JPS6145450Y2 - - Google Patents

Description

[Detailed description of the invention] This invention is an improvement of an electromagnetic pickup that makes it possible to adjust the delay time of the detection output signal by adding a closed circuit between a resistor and a coil, or a ring made of a conductor with resistance. It is related to.

Electromagnetic pickups have conventionally been used as various timing detection means, such as injection timing checkers for diesel engines. Generally, the structure of this electromagnetic pickup is such that a magnetic core made of a magnetic material with a magnet fixed to one end is fitted into the hollow part of a hollow cylindrical bobbin, and a detection coil having an output terminal is wound around the outer circumference of the bobbin. The magnetic material that forms the magnetic core is
Materials such as ferrite through which eddy currents do not flow, or materials such as ordinary iron and permalloy that do not have measures to prevent eddy currents are used. If ferrite or the like is used as the magnetic core material, the core will become brittle, so great care must be taken when using it for industrial purposes, but the detection delay time of the electromagnetic pickup output signal is almost negligible. It can be done. On the other hand, iron, permalloy, etc. are durable and are commonly used as magnetic core materials, but they have the disadvantage of increasing detection delay time. Moreover, such a detection delay time has a unique value for each electromagnetic pickup, and it is difficult to make it uniform in manufacturing. Therefore, when an electromagnetic pickup is used as a timing detection means, it is necessary to correct the detection device according to the detection delay time of each electromagnetic pickup, which is inconvenient because the electromagnetic pickup parts are not compatible.

Furthermore, if a large number of electromagnetic pickups having the same detection delay time are to be obtained, the only way is to select those with the same characteristics from a larger number of manufactured electromagnetic pickups, which is uneconomical.

The present invention was devised in view of the above-mentioned technical problems, and its purpose is to add the above-mentioned to a conventional electromagnetic pickup in which a detection coil having an output terminal is wound around a magnetic core formed of a magnetic material. A detection system in which a resistance circuit that closes the magnetic core by going around the magnetic core at least once is provided in the vicinity of the detection coil, and the detection delay time of the electromagnetic pickup output signal can be freely adjusted by changing the number of circuits and the resistance value. An object of the present invention is to provide an electromagnetic pickup with a delay time adjustment circuit.

Embodiments of the electromagnetic pickup according to the present invention will be described below with reference to the drawings.

FIG. 1 is a side sectional view of an electromagnetic pickup according to an embodiment. To explain the figure, 1 is a hollow cylindrical bobbin, and a coil winding portion 2 is provided on the outer periphery of the bobbin.
There are two locations. In the hollow part of bobbin 1,
A magnetic core 3 with a magnet 2 fixed to one end is fitted. Some magnetic cores are made of metal magnetic materials such as iron and permalloy. A detection coil 4 is wound around one coil winding portion of the bobbin 1, and both ends of the detection coil 4 are drawn out as output terminals 5. A delay time adjustment coil 6 is wound around the other coil winding portion of the bobbin 1 provided near the detection coil 4, and a delay time adjustment resistor 7 is connected to the output terminal of this coil 6. is connected.

Next, the operation of the electromagnetic pickup constructed as described above will be explained.

The electromagnetic pickup detects the input signal and picks up the magnetic core 3.
When a time-varying magnetic flux flows inside the coil 6
A circuit current whose phase is delayed from that of the input signal flows through the detection delay time adjustment circuit formed by the resistor 7 and the input signal.
Then, an induced voltage due to mutual induction is output to the output terminal 5 of the detection coil 4 coupled to the coil 6 through mutual inductance, but this output becomes a signal with an increased delay time compared to the original signal. In other words, the coil 6 and resistor 7 of the detection delay time adjustment circuit
By adjusting the delay time of the circuit current flowing between the two, the delay time of the output of the detection coil 4 can be adjusted in the direction of increasing the detection delay time.

To describe the above-mentioned operation in more detail using the equivalent circuit shown in FIG. 2, it is generally known that when an input signal of alternating current magnetic flux is applied to the magnetic core 3, the following equation holds true.

-Ndφ/dt-Ldi/dt=iR...(1) where L: Inductance value of coil 6 R: Resistance value of resistor 7 N: Number of turns of coil 6 i: Circuit current flowing through coil 6 and resistor 7 φ: The magnetic flux passing through the magnetic core 3 Now, the AC magnetic flux φ as the input signal is φ=〓sinωt …(2) where 〓: Maximum value of magnetic flux ω: Signal angular velocity, then the steady solution of equation (1) is ...(3) However, ψ=tan ^-1 (-L/Rω) ...(4) e: Voltage across resistor 7.

That is, the circuit current i flowing through the detection delay time adjustment circuit formed by the coil 6 and the resistor 7 is
The phase will be delayed by ψ compared to the input signal of the equation. The output of the electromagnetic pickup is obtained by receiving the voltage induced in the detection coil 4 by the circuit current i from the output terminal 5 at high impedance and taking it out as a voltage output. ) The phase is delayed by ψ in the equation.

Now, this phase delay ψ shown in equation (4) is −
When L/Rω is small, it can be approximated as ψ≒−L/Rω (5), and it becomes a function that is approximately proportional to the angular velocity ω of the magnetic flux change of the input signal. In this case, the detection delay time of the output signal can be set to a substantially constant value regardless of the angular velocity ω.

Therefore, for example, when using the pick-up of this embodiment to detect various timings during engine rotation, if the delay phase is between zero and about 18 degrees,
Since the error between equation (4) and equation (5) is about 3% or less, the phase delay ψ can be considered to be a linear function as shown in equation (5), and as a result, This means that a desired constant delay time can be obtained with an accuracy of about 3% or less, regardless of the angular velocity, that is, the rotational speed of the engine.

FIG. 3 shows a side sectional view of another embodiment of the electromagnetic pickup according to the present invention, in which an annular delay time adjustment ring 8 made of a conductor having resistance as shown in FIG. This is an example of use as an adjustment circuit. In this embodiment, instead of the detection delay time adjustment coil 6 and the resistor 7 shown in FIG. The electrical equivalent circuit is the same as that shown in FIG. 2. In this embodiment, a desired detection delay time can be obtained by appropriately selecting and installing the inner diameter and cross-sectional area of the delay time adjustment ring 8.

Incidentally, by appropriately making a slit in the delay time adjusting ring 8 and gradually increasing the resistance value around the ring, the detection delay time can be adjusted in the direction of decreasing the time.

According to the present invention, the detection delay time of the electromagnetic pickup can be freely adjusted to a desired value due to the above-described configuration and operation. As a result,
Conventionally, the detection delay time was different for each electromagnetic pick-up, but now it can be adjusted to have a uniform detection delay time, which is useful when it is necessary to use a large number of electromagnetic pick-ups with the same characteristics on a production line. However, electromagnetic pickups with the same characteristics can be easily manufactured.

Furthermore, since the detection delay time of the electromagnetic pickup used in the device for detecting the timing of a rotating object can be managed and made uniform, the accuracy of the detection device can be improved.

Further, even if the detection delay time of the electromagnetic pickup changes due to aging or the like, this can be easily corrected according to the present invention.

[Brief explanation of drawings]

Figure 1 is a side cross-sectional view of an embodiment of the electromagnetic pickup of the present invention, Figure 2 is an electrical equivalent circuit diagram, and Figure 3 is an electrical equivalent circuit diagram.
The figure is a side sectional view of another embodiment, and FIG. 4 is a perspective view of the delay time adjustment ring. 3... Magnetic core, 4... Detection coil, 6... Coil for adjusting detection delay time, 7... Resistor for adjusting detection delay time, 8... Delay time adjustment ring.

Claims (1)

[Scope of utility model registration request] In an electromagnetic pickup used in a device for detecting the timing of a synchronous moving body, a detection coil having an output end is wound around a magnetic core made of a metal magnetic material, and a resistor that circles the magnetic core at least once to close the circuit. With a detection delay time adjustment circuit, characterized in that a circuit is provided close to the detection coil, and the time delay of the output of the detection coil is adjusted by adjusting the phase delay of the current flowing through the resistance circuit. Electromagnetic pick-up.