Reluctance type linear position detection device

A linear position detection device including a coil section and a rod section being disposed in such a manner that it is capable of relative linear displacement with respect to said coil section, said coil section having at least two primary coils and secondary coil means corresponding to said primary coils, respective primary coils being excited by primary AC signals which are out of phase with one another so as to obtain, on the secondary coil means, an output signal which is produced by phase-shifting one of said primary AC signals in accordance with the relative linear position of said rod section, wherein said rod section is generally of a bar configuration and said rod section comprises:

• a plurality of conductive substance portions provided repeatedly at a predetermined interval in the direction of said relative linear displacement, said respective conductive substance portions being provided in such a manner that an eddy current path relative to flux produced by said coil section will be formed and being made of substance which is weak magnetic or non-magnetic and relatively conductive as compared with substance of the remaining portion of said rod section,
• and wherein the amount of the phase-shift corresponds to 360 degrees electrical angle with respect to an amount of displacement corresponding to one cycle of sequence of said conductive substance portions in said rod section, and a base portion of said rod section is coated with resin over the entire periphery thereof and a predetermined conductive substance is deposited on said coated resin over the entire periphery of said rod and said conductive substance is removed thereafter in a predetermined pattern thereby to leave conductive substance of a predetermined pattern which constitutes said conductive substance portions.

A linear position detection apparatus comprising a plurality of linear position detection devices each having a coil section and a rod section being disposed in such a manner that it is capable of relative linear displacement with respect to said coil section, said coil section having at least two primary coils and secondary coil means corresponding to said primary coils, respective primary coils being excited by primary AC signals which are out of phase with one another so as to obtain, on the secondary coil means side, an output signal which is produced by phase-shifting one of said primary AC signals in accordance with the relative linear position of said rod section,

• said rod section of said respective detection devices comprising a plurality of conductive substance portions provided at a predetermined interval in the direction of said relative linear displacement, said respective conductive substance portions being provided in such a manner that an eddy current path relative to flux produced by said coil section will be formed and being made of substance which is weak magnetic or non-magnetic and relatively conductive as compared with substance of other portion of said rod section, and
• said rod section of said respective detection devices being made of a common base portion and sequence of said conductive substance portions corresponding to each of said rod section being provided independently on said common base portion and an interval of repetition of said conductive substance portions being different between the respective rod sections.

A linear position detection device including a coil section and a rod section being disposed in such a manner that it is capable of relative linear displacement with respect to said coil section, said coil section having at least two primary coils and secondary coil means corresponding to said primary coils, respective primary coils being excited by primary AC signals which are out of phase with one another so as to obtain, on the secondary coil means side, the output signal which is produced by phase-shifting one of said primary AC signals in accordance with the relative linear position of said rod section wherein said rod section is generally of an elongated plate-like configuration and said rod section comprises:

• a magnetic substance portion provided in predetermined part of the rod section thereby changing the reluctance of a magnetic circuit passing through said coil section in accordance with said relative linear displacement;
• and
• a conductive substance portion provided in part of the rod section where the reluctance is caused to increase relatively in such a manner that an eddy current path will be formed relative to flux and made of substance which is relatively weak magnetic or non-magnetic and relatively conductive as compared with said magnetic substance,
• a plurality of said magnetic substance portions and said conductive substance portions being provided alternately,
• such that the amount of the phase-shift corresponds to 360 degrees electrical angle with respect to an amount of displacement corresponding to one cycle of the alternation of said magnetic and conductive substance portions in said rod section.

A linear position detection device including a coil section and a rod section being disposed in such a manner that it is capable of relative linear displacement with respect to said coil section, said coil section having at least two primary coils and secondary coil means corresponding to said primary coils, respective primary coils being excited by primary AC signals which are out of phase with one another so as to obtain, on the secondary coil means side, the output signal which is produced by phase-shifting one of said primary AC signals in accordance with the relative linear position of said rod section, said rod section being generally of an elongated plate-like configuration and said rod section comprising:

• a plurality of conductive substance portions provided repeatedly at a predetermined interval in the direction of said relative linear displacement, said respective conductive substance portions being provided in such a manner that an eddy current path relative to flux produced by said coil section will be formed and being made of substance which is weak magnetic or non-magnetic and relatively conductive as compared with substance of other portion of said rod section,
• such that the amount of the phase-shift corresponds to 360 degrees electrical angle with respect to an amount of displacement corresponding to one cycle of sequence of said conductive substance portions in said rod section, and a base portion of said rod section is coated with resin over the entire periphery thereof and a predetermined conductive substance is deposited on said coated resin over the entire periphery of said rod and said conductive substance is removed thereafter in a predetermined pattern thereby to leave conductive substance of a predetermined pattern which constitutes said conductive substance portions.