Electric contact switching device and power consumption control circuit

A load is connected with a power supply. An energizing electric contact and a transient current contact are connected electrically in parallel with each other and can do time-coordinated making and breaking operation. A capacitor is connected in series with the transient current contact. During breaking operation of the energizing contact and keeping making state of the transient current contact, a transient current from the power supply flows into the capacitor and delay voltage increase of the energizing contact using voltage drop at an internal resistance of the power supply and the load.

TECHNICAL FIELD

This invention relates to an electric contact switching device, a power consumption control circuit, a DC motor, a pantograph device, a connector, and a pulse generation device.

BACKGROUND ART

An electric contact switching device that mechanically makes and breaks an electric current, a relay and a sliding contact, etc. has features such as very low energizing resistance in making state, very high isolating electric resistance in off-state, excellent isolation between a control signal and a making/breaking contact circuit, and comparatively cheap manufacturing costs, compared with semiconductor switches. Therefore, it is widely used to make and break connection in an electric circuit where a power supply, an actuator, and a sensor, etc. are included in all fields such as information instruments, industrial equipments, cars, and consumer electronics. Moreover, it is said that the production of mechanical switches and the relays will keep increasing in the future.

A conventional electric contact switching device consists of a pair of electric contacts for making and breaking operations of an electric switching circuit. During breaking operation of a pair of electric contacts, the contacting area of each electric contact becomes narrow, and the current concentrates into only one contacting point, a molten metal bridge between contact electrodes glows and the bridge lastly evaporates. Further current concentration will lead to metal evaporation.

For the making and breaking operation of the large current from the high voltage power supply using the conventional electric contact switching device, whenever the energizing contact current exceeds the minimum arc discharge ignition current (minimum arc current) and the contact voltage exceeds the minimum arc discharge ignition voltage (minimum arc voltage), the arc discharge is inevitably ignited (for example, see Non-Patent Documents 1 to 4). The minimum arc current and the minimum arc voltage are decided depending on the kind of the electric contact material. The arc discharge in the contact is accompanied by heat generation at the electrodes and transfer of the contact material, and decreases the reliability and the lifetime of the relay for the large current making/breaking operation.

The conventional electric contact switching device consists of a couple of contact electrodes made of Cu metal plated with Au, Ag, Pd, or Pt for example, of which the resistivity is very low, and the contact resistance is very low. In order to suppress the arc ignition, the new materials with a high melting temperature and low resistivity for example, have been studied, and an atmosphere gas and the operation in vacuum have also been studied. However, there would be no applicable technology of arc ignition suppression for the conventional contact. To suppress the arc discharge as much as possible, heating the contact electrodes or decreasing the heat conductivity of the electrodes has been studied. However, it negatively affects a driving coil of the relay and its effect is so limited. The contact electrodes are sometimes mechanically divided into plurals to improve the reliability of contacts, and such contacts are called twin contacts. It has two mechanical springs for the making/breaking operation and for preventing an insulator obstacle of the contact, but not to suppress the arc ignition. The relay with two couples of contacts with different contact material has been proposed. They are operated in a timely-controlled manner. One contact, which operates earlier than the other, has low electric resistance for energizing the currents and the other contact, which operates behind the other, has high endurance to welding due to the arc ignition (see Patent Document 1). However, in this case, the arc ignition could not be suppressed. There would be no solution to suppress the arc ignition for the conventional contact.

In order to improve the reliability, high performance, miniaturization and low price, the following five problems are chiefly examined for the electric contact of the large current and the high voltage. The difficulty of problems mainly comes from the arc discharge during the breaking operation.

(1) Welding of the electric contacts

(2) Material transfer from the electrodes during breaking operations

(3) Contact resistance increase by chemical reaction or surface roughness (oxidation and sulfuration, etc.) on the surface of the electrode

(4) Miniaturization of the shape

(5) Decrease of serge generation

For the welding phenomenon of the electric contact in the above-mentioned (1), the molten metal bridge due to metal melting and metal evaporation generated by energizing current concentration into one spot is the main cause. It has a close correlation with the surface roughness and mass transfer of the electrodes due to the arc discharge. Because the arc current direction in a DC circuit is not changed, the problem for DC current switching is severer than for AC. The material transfer from the electrodes during the contact operations in the above-mentioned (2) is a complicated phenomenon of melting, evaporation, and the arc discharge. The contact resistance increase by the chemical reaction on the electrode surface in the above-mentioned (3) is induced by a rise in the metal temperature and an activated gas by the arc discharge. Miniaturization in the above-mentioned (4) of the contact device, the relay for example, is difficult due to the making/breaking mechanism against the arc discharge. The moving mechanism with a wide gap is inevitable to erase the arc discharge and a large contact force is necessary to overcome the roughened surface of the contact caused by the arc discharge for the low contact resistance. The serge generation in the above-mentioned (5) is induced inevitably at the breaking operation of the large current through an inductive load. When the large driving actuator breaks the large current with high velocity, bounce would occur and a complicated noise is generated due to a mechanical resonance of the moving electrode. Therefore, stable arc discharge, which starts as arc of the vaporized metal due to the arc discharge at the breaking operation and transfers to the arc of a surrounding gas, deteriorates the contact characteristics due to material consumption, material transfer and oxidation of the electrodes. If the arc ignition of the contact is suppressed, a lot of problems of the electric contact would be drastically solved.

Other than the electric contact switching device, generation of the arc discharge is also a problem for an armature of an electric motor or a pantograph of a train. For increasing the power consumption in the electrical equipments of cars, the higher voltage power supply is required for reducing electric power dissipation of a wiring. In the home electronics, a 300 V AC source would become popular for the higher power equipments. Therefore, the arc ignition of the electric contact becomes more important problem and the countermeasure has been studied eagerly.

As the arc discharge is estimated to be inevitable, metal composition, a thickness, a structure and a gap length of the contact electrodes are designed following to their deterioration factors to endure the target number of making/breaking cycles. Table 1 shows well known values of the minimum arc discharge current Imand the minimum arc discharge voltage Vm(see Non-Patent Document 5). For the electric contact of Au metal, the minimum arc discharge current Imis 0.38 A, and the minimum arc discharge voltage Vmis 15 V as shown in Table 1.

Table 1 shows the minimum arc electrical discharge currents and the minimum arc electrical discharge voltages in various metallic materials.

TABLE 1Determinations of Imand Vmin normal atmosphere, by various observers;Electrode diameter >> diameter of cathode spot; cf. Table (X, 3)ImVmAVMaterialIVESFINKHOLMIVESGAULRAPPFINKHOLMC0.020.0115.520Al18.314Fe0.730.35 to 0.558.013 to 15Ni0.20.58.014Cu1.150.4312.58.513Zn0.36(0.1)10.99.010.5Ag0.90.412.3812Cd(0.1)9.811Sb9.910.5Ta0.598W1.751.271.0 to 1.115.21015Pt0.671.00.7 to 1.11515.313.517.5Au0.380.420.3811.512.69.515Pb0.529.17.5

In order to quench the ignited arc discharge, a capacitor connected in parallel to the electric contact has been used as a quenching circuit. That is, the arc current at the contact is divided into the capacitor, the arc current becomes lower than the minimum arc discharge current, and the arc discharge disappears. For instance, it was reported that the minimum arc of Au is improved from 0.38 A to about 6 A by connecting the capacitor of 1 μF with the electric contact. However, there is a problem that the capacitor with the contacts decreases impedance for the AC current and is limited to the DC current. It means that isolation characteristics of the contacts decreases and the applicable circuits would be so limited. Adding to it, if the contacts are made during the capacitor is filled with high voltage charge, the rush current from the capacitor to the contact would raise the temperature of the metal contact and would cause welding of the contacts. To decrease the rush current from the capacitor to the contact, the resistance connected in series with the capacitor was proposed. However, the applicable circuits would be limited. A theoretical examination of the principle using the parallel capacitor to increase the minimum arc discharge current is insufficient, and the relation between the intercepted current and capacity of the capacitor and the high speed current change have not been theoretically examined.

A problem with the contact device other than the arc discharge is that the temperature near the contact surface rises by current concentration upon the breaking operation, leading to melting or evaporation of the metal. There is a theory, the “φ-Θ theory”, which can presume the highest temperature Tmaxnear the contact surface from the contact voltage VCof the electric contact (for example, see Non-Patent Document 5). Provided that ρλ=LT (the Wiedemann-Franz law) is formed, where an isothermal surface temperature on both ends of a current path is the room temperature (T0=300k) and the contact voltage is Vc, an approximate calculation of Formula (1) is obtained.
Tmax=((Vc2/4L)+T02)1/2≦3200·Vc[K](1)
Here, potential differences corresponding to a softening point temperature Ts, a melting point temperature Tm, and a boiling point temperature Tb of the current path material are called a softening voltage Vs, a melting voltage Vm, and a boil voltage Vb, respectively.

To overcome these problems, the arc quenching circuit comprising the capacitor connected in parallel to the electric contacts and another electric contact connected in series with the above-mentioned connectors with the capacitor was proposed. The two contacts synchronously perform the making or breaking operation (see Patent Document 2).

[Non-Patent Document 2] Atsuo Takahashi, “Research on generation area of point of contact arc”, Nippon Institute of Technology research report, 1976, Separate volume 1, p. 65

DISCLOSURE OF THE INVENTION

[Problems to be solved by the invention]

However, in the arc quenching circuit arrangement described in Patent Document 2, the electric contacts are connected in series with each other, so that, compared with the case where the number of the electric contact is one, the contact resistance doubles and the amount of energy losses and a calorific value double. For this reason, there is a problem that the power consumption increases. Additionally, since each electric contact needs the capacity which bears the energizing current, each electric contact becomes larger in size and the device cost increases. Since the supply voltage is certainly applied to the capacitor for arc quenching, it is necessary to use the pressure-resistant capacitor, which leads to the increase in the device cost and in the size.

From the view point of the above-mentioned problems, this invention is proposed to enable suppression of the arc ignition. Adding to it, the invention realizes the decrease in the device cost, miniaturization, and improvement in power dissipation for the electric contact switching device, the power consumption control circuit, the DC motor, the pantograph device, the connector, and the pulse generation device.

[Means for Solving the Problem]

In order to achieve the aforementioned object, an electric contact switching device according to a first aspect of the present invention is comprised of an energizing contact and a transient current contact with a capacitor connected in series with a switch, wherein the energizing contact and the transient current contact are connected electrically in parallel with each other, and the energizing contact and the transient current contact can do timely controlled making and breaking operations.

Even for the case of a complex circuit that consists of a power supply, a resistance, and an inductance, it is expressible by the series connection of an equivalent voltage power supply1and an equivalent impedance2using the Thevenin-Ho's theorem. Therefore, the switching operation can be examined in the equivalent circuit that combines them and switches3as shown inFIG. 36. A DC source, an AC source, and/or a pulse source are combined as the power supply1. However, every source can be uniformly treated if paying attention to the rapid transient phenomenon of the making/breaking operation compared with the time change of the power supply1as shown inFIG. 37.

As shown inFIG. 38, the ideal switch3, of which the resistance changes from zero to infinity and the response time is zero, does not cause the power consumption. However, as shown inFIG. 39, the actual switch3has non-zero resistance and has a gradient of resistance during the breaking operation. Therefore, the electric power is consumed in the contacts. As shown inFIG. 40, during breaking the contact current, the contact voltage rises from nearly zero to the source voltage. VI characteristics of the single switch3during the switching operation transfers from “a” to “b” inFIG. 40and passes through a power generation region.FIG. 41shows that a conventional electromagnetic relay has the arc discharge ignition with about half the voltage of the power supply voltage and also half the current of the load current during breaking the large current. It means the large power consumption in the contacts. If the inductance is neglected, the maximum power consumption occurs when the contact resistance is corresponding to the resistance of the load and the power supply1.

In an electric contact switching device according to the first aspect of the present invention, the energizing contact and the transient current contact can do timely controlled making and breaking operations, so that a transient current from the power supply by the resistance change between the contacts can be sent through the capacitor via the transient current contact. Thereby, voltage drop by the internal resistance of the power supply, the resistance of the load, and the inductance is generated, and the voltage immediately after the current interception of the energizing contact is not raised. This state corresponds to voltage shifting from point “a” to point “c” in the state near zero inFIG. 40.

After the energizing contact is broken completely, the transient current turns to zero in an instant by breaking the transient current contact, and the voltage of the energizing contact rises to reach the supply voltage. This state corresponds to the shifting from point c to point b inFIG. 40. Thus, the electric contact switching device according to the first aspect of the present invention can control the power consumption in the energizing contact at the breaking operation. Moreover, since the voltage or current of the energizing contact can be made below the minimum arc discharge voltage or below the minimum arc discharge current, generation of the arc discharge can be prevented.

As shown inFIG. 42, when intercepting the current which flows through an inductive load, such as a motor and a lamp, as a source of electromagnetic noise and beginning to send the current quickly through the load, such as the capacitor, surge noise occurs by the rapid change in the current. In the electric contact switching device according to the first aspect of the present invention, at the time of the breaking operation of the energizing contact, by sending the transient current through the capacitor via the transient current contact, it can prevent the current which flows through the load from falling rapidly, and it can be made the loose change. Thereby, the surge noise can be controlled.

In the electric contact switching device according to the first aspect of the present invention, since what is necessary is to set up the time to make the transient current contact and apply the supply voltage to the capacitor only at the time of breaking the energizing contact, the small capacitor with low pressure resistance can be used, and reduction in the material cost and a miniaturization can be attained. By breaking the transient current contact except the time of breaking of the energizing contact, the electricity hardly flows into the transient current contact. For this reason, the transient current contact smaller than the electric contact for current interception can be used, so that reduction in the material cost and miniaturization can be attained.

As for the electric contact switching device according to the first aspect of the present invention, it is preferred to have an arrangement where, when breaking the energizing contact, the transient current contact is made. In this case, the transient current from the power supply by the resistance change between the contacts under the breaking operation of the energizing contact can be sent through the capacitor via the transient current contact. In this manner, the voltage drop by the internal resistance of the power supply, the resistance of the load, and the inductance is generated and the power surge immediately after current interception of the energizing contact is suppressed, so that the power consumption in the energizing contact at the time of breaking can be controlled.

As for the electric contact switching device according to the first aspect of the present invention, it is preferred that the electric resistance or the switch is connected in parallel with the capacitor. In this case, the capacitor can be initialized after breaking the transient current contact with the electric resistance or the switch.

In the electric contact switching device according to the first aspect of the present invention, the capacity of the capacitor is preferably set so that, when breaking the energizing contact and the current value which flows through the energizing contact falls below the minimum arc discharge current value of the energizing contact, the voltage between the energizing contacts may fall below the minimum arc discharge voltage value. In this case, since, when breaking the energizing contact, either of the current or the voltage between the energizing contacts is always below the minimum arc discharge current value or below the minimum arc discharge voltage value, generation of the arc discharge can be prevented reliably.

The electric contact switching device according to the first aspect of the present invention is the device wherein the capacitor is set with the capacity where the voltage between the energizing contacts does not exceed the voltage V≈Tm/3200 (Tm: the melting point temperature of the energizing contact) or V≈Tb/3200 (Tb: the boiling point temperature of the energizing contact). In this case, from Formula (1), since the voltage between the energizing contacts is suppressed to the voltage lower than the melting voltage or the boiling voltage, when breaking the energizing contact, it can prevent the bridge phenomenon and metal evaporation from occurring in the energizing contact.

As for the electric contact switching device according to the first aspect of the present invention, it is preferred to have means to break and make the transient current contact mechanically or electrically, based on a breaking/making signal of the energizing contact. In this case, using the breaking/making signal of the energizing contact as a trigger, the timing of breaking and making the transient current contact can be arbitrarily set up mechanically or electrically.

The electric contact switching device according to the first aspect of the present invention has a rectification circuit instead of the transient current contact, and the rectification circuit may rectify the current that flows into the capacitor to save the electric charge in the capacitor when the energizing contact is broken. Moreover, the electric contact switching device according to the first aspect of the present invention may have the transient current contact connected in series with the rectification circuit. In this case, also when the speed of the change in supply voltage is higher than that of the breaking/making operation of the energizing contact, the charge can be saved in the capacitor when the energizing contact is broken, and it can prevent the steady current other than the transient current from flowing into the capacitor. For this reason, the transient current switch can be broken at a current zero state. Furthermore, by the rectification circuit, specification of the current direction of the capacitor becomes unnecessary in the case of the DC power supply, so that the capacitor with polarity such as an electrolytic capacitor can be used.

An electric contact switching device according to a second aspect of the present invention has the energizing contact and the transient current contact with the inductance connected in series with the transient current contact, wherein the energizing contact and the transient current contact are connected electrically in parallel with each other, and the energizing contact and the transient current contact can do timely controlled making and breaking operations.

As shown inFIG. 43, the power consumption is not produced with a switch3ideal in the circuit shown inFIG. 36. However, with the actual switch3, as shown inFIG. 44, the contact resistance is not zero and it changes in time before complete making. Thus, the power is consumed between the electric contacts. In the electric contact switching device according to the second aspect of the present invention, the energizing contact and the transient current contact can do timely controlled making and breaking operations, so that the transient current of the power supply which flows through the transient current contact can be restored to a regular value, and, after the voltage between the energizing contacts turns to substantially zero, the energizing contact can be made. Thereby, the power consumption in the energizing contacts at the time of making can be controlled.

In the electric contact switching device according to the second aspect of the present invention, at the time of making the energizing contact, by sending the transient current through the inductance via the transient current contact, so that it can prevent the current from flowing through the load rapidly, and it can be made a loose change. Thereby, the surge noise can be controlled.

As for the electric contact switching device according to the second aspect of the present invention, it is preferred to have an arrangement where, when making the energizing contact, the transient current contact is made. In this case, the transient current of the power supply which flows through the transient current contact can be restored to the regular value, and, after the voltage between the energizing contacts turns to substantially zero, the energizing contacts can be made. Thereby, the power consumption in the energizing contact at the time of making can be controlled.

In the electric contact switching device according to the first and second aspects of the present inventions, the energizing contact and the transient current contact may be constituted by a semiconductor switch. In this case, it is effective when breaking and making the energizing contact and the transient current contact at high speed. The semiconductor switch is constituted by such as a transistor, an FET, or a diode. When it is especially constituted by a power MOSFET which can deal with the large current, generation of heat at the time of making and breaking the switch can be suppressed.

A power consumption control circuit according to the first aspect of the present invention has the power supply, the load, and the electric contact switching device according to the first aspect of the present invention, wherein the load and the power supply are connected, the electric contact switching device is connected in series with the load, and wherein it has a configuration that, when breaking the energizing contact, the transient current contact is made so that the transient current from the power supply is sent through the capacitor, the voltage drop by the internal resistance of the power supply or the load is generated, and the power surge of the energizing contact is suppressed.

In the power consumption control circuit according to the first aspect of the present invention, when the energizing contact is broken, the transient current from the power supply is sent through the capacitor by making the transient current contact, and the voltage drop by the internal resistance of the power supply or the load is generated and the power surge of the energizing contact is suppressed, so that the power consumption in the energizing contact at the time of breaking can be controlled. Moreover, since the voltage or current of the energizing contact can be made below the minimum arc discharge voltage or below the minimum arc discharge current, generation of the arc discharge can be prevented.

In the power consumption control circuit according to the first aspect of the present invention, at the time of breaking the energizing contact, by sending the transient current through the capacitor via the transient current contact, so that it can prevent the current which flows through the load from falling rapidly, and it can be made a loose change. Thereby, the surge noise can be controlled.

In the power consumption control circuit according to the first aspect of the present invention, by setting up the time to make the transient current contact and apply the supply voltage to the capacitor only at the time of breaking the energizing contact, the small capacitor with low pressure resistance can be used, and reduction in the material cost and miniaturization can be attained. By breaking the transient current contact except the time of breaking the energizing contact, the electricity hardly flows into the transient current contact. For this reason, the transient current contact smaller than the electric contact for current interception can be used, so that reduction in the material cost and miniaturization can be attained.

The power consumption control circuit according to the second aspect of the present invention has the power supply, the load, and the electric contact switching device according to the second aspect of the present invention, wherein the load and the power supply are connected, the electric contact switching device is connected in series with the load, and wherein it has a configuration that, after making the transient current contact and the transient current of the power supply which flows through the transient current contact is restored to the regular value, the energizing contact is made.

In the power consumption control circuit according to the second aspect of the present invention, after making the transient current contact and the transient current of the power supply which flows through the transient current contact is restored to the regular value, it makes the energizing contact, so that it can control the power consumption in the energizing contact at the time of making. Moreover, at the time of making the energizing contact, the transient current is sent through the inductance via the transient current contact, so that it can prevent the current from flowing through the load rapidly, and it can be made a loose change. Thereby, the surge noise can be controlled.

A DC motor according to the present invention is a DC motor which contacts by turns a pair of brushes connected to the power supply with a pair of commutators provided on both ends of an armature, respectively, to send the direct current through the armature placed in a magnetic field, and to rotate the armature in response to an electromagnetic force, wherein, for the commutators to be electrically connected electrically in parallel with each other when contacted to the brush, each commutator has two contacts aligned in the direction of rotation and the capacitor connected in series with the contact at the back side of the direction of rotation.

Since the DC motor according to the present invention contacts the contact at the back side when the brush which contacts the contact at the front side of the direction of rotation separates from the contact by rotation of the commutator, it can send the transient current from the power supply through the capacitor. Thereby, the voltage drop by such as the internal resistance of the power supply is generated and the power surge between the brush and the contact at the front side is suppressed, so that generation of the arc discharge therein can be prevented and the power consumption can be controlled.

A pantograph device according to the present invention is a pantograph device for energization by contacting an overhead wiring, which has a pair of the pantographs and the capacitors, wherein the respective pantographs are arranged to be connected electrically in parallel with each other when contacted to the overhead wiring, and the capacitor is connected in series with one of the pantographs.

In the pantograph device according to the present invention, as long as one pantograph contacts the overhead wiring while the other pantograph is separated from the overhead wiring by such as vibration, it can send the transient current from the overhead wiring through the capacitor. Thereby, the voltage drop by such as the internal resistance of the overhead wiring is generated and the power surge between the overhead wiring and the other pantograph is suppressed, so that generation of the arc discharge therein can be prevented and the power consumption can be controlled.

A connector according to the present invention is a connector to conduct a socket side energizing line connected to a socket and a plug side energizing line connected to a plug by connecting the socket and the plug, wherein the connector has a socket side branch line, a plug side branch line, and the capacitor, and wherein the socket side energizing line has a socket side energizing contact, the socket side branch line is branched from the socket side energizing line and has a socket side transient current contact, the plug side energizing line has a plug side energizing contact, the plug side branch line is branched from the plug side energizing line and has a plug side transient current contact, and the capacitor is disposed either on the socket side branch line or the plug side branch line, and wherein the socket side energizing contact and the plug side energizing contact are made when the socket is connected to the plug, and the socket side transient current contact and the plug side transient current contact are made when the socket is connected to or removed from the plug, and wherein, while maintaining the making state, the socket side energizing contact and the plug side energizing contact are broken to remove the socket from the plug.

In the connector according to the present invention, when removing the socket from the plug, the socket side energizing contact and the plug side energizing contact are broken while the socket side transient current contact and the plug side transient current contact are in making state, so that it can send the transient current from the power supply through the capacitor. Thereby, the voltage drop by such as the internal resistance of the power supply is generated and the power surge between the socket side energizing contact and the plug side energizing contact is suppressed, so that generation of the arc discharge therein can be prevented and the power consumption can be controlled.

A pulse generation device according to the present invention has a rotor with a plurality of rotating electrodes, contact electrodes, and capacitors, wherein the respective rotating electrodes are separated by an insulator from each other and disposed symmetrically for a rotating axis of the rotor, each rotating electrode is constituted by a front side electrode placed at the front side of the direction of rotation of the rotor and a back side electrode placed at the back side of the direction of rotation, the front side and back side electrodes are connected electrically in parallel with each other to the power supply, and wherein the contact electrode is disposed so as to contact the respective rotating electrodes sequentially and intermittently during rotation of the rotor in the order corresponding to the front side electrode, the front and back side electrodes, and the back side electrode, and wherein the capacitor is connected in series with the respective back side electrode.

The pulse generation device according to the present invention can generate a current pulse train or a voltage pulse train, and can be used for such as an inverter device. Since the contact electrode is provided so as to contact the front side and back side electrodes of the respective rotating electrodes in the order corresponding to the front side electrode, the front and back side electrodes, and the back side electrode, when the contact electrode separates from the front side electrode, the transient current from the power supply can be sent through the capacitor. Thereby, the voltage drop by such as the internal resistance of the power supply is generated and the power surge between the contact electrode and the front side electrode is suppressed, so that generation of the arc discharge therein can be prevented and the power consumption can be controlled.

In the electric contact switching device according to the first and second aspects of the present inventions, as well as the power consumption control circuit according to the first and second aspects of the present inventions, by analyzing a waveform of the current flowing through the transient current contact or a voltage waveform of the capacitor or the coil connected in series, the property of the circuit in the state near an operating condition can be presumed as an equivalent circuit as shown inFIG. 1. In this case, while the energizing contact is made and the circuit is operating, the current in the transient current contact or the voltage of the capacitor or the coil is not generated, and the circuit which detects the current or the voltage is not affected and does not give the effect. Meanwhile, since the transient current contact is broken when the energizing contact is broken and the current is intercepted, the current in the transient current contact or the voltage of the capacitor or the coil is not generated as well, and that the circuit which detects the current or the voltage is not affected and does not give the effect.

[Advantage of the Invention]

According to the present invention, it can provide the electric contact switching device, the power consumption control circuit, the DC motor, the pantograph device, the connector, and the pulse generation device which can attain reduction in the material cost and miniaturization while preventing occurrence of the arc discharge.

DESCRIPTION OF THE REFERENCE CHARACTERS

10: power consumption control circuit

11: power supply

12: equivalent impedance for power supply or load

13: electric contact switching device

15: transient current contact

BEST MODE FOR CARRYING OUT THE INVENTION

Hereafter, embodiments of the present invention will be described based the drawings.FIGS. 1 through 25show a power consumption control circuit of a first embodiment of the present invention. As shown inFIG. 1, a power consumption control circuit10has a power supply11, an equivalent impedance12for such as the power supply and a load, and an electric contact switching device13.

The power supply11is constituted by a DC or AC power supply, and has an internal resistance. The equivalent impedance12for such as the power supply and the load can be expressed by series connection with the power supply11from the Thevenin-Ho's theorem. The electric contact switching device13is connected in series with the equivalent impedance12for such as the power supply and the load, and has an energizing contact14, a transient current contact15, breaking/making means (not shown), and a capacitor16.

The energizing contact14and the transient current contact15are constituted by a switch, respectively, and are connected electrically in parallel with each other. The energizing contact14and the transient current contact15can do timely controlled making and breaking operations.

As shown inFIG. 2, the breaking/making means is constituted so as to break/make the transient current contact15mechanically or electrically based on a breaking/making signal of the energizing contact14. The breaking/making means makes (turns on) the transient current contact15when breaking (turning off) the energizing contact14. Especially, as shown inFIG. 3, in order to suppress the voltage applying level to the capacitor16below a supply voltage at the time of breaking, the transient current contact15is broken immediately after the energizing current falls to substantially zero. It should be noted that the breaking/making means is specifically constituted as follows.

As an arrangement for mechanical synchronization, as shown inFIG. 4, the breaking/making means can be constituted, using the distance difference between the contacts, the elasticity difference of contact springs, the mass difference of the contacts, or the like, so that the transient current contact15may be broken and made with the time difference with breaking/making of the energizing contact14. The breaking/making means for a rotating type sliding contact may be constituted as shown inFIG. 5. With the arrangement shown inFIG. 5, an electrode C rotates in the clockwise direction to contact and energize an energizing electrode A. When it rotates further in the clockwise direction, it contacts a transient current electrode B near a narrow insulation area G while contacting the energizing electrode A. It rotates further, and the energizing electrode A is broken while contacting the transient current electrode B.

Additionally, as shown inFIG. 6, the breaking/making means may be a push button switch constituted by adjusting the contact positions of two mechanical spring contacts. In this case, as shown inFIG. 6(b), it can be seen that stable arc discharge is suppressed. It can also be seen that a transient current switch B at the time of breaking is shifted to OFF state before the capacitor16is charged completely with the supply voltage.

As an arrangement for electrical synchronization, as shown inFIG. 7, the breaking/making means can be constituted by combining two general-purpose electromagnetic relays, one being used as the energizing contact14and the other as the transient current contact15, using a driving current of the electromagnetic relays. In this case, as shown inFIG. 8, it can be seen that the arc discharge is suppressed completely. As shown inFIG. 9, it can also be seen that the stable arc discharge is suppressed from a trace on the surface of the electric contact after 100 times operations.

As shown inFIG. 1, the capacitor16is connected in series with the transient current contact15. The capacity of the capacitor16is set so that, when the energizing contact14is broken and at the time the current value which flows through the energizing contact14falls below the minimum arc discharge current value of the energizing contact14, the voltage between the energizing contacts14falls below the minimum arc discharge voltage value. In one example, it is set up as follows.

As shown inFIG. 10, the resistance between the energizing contacts14at the time of breaking, after exhibiting the transient characteristic which depends on the energizing current value due to a temperature rise by current concentration in the energizing contact14, results in a fully-broken stable state. As shown inFIG. 11, the resistance between the contacts is measured, and this resistance between the contacts as R(t) which carries out transitional change is incorporated in an equivalent circuit for transient current analysis shown inFIG. 12. It should be noted that the AC supply voltage could be treated similarly to that for DC. As shown inFIG. 13, the difference Δt between the time when the current falls below the minimum arc discharge current during breaking the energizing contact14and the time when the voltage rises above the minimum arc discharge voltage is calculated. The minimum arc discharge current value and the minimum arc discharge voltage value which vary depending on the material of the electric contact are calculated from the material constant shown in Table 1. If the values are negative, there is no time domain which both values are satisfied at the same time, and the arc discharge is not generated.

Actually, with the general-purpose electromagnetic relay which uses a silver alloy electrode, using R(t) measured as shown inFIG. 11, Δt is obtained by calculating the current and voltage as shown inFIG. 13in the circuit ofFIG. 12. As shown inFIG. 14, by comparing the current dependence of Δt which is calculated plural times by changing the current value and the value of the capacitor16with the current dependence of the arc discharge occurrence probability obtained by an electric discharge generating confirmation experiment which was actually conducted many times by changing the current value and the value of the capacitor16, their trends have a similarity. Thereby, it is understood that the technique of setting up the capacity of the capacitor16is appropriate.

Moreover, the capacity of the capacitor16is set so that the voltage between the energizing contacts14does not exceed the voltage V≈Tm/3200 or V≈Tb/3200, which corresponds to a melting point temperature Tm or a boiling point temperature Tb between the energizing contacts14. Thus, the capacity of the capacitor16is set to prevent, when breaking the energizing contacts14, a bridge phenomenon or metal evaporation from being generated in the energizing contact14.

Next, an operation will be described. It should be noted that an equivalent series resistance or an equivalent inductance of the capacitor16and the transient current contact15could be disregarded. As shown inFIG. 15, in the power consumption control circuit10, by making the transient current contact15using the breaking/making means when breaking the energizing contact14, the transient current from the power supply11is sent through the capacitor16, and the voltage drop due to the internal resistance of the power supply11or due to the equivalent impedance12for such as the power supply or the load is generated, so that the power surge of the energizing contact14can be suppressed. At this time, the power surge of the energizing contact14is determined by variation with time of the equivalent impedance12for such as the power supply and the load, the internal resistance of the power supply11, the capacity of capacitor16, and the resistance value of the energizing contact14. For this reason, the power surge of the energizing contact14can be designed to exhibit an arbitrary upward curve by changing the capacity of the capacitor16.

After breaking the energizing contact14completely, by breaking the transient current contact15using the breaking/making means, the transient current turns to zero in an instant, and the voltage of the energizing contact14rises to reach the supply voltage. Thus, the power consumption control circuit10can control the power consumption in the energizing contact14at the time of breaking. Additionally, since the capacity of the capacitor16is set so that, when breaking the energizing contact14, either of the current or the voltage between the energizing contacts14certainly falls below the minimum arc discharge current value or the minimum arc discharge voltage value, generation of the arc discharge can be prevented reliably.

As shown inFIG. 16. in the power consumption control circuit10, at the time of breaking the energizing contacts14, by sending the transient current through the capacitor16via the transient current contact15, it can prevent the current which flows through the equivalent impedance12for such as the power supply and the load from falling rapidly, and it can be made a loose change. Where the inductance, such as the equivalent impedance12for such as the power supply and the load, is L and the current is I, then the surge voltage V becomes V∝L (dI/dt), and the surge noise can be controlled. As shown inFIG. 17, a calculation result by a circuit simulation shows that, when the capacitor16is connected, the surge voltage becomes ⅕ or less as compared with when the capacitor16is not connected. Thus, it can be seen that the surge noise is controlled.

As shown inFIG. 15, in the power consumption control circuit10, since the time to make the transient current contact15and apply the supply voltage to the capacitor16is set only at the time of breaking the energizing contact14, the small capacitor16with large capacity and low pressure resistance can be used, and reduction in the material cost and miniaturization can be attained. Since the transient current contact15is broken except the time of breaking the energizing contact14, the electricity hardly flows into the transient current contact15. For this reason, the transient current contact15smaller than the electric contact for current interception can be used, so that reduction in the material cost and miniaturization can be attained.

The electric contact switching device13can apply its principle to all the switches which intercept the current. For example, it is applicable to such as a vacuum current breaker for large power or a semiconductor switch for an inverter.

As shown inFIG. 18, in the power consumption control circuit10, an electric resistance17or a switch18may be connected in parallel with the capacitor16. In this case, the capacitor16can be initialized after breaking the transient current contact15with the electric resistance17or the switch18. The transient current is restricted when the resistance is connected in series with the transient current contact15and the capacitor16. Moreover, when the inductance is connected in series with the transient current contact15and the capacitor16, it is assumed that the surge voltage may occur momentarily for the rush current to the capacitor16to generate the high voltage for a very short time in the order of picosecond or microsecond. However, since it occurs for a short time and the energy is small, there is little influence on the reliability or the lifetime of the electric contact switching device13.

Furthermore, as shown inFIG. 19, the power consumption control circuit10has a rectification circuit19connected in series with the transient current contact15and the capacitor16, and the rectification circuit19may rectify the current that flows into the capacitor16to save the electric charge in the capacitor16when breaking the energizing contact14. The rectification circuit19may be either for a full wave or a half wave. Where there is no rectification circuit19, as shown inFIG. 20, when the speed of the change in supply voltage is higher than that of breaking/making operations of the energizing contact14or the transient current contact15, the steady current other than the transient current may flow into the transient current contact15or the capacitor16while the energizing contact14is broken as well, and the transient current contact15may not be broken at a current zero state.

In contrast, where there is the rectification circuit19, as shown inFIG. 21, also when the speed of the change in supply voltage is higher than that of breaking/making operations of the energizing contact14, the electric charge can be saved in the capacitor16when the energizing contact14is broken, and it can prevent the steady current other than the transient current from flowing into the capacitor16. For this reason, the transient current contact15can be broken at a current zero state. Furthermore, by the rectification circuit19, since specification of the current direction of the capacitor16becomes unnecessary in the case of the DC power supply11, the capacitor16with polarity such as the electrolytic capacitor can be used.

As a result of a measurement in the circuit inFIG. 22, as shown inFIG. 23, it can be seen that the arc discharge is not generated. When the power supply11is made to apply DC 50 V in the circuit inFIG. 22, as shown inFIG. 24, it can also be seen that the arc discharge is not generated. As shown inFIG. 25, three circuits inFIG. 19(a) can be combined, for example, to be applied to a three-phase AC.

FIGS. 26 through 28show a power consumption control circuit of a second embodiment of the present invention. As shown inFIG. 26, a power consumption control circuit20has a power supply21, a load22, and an electric contact switching device23.

The power supply21is constituted by a DC or AC power supply, and has the internal resistance. The load22is connected to the power supply21. The electric contact switching device23is connected in series with the load22, and has an energizing contact24, a transient current contact25, and an inductance26.

The energizing contact24and the transient current contact25are constituted by a switch, respectively, and are electrically connected electrically in parallel with each other. The energizing contact24and the transient current contact25can do timely controlled making and breaking operations. The electric contact switching device23has a configuration that, after making the transient current contact25and the transient current of the power supply21which flows through the transient current contact25is restored to the regular value, the energizing contact24is made. The inductance26is connected in series with the transient current contact25.

Next, an operation will be described. As shown inFIG. 27, in the power consumption control circuit20, when the transient current contact25is turned on just before making the energizing contact24to connect the inductance26to the energizing contact24, the transient current value is restored to the regular value, and then the voltage between the energizing contacts24turns to substantially zero. The energizing contact24is made in the state. At this time, by making the contact resistance lower than the equivalent series resistance of the inductance26, the current flows through the energizing contact24. Thereby, the power consumption in the energizing contact24at the time of making can be controlled. Meanwhile, the transient current contact25can be broken at the time when the current value is substantially zero, which is determined by the ratio of the equivalent series resistance of the inductance26to the contact resistance of the energizing contact24.

As shown inFIG. 28, in the power consumption control circuit20, at the time of making operation of the energizing contact24, by sending the transient current through the inductance26via the transient current contact25, it can prevent the current from flowing through the load22rapidly, and it can be made a loose change. Where the inductance, such as the load22, is L and the current is I, then the surge voltage V becomes V∝L (dI/dt), and the surge noise can be controlled.

The electric contact switching device23can apply its principle to all the switches which intercept the current. For example, it is applicable to such as the vacuum current breaker for large power or the semiconductor switch for the inverter.

As shown inFIG. 29, in the power consumption control circuits10and20, the energizing contacts14and24and the transient current contacts15and25may be constituted by a semiconductor switch, respectively. In this case, it is effective when breaking and making the energizing contacts14and24and the transient current contact15and25at high speed. The semiconductor switch is constituted by such as the transistor, the FET, or the diode. When it is especially constituted by the power MOSFET which can deal with the large current, generation of heat at the time of making and breaking the switch can be suppressed. The constitution with the semiconductor switch is considered to provide a new technique for mounting or a circuitry design, as well as for an element design. As a result of a measurement in the circuit shown inFIG. 29, in both cases at the time of making the energizing switch shown inFIG. 30and at the time of breaking the energizing switch shown inFIG. 31, it can be seen that the power consumption is reduced and the surge noise is controlled.

FIG. 32shows a DC motor of an embodiment of the invention. As shown inFIG. 32, a DC motor30has a pair of brushes31, an armature32, and a pair of commutators33. The brush31is made from carbon and is connected to the power supply. The armature32is constituted by the coil and is placed in the magnetic field.

The respective commutators33are disposed on both ends of the armature32. The respective commutators33are constituted so that they contact respective brushes31by the turning of the armature32, send the DC through the armature32, and rotate the armature32by the electromagnetic force. Each commutator33has two contacts34,35and a capacitor36. The respective contacts34,35are aligned in the direction of rotation so that they may be connected electrically in parallel with each other when contacted by the brush31. The capacitor36is connected in series with the contact35at the back side of the direction of rotation.

Next, an operation will be described. The DC motor30applies the power consumption control circuit10shown inFIG. 1, forms the energizing contact14with the contact34at the front side of the direction of rotation and the respective brushes31, and forms the transient current contact15with the contact35at the back side and the respective brushes31. As shown inFIG. 32, since the DC motor30contacts the contact35at the back side when the brush31which contacts the contact34at the front side of the direction of rotation separates from the contact34by rotation of the commutator33, it can send the transient current from the power supply through the capacitor36. Thereby, the voltage drop by such as the internal resistance of the power supply is generated and the power surge between the brush31and the contact34at the front side is suppressed, so that generation of the arc discharge therein can be prevented and the power consumption can be controlled.

FIG. 33shows a pantograph device of an embodiment of the invention. As shown inFIG. 33, a pantograph device40has a pair of pantographs41,42and a capacitor43. The respective pantographs41,42are arranged to be connected electrically in parallel with each other when contacted to an overhead wiring44. The capacitor43is connected in series with one pantograph42.

Next, an operation will be described. The pantograph device40applies the power consumption control circuit10shown inFIG. 1, forms the energizing contact14with the overhead wiring44and the other pantograph41, and forms the transient current contact15with the overhead wiring44and one pantograph42. As shown inFIG. 33, in the pantograph40, as long as the other pantograph42contacts the overhead wiring44while the other pantograph41is separated from the overhead wiring44by such as vibration depending on its elasticity or structure, it can send the transient current from the overhead wiring44through the capacitor43. Thereby, the voltage drop by such as the internal resistance of the overhead wiring44is generated and the power surge between the overhead wiring44and the other pantograph41is suppressed, so that generation of the arc discharge therein can be prevented and the power consumption can be controlled.

FIG. 34shows a connector of an embodiment of the present invention. As shown inFIG. 34, a connector50has a socket51, a plug52, a socket side branch line53, a plug side branch line (not shown), a capacitor54, and an electric resistance55. A socket side energizing line56is connected to the socket51. The socket side energizing line56has a socket side energizing contact57at the tip. The plug52can be inserted in the socket51for connection, and a plug side energizing line58is connected thereto. The plug side energizing line58has a plug side energizing contact59at the tip. When the plug52is connected to the socket51, the plug side energizing line58can be conducted to the socket side energizing line56.

The socket side branch line53branches from the socket side energizing line56before the socket side energizing contact57, and has a socket side transient current contact60at the tip. The plug side branch line branches from the plug side energizing line58before the plug side energizing contact59, and has a plug side transient current contact61at the tip. The capacitor54is disposed on the socket side branch line53. The electric resistance55is disposed in parallel with the capacitor54.

Next, an operation will be described. The connector50applies the power consumption control circuit10shown inFIG. 1, forms the energizing contact14with the socket side energizing contact57and the plug side energizing contact59, and forms the transient current contact15with the socket side transient current contact60and the plug side transient current contact61.

As shown inFIG. 34, in the connector50, when the plug52is inserted in the socket51for connection, the socket side energizing contact57and the plug side energizing contact59are made. Thereby, the socket side energizing line56and the plug side energizing line58are conducted. When the plug52is removed from the socket51, the plug52is rotated with regard to the socket51to make the socket side transient current contact60and the plug side transient current contact61, and then break the socket side energizing contact57and the plug side energizing contact59while maintaining the making state. At this time, the transient current from the power supply can be sent through the capacitor54. Thereby, the voltage drop by such as the internal resistance of the power supply is generated and the power surge between the socket side energizing contact57and the plug side energizing contact59is suppressed, so that generation of the arc discharge therein can be prevented and the power consumption can be controlled. In this state, the plug52is drawn out from the socket51.

FIG. 35shows a pulse generation device70of an embodiment of the present invention.

As shown inFIG. 35, a pulse generation device70has a rotor71, a plurality of rotating electrodes72, a contact electrode73, a connection electrode74, a capacitor75, and an electric resistance76. In this case, the pulse generation device70applies the constitution shown inFIG. 5.

The rotor71is constituted by a disk and has an insulator on the surface.

The respective rotating electrodes72are separated by the insulator from each other and disposed on the surface of the rotor71symmetrically for a rotating axis of the rotor71. Each rotating electrode72is constituted by a front side electrode A placed at the front side of the direction of rotation of the rotor71and a back side electrode B placed at the back side of the direction of rotation. The respective rotating electrodes72are disposed so that a spacing72awith the adjacent rotating electrode72is wider than a spacing72bbetween the front side electrode A and the back side electrode B. The front side electrode A extends further toward the periphery of the rotor71than the back side electrode B. The front side electrodes A of the respective rotating electrodes72are connected electrically in parallel with each other. The back side electrodes B of the respective rotating electrodes72are connected electrically in parallel with each other. The front side electrode A and the back side electrode B are connected electrically in parallel with each other to the power supply77.

The contact electrode73is connected to one terminal of the power supply77, and is disposed so as to contact the respective rotating electrodes72sequentially and intermittently during rotation of the rotor71. The contact electrode73is formed so that width73awhich contacts the respective rotating electrodes72is narrower than the spacing72abetween the respective rotating electrodes72and wider than the spacing72bbetween the front side electrode A and the back side electrode B. The contact electrode73is disposed to contact the front side electrode A and the back side electrode B of the respective rotating electrodes72in the order corresponding to the front side electrode A, the front and back side electrodes A and B, and the back side electrode B.

The contact electrode74is connected to the other terminal of the power supply77, and is disposed near the periphery of the rotor71so as to contact the front side electrode A of the respective rotating electrodes72sequentially and not to contact the back side electrode B during rotation of the rotor71. The contact electrode74is formed so that width74awhich contacts the front side electrode A of the respective rotating electrodes72is wider than a spacing72cbetween the front side electrodes A of the respective rotating electrodes72. The contact electrode74always contacts any of the front side electrodes A of the respective rotating electrodes72.

The capacitor75is connected in series with the back side electrode B of the respective rotating electrodes72.

The electric resistance76is disposed in parallel with the capacitor75.

Next, an operation will be described.

The pulse generation device70applies the power consumption control circuit10shown inFIG. 1, forms the energizing contact with the front side electrode A and the contact electrode73, and forms the transient current contact with the back side electrode B and the contact electrode73.

The pulse generation device70can generate the current pulse train or the voltage pulse train, and can be used for such the inverter device. Since the contact electrode73is provided so as to contact the front and back side electrodes A and B of the respective rotating electrodes72, in the order corresponding to the front side electrode A, the front and back side electrodes A and B, and the back side electrode B, when the contact electrode73separates from the front side electrode A, the transient current from the power supply77can be sent though the capacitor75. Thereby, the voltage drop by such as the internal resistance of the power supply77is generated and power surge between the contact electrode73and the front side electrode A is suppressed, so that generation of the arc discharge therein can be prevented and the power consumption can be controlled.