JP2016114224A - Thermostat and thermostat control method - Google Patents

Abstract

An object of the present invention is to improve durability by preventing the lifter from extending beyond the limit due to the forced expansion of the thermal expansion body by the electric heat of the electric heater, and the state where the lifter extends to the limit continuously. A thermostat and a thermostat control method are provided. By energizing the electric heater 20, the thermal expansion body 15 is expanded as the temperature of the thermal expansion body 15 rises due to the electric heat of the electric heater 20, and the lifter 14 is forcibly extended. When operating the one valve body 16 in the opening direction and operating the second valve body 17 in the closing direction, the control device 21 acquires the continuous energization time ta in which the electric heater 20 is energized continuously, and the continuous energization time. When ta exceeds a predetermined stop determination value tx, control is performed to stop energization of the electric heater 20. [Selection] Figure 4

Description

  The present invention relates to a thermostat and a thermostat control method. More specifically, the lifter extends beyond the limit due to the forced expansion of the thermal expansion body due to the electric heat of the electric heater, and the state where the lifter extends to the limit is continuous. The present invention relates to a thermostat and a thermostat control method for improving durability by avoiding continuous operation.

  In a cooling circuit for an internal combustion engine in which a thermostat is disposed at a branch point between a cooling passage for introducing cooling water for cooling the internal combustion engine to the radiator and a bypass passage not passing through the radiator, when the temperature of the cooling water is low, The cooling passage is shut off by the thermostat and the bypass passage is opened to warm up the cooling water by raising the temperature of the cooling water without passing the radiator through the radiator. On the other hand, when the temperature of the cooling water is high, the cooling passage is opened by the thermostat and the bypass passage is blocked, and the cooling water is cooled by passing the radiator through the cooling water.

  Thus, as a thermostat arranged at a branch point of a plurality of passages and switching fluid flow paths, a lifter whose one end side is fixed and the other end side is expanded and contracted by a thermal expansion body, along with the expansion and contraction operation of the lifter There has been proposed a thermostat configured to include a first valve body and a second valve body that open and close, and an electric heater that warms a thermal expansion body (see, for example, Patent Document 1).

  This thermostat forcibly operates the first valve body and the second valve body regardless of the temperature of the fluid by warming and expanding the thermal expansion body with an electric heater. Specifically, when the temperature of the cooling water flowing through the cooling circuit exceeds a preset target water temperature, energize the electric heater to heat and expand the thermal expansion body by electric heating, and forcibly extend the lifter. The first valve body is opened and the second valve body is closed to open the cooling passage and shut off the bypass passage.

  However, this type of thermostat does not have a means for grasping the amount of lifter lift. Therefore, the durability is reduced by the lifter extending beyond the limit due to the forced expansion of the thermal expansion body due to the electric heat of the electric heater, or the lifter is extended for a long time. It was.

  In other words, if the cooling capacity of the cooling water is reduced due to an unexpected outside air temperature, radiator deterioration, or cooling fan failure, the lifter's extension amount is set to bring the cooling water temperature close to the target water temperature. Even in the limit state, the electric heater continues to be energized. As a result, as described above, the lifter extends beyond the limit due to the forced expansion of the thermal expansion body due to the electric heat of the electric heater, or the lifter may extend for a long time. Durability was reduced.

Japanese Patent Laid-Open No. 55-15579

The present invention has been made in view of the above problems, and the problem is that the lifter extends beyond the limit and the lifter extends to the limit due to the forced expansion of the thermal expansion body by the electric heat of the electric heater. It is to provide a thermostat and a thermostat control method that can improve durability by avoiding continuous state.

  The thermostat of the present invention for solving the above-described problems is a heat that is arranged at a branch of a plurality of passages, has one end side fixed, and the other end side expands as the temperature rises and contracts as the temperature decreases. A lifter that expands and contracts by an expansion body, a first valve body and a second valve body that open and close in accordance with the expansion and contraction operation of the lifter, and a first elastic body that biases the first valve body in a direction in which the lifter contracts A thermostat comprising: a second elastic body that urges the second valve body in a direction in which the lifter extends; an electric heater that warms the thermal expansion body; and a control device that controls the electric heater. The control device energizes the electric heater, extends the lifter by the expansion of the thermal expansion body due to electric heat, and controls the first valve body in the opening direction and the second valve body in the closing direction. When performing the electric heating A continuous energization time during which power is continuously supplied is acquired, and when the continuous energization time exceeds a predetermined stop determination value, control is performed to stop energization of the electric heater. Is.

  Further, the thermostat control method of the present invention for solving the above-mentioned problem is that the electric valve is energized, the thermal expansion body is expanded by electric heating, the lifter is extended by the expansion of the thermal expansion body, and the first valve In the thermostat control method in which the body is operated in the opening direction and the second valve body is operated in the closing direction, when the electric heater is energized, the continuous energization time in which the electric heater is energized is acquired. In the method, the energization of the electric heater is stopped when the continuous energization time exceeds a predetermined stop determination value.

  According to the thermostat and the thermostat control method of the present invention, in order to open one of the passages, when the electric heater is energized and the thermal expansion body is forcibly expanded by electric heating to extend the lifter, the electric heater is continuously connected. Thus, the energization of the electric heater is stopped by setting a limit on the continuous energization time. And since the influence of the electric heating by the electric heater is eliminated, the state in which the amount of elongation of the lifter is limited can be once released by contracting the thermal expansion body and contracting the lifter. Thereby, it is possible to prevent the lifter from extending beyond the limit due to the forced expansion of the thermal expansion body, and it is possible to avoid the state where the lifter is extended for a long time, thereby improving the durability.

  In particular, the present invention is effective for a long time even when the cooling water temperature of the cooling circuit of the internal combustion engine does not decrease to the target water temperature when the cooling capacity is reduced due to the influence of the outside air temperature, the deterioration of the radiator, and the cooling fan failure. Since it can be avoided that the electric heater is continuously energized over a period of time, it is effective to be provided in the cooling circuit of the internal combustion engine.

It is explanatory drawing which illustrates embodiment of the thermostat of this invention, and shows the state which the 1st valve body closed and the 2nd valve body opened. It is explanatory drawing which illustrates embodiment of the thermostat of this invention, and shows the state which the 1st valve body opened and the 2nd valve body closed. The state which the lifter of the thermostat shown in FIG. 2 extended is shown. It is a flowchart which illustrates the control method of the thermostat of this invention. It is explanatory drawing which illustrates the internal combustion engine which has arrange | positioned the thermostat shown in FIGS. 1-3 in a cooling circuit, and shows the state which interrupted | blocked the cooling channel | path of the cooling circuit and opened the bypass channel. It is explanatory drawing which illustrates the internal combustion engine which has arrange | positioned the thermostat shown in FIGS. 1-3 in a cooling circuit, and shows the state which opened the cooling channel | path of the cooling circuit and opened the bypass channel. 6 is a part of a flowchart illustrating a thermostat control method when arranged in a cooling circuit of an internal combustion engine.

  Hereinafter, the thermostat and the control method of the thermostat of the present invention will be described.

  1 to 3 illustrate the configuration of a thermostat 10 according to an embodiment of the present invention. The thermostat 10 energizes the electric heater 20 to expand the thermal expansion body 15 as the temperature of the thermal expansion body 15 rises due to the electric heat of the electric heater 20, and forcibly causes the first valve body 16 to move. The second valve element 17 is operated in the closing direction while being operated in the opening direction.

  As shown in FIG. 1, a thermostat 10 disposed at a branch point of a plurality of passages 36 a to 36 c includes a housing 11, a lifter 14 including a cylinder 12 and a piston 13, a thermal expansion body 15, a first valve body 16, A second valve body 17, a first elastic body 18, a second elastic body 19, an electric heater 20, and a control device 21 are provided.

  The casing 11 is fixed to the passage 36b, and includes an upper frame 11a disposed above, a lower frame 11b disposed below, and a connecting portion disposed on the outer peripheral side and coupled to the passage 36b. 11c and a valve seat 11d disposed on the inner peripheral edge. The upper frame 11a and the lower frame 11b of the housing 11 are provided with a plurality of through holes and formed in a bowl shape. Further, the connecting portion 11c and the passage 36b are connected while maintaining liquid tightness.

  The lifter 14 is fixed to the housing 11 at one end and filled with a thermal expansion body 15 at the other end, and is expanded and contracted by the thermal expansion body 15. The lifter 14 includes a cylinder 12 and a piston 13.

  The cylinder 12 is a bottomed cylindrical hollow container having an open end 12 a disposed inside the housing 11 and a closed end 12 b projecting outward from the housing, and is filled with a thermal expansion body 15.

  The piston 13 has an outer end 13 a protruding from the opening end 12 a of the cylinder 12 fixed to the inner surface of the upper frame 11 a of the housing 11, and an inner end 13 b embedded in the thermal expansion body 15 inside the cylinder 12. ing. The piston 13 is a hollow tube.

  The thermal expansion body 15 is filled in the cylinder 12. The thermal expansion body 15 has the property of melting and volume expansion as the temperature rises, while solidifying and volume shrinking as the temperature decreases. In addition, as this thermal expansion body 15, a thermo wax can be illustrated.

  The first valve body 16 is disposed inside the housing 11 and is fixed to the opening end side of the cylinder 12. The first valve body 16 is in contact with the valve seat 11d of the housing 11 to block the passage 36b, while being separated from the valve seat 11d, the passage 36b is opened.

  The second valve body 17 is supported so as to be slidable along a shaft portion 17 a protruding from the closed end 12 b of the cylinder 12 to the opposite side of the piston 13. The second valve body 17 is in contact with the passage 36c to block the passage 36c and is separated from the passage 36c to open the passage 36c.

  The first elastic body 18 is interposed between the housing 11 and the first valve body 16, the upper end is fixed to the first valve body 16, and the lower end is fixed to the lower frame 11 b of the housing 11. . The first elastic body 18 biases the first valve body 16 in the closing direction when the first valve body 16 moves in the opening direction.

  The second elastic body 19 is interposed between the cylinder 12 and the second valve body 17, and has an upper end fixed to the closed end 12 b of the cylinder 12 and a lower end fixed to the second valve body 17. The second elastic body 19 urges the cylinder 12 upward when the second valve body 17 is pressed against the passage 36c.

  The electric heater 20 is disposed in the hollow portion on the inner end side of the piston 13 and is connected to the control device 21 by electric wiring. The electric heater 20 may be provided inside the cylinder 12 instead of inside the piston 13, but the inside of the piston 13 is preferable because the position is fixed.

  As shown in FIG. 1, when the water temperature Ta of the cooling water W is lower than the melting temperature of the thermal expansion body 15, the first valve body 16 comes into contact with the valve seat 11d, blocks the passage 36b, and the second The valve body 17 is separated from the passage 36c and opens the passage 36c. As a result, the cooling water W is introduced from the passage 36a into the passage 36c.

  As shown in FIG. 2, when the water temperature Ta of the cooling water W is higher than the melting temperature of the thermal expansion body 15, the lifter 14 extends due to the expansion of the thermal expansion body 15, that is, the piston 13 due to the expansion of the thermal expansion body 15. Is pushed out from the cylinder 12 in the axial direction, and the cylinder 12 moves downward with respect to the piston 13. By the downward movement of the cylinder 12, the first valve body 16 is separated from the valve seat 11d, the passage 36b is opened, the second valve body 17 abuts on the passage 36c, and the passage 36c is blocked. Thus, the cooling water W is introduced from the passage 36a to the passage 36b.

  In the state shown in FIG. 2, when the water temperature Ta of the cooling water W becomes lower than the melting temperature of the thermal expansion body 15, the lifter 14 contracts due to the contraction of the thermal expansion body 15, that is, the thermal expansion body 15 contracts. Accordingly, the urging force from the first elastic body 18 acting on the first valve body 16 becomes larger than the force pushing the piston 13, and the cylinder 12 moves upward with respect to the piston 13 while pushing the piston 13 into the cylinder 12. Move to. By the upward movement of the cylinder 12, the first valve body 16 contacts the valve seat 11d, the passage 36b is blocked, the second valve body 17 is separated from the passage 36c, and the passage 36c is opened.

  When the water temperature Ta further rises from the state of FIG. 2, the thermal expansion body 15 further expands and the cylinder 12 moves downward as shown in FIG. At this time, as the second valve body 17 slides upward on the shaft portion 17a, the urging force F2 acts on the cylinder 12 from the second elastic body 19 in the direction in which the lifter 14 contracts, and thermal expansion occurs. It tries to absorb the expansion force F1 of the body 15. The position of the closed end 12b of the cylinder 12 in FIG. 2, that is, the closed end 12b when the second valve body 17 blocks the passage 36c in a state where the expansion force F1 and the urging force F2 of the thermal expansion body 15 are balanced. The difference between the position and the position of the closed end 12b when the water temperature Ta further rises is denoted by Δd. This difference Δd becomes the maximum value of the extension amount of the lifter 14 after the second valve body 17 blocks the passage 36c.

  In the thermostat 10, the control device 21 energizes the electric heater 20, and the thermal expansion body is heated and expanded by the electric heat of the electric heater 20, so that the first valve body is forcibly independent of the water temperature Ta of the cooling water W. And the second valve body is actuated.

  However, the thermostat 10 is not provided with means for grasping the amount of extension of the lifter 14. Therefore, the lifter 14 extends beyond the limit due to the forced expansion of the thermal expansion body 15 due to the electric heating of the electric heater 20 (the difference Δd is exceeded), or the state where the lifter 14 is extended continues for a long time. May occur.

Therefore, in the thermostat 10 of the present invention, when the control device 21 acquires the continuous energization time ta in which the electric heater 20 is energized continuously, and the continuous energization time ta exceeds a predetermined stop determination value tx. The electric heater 20 is configured to perform control to stop energization.

  The control device 21 can be exemplified by a microcomputer that performs control to energize the electric heater 20 from the power device 22 when the flow path of the cooling water W is changed from the passage 36a to the passage 36b. The control device 21 is connected to the power device 22 and the power sensor 23 and has a timer 24 that counts the continuous energization time ta.

  The continuous energization time ta is a time during which the electric heater 20 is continuously energized, that is, a time when electric power is supplied to the electric heater 20 according to a command from the control device 21 and the electric heater 20 continues to generate heat. Specifically, the time when the power sensor 23 that detects the current value or voltage value between the electric heater 20 and the power device 22 detects a predetermined value is the start time, and the time counted by the timer 24 of the control device 21 It is. Although the time when the predetermined value is detected by the power sensor 23 is set as the start time, a command signal for starting energization transmitted from the control device 21 to the power device 22 may be set as the start time.

  The stop determination value tx is set according to the filling amount of the thermal expansion body 15 based on the size of the cylinder 12 of the lifter 14 and the size of the heat capacity based on the properties of the thermal expansion body 15. For example, as the filling amount of the cylinder 12 is large and the heat capacity is large, the speed of expansion due to the electric heat of the electric heater 20 becomes gentler with time, so the stop determination value tx is set longer, and the smaller the filling amount is, the smaller the heat capacity is. The speed at which the electric heater 20 expands due to electric heat increases with time, so the stop determination value tx is set short. It may be set based on the spring constant of the second elastic body.

  This stop determination value tx is the second elastic body that acts on the expansion force F1 of the thermal expansion body 15 and the lifter 14 after the second valve body 17 is closed at least after the electric heater 20 is energized. 19 is set to a time until the urging force F2 in the direction in which the lifter 14 contracts is balanced, that is, counting is performed after the electric heater 20 is energized, and then the second valve body 17 is closed, and thereafter It is desirable to set the time until the lifter 14 is extended by the difference Δd.

  The state shown in FIG. 3 is a state in which the expansion force F1 of the thermal expansion body 15 and the biasing force F2 of the second elastic body 19 are balanced. By setting the stop determination value tx so that the lift amount of the lifter 14 is maximized in this state, the second valve body 17 can surely block the passage 36c within the continuous energization time ta. If the stop determination value tx is set to a time shorter than this, the initial purpose of introducing the cooling water W into the passage 36b without the second valve body 17 being able to block the passage 36c within the continuous energization time ta is achieved. Can not. When the stop determination value tx is set to a longer time, the expansion force F1 of the thermal expansion body 15 is larger than the urging force F2 of the second elastic body 19 and the lifter 14 extends beyond the limit (difference Δd Or the lifted state of the lifter 14 cannot be avoided for a long time.

  Therefore, it is preferable to obtain a time in which the expansion force F1 of the thermal expansion body 15 and the urging force F2 of the second elastic body 19 are balanced by experiments and tests, and to set the time as the stop determination value tx.

  The operation of the thermostat 10 will be described. In the thermostat 10, when the cooling water W introduced from the passage 36a to the passage 36c is introduced from the passage 36a to the passage 36b, the control device 21 first energizes the electric heater 20 and is thermally expanded by electric heat. 15 is inflated. Next, by the expansion of the thermal expansion body 15, the lifter 14 filled with the thermal expansion body 15 is extended, the first valve body 16 is operated in the opening direction, and the second valve body 17 is operated in the closing direction.

  Next, the control device 21 acquires a continuous energization time ta in which the electric heater 20 is energized continuously by the timer 24, with the time when the electric heater 20 is energized as a start time. Next, the control device 21 stops energization of the electric heater 20 when the continuous energization time ta exceeds a predetermined stop determination value tx.

  According to the thermostat 10 described above, when the electric heater 20 is energized to open the one passage 36b and the thermal expansion body 15 is forcibly expanded by electric heat to extend the lifter 14, the electric heater 20 is continuously connected. By providing a limit to the continuous energization time ta that is energized, the energization of the electric heater 20 is stopped when the continuous energization time ta exceeds the limit. And since the influence of the electric heat by the electric heater 20 is eliminated, the state in which the extension amount of the lifter 14 is limited can be once released by contracting the thermal expansion body 15 and contracting the lifter 14. As a result, it is possible to prevent the lifter 14 from extending beyond the limit due to the forced expansion of the thermal expansion body 15 and the extended state of the lifter 14 from being continued for a long time. It can be improved.

  Further, in the thermostat 10 described above, the control device 21 stops the energization of the electric heater 20 after performing the control to stop the energization of the electric heater 20 when the continuous energization time ta exceeds the stop determination value tx. It is desirable that the continuous stop time tb is acquired, and the control to start energization of the electric heater 20 is performed when the continuous stop time tb exceeds a predetermined start determination value ty.

  The continuous stop time tb is a time during which the electric heater 20 is continuously stopped. Specifically, it is the time counted by the timer 24 of the control device 21 when the power sensor 23 between the electric heater 20 and the power device 22 can no longer detect a predetermined value. Although the time when the predetermined value cannot be detected by the power sensor 23 is set as the start time, a command signal for stopping energization transmitted from the control device 21 to the power device 22 may be set as the start time.

  The start determination value ty is set in accordance with the filling amount of the thermal expansion body 15 and the heat capacity of the thermal expansion body 15 in the same manner as the stop determination value tx, but the elongation amount of the lifter 14 has reached a limit. May be set to a time that can be canceled once, and is preferably set to a time shorter than the stop determination value tx.

  When energizing the electric heater 20 and forcibly expanding the thermal expansion body 15 by electric heat to extend the lifter 14, the purpose is to change the flow path of the cooling water W from the passage 36c to the passage 36b. Therefore, after stopping energization of the electric heater 20 in order to improve durability, when the continuous stop time tb is acquired and the continuous stop time tb exceeds the start determination value ty, the electric heater 20 is supplied again. By starting energization, the original purpose can be achieved.

  A control method of the thermostat 10 will be described with reference to the flowchart of FIG. The control method of the thermostat 10 is a method performed when the cooling water W introduced from the passage 36a to the passage 36c is introduced from the passage 36a to the passage 36b. The continuous energization time ta and the continuous stop time tb are added every predetermined time Δt. Examples of the predetermined time Δt include 1 second and 10 seconds.

  First, in step S <b> 10, the electric heater 20 is energized according to a command from the control device 21. Next, in step S20, the timer 24 counts that the predetermined time Δt has elapsed as the continuous energization time ta.

Next, in step S30, the control device 21 determines whether or not the continuous energization time ta has exceeded the stop determination value tx. If it is determined in step S30 that the continuous energization time ta is equal to or less than the stop determination value tx, the process returns to step S10. On the other hand, if it is determined in step S30 that the continuous energization time ta has exceeded the stop determination value tx, the process proceeds to step S40.

  Next, in step S40, the continuous energization time ta counted by the timer 24 is reset.

  Next, in step S50, the control device 21 stops energization of the electric heater 20. Next, in step S60, the timer 24 counts that the predetermined time Δt has elapsed as the continuous stop time tb.

  Next, in step S70, the control device 21 determines whether or not the continuous stop time tb exceeds the start determination value ty. If it is determined in step S70 that the continuous stop time tb is equal to or less than the start determination value ty, the process returns to step S50. On the other hand, if it is determined in step S70 that the continuous stop time tb has exceeded the start determination value ty, the process proceeds to step S80.

  In step S80, the continuous stop time tb counted by the timer 24 is reset, the process returns to the start, and energization of the electric heater 20 is resumed.

  According to this control method, when the electric heater 20 is energized and the thermal expansion body 15 is forcibly expanded by electric heating and the lifter 14 is extended, the continuous energization time ta continuously energized to the electric heater 20 is limited. By providing, the energization of the electric heater 20 is stopped. Then, once the lift amount of the lifter 14 is released from the limit, the energization of the electric heater 20 is resumed. Thereby, the flow path of the cooling water W which is the initial purpose of energizing the electric heater 20 while avoiding the lifter 14 extending beyond the limit and the state where the lifter 14 is extended for a long time is avoided. Can be switched.

  FIG. 5 illustrates a cooling circuit 36 of the engine 30 in which the thermostat 10 is provided. In the engine 30, the air A taken into the intake passage 31 when the vehicle is running is compressed by a turbocharger compressor (not shown) and becomes high temperature, and is cooled by an intercooler (not shown). After that, the intake air is supplied to the engine body 33 through the intake manifold 32. The intake air supplied to the engine body 33 is mixed with fuel and combusted to generate heat energy, and then becomes combustion gas, exhausted from the exhaust manifold 34 to the exhaust passage 35, and then exhausted G to the atmosphere. Released into.

  Further, the cooling circuit 36 for cooling the engine body 33 is of a bottom bypass type, and the cooling water W discharged from the engine body 33 is cooled by the thermostat 10 through the inlet passage 36a by the cooling passage 36b or the bypass passage. It branches to 36 c and returns to the engine body 33 from the outlet passage 36 d via the pump 37.

  When the water temperature Ta is low, the cooling water W discharged from the engine body 33 is introduced into the bypass passage 36c by the thermostat 10 as shown in FIG. On the other hand, when the water temperature Ta is high, as shown in FIG. 6, it is introduced into the cooling passage 36b by the thermostat 10 and passes through the radiator 38, so that the vehicle speed wind and the cooling air by the subsequent cooling fan 39 are used. And cooled.

  The control device 21 of the thermostat 10 is integrated with an ECM 40 that controls the engine body 33. Note that the control device 21 may not be integrated into the ECM 40.

  In addition to the power sensor 23, the ECM 40 includes a water temperature sensor 41 for acquiring the water temperature Ta of the cooling water W, an engine speed sensor 42 for acquiring the engine speed Na, and an intake air amount sucked into the cylinder of the engine body 33. An intake air amount sensor 43 for acquiring Qa and an accelerator opening degree sensor 44 for acquiring an accelerator pedal depression amount by the driver, that is, an accelerator opening degree Ac, are connected.

  In this engine 30, when the ECM 40 calculates the target water temperature Tz set based on the heat quantity of the engine 30 and the water temperature Ta acquired by the water temperature sensor 41 exceeds the target water temperature Tz, the thermostat 10. The energization control to the electric heater 20 incorporated in the heater is performed, and the thermal expansion body 15 is forcibly expanded to control the cooling water W to be introduced into the cooling passage 36b.

  The target water temperature Tz is a target value of the water temperature Ta set based on the amount of heat of the engine 30. This target water temperature Tz has a target water temperature map for calculating.

The target water temperature map includes an engine speed Na acquired by the engine speed sensor 42, and
The target water temperature Tz based on the load La of the engine 30 obtained from the intake air amount Qa acquired by the intake air amount sensor 43 and the fuel injection amount Qb calculated from the accelerator opening amount Ac acquired by the accelerator opening amount sensor 44. Is a preset map. Instead of the target water temperature map, a map in which the target water temperature Tz is set based on the supplied heat capacity Ca obtained from the fuel injection amount Qb and the engine speed Na may be used.

  The ECM 40 obtains the detection value of each sensor and calculates the target water temperature Tz by referring to the detection value and the target water temperature map.

  When the water temperature Ta acquired by the water temperature sensor 41 is higher than the target water temperature Tz calculated in this way, the ECM 40 performs energization control to the electric heater 20 built in the thermostat 10. Even if the cooling capacity of the cooling water W is reduced due to the influence of the outside air temperature, the deterioration of the radiator 38, and the cooling fan 39, the amount of extension of the lifter 14 is reduced in order to keep the water temperature Ta below the target water temperature Tz. Even in the limit state, the electric heater 20 continues to be energized.

  Therefore, as described above, the thermostat 10 of the present invention continuously energizes the electric heater 20 when the electric heater 20 is energized and the thermal expansion body 15 is forcibly expanded by electric heat and the lifter 14 is extended. By restricting the energization time ta, the energization of the electric heater 20 is resumed after the energization of the electric heater 20 is stopped and the lift amount of the lifter 14 is once released from the limit state.

  A control method of the thermostat 10 provided in the cooling circuit 36 of the engine 30 will be described with reference to the flowchart of FIG. In this control method, step S10 shown in FIG. 4, that is, before the electric heater 20 is energized, steps S100 to S140 shown in FIG. 7 are performed to determine whether or not the electric heater 20 is energized. After step S150, step S160 and step S160 are performed to confirm energization of the electric heater 20. In addition, when the condition is not satisfied (NO) in step S30 shown in FIG. 4, the process returns to step S100, and the continuous energization time ta is reset while the electric heater 20 is energized.

As shown in FIG. 7, first, in step S100, the ECM 40 acquires detection values of the sensors (water temperature sensor 41, engine speed sensor 42, intake air amount sensor 43, accelerator opening sensor 44). Next, in step S110, the ECM 40 refers to the target water temperature map based on each detection value acquired in step S100. Next, in step S120, the ECM 40 calculates the target water temperature Tz from the target water temperature map.

  Next, in step S130, the ECM 40 determines whether or not the water temperature Ta has exceeded the target water temperature Tz. If it is determined in step S130 that the water temperature Ta is equal to or lower than the target water temperature Tz, the process proceeds to step S140. On the other hand, if it is determined in step S130 that the water temperature Ta has exceeded the target water temperature Tz, the process proceeds to step S10 shown in FIG.

  Next, in step S140, the continuous energization time ta counted by the timer 24 is reset, that is, the continuous energization time ta is set to an initial value of zero. Then, the process returns to step S100. If it is determined in step S130 that the water temperature Ta is equal to or lower than the target water temperature Tz, the lifter 14 of the thermostat 10 is not full lift, that is, the amount of extension of the lifter 14 is not a limit, or the middle stage of the control, that is, the second valve It can be determined that the body 17 is not blocking the bypass passage 36c. In this case, in step S140, the continuous energization time ta counted by the timer 24 is reset and the continuous energization time ta is set to zero, so that the lifter 14 is not in full lift or is in the middle of control. Stopping energization of the electric heater 20 can be avoided.

  Next, in step S150 after step S10, the control device 21 acquires the detection value of the power sensor 23. Next, in step S160, it is determined whether or not the electric heater 20 is energized based on the detected value of the power sensor 23. In step S160, it is determined whether or not the detection value of the power sensor 23 is equal to or greater than a predetermined value. For example, when the power sensor 23 uses the voltage value V1 from the power device 22 to the electric heater 20 as a detection value, it is determined whether or not the voltage value V1 is equal to or greater than the vehicle voltage value V2 (for example, 12V or 24V). To do. If it is determined in step S160 that the electric heater 20 is not energized, the process returns to step S10 again. On the other hand, if it is determined in step S160 that the electric heater 20 is energized, the process proceeds to step S20 in FIG.

  After step S20, when it is determined in step S30 that the continuous energization time ta is equal to or less than the stop determination value tx, the process is the same as shown in FIG. 4 except that the process returns to step S100.

  Thus, according to the thermostat 10 and the control method of the thermostat 10 of the present invention, when the cooling capacity of the cooling passage 36b is reduced due to the influence of the outside air temperature, the deterioration of the radiator 38, and the cooling fan 39, the engine 30 is reduced. Even when the water temperature Ta of the cooling water W flowing through the cooling circuit 36 does not decrease to the target water temperature Tz, the electric heater 20 can be prevented from being energized continuously for a long time, so that the lifter 14 extends beyond the limit. In addition, the durability can be improved by avoiding the extended state of the lifter 14 and extending the lifter 14 for a long time, and the water temperature Ta of the cooling water W that is the initial purpose of energizing the electric heater 20 is set to the target water temperature Tz. Therefore, the lifter 14 is forcibly lifted in order to meet the above conditions, and the flow path of the cooling water W can be switched to the cooling passage 36b. There can be avoided falling into insufficient cooling.

  In the above-described embodiment, the thermostat 10 and the passage are described as an example, but the thermostat 10 and the passage may be integrally formed. Further, each part of the thermostat 10 is preferably made of metal, but may be made of resin.

  Moreover, although the example which used thermowax as the thermal expansion body 15 of the thermostat 10 was demonstrated, this invention is applicable also to what used the bimetal as a thermal expansion body.

In the above embodiment, the bottom bypass type cooling circuit 36 has been described as an example. However, the thermostat 10 of the present invention can also be applied to an inline type cooling circuit. In addition, the cooling circuit 36
The configuration is not limited to the above configuration. For example, the cooling circuit 36 may be provided with two cooling circuits, a main cooling circuit and a sub cooling circuit. Further, the intercooler may be cooled by supplying the cooling water W of the cooling circuit 36 to the water-cooled intercooler.

DESCRIPTION OF SYMBOLS 10 Thermostat 14 Lifter 15 Thermal expansion body 16 1st valve body 17 2nd valve body 18 1st elastic body 19 2nd elastic body 20 Electric heater 21 Control apparatus ta Continuous energization time tb Continuous stop time tx Stop determination value ty Start determination value

Claims (6)

Arranged at the branch of multiple passages,
A lifter that expands and contracts by a thermal expansion body having a property that one end is fixed and the other end expands as the temperature rises and contracts as the temperature decreases, and a first valve that opens and closes as the lifter expands and contracts A first elastic body that biases the first valve body in a direction in which the lifter contracts, a second elastic body that biases the second valve body in a direction in which the lifter extends, In a thermostat provided with an electric heater for heating the thermal expansion body, and a control device for controlling the electric heater,
Control in which the control device energizes the electric heater, extends the lifter by expansion of the thermal expansion body by electric heating, and operates the first valve body in the opening direction and the second valve body in the closing direction, respectively. When doing
The configuration is such that the continuous energization time during which the electric heater is energized continuously is acquired, and control is performed to stop energization of the electric heater when the continuous energization time exceeds a predetermined stop determination value. Characteristic thermostat.   After the continuous energization time exceeds the stop determination value and the control device performs control to stop energization of the electric heater, the control device acquires the continuous stop time when the energization to the electric heater is stopped, and the continuous The thermostat according to claim 1, wherein the thermostat is controlled to start energization of the electric heater when the stop time exceeds a predetermined start determination value.   After the energization of at least the electric heater is started and the second valve body is closed, the stop determination value is determined by the expansion force of the thermal expansion body and the second elastic body acting on the lifter. The thermostat according to claim 1 or 2, wherein the thermostat is set to a time until the urging force in a direction in which the lifter contracts is balanced. The inlet passage through which the cooling water after heat exchange with the internal combustion engine passes, the cooling passage through which the radiator passes through the cooling water, and the bypass passage where the cooling water does not pass through the radiator are arranged at the branching point,
When the water temperature of the cooling water flowing through the inlet passage becomes equal to or lower than a target water temperature set based on the amount of heat of the internal combustion engine,
The control device energizes the electric heater, extends the lifter by expansion of the thermal expansion body due to electric heat, operates the first valve body in an opening direction to open the cooling passage, and the second The thermostat according to any one of claims 1 to 3, wherein the valve body is operated in a closing direction to block the bypass passage.   When the control device has acquired the continuous energization time and the temperature of the cooling water flowing through the inlet passage becomes equal to or lower than the target water temperature, the control device performs control to return the continuous energization time to an initial value. The thermostat according to claim 4. Energize the electric heater, expand the thermal expansion body by electric heat,
In the thermostat control method of extending the lifter by the expansion of the thermal expansion body and operating the first valve body in the opening direction and operating the second valve body in the closing direction,
When energizing the electric heater, obtain the continuous energization time of energizing the electric heater continuously,
A thermostat control method, wherein energization of the electric heater is stopped when the continuous energization time exceeds a predetermined stop determination value.

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