JPH1163385A - Rotary shaft bearing lubricating method and rotary shaft temperature controlling method using this method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of excessive energy from a lubricant supply device so as to suppress temperature increase to minimum by suppressing turbulence of lubricant in a bearing unit and preventing an oil pump from discharging excessive oil unavailable for lubrication. SOLUTION: A driving motor 8 is driven by means of an inverter at a selected number of revolutions when a power source of a lubricant supply device is turned on, and lubricant is fed out by means of an oil pump 5 at a selected discharge ratio of 1800 cc/min so as to be fed to a spindle bearing unit 1 from a supply flow passage 11 by a proper quantity for eliminating turbulence due to stirring. Then, the lubricant, which lubricated the spindle bearing unit 1, is heated because it takes the heat generated in lubrication while lubricating the bearing, and the oil pump 5 is prevented from discharging excessive oil, which not used for lubrication, so that the generation of excessive energy from the lubricant supply device is prevented, and the oil raised in temperature is returned to an oil tank 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of lubricating a rotating shaft bearing similar to a main shaft of an industrial machine, particularly a machine tool requiring high precision, for example, a grinding machine, a lathe, a machining center, etc., and a rotating shaft using the method. It relates to a temperature control method.

[0002]

2. Description of the Related Art The temperature of a spindle bearing used in a machine tool rises with an increase in the rotation speed of the spindle, and this rise in temperature also limits the maximum rotation speed of the spindle. At the same time, thermal displacement occurs in the spindle or the headstock, which affects machining accuracy. Therefore, it is a matter of each manufacturing engineer how to suppress the rise in bearing temperature. A conventional lubricating oil supply device for a bearing, which is generally performed, will be described with reference to FIG. The main spindle unit 1 has, for example, a main spindle 2 having a tool attached to its tip end supported by a bearing [fluid bearing (dynamic pressure bearing or the like) or a rolling bearing].
Driven by direct connection with An oil pump 5 of the lubricating oil supply device is connected to an oil tank 7 via a filter 6. The oil pump 5 discharges a certain amount of oil by the rotation of the drive motor 8. The discharged lubricating oil is supplied to the bearing of the bearing unit 1 from the supply flow path 11 via the oil amount adjusting valve 9 and the pressure control valve 10, and after lubricating the bearing, is returned to the oil tank 7 from the discharge flow path 12. The flow control valve 9 is normally adjusted to an appropriate flow rate required by the bearing, and excess oil not supplied to the bearing is returned to the oil tank 7 through the discharge path 11 of the pressure control valve 10.

[0003]

SUMMARY OF THE INVENTION Generally, an oil pump 5
Since the drive motor 8 is designed and used with a sufficient capacity, an extra flow not required for lubrication is inevitably discharged from the discharge passage 11 of the pressure control valve 10 to further increase the temperature of the oil in the tank 7. To raise. The oil pump 5 and the drive motor 8 generate extra energy by the amount of the discharged flow. This energy becomes the temperature rise of the lubricating oil supply device itself without being recovered, and is added to the temperature of the lubricating oil, which leads to the temperature rise. In addition to the temperature rise of the bearing itself due to the heat generated by the rotation of the main shaft in the bearing unit, the temperature of the lubricating oil, whose temperature has already risen due to the extra energy, is added to the overall temperature of the bearing unit, resulting in a corresponding increase in the temperature of the main shaft unit. Has reached the upper limit of the operable rotation speed, that is, approaches the inoperable limit, and further increases the thermal displacement of the machine.

In addition, even if the amount of lubricating oil required for the bearing of the bearing unit is adjusted by the flow control valve, it is often unsuitable, and is generally adjusted from the conventional idea to a large amount. As a result of the turbulence, it has been found that there is a problem that the temperature is increasing. SUMMARY OF THE INVENTION The present invention has been made in view of such problems of the related art, and has as its object to agitate lubricating oil in a bearing unit and to generate extra energy generated from a lubricating oil supply device. By stopping the supply of lubricating oil with an extra temperature rise to the bearing unit, a method of lubricating a rotating shaft bearing capable of minimizing the temperature rise and a method of controlling the temperature of a rotating shaft using this method will be provided. It is assumed that.

[0005]

According to the present invention, in order to solve this problem, an oil pump for supplying lubricating oil to a bearing of a rotary shaft uses a type capable of obtaining a discharge amount corresponding to the number of rotations, and is previously rotated. Determine the relationship between the bearing temperature rise and the lubricating oil flow rate using the shaft rotation speed as a parameter to determine the optimum lubrication oil flow rate at the minimum temperature rise relative to the rotation speed, and correspond to the rotation speed of the rotating shaft to be operated. The bearing is lubricated with the optimal lubricating oil flow rate by controlling the number of revolutions of the oil pump so that the optimal lubricating oil flow rate is discharged. Is prevented from being discharged by the oil pump, thereby eliminating the generation of extra energy from the lubricating oil supply device. The bearing is lubricated such that the oil pump discharges an optimal lubricating oil flow rate corresponding to the rotation speed of the rotating shaft. As a result, no turbulent flow occurs due to agitation of the lubricating oil in the bearing unit, no extra energy is generated from the oil pump and the drive motor, and the temperature rise of the lubricating oil supply device itself is minimized, which is passed on to the temperature rise of the bearing. The degree to which it is minimized. Also, since the required lubricating oil flow rate is supplied to the bearing in accordance with the operating conditions, the temperature rise of the bearing is minimized.

[0006] An oil pump for supplying lubricating oil to a bearing of a rotary shaft is of a type capable of obtaining a discharge amount corresponding to the number of rotations. The optimum lubricating oil flow rate at the time of the minimum temperature rise for various rotation speeds is obtained by calculating the relationship with the rotation speed, and a temperature characteristic curve connecting the points of the minimum temperature rise for various rotation speeds is obtained, and the temperature characteristic curve is calculated. Utilizing the present invention, it is possible to supply an optimal lubricating oil flow rate to each of the rotation speeds in accordance with a wide rotation speed range, and to operate at a minimum temperature increase at any of the rotation speeds. It is possible to determine the limit that can be operated in a wide range and at the maximum speed.

[0007] An oil pump for supplying lubricating oil to the bearing of the rotary shaft is of a type capable of obtaining a discharge amount corresponding to the number of rotations. Find the relationship with the flow rate and grasp the optimal lubricating oil flow rate when the minimum temperature rises with respect to the rotation speed.
When the rotating shaft is started, the lubricating oil flow rate is supplied in a much larger amount than the optimal lubricating oil flow rate, and the temperature rise of the bearing rises rapidly. By switching to the lubricating oil flow rate, the time required for the bearing temperature of the rotating shaft to reach the saturation point is shortened. Since a larger amount of lubricating oil is supplied than the optimal lubricating oil flow rate, there is no risk of bearing seizure, safe operation is possible, and the time required for the temperature of the rotating shaft to reach the saturation point can be reduced.

[0008]

DETAILED DESCRIPTION OF THE INVENTION The inventor of the present invention has studied for a long time the relationship between the temperature rise of a bearing of a spindle unit employing a hydrodynamic bearing of a rotary shaft and the flow rate of lubricating oil, and as a result has found one new fact. That is, it has been common general knowledge that the temperature rise of the conventional bearing can be suppressed by increasing the lubricating oil flow rate. However, during repeated experiments, it was questioned that the higher the lubricating oil flow rate, the better. Bearing configuration,
It has been found that the lubricating oil flow rate required for the bearing is determined for each of the rotating shafts manufactured in consideration of various conditions such as the load condition and the like, and that there is an optimum flow rate for reducing a rise in the bearing temperature.

First, it has been clarified that the extra oil that the bearing does not need for lubrication has been returned to the tank, which adversely affects the increase in lubricating oil temperature.
In the second case, even if the amount of lubricating oil required for the bearing of the bearing unit is adjusted by the flow control valve, it is often not suitable, and from the conventional idea it is generally adjusted to prevent seizure, As a result of the generation of turbulence due to the agitation of excess lubricating oil in the bearing unit, it became clear that a temperature rise had occurred.

FIG. 2 is a table showing an example of the experimental results.
The experimental conditions at this time were: bearing type; dynamic pressure bearing, shaft diameter φ5
5mm, lubricating oil; Esso standard, velocity #
3, room temperature; 22 ° C.

The table shows the relationship between the lubricating oil flow rate and the temperature rise of the bearing unit with the rotation speed of the rotating shaft as a parameter. When the rotational speed of the rotating shaft is 2000 rpm, the value of the temperature rise is steadily reduced up to about 1200 cc / min of the lubricating oil flow rate at the point F1 with respect to the increase of the supply amount of the lubricating oil, but exceeds 1200 cc / min. From around the value of the temperature rise has started to rise again. This is due to a turbulent flow phenomenon caused by agitation by extra lubricating oil in the bearing unit. That is, it indicates that there is a flow rate at which the temperature rise becomes minimum. When the rotation speed of the rotating shaft is 4000 rpm, the lowest flow rate at the temperature rise is the point F2 near about 1800 cc / min. When the rotation speed of the rotating shaft is 6500 rpm, the lowest flow rate of the temperature rise is the point F3 near 2300 cc / min. The F1, F2, and F3 points vary depending on the structure, load, and the like of the bearing. Therefore, this experimental data should be obtained for an actual bearing unit.

[0012]

FIG. 3 shows a bearing lubrication device used in the present invention based on the above experimental results. The same parts as those in FIG. The oil pump 5 is a commercially available oil pump whose discharge amount can be changed according to the number of revolutions, and the drive motor 8 is controlled by the control means 20. Therefore, the flow regulating valve 9 and the pressure regulating valve 10 which are required in the prior art become unnecessary.

The first case of the electric control of the control means 20 used here will be described with reference to FIG. As the drive motor 8, a general-purpose motor can be used, and a commercially available normal inverter 21 that changes the frequency of the input power of the motor 8 can be used. The rotation speed of the drive motor 8 is adjusted by the inverter to the rotation speed of the oil pump 5 so that the required discharge amount is obtained.

The second case of the electric control will be described with reference to FIG. The drive motor 8 uses a DC motor 22 and a voltage converter 23 that changes the voltage of the AC power supply as a DC power supply using a rectifier. By changing the DC voltage, the rotational speed of the drive motor 8 is adjusted to the rotational speed of the oil pump 5 so that the required discharge amount is obtained.

A third case of the electric control will be described with reference to FIG. As a commercially available oil pump, a linear motor oil pump or a piebrator oil pump 25 is used. The frequency converter 26 is combined with the rotation speed control of the pump. The frequency of the frequency converter 26 is changed to match the rotation speed of the oil pump 25 so that the discharge amount requires the rotation of the drive motor 8.

The case of mechanical control will be described with reference to FIG. Transmission 2 commercially available on the output shaft of drive motor 8
7 and the output shaft is connected to the oil pump 5. Then, the transmission is adjusted to the rotation speed of the oil pump so that a required discharge amount is obtained.

The operation of the present invention in such a configuration will be described. When the rotating shaft bearing unit 1 is determined according to the use conditions, the number of rotations is inevitably determined. Generally, this rotation speed may be a fixed rotation speed or a certain range depending on the application. Now, it is assumed that the configuration of FIG. 4 is used for the control means 20 of the drive motor 8. The rotation speed of the rotating shaft was used as a parameter. The relationship between the temperature rise of the rotary bearing unit 1 and the lubricating oil flow rate is confirmed by an experiment in advance, and an optimum lubricating oil flow rate corresponding to the minimum temperature rise is confirmed from FIG. The number of revolutions at which the optimum lubricating oil flow rate is discharged is selected from a characteristic table showing the relationship between the discharge amount and the number of revolutions of the oil pump. Inverter 2
The frequency of 1 is selected and the rotation speed of the drive motor 8 is adjusted to the rotation speed of the oil pump. The number of rotations of the drive motor is individually set from the relationship between the number of rotations of the oil pump and the discharge amount measured in advance.

For example, assuming that the rotational speed of the rotating shaft is 4000 rpm, the optimum lubricating oil flow rate is 1800 cc / m
in and FIG. Or F1, F2 in FIG.
From the points F3 and F3, a temperature curve H connecting the points of the minimum temperature rise with respect to the individual rotation speeds can be obtained as shown in FIG. The line G in FIG. 8 represents the flow rate at point F1 in FIG.
The flow rate when operating at 00,6500 rpm, ie, F
Since the value of the temperature rise at the point of intersection with the vertical line intersecting with one point is plotted, it is 4000,6500 rpm
In this case, the temperature rises higher than the H line. The difference in the temperature rise between the G line and the H line at each rotation speed means that the system can be operated at a lower temperature than the ordinary operation system.

When the power supply of the lubricating oil supply device is turned on, the drive motor 8 is driven at the rotation speed selected by the inverter 21. As a result, the oil pump 5 has the selected discharge amount of 1800cc.
/ Min lubricating oil is fed out and supplied to the main shaft bearing unit 1 from the supply flow path 11. Since the lubricating oil is supplied in an appropriate amount, there is no turbulent flow due to agitation in the bearing unit, and the lubricating oil lubricating the main shaft bearing unit 1 is returned to the oil tank 7 from the discharge passage 12. The circulated oil lubricates the bearings and generates heat by returning the heat generated to the oil tank 7. However, since no extra energy is generated in the lubricating oil supply device, the temperature of the oil in the tank does not rise further than the temperature rise due to the heat from the bearing unit, and the temperature rise of the main shaft bearing unit is small. In the embodiment, the dynamic pressure bearing is used as an example, but it is needless to say that the present invention can be applied to a rolling bearing.

When a wide rotation speed range is required and a high-speed rotation shaft is required, an oil pump for supplying lubricating oil to the bearing is provided with a type capable of obtaining a discharge amount corresponding to the rotation speed. The optimum lubricating oil flow rate at the minimum temperature rise for various rotational speeds is determined by obtaining the relationship between the bearing temperature rise and the lubricating oil flow rate using the rotational speed as a parameter, and the minimum temperature rise for various rotational speeds is determined. A temperature characteristic curve connecting the points can be obtained. Conventionally, when operating over a wide rotational speed range with the same lubricating oil flow rate, a low rotational speed will also be operated at a lubricating oil flow rate that satisfies the maximum rotational speed in that range, and at low rotational speeds, it is originally low As a result, the operation is performed at a higher temperature than when the operation is performed only at the rotation speed. The present invention uses the above-mentioned temperature characteristic curve to supply the optimal lubricating oil flow rate for each rotational speed over a wide rotational speed range. Control method of lubricating oil supply.
This method is effective for operating the rotating shaft in a wide rotation range. It is also possible to increase the upper limit of the high-speed rotation.

Further, the rotating shaft lubrication method described in the present invention can be applied to a case where it is desired to quickly reach a stable temperature range (saturation point) of the bearing unit. If the lubricating oil flow rate is reduced, the temperature rises faster, but in this case, there is a high possibility that bearing seizure will occur, and dangerous operation must be avoided. The present invention is a method that can be operated in a safe state. When the relationship between the temperature rise due to the rotation of the rotating shaft and the elapsed time is in the state shown by the line D in FIG. 9, a much larger flow rate than the optimal lubricating oil flow rate for the temperature rise at the rotating shaft speed at that time is applied. The temperature of the bearing unit 1 is increased to the point E1 on the E line by increasing the temperature of the bearing unit 1 and the lubricating oil supply is reduced when the temperature reaches the point E1. After a while, by finally switching to the optimum lubricating oil flow rate of the rotation speed, it can be said that the time required to reach the temperature stable region is almost halved.

In the case of a rotating shaft that is frequently started and stopped, the temperature of the rotating shaft is raised by increasing the lubricating oil supply amount from the optimum lubricating oil flow amount and returning to the optimum lubricating oil flow amount only at the time of start-up in the same manner as described above. Can be prevented from increasing, and wear of the rotating shaft can be reduced. As a result, the operating efficiency of the machine can be increased, and the operating range of the main shaft, that is, the range of temperature rise can be controlled to a certain extent. Further, by obtaining the optimum lubricating oil flow rate corresponding to the rotation speed in a wide range of the rotation speed of the rotation shaft from FIG. 8, the rotation speed of the oil pump is sequentially or manually switched automatically in response to the change of the rotation speed. A wide range can be supported.

[0023]

According to the first aspect of the present invention, the oil pump is controlled so that the oil pump discharges an optimum lubricating oil flow rate corresponding to the spindle speed previously determined by an experiment in advance. Since the oil supply is eliminated, the lubricating oil supply device including the oil pump and the drive motor does not generate extra energy, and can be stopped only by an increase in oil temperature due to heat generated in the bearing. Thus, turbulent flow due to agitation can be prevented, and a rise in the temperature of the bearing unit can be totally minimized. For this reason, it is possible to operate with a lower temperature rise in a wider rotation speed range than in the conventional case, and a bearing unit having a high speed rotation range can be obtained. Further, it is possible to minimize the temperature rise of the bearing unit operated only at a specific rotation speed without adding a special cooling device. It also contributes to power saving. According to the second aspect of the present invention, the operation can be performed with a minimum temperature increase in a wide rotation speed range. According to the third aspect of the present invention, it is possible to quickly reach the stable region of the rotating shaft temperature, thereby increasing the operation efficiency. And the temperature rise can be controlled over a wide range from the lowest point.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a conventional lubricating oil supply device for a bearing.

FIG. 2 is a table showing a relationship between a bearing temperature rise and a lubricating oil amount using a rotational speed as a parameter.

FIG. 3 is an explanatory view showing a lubricating oil supply device for a bearing according to the present invention.

FIG. 4 is an explanatory diagram showing a first electric control of an oil pump drive motor.

FIG. 5 is an explanatory diagram showing a second electric control of the oil pump drive motor.

FIG. 6 is an explanatory diagram showing a third electric control of the oil pump drive motor.

FIG. 7 is an explanatory diagram showing mechanical control of an oil pump drive motor.

FIG. 8 is a table showing a relationship between a spindle temperature rise and a rotation speed with respect to an optimal lubricating oil flow rate.

FIG. 9 is a table showing a relationship between a temperature rise of a bearing unit and an elapsed time.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main shaft bearing unit 2 Main shaft 3 Drive motor 5 Oil pump 8 Drive motor 20 Motor rotation speed control device 21 Inverter 22 DC motor 23 DC voltage converter 25 Linear motor oil pump 26 Frequency converter 27 Transmission

Claims (3)

[Claims] An oil pump for supplying lubricating oil to a bearing of a rotating shaft is of a type capable of obtaining a discharge amount corresponding to the number of rotations. Obtain the optimal lubricating oil flow rate at the time of minimum temperature rise with respect to the rotational speed by obtaining the relationship with the oil flow rate, and adjust the rotational speed of the oil pump to discharge the optimal lubricating oil flow rate corresponding to the rotational speed of the rotating shaft to be operated. The lubricating oil supply device controls and lubricates the bearing with the optimal lubricating oil flow rate, suppresses the turbulence of the lubricating oil in the bearing unit, and prevents the oil pump from discharging extra oil not used for lubrication. A method of lubricating a rotating shaft bearing, which eliminates the generation of extra energy from the shaft. 2. An oil pump that supplies lubricating oil to a bearing of a rotating shaft uses a type capable of obtaining a discharge amount corresponding to the number of rotations, and a bearing temperature rise and a lubricating oil to be supplied in advance using the number of rotations of the rotating shaft as a parameter. The optimum lubricating oil flow rate at the time of the minimum temperature rise for various rotation speeds is obtained by obtaining the relationship with the flow rate, and the temperature characteristic curve connecting the points of the minimum temperature rise for various rotation speeds is obtained. A method for controlling the temperature of a rotating shaft, characterized in that an optimum lubricating oil flow rate is supplied to each of the rotation speeds in correspondence with a wide rotation speed range by using the above-mentioned method, and the operation can be performed with a minimum temperature rise at any of the rotation speeds. 3. An oil pump that supplies lubricating oil to a bearing of a rotating shaft uses a type capable of obtaining a discharge amount corresponding to the number of rotations. Obtain the relationship with the oil flow rate and grasp the optimal lubricating oil flow rate at the time of the minimum temperature rise for various rotation speeds. The temperature rise of the shaft rapidly increases, and when the temperature exceeds the saturation point, the lubricating oil supply flow rate is reduced, and after a while, switching to the optimal lubricating oil flow rate shortens the time required for the rotating shaft bearing temperature to reach the saturation point. A method of controlling the temperature of the rotating shaft.