JPH0541213Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a control device for an exhaust heat exchanger that utilizes the heat of engine exhaust gas.

<Conventional technology> Conventionally, a heat exchanger installed in the exhaust system of a vehicle engine has been used to heat cooling water when the engine is cold, thereby reducing the time it takes to warm up the engine and the time when the vehicle interior heater actually starts working. is being shortened. As a device for controlling this kind of heat exchanger, for example, Utility Model Application No. 104216/1983 or Utility Model Application No. 61-
Japanese Patent Application No. 104217 discloses a system in which the operation of an exhaust heat exchanger is controlled using a cooling water temperature sensor provided in a water jacket and a radiator of an engine.

<Problem to be solved by the invention> However, when the outside air temperature is relatively high, the engine temperature and the cooling water temperature generally rise quickly, so the operation of the exhaust heat exchanger cannot be controlled solely by the cooling water temperature. If this occurs, the cooling water may be heated excessively.

In view of these problems in the prior art, the main purpose of the present invention is to provide an exhaust heat exchanger that appropriately exchanges heat between exhaust gas and cooling water without excessively heating the engine cooling water. The purpose of this invention is to provide a control device for.

<Means for Solving the Problems> According to the present invention, such an object is provided in the exhaust passage of an engine equipped with a cooling water system, and a selection means is provided to transfer heat between exhaust gas and the cooling water. A control device for an exhaust heat exchanger that can selectively take either a first state in which heat exchange is performed and a second state in which heat exchange is not substantially performed, the control device comprising: means for detecting outside air temperature; , means for detecting the temperature of the cooling water, selecting the first state when the temperature of the cooling water is below a predetermined value, and selecting the second state when the temperature of the cooling water exceeds the predetermined value. This is achieved by providing a control device for an exhaust heat exchanger, characterized in that the state is selected and the predetermined value is set to a low value when the outside air temperature is high.

<Function> By doing so, the cooling water will not be heated more than necessary due to heat exchange.

<Embodiments> The present invention will now be described in detail with reference to specific embodiments with reference to the accompanying drawings.

FIG. 1 is a diagram schematically showing the cooling water system and exhaust gas passage of a vehicle to which the present invention is applied. The water jacket of the engine 1 has a cooling water passage 2 led out from the water jacket and having a thermostat 7, and a radiator 3.
and a cooling water passage 4 having a water pump 6 on the side returning to the water jacket of the engine 1.
The cooling water is pumped toward the water jacket of the engine 1, and the cooling water whose temperature has risen in contact with the engine 1 is sent to the radiator 3 to cool the engine. Here, the motor 28 of the radiator fan 27
is connected to a thermo switch 29 that turns on at 90°C or higher, and when the cooling water temperature reaches 90°C or higher, the radiator fan 27 is driven.

The thermostat 7 opens only when the cooling water temperature reaches 82°C or higher, and a bypass passage 5 is provided between the upstream side of the thermostat 7 and the upstream side of the water pump 6.
is provided. Therefore, when the engine is cold, the thermostat 7 is closed, so that the cooling water directly flows through the bypass passage 5 to the engine 1.
warm-up is promoted.

The water jacket of the engine 1 is also connected to a heater passage 8 having a relatively small diameter. The heater passage 8 is connected to a water jacket 24 via a cooling water inlet 9a of an exhaust heat exchanger 9, which will be described later, and is connected to a cooling water outlet 9 from the water jacket 24.
The passage 11 led out through b passes through a three-way valve 12 and reaches a heater core 13, which is connected to the upstream side of the water pump 6 via a return passage 15. When the heater is not used, the three-way valve 12 is switched so that the cooling water from the passage 11 is directly returned to the engine side from the bypass passage 14 through the return passage 15 without passing through the heater core 13.

Exhaust gas discharged from the engine is introduced into the exhaust heat exchanger 9 through the exhaust gas passage 16, passes through the exhaust gas central passage 18 or the exhaust gas annular passage 19 depending on the state of the switching valve 17, and then passes through the muffler 20. It is then released into the atmosphere. That is, when the switching valve 17 is closed, the exhaust gas exclusively passes through the exhaust gas annular passage 19, and heat exchange is actively performed between the exhaust gas and the cooling water in the water jacket 24.
When the valve is opened, the exhaust gas generally travels straight through the exhaust gas central passage 18 without being subjected to exhaust resistance.

The switching valve 17 is driven to open and close by a negative pressure actuator 21, and a negative pressure chamber of the negative pressure actuator 21 is connected to an intake pipe of the engine via a solenoid valve 22. The solenoid 22a of this solenoid valve 22 is controlled by the ECU 25. Further, a cooling water temperature sensor 23 provided in the passage 11 led out from the cooling water outlet 9b of the water jacket 24 and an outside temperature sensor 26 provided in the engine compartment are also connected to the ECU 25.

FIG. 2 is a block diagram schematically showing the functions of the ECU 25. Signals sent from the cooling water temperature sensor 23 and the outside air temperature sensor 26 are sent to the CPU 30 via a level correction circuit 31, a multiplexer 32, and an A/D converter 33. CPU
30 follows the program stored in the ROM 34 and the data stored in the ROM 34 as well.
The data from both sensors temporarily stored in the RAM 35 are compared, and power is selectively supplied to the solenoid 22a shown in FIG. 1 via the drive circuit 36 and switched via the negative pressure actuator 21. The valve 17 will be opened and closed.

Next, the operation of this embodiment will be explained based on the flowchart shown in FIG. Steps in Figure 3
Initialize operation is performed in step 42, and step 43
determine whether the outside temperature is higher than 15℃,
If it is lower than 15°C, the process proceeds to step 44, where it is determined whether the cooling water temperature is higher than a set value lower than 90°C at which the radiator fan 27 operates, for example, 85°C. If the cooling water temperature is higher than 85° C., that is, if the engine 1 has been warmed up, the process proceeds to step 45 and the supply of power to the solenoid 22a is stopped. As a result, the actuator 21 is supplied with atmospheric pressure from the solenoid valve 22, and the switching valve 17 is supplied with atmospheric pressure.
The switching valve 17 is brought into a fully open state by the action of a torsion coil spring (not shown) provided therein. Here, the exhaust gas central passage 18 is the exhaust gas annular passage 19.
Most of the exhaust gas passes through the exhaust gas central passage 18, which has relatively low flow resistance, and is released to the outside via the muffler 20 without almost any heat exchange with the cooling water in the water jacket 24. will be done.

If the outside temperature is below 15℃ in step 43,
Proceeding to step 46, it is determined whether the cooling water temperature is higher than 70°C. Step if higher than 70℃
45, the power supply to the solenoid 22a is stopped. If the cooling water temperature is below 70°C in step 46, the process proceeds to step 47, and solenoid 2
2a, the intake negative pressure of the engine is supplied to the negative pressure actuator 21, the switching valve 17 is operated, the cooling water in the water jacket 24 is heated by the exhaust gas, and the temperature rises early, and the heater core 13 is heated. will soon have heating capacity. Further, even when the heater is not used, the cooling water is heated by the exhaust gas, thereby promoting warm-up. This process is repeated in a predetermined cycle until the cooling water temperature reaches 70°C or higher if the outside temperature is higher than 15°C, or until the cooling water temperature reaches 85°C or higher if the outside temperature is below 15°C. Heat exchange continues until

Here, since the sensor 23 detects the temperature near the cooling water outlet 9b of the heat exchanger 9 where the cooling water temperature is the highest, the cooling water in the passage 11 is not heated excessively due to heat exchange. do not have. Furthermore, by setting the temperature at which the power supply to the solenoid 22a is stopped to be lower than, for example, 90° C. at which the radiator fan operates, the radiator fan may be driven unnecessarily or heat exchange may be performed unnecessarily. The situation can be avoided.

It goes without saying that the present invention is not limited to the above and can be applied in various ways. For example, in the present embodiment, one cooling water temperature sensor detects two different set temperatures. Two temperature switches with different set temperatures may also be used. Furthermore, the set temperature of the cooling water in step 46 of the flowchart in FIG. You may decide as appropriate.

<Effects of the invention> As described above, according to the invention, when the outside temperature is relatively high, by stopping heat exchange before the cooling water temperature reaches a high temperature, the engine load is reduced and the cooling water is not used more than necessary. The effect is extremely large because the heat exchanger is not heated and the heat exchanger can be suitably controlled.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a cooling switch system of a vehicle to which a control device for an exhaust heat exchanger according to the present invention is applied. FIG. 2 is a block diagram showing the main parts of FIG. 1 in an enlarged manner. FIG. 3 is a flow diagram showing control of the exhaust heat exchanger based on the present invention. 1... Engine, 2... Passage, 3... Radiator, 4... Passage, 5... Bypass passage, 6... Water pump, 7... Thermostat, 8... Passage, 9... Exhaust heat exchanger , 9a... Cooling water inlet, 9b... Cooling water outlet, 11... Passage, 12
...Three-way valve, 13...Heater core, 14,15...
... Passage, 16 ... Exhaust gas passage, 17 ... Switching valve, 18 ... Exhaust gas central passage, 19 ... Exhaust gas annular passage, 20 ... Muffler, 21 ... Negative pressure actuator, 22 ... Solenoid valve, 22a
... Solenoid, 23 ... Temperature sensor, 24 ...
Water jacket, 25...ECU, 26...
Outside temperature sensor, 27...Radiator fan, 28
...Motor, 29...Thermoswitch, 30...
CPU, 31... Level correction circuit, 32... Multiplexer, 33... A/D converter, 34...
...ROM, 35...RAM, 36...drive circuit,
42-47...Step.

Claims (1)

[Claims for Utility Model Registration] A first state in which heat exchange is performed between the exhaust gas and the cooling water, and the heat exchange is substantially A control device for an exhaust heat exchanger that can selectively take one of the second states in which the temperature is not set, the control device comprising means for detecting outside air temperature and means for detecting the temperature of the cooling water. , when the cooling water temperature is below a predetermined value, the first state is selected; when the cooling water temperature exceeds the predetermined value, the second state is selected; and when the predetermined value is the outside temperature. A control device for an exhaust heat exchanger, characterized in that the value is set to a low value when the value is high.