JP2007018927A - Relay controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a relay controller which is prevented from evaporation of moisture of a relay contact even if it is put in a low temperature environment and always assures sufficient contact pressure of the relay contact. <P>SOLUTION: The relay controller comprises a relay drive circuit which supplies drive current to a relay coil 21 which opens and closes relay contacts 22 and 23, a thermistor 7 which detects ambient temperature of the relay. When the thermistor 7 detects a temperature below 0°C or predetermined minus value, the relay drive circuit supplies an average drive current smaller than that at room temperature to the relay coil 21 and the lower temperature it detects, the larger average drive current is supplied to the relay coil 21. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a relay control device including a contact mechanism, and more particularly to a relay control device that controls a drive current of a relay contact so that the relay contact does not malfunction in a low temperature environment below freezing point.

  In a relay device that supplies direct current to the relay coil and keeps the relay contacts closed, the current value should be kept below a certain level so that the relay drive current does not cause excessive heating of the relay coil or thermal damage to the relay coil. Control.

  As a typical device for controlling the current value below a certain value, for example, a relay that detects the coil voltage of a relay coil and performs PWM control of the duty ratio of the relay drive current (pulse current) so that the coil voltage approaches a predetermined voltage There is a control device (Patent Document 1). According to this device, a constant coil voltage can be maintained even when the battery voltage fluctuates, and heat generation of the coil can be suppressed.

In addition, after the relay contact is turned ON, a relay control device that detects a change in the external load (resistance value) and performs PWM control on the duty ratio of the relay drive current (pulse current) based on the detected value. Yes (Patent Document 2). Furthermore, an apparatus for PWM controlling the relay drive current has been proposed from the viewpoint of preventing chattering of the relay contact (Patent Document 3).
JP 2004-178967 A Japanese Patent No. 3465621 JP 2004-95213 A

  Moisture exists in the space inside the container of the relay device, and when this moisture falls below the freezing point (zero degrees Celsius), freezing occurs. Therefore, if an operation is performed in a low-temperature environment by causing a current to flow through the relay coil to cause the relay coil to generate heat and then stop the current again to stop the relay coil from generating heat, the thermal cycle around the relay contact will be below freezing. This thermal cycling can cause moisture evaporation in a low temperature environment, which can result in the formation of larger ice at the relay contacts. In particular, when a relay device is provided on a heat sink having a large heat capacity and high thermal conductivity, such a phenomenon is likely to occur when the relay contact is thermally coupled to the heat sink. The reason is that when the above heat cycle occurs when the heat sink itself is at a negative temperature, the relay contact is cooled relatively rapidly with respect to the surroundings when the current flowing through the relay coil is stopped. This is because the amount of moisture that condenses in the portion increases, and as a result, larger ice is formed. The presence of ice that hinders the movement of the relay contacts naturally leads to malfunction and can cause serious accidents.

  As a device using the above-mentioned relay device with the possibility of freezing, for example, there is an electric power steering device of an automobile. In an electric power steering apparatus, a power module that supplies a large current of several amperes to 100 amperes is used. In such an apparatus, the power module includes a heat sink for cooling, and a control board including a relay apparatus is thermally operated. It is fixed to the heat sink that is coupled to. Therefore, when a vehicle equipped with such an electric power steering device is cold in a cold region, when the driver turns the engine on and off, large ice adheres to the relay contact portion and the relay device is correctly operated. There was a possibility that the engine would not start or could not operate normally.

On the other hand, if the contact pressure of the relay contact is sufficiently large even if ice or foreign matter exists in the relay contact portion, the ice or foreign matter can be destroyed when the contact is closed. Therefore, it can be said that it is desirable to supply the relay coil with a drive current as large as possible without causing heat generation.

  However, since all of the devices shown in Patent Documents 1 to 3 set the relay drive current to a constant value regardless of the ambient temperature, the generation of water vapor and icing around the relay contacts are prevented in a low temperature environment. And ensuring sufficient contact pressure cannot be realized at the same time. In other words, if the relay drive current is reduced to such an extent that moisture does not evaporate at low temperatures, it may be difficult to ensure sufficient contact pressure at room temperature, and relay drive to the extent that sufficient contact pressure can be secured at room temperature. When the current is set, water evaporation occurs at a low temperature, which can generate large ice.

  The present invention provides a relay control device that prevents generation of water vapor at a relay contact portion even when placed in a low temperature environment, and can always ensure a sufficient contact pressure of the relay contact portion. With the goal.

  A relay control device according to the present invention includes a relay drive circuit that supplies a drive current to a relay coil that opens and closes a relay contact, and a temperature sensor that detects the ambient temperature of the relay contact.

  The relay drive circuit makes the average drive current supplied to the relay coil smaller than the average drive current at room temperature when the temperature sensor detects a temperature of zero degrees Celsius or less or a predetermined minus temperature or less.

  By configuring in this way, the relay coil can be prevented from generating heat in a low temperature environment of zero degrees Celsius or less or a predetermined minus temperature or less, so if the average drive current at that time is appropriately reduced, the relay coil It is possible to prevent moisture evaporation due to heat generation. In addition, the relay coil can be driven with a sufficient current without causing a problem of freezing in an environment that exceeds the above-mentioned low temperature such as normal temperature, so that the contact pressure of the relay contact portion can be sufficiently secured.

A relay control device according to the present invention includes a relay drive circuit that supplies a drive current to a relay coil that opens and closes a relay contact;
A temperature sensor for detecting the ambient temperature of the relay contact,
The relay drive circuit makes the average drive current supplied to the relay coil smaller than the average drive current at normal temperature when the temperature sensor detects a temperature of zero degrees Celsius or less or a predetermined minus temperature or less. Set to the current value corresponding to the temperature of.

  With this configuration, it is possible to further prevent the generation of water vapor and ensure the contact pressure of the relay contact portion in a low temperature environment of zero degrees Celsius or less or a predetermined minus temperature or less. That is, if the temperature decreases, the amount of water evaporation relative to the heat generation amount of the relay coil also decreases. Therefore, at a lower temperature (for example, minus 20 degrees), the relay increases while preventing the water evaporation by increasing the average drive current. The contact pressure at the contact portion can be increased. In addition, by increasing the average drive current supplied to the relay coil at a lower temperature, even if small ice or dust adheres to the contact, it can be destroyed, thus increasing the reliability of contact pressure Can do.

  The drive current supplied to the relay coil can be easily controlled by PWM control. The frequency of the drive current at that time is suitably about several KHz to several tens KHz. Since the relay coil is an inductor component, the responsiveness of the relay usually cannot catch up with a frequency of about several KHz to several tens KHz. For this reason, even if the direct current supplied from the battery is subjected to PWM control and converted into a pulsed current, the change in the current does not affect the switching operation of the relay contact. The opening / closing operation and contact pressure of the relay contact are determined by the average value of the drive current that is PWM controlled.

  By applying the relay control device of the present invention to an electric power steering device of an automobile, it is possible to prevent a problem that the relay does not open and close due to icing when the operation of the ignition switch is repeated in a cold region. .

  According to the present invention, it is possible to prevent malfunction of the relay contact due to freezing in a low temperature environment while preventing the contact pressure of the relay contact from decreasing.

  FIG. 1 is a conceptual diagram of a power module of an electric power steering apparatus using a relay apparatus according to an embodiment of the present invention. This power module is installed in the engine room of an automobile that undergoes a temperature change in the range of minus 2 to 30 degrees Celsius to about 50 degrees Celsius, and gives a steering assist force to the steering shaft in that environment. A motor driving current of about several tens of amperes to 100 amperes is supplied to a motor (not shown).

  A relay 2 is attached to an aluminum substrate 3 in the case 1, and a semiconductor switching element 4 such as a power transistor through which the motor driving current flows and other electronic components are mounted on the substrate 3. The substrate 3 is further attached to an aluminum heat sink 5. A thermistor 7 is mounted together with the electronic component 6 on the aluminum substrate 3, and the thermistor 7 detects the ambient temperature of the relay 2. The thermistor 7 may be provided anywhere as long as the ambient temperature of the relay 2 can be detected.

  The relay 2 includes a case 20 and a relay component provided in the case 20, and the relay component includes a relay coil 21, a relay fixed contact 22, and a relay movable contact 23, and is formed on the aluminum substrate 3. A terminal extending from each of the relay coil 21, the relay fixed contact 22, and the relay movable contact 23 is connected to the circuit. The aluminum substrate 3 and the heat sink 5 are electrically insulated or electrically connected at a reference potential, but both are thermally coupled. For this reason, each terminal of the relay 2 is thermally coupled to the heat sink 5, and when the engine is started when the heat sink 5 is cold, even if the entire relay is heated by the current flowing through the relay coil 21, Thereafter, when the ignition switch is turned off, the relay contacts 22 and 23 are rapidly cooled. Since the heat sink 5 is made of aluminum and has a high thermal conductivity, the relay contacts 22 and 23 are rapidly cooled.

  In FIG. 1, ice A adheres to the surface of the relay fixed contact 22. This ice A is formed by condensation of surrounding water, which is frozen below the freezing point. If the ice A has a small hardness and is relatively small, the ice A is broken by the contact pressure when the relay movable contact 22 is moved, so that there is no problem in conduction between the contacts. However, if the ice A is large, the force when the relay movable contact 22 is moved does not break the ice, and malfunctions such as contact between the contacts are not conducted.

  In the relay control device of the present embodiment, even if ice A is formed, the drive current that flows through the relay coil 21 is controlled to an appropriate magnitude so that it does not grow into ice with a large volume. That is, the drive current flowing through the relay coil 21 is PWM controlled so that the temperature of the relay 2 is kept below the freezing point (zero degrees Celsius or less). Also, the magnitude is PWM controlled so as to increase as the temperature decreases.

  FIG. 2 is a circuit configuration diagram of the relay control device.

  The voltage of the battery BT is applied to the relay coil 21 of the relay 2 via the ignition switch SW, and the relay coil 21 is connected to the switching transistor TR. A PWM signal is supplied to the control terminal of the switching transistor TR from the CPU 10 constituting the relay drive circuit, and the transistor TR is driven by the PWM signal.

  The relay fixed contact 22 and the relay movable contact 23 of the relay 2 are connected to output terminals to the battery BT and ECU (Electronic Control Unit), respectively. Further, in the case 1, two thermistors TH1 and TH2 (thermistors 7) are arranged, and are connected in series and connected to the power supply voltage Vcc via a resistor R. The two input thermistors TH1 and TH2 have the same characteristics, and detect the ambient temperature of the relay 2, specifically, the temperature of the aluminum substrate 3. The terminals of the thermistors TH1 and TH2 are connected to the input terminals I1 and I2 of the CPU 10, respectively. Therefore, as long as the thermistors TH1 and TH2 function normally, a voltage of Vcc × (TH1 + TH2) / (R + TH1 + TH2) is input to the input terminal I1 of the CPU 10, and Vcc × (TH2) is input to the input terminal I2. The voltage of / (R + TH1 + TH2) is input. Due to such a configuration, the voltages of the two input terminals I1 and I2 have a substantially constant ratio regardless of the temperature, and if one of the thermistors becomes defective, the ratio of the input voltages greatly changes. Thus, it can be seen that proper temperature detection is not performed. If temperature detection is performed with only one thermistor, it is not immediately known whether the thermistor is abnormal or the temperature is abnormal when the thermistor is in an abnormal state. However, when one of the thermistors becomes an abnormal state by connecting the thermistors doubly as in the present embodiment, this can be easily detected.

  Next, the operation will be described.

  FIG. 3 is a flowchart showing the relay driving procedure of the CPU after the ignition switch SW is turned on.

  In step ST1, temperature detection is performed by the thermistor 7 (thermistors TH1, TH2). In ST2, it is determined whether the detected temperature is less than minus 5 degrees Celsius (below freezing point) or less, and if it exceeds minus 5 degrees (normal temperature, etc.), a current having a duty ratio of 100% is supplied to the relay coil 2 in ST5. To do. If it is lower than minus 5 degrees, the duty ratio of the PWM signal for driving the switching transistor TR is set based on the temperature at that time, and the PWM signal of that duty ratio is supplied to the control terminal of the switching transistor TR in ST4. As a result, the average drive current flowing through the relay coil 2 is in accordance with the PWM signal. FIG. 4 shows a drive current waveform flowing through the relay coil 2. Due to the inductor component of the relay coil 2, the current waveform becomes dull as shown. If the duty ratio of the PWM signal is increased, the average drive current value (Ave) increases, and if the duty ratio is decreased, the average drive current value (Ave) decreases.

  FIG. 5 shows the duty ratio of the drive current (the duty ratio of the PWM signal) so that the relay coil temperature does not exceed zero degrees Celsius.

  In FIG. 5, the vertical axis represents the duty ratio of the PWM signal and the average drive current value of the relay coil, and the horizontal axis represents the temperature detected by the thermistor 7. Further, symbol a indicates a minimum current for guaranteeing the closed state of the relay contact, symbol b indicates a recommended current for guaranteeing the closed state of the relay contact, and symbol c indicates a temperature below minus 5 degrees to minus 20 degrees. The duty ratio of the PWM signal in which the temperature of the relay coil 21 is kept below zero degrees Celsius is shown. Symbol d indicates the average drive current when the duty ratio is the lowest c1 (55%), and symbol e indicates the average drive current when the duty ratio is the highest c2 (95%). The average drive current must be at least the minimum current a or more, and the recommended current b or more is desirable for ensuring a constant contact pressure. The more the recommended current b or more, the more reliable the relay contact is. It can be secured.

  As shown in the figure, the average drive current d is equal to or higher than the minimum current a and in the vicinity of the recommended current b, and the average drive current e greatly exceeds the recommended current b. The average drive current fluctuates between e and d according to the duty ratio of the PWM signal. When the duty ratio increases, it approaches e (increases), and when the duty ratio decreases, it approaches d (decreases).

  Therefore, at minus 5 degrees or less, PWM control of the drive current flowing through the relay coil 21 is performed based on the detected temperature as indicated by symbol c, so that the relay temperature is kept below zero degrees Celsius while ensuring the relay contact is closed. To be guaranteed.

  As shown in FIG. 6, the duty ratio may be fixed to 45% of the sign g at minus 5 degrees or less. In this case, the average drive current is in the range of minus 5 degrees to minus 20 degrees with the sign f. Thus, it becomes about 22 mA.

  However, as in the embodiment shown in FIG. 5, the duty ratio is increased as the temperature is lowered, so that the contact pressure is increased at a lower temperature. Therefore, even if small hard ice or the like adheres to the relay contact, The relay contact can be made reliable by destroying the.

  In the above embodiment, the duty ratio in the range of 0 to minus 5 degrees is set to 100%. However, since the ice is not hard in this range, the duty may be controlled to be close to 100%. That is, the ice formed in the range of 0 to minus 5 degrees can be broken by the contact pressure of the relay contact even if its shape is large. Of course, it is also possible to set the duty ratio so that the relay temperature is maintained below zero degrees Celsius even in this range.

  As another embodiment, in ST2 of FIG. 3, it is determined whether the detected temperature is equal to or lower than 0 degrees Celsius. If the detected temperature is equal to or lower than 0 degrees Celsius, the process proceeds to ST3, and when the detected temperature exceeds 0 degrees Celsius, the process proceeds to ST5. . In this case, in the embodiment of FIG. 5, the control is performed so that the duty ratio is reduced from minus 20 degrees to near zero degrees Celsius, and the duty ratio is 100% at zero degrees Celsius. In the embodiment of FIG. 6, the control is performed so that the duty ratio is 45% from minus 20 degrees to around 0 degrees Celsius, and the duty ratio is 100% at zero degrees Celsius.

  In addition, the temperature determined in ST2 of FIG. 3 may be arbitrary as long as the temperature is equal to or lower than zero degrees Celsius.

The conceptual diagram of the power module of the electric power steering apparatus using the relay apparatus which is embodiment of this invention Circuit diagram of relay control device Flowchart showing the relay drive procedure of the CPU after the ignition switch SW is turned on Coil current waveform diagram The figure which shows the duty ratio and coil current of PWM signal Diagram showing duty ratio of PWM signal and coil current (other examples)

Claims (4)

A relay drive circuit for supplying a drive current to a relay coil for opening and closing the relay contact;
A temperature sensor for detecting the ambient temperature of the relay,
The relay drive circuit is characterized in that when the temperature sensor detects a temperature of zero degrees Celsius or less or a predetermined minus temperature or less, an average drive current supplied to the relay coil is made smaller than an average drive current at normal temperature. Relay control device. A relay drive circuit for supplying a drive current to a relay coil for opening and closing the relay contact;
A temperature sensor for detecting the ambient temperature of the relay,
The relay drive circuit makes the average drive current supplied to the relay coil smaller than the average drive current at normal temperature when the temperature sensor detects a temperature of zero degrees Celsius or less or a predetermined minus temperature or less. The relay control device is characterized in that the current value corresponding to the temperature of the current is set.   3. The relay control according to claim 2, wherein the relay drive circuit increases the average drive current supplied to the relay coil as the temperature below zero degrees Celsius detected by the temperature sensor or below a predetermined minus temperature is lower. apparatus. The relay control device according to claim 1, wherein the relay drive circuit supplies a PWM-controlled drive current to the relay coil.

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