JPH0876852A - Cam device - Google Patents

Abstract

PURPOSE: To provide an extremely inexpensive cam device simple in structure without removing a mechanical cam device and without using an expensive ball screw, etc. CONSTITUTION: This cam device contains a rotational angle controller 5 of a servo motor 2. The controller 5 consists of a position pattern Generator 51 which generates the relation between the rotational angle θ' of a mechanical cam 1 and a phase θ as a position pattern. This relation is secured when a desired displacement curve Y=f(θ) is projected on the displacement curve X=g (θ') of the cam 1, where a position command, i.e., the relation between the angular velocity ω and the time (t) is referred to as θ. The controller 5 also includes a position control loop which calculates a velocity command Nref against a servo driver 4 by using the rotational angle θ' obtained by inputting a phase command θ to the generator 51 as a position command and using the position signal corresponding to a detection signal of a pulse detection signal of a pulse generator 3 as a feedback signal respectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cam device for converting a rotational motion of a motor or the like into a periodic motion, and more particularly to a cam device using an existing mechanical cam to obtain an arbitrary displacement curve.

[0002]

2. Description of the Related Art Conventionally, a cam device has long been used as a means for converting the rotational movement of a main shaft driven by a motor into a periodic linear movement of a driven shaft. Is determined, the cyclic displacement curve is 1
I only get the kind. In order to obtain different displacement curves, it is necessary to make and replace cams having different shapes to realize the displacement curves, which requires a lot of setup time for manufacturing, replacement and adjustment. As a means to solve this, instead of a mechanical cam device, a driven shaft composed of a ball screw or the like is driven by a servo motor, and the servo is performed based on a command from a displacement curve storage unit that stores the position data of the displacement curve. An electric cam device is disclosed in which a driven shaft is displaced according to a desired displacement curve by drivingly controlling a motor (for example, Japanese Patent Application Laid-Open No. Hei 4-
37910, JP-A-5-49279).

[0003]

However, in the prior art, by simply replacing the position data in the displacement curve storage unit,
It has the advantage that it can instantly respond to different displacement curves. However, if the existing equipment already uses a mechanical cam device, it will be necessary to remove the mechanical cam device, purchase and install a driven shaft such as a ball screw, and rebuild the mechanical structure accompanying it, resulting in a large cost. There was a drawback that it cost. An object of the present invention is to provide a cam device which has a simple structure and is extremely inexpensive, without removing the mechanical cam device and without using an expensive ball screw or the like.

[0004]

In order to solve the above problems, the present invention provides a mechanical cam that can rotate, a servomotor that rotationally drives the mechanical cam, and a signal that corresponds to the amount of rotation of the servomotor. A pulse generator, a servo driver having a speed control loop for driving the servo motor, and an angle control device for controlling the rotation angle of the servo motor, wherein the angle control device has an angular velocity ω The phase command as a function of time t is θ, the rotation angle of the mechanical cam is θ ′, and the desired displacement curve is Y =
f (θ), where X = g (θ ′) is the displacement curve of the mechanical cam, the desired displacement curve Y = f (θ) is projected onto the displacement curve X = g (θ ′) of the mechanical cam. A position pattern generator that generates the relationship between the rotation angle θ ′ of the mechanical cam and the phase command θ as a position pattern, and the rotation obtained by inputting the phase command θ to the position pattern generator. The position control loop calculates the speed command N _ref for the servo driver by using the angle θ ′ as a position command and a position signal according to the detection signal of the pulse generator as a feedback signal.

[0005]

By the above means, the displacement curve of the mechanical cam X = g
A desired displacement curve Y = f (θ) is projected on (θ ′), and the relationship between the rotation angle θ ′ of the mechanical cam and the phase command θ is obtained. That is, g (θ ′) = f (θ) is set, and the phase command θ is output to the position pattern generation circuit that outputs the value obtained from the inverse function of g, θ ′ = g ⁻¹ (f (θ)), as the position pattern.
Is input, the rotation angle θ ′ of the mechanical cam is output from the position pattern generation circuit, and the speed command N _ref calculated from the output
Is input to the servo drive to drive the servo motor.
As a result, the mechanical cam driven by the servomotor achieves the desired displacement curve Y = f (θ). Therefore,
By setting data of an arbitrary displacement curve in the position pattern generation circuit, it is possible to realize a cam operation of an arbitrary displacement curve using one type of mechanical cam.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention.
In the figure, 1 is a mechanical cam having a predetermined displacement curve, 2
Is a servomotor that rotationally drives the mechanical cam 1, 3 is a pulse generator that detects the rotation angle of the servomotor 2, and 4 is a pulse generator.
Is a servo driver that drives the servo motor 2, and 5 is an angle control device that controls the rotation angle of the servo motor 2. 5
Reference numeral 1 is a position pattern generation circuit that generates a displacement position pattern at a rotation angle θ ′ of the mechanical cam 1 with respect to a phase command θ that is a function of the angular velocity ω and time t, and 52 is output from the position pattern generation circuit 51. An adder for feeding back the position command and the position signal from the pulse generator 3 via the counter 53, 54 an adder for feed-forwarding the position command output from the position pattern generation circuit 51 to the output of the adder 52, and 55 an addition The output of the instrument 54 is D /
It is a D / A converter that performs A conversion. Therefore, when the rotation angle θ ′ of the mechanical cam 1 is used as a position command, a position control loop is formed by the above configuration, and its output is input to the servo driver 4 as a speed command N _ref of the servo motor 2.

Here, the operation of the position pattern generating circuit 51 will be described. Now, it is assumed that the mechanical cam 1 has a displacement curve X = g (θ ′) as shown in FIG. However, θ'is the rotation angle of the mechanical cam. On the other hand, it is assumed that the mechanical cam 1 changes the displacement curve Y = f (θ) as shown in FIG. The phase command θ is ω for angular velocity and t for time.
Then, θ = ωt, so if ω is constant,
θ may be considered as time t. The relationship between the maximum displacement Y _{ma x} displacement curve to be changed as the maximum displacement X _max of the machine cam 1, and X _max ≧ Y _max. This is X _max <Y
_{This is because in} the range of _max , the desired displacement exceeds the displacement of the mechanical cam 1, so that the desired displacement cannot be realized by rotating the mechanical cam 1. FIG.
As shown in, each displacement point on the displacement curve Y = f (θ) for each phase (θ ₁ , θ ₂ , θ ₃ , θ ₄ , θ ₅ ...) of the displacement curve Y = f (θ) to be obtained ( a, b, c, d, e ...). Next, each displacement point (a, b, c, d, e ...) Is projected onto one side MN of the displacement curve X = g (θ ′) of the mechanical cam 1, and the mechanical cam displacement point (a ′, b) is projected. ', C', d ', e ...)
And the mechanical cam displacement points (a ', b', c ',
The rotation angle (θ of the mechanical cam 1 corresponding to d ′, e ...)
₁ ', θ ₂ ', θ ₃ ', θ ₄ ', θ ₅ '...).
Here, each phase (θ ₁ , θ ₂ , θ ₃ , θ ₄ , θ ₅ ...) and the rotation angle of the mechanical cam 1 (θ ₁ ′, θ ₂ ′, θ ₃ ′, θ
_The position pattern θ ′ = g ⁻¹ (f (θ)) is obtained as an inverse function of g in relation to ₄ ′, θ ₅ ′ ...).

Therefore, the position pattern θ '= g ^-1 (f
By inputting the phase command θ to the position pattern generation circuit 51 that generates (θ)), outputting the rotation angle θ ′ corresponding to the phase command θ, and forming a position control loop using the rotation angle θ ′ as the position command. When the servo motor 2 is rotated by the obtained speed command N _ref , the desired displacement curve Y = f (θ) can be obtained by the mechanical cam 1. As shown in FIG. 5, the actual operation of the mechanical cam 1 is such that when θ = 0 ° at first, the mechanical cam 1 has a displacement X = 0 and a rotation angle θ ′ = 0, and then θ = θ ₁ . , When the displacement X = a 'of the mechanical cam 1 and the rotation angle θ' = θ ' ₁ and θ = θ ₂ , the displacement X = b' of the mechanical cam 1 causes the rotation angle θ '= θ' ₂ and θ = θ ₃ , The rotation angle θ ′ = θ ′ at the displacement X = c ′ of the mechanical cam 1
₃ , when θ = θ ₄ , displacement X = d ′ of the mechanical cam 1 causes the mechanical cam to reverse, and when rotational angle θ ′ = θ ′ ₄ and θ = θ ₅ , displacement X = e ′ of mechanical cam 1 And the rotation angle θ '=
When θ ′ ₅ and θ = 360 °, the mechanical cam 1 is displaced X =
At 0, the rotation angle θ ′ = 0. The maximum displacement amount of the displacement curve to be changed as the maximum displacement X _max of mechanical cam 1 Y _{ma x}
And are equal, each phase (θ ₁ , θ ₂ , θ ₃ , θ ₄ , θ _{5 of the} displacement curve Y = f (θ) desired to be obtained over the entire circumference of the mechanical cam 1
...) for each displacement point on the displacement curve Y = f (θ) (a,
b, c, d, e ...) to project the mechanical cam 1
One rotation of can be one cycle of the displacement curve.
Thus, by setting an arbitrary displacement curve Y = f (θ) in the position pattern generating circuit 51, a desired displacement curve can be obtained without replacing the mechanical cam.
It is possible to instantly realize a cam operation with an arbitrary displacement curve by using various kinds of mechanical cams.

[0009]

As described above, according to the present invention, one type of mechanical cam can be used without replacing the mechanical cam by setting the data of an arbitrary displacement curve in the position pattern generating circuit. Since a cam operation that draws an arbitrary displacement curve can be realized, it is not necessary to remove the mechanical cam or install an expensive ball screw, and there is an effect that an extremely inexpensive cam device can be provided.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a displacement curve diagram of a mechanical cam according to an embodiment of the present invention.

FIG. 3 is a desired displacement curve diagram of an embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a procedure of projecting a desired displacement curve on a displacement curve of a mechanical cam according to an embodiment of the present invention.

FIG. 5 is an explanatory diagram showing the operation of the mechanical cam of the embodiment of the present invention.

[Explanation of symbols]

1 mechanical cam, 2 servo motor, 3 pulse generator, 4 servo driver, 5 angle control device, 51
Position pattern generation circuit, 52, 54 adder, 53 counter, 55 D / A converter

Claims (1)

[Claims] 1. A mechanical cam that can rotate, a servomotor that rotationally drives the mechanical cam, a pulse generator that generates a signal according to the amount of rotation of the servomotor, and a servomotor that has a speed control loop. In a cam device including a driving servo driver and an angle control device for controlling a rotation angle of the servo motor, the angle control device provides a phase command θ that is a function of an angular velocity ω and a time t, the mechanical cam. Θ'is the rotation angle of and the desired displacement curve is Y =
f (θ), where X = g (θ ′) is the displacement curve of the mechanical cam, the desired displacement curve Y = f (θ) is projected onto the displacement curve X = g (θ ′) of the mechanical cam. A position pattern generator that generates the relationship between the rotation angle θ ′ of the mechanical cam and the phase command θ as a position pattern, and the rotation obtained by inputting the phase command θ to the position pattern generator. A cam comprising a position control loop for calculating a speed command N _ref for the servo driver by using the angle θ ′ as a position command and a position signal corresponding to a detection signal of the pulse generator as a feedback signal. apparatus.