JP3007493B2 - High speed and high load bearing device and screw compressor using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to relates to a high-speed and high-load bearing device, the bearing device and a screw compressor using the same, especially attained the survival of high-speed bearings in a screw compressor of the dry air.

[0002]

BACKGROUND OF THE INVENTION The present invention is effective in the field of supporting a rotor subjected to a thrust load, and is particularly advantageous in a screw compressor. In the dry rotary screw compressor, the rotation of the main rotor is transmitted to the sub-rotor via a power transmission gear. In this combination, the clearance between the power transmission gears is smaller than the clearance of the screw rotor in order to prevent contact with the screw rotor. Compressors that rotate at very high speed and do not allow oil to enter the compressed air are particularly used in the chemical or food processing fields. Also, for environmental reasons,
There is a growing demand for a type in which the above-mentioned oil does not enter. The bearing combinations for the rotors of these screw compressors conventionally include two single row angular contact ball bearings, face-to-face or back-to-back, with each bearing having the same contact angle. This kind of thrust bearing combination itself is not new and is described, for example, in U.S. Pat. No. 4,227,755 and U.S. Pat.
No. 0995.

In these known bearing combinations,
The contact angles of the two angular contact ball bearings are in the range of 30 ° to 40 °. One bearing is called a thrust bearing and functions to receive an axial force acting only in one direction during steady operation of the compressor, and the other bearing is called an auxiliary bearing or a backup bearing to adjust the rotor play. Has contributed.

In such a conventional device, both bearings are designed to have the same large contact angle so as to effectively receive the thrust load of the rotor during operation of the compressor.

[0005] Further, in the above-mentioned conventional apparatus, it was believed that setting the contact angle between the thrust bearing and the backup bearing to the same large value did not affect the thrust load capability in the bearing system. However, it has been found that the life of the conventional bearing combination is statistically shortened because the internal axial force caused by the centrifugal force acting on the ball under high-speed rotation increases. This means that in these conventional bearing combinations, the load-bearing bearing must support an axial force greater than the air compression provided by the rotor.

[0006] The life of the bearing is short, especially in applications such as screw compressors, due to the high load and high speed of rotation. Attempts to extend bearing life in this field have been made, such as by relatively increasing the axial clearance between bearings, as shown in FIG. However, large axial clearances have an adverse effect on compressor efficiency, and such measures are not satisfactory. Providing the bearings with axial clearance affects the accuracy of the relative positions of the rotors within the compressor housing. The large axial clearances in the bearings (see FIG. 4) require large clearances between the rotor and the housing to avoid so-called "rotor rubbing", and these large clearances are high on the high pressure side of the compressor. This may cause leakage from the room or space to the space on the low pressure side. Thus, the compressor is less efficient. Furthermore, large axial clearances cause slippage between the bearing balls and the bearing rings, shortening the service life.

An object of the present invention is to improve a thrust bearing, particularly a thrust bearing used for a screw compressor, so as to extend the life of the bearing and improve the performance of the compressor.

Another object of the present invention is to provide a thrust bearing having a large contact angle so as to support an external load, and to minimize an induced axial force caused by an internal force due to a centrifugal force even at a high speed. is there.

[0009]

According to the present invention, the above problems relate to a high-speed and high-load bearing device,
A high-speed, high-load bearing device in which first and second two angular contact bearings for thrust loads having different contact angles are disposed on a shaft adjacent to each other in a common housing. Bearing is 30 ° -4
A second angular contact bearing is provided as a thrust bearing for a main thrust load having a contact angle α in the range of 0 ° and a backup bearing having a contact angle β in the range of 15 ° to 25 ° smaller than the contact angle α. is provided as, the
The first and second angular contact bearings are
To form a radial gap around the
Non-contact in the radial direction, cylindrical roller shaft on the shaft
A receiver is arranged in contact with the housing in the radial direction,
This problem can be solved by minimizing the induced axial force generated in the second angular contact bearing and acting on the first angular contact bearing due to the internal force based on the centrifugal force acting on the rolling element.

[0010]

[0011] With respect to the screw compressor, the above-mentioned problems by rotatably supported to <br/> Rukoto a pair of rotors using the above bearing device is solved.

In high speed screw compressors, the centrifugal force acting on the bearing balls creates an axial force in the bearing, so that the thrust bearing is induced by the air compression provided by the rotor and the backup bearing. It turned out that both axial forces had to be countered. Furthermore, it has been found that the induced axial force can be minimized by reducing the contact angle in the backup bearing. This induced axial force is not affected by radial loads
In this state, the bearing is supported by the thrust bearing, so that the load on the thrust bearing is reduced and the life of the bearing is extended by an amount corresponding to the decrease in the induced axial force. Conventionally, the centrifugal force acting on the ball has not been considered to have a significant effect on the life of the bearing system. According to the invention, a contact angle of 30
A bearing combination having a thrust bearing of 40 ° to 40 ° and an opposing backup bearing of a small contact angle of 15 ° to 25 ° provides a bearing combination in an application field such as a screw compressor which has a wide load range and operates at high speed. It turns out that the life of the body is very long. As will be described in detail below, as a result of such a combination of bearings, the induced axial force based on the centrifugal force acting on the ball is minimized. Thus, the life of the bearing combination is prolonged. Furthermore, an angular contact bearing with a preload can be used for the bearing combination of the compressor. Such a preload is required for a compressor to accurately position the compressor in order to optimize its performance.

A comparison was made between a combination bearing that supports the rotor of the screw compressor according to the present invention and a conventional combination in which the thrust bearing and the backup bearing have the same contact angle. The results showed that the bearing life in the normal speed and load range imposed on the bearing during the operation of the compressor was greatly extended. This clearly indicates that the induced axial force due to the centrifugal force is minimized as shown in FIG. 11 in comparison with the conventional device shown in FIG.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention for achieving the above-mentioned object will be described in detail based on embodiments.

As mentioned above, certain compressors, such as dry air twin screw compressors, operate at high speed to maximize compression efficiency. Thrust bearings widely used in this field have a combination of two single-row angular contact bearings, and conventionally have a contact angle of 30 ° to 40 °.
A relatively large one was also used for both bearings. The reason for such a large contact angle for these bearings was to maximize the ability to support the air compression force (axial force) generated by the rotor.

In the past, it was believed that the internal axial force resulting from the centrifugal force was extremely small in the bearing combination.
However, it has been found that the conventional combination bearing has a relatively short life due to the centrifugal force of the ball due to the large contact angle described above. The effect of the centrifugal force of the ball on the induced axial force can be minimized by using an angular contact bearing with a small contact angle. However, the smaller the contact angle, the lower the ability of the compressor to support the axial force.

As described above, the present invention provides a bearing combination that minimizes the effect of centrifugal force on the induced axial force in a combined bearing and that can support the same or greater air compression force as a conventional combined bearing. . The relationship between force and life extension in the bearing combination of the present invention will be described below with reference to the drawings.

In particular, FIGS. 1 and 2 show a screw compressor as a so-called dry air compressor having the combination bearing of the present invention indicated by reference numeral 10. The overall structure and the basic elements of the compressor, except for the bearing combination, are not new, but have a housing 12, a main rotor 14 and a co-rotor 16 cooperating therewith. The main rotor 14 on the driving side receives the driving force from the driving means by means of gears, rotates, and transmits the rotation to the sub-rotor 16. As a general example, the rotors 14, 16 are in the form of a spiral screw meshing with each other. Gears 20 and 22 connect both rotors 14,16. The main rotor 14 and the sub-rotor 16 have stub shafts 24 and 26, respectively, and a bearing for rotatably supporting the rotor can be assembled to the stub shaft in a housing.

The operation and cycle of a compressor is typical, and when the compressor is performing this general cycle, radial and axial forces from air as the medium to be compressed are applied to the rotor. Will receive it. The axial force acting in the illustrated direction is indicated by K in the following figures. Thus, as the force acting on the rotor from the medium increases, the axial force K also increases. Further, in the illustrated example, the rotor is rotating at a constant high speed of about 30,000 RPM. In the conventional combination bearing shown in FIGS. 3 and 4, it has been found that an internal axial force Fbc, which is an axial component of the force due to the centrifugal force Fc acting on the bearing ball, additionally acts (FIG. 1).
0). It has also been found that the effect of this force increases with speed, and that as the contact angle increases, the internal axial force Fbc increases. It is important that in a conventional bearing combination with a thrust bearing 30 and a backup bearing 32 having the same contact angle, the thrust bearing must be able to support an axial force greater than the force generated by the compressed air. .

According to the present invention, the thrust bearing effectively reduces the force acting on the bearing, thereby extending the life as compared with the above-described conventional combination of angular contact bearings. In order to do so, in the present invention, the angular contact thrust bearing 3 having a large contact angle α is used.
0 'and an angular contact backup bearing 32' having a small contact angle are used in combination. Each of these bearings, which has been widely used in the past, has an inner ring Ri, an outer ring Ro, and a ball B disposed between the inner and outer rings. The contact angle α of the thrust bearing 30 is preferably in the range of 30 ° to 40 °, and the contact angle β of the backup bearing 32 is preferably in the range of 15 ° to 25 °. According to the invention, the difference between the contact angles of the thrust bearing and the backup bearing is at least 5 °, preferably between 15 ° and 20 °. In such a configuration, the guiding axial force takes a minimum value. As can be seen from FIGS. 8 and 9 and FIGS. 10 and 11, the life of the bearing according to the invention is long, as can be seen in the computer simulations of FIGS. 12 and 13.

Further, the arrangement of the present invention allows for a bearing assembly with a small clearance or preload, resulting in a more accurate positioning of the rotor and a large shaft which has a negative effect on compressor efficiency. The compressor efficiency is improved as compared with the conventional bearing combination having a directional clearance.

According to the analysis of the graphs of FIG. 10 and FIG.
It shows that the forces acting on the bearing combination according to the invention are smaller than in a conventional bearing combination. In both cases, the bearing is preloaded as shown in FIGS. The curves represent the axial load and the displacement of the combined bearing and show the distribution of the load on the two bearings of the combined bearing. When the bearing is not subject to external force K and is not rotating, the force within the bearing combination is the preload Fo.
In a typical bearing combination, when an external force K is applied, the displacement of the thrust bearing increases and the displacement of the backup bearing decreases. The external force K is the difference between the load on the thrust bearing and the load on the backup bearing.

When the bearing is rotating, the dashed curve shows the relationship between force and displacement. At high displacements, the solid and dashed curves almost coincide, and at low displacements there is a large difference between the two. It is noted that this difference is smaller for bearings with smaller contact angles. Another difference is that the bearing having a small contact angle has a small slope of the curve, and the load of the backup bearing is small at a high speed with respect to the applied force. The loads Fak and F'ak of the thrust bearing are the external load K and the loads Fbk and F'bk of the backup bearing, respectively.
In the bearing system of the present invention, compared with a conventional bearing system using a pair of angular contact bearings having the same large contact angle α under the same external load K, The load F'ak of the thrust bearing is small (see FIGS. 10 and 11).

Thus, the present invention provides a screw compression system which minimizes internal forces due to centrifugal force of the ball and induced axial forces as compared to conventional bearing combinations having a thrust bearing and a backup bearing having large and substantially equal contact angles. The present invention provides a bearing combination for a machine. The reaction force against the force of the compressor is shown in FIG.
FIG.

According to the present invention, the main force acting on the angular contact bearing is an axial load (thrust load),
Although illustrated and described with respect to bearing combinations in which radial loads are supported by cylindrical roller bearings, the principles of the present invention apply to bearing combinations with only angular contact bearings that support a combined load of radial and axial loads. , Get similar benefits.

Thus, according to the present invention, the above effects can be obtained by combining angular contact bearings having different contact angles. The contact angle is an angle measured by receiving a light measurement load when the bearing is not rotating.

The present invention is not limited to the illustrated embodiment,
Various modifications are possible within the scope of the present invention.

[Brief description of the drawings]

FIG. 1 is a partially broken side view of a dry air compressor having a bearing for a rotor according to the present invention.

FIG. 2 is an enlarged sectional view of a dashed-dotted line portion in FIG.

FIG. 3 is a cross-sectional view of a conventional bearing for a rotor.

FIG. 4 is a view of a dashed line portion in FIG. 3, showing a state where an end cover of a housing is removed.

FIG. 5 is a sectional view of a bearing for a rotor according to the present invention, showing a state in which an end cover of a housing is removed.

FIG. 6 shows a centrifugal force Fc acting on a ball having a large contact angle of 40 °.
3 is a diagram showing an axial component Fac of FIG.

FIG. 7 is a diagram showing an axial component Fbc of a centrifugal force Fc acting on a ball having a small contact angle of 15 ° to 25 °.

FIG. 8 is a diagram showing a reaction force acting on a conventional combined bearing.

FIG. 9 is a view showing a force acting on the bearing assembly of the present invention.

FIG. 10 is a diagram showing a relationship between axial force and displacement in a conventional combined bearing.

FIG. 11 is a diagram showing a relationship between axial force and displacement in the combination bearing of the present invention.

FIG. 12 is a diagram showing a comparison between the load of the thrust bearing in the present invention and the conventional combined bearing as a function of speed.

FIG. 13 is a diagram showing the bearing life for the load of FIG.

[Explanation of symbols]

 30 'thrust bearing 32' backup bearing

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-58-160621 (JP, A) West German Patent Application Publication No. 2746151 (DE, A1) (58) Fields investigated (Int. Cl. ⁷ , DB name) F04C 29/00 F04C 18/16 F16C 19/18

Claims (9)

(57) [Claims] 1. A high-speed, high-load bearing device in which first and second two angular contact bearings for thrust loads having different contact angles are disposed on a shaft adjacent to each other in a common housing. The first angular contact bearing is provided as a thrust bearing for a main thrust load having a contact angle α in the range of 30 ° to 40 °, and the second angular contact bearing is 15 ° smaller than the contact angle α.
First and second angular contact bearings provided as backup bearings having a contact angle β in the range of
Has a radial gap around it with the housing
Non-contact with the housing in the radial direction,
Cylindrical roller bearings are arranged in radial contact with the housing.
It is characterized in that an induced axial force acting on the first angular contact bearing which is generated in the second angular contact bearing by an internal force based on the centrifugal force acting on the rolling element is minimized. High speed and high load bearing device. 2. The high-speed high-speed high-speed bearing according to claim 1, wherein the thrust bearing and the backup bearing are a back-to-back combination.
Bearing device for load . 3. The high-speed high-speed high-speed bearing according to claim 1, wherein the thrust bearing and the backup bearing are combined in a frontal manner.
Bearing device for load . 4. The high-speed, high-load bearing device according to claim 1 , wherein a difference in a contact angle between the thrust bearing and the backup bearing is at least about 5 °. 5. The contact angle difference between the thrust bearing and the backup bearing is in the range of 15 ° to 25 °.
4. The high-speed and high-load bearing device according to 4 . 6. The height according to claim 5, wherein the difference in contact angle between the thrust bearing and the backup bearing is about 15 °.
Bearing device for high speed and high load . 7. A housing, a pair of rotors having a journal in the housing, and a bearing device rotatably supporting the journal in the housing, wherein the bearing devices have thrust loads having different contact angles. In a screw compressor having a high-speed and high-load bearing device in which first and second two angular contact bearings are disposed on a shaft adjacently in a common housing, the first angular contact bearing is A thrust bearing for a main thrust load having a contact angle α in the range of 30 ° to 40 ° is provided. The second angular contact bearing has a contact angle β in the range of 15 ° to 25 ° smaller than the contact angle α. Provided as backup bearings with first and second angular
Contact bearings are radially circumferential around the housing
A gap is formed so that it does not contact the housing in the radial direction.
And a cylindrical roller bearing is mounted on the shaft in the radial direction.
And the internal force based on the centrifugal force acting on the rolling elements, which is generated in the second angular contact bearing and minimizes the induced axial force acting on the first angular contact bearing. A screw compressor. 8. The screw compressor according to claim 7 , wherein the thrust bearing and the backup bearing are a back-to-back combination. 9. The screw compressor according to claim 7 , wherein the thrust bearing and the backup bearing are in a front combination.