Spindle device for machine tool

Abstract

To provide a spindle device of a machine tool capable of preventing the reduction of the service life and damage of a bearing by optimizing a preparatory operation.SOLUTION: The spindle device 1 is provided with a preparatory operation control part 31 for controlling the preparatory operation as a control part which has not been conventionally provided. The preparatory operation control unit 31 displays an alarm and controls the main shaft so as not to increase the rotation speed to the allowable maximum rotation speed S1 or more when the operation at the rotation speed equal to or higher than S1 is to be started before the elapsed time of the operation at the rotation speed equal to or lower than S1 becomes equal to or longer than Tp with respect to the set preparatory operation time Tp.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a spindle unit provided in a machine tool, for example, a machining center. [Background technology]

[0002] In the spindle unit of a machine tool, the bearings that support the spindle are lubricated by a lubricating oil supply system. For lubrication, methods that use compressed air to transport and supply lubricating oil, such as oil-air lubrication and oil-mist lubrication, are often used.

[0003] An example of a conventional spindle unit of a machine tool is shown in Figure 5. As shown in the figure, the spindle unit (1) includes a cylindrical body (2), a spindle (3) extending on the axis of the body (2), a plurality of bearings (4) interposed between the inner surface of the body (2) and the outer surface of the spindle (3), a nozzle (5) that sprays lubricating oil conveyed by compressed air and supplies it to each bearing (4), and discharge passages (6) and (7) provided in the body (2) that discharge oil-air from the vicinity of each bearing (4) to the outside of the body (2).

[0004] In the above-described spindle device (1), if the lubricating oil in the piping is low because the spindle device (1) has been stopped for a long period of time, it takes a certain amount of time for the lubricating oil to reach the bearings (4). Therefore, if the spindle device (1) is suddenly started, the spindle device will be operating in a state of insufficient lubrication, and an oil film will not be formed sufficiently, which may lead to a shortened life of the bearings (4) or damage to the bearings (4). Furthermore, if the lubricating oil accumulated in the piping is supplied when the machine tool starts operating, an excess of oil will occur, causing the temperature of the bearings (4) to rise, which may lead to damage to the bearings (4).

[0005] As a method for preventing damage to bearings in spindle devices and extending their lifespan, Patent Document 1 proposes monitoring the downtime of a machine tool, and if the downtime is equal to or exceeds a predetermined value, prohibiting the spindle from rotating beyond the predetermined value, thereby avoiding the risk of damage. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 8-267340 Summary of the Invention [Problem to be solved by the invention]

[0007] The supply of lubricating oil to the bearings needs to be an optimal amount, neither too little nor too much, and it is necessary to stably supply the amount, and the monitoring of downtime as in Patent Document 1 is insufficient. In recent years, in order to reduce the environmental impact, it has become necessary to minimize warm-up operation time. To avoid operation in an unstable state with the lubricating oil supplied to the bearings, it is necessary to carry out warm-up operation that is optimal for the size of the machine tool and the length of downtime.

[0008] In view of the above circumstances, an object of the present invention is to provide a spindle device for a machine tool that can prevent a reduction in the lifespan of and damage to bearings by optimizing preparatory operation. [Means for solving the problem]

[0009] In order to achieve the above object, the present invention comprises the following aspects.

[0010] 1) In a spindle device of a machine tool, lubricating oil is conveyed by air to lubricate the bearings that support the spindle, A preparatory operation control unit is provided to control the preparatory operation, A spindle device of a machine tool characterized in that the preparatory operation control unit displays an alarm when an attempt is made to start operation at S1 or higher before the elapsed time of operation at or below the maximum allowable rotation speed S1 during preparatory operation reaches or exceeds Tp for a set preparatory operation time Tp, and controls the spindle so that the rotation speed cannot be increased above S1.

[0011] 2) The spindle device of a machine tool according to 1) above, characterized in that the stop time Ts since the previous operation is acquired, and the preparatory operation is carried out when Ts is equal to or greater than a predetermined value.

[0012] 3) The spindle device of a machine tool according to 1) or 2) above, characterized in that after the preparatory operation is carried out for a period of Tp at a rotation speed of S1 or less, operation at a rotation speed of S1 or more is carried out in stages as a further preparatory operation.

[0013] 4) A spindle device of a machine tool according to any one of 1) to 3) above, characterized in that Tp is calculated by Tp = L / V or Tp = L / V + C (C is the time it takes for the lubricating oil to become accustomed to the bearings), where L is the length of the lubricating oil supply pipe and V is the speed at which the lubricating oil advances through the pipe.

[0014] 5) A spindle device for a machine tool according to 4) above, characterized in that a temperature measuring means is provided for measuring the temperature at a required position of the machine tool, and the speed V at which the lubricating oil advances through the piping is corrected by the temperature Tm measured by the temperature measuring means. [Effects of the Invention]

[0015] According to the spindle device of the machine tool described in 1) above, the preparatory operation time for spreading the lubricating oil over the bearings can be set according to the size of the machine tool, and the preparatory operation for uniforming the lubricating oil in the piping can be properly carried out before switching to normal operation. This means that operation will not be started with an unstable lubricating oil supply, and shortened lifespan and damage to the bearings can be prevented.

[0016] According to the spindle device of the machine tool described in 2) above, by making preparatory operation unnecessary if the stop time since the previous operation is less than a predetermined value, unnecessary preparatory operation can be omitted and preparatory operation can be carried out efficiently.

[0017] According to the spindle device of the machine tool in 3) above, the preparatory operation at low speed in 1) above makes it possible to homogenize the lubricating oil in the piping and prevent a shortage of lubricating oil in the bearings. However, when operating at low speed, the lubricating oil may not be easily discharged, which may result in an excess of oil. In response to this, by operating at S1 or higher in stages for a predetermined period of time in addition to operating with the lubricating oil supplied homogenized, it is possible to prevent an excess of oil and make the lubricating oil in the bearings even more appropriate.

[0018] According to the machine tool spindle device of 4) above, the warm-up operation time Tp required for the lubricating oil to be homogenized and reach the bearings after the machine tool is restarted can be calculated using the experimentally determined speed V at which the lubricating oil advances through the piping and the piping length L, which is set to a different length for each model, as Tp = L / V or Tp = L / V + C. Then, according to 1) above, the maximum allowable low speed rotational speed S1 is set to allow the lubricating oil to be distributed throughout the bearings, and operation at or below S1 is carried out for Tp, thereby enabling a uniform supply of lubricating oil, and if an attempt is made to start operation at or above S1 before the elapsed time of operation at or below the maximum allowable maximum rotational speed S1 during warm-up operation reaches or exceeds Tp, an alarm is displayed and the rotational speed cannot be increased above S1, thereby further optimizing the warm-up operation.

[0019] According to the spindle device of the machine tool described in 5) above, the speed V at which the lubricating oil advances through the piping changes depending on the viscosity of the lubricating oil, and viscosity is affected by temperature. Therefore, by measuring the temperature of the machine tool and correcting V based on this temperature to determine Tp, a more optimized preparatory operation can be carried out. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a block diagram showing an embodiment of a spindle device of a machine tool according to the present invention; [Figure 2] 1 is a flowchart showing a first embodiment of a spindle device of a machine tool according to the present invention. [Figure 3] 5 is a flowchart showing a second embodiment of the spindle device of a machine tool according to the present invention. [Figure 4] 6 is a graph showing a third embodiment of a spindle device of a machine tool according to the present invention. [Figure 5] FIG. 10 is a longitudinal sectional view showing a main part of a spindle device of a conventional machine tool. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, an embodiment of a spindle device for a machine tool according to the present invention will be described with reference to FIGS.

[0022] As shown in FIG. 1, the spindle device (1) of the machine tool of this embodiment includes the spindle (3), bearings (4), and nozzle (5) shown in FIG. 5, as well as a spindle drive device (11) that drives the spindle (3), a lubricating oil supply device (12) that supplies lubricating oil to the nozzle (5), a time measurement device (13) that measures time, a temperature measurement device (14) that measures temperature, and a control device (15) that controls each of these devices (11), (12), (13), and (14).

[0023] The control device (15) is provided with an operation information collection unit (21) that collects operation information of the spindle device (1), a spindle drive control unit (22) that controls the spindle based on data sent from the operation information collection unit (21), and a lubricating oil control unit (23) that controls lubricating oil to be supplied to the nozzle (5) based on data sent from the operation information collection unit (21).

[0024] Compared with conventional spindle devices of machine tools, the spindle device (1) of the machine tool of this embodiment differs from conventional ones in that the spindle drive control section (22) has a preparatory operation control section (31) that properly performs preparatory operation in addition to the conventional normal operation control section (30) that properly performs normal operation, and in that a temperature measuring device (14) necessary for control in this preparatory operation control section (31) is added.

[0025] The preparatory operation control section (31) of the spindle drive control section (22) is configured to perform appropriate control when rotating the spindle (3) after the spindle (3) has stopped. The temperature measuring device 14 is for obtaining the temperature (viscosity of the lubricating oil) of the lubricating oil used in the preparatory operation control unit 31, and is provided with, for example, a temperature sensor installed at a position where it can measure the ambient temperature around the machine tool. The temperature sensor may also be installed so as to directly measure the temperature of the lubricating oil.

[0026] There are two types of lubricating oil supply methods: oil-air lubrication and oil-mist lubrication. In oil-air lubrication, compressed air is supplied into the lubrication pipe, and a device called a mixing valve periodically discharges a fixed amount of lubricating oil into the compressed air in the pipe, mixing the lubricating oil with the air and transporting it, and supplying it to the bearings (4) through a nozzle (5). In oil-mist lubrication, atomized lubricating oil is transported by compressed air and supplied to the bearings (4) through a nozzle (5). Generally, when the spindle (3) stops rotating, the supply of lubricating oil is stopped. During this time, the lubricating oil adhering to the walls of the piping moves due to the influence of gravity, causing unevenness within the piping. The amount of lubricating oil decreases in the sections of the piping facing the direction of gravity, while it tends to accumulate in the sections of the piping facing horizontally. As a result, the next time there is a command to rotate the spindle and the supply of lubricating oil begins, there is a possibility that the supply of lubricating oil will be low until the newly discharged lubricating oil reaches the bearings (4). When the amount of lubricating oil is low, an oil film will not be formed sufficiently, shortening the life of the bearings (4) and causing damage. Conversely, if the lubricating oil in the area where it has been accumulated suddenly flows into the bearing (4), there will be an excess of oil, which will cause a rise in temperature due to viscous resistance, shortening the life of the bearing (4) or causing damage. Therefore, it is ideal to start operation after the newly supplied lubricating oil reaches the bearings (4) in a uniform state. On the other hand, if the lubricating oil is only supplied to a part of the bearings (4) while the rotation is stopped, the lubricating oil is not distributed over the entire bearings (4). Therefore, when restarting operation, the preparatory operation control unit (31) needs to supply the lubricating oil while rotating the main shaft (3) at a low speed.

[0027] The preparatory operation control unit (31) includes a calculation unit (32) that calculates data sent from the operation information collection unit (21) and a determination unit (33) that determines the results obtained by the calculation unit (32).

[0028] The calculation unit (32) is configured to calculate a warm-up operation time Tp, which is the time from when the spindle (3) starts operating until when normal operation of the spindle (3) starts. The warm-up operation time Tp is the time it takes for the lubricating oil discharged by the mixing valve to be homogenized and reach the bearings (4) after the machine tool is restarted, and can be calculated as Tp = L / V, where L is the length of the pipe connected to the nozzle (5) of the machine tool, and V is the experimentally determined speed at which the lubricating oil advances through the pipe. The required warm-up operation time Tp can be calculated by setting a different pipe length L for each model of machine tool. Here, if the maximum allowable low speed rotational speed for spreading the oil over the entire bearing (4) is S1, then operating at or below S1 for Tp time will enable the lubricating oil to be supplied uniformly.

[0029] The determination unit (33) determines whether the relationship between the data is appropriate according to a flowchart described later. If an attempt is made to start operation at S1 or higher before the elapsed time of operation at or below the maximum allowable rotation speed S1 during the warm-up operation reaches or exceeds Tp, the determination unit (33) instructs the display unit (34) to display an alarm, and issues an instruction to the spindle drive device (11) via the spindle drive control unit (22) not to increase the rotation speed above S1.

[0030] Next, an example of the preparatory operation control section (31) will be described with reference to the flowchart of FIG.

[0031] In FIG. 2, first, the pipe length L of the pipe connected to the nozzle (5) of the spindle device (1) is obtained (step S1), and an appropriate warm-up operation time Tp is set based on the pipe length L (step S2). Next, the maximum allowable spindle rotation speed S1 during the warm-up operation time Tp is obtained (step S3). Next, a spindle rotation speed command S0 is obtained (step S4), and the elapsed time T0 from the start of operation to the present is obtained (step S5). Here, first, regarding the spindle rotation speed command S0 obtained in step S4, the magnitude relationship (whether S0 < S1) with the maximum allowable spindle rotation speed S1 obtained in step S3 is checked (step S6). If S0 < S1, the spindle rotation is continued (step S7). Next, regarding the elapsed time T0 obtained in step S5, the magnitude relationship (whether T0 > Tp) with the warm-up operation time Tp obtained in step S2 is checked (step S8). At this time, if T0 ≤ Tp, it is determined that the continuation of the restart control of the operation is necessary, and the process returns to step S4. Conversely, if T0 > Tp in step S8, then S0 < S1 and T0 > Tp, which means that the warm-up operation time Tp has been reached before the rotation speed reaches the maximum allowable spindle rotation speed S1. It is determined that the operation has been restarted properly, and the control is terminated. In step S6, if S0 ≥ S1, similar to step S8, the magnitude relationship (whether T0 > Tp) between the elapsed time T0 and the warm-up operation time Tp is checked (step S9). At this time, if T0 > Tp, then S0 ≥ S1 and T0 > Tp, which means that the warm-up operation time Tp has been exceeded when the rotation speed reaches the maximum allowable spindle rotation speed S1. It is determined that the operation has been restarted properly, and the spindle rotation is continued (step S10), and the control is terminated. Conversely, if T0 ≤ Tp in step S9, then S0 ≥ S1 and T0 ≤ Tp, which means that it is determined that the spindle rotation speed has become S1 or higher (improper operation) before the warm-up operation time Tp is reached. An alarm is displayed (step S11), and the control is terminated so that the rotation speed cannot be increased above S1.

[0032] Next, referring to the flowchart of FIG. 3, another example of the warm-up operation control unit (31) will be described.

[0033] In FIG. 3, compared to the flowchart of FIG. 2, steps Sa and Sb are added before step S1. That is, the process starts by first acquiring the downtime Ts since the previous operation (step Sa). Next, it is determined whether this downtime Ts since the previous operation is equal to or greater than a predetermined value that has been set in advance. If the downtime Ts is equal to or greater than the predetermined value, the process proceeds to step S1 of FIG. 2, and from step 1 onwards, a preparatory operation similar to the steps described with reference to FIG. 2 is performed, and the control is terminated. Then, if the downtime Ts since the previous operation is less than the predetermined value, all steps for performing the preparatory operation are omitted and the control is terminated. As a result, by making the preparatory operation unnecessary if the downtime since the previous operation is less than the predetermined value, unnecessary preparatory operation can be omitted, and more efficient preparatory operation can be performed.

[0034] 2 and 3, the preparatory operation is performed for Tp at a rotation speed of S1 or less, and then immediately transitions to normal operation (the preparatory operation is terminated), but operation at a rotation speed of S1 or more may be performed in stages as a further preparatory operation, as shown in Fig. 4. That is, the flowcharts shown in Fig. 2 and 3 correspond to the time T=Tp in Fig. 4, and steps S2 to S11 may be performed once more (or once more) by replacing Tp, S1, S0, and T0 used in the flowcharts shown in Fig. 2 and 3 with new values.

[0035] In this way, in the flowcharts shown in Figures 2 and 3, it is possible to homogenize the lubricating oil in the piping and prevent a shortage of lubricating oil in the bearings (4) by performing preparatory operation at low speed. On the other hand, operation at low speed may result in poor discharge of the lubricating oil, which may lead to an excess of oil. However, by performing operation at S1 or higher in stages for a predetermined period of time in addition to operation in a state where the supplied lubricating oil is homogenized, it is possible to further optimize the lubricating oil in the bearings (4). [Explanation of symbols]

[0036] (1): Machine tool spindle unit (3):Spindle (4): Bearings (5): Nozzle (11): Main shaft drive unit (12): Lubricating oil supply device (13): Time measuring device (14):Temperature measuring device (15): Control device (21): Operational Information Collection Department (22): Spindle drive control unit (23): Lubrication oil control unit (31): Preparatory operation control unit (32): Arithmetic section (33):Judgment part (34):Display section

Claims

1. In a spindle device of a machine tool, lubricating oil is conveyed by air to lubricate the bearings that support the spindle, A preparatory operation control unit is provided to control the preparatory operation, The preparatory operation control unit displays an alarm when an attempt is made to start operation at S1 or higher before the elapsed time of operation at or below the maximum allowable rotation speed S1 during preparatory operation reaches or exceeds Tp for a set preparatory operation time Tp, and controls the spindle so that the rotation speed cannot be increased above S1.

2. 2. The spindle device of a machine tool according to claim 1, wherein a stop time Ts from a previous operation is acquired, and the preparatory operation is carried out when Ts is equal to or greater than a predetermined value.

3. 3. The spindle device of a machine tool according to claim 1, wherein after the preparatory operation is carried out for a period of time Tp at a rotation speed not higher than S1, an operation at a rotation speed not lower than S1 is carried out in stages as a further preparatory operation.

4. 4. The spindle device of a machine tool according to claim 1, wherein Tp is calculated by Tp = L / V or Tp = L / V + C (C is the time it takes for the lubricating oil to become accustomed to the bearings), where L is the length of the lubricating oil supply pipe and V is the speed at which the lubricating oil advances through the pipe.

5. 5. A spindle device of a machine tool according to claim 4, further comprising a temperature measuring means for measuring a temperature at a required position of the machine tool, and the speed V at which the lubricating oil advances through the piping is corrected by the temperature Tm measured by the temperature measuring means.

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