JP3845757B2 - Spindle device of machine tool and operation method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a spindle device for a machine tool.
[0002]
In this specification, the front end side of the main shaft, that is, the left side of FIGS. 1, 3 and 4 is referred to as the front, and the opposite side is referred to as the rear.
[0003]
[Prior art]
In machine tools, particularly machining centers equipped with a high-speed spindle, a spindle apparatus capable of stable machining in a wide range from low speed to high speed is desired.
[0004]
As a main spindle device of a machine tool, one in which a front portion and a rear portion of a main shaft are rotatably supported with respect to a housing by a rolling bearing is known. An angular ball bearing or the like is used as a bearing of such a main shaft device, and the bearing inner ring is fixed to the main shaft side and the bearing outer ring is fixed to the housing side. In order to prevent the rolling elements of the bearings from slipping and increase the rigidity of the main shaft, the relationship between the axial relative position of the inner ring and the axial relative position of the outer ring is determined so that an appropriate preload is applied to the bearing. It has been.
[0005]
By the way, when the main shaft rotates, the bearing generates heat and a temperature rise occurs in the main shaft. Further, in recent years, the number of spindle apparatuses incorporating an electric motor for driving the spindle has increased, but in that case, the rotor of the motor on the spindle side also generates heat, and the temperature rise of the spindle further increases. The degree of temperature rise of the main shaft varies depending on the rotation speed, especially during high-speed rotation, the temperature rise of the main shaft is large, a large temperature difference occurs between the main shaft and the housing, and the main shaft undergoes thermal deformation in the axial direction of the main shaft. growing. As a result, the relationship between the axial relative position between the bearings of the bearing inner ring fixed on the main shaft side and the axial relative position between the bearings of the bearing outer ring fixed on the housing side changes, and the preload is too low or too high. This causes bearing damage.
[0006]
In order to absorb such thermal deformation of the main shaft, the inner ring of the rolling bearing for rotating and supporting the main shaft with respect to the fixed housing is fixed at a plurality of positions before and after the main shaft, and the outer ring of some of the rolling bearings is fixed inside the fixed housing. 2. Description of the Related Art A spindle device is known that is fixed to a moving housing that is attached to the periphery via a ball bush so as to be axially movable.
[0007]
In the case of this main shaft device, even if thermal deformation occurs in the main shaft, the moving housing moves in the axial direction with respect to the fixed housing, thereby preventing a change in the preload of the bearing. However, there are the following problems.
[0008]
In the above spindle device, the size of the gap between the inner periphery of the fixed housing and the outer periphery of the movable housing is made slightly smaller than the outer diameter of the ball bushing ball, and an appropriate tightening allowance is given to the ball to increase the support rigidity of the spindle. I try to increase it. By the way, if heat is generated in the bearing or the main shaft during rotation of the main shaft, the temperature of the moving housing close to these is larger than that of the fixed housing, and the temperature difference between them and the difference in the thermal deformation in the radial direction between them is large. Occurs. The temperature difference between the movable housing and the fixed housing changes due to the temperature change of the main shaft, and when the temperature difference changes, the gap between the two changes, and the above-mentioned tightening allowance changes. For this reason, if the tightening margin is set so as to be appropriate in a state where the temperature difference is small, the tightening margin is increased in a state where the temperature difference is large, and the compressive force acting on the balls of the ball bushing is increased. The rolling resistance of the ball is increased, and the movement of the moving housing is deteriorated. On the contrary, if the above tightening allowance is set to be appropriate in a state where the temperature difference is large, the tightening allowance becomes small in a state where the temperature difference is small, and the spindle support rigidity is insufficient, which adversely affects the machining accuracy. . In any case, it is impossible to always make the movement of the movable housing smooth and increase the support rigidity of the main shaft regardless of the temperature change of the main shaft.
[0009]
In order to reduce the temperature difference between the moving housing and the fixed housing, a spindle device has been proposed in which cooling oil is circulated inside the moving housing. An example of such a spindle device is shown in FIG. 3, and its rear part is shown enlarged in FIG.
[0010]
In FIG. 3, two places at the front and two places at the rear of the hollow main shaft (10) are rotated with respect to the cylindrical fixed housing (15) by the rolling bearings (11), (12), (13), and (14). It is supported. In this example, the bearings (11) to (14) are all angular ball bearings. The fixed housing (15) includes a cylindrical outer housing member (15a) that is long in the front-rear direction, and a cylindrical front housing member (15b) that is concentrically fixed inside the front portion of the outer housing member (15a). A cylindrical rear housing member (15c) concentrically fixed inside the rear portion of the outer housing member (15a), and the outer housing member (15a) is fixed to the spindle head (16) or the like. Yes. A built-in electric motor (17) for driving the main shaft (10) is provided in a portion between the front and rear housing members (15b) and (15c) in the fixed housing (15). The motor (17) includes a rotor (17a) provided on the outer periphery of the main shaft (10) and a stator (17b) provided on the inner periphery of the outer housing member (15a) around it.
[0011]
The two bearings (11) and (12) on the front side are arranged in the same direction, and these inner rings are spaced apart from the outer periphery of the main shaft (10), and the outer rings are spaced apart from the inner periphery of the front housing member (15b). Fixed.
[0012]
As shown in detail in FIG. 4, the two rear bearings (13) and (14) are arranged in the opposite direction to the front bearings (11) and (12), and these inner rings (13a) ( 14a) is fixed to the outer periphery of the main shaft (10) at an appropriate interval. A ball bush (18) is fitted on the inner periphery of the rear housing member (15c), and a cylindrical movable housing (19) is fitted on the inner periphery thereof. The ball bush (18) is a thin cylindrical retainer that holds a large number of balls (18a) so as to protrude on both sides in the radial direction, and the movable housing (19) is opposed to the housing member (15c). Although it does not rotate, it can move in the axial direction via the ball (18a) of the ball bush (18). A lid (20) is fixed to the rear end of the movable housing (19) protruding rearward from the housing member (15c), and the outer ring of the two bearings (13) and (14) is provided on the inner periphery of the movable housing (19). (13b) and (14b) are fixed at an appropriate interval. Three or more spring accommodating holes (21) are formed at equal intervals in the circumferential direction on the rear end surface of the housing member (15c), and the rear end of the lid (20) corresponding to these holes (21). An outward projecting portion (20a) is formed on the portion. Each hole (21) accommodates a compression coil spring (22) which is an elastic member. The spring (22) presses against the bottom of the hole (21) and the protrusion (20a) of the lid (20) to urge the lid (20) backward. As a result, the movable housing (19) is urged rearward, and as a result, the outer rings (13b) and (14b) of the bearings (13) and (14) are urged rearward to the bearings (11) to (14). Appropriate preload is applied.
[0013]
The bush (23) is fixed to the outer peripheral surface of the moving housing (19) inside the ball bush (18) by shrink fitting. On the outer peripheral surface of the rear end portion of the movable housing (19) and the inner peripheral surface of the front end portion of the bush (23), annular convex portions (19a) and (23a) having the same protruding height are integrally formed over the entire circumference. Between the outer peripheral surface of the annular protrusion (19a) of the moving housing (19) and the inner peripheral surface of the bush (23), and the inner peripheral surface of the annular protrusion (23a) of the bush (23) and the moving housing (19) Are sealed with seals (24) and (25), respectively, so that an annular cooling oil circulation hollow portion (26) (cooling) is provided between the movable housing (19) and the bush (23). A fluid circulation hollow portion) is formed. The cooling oil circulation hollow part (26) is supplied to the protruding part (20a) of the lid (20) via the communication passage (27) formed in the movable housing (19) and the lid (20). It is connected to the joint block (28) for pipe connection. Connected to the joint block (28) is a cooling oil supply pipe (30) from a cooling oil supply device (29) provided with an oil tank, a pump and the like. Although not shown in the drawings, the cooling oil circulation hollow portion (26) has a lid through a communication passage formed in the movable housing (19) and the lid (20) at a position different from the communication passage (27). The cooling oil discharge pipe connecting joint block fixed to (20) is connected to the cooling oil discharge pipe (30) extending to the cooling oil supply device (29).
[0014]
In the above spindle device, even if thermal deformation occurs in the spindle (10), the moving housing (19) moves in the axial direction with respect to the rear housing member (15c) of the fixed housing (15), so that the bearing (11 ) To (14) are prevented from changing in preload. For example, when the thermal deformation of the main shaft (10) increases and the rear part moves to the rear side, the inner rings (13a) and (14a) of the rear bearings (13) and (14) also move to the rear side. The preload of the bearings (11) to (14) is reduced. Then, the preload force acting on the outer ring (13b) (14b) of the bearing (13) (14) is not balanced with the force of the spring (22), and the movable housing (19) and the outer ring (13b) (14b) ) Is pushed to the rear by the spring (22) and stops at a position where both forces are balanced. Conversely, when the thermal deformation of the main shaft (10) is reduced and the rear part thereof moves to the front side, the inner rings (13a) and (14a) of the bearings (13) and (14) also move to the front side accordingly, and the bearing (11 ) To (14) preload increases. Then, the preload force acting on the outer ring (13b) (14b) of the bearing (13) (14) is not balanced with the force of the spring (22), and the movable housing (19) and the outer ring (13b) (14b) ) Compresses the spring (22) and moves forward, stopping at the position where both forces are balanced.
[0015]
Further, during the high speed rotation of the main shaft (10), the temperature of the moving housing (19) becomes higher than the temperature of the housing member (15c) due to the heat generation of the bearings (11) to (14). (29) is supplied to the cooling oil circulation hollow portion (26) and circulates in the hollow portion (26), so that the temperature difference between the movable housing (19) and the housing member (15c) is alleviated. By adjusting the size of the gap, it is possible to keep the tightening allowance of the ball (18a) of the ball bush (18) within an appropriate range. Therefore, regardless of the temperature change of the main shaft (10), the movement of the movable housing (19) is always smoothed, the preload of the bearings (11) to (14) is kept at an appropriate value, and the main shaft (10) Support rigidity can be kept high. Therefore, stable operation from low speed rotation to high speed rotation is possible, and performance such as machining accuracy is improved.
[0016]
However, the spindle device has the following problems. That is, when the spindle (10) that has been rotating at a high speed stops suddenly, there is no heat transfer to the moving housing (19) and the housing member (15c), which have risen in temperature due to heat generated by the bearings (11) to (14). The moving housing (19) having a small heat capacity is cooled more rapidly than the housing member (15c) by the cooling oil supplied into the cooling oil circulation hollow portion (26). For this reason, the contraction amount of the movable housing (19) becomes larger than the contraction amount of the housing member (15c), and the tightening allowance of the ball (18a) of the ball bush (18) becomes too small. Therefore, the support rigidity of the main shaft (10) is reduced, and a large vibration is generated in the main shaft (10) during the subsequent rapid acceleration of the main shaft (10).
[0017]
[Problems to be solved by the invention]
The object of the present invention is to solve the above-mentioned problems and prevent a decrease in the support rigidity of the main shaft even when the main shaft suddenly stops, and a large vibration is generated in the main shaft during the subsequent sudden acceleration of the main shaft. It is an object of the present invention to provide a spindle device for a machine tool that can be prevented.
[0018]
[Means for Solving the Problems and Effects of the Invention]
In the apparatus according to the present invention, an inner ring of a rolling bearing for rotating and supporting the main shaft with respect to the fixed housing is fixed at a plurality of positions before and after the main shaft, and an outer ring of a part of the rolling bearing is inserted into the inner periphery of the fixed housing via a ball bush. The bush is fixed to the outer peripheral surface of the movable housing, and an annular cooling fluid circulation hollow is provided between the outer peripheral surface of the movable housing and the inner peripheral surface of the bush. In the formed spindle device of the machine tool, means for detecting a temperature difference between the movable housing and the fixed housing, and means for controlling the supply of the cooling fluid to the cooling fluid circulation hollow portion based on the temperature difference. It is characterized by having.
[0019]
According to the apparatus of the present invention, when the main shaft rotates at a high speed, the temperature of the moving housing becomes higher than the temperature of the fixed housing due to heat generation of the bearing, and the temperature difference between the moving housing and the fixed housing detected by the temperature difference detecting means is increased. When the set value is exceeded, the cooling fluid supply control means supplies the cooling fluid into the cooling fluid circulation hollow portion to cool the moving housing. Therefore, the temperature difference between the two housings is alleviated, and the size of the gap between the two housings can be adjusted to keep the ball bushing margin of the ball bushing within an appropriate range. As a result, the ball bushing margin of the ball bush can always be kept within an appropriate range. For this reason, regardless of the temperature change of the main shaft, the movement of the movable housing can always be made smooth, the preload of the rolling bearing can be kept at an appropriate value, and the support rigidity of the main shaft can be kept high. Therefore, stable operation from low speed rotation to high speed rotation is possible, and performance such as machining accuracy is improved.
[0020]
When the spindle that has been rotating at high speed stops suddenly, heat transfer to the moving housing and stationary housing, which has risen in temperature due to the heat generated by the bearings, is lost, and the heat capacity is reduced by the cooling fluid supplied into the cooling fluid circulation hollow. The moving housing is rapidly cooled. At this time, when the temperature difference between the movable housing and the fixed housing detected by the temperature difference detecting means becomes a set value or less, the cooling fluid supply control means stops supplying the cooling fluid into the cooling fluid circulation hollow portion, Overcooling of the moving housing is prevented. Therefore, it is possible to prevent the ball bushing of both the housings from being excessively tightened, and to prevent a decrease in the support rigidity of the main shaft. As a result, no vibration is generated in the main shaft during the subsequent rapid acceleration of the main shaft.
[0021]
Apparatus smell of the invention Te, bush is fixed to the outer peripheral surface of the moving housing, a hollow portion for cooling fluid circulation ring is formed between the outer surface and the inner peripheral surface of the bush of the movement housing.
[0022]
In this way, the cooling fluid circulation hollow portion can be formed in the moving housing relatively easily.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0024]
FIG. 1 is a longitudinal sectional view of a rear portion of a main spindle device corresponding to FIG. 4 showing an embodiment of the present invention. In FIG. 1, portions corresponding to those in FIG.
[0025]
In the case of this embodiment, temperature sensors (41) (42) as means for detecting a temperature difference between these are provided at appropriate locations in the movable housing (19) and the rear housing member (15c). . Also, a spring offset solenoid valve (43) using a single solenoid in the middle of the cooling oil supply pipe (30) for supplying the cooling oil from the cooling oil supply device (29) into the cooling oil circulation hollow portion (26). ) Is provided. Each temperature sensor (41) (42) and solenoid valve (43) are connected to a cooling oil supply control device (44) (cooling fluid supply control means).
[0026]
Here, the control operation by the cooling oil supply control device (44) will be described with reference to the flowchart of FIG.
[0027]
The control device (44) detects the temperature T detected by the temperature sensors (41) and (42) from the output signals of the temperature sensor (41) of the moving housing (19) and the temperature sensor (42) of the rear housing member (15c). _i, obtains the temperature difference _T i -T _o of _{T o,} if the temperature difference _T i -T _o with the set value TH is compared with the temperature difference _T i -T _o set value TH or more (step 1 ), The excitation of the solenoid valve (43) is stopped and opened, and the cooling oil is supplied from the cooling oil supply device (29) into the cooling oil circulation hollow portion (26) (step 2). After step 2, return to step 1. If the temperature difference _T i -T _o that less than the set value TH in step 1, is compared with the set value TL and the temperature difference _T i -T _o, the temperature difference _T i -T _o is less than or equal the set value TL If there is (step 3), the solenoid valve (43) is energized and closed, and the cooling oil supply from the cooling oil supply device (29) into the cooling oil circulation hollow portion (26) is stopped (step). 4). After step 4, return to step 1. In Step 3, if the temperature difference _T i -T _o is greater than the set value TL, the flow returns to step 1. Here, the set value TL is a temperature lower than the set value TH by a predetermined temperature, and the solenoid valve (43) is not frequently opened and closed.
[0028]
The structure of the other part in the rear part of the spindle device is the same as that of FIG. Moreover, the structure of the whole spindle apparatus can be made the same as that of FIG. 3, for example.
[0029]
In the above spindle device, in the initial stage of operation, there is almost no temperature difference between the rear housing member (15c) of the movable housing (19) and the fixed housing (15), so the solenoid valve (43) is excited. The cooling oil is not supplied into the cooling oil circulation hollow portion (26).
[0030]
Even if the bearings (11) to (14) generate heat due to the rotation of the main shaft (10) and the temperature of the main shaft (10) rises and the main shaft (10) is thermally deformed, the rear part of the fixed housing (15) When the movable housing (19) moves in the axial direction with respect to the housing member (15c), a change in the preload of the bearings (11) to (14) is prevented. For example, when the thermal deformation of the main shaft (10) increases and the rear part moves to the rear side, the inner rings (13a) and (14a) of the rear bearings (13) and (14) also move to the rear side. The preload of the bearings (11) to (14) is reduced. Then, the preload component force acting on the outer ring (13b) (14b) of the bearing (13) (14) is unbalanced with the force of the spring (22), and the movable housing (19) and the outer ring (13b) (14b) ) Is pushed to the rear by the spring (22) and stops at a position where both forces are balanced. Conversely, when the thermal deformation of the main shaft (10) is reduced and the rear part thereof moves to the front side, the inner rings (13a) and (14a) of the bearings (13) and (14) also move to the front side accordingly, and the bearing (11 ) To (14) preload increases. Then, the preload component force acting on the outer ring (13b) (14b) of the bearing (13) (14) is unbalanced with the force of the spring (22), and the movable housing (19) and the outer ring (13b) (14b) ) Compresses the spring (22) and moves forward, stopping at the position where both forces are balanced.
[0031]
In addition, when the main shaft (10) rotates at high speed, the temperature of the moving housing (19) becomes higher than the temperature of the rear housing member (15c) due to the heat generated by the bearings (11) to (14). When the temperature exceeds TH, the cooling oil is supplied into the cooling oil circulation hollow portion (26) by the cooling oil supply control device (44) as described above, the temperature difference between them is alleviated, and the ball bush (18) The allowance of the ball (18a) can be kept within an appropriate range. As a result, regardless of the temperature change of the main shaft (10), the movement of the movable housing (19) is always smoothed, the preload of the bearings (11) to (14) is kept at an appropriate value, and the main shaft (10) The support rigidity of the can be kept high. Therefore, stable operation from low speed rotation to high speed rotation is possible, and performance such as machining accuracy is improved.
[0032]
Furthermore, when the spindle (10) that has been rotating at a high speed suddenly stops, the moving housing (19) with a small heat capacity is rapidly cooled by the cooling oil circulating in the cooling oil circulation hollow portion (26). When the temperature difference between the movable housing (19) and the rear housing member (15c) becomes less than the set value TL, the cooling oil supply control device (44) enters the cooling oil circulation hollow portion (26) as described above. The cooling oil supply is stopped and overcooling of the movable housing (19) is prevented. Therefore, it is possible to prevent the ball bushing of both housings from being excessively tightened, and to prevent the support rigidity of the main shaft (10) from being lowered. As a result, vibrations during rapid acceleration to the main shaft (10) does not occur in the subsequent main axis (10).
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of a rear portion of a spindle device showing an embodiment of the present invention.
FIG. 2 is a flowchart showing an example of a control operation by a cooling oil supply control device.
FIG. 3 is a longitudinal sectional view of a spindle device showing a conventional example.
4 is an enlarged longitudinal sectional view showing a rear part of FIG. 3. FIG.
[Explanation of symbols]
(10): Spindle
(11) (12) (13) (14): Ball bearing (rolling bearing)
(11a) (12a) (13a) (14a): Inner ring
(13b) (14b): Outer ring
(15): Fixed housing
(15c): Housing member
(18): Ball bush
(18a): Ball
(19): Moving housing
(26): Cooling oil circulation hollow (cooling fluid circulation hollow)
(41) (42): Temperature sensor (temperature difference detection means)
(44): Cooling oil supply control device (cooling fluid supply control means)

Claims (1)

The inner ring of a rolling bearing for rotating and supporting the main shaft with respect to the fixed housing is fixed at multiple locations on the front and rear of the main shaft, and the outer ring of some of the rolling bearings can move in the axial direction on the inner periphery of the fixed housing via a ball bush. A machine tool that is fixed to an attached moving housing, a bush is fixed to the outer peripheral surface of the moving housing, and an annular cooling fluid circulation hollow is formed between the outer peripheral surface of the moving housing and the inner peripheral surface of the bush In the spindle device of
A machine tool comprising: means for detecting a temperature difference between the movable housing and the fixed housing; and means for controlling the supply of the cooling fluid to the cooling fluid circulation hollow portion based on the temperature difference. Spindle device.

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