect of the coolers 45, 44. In the case where the detection temperature Tx is not higher than the target temperature T1, on the other hand, the controller 37B gives an instruction to deenergize the first electromagnetic valve 54 and the second electromagnetic valve 55. The first electromagnetic valve 54 and the second electromagnetic valve 55 are deenergized in response to the deenergizing instruction from the controller 37B. As shown in FIG. 9, the first electromagnetic valve 54 thus deenergized prohibits the coolant from flowing from the main supply pipe 49 to the subsidiary supply pipe 50, while the second electromagnetic valve 55 deenergized allows the coolant to flow to the convergence pipe 52 through the main supply pipe 49. Thus, the temperature in the coolers 45, 44 increases, thereby reducing the cooling effect of the coolers 45, 44.

[0062] Assume that the temperature Ty detected by the temperature detector 56 is already not higher than a preset reference temperature T2. In the case where the temperature Tx detected by the temperature detector 53 exceeds the preset target temperature T1, the controller 37B gives an instruction to energize the first electromagnetic valve 54 and to deenergize the second electromagnetic valve 55 at the same time. The first electromagnetic valve 54 is energized in response to the energizing instruction from the controller 37B, while the second electromagnetic valve 55 is deenergized in response to the deenergizing instruction from the controller 37B. As shown in FIG. 11, the first electromagnetic valve 54 thus energized allows the coolant to flow from the main supply pipe 49 to the subsidiary supply pipe 50, while the second electromagnetic valve 55 thus deenergized allows the coolant to flow to the convergence pipe 52 through the main supply pipe 54. As a result, the temperature in the coolers 45, 44, is decreased and the cooling effect of the coolers 45, 44 is enhanced.

[0063] In the case where the detection temperature Tx is not higher than the target temperature T1, on the other hand, both the electromagnetic valves 54, 55 are deenergized.

[0064] By controlling the cooling operation in the way described above, the surface temperature of the rotor housing 12 is converged to the target temperature T1.

[0065] The controller 37B constitutes switching control means for electrically controlling the switching operation of the electromagnetic valve 54 between supply permit mode and supply prohibit mode. The first electromagnetic valve 54 and the second electromagnetic valve 55 constitute supply switching means.

[0066] According to the third embodiment, the same effects are obtained as the effects (1-1) to (1-5) of the first embodiment. The coolant supplied to the subsidiary supply pipe 50 is the one that has been passed through the electric motor M. The temperature of the coolant that been passed through the electric motor M affects the cooling operation of the coolers 44, 45 for the cooling areas (the rotor housing 12 and the drive unit 33) cooled by the coolant supplied to the subsidiary supply pipe 50. The control operation in which the amount of the coolant supplied to the subsidiary supply pipe 50 is divided into two stages in accordance with the temperature of the electric motor M located upstream of the subsidiary supply pipe 50 in the main supply pipe 49 improves the appropriateness of the cooling operation of the rotor housing 12 and the drive unit 33 cooled by the coolant supplied to the subsidiary supply pipe 50.

[0067] The present invention can also be embodied in the following manner:

[0068] (1) In the first embodiment, the cooler 45 for cooling the drive unit 33 may be located midway in the main supply pipe 49, the subsidiary supply pipe 50 may be branched off from the main supply pipe 49 downstream of the cooler 45, and the electromagnetic three-way valve 51 may be arranged at the diverging point of the main supply pipe 49 and the subsidiary supply pipe 50.

[0069] (2) In the first embodiment, the cooler 44 for cooling the rotor housing 12 and the cooler 45 for cooling the drive unit 33 may be arranged on separate subsidiary supply pipes, and an electromagnetic three-way valve may be arranged at the diverging point of each subsidiary supply pipe and the main supply pipe 49.

[0070] (3) The rotor housing 12 and the drive unit 33 may be cooled with a single cooler.

[0071] (4) In the first embodiment, the temperature of the cooler 44 may be detected by the temperature detector 53.

[0072] (5) The present invention is applicable also to vacuum pumps other than the Roots pump.

[0073] As described in detail above, the cooling apparatus according to this invention is configured with a main supply path arranged to supply a coolant for cooling at least one of a plurality of cooling areas, a subsidiary supply path arranged to supply the coolant from the main supply path for cooling at least one of a plurality of the cooling areas, and supply switching means capable of switching between the supply permit mode in which the coolant is supplied to the subsidiary supply path and the supply prohibit mode in which the coolant is not supplied to the subsidiary supply path. Therefore, the invention exhibits the superior effect of being capable of properly cooling a plurality of cooling areas of a vacuum pump with a single coolant supply system.

[0074] While the invention has been described by reference to specific embodiments chosen for purposes of illustration, it should be apparent that numerous modifications could be made thereto by those skilled in the art without departing from the basic concept and scope of the invention.

Claims

1. A cooling apparatus for cooling a vacuum pump, for accomplishing a sucking effect, by the transfer operation of a gas transfer member, comprising:

a main supply path arranged for supplying a coolant to cool at least one of a plurality of cooling areas of said vacuum pump;

a subsidiary supply path arranged for supplying a coolant from said main supply path to cool at least one of a plurality of the cooling areas; and

supply switching means capable of switching between the supply permit mode in which the coolant is supplied to said subsidiary supply path and the supply prohibit mode in which the coolant is not supplied to said subsidiary supply path.

2. A cooling apparatus for cooling a vacuum pump according to

claim 1, further comprising switching control means for electrically controlling the switching of said supply switching means between the supply permit mode and the supply prohibit mode, and temperature detection means for detecting the temperature of said cooling areas cooled by the coolant supplied to said subsidiary supply path or the temperature of said subsidiary supply path, wherein said switching control means controls said supply switching means in such a manner that the temperature of said cooling areas cooled by the coolant supplied to said subsidiary supply path is converged to a target temperature, based on the temperature detection information of said temperature detection means.

3. A cooling apparatus for cooling a vacuum pump according to

claim 2, wherein said switching control means is cooled by the coolant supplied to said main supply path and arranged upstream of said supply switching means in said main supply path.

4. A cooling apparatus for cooling a vacuum pump according to

claim 1, wherein said gas transfer member is driven by an electric motor, said electric motor is cooled by the coolant supplied to said main supply path, and said electric motor is arranged upstream of said supply switching means in said main supply path.

5. A cooling apparatus for cooling a vacuum pump according to

claim 1, wherein said vacuum pump is a multistage Roots pump comprising a plurality of rotary shafts arranged in parallel to each other, a plurality of rotors arranged on said rotary shafts, respectively, and a plurality of pump chambers each arranged in a rotor housing along the axes of said rotary shafts for accommodating a plurality of said rotors in mesh with each other, wherein the cooling areas cooled by the coolant supplied to said subsidiary supply path include said rotor housing forming said pump chambers.

6. A cooling apparatus for cooling a vacuum pump according to

claim 1, wherein said supply switching means is an electromagnetic three-way valve arranged at the diverging point of said main supply path and said subsidiary supply path.

7. A cooling apparatus for cooling a vacuum pump according to

claim 1, wherein said supply switching means is an electromagnetic valve arranged on said subsidiary supply path.

8. A cooling apparatus for cooling a vacuum pump, for accomplishing a sucking effect, by the transfer operation of a gas transfer member, comprising:

a main supply path arranged for supplying a coolant to cool at least one of a plurality of cooling areas of said vacuum pump;

a subsidiary supply path arranged for supplying a coolant from said main supply path to cool at least one of a plurality of the cooling areas; and

a supply path switch for switching between the supply permit mode in which the coolant is supplied to said subsidiary supply path and the supply prohibit mode in which the coolant is not supplied to said subsidiary supply path.