JP3982196B2 - Grinding machine equipped with steady rest and grinding method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a grinding machine provided with a touch-stop device for supporting a journal of a crankshaft and a grinding method thereof. More specifically, the present invention relates to a grinding machine and a grinding method provided with a steady rest device for supporting a journal for rotating a crankshaft around a journal to grind a crankpin.
[0002]
[Prior art]
In a grinding machine that grinds the crankpin of the crankshaft, it rotates around the journal shaft center of the crankshaft according to the machining program set in the numerical control device, and the crankpin rotates around the journal. The forward / backward feed is controlled synchronously with the rotation of the crankshaft so that the wheel head can be advanced and retracted in response to changes in the angular position during the movement.
[0003]
In general, the crankshaft has low rigidity and generates a deflection when subjected to grinding resistance by a grinding wheel. For this reason, in a grinding machine that rotates around the journal axis as described above to grind the crankpin, the entire crankshaft is deflected by the grinding resistance applied to the crankpin and the journal axis is displaced from the center of rotation. become. If grinding of the crankpin is continued in this state, an error will occur in the shape and roundness of the crankpin, and if the grinding resistance is further increased, the entire crankshaft will vibrate greatly, causing the crankshaft to fall off and grinding itself. May not be possible.
[0004]
Conventionally, when the workpiece is a simple cylinder, a tapping device that presses the crankshaft from the direction opposite to the pushing direction of the grinding wheel is used as a method for preventing the deflection. However, in the grinder that grinds the crank pin by rotating around the journal axis as described above, the crank shaft rotates around the journal axis, so that the crank pin rotates. It was difficult to press. For this reason, in order to prevent the journal axis from deviating from the center of rotation, the journal is held by a touch-stop device to prevent crankshaft deflection.
[0005]
[Problems to be solved by the invention]
However, when the journal is held by the steady rest device, the rotational motion accuracy of the crankpin is affected by the roundness accuracy of the journal portion. Further, when there is a coaxiality error between the center hole, which is the processing standard of the journal held by the steady-rest device and the crankshaft, or between both end journals, the crankshaft receives a bending force that varies with rotation. This force causes an error in the revolving motion of the crankpin and an error in shape and roundness. In particular, as shown in FIG. 2, the three-point support type steady rest device that holds the angular position of every 120 degrees of the journal circumference has a high holding force. However, it is easy to be affected by the roundness of the journal.
Therefore, a main object of the present invention is to prevent roundness error due to circular motion error of the crankpin and improve grinding accuracy.
[0006]
[Means for Solving the Problems]
The present invention provides a grinding method for solving the above-described problems, and the gist thereof is to enable high-efficiency grinding without causing bending of the crankshaft in grinding processing with a relatively large load. Grind by holding the crankshaft journal with a steady rest.
On the other hand, in the final finishing process with a relatively small load, the journal holding of the steady rest is released and the crankshaft is rotated with two-point support between both center holes of the crankshaft machining reference or both end journals. On the other hand, the pin part that performs a circular motion without error is ground.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an embodiment in which the present invention is applied to a grinding machine for machining a crankpin. A grinding wheel base 8 is provided on a bed 1 on a Z-axis guide rail 2 in the longitudinal direction (Z-axis direction). The Z-axis table 6 to be placed is slidably provided by the feed screw 3, and a grinding wheel base 8 that rotatably supports the grinding wheel 14 is provided on the Z-axis table 6 more precisely in the radial direction of the crankshaft W described later. Is slidable by a feed screw 12 in the front-rear direction (X-axis direction) orthogonal to the Z-axis direction.
[0008]
A headstock 17 and a tailstock 18 are installed in front of the grindstone table 8 in the longitudinal direction, and a crankshaft W, which is a workpiece, is supported by a pair of left and right centers therebetween. The headstock 18 is provided with a C-axis servomotor 19 for driving the rotation of the crankshaft, and can be driven to rotate by gripping the shaft end of the crankshaft W by the drive pin 20, and its rotational position is provided at the rear end of the motor 19. Detected by the encoder 19E, the one tailstock 18 is configured to press and support the axis of the crankshaft W at its center.
[0009]
Each of the feed screws 3 and 12 is rotationally driven by an encoder-equipped servomotor controlled by a numerical controller described later. That is, a servo motor 25 with an encoder 25E is provided at the left end of the feed screw 3 for moving the Z-axis table 6 on which the grinding wheel head 8 is placed in the Z-axis direction. On the Z-axis table 6, a servomotor 27 with an encoder 27 </ b> E is provided at the end of the feed screw 12 for sliding the grinding wheel base 8 in the front-rear direction (X-axis direction). The grindstone base 8 supports the grindstone 14 so that it can be rotationally driven by a built-in motor (not shown).
[0010]
On the bed 1, a three-point support type steady rest device 30 is disposed on the opposite side of the grinding wheel base 8 with the crankshaft W interposed therebetween. The steady rest device 30 is provided with a feed screw 33 and an encoder-equipped servo motor 34 for indexing and moving the rest head 32 in the Z direction on the rest base 31.
As shown in FIG. 2, the housing 35 of the rest head 32 includes a hydraulic cylinder 36 at the lower portion, and reciprocates in a direction perpendicular to the rotation axis of the crankshaft W (X direction) with respect to a base 37 moved by a feed screw 33. Moving.
[0011]
In the housing 35, a hollow hole 38 formed at a position corresponding to the height of the rotation axis of the crankshaft W supported by the main shaft 17 in the vertical direction (that is, the height of the main shaft of the grindstone head H), A sliding body 39 is fitted so as to be slidable forward and backward.
A first support arm 40 is fixed to the front end of the sliding body 39 exposed from the housing 1.
A drive shaft 41 is rotatably supported at the rear end of the hollow hole 38. The front end side of the drive shaft 41 protrudes into the center hole 42 of the sliding body 39 and is formed with a threaded portion 44 that is screwed into a female screw sleeve 43 fitted to the rear end opening side of the center hole 42 of the sliding body 39. By making the drive shaft 41 rotate, the sliding body 39 advances and retreats in the hollow hole 38. A gear mechanism 45 is attached to the rear end side of the drive shaft 41. The gear mechanism 45 is coupled to an output shaft of a servo motor 46 attached to the side surface of the housing 35.
[0012]
In the front surface of the housing 35 and in the vertical direction of the first support arm 40, a pair of second support arms 47 and third support arms 48 are provided so as to be rotatable about an axis parallel to the support shafts 49 and 50.
[0013]
The second support arm 47 and the third support arm 48 are brought into contact with and separated from the first support arm 40 around the axis of the support shafts 49 and 50 by a hydraulic cylinder (not shown) connected to the hydraulic control device 83. The turn is controlled.
In the case of a four-cylinder crankshaft exemplified in the grinding, the rest head 35 is moved to three positions in the center, that is, a position facing the second to fourth journals J2, J3, J4 from the tailstock 18 side. 34 is selectively determined. At this indexing position, the housing 35 moves forward depending on the cylinder 36, so that the first support arm 40 whose position has been adjusted in advance by the servo motor 46 in accordance with the shearal diameter comes into contact with the journal. At the same time, the second support arm 47 and the third support arm 48 are closed by the hydraulic pressure from the hydraulic control device 83, so that the journal is sandwiched as shown in FIG.
[0014]
The general configuration of the grinding machine according to the embodiment of the present invention is as described above. The crankshaft W is supported between the headstock 17 and the tailstock 18 and the left Z-axis table 6 is servoed during grinding. The grindstone 14 is indexed to a position where the grindstone 14 is aligned with the crank pins P1 to P4 by the motor 25, and the rest head is indexed to the position of the journal near the crankpin from which the grindstone 14 is indexed by the servo motor. The first support arm 40 is brought into contact with the journal and the second support arm 47 and the third support arm 48 are closed to sandwich the journal, thereby fixing the journal at the center of rotation.
Next, the servo motor 19 of the headstock 17 is rotated to rotate the crankshaft W. At that time, the crankshaft W is rotated on the axis of the journal, so that the crankpin as a machining portion rotates around the journal. Then, the grinding wheel base 8 is advanced by the feed amount of rough grinding by the servo motor 27. At that time, since the crank pin which is a machining part is revolving, the grinding wheel 14 is ground while moving the grinding wheel base 8 back and forth in synchronization with the rotation of the spindle servo motor 19. This synchronous motion is superimposed on the servo motor 27 to give a cutting forward motion, and it is operated to gradually grind to a rough machining dimension.
[0015]
When the crankpin is ground to the rough machining size by the grinding wheel 14, the second support arm and the third support arm are opened, and the housing is retracted to move the journal by the first support arm, the second support arm, and the third support arm. Holding is released.
During this time, the crankpin moves around the journal without stopping, and is advanced by the feed amount of finish grinding by the servo motor 27 of the grinding wheel base 8. At that time, since the crank pin which is a machining location makes a circular motion, the grinding wheel 14 is ground while the grinding wheel base 8 is moved back and forth in synchronization with the rotation of the spindle servo motor 19 by the control means. This synchronous motion is superimposed on the servo motor 27 to give a cutting forward motion, and it is operated so as to gradually grind to the finished machining completion dimension.
Note that the sizing device 51 performs switching of the feed amount of the grindstone table 8 when the rough machining completion dimension is reached and completion of the machining by reaching the finishing machining dimension. The sizing device 51 is placed on the grindstone base 8 as shown in FIG.
This sizing device 51 is a known follow-up sizing device (for example, manufactured by Marposs, Italy) of a type that performs dimensional measurement by following the crank pin P that is turning during continuous grinding. A second arm 54 is pivotally supported at the tip of a first arm 53 that is pivotally supported by a support member 52 on the grinding wheel base 8 and extends forward of the grinding wheel 14, and further, a measurement for measuring at a right angle to the tip of the second arm 54. The bar 55 is fixed. The measuring rod 55 has a measuring head composed of a V block 56 fixed to the lower end thereof and in contact with the outer periphery of the crankpin P, and a probe 57 provided at the center thereof so as to be freely movable back and forth. It is the structure which detects the forward and backward movement and outputs it as an electrical signal. A guide member 58 is fixed to the tip of the V block 56 and serves as a guide for the V block 56 to engage with the crank pin P.
[0016]
A hydraulic cylinder 60 for moving the measuring rod 55 to the rest position (two-dot chain line position) and the measurement position (solid line position) on the grinding wheel base 8 by contacting an operation piece 59 integrated with the first arm 53. An actuating device is provided. The protrusion 62 of the support piece 61 protruding forward from the lower surface of the distal end of the first arm 53 works so as to abut against the lower surface of the second arm 54 at the rest position and hold the second arm 54 horizontally. By returning the piston 60a of the hydraulic cylinder 60 from the rest position of the two-dot chain line, the measuring rod 55 gradually descends. First, the guide member 58 comes into contact with the crankpin P, and the crankpin P moves along the guide member 58 to V The second arm 54 is configured to engage with the block 57, and at that time, the second arm 54 can move freely away from the protrusion 62 of the support piece 61.
[0017]
Next, a control system for controlling the grinding machine of the embodiment will be described with reference to FIG. The present control system includes a numerical control device 70, and the numerical control device 70 is configured by connecting a CPU 71 and ROM 73 and RAM 74, which are storage devices, to each other. The CPU 71 is connected to the X-axis motor control circuit DUX via the interface 76, and the S-axis motor control circuit DUS and the T-axis motor control circuit DUT for controlling the Z-axis motor control circuit DUZ and the rest device 30 via the interface 78. The C-axis motor control circuit DUC for controlling the spindle motor 19 and the sequence controller 79 are connected. These motor control circuits DUX, DUZ, DUS, DUT and DUC drive the corresponding servo motors 19, 27, 25, 34 and 36, respectively, and return signals from the encoders 19E, 27E, 25E, 34E and 36E of these servo motors, respectively. Connected to receive.
[0018]
An operation panel 81 having a CRT, a numeric keypad, and the like is connected to the CPU 71 via an interface 80. The ROM 73 stores a system control program and the like, and the RAM 74 stores a machining control program and the like. Further, the measuring head of the sizing device 51 provided on the grinding wheel head 8 is connected to the CPU 71 via an interface 82 including an A-D converter.
Next, a specific grinding operation which is a feature of the present invention will be described with reference to the flowchart of FIG.
[0019]
A crankshaft W is attached between the centers of the headstock 17 and the tailstock 18 by an operator. When attaching and detaching the crankshaft, the grinding wheel base 8 and the rest head 32 are both in the retracted standby position, and the second support arm 47 and the third support arm 48 of the rest head 32 in the standby position are opened. is there.
Thereafter, when a grinding execution command is issued from the operation panel 81 to the numerical controller 70, the operation of the flowchart of FIG. 4 is executed, and the sequence counter N formed in the RAM 74 is set to the initial value “1” ( Step 90). Next, it is determined whether or not the order counter N is greater than “5” indicating that grinding of all the crank pins has been completed. (Step 92) Since the order counter N is “1” in this state, the determination is “NO”, and the table indexing is executed as the next processing (Step 94). The index position storage table IPMT shown in FIG. 5 is formed in the RAM 74, and when the processing order N is specified, the crankpin to be processed and the journal to be supported by the rest device 30 are previously stored by the operator using the operation panel 81. It is specified. In this case, since the processing order is “1”, the servo motor 25 is operated, the table 6 is indexed to the position where the grindstone 14 is aligned with the crank pin P2, and then the servo motor 19 is operated to operate the crank pin. P2 is indexed to the horizontal machining start position closest to the grindstone side shown as the position (b) in FIG. 6 (step 96).
[0020]
Next, by the operation of the servo motor 34, the rest head 32 is indexed to a position aligned with the central journal J3. When the rest head is indexed to the position aligned with the journal J3, the sequence controller outputs a command to advance the housing of the less head to the hydraulic control device 83, and the tip of the first support arm contacts the journal J3. At the same time, the servo motor 27 is operated to advance the grinding wheel head 8 forward toward the crankshaft W. (Step 98) The forward feed amount is set in advance so that the grinding wheel 14 is stopped at a position having a slight gap from the crankpin P2 and the journal J3.
[0021]
When the fast-forwarding is completed, the second support arm 47 and the third support arm 48 are instructed to close continuously, and the second support arm 47 and the third support arm 48 sandwich the journal J3 with a predetermined hydraulic pressure by the hydraulic control device 83. Thus, the journal J3 is fixed at a position coinciding with the rotation axis of the main shaft. (Step 100).
[0022]
Next, rough grinding feed of the grinding wheel base 8 is executed (step 102). In this rough grinding, the servo motor 19 and the servo motor 27 are synchronously controlled according to the profile data. As shown in FIG. 6, the profile data includes a position (XΘ) from the crankshaft rotation axis of the grindstone table 8 with respect to the rotation angle (Θn) from the machining start position (A) of the crankpin P, for example, the crankshaft rotation angle. This is determined every 0.5 degrees, and is registered in the RAM 74 in advance. The servo motor 27 for the grinding wheel base 8 superimposes the rough grinding feed, that is, the cutting of the grinding wheel 14 with respect to the crank pin P2 with respect to the advance / retreat movement based on the profile data, whereby the grinding wheel 14 rotates around the crank pin P2. It is gradually cut and advanced while moving forward and backward with movement.
[0023]
In the course of this rough grinding process, the cylinder 60 of the sizing device 51 shown in FIG. 3 retracts the piston rod 60a, engages the V bevel 56 with the crank pin P2, and starts measurement. This measurement start command is executed by a signal from the sequence controller 79. The movement to the measurement position of the sizing device is performed so that the crank pin P tracks the V bevel 56 while the crank pin P turns and descends from the position (b) of FIG. In this case, the rotational speed of the crankshaft W may be decreased so that the V bevel 56 can be accurately engaged by the crankpin P. Alternatively, the measurement pin advance operation of the V bevel 56 may be executed in a state where the crank pin P is temporarily stopped at the phase (b) of FIG.
Thus, since the journal J3 is held by the steadying device 30, the axis of the crankshaft W is maintained substantially at the axis of rotation, and in particular, bending of the crankshaft W due to grinding resistance is prevented, and the three-point supported steadying is prevented. The crankshaft W in a state can perform a stable circular motion even when an external force is applied.
[0024]
In this way, the rough grinding of the crank pin P2 proceeds, and during this time the measuring head monitors the dimensions of the crank pin P2. (Step 104) When the crank pin P2 is roughly ground to a predetermined dimension, a command to retract the housing 35 of the less head 32 is output to the hydraulic control device 83 via the sequence controller 79, and the first support arm 40 tips separate from journal J3. Subsequently, a command to open the second support arm 47 and the third support arm 48 is issued, and the fixing of the journal J3 by the steady rest device is released by these commands. (Step 106). At this time, the crankshaft W performs a circular motion while being held only by a reference portion such as a center hole. That is, it makes a circular motion without the influence of the poor circularity of the journal that occurs when the journal is held by the steady rest. Finish grinding is performed in this state. (Step 108)
[0025]
In the finish grinding, the grinding wheel head 8 is cut and advanced at a cutting speed slower than the rough grinding feed speed, and this cutting feed is superposed on the forward / backward movement based on the profile data, whereby the crankpin P2 is finish-ground at a slower grinding speed. (Step 110). In addition, since the feed of the grindstone table 8 in finish grinding is very small as compared with rough grinding, grinding can be performed with almost no bending of the crankshaft.
[0026]
When the crank pin P2 reaches a predetermined finishing dimension (step 112), final spark-out grinding is performed while the crankshaft W rotates a predetermined number of times (step 114), and the grinding process is completed.
After grinding, “1” is added to the machining order counter N (step 116), the process returns to step 83, and the processing of steps 94 to 112 is repeated as described above until the machining order counter becomes larger than “4”. Thus, the remaining crank pins J1, J3 and J4 are ground. Then, when the machining order counter N becomes larger than “4” in the step, the grinding is finished, the grinding wheel base 8 returns to the original position (step 118), and the processing is finished.
[0027]
In this way, since the grinding resistance by the grindstone 14 is large during rough grinding, the crankshaft is bent to prevent the grinding accuracy from being deteriorated by supporting the journal. In finish grinding, the grinding resistance by the grindstone is small and the crankshaft is small. Therefore, in order to prevent the rounding motion of the crankpin from being affected by the roundness of the journal, the steady rest device 30 does not support the journal, and both ends of the crankshaft W are connected to the headstock 17. And supported only by the center of the tailstock 18. As a result, the crankpin can be ground with high accuracy.
In particular, the grinding machine using the three-point steadying device 30 shown in the present embodiment is effective because the journal holding force of the steadying device 30 is high.
[0028]
In the above embodiment, the journal located closest to the crankpin is supported during rough grinding. However, the present invention is not limited to this, and a crankshaft having a relatively small deflection (including a case where the length is short). Then, if the journal located in the center of the crankshaft is supported regardless of the position of the crankpin that grinds, there is no need to move the rest head, so there is no need to provide a servo motor or ball screw, and the grinding machine Can be simplified.
A plurality of steady rest devices may be provided. Furthermore, without completely releasing the steady rest support during finish grinding, the hydraulic pressure of the hydraulic control device 83 is lowered during finish grinding, so that the holding force of the journal by the steady rest device (for example, about 20% of the retention force during rough grinding) is reduced. You may make it reduce and grind.
In the above embodiment, only two grinding cycles of rough grinding and finish grinding have been described. However, finish grinding includes fine grinding and fine grinding.
[0029]
【The invention's effect】
As described above, as described in claim 1 of the present invention, the journal is supported by the steady rest device during rough grinding, and only the both ends of the crankshaft are supported during finish grinding. High-efficiency grinding with a large grinding force is possible by preventing falling off. On the other hand, pin grinding can be performed with high precision without being affected by the precision of the journal during finish grinding. As a result, highly accurate pin grinding can be performed in a short time. Further, if the journal closest to the pin to be ground is supported as in claim 2, the deflection can be most effectively prevented. According to the fourth aspect of the present invention , high-efficiency grinding with a large grinding force can be performed by preventing the crankshaft from being bent or dropped during rough grinding, while being not affected by the accuracy of the journal during finish grinding. Thus, a grinding machine capable of highly accurate pin grinding can be obtained. According to the fifth aspect of the present invention, it is possible to provide a grinding machine that can most effectively prevent the deflection, and to provide a grinding machine capable of performing highly accurate grinding.
[Brief description of the drawings]
FIG. 1 is a plan view of a crankpin grinder as an embodiment of a grinder according to the present invention.
FIG. 2 is a side view showing a rest head of a steady rest device used in a crankpin grinding machine.
FIG. 3 is a side view showing a sizing device used in a crankpin grinding machine.
FIG. 4 is a flowchart of a system control program executed by a numerical control device of a crankpin grinder.
FIG. 5 is an explanatory diagram showing an index position storage table formed in the RAM of the numerical controller.
FIG. 6 is an explanatory view showing a relationship between a turning phase of a crank pin and a feed position of a grindstone.
[Explanation of symbols]
1: Bed, W: Crankshaft (workpiece), 17: Main spindle, 18: Tailstock, 8: Grinding wheel, 14: Grinding wheel, 30: Stabilizer, 32: Rest head, 40: First support arm 47: second support arm 48: third support arm 70: numerical control device

Claims (5)

A workpiece support device for rotating both ends of a crankshaft having a plurality of axially arranged crankpins around a journal axis on a bed and rotating the crankpin around the journal, and rotating a grindstone A grindstone bed that can be held and can move forward and backward in a direction perpendicular to the axis of the crankshaft on the bed, and a circular movement around the journal of the crankpin by the workpiece support device and the advance and retreat of the grindstone bed are controlled synchronously In a grinding machine provided with a numerical control device for grinding and a steadying device for holding the journal of the crankshaft , a rough grinding process in a series of grinding cycles for one grinding processing portion is performed by the steadying device. after it was kept for the steadying the finish grinding step following the rough grinding step in the series of grinding cycles Grinding method according grinding machine provided with a steady rest and performs the wheel head by releasing the holding by the location is advanced cut at a slower infeed rate than the rough grinding feed.   The grinding method of a grinding machine provided with the steady rest device according to claim 1, further comprising a steady rest device that holds the journal at a position closest to a position of a crankpin to be roughly ground by the steady rest device. Grinding method using a grinding machine.   The grinding method for a grinding machine provided with the steady rest device according to claim 1, wherein the journal located at the center of the crankshaft is held by the steady rest device regardless of the position of the crankpin to be roughly ground. A grinding method using a grinding machine equipped with a steady rest device. A workpiece support device for rotating both ends of a crankshaft having a plurality of axially arranged crankpins around a journal axis on a bed and rotating the crankpin around the journal, and rotating a grindstone A grindstone bed that can be held and can move forward and backward in a direction perpendicular to the axis of the crankshaft on the bed, and a circular movement around the journal of the crankpin by the workpiece support device and the advance and retreat of the grindstone bed are controlled synchronously In a grinding machine provided with a numerical control device that performs grinding and a steadying device that holds a journal of the crankshaft, the numerical control device performs a rough grinding step in a series of grinding cycles for one grinding processing point. after it performed holding the journal by steady rest, finishing Labs following said rough grinding step in the series of grinding cycles Characterized by comprising an anti-sway control means for controlling the anti-sway device so as to perform the process by releasing the holding by the anti-sway device and moving the grindstone table at a cutting speed slower than the rough grinding feed. A grinding machine equipped with a steady rest.   5. A grinding machine provided with the steadying device according to claim 4, further comprising a moving means for moving the steadying device relative to the crankshaft in an axial direction thereof, wherein the control device is a crank pin for grinding by the moving means. A grinder equipped with an anti-skid device, comprising indexing control means for indexing the anti-skid device to the position of the nearest journal.

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