JPH0540256Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a control device for an exhaust heat exchanger for utilizing 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 substantially reducing the effectiveness of the cabin heater. Efforts are being made to shorten the time it takes to get started. As this type of device, for example,
An example of a structure for controlling the operation of an exhaust heat exchanger using a temperature sensor is disclosed in Japanese Unexamined Patent Publication No. 61-104216 or Japanese Utility Model Application Publication No. 61-104217.

<Problems to be solved by the invention> However, such heat exchangers have states in which heat exchange is performed and states in which heat exchange is not substantially performed, but in general, heat exchangers in which heat exchange is performed In order to achieve this, it is necessary to ensure a necessary contact area for heat transfer, so the exhaust resistance becomes relatively large when heat exchange is performed. However, in general, when starting an engine when the coolant is at a low temperature, it is relatively difficult to start the engine, and even if the engine is started, it is difficult to stabilize the rotation. When starting an engine equipped with a heat exchanger, there has been a problem in that the increased exhaust resistance of the engine makes it difficult to start the engine or tends to stall even after starting.

Utility Model Application No. 61-104219 uses an actuator that responds to the intake negative pressure of the engine to drive the switching valve of the exhaust gas passage of the exhaust heat exchanger, and when the intake negative pressure is below a predetermined value, heat exchange is performed. A control device for an exhaust heat exchanger has been disclosed in which heat exchange is performed only when the intake negative pressure is high, and the exhaust resistance is reduced. Although such a control device can avoid stalls caused by exhaust resistance when the throttle is opened, it is complicated to set the intake negative pressure that drives the actuator, and it is not always possible to start the engine when the engine is cold as described above. I can't improve my sexuality.

In view of these problems in the prior art, the main purpose of the present invention is to provide a control device for an exhaust heat exchanger that uses exhaust gas without interfering with engine startability and stability of engine speed. It's about doing.

<Means for Solving the Problems> According to the present invention, this purpose is to achieve a first state in which heat exchange is performed between engine exhaust gas and cooling water and exhaust resistance is relatively large; The second part where the heat exchange is not substantially performed and the exhaust resistance is relatively small.
A control device for an exhaust heat exchanger of an engine having a state of said first state and said second state.
a selection means for selecting the second state; a means for detecting cranking of the engine; and a selection means for selecting the second state at least within a predetermined time after the start of cranking according to a detection result of the cranking detection means. This is achieved by providing a control device for an exhaust heat exchanger, characterized in that it has a control means for controlling the selection of the exhaust heat exchanger.

<Function> By doing this, the exhaust resistance will not increase when the engine starts and immediately after, and the heat exchange between the exhaust gas and the cooling water will not begin until after the engine starts easily and the rotational speed has stabilized. will be carried out.

<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. Further, the thermostat 7 opens only when the temperature is high, and a bypass passage 5 is provided between the upstream side of the thermostat 7 and the upstream side of the water pump 6.
Therefore, since the thermostat 7 is closed when the engine is cold, the cooling water is directly returned to the engine 1 via the bypass passage 5, thereby promoting warm-up.

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 of an exhaust heat exchanger 9, which will be described later.
A passage 11 led out from the water pump 4 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. If the heater is not used, 3
By switching the direction valve 12, the cooling water from the passage 11 is routed to the bypass passage 14 without passing through the heater core 13.
From there, it is directly returned to the engine side via a return passage 15.

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. A solenoid 22a of this solenoid valve 22 is connected to the ECU 25. Also, a cooling water temperature sensor 23 provided in the passage 11, an engine rotation speed sensor 26 attached to the engine 1, and a starter switch 2 are provided.
7 is also connected to the ECU 25.

FIG. 2 is a block diagram schematically showing the functions of the ECU 25. The signal sent from the engine rotation speed sensor 26 is sent to the CPU 30 via the waveform shaping circuit 28 and counter 29. Also,
Signals sent from the starter switch 27 and the cooling water temperature sensor 23 provided in the passage 11 communicating with the cooling water outlet of the heat exchanger 9 are sent to the level correction circuit 31, the multiplexer 32, and the A/D converter 33. It is sent to the CPU 30 via the CPU 30. CPU3
0 follows the program stored in the ROM 34 and the data stored in the ROM 34 as well.
The data from each sensor temporarily stored in the RAM 35 is 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. In step 41 of FIG. 3, an initializing operation is performed, and in step 42, it is determined whether the cooling water temperature is higher than 90°C. If it is higher than 90°C, that is, the engine 1 is almost warmed up. If the switching is completed, the process proceeds to step 48, where the power supply to the solenoid 22a is stopped, and atmospheric pressure is supplied to the actuator 21 from the solenoid valve 22, and the torsion coil spring, etc. (not shown) provided in the switching valve 17 is activated. The switching valve 17
is fully opened. Here, exhaust gas central passage 1
8 has a relatively low flow resistance with respect to the exhaust gas annular passage 19, and most of the exhaust gas passes through the exhaust gas central passage 18 and remains as it is with almost no heat exchange with the cooling water in the water jacket 24. It comes to be discharged to the outside air via the muffler 20.

If the coolant temperature is 90° C. or less in step 42, the process proceeds to step 43, where it is determined whether or not the engine 1 is cranking. If cranking is in progress, the process proceeds to step 46, where it is determined whether the engine rotation speed is higher than 1000 rpm. If the engine speed is less than 1000 rpm, that is, if starting of the engine is not detected, a timer not shown in FIG. 3 is set to 2 seconds in step 47, and the process proceeds to step 48. If the engine is not cranking in step 43, or if the engine speed is not cranking in step 46,
If the rpm is higher than 1000 rpm, that is, if starting of the engine is detected, the process proceeds to step 44. In step 44, if there is time left on the timer described above, the process proceeds to step 48; if the timer has timed up, the process proceeds to step 45, where power is supplied to the solenoid 22a and the intake negative pressure of the engine is changed to the negative pressure actuator 21. The switching valve 17 is activated, the cooling water in the water jacket 24 is heated and the temperature rises quickly, and the heater core 13 quickly becomes capable of heating. Then, heat exchange is performed until the engine 1 is stopped or the cooling water temperature reaches 90° C. or higher.

Here, the flow shown in FIG. 3 is executed continuously, and always controls the switching valve 17, that is, the heat exchanger 9.
will be controlled. Note that even the cooling water after heating the passenger compartment by the heater core 13 retains a certain amount of exhaust gas heat, so it is returned to the water jacket of the engine 1 via the passage 15 to promote warming. You can also get the work done.

It goes without saying that the present invention is not limited to the above and can be applied to various applications.For example, in step 47 of the flowchart in Fig. 3, the timer setting value was set to 2 seconds, but the It may be any time that is stable, and the engine rotational speed in step 46 or the cooling water temperature in step 42 may be set arbitrarily.

<Effects of the invention> As described above, according to the invention, since the exhaust resistance in the exhaust gas passage does not increase when the engine is started at low temperature, starting is easier and the engine can be started quickly without any loss in engine performance. This is extremely effective because it can heat the room and warm up the engine more quickly.

[Brief explanation of the drawing]

FIG. 1 is a diaphragm 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 the 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 , 11...Aisle, 12...
...3-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... Engine speed sensor, 27... Starter switch, 28... Waveform shaping circuit, 29... Counter,
30...CPU, 31...Level correction circuit, 32
...Multiplexer, 33...A/D converter, 34...ROM, 35...RAM, 36...
Drive circuit, 41-48...steps.

Claims (1)

[Claims for Utility Model Registration] A first state in which heat exchange occurs between engine exhaust gas and cooling water and the exhaust resistance is relatively large; and a first state in which the heat exchange does not substantially occur and the exhaust resistance is relatively large. A control device for an exhaust heat exchanger of an engine having a small second state, comprising: selection means for selecting the first state and the second state; and detecting cranking of the engine. and control means for controlling the selection means to select the second state at least within a predetermined time after the start of cranking according to the detection result of the cranking detection means. A control device for an exhaust heat exchanger.