Stepping motor type indicator having a pole tooth with reduced end area

• US 6,211,585 B1
• Filed: 04/05/1999
• Issued: 04/03/2001
• Est. Priority Date: 04/28/1998
• Status: Expired due to Term

• Current Assignee: Nippon Seiki Company Limited
• Original Assignee: Nippon Seiki Company Limited
• Inventors: Matsuda, Hiroyuki, Sato, Hitoshi, Iwahashi, Masaru, Jinushi, Koichi, Tsurumaki, Keiji, Sato, Koichi, Numaya, Hiroyasu
• Primary Examiner(s): Ramirez, Nestor
• Assistant Examiner(s): Perez, Guillermo
• Application Number:
  US09/285,722
• Time in Patent Office: 729 Days
• Field of Search: 310/49 R, 310/261, 310/263, 310/254, 310/257, 310/258, 310/259, 324/154 R, 324/146
• US Class Current: 310/49.55
• CPC Class Codes: G01D 7/00 Indicating measured values
• CPC Class Codes: G01R 7/06 moving-iron type
• CPC Class Codes: H02K 37/14 with magnets rotating within the armatures

Abstract

A stepping motor type indicator provided with unambiguous stable points having a holding force in a non-excited condition sufficient to suppress undesirable movements of a pointer. The stepping motor type indicator includes a stepping motor (2) having a rotor (28) with an output shaft (27) and stators (A, B). Yokes (23, 26) have a plurality of pole teeth (232, 233, 262, 263) extending toward curved outer surfaces of the rotor. The pole ends of a specific pole tooth (232a) chosen from one of the plurality of pole teeth is made to have a pole end area different than that of the remaining pole teeth. This structure produces unambiguous stable points (“a”-“l”) and produces strong holding forces so that an attractive force exerted by the stable point (“a”) on the pointer (4) toward stopper pin (7) is increased to positively suppress undesirable movements of pointer (4).

Claims

1. A stepping motor type indicator comprising a stepping motor which is constructed of a rotor formed of permanent magnets and having an output shaft, and first and second stators individually having yokes, from which a plurality of pole teeth extend toward a curved outer surface of the rotor, and exciting coils for magnetizing the yokes, in which said first and second stators are concentrically stacked and said rotor is driven to rotate in accordance with a measurement value;

a driver which supplies driving signals to the exciting coils of said individual stators to cause the rotor to rotate in accordance with the measurement value;

a pointer which is connected to the output shaft of said stepping motor and indicates the measurement value on a dial plate; and

a rotor stopper for stopping said pointer at a specified stopping position on the dial plate, wherein the stopping position of said pointer determined by said rotor stopper is set at a point closer to a stable point which is located on a decreasing side of dial reading of said pointer than an approximately middle point between two adjacent stable points arbitrarily selected from a plurality of stable points of the rotor which are formed along the turning direction of said pointer due to magnetic forces exerted between the rotor and the yokes in a non-excited condition of the exciting coils, the pole end area of a specific pole tooth chosen from said multiple pole teeth facing the rotor is made different from the pole end areas of the other pole teeth facing the rotor so that a relative difference is created between the pole end areas of the pole teeth of said first stator facing the rotor and those of the pole teeth of said second stator, and the root-mean-square value of the driving signal fed into the exciting coil of said first stator whose pole teeth have smaller pole end areas facing the rotor is made higher than the root-mean-square value of the driving signal fed into the exciting coil of said second stator whole pole teeth have larger pole end areas facing the rotor.

2. A stepping motor type indicator according to claim 1, wherein the pole end area of only one specific pole tooth is made different from the pole end areas of the other pole teeth.

3. A stepping motor type indicator according to claim 2, wherein an angular position taken by said pointer when said driver outputs the driving signals corresponding to an electrical angle of 0°

and said stable point in the non-excited condition are matched exactly or approximately with each other.

4. A stepping motor type indicator according to claim 1, wherein an angular position taken by said pointer when said driver outputs the driving signals corresponding to an electrical angle of 0°

and said stable point in the non-excited condition are matched exactly or approximately with each other.

5. A stepping motor type indicator comprising a stepping motor which is constructed of a rotor formed of permanent magnets and having an output shaft, and first and second stators individually having yokes, from which a plurality of pole teeth extend toward a curved outer surface of the rotor, and exciting coils for magnetizing the yokes, in which said first and second stators are concentrically stacked and said rotor is driven to rotate in accordance with a measurement value;

a driver which supplies driving signals whose output waveforms have a phase difference to the exciting coils of said individual stators to cause the rotor to rotate in accordance with the measurement value;

a pointer which is connected to the output shaft of said stepping motor and indicates the measurement value on a dial plate; and

a rotor stopper for stopping said pointer at a specified stopping position on the dial plate, wherein the stopping position of said pointer determined by said rotor stopper is set at a point closer to a stable point which is located on a decreasing side of dial reading of said pointer than an approximately middle point between two adjacent stable points arbitrarily selected from a plurality of stable points of the rotor which are formed along the turning direction of said pointer due to magnetic forces exerted between the rotor and the yokes in a non-excited condition of the exciting coils, the pole end area of a specific pole tooth chosen from said multiple pole teeth facing the rotor is made different from the pole end areas of the other pole teeth facing the rotor to increase an attractive force at the stable points, and an angular position taken by the said pointer when said driver outputs the driving signals corresponding to an electrical angle of 0° and

said stable point in the non-excited condition are matched exactly or approximately with each other.