JP5665674B2 - Engine cooling system and control device - Google Patents

Description

  The present invention relates to an engine cooling system including a switching valve and a switching valve control device.

  2. Description of the Related Art Conventionally, an engine cooling system including a cooling water passage, a water pump for circulating cooling water in the cooling water passage, and a radiator for cooling cooling water circulating in the cooling water passage is known (for example, Patent Document 1).

  Patent Document 1 discloses a first flow path that connects an engine outlet and a radiator, a second flow path that connects a radiator and an inlet of cooling water to the engine, a first flow path that bypasses the radiator, and A vehicle cooling device is disclosed that includes a cooling circuit (cooling water passage) having a bypass path connecting the second flow path. A thermostat (switching valve) is provided at a connection point between the bypass path and the second flow path in the cooling circuit. This thermostat includes a thermo element that expands and contracts according to temperature, and the opening and closing of the valve is controlled by the expansion and contraction of the thermo element.

  And in the vehicle cooling device of patent document 1, the cooling water which flows into an engine (inlet port) is distributed by the thermostat by distributing the flow volume of the cooling water flowing from the radiator and the cooling water flowing around the radiator. It is configured to maintain the temperature within a predetermined range.

  Here, the thermostat is provided with a heater that heats the thermoelement, and the opening and closing of the thermostat is controlled by the ECU supplying power to the heater. Specifically, the ECU estimates the temperature of the thermo element based on the engine outlet water temperature, the radiator outlet water temperature, and the ambient temperature of the thermostat, and determines the amount of electric power supplied to the heater based on the estimated temperature of the thermo element. By doing so, the thermostat is controlled so that the temperature of the cooling water introduced into the engine becomes a target value.

JP 2005-188327 A

  However, in the conventional vehicle cooling device disclosed in Patent Document 1, the temperature of the thermo element is estimated based on the engine outlet water temperature, the radiator outlet water temperature, and the ambient temperature of the thermostat, but the characteristics of the thermo element are taken into consideration. In addition, there is a problem that it is difficult to estimate the temperature of the thermo element with high accuracy.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an engine cooling system and a control device capable of estimating the temperature of the thermo wax with high accuracy. is there.

  An engine cooling system according to the present invention includes a cooling water passage, a switching valve that is provided in the cooling water passage and includes a thermo wax and a heating unit that heats the thermo wax, and a control device that controls opening and closing of the switching valve. . The control device estimates the temperature of the thermowax by setting a different time constant according to at least one of the on / off state of energization to the heating unit and the temperature of the cooling water around the thermowax. It is configured as follows.

  With this configuration, even when the time required for the temperature of the thermowax to converge to a steady value varies due to the different characteristics of the thermowax, different time constants are set according to the conditions. Therefore, the temperature of the thermowax can be estimated with high accuracy.

  In the engine cooling system, the controller is configured such that the energization to the heating unit is on and the energization to the heating unit is off, and the temperature of the cooling water around the thermowax is equal to or higher than a preset temperature. Estimate the temperature of the thermowax by setting different time constants depending on the case and when the energization to the heating unit is off and the temperature of the cooling water around the thermowax is lower than the preset temperature It may be configured to.

  With this configuration, when the energization to the heating unit is in the on state, the same time constant is set regardless of the temperature of the surrounding cooling water, and when the energization to the heating unit is in the off state, Different time constants can be set according to the temperature of the surrounding cooling water.

  In this case, the preset temperature may be the melting temperature of the thermo wax.

  With this configuration, different time constants can be set depending on whether the temperature of the cooling water around the thermowax is equal to or higher than the melting temperature and lower than the melting temperature.

  The engine cooling system includes a cooling water temperature sensor provided in the cooling water passage, and the control device is configured to estimate the temperature of the cooling water around the thermowax based on the detection result of the water temperature sensor. It may be.

  If comprised in this way, the temperature of the cooling water around a thermo wax can be estimated.

  In the engine cooling system, the control device is configured to set a target value for the temperature of the thermowax and to control energization to the heating unit so that the estimated temperature of the thermowax becomes the target value. Also good.

  If comprised in this way, it can control with high precision so that the temperature of a thermo wax may become a target value.

  The control device according to the present invention is provided in an engine cooling system including a cooling water passage and a switching valve provided in the cooling water passage and including a thermo wax and a heating unit for heating the thermo wax. The control device is a control device that controls opening and closing of the switching valve, and is different depending on at least one of the on / off state of energization to the heating unit and the temperature of the cooling water around the thermowax. A constant is set to estimate the temperature of the thermowax.

  With this configuration, even when the time required for the temperature of the thermowax to converge to a steady value changes due to changes in the characteristics of the thermowax, different time constants are used depending on conditions. Since the temperature of the thermo wax can be estimated by setting, the temperature of the thermo wax can be estimated with high accuracy.

  According to the engine cooling system and the control device of the present invention, the temperature of the thermowax can be estimated with high accuracy.

It is a schematic block diagram which shows an example of the cooling system of the engine to which this invention is applied. It is sectional drawing which shows the structure of the switching valve used for the cooling system of FIG. Note that (A) shows the closed state of the switching valve, and (B) shows the opened state of the switching valve. In the engine cooling system of FIG. 1, a diagram (A) showing a flow of cooling water circulating through the cooling water passage during cold, and a flow of cooling water circulating through the cooling water passage when the engine is in a semi-warm-up state It is a figure which writes and shows figure (B) which shows this. FIG. 2 is a diagram showing a flow of cooling water circulating in a cooling water channel when the engine is completely warmed up in the engine cooling system of FIG. 1. FIG. 2 is a functional block diagram showing a configuration of an ECU used in the engine cooling system of FIG. 1. It is a figure for demonstrating the characteristic of the thermowax of the switching valve used for the cooling system of the engine of FIG. 2 is a flowchart for explaining a wax temperature estimation process by an ECU used in the engine cooling system of FIG. 1. It is a figure for demonstrating the valve opening control process by ECU used for the cooling system of the engine of FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  A cooling system (engine internal water stop cooling system) to which the present invention is applied will be described with reference to FIG.

  The cooling system in this example includes an electric water pump (electric WP) 2, a radiator 3, a thermostat 4, a heater 5, an exhaust heat recovery device 6, an EGR cooler 7, a switching valve 10, and cooling for circulating cooling water to these devices. A water passage 200 is provided.

  The cooling water passage 200 is configured to circulate cooling water (for example, LLC: Long Life Coolant) via the engine 1, the radiator 3, and the thermostat 4, and the cooling water to the EGR cooler 7, the exhaust heat recovery. And a heater passage 202 that circulates via the heater 6, the heater 5, and the thermostat 4. In this example, one electric water pump 2 is used in combination for circulating the cooling water between the engine cooling water passage 201 and the heater passage 202.

  The engine 1 is a gasoline engine, a diesel engine, or the like mounted on a conventional vehicle, a hybrid vehicle, or the like, and a water jacket (not shown) is provided on a cylinder block and a cylinder head. The engine 1 is provided with an engine water temperature sensor 21 that detects the water temperature of the cooling water outlet (water jacket outlet) 1b. An intake air temperature sensor 23 that detects the temperature of intake air and an air flow meter 24 that detects the amount of intake air to the engine 1 are disposed in the intake passage of the engine 1. Further, the engine 1 is provided with an engine speed sensor 25 that detects the number of rotations of the crankshaft that is the output shaft (engine speed). The output signals of the engine water temperature sensor 21, the intake air temperature sensor 23, the air flow meter 24, and the engine speed sensor 25 are input to an ECU (Electronic Control Unit) 300.

  The electric water pump 2 is a water pump capable of variably setting the discharge flow rate (discharge pressure) by controlling the number of revolutions of the electric motor, and the discharge port is a cooling water inlet (water jacket of the engine 1). It is arranged to communicate with the inlet 1a. The operation of the electric water pump 2 is controlled by the ECU 300. The electric water pump 2 is driven as the engine 1 is started, and the discharge flow rate is controlled according to the operating state of the engine 1 and the like.

  The thermostat 4 is a valve device that operates by, for example, expansion or contraction of thermowax in the temperature sensing unit. When the cooling water temperature is relatively low, the cooling water passage between the radiator 3 and the electric water pump 2 is blocked. Thus, the cooling water is not allowed to flow through the radiator 3 (engine cooling water passage 201). On the other hand, after the warm-up of the engine 1 is completed, that is, when the cooling water temperature is relatively high, the thermostat 4 operates (opens) in accordance with the cooling water temperature, and a part of the cooling water flows to the radiator 3. The heat recovered by the cooling water is released from the radiator 3 to the atmosphere. In this example, the thermostat 4 is set to open when the wax temperature reaches a temperature (for example, 82 ° C. or higher) higher than a valve opening temperature (for example, 70 ° C.) of the switching valve 10 described later. ing.

The heater passage 202 is a bypass passage that bypasses the engine 1. The EGR cooler 7, the exhaust heat recovery device 6, and the heater 5 are connected in series to the heater passage 202 from the upstream side of the cooling water flow. 7 → Exhaust heat recovery device 6 → Heater 5 → Thermostat 4 → Electric water pump 2]. A heater connection passage 202 a is connected to the heater passage 202 between the EGR cooler 7 and the exhaust heat recovery device 6. The heater connection passage 202a is connected to the cooling water outlet (water jacket outlet) 1b of the engine 1 through the switching valve 10. The switching valve (control valve) 10 opens and closes the heater connection passage 202a. Details of the switching valve 10 will be described later.

  The heater 5 is a heat exchanger for heating the passenger compartment using the heat of the cooling water, and is disposed facing the air duct of the air conditioner. That is, when the vehicle interior is heated (when the heater is on), the conditioned air flowing in the air duct is passed through the heater 5 (heater core) and supplied as warm air to the vehicle interior, while at other times (for example, during cooling) When the heater is turned off, the conditioned air bypasses the heater 5. The heater 5 is provided with a heater inlet water temperature sensor 22. An output signal of the heater inlet water temperature sensor 22 is input to the ECU 300. The inlet water temperature of the heater 5 is equivalent to the temperature of the cooling water flowing through the heater passage 202 (bypass passage).

  The exhaust heat recovery device 6 is disposed in the exhaust passage of the engine 1 and is a heat exchanger for recovering the heat of the exhaust gas with the cooling water, and the recovered heat is used for engine warm-up, vehicle interior heating, and the like. Is done. The EGR cooler 7 is a heat exchanger that is disposed in an EGR passage that recirculates a part of the exhaust gas that flows through the exhaust passage of the engine 1 to the intake passage, and cools the EGR gas that passes through (returns to) the EGR passage. .

-Switching valve-
Next, the switching valve 10 used in the cooling system will be described with reference to FIG.

  The switching valve 10 in this example includes a housing 11, a valve body 12, a compression coil spring 13, a temperature sensing unit 14, and the like.

  The housing 11 is provided with a cooling water inlet 11a connected to a cooling water outlet (water jacket outlet) 1b of the engine 1 shown in FIG. 1, a radiator connection port 11b connected to the radiator 3, and a heater connection port 11c. It has been. The heater connection port 11c is connected to the heater passage 202 via the heater connection passage 202a shown in FIG.

  A valve seat (valve seat) 111 and a spring seat 112 are provided inside the housing 11 so as to face each other. A space between the valve seat 111 and the spring seat 112 (a space on the upstream side of the valve body 12) serves as a water introduction portion 11d. The cooling water inlet 11a communicates with the water introduction portion 11d, and the radiator connection port 11b communicates with the cooling water inlet 11a via the water introduction portion 11d. A space downstream of the valve body 12 serves as a water outlet 11e, and the heater outlet 11c communicates with the water outlet 11e.

  The valve body 12 is disposed between the valve seat 111 and the spring seat 112 inside the housing 11 so as to be able to contact with and separate from the valve seat 111. The valve body 12 and a case 141 of a temperature sensing unit 14 described later are integrated. A compression coil spring 13 is sandwiched between the valve body 12 and the spring seat 112, and the valve body 12 is biased toward the valve seat 111 by the elastic force of the compression coil spring 13.

The temperature sensing unit (temperature sensing actuator) 14 includes a case 141 and a rod 142. The rod 142 is a rod-shaped member extending along the opening / closing direction of the valve body 12 and is slidably disposed on the case 141. The rod 142 passes through the valve body 12, and the valve body 12 can slide in the opening / closing direction with respect to the rod 142. The tip of the rod 142 passes through the wall 11 f of the housing 11 (the wall opposite to the cooling water inlet 11 a), and the tip is held by the rod holding member 16.

  The case 141 of the temperature sensing unit 14 is filled with a thermo wax 143 that expands and contracts due to a temperature change, and the amount of protrusion of the rod 142 with respect to the case 141 changes due to the expansion and contraction of the thermo wax 143. ing. The thermowax 143 is accommodated in a sealing material 144 made of rubber or the like.

  In the switching valve 10 having the above structure, when the wax temperature (the temperature of the thermowax 143) is lower than a predetermined value (70 ° C. in this example), the protruding amount of the rod 142 from the case 141 is small (inside the case 141). And the valve body 12 is seated (closed) on the valve seat 111 by the elastic force of the compression coil spring 13 (FIG. 2A). When the wax temperature is equal to or higher than the predetermined value (70 ° C. or higher) from such a valve closed state, the thermowax 143 of the temperature sensing unit 14 expands. Due to the expansion of the thermowax 143, the protruding amount of the rod 142 from the case 141 is increased, and the entire temperature sensing portion 14, that is, the valve body 12 is separated from the valve seat 111 against the elastic force of the compression coil spring 13. And the valve body 12 is separated (opened) from the valve seat 111 (FIG. 2B).

  Thus, the switching valve 10 in this example is closed when the wax temperature is lower than a predetermined value (70 ° C.), and the cooling water outlet 1b (engine cooling water passage 201) of the engine 1 and the heater shown in FIG. The passage 202 is blocked (circulation of the cooling water between the engine cooling water passage and the bypass passage is restricted). On the other hand, when the wax temperature is equal to or higher than a predetermined value (70 ° C. or higher), the valve is opened, and the cooling water outlet 1b (engine cooling water passage 201) and the heater passage 202 of the engine 1 shown in FIG. Although the cooling water inlet 11a and the radiator connection port 11b communicate with each other, when the thermostat 4 shown in FIG. 1 is in a closed state, the cooling water flowing into the cooling water inlet 11a flows to the radiator connection port 11b. Absent.

  Here, in the switching valve 10 of this example, an electric heater 15 is embedded in the temperature sensing unit 14, and the wax temperature can be controlled by heat generated by energizing the electric heater 15. . The electric heater 15 of the switching valve 10 is operated by a switching valve controller (not shown). The electric heater 15 is an example of the “heating unit” in the present invention. The energization of the electric heater 15 is controlled by the ECU 300, and the control of the switching valve 10 by the ECU 300 will be described in detail later.

-Cooling system operation explanation-
The flow of the cooling water circulating through the cooling water passage of the cooling system of the engine 1 shown in FIG. 1 will be described with reference to FIGS.

  First, during the cold period, the temperature of the water around the temperature sensing portion 14 of the switching valve 10 is low (less than 70 ° C.), so the switching valve 10 is closed and the flow of cooling water in the engine 1 (in the water jacket) stops. (Stops water in the engine). Thereby, the engine 1 is warmed up early. When the switching valve 10 is in the closed state, as shown in FIG. 3A, the cooling water is circulated in the heater passage 202 by the operation of the electric water pump 2, and the cooling water is [electric water pump 2 → EGR. It flows in the order of cooler 7 → exhaust heat recovery device 6 → heater 5 → thermostat 4 → electric water pump 2]. When there is a request for heating during such early warm-up, the amount of heat necessary for the heater 5 may be covered by the heat recovered by the exhaust heat recovery device 6.

  Next, the engine 1 is in a semi-warm-up state, a valve opening request is made, and the switching valve 10 is opened when the wax temperature becomes a predetermined temperature (70 ° C. or higher). When the switching valve 10 is opened, as shown in FIG. 3B, in addition to the cooling water circulation in the heater passage 202, the cooling water is [electric water pump 2 → cooling water inlet 1a of engine 1 → engine 1]. The engine 1 is cooled by flowing in the order of inside (in the water jacket) → cooling water outlet 1b of the engine 1 → switching valve 10 → heater connection passage 202a]. Further, when the switching valve 10 is opened, the cooling water in the engine cooling water passage 201 (in the engine 1) and the cooling water in the heater passage (bypass passage) 202 are mixed.

  Then, when the engine 1 is completely warmed up, as shown in FIG. 4, the thermostat 4 is actuated (opened) so that a part of the cooling water flows to the radiator 3, and the heat recovered by the cooling water is reduced. Released from the radiator 3 to the atmosphere.

-ECU-
Next, the ECU 300 will be described. The ECU 300 includes a CPU, a ROM, a RAM, a backup RAM, and the like. The ROM stores various control programs, maps that are referred to when the various control programs are executed, and the like. The CPU executes arithmetic processing based on various control programs and maps stored in the ROM. The RAM is a memory that temporarily stores calculation results from the CPU, data input from each sensor, and the like. The backup RAM is a non-volatile memory that stores data to be saved when the engine 1 is stopped. is there.

  The ECU 300 is connected to various sensors that detect the operating state of the engine 1 including the engine water temperature sensor 21, the intake air temperature sensor 23, the air flow meter 24, and the engine speed sensor 25. The ECU 300 is connected to the heater inlet water temperature sensor 22 and an ignition switch (not shown).

  ECU 300 is configured to control opening and closing of switching valve 10. Specifically, as shown in FIG. 5, ECU 300 includes an ambient water temperature estimation unit 301, a wax temperature estimation unit 302, a target value setting unit 303, an energization control unit 304, and a storage unit 305. . The ambient water temperature estimation unit 301, the wax temperature estimation unit 302, the target value setting unit 303, and the energization control unit 304 are realized by the CPU executing a control program stored in the ROM. The storage unit 305 includes a ROM, a RAM, a backup RAM, and the like. Moreover, each part of ECU300 is demonstrated in detail later.

−Estimation of ambient water temperature−
Based on the detection result (detected temperature thw) of the engine water temperature sensor 21 provided in the cooling water passage 200, the ambient water temperature estimation unit 301 performs a cooling water temperature around the thermowax 143 (hereinafter referred to as “ambient water temperature”) T_w. It has the function to estimate.

  Here, the engine water temperature sensor 21 is disposed in the vicinity of the cooling water outlet (water jacket outlet) 1 b and is disposed upstream of the switching valve 10. Thereby, for example, when the engine 1 is started and the detected temperature thw of the engine water temperature sensor 21 rises, it takes time until the temperature change is transmitted to the ambient water temperature T_w. That is, when the detected temperature thw of the engine coolant temperature sensor 21 changes, there is a time lag (time delay) until the ambient water temperature T_w reaches the detected temperature thw.

  Therefore, the ambient water temperature estimation unit 301 is configured to estimate the ambient water temperature T_w using the following equation (1) in consideration of the time delay described above.

G ₄ (s) = thw / (T ₄ s + 1) (1)
In this equation (1), G ₄ (s) is a transfer function of a first-order lag element, and thw is a steady gain, which is a detected temperature of the engine coolant temperature sensor 21. T ₄ is a time constant, and s is a Laplace operator. The time constant T ₄ is a constant obtained in advance by simulation or the like and is stored in the storage unit 305.

-Estimation of wax temperature-
[Characteristics of thermo wax for switching valve]
Next, the characteristics of the thermowax 143 of the switching valve 10 will be described with reference to FIG. Hereinafter, a case where the melting temperature of the thermowax 143 is a predetermined value (70 ° C.) will be described as an example. The predetermined value is an example of the “preset temperature” in the present invention.

First, as shown in FIG. 6A, when the energization to the electric heater 15 is on and the ambient water temperature T_w is lower than a predetermined value (70 ° C.), the thermowax 143 Melted from the surroundings. In this case, the wax temperature converges to a steady value K (T_w) corresponding to the ambient water temperature T_w with a time constant T ₁ .

Further, as shown in FIG. 6B, when energization to the electric heater 15 is in an on state and the ambient water temperature T_w is equal to or higher than a predetermined value (70 ° C.), the thermo wax 143 It is melted from the periphery and the outer periphery of the thermowax 143. Also in this case, the wax temperature converges to a steady value K (T_w) corresponding to the ambient water temperature T_w with a time constant T ₁ .

Thus, when the energization to the electric heater 15 is in the ON state, the electric heater 15 has a greater influence on the wax temperature than the ambient water temperature T_w. Therefore, regardless of the ambient water temperature T_w, the wax temperature is It converges to a steady value K (T_w) with the same time constant T ₁ .

  Note that the steady value K (T_w) is determined using, for example, a map indicating the correspondence between the ambient water temperature T_w and the steady value K. The correspondence between the ambient water temperature T_w and the steady value K is calculated in advance by simulation or the like, and a map that is the calculation result is stored in the storage unit 305.

In addition, as shown in FIG. 6C, when the energization to the electric heater 15 is changed from the on state to the off state and the ambient water temperature T_w is lower than a predetermined value (70 ° C.), Heat is released from around the heater 15 (see arrow H1), and the melted portion is solidified. In this case, the wax temperature, the time constant T ₂ converges to a steady value (near water temperature T_W).

As shown in FIG. 6D, when the energization to the electric heater 15 is off and the ambient water temperature T_w is equal to or higher than a predetermined value (70 ° C.), the thermowax 143 generates heat from the cooling water. Is added (see arrow H2) and melted from the outer periphery. In this case, the wax temperature converges to a steady value (ambient water temperature T_w) with a time constant T ₃ different from the time constant T ₂ .

  Thus, when the energization to the electric heater 15 is in the off state, the time constant differs between the case where the ambient water temperature T_w is equal to or higher than the predetermined value and the case where the ambient water temperature T_w is lower than the predetermined value.

  As described above, the time required for the thermowax 143 to converge on the wax temperature to a steady value varies depending on the on / off state of energization to the electric heater 15, and the energization to the electric heater 15 is off. Sometimes the time taken for the wax temperature to converge to a steady value varies depending on the ambient water temperature T_w. This is considered to be because the melting and solidification characteristics of the thermowax 143 differ depending on the on / off state of energization to the electric heater 15 and the condition of the ambient water temperature T_w.

Here, the time constants T _{1 to} T ₃ are constants obtained in advance by simulation or the like, and are stored in the storage unit 305. The time constant T ₁ is smaller than the time constants T ₂ and T ₃ . In other words, the wax temperature converges to a steady value earlier when the electric current to the electric heater 15 is on than when the electric current to the electric heater 15 is off. The time constants T ₂ and T ₃ may differ in magnitude depending on the shape and type of the thermowax 143 (the temperature sensitive part 14). That is, depending on the type of the switching valve 10, when the case who is greater than the time constant T ₃ and constants T _2, the time towards the constant T ₂ has may be smaller than the time constant T _3.

[Wax temperature estimation part]
The wax temperature estimation unit 302 has a function of estimating the temperature (wax temperature) of the thermowax 143 of the switching valve 10. Specifically, the wax temperature estimator 302 determines whether the energization to the electric heater 15 is on, the energization to the electric heater 15 is off, and the ambient water temperature T_w is less than a predetermined value. 15 is configured to estimate the wax temperature by setting different time constants T _{1 to} T ₃ according to the case where the energization to 15 is off and the ambient water temperature T_w is equal to or higher than a predetermined value. That is, in the ECU 300 according to the present embodiment, different time constants are set according to both the on / off state of energization of the electric heater 15 and the ambient water temperature T_w.

[Wax temperature estimation process]
Next, the wax temperature estimation process performed by the ECU 300 will be described with reference to FIG. This process is started when the engine 1 starts and is repeatedly executed every predetermined control cycle.

Step S1:
The ambient water temperature T_w is estimated by the ambient water temperature estimation unit 301 (see FIG. 5). Specifically, the response of the first-order lag obtained using the above equation (1) is estimated as the ambient water temperature T_w.

Step S2:
ECU 300 determines whether or not energization to electric heater 15 is in an on state. If it is determined that energization to the electric heater 15 is on, the process proceeds to step S3. On the other hand, if it is determined that energization of the electric heater 15 is in an off state (not an on state), the process proceeds to step S4.

Step S3:
The wax temperature estimation unit 302 estimates the wax temperature using the following equation (2).

G ₁ (s) = K (T_w) / (T ₁ s + 1) (2)
In this equation (2), G ₁ (s) is a transfer function of a first-order lag element, and K (T_w) is a steady gain. T ₁ is a time constant, and s is a Laplace operator. Note that K (T_w) is a steady value K corresponding to the ambient water temperature T_w estimated in step S1 with reference to a map showing a correspondence relationship between the ambient water temperature T_w and the steady value K.

That is, when energization to the electric heater 15 is on, the wax temperature is estimated using the transfer function G ₁ (s) in which the time constant T ₁ is set. That is, the first-order lag response obtained using the transfer function G ₁ (s) is estimated as the wax temperature.

Step S4:
ECU 300 determines whether or not ambient water temperature T_w estimated in step S1 is less than a predetermined value (70 ° C.). And when it is judged that the surrounding water temperature T_w is less than a predetermined value, it moves to step S5. On the other hand, when it is determined that the ambient water temperature T_w is equal to or higher than the predetermined value (not lower than the predetermined value), the process proceeds to step S6.

Step S5:
The wax temperature estimation unit 302 estimates the wax temperature using the following equation (3).

G ₂ (s) = T_w / (T ₂ s + 1) (3)
In this equation (3), G ₂ (s) is a transfer function of a first-order lag element, and T_w is a steady gain (ambient water temperature estimated in step S1). T ₂ is a time constant, and s is a Laplace operator.

That is, when the energization to the electric heater 15 is in an off state and the ambient water temperature T_w is less than a predetermined value, the transfer function G ₂ (s) in which the time constant T ₂ larger than the time constant T ₁ is set is obtained. Used to estimate wax temperature. That is, the first-order lag response obtained using the transfer function G ₂ (s) is estimated as the wax temperature.

Step S6:
The wax temperature estimation unit 302 estimates the wax temperature using the following equation (4).

G ₃ (s) = T_w / (T ₃ s + 1) (4)
In this equation (4), G ₃ (s) is a transfer function of a first-order lag element, and T_w is a steady gain (ambient water temperature estimated in step S1). T ₃ is a time constant, and s is a Laplace operator.

In other words, energization of the electric heater 15 is off, if the peripheral temperature T_w is a predetermined value or more, when greater than the constant T _1, and when set to a constant value T ₃ at a different time than the constant T ₂ The wax temperature is estimated using the transferred function G ₃ (s). That is, the first-order lag response obtained using the transfer function G ₃ (s) is estimated as the wax temperature.

-Switching valve control by ECU-
[Target value setting section]
The target value setting unit 303 (see FIG. 5) has a function of setting a target value of the temperature of the thermo wax 143 (see FIG. 2). Specifically, the target value setting unit 303 is configured to read out and set a target value corresponding to an operation mode (preheating mode, valve opening mode, water temperature mode, protection mode) described later from the storage unit 305. .

[Energization control unit]
The energization control unit 304 (see FIG. 5) is configured so that the temperature of the thermo wax 143 (the wax temperature estimated by the wax temperature estimation unit 302) becomes the target value set by the target value setting unit 303 (see FIG. 5). 2). That is, the energization control unit 304 has a function of controlling the on / off state of energization to the electric heater 15.

  Specifically, the energization control unit 304 energizes the electric heater 15 when the wax temperature estimated by the wax temperature estimation unit 302 is lower than the target value, and the wax temperature estimated by the wax temperature estimation unit 302. When the value is higher than the target value, the electric heater 15 is not energized.

[Switching valve control processing]
Next, the switching valve control process by the ECU 300 will be described with reference to FIG. This process is executed by the ECU 300 and is started when the engine 1 is started. The switching valve control process is performed in parallel with the wax temperature estimation process described above.

  First, when the engine 1 (see FIG. 1) is started, the preheating mode is set as shown in FIG. In the preheating mode, the target value setting unit 303 (see FIG. 5) sets the target value of the wax temperature to the preheating temperature (for example, 60 ° C.).

  At this time, the energization control unit 304 (see FIG. 5) controls the energization of the electric heater 15 (see FIG. 1) so that the wax temperature becomes the preheating temperature (60 ° C.). As a result, when a valve opening request is made, the switching valve 10 (see FIG. 1) can be quickly opened. In the preheating mode, the switching valve 10 is closed, and as shown in FIG. 3A, it is cold and the engine 1 is warmed up.

  Thereafter, when a valve opening request is made, the valve opening mode is set. In the valve opening mode, the target value setting unit 303 sets the target value of the wax temperature to the valve opening temperature (for example, 70 ° C.). The energization control unit 304 controls energization of the electric heater 15 so that the wax temperature becomes the valve opening temperature.

  The valve opening request is made when ECU 300 determines that the temperature of the cooling water in engine 1 reaches a predetermined temperature (for example, 70 ° C.) after a predetermined time (for example, 20 seconds) has elapsed. Is called.

  When the wax temperature reaches the valve opening temperature, the water temperature mode is set. In the water temperature mode, the target value setting unit 303 gradually increases the target value of the wax temperature to the fully open temperature of the switching valve 10 (for example, 83 ° C.). The energization control unit 304 controls energization of the electric heater 15 so that the wax temperature becomes the target value. Thereby, it is possible to suppress a sudden change in the water temperature detected by the engine water temperature sensor 21 by gradually opening the switching valve 10.

  Thereafter, the protection mode is set, and the target value setting unit 303 sets the target value of the wax temperature to the fully open temperature (83 ° C.) of the switching valve 10. The energization controller 304 controls the energization of the electric heater 15 so that the wax temperature becomes the fully open temperature (83 ° C.). Thereby, when the wax temperature becomes sufficiently high, it is possible to suppress excessive energization, and thus it is possible to suppress deterioration of the temperature sensing unit 14 (see FIG. 2).

-Effect-
In the present embodiment, as described above, when energization to the electric heater 15 is in an on state, energization to the electric heater 15 is in an off state, and the ambient water temperature T_w is lower than a predetermined value, to the electric heater 15. The wax temperature is estimated by setting different time constants T _{1 to} T ₃ according to the case where the energization of is in an off state and the ambient water temperature T_w is equal to or higher than a predetermined value.

With this configuration, even when the time required for the wax temperature to converge to a steady value varies due to the different melting and solidification characteristics of the thermowax 143, Since the wax temperature can be estimated by setting the constants T _{1 to} T ₃ , the wax temperature can be estimated with high accuracy. Thereby, since the occurrence of valve opening delay can be suppressed, it is possible to suppress the occurrence of overheating due to boiling of the cooling water in the engine (in the water jacket). Moreover, since generation | occurrence | production of an early valve opening can be suppressed, it can suppress that the effect of a fuel consumption improvement is reduced. Moreover, since it can suppress that the thermowax 143 is heated unnecessarily, deterioration of the switching valve 10 can be suppressed.

  Moreover, in this embodiment, the surrounding water temperature estimation part 301 estimates the surrounding water temperature T_w in consideration of the time delay, and thus the surrounding water temperature T_w is estimated with high accuracy based on the detected temperature thw of the engine water temperature sensor 21. be able to.

-Other embodiments-
In addition, embodiment disclosed this time is an illustration in all the points, Comprising: It does not become a basis of limited interpretation. Therefore, the technical scope of the present invention is not interpreted only by the above-described embodiments, but is defined based on the description of the scope of claims. Further, the technical scope of the present invention includes all modifications within the meaning and scope equivalent to the scope of the claims.

  For example, in the present embodiment, the electric water pump 2 is used for circulating the cooling water. However, the present invention is not limited to this, and a mechanical water pump may be used for circulating the cooling water.

  Further, in the present embodiment, a cooling system in which a heater, an exhaust heat recovery device, and an EGR cooler are incorporated as a heat exchanger is shown. The present invention may be applied to a cooling system in which a vessel is incorporated.

  In the present embodiment, an example in which different time constants are set according to both the on / off state of energization to the electric heater 15 and the ambient water temperature T_w has been described. Different time constants may be set in accordance with one of the on / off state of energization 15 and the ambient water temperature T_w.

Further, in the present embodiment, an example in which the time constant T ₁ is set when the energization to the electric heater 15 is in the on state is shown, but the present invention is not limited thereto, and the energization to the electric heater 15 is in the on state. In some cases, the time constant may be different between the case where the ambient water temperature T_w is equal to or higher than a predetermined value and the case where the ambient water temperature T_w is lower than a predetermined value.

  Further, in the present embodiment, an example is shown in which a map indicating a correspondence relationship between the ambient water temperature T_w and the wax temperature steady value K is stored in the storage unit 305 in order to obtain the wax temperature steady value K (T_w). However, the present invention is not limited to this, and a map indicating the correspondence between the ambient water temperature T_w and the steady value of the lift amount is stored in the storage unit 305 in order to obtain the steady value of the lift amount (opening degree) of the switching valve 10. May be. In this case, since the lift amount and the wax temperature have a corresponding relationship, the steady value of the wax temperature may be obtained based on the steady value of the lift amount.

  In the present embodiment, an example is shown in which different time constants are set depending on whether the ambient water temperature T_w is equal to or higher than the melting temperature of the thermowax 143 and lower than the melting temperature. The boundary temperature to be used may be other than the melting temperature of the thermowax 143.

  Moreover, in this embodiment, although the surrounding water temperature estimation part 301 showed the surrounding water temperature T_w in consideration of the time delay based on the detection temperature thw of the engine water temperature sensor 21, although not limited to this, A sensor for detecting the ambient water temperature T_w may be separately provided.

  In the present embodiment, an example is shown in which the water temperature mode is sandwiched after the valve opening mode and the protection mode is set. However, the present invention is not limited thereto, and the water temperature mode is directly sandwiched after the valve opening mode. The protection mode may be set. That is, after the switching valve 10 is opened, the wax temperature target value may be set to the full opening temperature (83 ° C.) of the switching valve 10 without gradually increasing the wax temperature target value.

  Further, in the present embodiment, the values such as the predetermined value are only examples, and are not limited to the above values.

10 Switching valve 15 Electric heater (heating unit)
21 Engine water temperature sensor (water temperature sensor)
143 Thermowax 200 Cooling water passage 300 ECU (control device)

Claims (6)

A cooling water passage,
A switching valve provided in the cooling water passage and including a thermo wax and a heating unit for heating the thermo wax;
An engine cooling system comprising a control device for controlling opening and closing of the switching valve,
The control device sets a different time constant according to at least one of the on / off state of energization to the heating unit and the temperature of cooling water around the thermowax, and the thermowax An engine cooling system configured to estimate temperature. The engine cooling system according to claim 1,
The control device, when energization to the heating unit is in an on state, energization to the heating unit is in an off state, and the temperature of the cooling water around the thermowax is equal to or higher than a preset temperature, The temperature of the thermowax is set by setting different time constants depending on the case where the energization to the heating unit is off and the temperature of the cooling water around the thermowax is lower than the preset temperature. An engine cooling system characterized by being configured to estimate. The engine cooling system according to claim 2,
The engine cooling system, wherein the preset temperature is a melting temperature of the thermowax. The engine cooling system according to any one of claims 1 to 3, comprising:
A cooling water temperature sensor provided in the cooling water passage;
The engine cooling system, wherein the control device is configured to estimate a temperature of cooling water around the thermowax based on a detection result of the water temperature sensor. An engine cooling system according to any one of claims 1 to 4, comprising:
The control device is configured to set a target value of the temperature of the thermowax and to control energization to the heating unit so that the estimated temperature of the thermowax becomes the target value. Characteristic engine cooling system. A control device that is provided in a cooling system of an engine that includes a cooling water passage and a switching valve that is provided in the cooling water passage and includes a thermowax and a heating unit that heats the thermowax, and controls opening and closing of the switching valve Because
The temperature of the thermowax is estimated by setting different time constants according to at least one of the on / off state of energization to the heating unit and the temperature of the cooling water around the thermowax. It is comprised in the control apparatus characterized by these.

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