JPH025374Y2 - - Google Patents

Description

[Detailed explanation of the idea] The present invention relates to an automatic weight adding and removing type balance.

In general, a mechanism for selectively adding/removing multiple built-in weights involves attaching a weight adding/removing cam corresponding to each weight to a common shaft, engaging a weight adding/removing lever for each cam, and holding the weight while the shaft rotates once. All combinations of weight addition and subtraction can be selected. Therefore, for example, in an apparatus using four weights, there are ²⁴ =16 combinations of weight addition/subtraction, and the circumference of the cam must be divided into 16 to form the cam.
Furthermore, if the weight adding/removing mechanism is to be miniaturized, not only the precision of the cam's work but also the backlash of the mechanism for rotationally driving the cam become important issues.

The purpose of the present invention is to solve this problem and to provide an automatic weight adding/removing balance that operates accurately without having to keep the buck crash particularly low.

The characteristic part of the present invention is the control device for the step motor that rotationally drives the weight addition/removal cam. The cam is rotated to the reference position before the start of measurement by using the determination result and the output of the reference position detection device which detects whether the cam is at the reference position or not. To eliminate backlash in a drive mechanism of a cam for weight addition/removal by always making the direction of rotation of the cam to a predetermined position immediately before stopping in a constant direction during weight addition/removal operation during weight addition/removal operation.

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a block diagram of an embodiment of the present invention. A plate 3 for placing an object to be measured and a plurality of built-in weights 4 are suspended from a force point 2 placed at one end of the beam 1.
An electromagnetic force generating mechanism 15 that detects the imbalance of the beam 1 and generates a force to resist the load is disposed at the other end of the beam 1, sandwiching the fulcrum 5 of the beam 1. Multiple built-in weights 4
are engaged with their corresponding weight addition/removal levers 6, and each weight addition/removal lever 6 is engaged with its corresponding weight addition/removal cam 7, and each weight addition/removal cam 7 is coaxially connected to the camshaft 8. It is fixed and rotated by a step motor 9. Therefore, each built-in weight 4 is attached to and detached from the weight hook 10 according to the rotation angle of the step motor 9, and the camshaft 8
All combinations of weight addition and subtraction can be selected during one rotation of the weight. A reference position detection shutter 11 is disposed on the camshaft 8 and works together with a photo sensor 12 to detect the reference position of its rotation. Drive control of the step motor 9 is performed by a step motor drive circuit 14 in response to command signals from an arithmetic and control unit 13.

The driving control of the step motor 9, which is a feature of the present invention, is performed according to a program stored in the arithmetic and control unit 13, and its operation will be explained below with reference to a flowchart.

FIGS. 2 and 3 are flowcharts of the rotation of the camshaft 8 to the reference position before starting measurement when the power is turned on, and the rotation of the camshaft 8 to a predetermined position during the weight adding/removing operation, respectively.

FIG. 4 shows an explanatory diagram showing the positional relationship between the reference position detection shutter 11 and the photo sensor 12 arranged on the camshaft 8, and the flowcharts of FIGS. 2 and 3 will be explained based on this.

The reference position of the camshaft 8 is set to the position shown in FIG. 4A, with the reference position detection shutter 11 blocking light from the photo sensor 12. When the power is turned on, the reference position detection shutter 11 is activated as shown in FIG.
does not block the light from the photo sensor 12,
That is, for example, when the camshaft 8 is in the position shown in FIG. The shutter is stopped at the reference position shown in Figure 4 A, and the reference position detection shutter 1 is activated when the power is turned on.
1 blocks the light of the photo sensor 12,
Is the camshaft 8 in the reference position shown in Figure 4 A?
Alternatively, it is also possible that the camshaft 8 is in the position shown in FIG. At step A, a command signal is issued to the step motor drive circuit 14 to rotate it clockwise until the light is blocked, and the camshaft 8 is stopped at the reference position shown in FIG. 4A.

When a weight addition/removal command is generated in the measurement state and the weight is added/removed, if the commanded cam stop position is, for example, E in Figure 4, the command will move clockwise relative to the current cam position. The rotation of the cam is controlled according to the procedure shown below. That is, as shown in the flowchart of FIG. 3, when the camshaft 8 is in the position A of FIG. 4, a certain number of pulses is added to the number of pulses required to rotate it counterclockwise to the position E of FIG. A command signal is issued to the step motor drive circuit 14 to rotate the step motor drive circuit 14 counterclockwise by the number of pulses added above, and then stop at the position shown in FIG. 4 (D). It is stopped at the position shown in Fig. 4 (E). When the camshaft 8 is in the position shown in Figure 4, a command signal is issued to the step motor drive circuit 14 to rotate it clockwise to the position shown in Figure 4, and the camshaft 8 is stopped at the position shown in Figure 4, E. .

As explained above, according to the present invention, the camshaft rotates to the reference position before starting measurement when the power is turned on, and the camshaft rotates to a predetermined position during weight addition/removal operation when a weight addition/removal command is generated. Since the direction of rotation immediately before stopping is always constant, even if there is a bump in the camshaft drive system, the cam will always be accurately positioned and stopped. As a result, problems such as the built-in weight coming into contact with the weight addition/removal lever or the weight hook due to variations in the cam stop position, which are conventional, are eliminated.

At the same time, this also means that positioning can be performed with higher precision than before, without having to strictly suppress the bump crash of the camshaft drive system as in the past, or even if the adjustment of the weight adjustment mechanism is simpler than before. This is also advantageous in terms of manufacturing costs.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIGS. 2 and 3 are flowcharts of camshaft drive, and FIG. 4 is an explanatory diagram showing the positional relationship between the reference position detection shutter and the photo sensor. 1...Beam, 3...Dish, 4...Built-in weight, 7
...Cam for weight addition/removal, 8...Camshaft, 9...
...Step motor, 13... Arithmetic control unit, 14
...Step motor drive circuit.

Claims (1)

[Scope of Claim for Utility Model Registration] A built-in weight adjustment mechanism that controls the addition and removal of the internal weight according to the rotational position of the cam, a step motor that rotates the cam in both positive and negative directions, and a step motor that rotates the cam in both positive and negative directions, and a step motor that rotates the cam in both positive and negative directions; a reference position detection device for detecting whether or not the cam is present; In a balance having a control device for controlling the rotation of a step motor, the control device includes a determining means for determining whether or not a position based on a weight addition/removal command is on a predetermined direction side with respect to the current position of the cam. When the power is turned on, based on the output of the reference position detection device, if the cam is not at the reference position, the cam is rotated in the predetermined direction and stopped at the reference position, and when it is at the reference position, the cam is rotated. Once the weight is rotated by a predetermined amount in the opposite direction to the above predetermined direction, it is rotated in a predetermined direction and stopped at the reference position. Also, when a weight addition/removal command is issued in the measurement state, the position to be stopped is determined based on the above determination result. If the cam is on the side of the predetermined direction, the cam is rotated in the predetermined direction and stopped at the position based on the above command, and when the cam is on the opposite side to the predetermined direction, the cam is rotated in the opposite direction to the predetermined direction. The automatic weight is characterized in that a drive pulse is supplied to the step motor so that the weight moves and stops at a position based on the command by a predetermined amount, and then rotates in a predetermined direction and stops at the position based on the command. Adjustable balance.