Timing Apparatus Using Electrochemical Memory Device

Abstract

An electrochemical potential memory device comprising a cathode mainly comprising silver, an anode mainly comprising silver chalcogenide, and a silver ion conductive solid state electrolyte sandwiched therebetween is connected to a current source for selectively driving the device in a charging state or discharging state and to a high input impedance direct current amplifier responsive to the terminal voltage of the device, and a timing operation signal proportional to the lapse of the charging or discharging time is obtained from the amplifier. In a preferred embodiment, the potential memory device comprises a main cathode for supply of the charging or discharging current and an auxiliary cathode for detecting the terminal voltage of the device, the latter being connected to the high input impedance amplifier. The timing apparatus employing such device eliminates disadvantageous influence caused by an overvoltage as occurs at the time of current conduction in the device.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a solid state timing apparatus using an electrochemical potential memory device. More specifically, this invention relates to such a solid state timing apparatus that can provide visual indication of the passing of any preset time.

2. Description of the Prior Art

A timing apparatus or a timer has been widely used to control the operation of any given apparatus after a preset time interval. One such type timer is of a mechanical structure. Such a mechanically built timer usually comprises a timing mechanism driven by motor, spring or the like. However, such a mechanical timer is disadvantageous in that a reduction gear mechanism inevitably employed in the timer for this purpose is complicated, with the result that miniaturization is difficult, the mechanism is readily vulnerable to troubles and furthermore the motor, if employed, must be of relatively high power.

A solid state type timer was also proposed and has already been commercially employed. The typical type of such existing solid state timer usually uses the charging or discharging time constant of an RC circuit, or the resistor-capacitor circuit. In more detail, a timing output signal is provided as a function of the charged or discharged voltage of the capacitor present in such RC circuit. It is apparent that such capcitor voltage changes exponentially and therefore is unsuitable for any prolonged timing operation. Usually, such capacitor voltage is merely applicable to a short timing operation that cannot exceed a few minutes at most. Accordingly, it is highly desirable to provide such solid state timing apparatus that can precisely set to any given time to relatively longer duration.

Professor Takehiko Takahashi and Assistant Professor Osamu Yamamoto, Technological Department of Nagoya University, announced their study on the electrochemical potential memory by the use of a solid state electrolyte at the b 22nd annual assembly of Japan Chemical Association held on Apr. 5th to 7th, 1969. Briefly stated, this device comprises an Ag electrode as a cathode, an Ag-Te alloy electrode as an anode, and a solid state electrolyte having high ion conductivity, such as RbAg.sub.4 I.sub.5 sandwiched between both electrodes. When a DC voltage is applied to the device so that the Ag electrode may be negative, a portion of Ag contained in the Ag-Te alloy electrode migrates over to the Ag electrode, resulting in a decreased activity of Ag in the Ag-Te alloy, and thus an increased potential difference between both electrodes. The inventors of this device termed this state of operation as "charging." When the polarity of the applied DC voltage is reversed relatively to that of the former case, Ag is refilled into the Ag-Te alloy, resulting in a decreased potential difference and return to the initial value eventually. The inventors of this device termed this state of operation as "discharging." Study disclosed by the inventors of this device indicates that the electromotive force generated by the aforementioned charging or discharging current can cause linear change to some extent with respect to the charging or discharging time. Thus, this device makes it possible as an outstanding characteristic to do write-in and non-destructive read-out operation while preserving relatively linear relation between the charging or dischrging time and terminal voltage, and in addition, it can hold the memory condition for a relatively longer period of time. These advantages mean that this device has opened a way for its potential use as an analogue memory device.

In view of these advantageous characteristics of the aforementioned memory device, it may be possible to utilize this device as an essential component of solid state timing apparatus. The invention described in this application has been thus accomplished by the inventors in order that such possibility may be realized. Accordingly, details of the aforementioned memory device which is the foundation of this invention will be further described in the subsequent section of Description of the Preferred Embodiment.

SUMMARY OF THE INVENTION

Briefly stated, this invention comprises a solid state electrochemical potential memory device comprising a cathode including an active metal, an anode including an alloy including said metal, and a solid state electrolyte having high ion conductivity sandwiched therebetween, said device showing a voltage between said anode and cathode linearly changing as a function of the charging or discharging quantity of electricity supplied to said device in a direction of the anode being positive or the anode being negative, respectively; a means for charging or discharging said device by substantially a constant current flowing therethrough in a selected direction; and a means for providing a signal that is proportional to the lapse of the time of charging or discharging operation of said device in response to the terminal voltage of said device. As mentioned in the section of the Description of the Prior Art and also as described hereinafter in detail, substantially a constant current flows through the aforementioned electrochemical potential memory device when a given voltage is applied in a charging or discharging manner, and the terminal voltage or electromotive force of this device increases or decreases in proportion to the flowing time. Accordingly, such signal proportional to said charging or discharging time is practically applicable to the purpose of timing operation such as performed by a timer, sequence programmer or the like. This signal is also available for the energization of such indicator that is provided with a timing scale along with the aforementioned operation and provides visual indication of the lapse of time. Quite clearly, such timing apparatus of the invention is of a solid state type and thus may be built in small dimensions and is economical in power consumption, and makes the timing operation possible for a relatively longer period of time.

In a preferred embodiment, the terminal voltage of the potential memory device is sensed by means of an amplifier having a high impedance input, such as a field effect transistor. In a more preferred embodiment, the memory device comprises a main cathode for the charging and discharging operation and an auxiliary cathode available for the sensing of terminal voltage, both being discrete to each other. Such embodiment enables more precise timing operation of such timing apparatus.

In a more preferred embodiment, charging cycle of the device is rapidly carried out for the purpose of time setting, whereas the discharging cycle of the device is slowly carried out for the purpose of timing operation.

Therefore, an object of this invention is to provide an improved solid state timing apparatus.

Other object of this invention is to provide a solid state timing apparatus that is capable of performing timing operation for a relatively longer period of time.

Another object of this invention is to provide a solid state timing apparatus that provides visual indication of the lapse of time.

A further object of this invention is to provide a timing apparatus incorporating a solid state potential memory device that generates a terminal voltage proportional to the quantity of electricity passing therethrough.

Still a further object of this invention is to enable precise timing operation of the timing apparatus using a solid state potential memory device.

It is a further object of this invention to provide an improved solid state potential memory device using a solid state electrolyte suitable for use in a timing apparatus.

It is still a further object of this invention to provide an improved solid state potential memory device using a solid state electrolyte suitable for use in a timing apparatus, said device avoiding unfavorable influence caused by the overvoltage of the device.

It is a further object of this invention to enable rapid time setting of the timing apparatus using a solid state potential memory device.

These objects and other objects and features of the present invention will become apparent from the following detailed description of the preferred embodiments taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a schematic sectional view of an electrochemical potential memory device for use in a timing apparatus of this invention,

FIG. 2 illustrates a graph showing characteristics between the terminal voltage and the charging or discharging time of the device shown in FIG. 1,

FIG. 3 illustrates the basic concept of an embodiment of this invention in a block form,

FIG. 4 illustrates a more detailed schematic diagram of the embodiment shown in FIG. 3,

FIG. 5 illustrates another embodiment of this invention that has been developed, based in part on the embodiment shown in FIG. 4,

FIG. 6 illustrates a schematic sectional view of another embodiment of the electrochemical potential memory device whcich is particularly suitable for the embodiment of this invention,

FIG. 7 illustrates, partially in a block form, a schematic diagram of an embodiment of this invention that incorporates the device shown in FIG. 6,

FIG. 8 illustrates a graph showing voltage holding characteristics after the cutting of the current of the device shown in FIG. 6,

FIG. 9 illustrates a graph showing voltage holding characteristics after the cutting of the current of a similar structural and yet more preferred embodiment of the device shown in FIG. 6,

FIG. 10 illustrates a schematic diagram of the timing apparatus of another embodiment of this invention, and

FIG. 11 illustrates a graph for explaining the operations of the embodiment shown in FIG. 10.

In the drawings, like parts are indicated by like reference characters.

DESCRIPTION OF THE PREFERRED EMBODIMENT

As described in the foregoing section of Description of the Prior Art, this invention utilizes the prior art electrochemical potential memory device including a solid state electrolyte. As described already, this device has a significant characteristic of the terminal voltage or electromotive force changing in an approximately linear way with respect to the charging or discharing quantity of electricity passing therethrough. Accordingly, prior to a detailed description of this invention, it would be appropriate to give a more detailed description of such electrochemical potential memory device.

FIG. 1 illustrates a schematic sectional view of an electrochemical potential memory device 1 which is used in the apparatus of this invention. It may be considered that this device is a kind of cell which comprises a solid state electrolyte 4 of high ion conductivity, such as RbAg.sub.4 I.sub.5 or Ag.sub.3 SI, sandwiched between a cathode 2 mainly including silver (Ag) and an anode 3 mainly including an alloy of silver and a member selected from the group consisting of sulfur (S), selenium (Se) and tellurium (Te), preferably an Ag-Te alloy. When a DC voltage is applied between both electrodes of this device 1 in such way that the anode 3 of this device may be positive and the cathode 2 may be negative, silver contained in the Ag-Te alloy in the anode 3 is ionized to be dissolved into the solid state electrolyte 4 and is deposited on the cathode 2. In this specification, such state of operation is referred to as "charging" hereinafter. When a DC voltage is applied to the aforementioned device in the directly opposite polarity to the above case, silver deposited over the cathode 2 migrates onto the anode 3 and is deposited thereupon. In this specification, such state of operation is referred to as "discharging" hereinafter.

FIG. 2 is a graph which indicates the relation between the charging or discharging time and the electromotive force of the aforementioned device by taking the current for charging or discharging the device as a parameter. As illustrated in the FIG. 2, the following facts of function have been clarified; that the electromotive force of this device as a cell indicates the value dependent upon the activity of silver contained in the Ag-Te alloy of cathode 3, that the activity of silver varies to a large measure by any slight charging or discharging performance when the atomic composition ratio of silver and tellurium contained in the Ag-Te alloy approximates to a value of 2, and that the relation between the aforementioned electromotive force and the charging or discharging quantity of electricity i.sup.. t, where i is a current value and t is time, generally indicates a linear relation during the charging or discharging period in case of the electromotive force of relatively low voltage range (from 0 (zero) to 100mV. as per the embodiment illustrated in the FIG. 2) and also in case of the current density of relatively low order (less than 100 .mu.A/cm.sup.2 as per the embodiment illustrated in the FIG. 2). In this connection, it is to be pointed out that application of a given voltage to the device in either charging or discharging manner causes substantially a constant current to flow therethrough and therefore the said linear relation is also applicable to the characteristic between the terminal voltage of the device and the charging or discharging time.

It has further been known that this device has an additional characteristic capable of holding the potential established immediately before cutting the current even after the cutting of the current supplied to this device for the aforementioned voltage range (from 0 (zero) to 100mV. as per the embodiment illustrated in the FIG. 2).

Accordingly, this invention is directed to providing such timing apparatus as to function to indicate the passing of the preset time by detecting the terminal voltage of the device by the use of the advantageous linear characteristic in a preselected region obtainable between the supplied quantity of electricity i.sup.. t, where t is the lapse of time and the terminal voltage of this device.

FIG. 3 illustrates a block diagram that indicates the most fundamental structure of the timing apparatus of this invention. The timing apparatus illustrated in the FIG. 3 basically comprises the aforementioned electrochemical memory device 1, a power source and switching circuit 11 for switching the polarity of the voltage being applied to the device 1 for the charging or discharging performance, a high input impedance initial step amplifier 12, preferably a differential amplifier comprising a pair of field effect transistors, a latter step amplifier 13, such as a differential amplifier comprised of a pair of bipolar transistors, and an indicating device 14 like an analogue indicating device such as ammeter or like an appropriate digital indicating device.

The initial amplifier 12 apparently functions to detect the voltage of the device 1. It is preferable to use an amplifying device of high input impedance, such as a field effect device, so as to prevent the drop of potential in this device caused by formation of a closed circuit with respect to the potential of this device through the attached circuit.

FIG. 4 illustrates a schematic diagram of an embodiment of this invention for implementation of the block diagram shown in FIG. 3. In the FIG. 4, portions corresponding to those of a block form in FIG. 3 are designated by the same reference characters.

Referring to FIGS. 3 and 4, the following description covers the structure of an embodiment of this invention and its operation. The potential memory device 1 has its anode 3 connected to the ground and the cathode 2 connected to the negative voltage bus -Vcc through a charge contact 21c of a switch 21 (as shown) alternatively connected to the positive voltage bus +Vcc through a discharge contact 21d, thereby allowing the switch to be switched to the charge, discharge or open (at a contact 21n) position. A variable resistor 22 is provided in the charge/discharge circuit for setting a value of the constant current fed to the device during the charging or discharging period. Adjustment of the variable resistor 22, for example by means of a rotatable knob or push button, permits the selective setting of the operation time range in the graph shown in FIG. 2.

First, the charging operation of the device 1 will be considered. When the switch 21 is turned from the open position 21n to the charge position 21c and at the same time an apparatus being controlled (not shown) is caused to start its operation, the voltage of the device 1 increases linearly as illustrated in FIG. 2. This potential is then fed to the input of the initial stage differential amplifier comprising field effect transistors TR1 and TR2 through the resistor 23. This potential is detected by the gate of said transistor TR1, while the gate of the other FET TR2 is connected to the ground through the high value resistor 24. These two transistors TR1 and TR2 are so connected as to function as a differential amplifier for effecting impedance conversion and voltage amplification. Outputs at both drains of the transistors TR1 and TR2 are fed to bases of bipolar transistors TR3 and TR4, respectively, of the succeeding stage differential amplifier 13.

An ammeter 14 is inserted between the collectors of said transistors TR3 and TR4 through the regulating resistors 25 for regulating the balance so as to amplify the device voltage linearly. Accordingly, passing of the operating time can be indicated by the ammeter 14. As an alternative embodiment of such indicator means 14, a number of indicating lamps may be used in place of said ammeter for indicating the operating time in a digital manner by flickering these lamps in successive order in response to the device voltage.

The collector of one transistor TR3 of both transistors in the latter stage amplifier 13 is connected to an output transistor TR5 through an appropriate base bias resistor so as to provide a single-ended output, which is then taken out through the output OUT as an output for load driving or for program controlling.

If the charging is discontinued by switching the switch 21 to a position 21n, the device 1 holds a potential proportional to the charging quantity of electricity so far fed to the device and accordingly, it is possible to retain the indication of the indicator means 14, or to keep a needle of ammeter or indicating lamps for digital indication in the indicated position or state.

If the switch is turned to the discharging position after the required charging operation, the voltage of the device 1 linearly decreases contrary to the preceding case along the characteristic curve as illustrated in FIG. 2, and accordingly, it is also feasible to operate the indicator means 14 so as to indicate the detected voltage of the device, as in the preceding case.

FIG. 5 illustrates a circuit of another embodiment of this invention, in which the embodiment shown in FIG. 4 has been partially modified or developed. More specifically, the embodiment of FIG. 5 additionally comprises a circuit for effecting DC amplification of the output of said transistor TR5 by means of transistors TR6 and TR7 arranged in successive order so as to control a transistor TR8 for driving a relay 26. Other portions are the same as those of FIG. 4 and the same portions are indicated by the same reference characters. Operating level of transistors TR5, TR6, TR7 and TR8 are so selected that the relay 26 may be operated by any optionally preset voltage in the device 1. Accordingly, it is possible to control the equipment being controlled (not shown), or to effect on/off operation of energization of such equipment at any preset time by using the contact of said relay. If a plurality of output circuits each comprising such transistor amplifying circuit and relay are provided so that the operating level of respective output circuits may be different from each other, it would be possible to effect the programming control of such equipment in any required timing sequence.

The embodiment of FIG. 5 shows an example in which such relay is utilized for a specific purpose. More specifically, a normally closed switch 27 engageable with said relay 26 is inserted in the charging circuit as shown in FIG. 5 in order that the charging may be effected only within a range in which the voltage characteristic of the device 1 is substantially linear. The above-mentioned relay 26 is so adjusted that the aforementioned normally closed switch 27 may be opened when the device voltage exceeds the voltage range that indicates relatively desirable linear character as mentioned with reference to FIG. 2, for example, when the device voltage reaches a range between 100 to 120 mV. Thus, regulation is effective to permit the charging operation only within a range in which the voltage characteristic of the device 1 is linear, and prevents the device 1 from excessive charging thereupon.

It is understood that each of the embodiments described with reference to FIGS. 1, 4, and 5 includes a common terminal corresponding to a single cathode by means of which the charging or discharging current is supplied and also the terminal voltage of the device 1 is detected. In this connection it is recalled that the device shown in FIG. 1 can be considered as a cell, as mentioned previously. Therefore, in case of such device as comprising the common cathode for supply of the current and for detection of the terminal voltage, the detected output voltage is a total of an electromotive force of the device and of an overvoltage of the device as a cell. This results in the fact that the start or the stop of the electric current conduction into the device 1 causes influence of the overvoltage on the detected voltage and therefore the output voltages detected at each device 1 immediately before and after the change to a different electrical current conduction state. This means that the voltage holding characteristic of the device is degraded. For example, when the switch 21 is opened or turned to the open position 21n in the course of charging or discharging the device 1, indication by the indicating means 14 varies from such indication that should correspond to the time in which charging or discharging was actually done. It has been found that the said degradation of the voltage holding characteristic is aggravated by the fact that an increased current for charging or discharging the device causes a greater overvoltage, resulting in more inaccurate indication. Thus it is desired to provide an improved potential memory device that eliminates the abovementioned problem.

The overvoltage as occurs in the electrochemical potential memory device causing a voltage drop after the cutting of the current conduction into the device may be classified as follows:

1. A voltage drop caused by the current flowing through the resistance involved in the solid state electrolyte of the device (or an IR drop across the resistance in the electrolyte).

2. An overvoltage caused by dissolution or deposition of Ag at an interface between the electrolyte and the anode or cathode.

3. An overvoltage caused by diffusion of Ag ion into the anode.

FIG. 6 shows a schematic sectional view of an improved electrochemical potential memory device 30 for eliminating the IR drop across the resistance in the electrolyte as described in the above subsection (1) and the overvoltage caused by dissolution or deposition of Ag as described in the above subsection (2). The device 30 shown in FIG. 6 is basically characterized by the provision of an auxiliary cathode that comprises an output terminal for detecting the potential separately from the aforementioned cathode available for the input terminal for the current conduction. More specifically, the device 30 shown in FIG. 6 essentially comprises a solid state electrolyte 31 composed of Ag.sub.3 SI, an anode 33 composed of an Ag-Te alloy, a cathode composed of Ag, and an auxiliary cathode 34 composed also of Ag.

FIG. 7 illustrates a block diagram that describes the basic concept of the timing apparatus of this invention using an electrochemical memory device that has such auxiliary cathode 34 as described above. The cathode 32 of the device 30 is connected to the switch 21 through a variable resistor 22, while the auxiliary cathode 34 is connected to the first stage amplifier 12, and the anode 33 is connected to the ground. Circuit connections of FIG. 7 are basically the same as those which are described with reference to FIGS. 4 and 5, and the same or corresponding portions are designated by the same or corresponding reference characters. Operation of the timing apparatus using said memory device that has an auxiliary electrode will be described in more detail later with reference to a specific embodiment of such circuit shown in FIG. 10.

Returning to FIG. 6, a more detailed description is given with respect to an embodiment of the memory device that has the aforementioned auxiliary electrode. 70 mg and 20 mg of silver powder of 200 mesh each are weighed out, which are then pressed by approximately 5 tons/cm.sup.2 pressure generated by metal mold jig of 70 and 30, respectively, followed by forming into silver pellets for the main cathode and the auxiliary cathode. The prepared two silver pellets are then laid over the metal mold jig of 120 so as not to be in contact with each other, and then 1,000 mg of Ag.sub.3 SI powder of 200 mesh is put upon the metal mold to plane the surface, and further 200 mg of Ag.sub.2 Te alloy of 200 mesh grain is put on it, followed by pressing and molding with approximately 2 tons/cm.sup.2 pressure.

FIG. 8 illustrates a graph that indicates the potential holding characteristic of the device of FIG. 6 in comparison with that of the device of FIG. 1, and the curve (a) therein shown indicates the case of FIG. 1 embodiment and the curve (b) therein shown indicates the case of FIG. 6 embodiment, respectively. The reason why the characteristic of the device may be improved by practicing the embodiment of FIG. 6 as mentioned above is that no deposition of Ag on the auxiliary cathode from the opposite electrode during the charging period and no dissolution of Ag from the auxiliary cathode towards the opposite electrode during the discharging period take place because the auxiliary cathode is not used as a terminal for current conduction of the device, and consequently, an overvoltage that might arise at the interface between the electrolyte and the auxiliary cathode (that is, an overvoltage caused by deposition of Ag ion onto the metal Ag at the charging cycle as well as an overvoltage caused by the dissolution of Ag ion into the electrolyte at the discharging cycle) and the resistive polarization in the electrolyte are removed from the detected voltage. By taking the output voltage of this auxiliary cathode, accurate detection of the electromotive force of the device is thus possible without being affected by the aforementioned over-voltage.

Another solution of avoiding the disadvantageous influence by the overvoltages may be directed to the overvoltage caused by diffusion of Ag ion into the anode, as mentioned in the previous subsection (3). It has been found that the charging or discharging by an increased current fed to the device gives rise to a disadvantageously increased overvoltage, resulting in more aggravated degradation of the voltage holding characteristic of the device. Thus, it is also desired to provide such an electrochemical potential memory device as satisfactory in the potential holding characteristic even in case of charging or discharging the device by a greater current in a shorter period of time.

The following is a description of preferred embodiment for implementing such an improved voltage holding characteristic. This embodiment will be hereinafter described as embodied in a device of such structure as shown in FIG. 6, though this should not be construed by way of limitation. The inventors knew that the degradation of said characteristic affected by the above-mentioned overvoltage was solved by selecting the thickness of anode comprising three members, namely, Ag-Te alloy, graphite, and solid state electrolyte, in other words, a fact that the diffusive migration of the silver ion present in the anode 33 could affect the aforementioned degradation strongly. They followed up experiments repeatedly by varying the thickness of the anode 33 in various way. As a result, they reached a conclusion that the degradation of said characteristic under the influence of overvoltage could take place noticeably if the thickness of the anode 33 exceeds 1 mm as the borderline. The embodiment hereinafter described utilizes such conclusion thus obtained.

The following describes one of the fabrication examples as regards the device of such preferred embodiment. 100 mg and 20 mg of silver powder of 200 mesh each are weighed out and then preliminary pressing is given to the both lots with pressure of approximately 0.5 ton/cm.sup.2 by means of metal mold jig of 70 and 30, respectively, so as to form silver pellets available for the cathode and also for the auxiliary cathode. Then, the above-mentioned two silver pellets are laid upon a metal mold jig of 120 so as not to be in contact with each other. Then 500 mg of Ag.sub.3 SI powder of 200 mesh is put on them to plane the surface. The 500 mg of anode material comprising a mixture of Ag.sub.2 Te powder of 200 mesh (as the main), graphite and Ag.sub.3 SI powder is put onto the abovementioned planed material to plane the surface thereof, followed by pressing with approximately 2 tons/cm.sup.2 pressure for molding.

FIG. 9 illustrates a graph that indicates the correlation between the thickness of the anode 33 and the potential holding characteristic of the device 30 prepared in accordance with the above-mentioned process. Curve (a) shown in the graph indicates the characteristic of the device of the embodiment just described and the curve (b) indicates that of the device described in connection with FIG. 1. Table 1 indicates the correlation between the thickness and the weight of the embodiment shown as a parameter in FIG. 9.

TABLE 1

Weight of anode (mg) 300 450 600 750 900 Thickness of anode (mm) 0.5 0.75 1.0 1.25 1.5

As seen from FIG. 9, when thickness of the anode 33 is reduced to less than 1 mm, the characteristic of the device is remarkably improved. One possible reason may be considered as follows. As soon as the electric current starts to flow through the device, activity of silver at the anode portion in contact with the solid state electrolyte starts to change in the first step and then the silver activity becomes uniform by diffusive migration of the silver ion. However, in case of a greater current flowing through the device, stronger influence can be caused by the migrative diffusion, or diffusive migration, of silver ions because the charging is completed within a shorter time by the greater current. It is considered that the distance or width of said migrative diffusion would be about 1.00 mm. Thus, in accordance with the embodiment just described, by employment of the anode less than 1 mm in thickness including an Ag-Te alloy, graphite and a solid state electrolyte, it is possible to provide electrochemical potential memory device showing a linear change in the output voltage with respect to the supplied quantity of electricity wherein even such a great current as 1 mA per cell only causes an overvoltage less than one fifth of that of FIG. 1 embodiment, for example. This considerable improvement in the potential holding characteristic of such device would apparently be a great contribution to the applications of such device.

A detailed circuit diagram of a preferred embodiment of the timing apparatus in accordance with this invention is illustrated in FIG. 10, wherein some blockes constituting this apparatus are encompassed by dot-dash lines. The embodiment shown in FIG. 10 comprises the timing apparatus 40 that functions to make off-delay control, i.e., delayed turn-on of the load 48, such as electronic equipment energized by the source 49, or to turn off such equipment after a preset period of time. The load 48 is connected to the source 49 through the main source switch SW5 and a manual-automatic switch SW1. When the off-delay control of the load 48 is not desired, in other words, when manual control of energization of the load 48 is desired, switch SW1 may be turned over to the manual contact "MAN," thereby allowing the energization of the load 48 to be controlled by manual opening or closing of the switch SW5 as desired. When automatic off-delay control of the load 48 is desired, switch SW1 may be turned over to the "AUTO" contact. The following is a description of the structure of the timing apparatus 40 and such off-delay control operation thereof.

The timing apparatus 40 of the embodiment shown in FIG. 10 comprises a switching circuit 47 for switching energization of the timing apparatus 40, a charging/discharging circuit 41 for charging or discharging the potential memory device 30, an amplifying circuit 42 for amplifying the terminal potential of the device 30, a reference voltage source 44 for providing the reference voltage to make comparison with the output of the amplifying circuit 42, an indicator circuit 43 for providing visual indication of a time to be preset and also visual analog indication of the passing state of the preset time by comparing the output of the aforementioned amplifying circuit 42 and the reference voltage of the reference voltage source 44, a control circuit 45 for enabling or disabling a load switching circuit 46 after the lapse of a preset time, to be explained later, and power switching circuit 47 for switching control of the load 48.

The embodiment of FIG. 10 utilizes the charging/discharging circuit 41, a potential memory device 30 that employs such auxiliary cathode as described with reference to FIGS. 6, 7, 8 and 9, though this should not be construed by way of limitation. The anode 33 of the device 30 is connected through the resistor 50 to, and the cathode 32 is connected through the resistor 52 to and also through the resistor 53 and the switch SW4 to the positive potential bus +Vcc. The anode 33 is also connected through the discharge contact CD of the charging/discharging switch SW3 and the cathode 32 is also connected through the charge contact CC of the switch SW3 to the negative potential bus -Vcc. The auxiliary cathode 34 is connected to the input electrode of a field effect transistor TR11. The amplifying circuit 42 comprises transistor TR11 and TR12. A high input impedance transistor, preferably a field effect transistor is appropriate for the transistor TR11 for the reason mentioned previously. The reference voltage source 44 comprises a potential divider comprising resistors 57 and 58. A variable resistor 59 and an ammeter 14 are connected in series between the junction E of the output load resistor 55 of the amplifying circuit 42 and the resistor junction F of the reference voltage source 44. The control circuit 45 comprises transistors TR13 and TR14. The switching circuit 46 comprises a switching transistor TR15 which is connected to the load 48 in series and also to the switch SW1 in parallel. The energization switch circuit 47 comprises a transistor TR17 which is connected in series with the positive voltage bus +Vcc and a transistor TR16 which is connected between the input electrode of the transistor TR17 and the negative voltage bus -Vcc, and the transistor TR16 is shunted by the switch SW2 which is provided to start the operation of the timing circuit 40.

FIG. 11 illustrates the relation between the terminal voltage of the device during the charging and discharging operation of the potential memory device 30 used in the embodiment illustrated in FIG. 10 and the charging and discharging operation time. This graph will be referred to in conjunction with the following description of the operation of the timing apparatus.

The following is a description as regards the operation of the timing apparatus 40. The switch SW1 is turned to the "AUTO" contact position so as to place the timing apparatus in the operating state. The switch SW5 is kept as being closed. The timing apparatus is at first so controlled as to drive the device 30 in the charging condition. For this purpose, the starting switch SW2 is at first depressed. The source switching transistor TR17 becomes conductive due to a short circuit formed between the emitter and the collector of the transistor TR16, thereby energizing or supplying the power to the timing apparatus 40. Such energizing state is self-held in an electronic manner in response to the subsequent switching of the switch SW3 over to the contact CC, the detail of which will be described later on. For the purpose of setting to the charging state, the switch SW3 is also depressed to close the charging contact CC. The device 30 is supplied with the current flowing through the resistor 50 in a direction of the anode 33 being positive , in other words, the device 30 is charged. The terminal voltage of the device 30 varies from the point a to the point b along the curve illustrated in FIG. 11 in proportion to the charging quantity of electricity i.sup.. t as supplied to the device 30. The variation of the potential is detected by the cathode 34 for driving the transistors TR11 and TR12, resulting in indication by means of the ammeter 14 of a value that is proportional to such voltage variation. This ammeter is provided with the timing scale to indicate the timing operation of the timing apparatus 40. Accordingly, when the ammeter or the time meter 14 reaches a voltage indication level corresponding to the time T.sub.1 (time required to reach the point c from the point b for discharging) to be preset, depression of the switch SW3 is released to complete the desired charging, or setting of the desired time.

In the circuit of the embodiment, resistance of the resistors 56, 55, 57 and 58 is selected so that the potential difference between the junctions E and F becomes zero volt and so that the needle of the ammeter 14 can indicate zero and thus the transistor TR13 can be turned on, when the voltage of the detecting electrode 34 of the device 30 is 0 (zero). Accordingly, while the starting switch SW2 is depressed with the terminal voltage of the device 30 at OV, transistors TR13 and TR14 remain on and the transistor TR16 remains off. It is thus apparent that the opening of the switch SW2 will turn the transistor TR17 off and discontinue the supply of the source. Once the time-setting switch SW3 is turned to the charge contact CC after the starting switch SW2 is closed, the circuit functions to self-hold the transistor TR17 on, irrespective of the subsequent opening of the switch SW2. More specifically, the potential at the junction E becomes higher than that of the junction F simultaneously with the starting of the charging of the device 30 to cause the needle of the indicator to move by influence of the current flow produced by the potential difference between E and F, and to turn off the transistors TR13 and TR14 in the switching circuit 45 and also to turn on the transistor TR16, and consequently, the transistor TR17 remains on even after the circuit of the starting switch SW2 is opened, and thus power continues to be supplied to the apparatus 40. The transistor TR15 in the load control circuit 46 also remains on at the same time and load 48 continues to be supplied with the power. While the time-setting switch SW3 is kept turned to the charge contact CC after the starting switch SW2 is closed, the device 30 is charged, and the negative potential develops at the detecting auxiliary cathode 34 in proportion to the quantity of electricity passing through the device 30. The said negative potential is fed to the gate of the transistor TR11. As described above, since the potential at the junction E rises in proportion to the terminal voltage of the device 30 as the voltage is amplified by the transistors TR11 and TR12, the needle of the time indicator 14 comprised of an ammeter moves in accordance with the current that flows between the junctions E and F, and accordingly, the charging quantity of electricity can be selected based on the indication of the indicator 14, thereby permitting any desired time setting easily.

It is important in the embodiment of FIG. 10 that the charging operation for the device 30 is completed within a short time. It is to be pointed out that for this purpose the resistor 50 has been selected to be of a negligible value. As the transistor TR13 is subjected to a reverse bias simultaneously with the start of charging the device 30, the transistor TR13, and thus the transistor TR14 are turned off, and accordingly, the transistors TR15 and TR16 are turned on to set out the load 48 in operation. However, as the setting of any desired time by means of depressing the above mentioned switch SW3 is carried out by rapid charging as described above, which is effected within 10 seconds, preferably within a period of 3 to 4 seconds, and therefore, the required time for charging may be negligible as compared with the discharging time of the device 30.

Now, the following is a description of the discharging operation of the device 30, in other words, timing operation of the apparatus 40. Simultaneously with the release of the depression of the switch SW3, the device 30 conducts the current in a direction of the anode 33 being negative through the discharge resistor 52, and the timing operation begins simultaneously with the starting of the discharging operation. Through the discharging process, the potential of the device 30 gradually decreases towards the point c from the point b along the curve illustrated in FIG. 11 along with the decrease of the quantity of electricity (i.sup.. t) stored in the device 30. Accordingly, the needle of the indicator 14 swings from an indication point T.sub.1 to an indication point 0 in proportion to the above-mentioned decrease. In such manner, the needle of the ammeter or of the time indicator 14 moves towards the 0 point of the scale, thereby indicating the passing of time. As soon as the potential of the device 30 detected by the auxiliary cathode 34 reaches OV upon completion of the discharging of the potential memory device 30, the needle of the indicator 14 indicates the completion of the passed time previously set by returning to the 0 point. At that time, the transistor TR13 turns on as a function of the forward bias given by the resistor 56, and accordingly, the transistor TR14 also turns on, so that the transistor TR15 turns off to discontinue the energization of the load 48, and likewise, the transistor TR16 also turns off to turn the transistor TR17 off, and consequently, supply of the electric power to the apparatus 40 is discontinued.

It is thus understood that the discharging time and thus the delay operation time of the apparatus 40 may be determined by a value of the resistor 52. It is desirable that the discharging may be effected at a relatively slow rate so that the device 30 in the apparatus 40 may be rapidly charged in order that the preparation for the timing operation may be quickly completed and also any desired prolonged timing operation may be provided. In such understanding, the resistor 50 of a small value and the resistor 52 of a large value have been selected.

The embodiment illustrated in FIG. 10 further provides an additional means that facilitates resetting of the required timing rapidly within a shorter period than the timing operation time left after the lapse of a given time in the course of passing of a given preset time for the timing operation or for the delaying operation. It is readily understood that such means is often necessary in the practical use of the apparatus. If any change is desired as regards the preset time after the timing once has been set in such manner as described above by the use of the aforementioned switch SW3, or in the course of the timing process, such change may be attained by operating the second operating switch SW4 that is connected to the discharge resistor 52 in parallel through the resistor 53. More specifically, if it is desired to change the preset time to a value T.sub.0 after the lapse of time T' from the start of the timing operation as based on the initially set time T.sub.1, as shown in FIG. 11, such a change is attainable by depressing the rapid discharge switch SW4 to close the circuit of the resistor 53 so as to effect rapid discharging of the device 30 through the parallelled resistors 52 and 53 and transfer the terminal voltage from the point f to point g, and then opening the switch SW4 as soon as the needle of the indicator reaches a point of the scale corresponding to the voltage g. Thereafter, the potential of the device 30 again gradually decreases towards the point h from the point g as affected by normal discharging, and thus, timing operation for the newly set time that has been already changed is effected. It is needless to emphcsize that the aforementioned rapid discharge switch SW4 may also be used to bring back the preset time to the desired time rapidly in case the time has been set in excess of the said desired value.

While specific preferred embodiments of the present invention have been described, it will be apparent that obvious variations and modifications of the invention will occur to those of ordinary skill in the art from a consideration of the foregoing description. It is, therefore, desired that the present invention be limited only by the appended claims.

Claims

What is claimed is:

1. A timing apparatus comprising:

a solid state electrochemical potential memory device comprising:

a main cathode including an active metal,

an auxiliary cathode including an active metal,

an anode comprising an alloy including said metal, and

a solid state electrolyte having high ion conductivity sandwiched between said cathodes and said anode,

said device exhibiting a terminal voltage between said anode and said cathodes linearly changing as a function of the charging or discharging quantity of electricity fed to said device in accordance with the anode being positive or negative, respectively,

means connected to said main cathode for providing a substantially constant current therethrough to said device in a selected direction, thereby selectively charging or discharging said device,

a direct current amplifier having a high impedance input connected to said auxiliary cathode and responsive to the voltage between the anode and auxiliary cathode of said device, and

an output means coupled to said direct current amplifier for providing a timing operation signal, said signal being proportional to the lapse of time of, selectively, the charging or discharging operation of said device.

2. A timing apparatus in accordance with claim 1, in which said current providing means comprises

a means for relatively quickly charging said device in a charging cycle, and

a means for relatively slowly discharging said device in a discharging cycle,

said charging cycle being used for time setting and said discharging cycle being used for the timing operation.

3. A timing apparatus in accordance with claim 2, in which said current providing means further includes means selectively operable for relatively quickly discharging said device in a quick discharge cycle, said quick discharge cycle being used for resetting the time theretofore set in a charging cycle.

4. A timing apparatus in accordance with claim 1, in which said output means comprises an indicator.

5. A timing apparatus in accordance with claim 4, in which said indicator provides visual indication of the voltage of said device as a function of the time.

6. A timing apparatus in accordance with claim 1, in which said direct current amplifier comprises a field effect transistor.

7. A timing apparatus in accordance with claim 1, in which said direct current amplifier comprises a differential amplifier.

8. A timing apparatus in accordance with claim 1, in which the cathode of said device includes Ag and the anode thereof includes an alloy of Ag and a chalcogen element.

9. A timing apparatus in accordance with claim 8, in which the anode of said device includes an Ag-Te alloy.

10. A timing apparatus in accordance with claim 9, in which the anode of said device includes an alloy of Ag and a chalcogen element, graphite and a solid state electrolyte.

11. A timing apparatus in accordance with claim 10, in which said alloy of Ag and a chalcogen element is an Ag-Te alloy.

12. A timing apparatus in accordance with claim 11, in which the anode of said device is less than 1 mm in thickness.