JP2012052488A - Cooling device of internal combustion engine - Google Patents

Abstract

When a flow rate is restricted by a flow rate control valve (at zero flow), cooling water stays and the detected value of a water temperature sensor tends to be lower than the actual cooling water temperature near the cylinder.
A main cooling water flow path R1 that circulates cooling water between a radiator 12 and the inside of the internal combustion engine 10, and a bypass flow path R2 that bypasses the radiator 12 and circulates the cooling water inside the internal combustion engine 10. The thermostat valve 19 which switches both R1 and R2 and the water temperature sensor 33 which outputs the detected value according to the temperature of the cooling water are provided. At the time of zero flow in which the thermostat valve 19 is closed and the flow rate of the bypass flow path R2 is limited by the flow rate control valve 32 as in the cold engine state, the temperature rise of the cooling water in the vicinity of the cylinder is compared with the detected value of the water temperature sensor 33. The estimated cooling water temperature is calculated, and the estimated cooling water temperature is set as the cooling water temperature.
[Selection] Figure 1

Description

  The present invention relates to a water-cooled cooling device for an internal combustion engine.

  As described in Patent Document 1, many of internal combustion engines represented by automobile internal combustion engines are provided with a water-cooling type cooling device by forced circulation of cooling water. In this type of cooling device, in order to promote the temperature rise of the cooling water when the engine is cold, the radiator is bypassed separately from the main cooling water flow path for circulating the cooling water between the radiator and the internal combustion engine. It has a bypass channel that circulates cooling water inside the internal combustion engine. When the engine is cold, the temperature is switched to the bypass channel by a channel switching valve such as a thermostat, and the radiator is bypassed to increase the temperature of the cooling water. is doing.

Japanese Patent Laid-Open No. 11-182241

  Further, in recent years, it is desired to quickly raise the temperature when the engine is cold in order to purify the exhaust gas. When the engine is cold, after switching to the bypass flow path by the flow path switching valve as described above, the flow control valve is further used. The present applicant is considering that the flow rate of cooling water circulating in the bypass flow path is limited to significantly suppress or stop the cooling water flow (hereinafter also referred to as zero flow). By performing such zero flow, warming up can be promoted by quickly raising the temperature of the cooling water staying in the vicinity of the combustion chamber and the cylinder, which is susceptible to heat from combustion.

  By the way, the temperature of the cooling water in the cylinder block of the internal combustion engine and the water jacket of the cylinder head is detected by, for example, a water temperature sensor provided in the internal combustion engine, and this cooling water temperature is determined in addition to the determination of the engine cold state, Used for setting fuel injection timing. The water temperature sensor is generally attached to the outer wall of an internal combustion engine such as a cylinder block or a cylinder head with the temperature sensing portion facing the water jacket.

  However, since the cooling water in the water jacket stays (or circulates at a very slow speed) at the time of the above-described zero flow, there is a temperature difference, that is, a temperature variation depending on the position of the water jacket. growing. For example, in a water jacket, heat from combustion is easily transmitted in the vicinity of a combustion chamber or cylinder, so that the temperature tends to be relatively high. On the other hand, in the vicinity of an outer wall of an internal combustion engine to which a temperature sensor is attached, the combustion chamber or cylinder The temperature is relatively low, and the temperature is relatively low. For this reason, the detection value detected by the water temperature sensor deviates to the lower side compared to the actual temperature of the cooling water near the combustion chamber and the cylinder, and various controls using the cooling water temperature become inaccurate. Since the end determination of the engine cold state (warm-up operation) is delayed and the warm-up operation is unnecessarily prolonged, there is a possibility of causing deterioration of fuel consumption and exhaust.

  The present invention has been made in view of such circumstances. That is, the cooling device for an internal combustion engine according to the present invention includes a main cooling water passage for circulating cooling water between the radiator and the inside of the internal combustion engine, and a bypass for bypassing the radiator and circulating the cooling water inside the internal combustion engine. A flow path, a flow path switching valve that switches between the main cooling water flow path and the bypass flow path, and cooling water that circulates in the bypass flow path while being switched to the bypass flow path by the flow path switching valve. A flow rate control valve for limiting the flow rate, a water temperature sensor that outputs a detection value corresponding to the temperature of the cooling water inside the internal combustion engine, a water temperature setting means that sets the cooling water temperature based on the detection value of the water temperature sensor, have. Then, the water temperature setting means obtains a predicted coolant temperature taking into account the temperature rise of the coolant near the cylinder with respect to the detected value of the coolant temperature sensor when the flow rate is restricted by the flow control valve, and this coolant temperature predicted value Is set as the cooling water temperature.

  For example, when the engine is cold, such as cold start (cold start), in order to promote warm-up, the flow is switched to the bypass flow path by the flow path switching valve and then circulated in the bypass flow path by the flow control valve Limit water flow. And when the flow rate is restricted by such a flow control valve (at zero flow), the flow of the cooling water is remarkably restricted or stopped, so the detected value of the water temperature sensor is lower than the actual temperature of the cooling water near the cylinder. However, in the present invention, the predicted cooling water temperature considering the temperature rise of the cooling water near the cylinder is set as the cooling water temperature. It is possible to set the cooling water temperature appropriately in anticipation.

  As described above, according to the present invention, even when the flow rate of the bypass passage is limited by the flow control valve when the engine is cold (at the time of zero flow), the cooling water temperature is anticipated in anticipation of the temperature rise of the cooling water near the cylinder. Can be set appropriately, and the setting accuracy of the cooling water temperature is improved. Therefore, when the engine is cold, the cooling water temperature is suppressed / avoided to deviate from the cooling water temperature near the actual cylinder, and the fuel consumption is deteriorated or the exhaust gas is deteriorated due to unnecessarily prolonged warm-up operation. Can be suppressed and avoided.

The block diagram which shows simply the cooling device of the internal combustion engine which concerns on one Example of this invention. The temperature distribution of the cooling water inside an internal combustion engine is shown typically, FIG. 2 (A) is a state after warm-up, and (B) is an explanatory view showing the state of zero flow. The flowchart which shows the setting process of the cooling water temperature which concerns on the said Example. The flowchart which shows the calculation process of a cooling water temperature estimated value. The flowchart which shows the start determination process of a zero flow. The flowchart which shows the completion | finish determination process of a zero flow. The flowchart which shows the calculation process of a cooling water temperature estimated value. Explanatory drawing which shows the completion | finish time of the zero flow by a cooling water temperature estimated value. Explanatory drawing which shows the setting of the EGR rate (A) using a cooling water temperature, fuel injection timing (B), pilot injection quantity (C), and fuel injection pressure (D).

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram schematically showing a cooling device for an internal combustion engine 10 according to an embodiment of the present invention. As shown by the arrows in the figure, the coolant is circulated in the coolant flow paths R1 and R2 by the water pump 11 driven by the crankshaft of the internal combustion engine 10. Here, a thick-filled arrow indicates the main cooling water channel R1, and a thick white arrow indicates the bypass channel R2.

  The main cooling water flow path R1 circulates the cooling water between the radiator 12 and the internal combustion engine 10 in order to cool the cooling water via the radiator 12 in the operation state after warming up. In the main cooling water flow path R1, the cooling water fed by the water pump 11 passes through water jackets 15 and 16 (see FIG. 2) formed inside the cylinder block 13 and the cylinder head 14 of the internal combustion engine 10. Then, the water is sent from the water outlet 17 to the radiator 12, returned from the radiator 12 to the internal combustion engine 10 through the water inlet 18, and supplied to the water pump 11 through the thermostat valve 19 and the thermostat housing 20 as flow path control valves. The

  A part of the cooling water supplied to the radiator 12 is supplied to the reservoir tank 21 and returned from the reservoir tank 21 to the thermostat housing 20. Further, a part of the cooling water is supplied from the cylinder block 13 to heat exchange parts such as the oil cooler 22, the turbocharger 23, and the heater 24, and is supplied from the water outlet 17 to the EGR valve 25 as a heat exchange part. In the supply passages to these heat exchange parts 22 to 25, there are provided electromagnetic switching valves 26, 27, 28 for switching between supply and shutoff of the cooling water to the respective parts, and the operation of these switching valves 26, 27, 28. Is controlled by the control unit 30 capable of storing and executing various control processes. The cooling water supplied to each of the heat exchange components 22 to 25 is returned to the thermostat housing 20 via the return passage.

  The bypass flow path R2 bypasses the radiator 12 and accelerates the warm-up completion time by accelerating the temperature rise of the internal combustion engine (cooling water) when the engine is cold before the warm-up is completed. The cooling water is circulated in the 15 and 16. In this bypass flow path R2, the cooling water fed by the water pump 11 is returned from the cylinder block 13 and the cylinder head 14 of the internal combustion engine 10 to the water pump 11 through the bypass passage 31 and the thermostat housing 20, and the radiator. 12 and the thermostat valve 19 are not passed.

  The thermostat valve 19 operates according to the temperature as is well known, and functions as a flow path switching valve that switches between the main cooling water flow path R1 and the bypass flow path R2. That is, in a state after the warm-up in which the temperature of the cooling water exceeds a predetermined set temperature (for example, around 80 degrees), the thermostat valve 19 is opened and the cooling water circulates through the main cooling water flow path R1, so When the engine is cold, the thermostat valve 19 closes the main cooling water passage R1, so that the cooling water circulates in the bypass passage R2.

  In the present embodiment, a flow rate control valve 32 is provided that restricts the flow rate of the cooling water circulating in the bypass flow path R2 while being switched to the bypass flow path R2 by the thermostat valve 19. The flow rate control valve 32 is provided in a bypass passage 31 that branches from the middle of the main cooling water flow path R1 and connects the cylinder head 14 and the thermostat housing 20. For example, when the engine is cold under a predetermined set temperature (for example, around 80 degrees), closing the flow control valve 32 greatly restricts the flow of cooling water circulating in the bypass flow path R2. It becomes a zero flow state that is stopped or stopped.

  In this embodiment, an electromagnetic valve is used as the flow control valve 32, and the operation of the flow control valve 32 is controlled by the control unit 30. However, similarly to the above-described flow path switching valve, a thermostat valve that automatically operates according to the temperature can also be used as the flow control valve 32. In this case, the engine is always in a zero flow state when the engine is cold.

  Referring to FIG. 2, a cylinder head 14 is fixed to an upper portion of a cylinder block 13 in which a cylinder 13 </ b> A is formed, and a water jacket 15 through which cooling water flows through the cylinder head 14 and the cylinder block 13. 16 is formed. A water pump 11 is attached to the cylinder block 13, and a thermostat housing 20 is attached to the cylinder head 14. Further, a water temperature sensor 33 for detecting the temperature of the cooling water is attached to the outer wall of the cylinder head 14 with the temperature sensing portion 34 at the tip thereof facing the water jacket 16 in the cylinder head 14.

  In the state after warm-up shown in FIG. 2 (A), since the cooling water circulates in the water jackets 15 and 16, the temperature of the cooling water in the water jackets 15 and 16 is almost uniform regardless of the position. There is no problem even if the detected value 33 is set as the cooling water temperature as it is. On the other hand, as shown in FIG. 2B, at the time of zero flow when the thermostat valve 19 and the flow rate control valve 32 are closed, the cooling water stays in the water jackets 15 and 16 with almost no circulation. Specifically, the temperature in the vicinity of the outer wall of the cylinder head 14 where the water temperature sensor 33 is installed is lower than that in the vicinity of the combustion chamber or the cylinder 13A that is susceptible to heat from combustion. For this reason, the detected value detected by the water temperature sensor 33 deviates to the lower side than the actual temperature of the cooling water near the cylinder. Therefore, in this embodiment, at such a zero flow, a predicted coolant temperature is calculated for the detected value of the coolant temperature sensor 33 in consideration of the temperature rise of the coolant near the cylinder, and this predicted coolant temperature is set as the coolant temperature. is doing.

  3 to 7 are flowcharts showing the flow of control of the present embodiment, and these routines are stored and executed by the control unit 30 described above. Referring to FIG. 3, in step S <b> 11, it is determined whether the water temperature setting flag FLG_Z-flow is 1. This flag FLG_Z-flow is set by the routine of FIG. 5 and FIG. 6 to be described later, and is set to “1” at the time of zero flow for closing the thermostat valve 19 and the flow rate control valve 32 as when the engine is cold. It is set to “0” at the time of non-zero flow at least to open the flow control valve 32 as after warming up.

  If the water temperature setting flag FLG_Z-flow is 1, it is determined that the flow is in the zero flow state, the process proceeds to step S12, and the temperature of the cooling water in the vicinity of the cylinder is detected with respect to the detected value THW of the water temperature sensor 33 by the process of FIG. A predicted coolant temperature THWcyl in consideration of the rise is obtained, and this coolant temperature predicted value THWcyl is set as the coolant temperature TW. On the other hand, if the water temperature setting flag FLG_Z-flow is 0, it is determined that the state is a non-zero flow state after warming up, and the process proceeds to step S13, and the detected value THW of the water temperature sensor 33 is set as it is as the cooling water temperature TW.

  FIG. 4 shows the calculation process of the predicted coolant temperature THWcyl. In step S31, the detection value THW of the water temperature sensor 33 is read. In step S32, the engine speed Ne is read. In step S33, the fuel injection amount Q is read. Then, in step S34, the estimated coolant temperature THWcyl is calculated by adding the temperature rise of the coolant near the cylinder to the detected value THW of the coolant temperature sensor 33. In this embodiment, the temperature rise is obtained from the engine rotational speed Ne and the fuel injection amount Q. More specifically, as shown in the equation of FIG. 4, the engine rotational speed Ne and the fuel injection per unit time are shown. It is obtained by integrating the multiplication value with the quantity Q and multiplying this integration value by a coefficient C. The coefficient C is a constant set and adapted in advance.

  FIG. 5 shows a zero flow start determination process. In step S41, the detection value THW of the water temperature sensor 33 is read. In step S42, it is determined whether the detected value THW is less than a predetermined start determination value THW_zstart. If the detected value THW is less than the predetermined start determination value THW_zstart, it is determined that zero flow should be started, the process proceeds to step S43, and the water temperature setting flag FLG_Z-flow is set to 1. On the other hand, if the detected value THW is greater than or equal to the start determination value THW_zstart, it is determined that zero flow is not necessary, and the process proceeds to step S44, where the water temperature setting flag FLG_Z-flow is set to zero.

  FIG. 6 shows a zero flow end determination process, and this routine is executed only in the zero flow state. In step S51, the detection value THW of the water temperature sensor 33 is read. In step S52, the cooling water temperature predicted value THWcyl is read. In step S53, the estimated coolant temperature THW2 is calculated by THW2 calculation processing of FIG. In step S54, it is determined whether the predicted coolant temperature THWcyl is greater than or equal to a predetermined first release determination value THW_upper, or whether the estimated coolant temperature THW2 is greater than or equal to a predetermined second release determination value THW_zend. If THWcyl is equal to or higher than THW_upper or THW2 is equal to or higher than THW_zend, the process proceeds to step S55, the water temperature setting flag FLG_Z-flow is set to 0, and the zero flow is canceled / terminated. On the other hand, if THW2 is less than THW_zend and THWcyl is less than THW_upper, the process proceeds to step S55, the water temperature setting flag FLG_Z-flow is set to 1, and zero flow is continued.

  FIG. 7 shows a process for calculating the estimated coolant temperature THW2. In step S61, the detection value THW of the water temperature sensor 33 is read. In step S52, the cooling water temperature predicted value THWcyl is read. In step S63, an estimated coolant temperature THW2 is calculated based on the detected value THW and the estimated coolant temperature THW. Note that the coefficient a and the coefficient b in the expression of step S63 are constants that are adapted and set in advance. As shown in FIG. 8, in this embodiment, the estimated coolant temperature THW2 is set lower than the estimated coolant temperature THWcyl. Therefore, the second release determination value THW_zend for the estimated coolant temperature THW2 is also the cooling It is set lower than the first release determination value THW_upper for the predicted water temperature value THWcyl.

  Thus, at the time of zero flow cancellation, since both the cooling water temperature predicted value THWcyl and the cooling water temperature estimation value THW2 are used and either one reaches the respective cancellation determination value, the zero flow is canceled. Can be performed with high accuracy. In particular, the estimated coolant temperature THW2 is estimated based on the detected value THW and the estimated coolant temperature THWcyl, and when the estimated value THW2 reaches a predetermined second release determination value THW_zend, the zero flow is canceled. As shown in FIG. 8, for example, the release timing of the zero flow can be advanced by a predetermined time ΔT as compared with the case where the release determination is performed based on the detection value THW, and the warm-up operation is performed wastefully. Can be suppressed and energy saving can be achieved.

  As shown in FIG. 9, the cooling water temperature set in this way is used for setting the EGR rate, fuel injection timing, pilot injection amount, fuel injection pressure, as well as determining EGR cooler bypass switching. As shown in the figure, in the engine cold state before the completion of warming up, the lower the coolant temperature, the lower the EGR rate, the more advanced the fuel injection timing, and the higher the exhaust gas temperature, in order to prevent misfires, etc. The pilot injection amount (or post-injection amount) is increased, and the fuel injection pressure is kept low to ensure a long time until the cylinder wall is reached.

DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine 11 ... Radiator 12 ... Water pump 13 ... Cylinder block 14 ... Cylinder heads 15, 16 ... Water jacket 19 ... Thermostat valve (flow-path switching valve)
30 ... Control part 31 ... Bypass passage 32 ... Flow control valve 33 ... Water temperature sensor

Claims (5)

A main cooling water flow path for circulating cooling water between the radiator and the internal combustion engine;
A bypass passage for bypassing the radiator and circulating cooling water inside the internal combustion engine;
A flow path switching valve for switching between the main cooling water flow path and the bypass flow path;
A flow rate control valve for limiting a flow rate of the cooling water circulating in the bypass flow channel in a state where the flow channel switching valve is switched to the bypass flow channel;
A water temperature sensor that outputs a detection value corresponding to the temperature of the cooling water inside the internal combustion engine;
Water temperature setting means for setting the cooling water temperature based on the detection value of the water temperature sensor,
This water temperature setting means obtains a predicted coolant temperature taking into account the temperature rise of the coolant near the cylinder with respect to the detected value of the coolant temperature sensor when the flow rate is limited by the flow control valve, and calculates the predicted coolant temperature as described above. A cooling device for an internal combustion engine, characterized in that the cooling water temperature is set.   2. The cooling apparatus for an internal combustion engine according to claim 1, wherein the water temperature setting means sets the detected value of the water temperature sensor as a cooling water temperature when the flow rate is not limited by the flow control valve. The flow path switching valve is a thermostat valve that shuts off the main cooling water flow path when the engine is cold.
3. The cooling apparatus for an internal combustion engine according to claim 1, wherein the flow rate control valve is closed when the engine is cold.   The cooling apparatus for an internal combustion engine according to any one of claims 1 to 3, wherein the water temperature sensor is attached to an outer wall of a cylinder head spaced from the cylinder.   When the flow rate is limited, the predicted coolant temperature reaches a predetermined first release determination value, or the estimated coolant temperature obtained based on the predicted coolant temperature and the detected value of the water temperature sensor is a predetermined second release. The cooling apparatus for an internal combustion engine according to any one of claims 1 to 4, wherein when the determination value is reached, the flow restriction by the flow control valve is released.

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