JPS61294964A - Stepping motor driving circuit - Google Patents

Abstract

PURPOSE:To suppress excessive driving torque and to prevent the occurrence of noise at a low speed area by providing a speed control means, an energizing phase selecting means, an energizing current control means and an energizing means. CONSTITUTION:A driving speed control circuit 1 decides a driving speed and notifies a speed information which represents speed to be driven to an energizing phase selecting circuit 2 and an energizing current control circuit 3. The energizing phase selecting circuit 2 distributes a time to be energized on each phase of a stepping motor corresponding to the speed information and outputs a timing signal which indicates energizing or non-energizing to each of the stepping motor. On the other hand, the energizing current control circuit 3, in parallel with a series of speed control operation, performs the control of energizing current at each speed by the speed information. A stepping motor energizing circuit 4 energizes the phase of the stepping motor selected by the energizing phase selecting circuit 2 with current value set by the energizing current control circuit 3. Thereby, small current without generating the excessive torque is on at a low speed driving time.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a stepping motor drive circuit, and in particular,
The present invention relates to a stepping motor drive circuit used in a paper conveyance drive system that appropriately conveys original documents or recording paper over a wide speed range in a facsimile machine.

[Conventional technology]

In facsimile machines, with the demand for faster operation of the apparatus, it is necessary to operate the paper conveyance system for originals or recording paper at high speed. Conventionally, the stepping motor drive circuit used in the paper transport system of such high-speed facsimiles has been designed to provide constant current to each phase of the stepping motor, sharpening the current rise characteristics during phase switching, and achieving high speeds. So-called constant current control is widely used to obtain sufficient torque even in the range.

[Problem that the invention seeks to solve]

On the other hand, in facsimile machines that have an image information encoding function, the processing speed of the encoder and decoder generally changes greatly depending on the complexity of the image information, and the paper conveyance system is forced to change due to the change in processing speed. It is necessary to vary the driving speed widely from a low speed range to a high speed range. The processing speed of the primary recording device is
Generally, the amount of black pixels in the image information to be recorded changes, so it is necessary to change the driving speed of the paper conveyance system accordingly.

However, in general, stepping motors have the characteristic of generating large torque in the low speed range as well as in the high speed range, so the current flow value must be adjusted so that sufficient driving torque can be obtained in the high speed range to match the load torque of the paper conveyance system. When a stepping motor drive circuit that performs constant current control is used in a low speed range, the drive torque generated is excessive compared to the required torque, resulting in a large amount of noise.

In other words, when a conventional stepping motor drive circuit needs to be driven in a wide speed range from low to high speeds, such as in a high-speed facsimile,
The problem was that excessive torque was generated in the low speed range, producing large equipment noise.

It is an object of the present invention to provide a stepper motor drive circuit that generates sufficient drive torque in the high speed range and does not generate excessive drive torque in the low speed range to prevent device noise. The purpose is to provide.

[Means for solving problems]

In order to achieve the above object, a stepping motor drive circuit according to the present invention includes a speed control means that outputs speed information according to the required driving speed, and a stepper motor drive circuit that outputs speed information according to the required driving speed. energizing phase selection means for allocating phase energization time and outputting an energized phase switching signal; energizing current control means for outputting an energizing current value setting signal that changes in accordance with the speed information; The device is configured to include energizing means for energizing the next phase specified by the switching signal at a current value set by the energizing current value setting signal.

〔Example〕

Next, one embodiment of the present invention will be described based on the drawings.

FIG. 1 is a block diagram of the stepping motor drive circuit of this embodiment, which is composed of a drive speed control circuit 1, an energization phase selection circuit 2, an energization current control circuit 3, and a stepping motor energization circuit 4. be.

The driving speed control circuit determines the driving speed and notifies the energizing phase selection circuit 2 and the energizing current control circuit 3 of speed information representing the speed t to be driven. The energized phase selection circuit 2 allocates the time during which all phases of the stepping motor should be energized in accordance with the speed information, and outputs a timing signal instructing energization or de-energization to each phase of the stepping motor. On the other hand, in parallel with the series of speed control operations described above, the current flow control circuit 3 controls the current flow at each speed based on the speed information.

In other words, during high-speed driving, the energizing current is set to a large value to generate sufficient torque, and conversely, during low-speed driving, the energizing current is set to be small to avoid excessive torque. Outputs all signals. Such an energizing current control circuit 3 includes a ROM (read only memory) that is addressed by speed information and outputs current value information as data, and a ROM output, that is, converting current value information into voltage and controlling the energizing current. It is configured by a combination of D/A converters that output as a current value setting signal.

The stepping motor energizing circuit 4 energizes the phase of the stepping motor selected by the energizing phase selection circuit 2 at a current value set by the energizing current control circuit 3 . As a result, a large current necessary to generate a sufficiently large torque flows through each phase of the stepping motor during high-speed driving, and a small current that does not generate excessive torque flows during low-speed driving.

〔Effect of the invention〕

As explained above, the present invention allows a large current to flow during high-speed driving to generate sufficient torque, and performs current control to suppress the current to a small value so as not to generate excessive torque during low-speed driving. This has the effect of enabling a wide range of operation from low to high speed ranges without producing noise due to excessive torque.

[Brief explanation of drawings] FIG. 1 is a block diagram showing one embodiment of the present invention. 1... Drive speed control circuit 2... Energized phase selection circuit 3... Current flow control circuit 4...Stepping motor energizing circuit Patent applicant: NEC Corporation Agent Patent Attorney Inoro Jusai 1

Claims (1)

[Claims] a speed control means for outputting speed information in accordance with a required drive speed; an energization phase selection means for allocating energization time of each phase of the stepping motor in accordance with the speed information and outputting an energization phase switching signal; Current flow control means outputs a current flow value setting signal that changes according to information, and energizes the phase designated by the energization phase switching signal at the current value set by the current flow value setting signal. A stepping motor drive circuit comprising a current supply means.