Detection signal processing circuit and detection signal processing apparatus for a rotation sensor

• US 7,345,468 B2
• Filed: 03/01/2005
• Issued: 03/18/2008
• Est. Priority Date: 03/02/2004
• Status: Expired due to Fees

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Okada, Hiroshi, Sugiki, Mikio, Makino, Yasuaki
• Primary Examiner(s): WHITTINGTON, KENNETH
• Application Number:
  US11/067,681
• Publication Number:
  US 20050194964A1
• Time in Patent Office: 1,113 Days
• Field of Search: 324/160, 324/163, 324/165, 324/166, 324/173, 324/174, 324/178, 324/179, 324/207.13, 324/207.15, 324/207.2, 324/207.21, 324/207.25, 735/143.9, 340/671, 340/672
• US Class Current: 324/165
• CPC Class Codes: G01P 13/045 with speed indication

Abstract

Detecting the rotational direction of a rotor is feasible by allowing a constant current source to supply a constant current flowing from an electric potential supply line to the earth in response to a turning-on action of a switch. Accordingly, detecting both the rotational speed and the rotational direction of the rotor is feasible by using three wiring cables of a power source line, an earth line, and a signal line outputting a pulse signal in accordance with the rotation of the gear. Using such a one-stage voltage adjustment enables the detection signal processing circuit to reduce electric power consumption compared with a system requiring a two-stage voltage adjustment.

Claims

1. A signal processing circuit disposed in a rotation sensor, the rotation sensor including two sensing elements disposed in a confronting relationship with a rotor to produce detection signals having different phases in accordance with rotation of said rotor, and detecting a rotational speed and a rotational direction of said rotor based on said detection signals, said detection signal processing circuit comprising:

pulse signal generating means for generating pulse signals in response to a change occurring in a level of the detection signal produced from at least one of said two sensing elements;

forward/reverse judging means for generating a judgment signal based on the pulse signals from the pulse signal generating means, the judgment signal showing whether the rotational direction of said rotor is a forward direction or a reverse direction; and

potential changing means comprising;

a path connecting a power source line to a predetermined power source and an earth line;

a constant current source generating a constant current, and being disposed in the path; and

a switch disposed in the path, and being controlled to be selectively switched between on/off states to connect or disconnect the constant current source and the earth line,

wherein the potential changing means changes an electric potential supplied to the signal processing circuit via the power source line on the basis of a voltage drop caused in response to the selectively switching between the on/off states of the switch so that the changed electric potential shows the rotational direction of the rotor, and controls the switch in accordance with said judgment signal of said forward/reverse judging means.

2. The signal processing circuit in accordance with claim 1, further comprising a constant voltage circuit to supply a constant voltage to each of said pulse signal generating means, said forward/reverse judging means, and said potential changing means.

3. The signal processing circuit in accordance with claim 2, wherein an input current of said constant voltage circuit is constant.

4. The signal processing circuit in accordance with claim 3, wherein said constant voltage circuit includes:

a constant voltage section producing a constant voltage based on a band gap;

a differential amplifier inputting the constant voltage produced from said constant voltage section and also inputting a control voltage; and

a control element having a control terminal receiving an output of said differential amplifier and input and output terminals connected between said power source line and the earth line.

5. The signal processing circuit in accordance with claim 1, wherein the power source line of the signal processing circuit is connected in series to a resistor disposed externally from the signal processing circuit, the resistor causing the voltage drop in response to the switch being controlled to be selectively switched to on state.

6. The signal processing circuit in accordance with claim 5, wherein the potential changing means is configured to control the switch to be selectively switched to the on state when the forward/reverse judging means generates the judgment signal showing the reverse direction of the rotor.

7. The signal processing circuit in accordance with claim 1, wherein the path connecting the switch and the earth line includes a resistor causing the voltage drop in response to the switch being controlled to be selectively switched to the on state.

8. A signal processing unit incorporated in a rotation sensor including a detection signal processing circuit and a rotational direction signal binarization circuit, wherein

said detection signal processing circuit includes two sensing elements disposed in a confronting relationship with a rotor to produce detection signals having different phases in accordance with rotation of said rotor and detects a rotational speed and a rotational direction of said rotor based on said detection signals, and

said rotational direction signal binarization circuit generates a binary signal representing the rotational direction of said rotor, wherein

said detection signal processing circuit comprises:

pulse signal generating means for generating a pulse signal in response to a change occurring in a level of the detection signal produced from at least one of said two sensing elements;

forward/reverse judging means for generating a judgment signal corresponding to the rotational direction of said rotor based on the detection signals of said two sensing elements; and

current path forming means for allowing a constant current to flow from a power source line to an earth via a resistor in response to said judgment signal of said forward/reverse judging means, and

said rotational direction signal binarization circuit detects said constant current flowing from said power source line to said earth based on a voltage change occurring in said power source line, and generates said binary signal representing the rotational direction of said rotor.

9. A signal processing unit incorporated in a rotation sensor including a detection signal processing circuit and a rotational direction signal binarization circuit, wherein

said detection signal processing circuit includes two sensing elements disposed in a confronting relationship with a rotor to produce detection signals having different phases in accordance with rotation of said rotor and detects a rotational speed and a rotational direction of said rotor based on said detection signals, and

said rotational direction signal binarization circuit generates a binary signal representing the rotational direction of said rotor, wherein

said detection signal processing circuit comprises:

pulse signal generating means for generating a pulse signal in response to a change occurring in a level of the detection signal produced from at least one of said two sensing elements;

forward/reverse judging means for generating a judgment signal corresponding to the rotational direction of said rotor based on the detection signals of said two sensing elements; and

current path forming means for allowing a constant current to flow from an electric potential supply line to an earth line response to said judgment signal of said forward/reverse judging means, and

said rotational direction signal binarization circuit is connected to a voltage source via a resistor, wherein a connecting point of said resistor and said rotational direction signal binarization circuit is connected to said electric potential supply line of said current path forming means, and

said rotational direction signal binarization circuit detects said constant current flowing from said electric potential supply line to said earth line based on a voltage drop occurring at said resistor, and generates said binary signal representing the rotational direction of said rotor.

10. A rotation sensor detecting at least a rotational direction of a rotor to be targeted, comprising:

first and second sensing elements sensing rotation of the rotor to output first and second signals indicative of the rotation, the first and second signals being different in phase from each other;

converting means for converting the first and second signals into corresponding pulse signals, respectively;

first determining means for determining whether or not the rotational direction of the rotor is a forward direction or a reverse direction based on the converted pulse signals;

changing means for changing an amount of power consumption in the rotation sensor so that a voltage on a power source line from a predetermined power source is chanced based on determined results of the first determining means; and

second determining means for determining whether or not the rotational direction of the rotor is the forward direction or the reverse direction based on the voltage of the power source line,

wherein the changing means comprises;

a path for connecting the power source line to an earth line;

a constant current source generating a constant current, the constant current source being disposed in the path;

a switch disposed in the path, the switch being switched between on/off states to selectively connect or disconnect the constant current source from ground; and

means for changing the voltage on the power source line on the basis of a voltage drop caused in response to the selectively switching between the on/off states of the switch so that the changed voltage shows the rotational direction of the rotor.

11. The rotation sensor of claim 10, further comprising a resistor disposed on the power source line to cause the voltage drop.

12. The rotation sensor of claim 11, wherein the changing means is configured to switch the switch to the on state when the first determining means determines the rotational direction of the rotor is the reverse direction.

13. The rotation sensor of claim 11, wherein the second determining means has an input electrically connected to the power source line to receive the voltage drop from a voltage of the predetermined power source.

14. The rotation sensor of claim 10, further comprising a resistor disposed in the path to cause the voltage drop.

15. The rotation sensor of claim 10, wherein the voltage drop is a two-level drop depending on which direction the rotor rotates.

16. The rotation sensor of claim 15, wherein the two-level drop includes a first voltage drop from a voltage of the predetermined power source and a second voltage drop following the first voltage drop, the first voltage drop occurring when the first determining means determines that the rotational direction of the rotor is the forward direction and the second voltage drop occurring when the first determining means determines that the rotational direction of the rotor is the reverse direction.