JPH0338071B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a truing device for shaping the outer peripheral surface of a grinding wheel into a perfect circle in a grinding machine.

<Prior art> The roundness of the outer circumferential surface of a grinding wheel in a grinding machine or the like affects the machining accuracy of a workpiece. In particular, hard grinding wheels containing diamond or CBN abrasive grains are used to grind difficult-to-cut materials such as cemented carbide and ceramics. When the grinding wheel vibrates in the direction of , it scrapes the surface of the grinding wheel and generates uneven undulations, and vibration occurs during grinding and self-excited chatter deteriorates the machining accuracy of the workpiece. Therefore, a truing device is used to shape the outer peripheral surface of the grinding wheel into a perfect circle.

This truing device has a truing head that can feed and move the grinding wheel in the traverse direction of the axis parallel to the axis of the grinding wheel and in the plunge direction perpendicular to the axis of the grinding wheel, and rotates the truer axis along the axis parallel to the axis of the grinding wheel. The grinding wheel is rotated by the grinding wheel, which is rotated by the grinding wheel, which is rotated by the grinding wheel, which is rotated by the grinding wheel, which is rotated by the grinding wheel. be.

<Problems to be Solved by the Invention> However, conventional truing devices are not equipped with means for automatically verifying the roundness of the grinding wheel. Therefore, it is not possible to judge whether the grinding wheel has become a perfect circle during truing, and since truing is performed with the amount of truing estimated in advance, the amount of truing may be more than necessary, especially compared to a normal grinding wheel. For grinding wheels containing expensive diamond or CBN abrasive grains, there is a problem in that it is uneconomical to perform truing with an amount of truing greater than necessary.

<Means for Solving the Problems> In order to solve the above conventional problems, the present invention rotatably supports a true shaft or a grindstone shaft by a fluid bearing, and reduces the pressure in the plunge direction of the fluid bearing. a pressure detection means for detecting the pressure fluctuation, a means for determining whether the fluctuation in the pressure has become below a certain level, and a feed control device for controlling the feed movement of the truss head based on the signal from the determination means, This makes it possible to automatically verify the roundness of the whetstone.

<Examples> Examples of the present invention will be described below based on the drawings. In Figure 1, 1 is a grinding wheel head, 2 is a grinding wheel head 1
The grindstone shaft is rotatably supported by the grindstone shaft, and is rotationally driven by a drive motor (not shown). 3 is a grinding wheel fixed on the grinding wheel shaft 2. Reference numeral 4 denotes a truing device, which is provided integrally with the grindstone head 1 in the illustrated example, but may also be installed on the headstock.

The configuration of this truing device 4 will be explained based on the case where it is provided on the illustrated grindstone head 1. 1st
As shown in the figure, a table 5 is provided on the whetstone head 1,
A sliding surface 6 in a direction parallel to the axis of the grinding wheel shaft 2 is formed on this table 5, and this sliding surface 6
The traverse table 7 is slidably guided. 8 is a traverse feed motor that moves the traverse table 7 in the left direction L and right direction R;
One end of a screw shaft 9, which is rotated forward and backward by the traverse feed motor 8, is screwed into the traverse table 7.

10 is a ram part, which is attached to the traverse table 7 in an axial direction perpendicular to the axis of the grinding wheel shaft 2 (plunge direction).
The truing head 11 is integrally connected to the tip of the truing head. 12 is a plunge feed motor, and a feed screw 13 is rotated in forward and reverse directions by this plunge feed motor 12.
One end is screwed into the rear end of the ram part 10.

A dog 32 is fixed to the traverse table 7, and the dog 32 is fixed at the rightward R end of the traverse table 7.
A limit switch 31 operated by a limit switch 31 is arranged on the table 5.

As shown in FIG. 2, in the truing head 11, a truer shaft 14 is rotatably supported by a fluid bearing 17 along an axis parallel to the axis of the grindstone shaft 2. As shown in FIG. The fluid bearing 17 has a bearing pocket 1 for supporting the truer shaft 14 under static pressure in the radial direction.
8, an axial discharge groove 21 and an annular discharge groove 19, 2.
0.

Furthermore, as shown in FIG.
is provided. And this pressure outlet 2
2 and 23 are connected to a differential pressure detector 24 that detects the pressure difference between the left and right bearing pockets 18. Further, a band pass filter 25, a gate circuit 26, an amplitude detector 27, a comparator circuit 28, and a flip-flop 29 are connected in this order from the differential pressure detector 24, and the plunge feed motor is connected to the flip-flop 29 and the gate circuit 26. 12 and a feed control device 30 that controls the traverse feed motor 8 is connected.

The bandpass filter 25 is the differential pressure detector 2
Remove the DC component of the differential pressure fluctuation detection signal from 4,
It also removes noise. Amplitude detector 2
7 detects the maximum and minimum difference among the fluctuations in the pressure difference over a certain period of time. If the amplitude detected by the amplitude detector 27 is smaller than the preset amplitude, a signal is sent to the comparator circuit 28 to set the flip-flop to "1". Flip-flop 29 holds the set signal. Further, the feed control device 30 receives a signal in which the flip-flop 29 is set to "1", and sends a signal to the flip-flop 29 to reset it to "0". Furthermore, the feed control device 30
sends an opening/closing signal to the gate circuit 26. That is, by stepping on the limit switch 31 during the return stroke of the truing head 11 (to the left), a signal to open the gate circuit is sent, and by turning off the limit switch 31, a signal to close the gate circuit is sent. However, even if the limit switch 31 is depressed during the cutting (rightward R) stroke of the truing head 11, no signal is sent to open the gate circuit.

Since the present invention has the above-mentioned configuration, as shown in the flowchart of FIG. 4, as a truing cycle, the following operations are repeated until the traverse 3 becomes a perfect circle. be exposed. If there is a runout on the outer periphery of the grinding wheel 3 at the time when the cutting is applied, there is a fluctuation in the truing resistance corresponding to this runout, and the fluid bearing 1
Pressure fluctuations occur in the bearing pocket 18 of 7. When this pressure fluctuation level falls below a certain value, the comparison circuit 28 determines that truing is OK. In other words, the pressure fluctuation is large when a depth of cut is applied, and the amplitude is detected for a certain period in the middle of leftward movement L excluding this fluctuation, that is, while the limit switch 31 is depressed by the dog 32, and if OK, the flip-flop is At step 29, the OK signal is held, and one cycle of cutting is completed. That is, when the truing head 11 reaches the leftward advance end, the feeding of the truing head 11 is stopped and the truing is completed.

<Other Embodiments> In the embodiment described above, differential pressure fluctuations between the two left and right bearing pockets 18 of the hydrodynamic bearing 17 are detected.
Pressure fluctuations in two bearing pockets 18 may also be detected. Furthermore, the object of the present invention can be achieved by detecting the pressure in the plunge direction of the grindstone bearing instead of detecting the pressure in the plunge direction of the truer shaft.

<Effects of the Invention> As described above, according to the present invention, the roundness of the grinding wheel is automatically verified based on the fluctuation level of the bearing pocket pressure in the plunge direction of the true bearing or the grindstone bearing during truing, so that the grinding wheel is constantly grounded. It is now possible to true the grinding wheel into a highly accurate perfect circle, and it can also be verified during the truing, which eliminates the need for more truing than is necessary and has the economical effect of extending the useful life of expensive grinding wheels. have.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention, and FIG. 1 is a plan view, FIG. 2 is an enlarged cross-sectional view taken from FIG. 1, and FIG.
FIG. 3 is a sectional view taken along the line shown in FIG. 2, and FIG. 4 is a flowchart showing a truing cycle according to the present invention. DESCRIPTION OF SYMBOLS 1... Grinding wheel head, 2... Grinding wheel shaft, 3... Grinding wheel, 4... Truing device, 7... Traverse table, 8... Traverse feed motor, 10... Ram part, 11... Truing head, 12...Plunge feed motor, 14...Trua shaft, 15...
...Trua, 17...Fluid bearing, 18...Bearing pocket, 22, 23...Pressure outlet, 24...Differential pressure detector, 25...Band filter, 26...Gate circuit, 27...Amplitude detector , 28... Comparison circuit, 29... Flip-flop, 30... Feed control circuit, 31... Limit switch, 32... Dog.

Claims (1)

[Claims] 1. A grinding wheel rotatably provided on a grindstone head by a grindstone shaft can be fed and moved in a traverse direction of an axis parallel to the axis of the grindstone shaft and in a plunge direction perpendicular to the axis of the grindstone shaft. In a truing device in which a truer shaft having an axis parallel to the axis of the grinding wheel shaft is rotatably supported in a truing head, and a truer is provided on the truing shaft, the truer shaft or the grinding wheel shaft is rotatably supported by a fluid bearing. , a pressure detection means for detecting the pressure in the plunge direction of the fluid bearing, a determination means for determining whether the fluctuation in the pressure has become below a certain level, and a signal from the determination means to control the feed movement of the pull head. A grinding wheel truing device characterized by comprising a feed control device.