JP2002005169A - Fluid bearing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce torque for shearing pressure fluid supplied into a bearing pocket with a rotating shaft to decrease energy loss. SOLUTION: At least four or more bearing pockets 14 are disposed in the inner surface of a bearing metal 15 for supporting the rotating shaft 13, these pockets 14 are divided into at least three main pockets MP and one or more sub pockets SP for being used. Pressure fluid is steadily supplied from a pump 31 to the main pockets MP, and pressure fluid is selectively supplied to the sub pockets SP by an opening/closing operation of an opening/closing valve 42. During non-machining period in which machining resistance is not applied to the rotating shaft 13, when a load on the rotating shaft is not higher than a predetermined threshold value, or when a rotation speed of the rotating shaft 13 exceeds a predetermined threshold value, the opening/closing valve 42 is closed to stop supply of pressure fluid to the sub pockets SP.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluid bearing device for rotatably supporting a main spindle of a machine tool such as a grindstone shaft of a grinding machine.

[0002]

2. Description of the Related Art In a conventional hydrodynamic bearing device, FIG.
As shown in FIG. 3, the outer periphery of the bearing 11 is tightly fitted in the cylindrical bore 7 of the bearing housing 10, and the bearing surface 9 of the bearing 11 is
A plurality of bearing pockets 14 are formed at equal angular intervals in the circumferential direction, and an axially extending bearing land 15 that circumferentially separates the bearing pockets 14 is provided.
Constitutes a bearing surface 9 having a predetermined bearing clearance with the rotating shaft 13. A pressure fluid is supplied to the bearing pocket 14 from a supply port 19 of the bearing housing 10 through an annular groove 8 provided on the outer periphery of the bearing 11.

[0003]

However, when such a hydrodynamic bearing device is used in a high-speed grinding process in which a grinding wheel fixed to one end of a rotating shaft is rotated at a high peripheral speed, the rotating shaft itself also has a high rotational speed. It is necessary to drive at a speed. In this case, on the bearing surface, the torque for shearing the pressure fluid sharply increases, and the power consumption in the bearing portion increases. For this reason, at the time of high-speed rotation, a large-capacity electric motor power is required only to drive the rotating shaft without load, and the waste of energy is increased. At the same time, the calorific value also increases, causing a decrease in bearing clearance due to the effect of thermal expansion. In some cases, the rotating shaft and the bearing land may seize.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and prevents waste of energy without unnecessarily increasing power consumption in a bearing portion during non-machining, low load, or high-speed rotation. It is another object of the present invention to provide a hydrodynamic bearing device capable of preventing adverse effects due to thermal expansion.

[0005]

In order to solve the above-mentioned problems, a hydrodynamic bearing device according to the present invention has at least four or more main and sub-bearing pockets, and pressurizes fluid into at least three of the main bearing pockets. The present invention is characterized in that the mode is switched between a first mode for supplying the fluid and a second mode for supplying the pressurized fluid to the main and sub bearing pockets. According to this configuration, the mode is switched between the first mode and the second mode in accordance with the state of use, and the bearing performance such as bearing rigidity and power loss is changed.

In addition, when a tool or a workpiece attached to a rotary shaft contacts a workpiece or a tool and a processing resistance acts on the rotary shaft, and when the tool and the workpiece are not in contact with each other, a non-contact state occurs. It is characterized in that the switching means is distinguished from the processing time, and the switching means is switched to the second mode when the processing is performed, and the switching means is switched to the first mode when the processing is not performed. With this configuration, the processing state is switched to the second mode in a processing state in which processing resistance acts on the rotating shaft via a rotating tool such as a grinding wheel,
In this aspect, the pressurized fluid is supplied to both the main and sub bearing pockets, and the bearing stiffness is increased to counter the machining resistance.

Further, a speed detecting means for detecting a rotation speed of the rotating shaft is provided, and when the rotating shaft is rotating at a predetermined speed or more, the switching means is switched to the first mode, and at a speed less than the predetermined speed. When the rotating shaft is rotating, the switching means is switched to the second mode. According to this configuration, when the rotation speed of the rotating shaft shifts from the low speed region to the high speed region, the supporting rigidity of the sub bearing pocket is reduced, and the torque at which the outer peripheral surface of the rotating shaft shears the low pressure fluid remaining in the sub bearing pocket is reduced. Is significantly reduced, thereby reducing the loss of motor power required to drive the rotating shaft. In this case, the switching means may be in the form of a pressure control type in which the pressure of the fluid supplied to the sub-bearing pocket decreases as the rotation speed of the rotating shaft increases, and the rigidity of the bearing and the energy loss on the bearing surface can be reduced. Is precisely controlled according to the speed fluctuation of the rotating shaft.

Further, a load detecting means for detecting a machining load is provided, and the switching means is switched to the first mode when the load is low, and the switching means is switched to the second mode for increasing the bearing rigidity when the load is high. With this configuration, when the processing load increases, the supporting rigidity of the auxiliary bearing pocket is increased. The switching means may be an open / close operation type or a pressure control type.
When the pressure control type switching means is used, the pressure of the fluid supplied to the auxiliary bearing pocket is increased with an increase in load. In this way, the rotating shaft at the time of low load is supported by the pressurized fluid supplied to the main bearing pocket with less energy loss.

Further, the total number of the main and sub bearing pockets provided on the inner peripheral surface of the bearing metal is set to five or more, and the number of the sub bearing pockets to which the pressurized fluid is supplied is different from the second mode. The switching means can be switched. With this configuration, the bearing rigidity can be switched to a plurality of stages in accordance with the usage state of the hydrodynamic bearing device.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIGS. In FIG. 1, reference numeral 10 denotes a bearing housing constituting, for example, a grindstone stand of a grinding machine;
A rotating shaft 13 such as a grindstone shaft to which a not-shown grinding grindstone is fixed is supported at the left end thereof via a bearing metal 11. A bearing metal 11 having a flange 12 formed at the left end of the cylindrical inner hole 7 of the bearing housing 10 is tightly fitted, and is fixed to the left end surface of the bearing housing 10 with a bolt by the flange 12. As shown in FIG. 2 (a view taken along the line II-II in FIG. 1), six rectangular bearing pockets generally indicated by reference numeral 14 are provided on the bearing surface 9 formed on the inner surface of the bearing metal 11. Are formed. These bearing pockets 14 are defined at equal angular intervals in the circumferential direction by a plurality of bearing lands 15 extending in the axial direction, and both axial ends are defined by bearing lands 17, 17 'extending in the circumferential direction. .

Of these six pockets 14, three at the 12 o'clock, 4 o'clock and 8 o'clock positions of the watch shown in FIG. 2 are main bearing pockets, and the remaining three are sub bearing pockets. The main and sub bearing pockets are distinguished by reference numerals MP and SP, respectively. During operation, the main bearing pocket MP is constantly supplied with pressure fluid, while the sub-bearing pocket SP
The supply operation of the pressure fluid to the auxiliary bearing pocket SP is irregular or the pressure of the fluid supplied to these auxiliary bearing pockets SP is variable.

As shown in FIG. 2, each of the throttle elements 1 from the pump unit (pressure fluid supply means) 31 to every other three main bearing pockets MP used in the first embodiment.
A first supply path 40 for supplying the pressurized fluid via the first throttle element 4a and a second supply path 4 for supplying the remaining three auxiliary bearing pockets SP for use in the second embodiment via the respective throttle elements 14a.
It is a different system from 1. On the second supply path 41, a switching means 42 that opens and closes in response to a command from a controller (not shown) such as a CPU of a CNC device is provided. The switching unit 42 is configured as an opening / closing valve that opens and closes or a pressure control valve that controls pressure.

As will be described later, the control device (not shown) has a function of discriminating between a machining state and a non-machining state, a function of discriminating whether or not the rotary spindle 13 is rotating at a predetermined rotation speed or more,
A function for discriminating whether the processing load is a high load or a low load is provided as software, and the switching means 42 is switched in accordance with the identification result. Due to this switching operation, power consumption in the bearing portion during rotation is minimized, and energy is prevented from being wasted. As a result, heat generation in the bearing portion is suppressed and machining accuracy is reduced due to thermal deformation of the bearing device. Is minimized. FIG. 1 is a longitudinal sectional view of the present embodiment, and FIG. 2 which is a view taken in the direction of the arrow II in FIG. 1 shows a circumferential positional relationship between the bearing pocket 14 and the bearing land 15. .

As a first mode of use of the present invention, the control device is operated in accordance with the flowchart of FIG. 3 to discriminate between a machining state and a non-machining state (step 3-1). Since rigidity is required, the opening / closing valve 42 as a switching means is opened and switched to the second mode (step 3-3).
Is closed to switch to the first mode (step 3-
2). Accordingly, in the first mode during non-machining, the watch is arranged at the angular positions of 12 o'clock, 4 o'clock, and 8 o'clock in FIG. 2 (preferably at equal angles of 2 / 3π Rajang interval).
The pressure fluid is supplied to the first supply passage 4 only to the main bearing pockets MP.
0. In this case, the rotating shaft 13 is supported at three angular positions by the static pressure of the pressure oil generated in these three main bearing pockets MP. The shear torque at which the outer peripheral surface of the rotating shaft 13 shears the fluid is supplied to the first supply path 40.
The remaining three sub-bearing pockets SP at 2 o'clock, 6 o'clock and 10 o'clock positions of the watch which are larger on these three main bearing pockets MP receiving more supply of pressure fluid but without replenishment of pressure fluid. Above is smaller.

As described above, the control device opens and closes the on-off valve 42 when it is determined that the machining is being performed.
Thus, the pressurized fluid is supplied to all the six bearing pockets 14, and the rotating shaft 13 is supported at six angular positions by the static pressure of the pressure oil generated in these bearing pockets 14. It is reinforced to strongly oppose the processing load. During the operation of the machine tool, when the machining and the non-machining are compared, the non-machining time is longer than the machining time. By supplying the pressure fluid only to the main bearing pocket MP, waste of energy and heat generation of the bearing portion can be effectively suppressed.

The discrimination between working and non-working can be made by various methods. In a case where the control device is a CNC device that controls a grinding machine, for example, a forward position of a grindstone table 10 having a grinding wheel fixed to the left end of the rotating shaft 13 with respect to a workpiece (not shown) is arranged in a feed mechanism of the grindstone table 10. A determination is made based on the output of the encoder (not shown), and it is possible to identify whether the grinding wheel head 10 is at the processing position or at the non-processing position from the advance position information. In another method, for example, as shown in FIG. 1, a vibration sensor 43 is attached to the grindstone table 10, and the CNC device monitors the output of the vibration sensor 43 at a cycle of, for example, 1 millisecond, so as to be able to perform processing or not processing. Time can be identified.

Next, another embodiment will be described with reference to FIGS. In the embodiment shown in FIG. 4 and FIG. 5, by detecting the rotation speed of the rotating shaft 13, if the rotation speed is higher than a preset threshold, the rotation speed is used in the first mode. If they are the same or later, they are used in the second mode. More specifically, the CN
The C device periodically monitors the output from the rotation speed sensor SS provided on the electric motor M that drives the rotation shaft 13.
(Step 4-1) When the threshold value is set to, for example, 15,000 min ^-1 (15,000 rotations per minute), the CNC device determines that the speed of the rotating shaft 13 detected by the rotation speed sensor SS exceeds this threshold value. (Step 4-
2) If not, the open / close valve 42 is opened (step 4-3), whereby the pressure fluid is supplied to all six bearing pockets 14 (MP and SP).

Conversely, when the speed of the rotating shaft 13 exceeds the threshold value, the CNC device closes the opening / closing valve 42 (step 4-4), whereby the angles of the timepiece at 2:00, 6:00 and 10:00 are set. Three sub-bearing pockets SP located at different positions
The supply of pressure fluid to is stopped. In the high-speed rotation state,
The shearing resistance of the fluid on these auxiliary bearing pockets SP is reduced, and as shown in FIG. 5, the power consumption is reduced in a region exceeding the threshold value, and the power consumption of the bearing portion is sharply increased even when the rotating shaft 13 rotates at high speed. Can be used without increase. In the case where a pressure control valve is used as the switching means 42, the pressure of the fluid supplied to the auxiliary bearing pocket SP is controlled to be gradually reduced as the rotating shaft 13 increases the speed beyond a predetermined threshold speed. .

Next, another embodiment will be described with reference to FIGS. 6 and 7. FIG. In this embodiment, as shown in the flowchart of FIG. 6, by detecting the processing load,
Normally, it is used in the first mode, and when the load is high, the open / close valve 42 is switched so as to correspond to the second mode. More specifically,
The CNC device detects a processing load using a processing load sensor (not shown) (step 6-1), and determines whether the detected processing load exceeds a preset threshold (step 6-).
2), while the machining load does not exceed the threshold, the opening / closing valve 42 is closed (step 6-3), and conversely, while the machining load exceeds the threshold, the opening / closing valve 42 is opened (step 6).
-4). Thereby, as shown in FIG. 7, the bearing rigidity of the hydrodynamic bearing device according to the present invention is kept small in the first mode and large in the second mode after a predetermined processing load. That is, compared to a conventional hydrodynamic bearing device designed to always be able to cope with a high load, the device according to the present embodiment can reduce power consumption at a low load, and can suppress waste of energy.

Although the switching means 42 in this embodiment is constituted by an open / close valve, a pressure control valve may be used instead of the open / close valve as a modification. In this case, when the processing load further increases beyond the predetermined threshold, the pressure control valve 42 starts supplying the pressurized fluid to the sub-bearing pocket SP, and thereafter, the sub-bearing pocket SP increases as the processing load increases. Control is performed so as to increase the supply pressure to the SP. As the load sensor, for example, a sensor that detects a current value of the electric motor M, a strain gauge provided on a support system of a non-processed object, or the like can be used.

Further, as other embodiments, the embodiments shown in FIGS. 8 to 10 can be implemented. In the form of FIG.
In the first embodiment, three bearing pockets 14 are arranged at equal intervals on the circumference.
The pressure fluid is supplied to the two main pockets MP. In the second embodiment, the pressure fluid is also supplied to the two sub-pockets SP14 (black filled pockets) at the 2 o'clock and 10 o'clock positions.

In the embodiment of FIG. 9, six bearing pockets 14 are provided.
Are arranged, and the pressure fluid is supplied to the watch 3 in the first embodiment.
Hour, at 7 o'clock and 11 o'clock, supply to the three main pockets MP, and in the second embodiment also to the remaining three sub-pockets SP at 1 o'clock, 5 o'clock and 9 o'clock (black filled pockets) I do. In the embodiment shown in FIG. 10, eight bearing pockets 14 are arranged.
Pressure fluid is supplied to the three main pockets MP at the 5 o'clock and 7 o'clock positions, and in the second embodiment, the pressure fluid is also supplied to the three hatched sub-pockets SP at the 1 o'clock, 6 o'clock and 11 o'clock positions. Further, in the third embodiment, the pressure fluid is also supplied to the two sub-pockets SP filled with black at 3 o'clock and 9 o'clock so that the pressure fluid is supplied to all the pockets 14. In this embodiment, by providing two or more threshold values of the rotational speed of the rotating shaft 13 and the processing load, the usage form of the eight bearing pockets 14 can be set to three levels, and the reduction of power loss can be finely dealt with. It is.

As a modification of the embodiment shown in FIG. 8, a form in which the total number of the main and sub bearing pockets 14 is four can be adopted. In this case, in FIG. 8, when the grinding resistance acts from the 3 o'clock direction to the 9 o'clock direction in
The auxiliary bearing pocket SP at the hour position is eliminated, and in the second embodiment, additional pressure fluid is supplied to the auxiliary pocket SP at the 10 o'clock position so that the rotating shaft 13 can withstand the grinding resistance firmly. Thus, the present invention can be applied to a hydrodynamic bearing device in which at least four bearing pockets 14 in total are arranged around the rotating shaft 13.

In each of the embodiments described above, the bearing pockets 14 are arranged at an equal angle. However, it is not always necessary to arrange the bearing pockets 14 at an equal angle in consideration of the direction in which the machining load acts on the rotating shaft. Further, in each of the above embodiments, the circumferential width of the plurality of bearing pockets 14 facing the outer peripheral surface of the rotating shaft 13 is the same, but the circumferential width of the main pocket MP and the width of the sub pocket SP are changed. Can be adopted.

In the embodiment described above, all of the main and sub pockets MP and SP are arranged in a single row in the circumferential direction at the same position in the axial direction of the rotating shaft 13, but the main pocket MP and the sub pocket MP are arranged in one row. A form in which two sub-pockets SP or a row of sub-pockets SP are shifted in the axial direction and arranged in parallel is also possible. Further, as the pressure fluid used in the embodiment of the present invention, oil, water-based fluid, air and other gases can be used.

[0026]

As described in detail above, according to the present invention,
A first mode in which at least four bearing pockets are arranged in the circumferential direction of the rotating shaft, and a pressure fluid is supplied to not more than all and at least three main bearing pockets, and a pressure fluid is supplied to the remaining auxiliary bearing pockets. By switching between the second mode and the second mode, power consumption of the bearing portion can be minimized, energy consumption can be minimized, and deformation and seizure of the bearing portion due to thermal expansion can be prevented. be able to.

Preferably, as in the invention according to the second to fourth aspects, it is determined whether machining is being performed or not, whether the rotary shaft is rotating at a high speed, or whether the processing load is reduced. Since the determination is made and the bearing pocket to which the pressure fluid is supplied to the bearing pocket is switched based on the results of these determinations, the characteristics of the bearing device can be changed. This property change
This provides advantages such as a reduction in power loss of the rotary shaft driving motor during non-machining, use in a high-speed rotation region, or use under a low load.

More preferably, as in the fifth aspect of the invention, the number of bearing pockets to which the pressure fluid is supplied is gradually changed in a plurality of stages, so that the bearing characteristics can be changed more finely, and Loss can be more effectively reduced.

[Brief description of the drawings]

FIG. 1 shows a hydrodynamic bearing device showing an embodiment of the present invention in FIG.
FIG. 3 is a longitudinal sectional view taken along the line II.

FIG. 2 is a sectional view taken along the line II-II in FIG.

FIG. 3 is a control flowchart used in the embodiment of the present invention.

FIG. 4 is another control flowchart used in the embodiment of the present invention.

FIG. 5 is a graph showing a relationship between a rotation speed and power consumption in a control mode according to the flowchart of FIG. 4;

FIG. 6 is still another control flowchart used in the embodiment of the present invention.

FIG. 7 is a graph showing a relationship between a processing load and a bearing rigidity in a control mode according to the flowchart of FIG. 6;

FIG. 8 is an explanatory view illustrating the arrangement and use of bearing pockets in another embodiment of the present invention.

FIG. 9 is an explanatory view illustrating the arrangement and use of bearing pockets according to still another embodiment of the present invention.

FIG. 10 is an explanatory view illustrating the arrangement and use of bearing pockets according to another embodiment of the present invention.

FIG. 11 is a longitudinal sectional view of a conventional hydrodynamic bearing device.

[Explanation of symbols]

10: bearing housing, 11: bearing metal, 13: rotating shaft, 14: bearing pocket, 15: axial land,
18: discharge groove, 19: pressurized fluid supply port, 20: throttle element, 31: pump unit, 40, 41: pressurized fluid supply path, 42: open / close valve, 43: vibration sensor,

Claims (5)

[Claims] 1. A plurality of main bearing pockets and at least one sub-bearing pocket are arranged on an inner peripheral surface of a bearing metal attached to a bearing housing, and pressure fluid is supplied to the main and sub-bearing pockets via a throttle element. A fluid bearing device comprising a fluid supply means, wherein a rotating shaft fitted to an inner peripheral surface of the bearing metal via a predetermined gap is rotatably supported by a static pressure of a fluid generated in the bearing pocket. Switching the number of main and sub bearing pockets to at least four or more and switching between a first mode of supplying pressure fluid to at least three main bearing pockets and a second mode of supplying pressure fluid to the main and sub bearing pockets A fluid bearing device wherein means is provided in the fluid supply means. 2. A process in which one of a tool and a workpiece attached to the rotating shaft comes into contact with the other and a machining resistance acts on the rotating shaft, and a non-machining in which the tool and the workpiece are not in contact with each other. Is further provided. When the identification means identifies that the processing is being performed, the switching means is switched to the second mode. When the identification means identifies that the processing is not being performed, The hydrodynamic bearing device according to claim 1, wherein the switching means is switched to the first mode. 3. A speed detecting means for detecting a rotation speed of the rotating shaft, wherein the first speed detecting means detects that the rotating shaft is rotating at a predetermined speed or more. Switching the switching means to the second mode when the speed detecting means detects that the rotating shaft is rotating at a rotation speed less than or equal to a predetermined speed. Item 3. The hydrodynamic bearing device according to Item 1. 4. A load detecting means for detecting a machining load, wherein the switching means is switched to the second mode in which the bearing rigidity is high under a high load based on a detection result of the load detecting means. Item 3. The hydrodynamic bearing device according to Item 1. 5. The hydrodynamic bearing device according to claim 1, wherein a total number of said main and sub bearing pockets provided on an inner peripheral surface of said bearing metal is five or more, and a pressurized fluid is supplied. A fluid bearing device wherein the number of the auxiliary bearing pockets is switchable to a third mode different from the second mode.