JPS5944178B2 - cam grinding device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for grinding a cam of a workpiece such as a camshaft, and its purpose is to keep the relative circumferential velocity of the workpiece to the grindstone at approximately constant 0 degrees during grinding. , to obtain a highly accurate cam profile.

Generally, when grinding a cam such as a camshaft, a master cam with a shape that matches the cam profile is pressed against the follower roller, and a rocking table is swung according to the pro5 pool of the master cam. In this method, a camshaft held between a main shaft and a tailstock is rotated at a constant speed in synchronization with a master cam, and the cam of the camshaft is ground using a grindstone.

'0 However, as shown in Fig. 1, in a cam C that has a top part T, a base circular part B, and a side part S connecting these two parts, while rotating at a constant rotational speed as described above, the swing center When grinding is performed with the grindstone C by swinging around O, the relative circumferential speed of the cam surface with respect to the grindstone G (hereinafter referred to as the cam surface circumferential speed) is constant in the top portion T and the arc portion of the base interior B. Precise machining is performed, but since the grinding point P moves when the side portion S is ground, the cam surface peripheral speed increases rapidly.

This state is shown in Fig. 210, and as is clear from this, the cam surface peripheral speed near the rotation angle of 120 degrees and 240 degrees, which is the side portion S of the cam C, is higher than the peripheral speed of other parts. It's getting noticeably bigger. As can be seen from the cam profile 15 error curve in Fig. 2, in the area where the grinding point P moved rapidly in this way, there was an inconvenience that the cutting depth was insufficient or excessive, resulting in a cam profile error, and thus the finished surface accuracy deteriorated. . In order to solve these conventional problems, the present invention sequentially measures the lift amount of the master cam at a measurement position that is a unit rotation angle ahead of the contact position with the follower roller, and adjusts the workpiece according to the measurement output. It is characterized in that the rotational speed is controlled to keep the cam surface circumferential speed almost constant.

Embodiments of the present invention will be described below with reference to FIGS. 3 to 6.

First, 1 is a sliding table of the cam grinding device, 2 is a headstock fixed on this sliding table 1, and 3 is a rocking table supported on the sliding table 1 by support shafts 4 and 5 so as to be swingable. It is.

A main shaft 6 is rotatably supported on the rocking table 3, and a plurality of master cams 7 are fitted in series in the center of the main shaft 6. Further, a center is fitted to the tip of the main spindle 6, and a workpiece W such as a camshaft having a cam C is held between this center and the center of a tailstock 8 fixed on the rocking table 3. There is. A universal joint 9 is provided at the rear end of the main shaft 6, and a universal joint 11 is connected to this universal joint 9 via a spline shaft 10, and this universal joint 11 is rotatably supported on the sliding table 1. A transmission shaft 12 is connected thereto. The transmission shaft 12 is rotatably driven by a rotary drive device 15 consisting of a servo motor 13 and a reduction gear device 14. Further, in FIG. 3, 16 is a unit rotation angle detection device that sends out a pulse signal every time the main shaft 6 rotates by a unit rotation angle θ.
A slit disk 17 is fixed to the rear end of the main shaft 6 and has a large number of slits S carved in the circumferential direction at intervals of a unit rotation angle θ, as shown in FIG. A light source 18 and a disk 17 provided opposite the light source 18.
The photoelectric converter 19, such as a phototransistor, responds to a light source 18 via a slit S according to the rotation of the phototransistor. Furthermore, a swinging arm 20 is attached to the lower end of the swinging table 3, and a tension spring 21 is stretched between the swinging arm 20 and the headstock 2. The spring 21 constantly urges the rocking table 3 to rotate counterclockwise in FIG. has been done. A cylinder device 22 is mounted on the headstock 2, and a piston rod 23 of this cylinder device 22 is mounted on the headstock 2.
When releasing the contact state between the master cam 7 and the follower roller 31, the tip of the swinging arm 20 is pressed, and the swinging table 3 is rocked clockwise against the tensile force of the tension spring 21. The master cam 7 is separated from the follower roller 31. Further, at the lower end of the rocking table 3, on the opposite side of the rocking arm 20, a support stand 25 is mounted so as to be slidable in the axial direction of the main shaft 6. A lift amount measuring device 26 such as a differential transformer to be measured is installed. As shown in FIG. 4, the measuring stylus 27 of the measuring device 26 is at a measuring position MP which is in advance of the contact position CP between the master cam 7 and the follower roller 31 by the unit rotation angle θ when the main shaft 6 rotates, as shown in FIG. It is in contact with master cam 7. Furthermore, Mastercam 7
As the probe rotates, the probe 27 moves forward (toward the right in Fig. 4).
When the displacement occurs, the measurement device 26 outputs a measurement output voltage that gradually increases. The headstock 2
A fluoro roller support 30 is supported on the left side of the main shaft 6 by dovetail fitting so as to be slidable in the axial direction of the main shaft 6, and the aforementioned fluoro roller 31 is rotatably mounted on this support 30, as shown in FIG. As shown, it is in contact with the master cam 7 adjacent to the probe 2r. At the lower end of the support 30 is a rack 3.
2, and a gear 33 rotatably mounted on the headstock 2 is meshed with the rack 32 via an idler gear 34. A star gear 3 is provided at the end of the shaft that supports the gear 33.
5 is fixed, and this gear 35 rotates by engaging with a number of dogs 37 mounted on a dog bar 36 fixed on a base B on which the slide table 1 is slidably mounted. There is.
A holding member 38 is also fixed to the lower end of the support base 30, and a fitting groove 39 formed at the tip of the support base 38 allows the support base 25 to restrict relative movement in the axial direction of the main shaft 6 and to prevent rocking. They are fitted so that they can slide within the fitting groove 39 as the moving table 3 swings. In FIG. 6, reference numeral 46 denotes a pulse wave shaping circuit connected to the photoelectric converter 19, which generates pulses of the photoelectric converter 19 in response to the light source 18 at every unit rotation angle θ as the slit disk 17 rotates. It shapes the signal into a rectangular pulse waveform. Next, the storage device 45 that stores the output from the lift amount measuring device 26 after a minute time has elapsed since the preceding pulse signal was sent from the unit rotation angle detecting device 16 will be explained. First, the pulse wave shaping circuit 46 is a one-shot circuit 4 that sends out a pulse signal that rises immediately after the shaped pulse signal falls.
7 is connected. This one-shot circuit 47
The input terminal of this gate circuit 48 is connected to the output terminal of the lift measuring device 26, and the capacitor C1 is connected between the output terminal and ground. . Yotsute capacitor C
1 stores the output from the lift amount detection device 26 after a short time period has elapsed since the pulse signal was sent. Next, according to the rotation of the main shaft 6, the unit rotation angle detection device 16
The arithmetic device 50 that calculates the difference between the output from the lift amount measuring device 26 at this time and the output stored in the storage device 45 based on the pulse signal sent out after the subsequent pulse signal will be explained.

A negative input terminal of a differential amplifier 51 is connected to the output terminal of the gate circuit 48, and a positive input terminal of the differential amplifier 51 is connected to an output terminal of the lift amount measuring device 26. The output terminal of the differential amplifier 51 is connected to the input terminal of a second gate circuit 52, and the gate terminal of this gate circuit 52 is connected to the pulse waveform shaping circuit 46. A rotational speed control device 60 that controls the rotational speed of the servo motor 13 of the rotational drive device 15 based on the output from the arithmetic device 50 will be described. First, an input terminal of a voltage follower operational amplifier 61 is connected to the output terminal of the gate circuit 52, and a capacitor C2 is connected between this input terminal and ground. Reference numeral 62 denotes a positive/negative determination circuit for determining whether the voltage output from the operational amplifier 61 is positive or negative, and is connected to the output terminal of the operational amplifier 61.

A positive judgment output terminal 62a of this positive/negative judgment circuit 62 is connected to a gate terminal 63a of a field effect transistor 63.
The negative judgment output terminal 62b is connected to the field effect transistor 64.
is connected to the gate terminal 64a of. Source terminals 63b and 64b of these transistors 63 and 64 are connected to the output terminal of the operational amplifier 61 described above. Furthermore, the drain terminal 63c of the transistor 63 is connected to the servo motor 1.
The drain terminal 64c of the transistor 64 is connected to the input side of the drive circuit 66 via an analog inverter 65. Next, the operation of the above configuration will be explained.

First, when machining the workpiece W, in order to match the grindstone G and the required cam C, the piston rod 23 of the cylinder device 22 is
When the sliding table 1 is moved to the left in FIG. 1 with the rocking table 3 rotated clockwise due to the lowering of the star gear 3
5 engages with the dog 37 on the base B and rotates. Due to the rotation of this star gear 35, the fluoro roller support 30
is slid, and the predetermined master cam 7 and follower roller 31 are positioned at corresponding positions as shown in FIG. Further, as the support body 30 slides, the support base 25 slides on the rocking base 3 while being held by the holding member 38, and the lift amount measuring device 26 also has a master cam whose measuring element 27 corresponds to the follower roller 31. 7, as shown in FIG. Subsequently, when a processing start command is issued, the piston dot 23 of the cylinder device 22 rises, and the rocking table 3 pivots counterclockwise around the support shafts 4 and 5 by the tensile force of the tension spring 21. Then, the master cam 7 comes into contact with the follower roller 31. When the servo motor 13 is rotated and driven in this state, this rotation is decelerated by the gear reduction device 14, further transmitted to the main shaft 6 via the transmission shaft 12 and the universal joints 11 and 9, and supported at the end of the main shaft together with the master cam 7. The workpiece W rotates. In this way, by the rotation of the master cam 7, the rocking table 3 and thus the workpiece W are swung according to the profile of the master cam 7, and the distance between the axis of the grindstone G and the axis of the workpiece W changes. As a result, a cam C matching the profile of the master cam 7 is ground on the workpiece W. When grinding this cam C, the operation of controlling the rotational speed of the main shaft 6 by the servo motor 13 will be explained below with reference to FIG. 6. First, the case where the contact point of the master cam 7 with respect to the follower roller 31 moves from the top portion T of the master cam to the inside B of the base will also be described. Now, when the main shaft 6 rotates by the unit rotation angle θ and the cam portion P1 of the master cam 7 contacts the follower roller 31, the lift amount measuring device 26 is attached to the cam portion P2 of the master cam 7.
Since the measuring head 27 of is displaced in the forward direction while making contact,
A measurement output voltage corresponding to the displacement of the probe 27 is generated from the measurement device 26 and applied to the positive input terminal of the differential amplifier 51 . On the other hand, since the measured output voltage charged in the capacitor C1 when the cam portion P1 of the master cam 7 contacts the probe 27 is applied to the negative input terminal of the differential amplifier 51, the difference between these two measured output voltages is Calculated by the differential amplifier 51, an output voltage 0E corresponding to the difference in cam lift amount between the cam portions Pl and P2 of the master cam 7 is output from the output terminal of the differential amplifier 51, and is applied to the gate circuit 52. Ru. Further, when the cam portion P1 comes into contact with the follower roller 31, the photoelectric converter 19 responds to the light source 18 through the slit S of the slit disk 17 to generate a detection pulse signal of the unit rotation angle θ. The pulse waveform shaping circuit 46 shapes the pulse waveform into a rectangular pulse waveform, and the pulse waveform is applied to the gate circuit 52 .

As a result, the gate of the gate circuit 52 opens, whereby the output voltage 0E is charged and stored in the capacitor C2. The output voltage stored in the capacitor C2 is applied to the voltage follower operational amplifier 61, and the output voltage corresponding to the output voltage 0E output from the output terminal of the operational amplifier 61 is determined by the positive/negative determination circuit 62. It is determined to be positive, and a positive determination signal is sent from the positive determination output terminal 62a and applied to the gate terminal 63a of the transistor 63. Thus, based on this positive determination signal, the source terminal 6 of the transistor 63
3b and the drain terminal 63c are allowed to conduct with each other.
An output voltage from an operational amplifier 61 is applied to the input side of the operational amplifier 61. As a result, the rotational speed of the servo motor 13 is
The gourd main shaft 6 is decelerated according to the difference in cam lift amount between Pl and P2.
The cam surface is rotated at a reduced speed so that the peripheral speed of the cam surface does not change. On the other hand, the pulse signal sent from the pulse waveform shaping circuit 46 is also guided to the gate terminal of the gate circuit 48 after a minute time through the one-shot circuit 47. As a result, the gate of the gate circuit 48 is opened, and the cam part from the measurement position 26 is guided to the gate terminal of the gate circuit 48. The capacitor C1 is charged in accordance with the measured output voltage corresponding to the cam lift amount of P2.

Thereafter, when the main shaft 6 and the master cam 7 further rotate by the unit rotation angle θ and the cam portion P2 of the master cam 7 contacts the follower roller 31, the probe 27 of the measuring device 26 contacts the cam portion P3 of the master cam 7 and rotates in the forward direction. Because of the displacement, the measured output voltage from the measuring device 26 is applied to the positive input terminal of the differential amplifier 51 in the same manner as described above.

As a result, the difference between this measured output voltage and the measured output voltage charged in the capacitor C1 is calculated by the differential amplifier 51, and the cam portions P2 and P3 of the master cam 7 are calculated in the same manner as described above.
An output voltage corresponding to the difference in cam lift amount between the two is output from the output terminal of the differential amplifier 51. This output voltage is determined by the gate circuit 5 based on a pulse signal emitted from the transformer 19 as the slit disk 17 rotates at a unit rotation angle θ.
It is output from the output terminal of C2 and charged to the capacitor C2. Then, a voltage corresponding to the charging voltage level of the capacitor C2 is outputted from the output terminal of the voltage follower operational amplifier 61, and the voltage corresponding to the charging voltage level of the capacitor C2 is outputted to the servo motor 13 through the conduction between the source terminal 63b and the drain terminal 63c of the transistor 63. is applied to the input side of the drive circuit 66, thereby reducing the rotational speed of the servo motor 13. In this way, the main shaft 6 and the master cam 7 are rotated at a unit rotation angle θ.
The rotation speed is sequentially controlled by the servo motor 13 according to the change in the cam lift amount due to the rotation of the master cam 7.
The cam C of the workpiece W rotates while the cam surface peripheral speed is maintained at a substantially desired constant value.

When the main shaft 6 further rotates and the base interior B of the master cam 7 contacts the follower roller 31, the difference in lift amount of the master cam 7 between the contact position CP and the measurement position MP is zero, so the servo motor 13 The rotation speed of is not changed.

When the cam part of the master cam 7 extending from the base interior B to the top part T contacts the guide roller 31, the probe 27 of the lift amount measuring device 26 is displaced in the backward direction, so that the unit rotation angle of the master cam 7 is As θ rotates, the output terminal of the measuring device 26 outputs a measurement output voltage that gradually decreases.

Therefore, the output voltage outputted from the output terminal of the voltage follower operational amplifier 61 through the operation of the differential amplifier 51 and the gate circuit 52 is determined to be negative by the positive/negative determination circuit 62. As a result, the negative judgment output terminal 62b of this judgment circuit 62
A negative determination signal is sent from the transistor 64 and applied to the gate terminal 64a of the transistor 64. As a result, transistor 6
4, the output voltage signal from the operational amplifier 61 is positively inverted by the analog inverter 65 and supplied to the human power side of the drive circuit 66, and the rotational speed of the servo motor 13 is increased. is controlled to decelerate. As described above, the present invention has a configuration in which the lift amount of the master cam is measured at a position preceding the contact point between the follower roller and the master cam by a unit angle, and the rotation speed is controlled by determining the rate of change in the lift amount, which will be described later. Therefore, it has an excellent effect of being able to accurately control the rotational speed of the main shaft at the point where the master cam and the follower roller come into contact without being affected by the response delay of the control system or the followability of the servo motor.

Further, the present invention is configured to calculate and obtain the rate of change in the lift amount of the master cam from the difference between the output from the lift amount measuring device and the lift amount measurement value stored in the storage device before the unit rotation angle. It is possible to accurately detect the point where the surface circumference speed suddenly increases, and by controlling the rotational speed of the spindle based on this calculation result, it is possible to machine the workpiece cam into a highly accurate profile. There are advantages.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the correspondence relationship between the cam and the grindstone, FIG. 2 is a diagram showing the cam surface peripheral speed and cam profile error in conventional cam grinding, and FIG. 3 is a diagram showing the cam according to the embodiment of the present invention. A front view of the grinding device, FIG. 4 is a cross-sectional view taken along the line - in FIG. 3, FIG. 5 is a partial plan view taken along arrow V in FIG. 4, and FIG. It is a circuit diagram. 1... Sliding base, 2... Headstock, 3...
...Rocking table, 6...Main shaft, 7...
Master cam, 15...Rotary drive device, 16...
...Unit rotation angle detection device, 26...Lift amount measuring device, 45...Storage device, 50...
... Arithmetic device, 60 ... Rotation speed control device,
C...Cam, CP...Contact position, MP
...Measurement position, W...Workpiece.

Claims (1)

[Claims] 1 A slider is pivotably supported on the slider, a main shaft is rotatably supported on the slider, a rotary drive device is connected to the main shaft, and a master cam fitted on the main shaft is mounted. In a cam grinding device that is brought into pressure contact with a follower roller and swings the rocking table according to the profile of the master cam as the main shaft rotates to grind a cam of a workpiece attached to the main shaft,
a unit rotation angle detection device that sends out a pulse signal every time the main shaft rotates by a unit rotation angle; a lift amount measuring device that measures the lift amount of the master cam at a measurement position that precedes by When a subsequent pulse signal is sent out from the unit rotation angle detection device in accordance with the rotation of a calculation device that calculates a rate of change in the lift amount of the master cam; and a rotation speed that controls the rotation speed of the rotary drive device so that the circumferential speed of the cam surface is approximately constant based on the output from the calculation device. A cam grinding device characterized by comprising a control device.