JP2011094537A - Cooling device for engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cooling device for an engine that strikes a balance between decrease in cooling loss and knock performance by partially varying the state of heat transfer of the engine in a rational aspect. <P>SOLUTION: The cooling device 1A includes: the engine 50 having a cylinder block 51 where a block side W/J511 is provided and a cylinder head 52 where a gas flow path 525 is provided at a position where the heat transfer from the cylinder block 51 can be controlled; an on-off valve 21 that can change a state of gas circulation in the gas flow path 525 by permitting or prohibiting the gas circulation; and a controller that controls the on-off valve 21 to circulate EGR gas into the gas flow path 525 by circulating a cooling water into the block side W/J511 when an engine operating condition is a low revolution high load. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an engine cooling apparatus.

  Conventionally, an engine is generally cooled by cooling water. Conventionally, an engine that performs exhaust gas recirculation is known. In this regard, Patent Document 1 discloses an exhaust gas recirculation device for an engine having an exhaust gas recirculation passage that has an internal passage formed in a cylinder block so as to be close to the water jacket and along the cylinder row of the engine as a main part. ing. This exhaust gas recirculation device of the engine effectively cools the recirculated exhaust gas and simplifies the piping structure.

JP 2008-82307 A

  By the way, as shown in FIG. 10, an engine, particularly a spark ignition type internal combustion engine, generates a lot of heat not used for net work such as exhaust loss and cooling loss. The reduction of the cooling loss, which accounts for a large proportion of the total energy loss, is a very important factor for improving the thermal efficiency (fuel consumption). However, it is not always easy to reduce cooling loss and effectively use heat, which hinders improvement in thermal efficiency.

  The reason why it is difficult to reduce the cooling loss is that, for example, a general engine is not configured to locally change the state of heat transfer. That is, in a general engine, it is difficult to cool a part that needs to be cooled to a necessary degree and to suppress heat transfer to a part where a lot of cooling loss occurs due to the configuration. Specifically, when changing the state of heat transfer of the engine, generally, the flow rate of the cooling water is changed according to the engine speed by a mechanical water pump driven by the output of the engine. . However, in the water pump that adjusts the flow rate of the cooling water as a whole, even if a variable water pump that makes the flow rate variable is used, the heat transfer state can be locally changed according to the engine operating state. I can't do it.

  In order to reduce the cooling loss, for example, it is conceivable to improve the heat insulation of the engine. In this case, a significant reduction in cooling loss can be expected as shown in FIG. However, in this case, by increasing the heat insulation of the engine, the temperature of the inner wall of the combustion chamber increases at the same time. In this case, there is a problem that knocking is induced when the temperature of the air-fuel mixture rises accordingly. In this regard, in the engine cooling device disclosed in Patent Document 1, while the recirculated exhaust can be effectively cooled, the cooling water is used for cooling the recirculated exhaust, and the recirculated exhaust enhances the heat insulation of the cylinder block. Therefore, from the viewpoint of improving the thermal efficiency, there is a problem in that it is considered that knocking is more easily induced.

  Accordingly, the present invention has been made in view of the above-described problems, and an engine cooling apparatus that can achieve both reduction in cooling loss and knock performance by locally changing the heat transfer state of the engine in a rational manner. The purpose is to provide.

  In order to solve the above problems, the present invention provides a cylinder block provided with a cooling medium passage, an engine having a cylinder head provided with a gas passage at a position where heat transfer from the cylinder block can be suppressed, and the gas passage. A flow changing means capable of changing a gas flow state in the engine, and when the operating state of the engine is a low rotation and high load, in a state in which a cooling medium is circulated through the cooling medium passage, And a control means for controlling the flow changing means so as to circulate the gas.

  Further, the present invention is configured such that the flow changing means is capable of switching a gas that flows through the gas passage between the first gas and a second gas having a temperature lower than the first gas, It is preferable that the control means further controls the flow changing means so that the second gas flows through the gas passage when the engine is operating at a high rotation speed and a high load.

  In the present invention, the gas passage is preferably provided in the periphery of the intake port in the cylinder head.

  In the present invention, it is preferable that the first gas is an exhaust gas recirculated to the engine.

  The present invention further includes a flow stopping means capable of stopping the flow of the first gas in the gas passage, and when the control means performs a large amount of exhaust gas recirculation, the flow of the first gas in the gas passage is reduced. It is preferable that the distribution stop means is further controlled to stop.

  Moreover, it is preferable that this invention is the structure whose said 2nd gas is the gas accumulate | stored in an air storage tank.

  According to the present invention, it is possible to achieve both reduction in cooling loss and knock performance by locally changing the state of heat transfer of the engine in a rational manner.

1 is a diagram schematically showing an engine cooling device (hereinafter simply referred to as a cooling device) 1A. FIG. FIG. 2 is a diagram schematically showing an engine 50 in cross section per cylinder. It is a figure which shows ECU70A typically. It is a figure which shows the classification | category of an engine operation state typically. It is a figure which shows operation | movement of ECU70A with a flowchart. It is a figure which shows the heat transfer rate and surface area ratio of the combustion chamber 55 according to a crank angle. It is a figure which shows typically the cooling device 1B. It is a figure which shows operation | movement of ECU70B with a flowchart. It is a figure which shows operation | movement of ECU70C with a flowchart. It is a figure which shows the breakdown of the general heat balance of a spark ignition type internal combustion engine about the case of a full load, and the case of a partial load, respectively. It is a figure respectively shown about the case of the base engine used as the standard for the inner wall temperature and heat transmittance of a cylinder, and the case where heat insulation is improved. In addition, in FIG. 11, as the case where heat insulation is improved, the case where the material is changed as the wall thickness of the cylinder is increased and the case where air insulation with higher heat insulation is performed are shown.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings.

  A cooling device 1A shown in FIG. 1 is mounted on a vehicle (not shown), and includes a water pump (hereinafter referred to as W / P) 11, a radiator 12, a thermostat 13, a flow rate control valve 14, an on-off valve 21, An exhaust gas recirculation device 30, an exhaust pipe 40, and an engine 50 are provided. W / P11 is a cooling medium pumping means, which is a variable W / P that pumps the cooling water that is the cooling medium and makes the flow rate of the cooling water pumped variable. Cooling water pumped by the W / P 11 is supplied to the engine 50.

  The engine 50 includes a cylinder block 51 and a cylinder head 52. The cylinder block 51 is formed with a block-side water jacket (hereinafter referred to as block-side W / J) 511 that is a first cooling medium passage. The block side W / J 511 forms a plurality (two in this case) of cooling systems in the cylinder block 51. On the other hand, the cylinder head 52 is formed with a head side water jacket (hereinafter referred to as head side W / J) 521 which is a second cooling medium passage. The head side W / J 521 forms a plurality (four in this case) of cooling systems in the cylinder head 52. Specifically, the cooling water pumped by the W / P 11 is supplied to the block side W / J 511 and the head side W / J 521.

In this regard, the cooling device 1A has a plurality of cooling water circulation paths.
As the cooling water circulation path, for example, there is a block side circulation path C1 which is a circulation path in which the block side W / J 511 is incorporated. The cooling water flowing through the block-side circulation path C1 is discharged from the W / P 11 and then flows through the block-side W / J 511 and further through the thermostat 13 or through the radiator 12 and the thermostat 13. To come back. The radiator 12 is a heat exchanger, and cools the cooling water by exchanging heat between the circulating cooling water and the air. The thermostat 13 switches the distribution route communicating with the W / P 11 from the entrance side. Specifically, the thermostat 13 sets the flow path that bypasses the radiator 12 when the coolant temperature is lower than a predetermined value, and sets the flow path that flows through the radiator 12 when the temperature of the cooling water is equal to or higher than the predetermined value.

  Further, as the cooling water circulation path, for example, there is a head side circulation path C2 which is a circulation path in which the head side W / J 521 is incorporated. The cooling water flowing through the head-side circulation path C2 is discharged from the W / P 11, and then flows through the flow rate control valve 14 and the head-side W / J 521, and further passes through the thermostat 13 or the radiator 12 and the thermostat 13. Via W / P11. The flow rate adjusting valve 14 is provided in a portion of the head-side circulation path C2 after the circulation paths C1 and C2 are branched and a portion upstream of the cylinder head 52.

The flow rate adjusting valve 14 is a cooling capacity adjusting means capable of adjusting the cooling capacity of the cylinder head 52. In this regard, the flow rate adjusting valve 14 specifically adjusts the cooling capacity of the cylinder head 52 by adjusting the overall flow rate of the cooling water flowing through the head side W / J 521. It is a means.
Further, the flow rate adjusting valve 14 provided in this way serves as a cooling capacity adjusting means capable of suppressing the cooling capacity of the cylinder head 52 without suppressing the cooling capacity of the cylinder block 51. Further, the flow rate adjusting valve 14 thus provided increases the cooling capacity of the cylinder block 51 when the flow rate of the cooling water flowing through the head side W / J 521 is adjusted so as to suppress the cooling capacity of the cylinder head 52. Thus, the cooling capacity adjusting means is capable of adjusting the flow rate of the cooling water flowing through the block side W / J511.

  In the cooling device 1A, the cooling water flowing through the block-side circulation path C1 is not circulated through the head-side W / J 521 until one cycle after the cooling water is pumped by the W / P 11. Further, in the cooling device 1A, the cooling water flowing through the head-side circulation path C2 is not circulated through the block side W / J 511 until one cycle after the cooling water is pumped by the W / P 11. That is, in the cooling device 1A, the block side W / J511 and the head side W / J521 are incorporated in different coolant circulation paths.

  The exhaust gas recirculation device 30 includes an EGR pipe 31 and an EGR flow rate adjustment valve 32, and causes the engine 50 to recirculate exhaust gas. The EGR pipe 31 communicates the exhaust pipe 40 and an intake system (not shown) of the engine 50, and forms an exhaust gas recirculation path C3. The EGR flow rate adjustment valve 32 adjusts the flow rate of exhaust gas recirculated to the engine 50 (hereinafter referred to as EGR gas). The exhaust gas recirculation path C3 is provided with an EGR branch path C4 as a branch path. In this regard, the cylinder head 52 is provided with a gas passage 525, and the gas passage 525 is incorporated in the EGR branch path C4. That is, the EGR branch path C4 is a path for branching and introducing the EGR gas, which is the first gas, into the gas passage 525. In addition, an open / close valve 21 is provided in the EGR branch path C4. The on-off valve 21 is a flow changing means capable of changing the flow state of the gas in the gas passage 525, and more specifically, by permitting or prohibiting the flow of gas in the gas passage 525, the gas passage This is a flow changing means capable of changing the gas flow state at 525.

  Next, the engine 50 will be described more specifically. As shown in FIG. 2, a cylinder 51 a is formed in the cylinder block 51. A piston 53 is provided in the cylinder 51a. A cylinder head 52 is fixed to the cylinder block 51 via a gasket 54 having high heat insulating properties. The gasket 54 suppresses heat transfer from the cylinder block 51 to the cylinder head 52 by its high heat insulating property. The cylinder 51a, the cylinder head 52, and the piston 53 form a combustion chamber 55. The cylinder head 52 is formed with an intake port 52 a that guides intake air to the combustion chamber 55 and an exhaust port 52 b that discharges combustion gas from the combustion chamber 55. A spark plug 56 is provided in the cylinder head 52 so as to face the substantially upper center of the combustion chamber 55.

  Specifically, the block side W / J 511 includes a plurality of portions W / J 511a and portions W / J 511b which are first partial cooling medium passages. The portion W / J 511a is provided in the peripheral portion and the upper portion of the cylinder 51a. The portion W / J 511a is provided so as to correspond to a portion of the wall surface of the cylinder 51a where the intake air flowing into the cylinder hits. In this regard, the engine 50 is an engine that generates a normal tumble flow in the cylinder in this embodiment, and more specifically, the portion that the intake air that has flowed into the cylinder hits is the upper part of the wall surface of the cylinder 51a and the exhaust side. It is part of. The portion W / J511b is provided in the peripheral portion and the lower portion of the cylinder 51a. The portions W / J 511a and 511b can be formed, for example, by forming a cylindrical space around the cylinder 51a and inserting sleeves 57 and 58 each having a U-shaped inner groove in the space. The parts W / J511a and 511b are separately incorporated in two cooling systems formed by the block side W / J511.

  Specifically, the head side W / J 521 includes a plurality of portions W / J 521a, a portion W / J 521b, a portion W / J 521c, and a portion W / J 521d which are second partial cooling medium passages. The portion W / J 521a is provided at the peripheral portion of the intake port 52a, the portion W / J 521b is provided at the peripheral portion of the exhaust port 52b, and the portion W / J 521c is provided at the peripheral portion of the spark plug 56. Further, the portion W / J 521d is provided for cooling between the intake / exhaust valves 52a and 52b and other portions. The portion W / J521a to the portion W / J524d are separately incorporated in the four cooling systems formed by the head side W / J521.

  The gas passage 525 is provided at a position where heat transfer from the cylinder block 51 can be suppressed. Specifically, the gas passage 525 is provided in the periphery of the intake port 52 a in the cylinder head 52, and more specifically, in the portion of the cylinder head 52 between the intake port 52 a and the cylinder block 51. Is provided. In this respect, the gas passage 525 is provided in the peripheral portion of the intake port 52a so as to avoid the peripheral portion of the exhaust port 52b having a high heat load and the peripheral portion of the spark plug 56.

  Further, the cooling device 1A includes an ECU (Electronic Control Unit) 70A shown in FIG. The ECU 70A includes a microcomputer including a CPU 71, a ROM 72, a RAM 73, and the like, and input / output circuits 75 and 76. These components are connected to each other via a bus 74. The ECU 70A includes a crank angle sensor 81 for detecting the rotational speed of the engine 50, an air flow meter 82 for measuring the intake air amount, an accelerator opening sensor 83 for detecting the accelerator opening, cooling water Various sensors and switches such as a water temperature sensor 84 for detecting the temperature of the water are electrically connected. In this regard, the load of the engine 50 is detected by the ECU 70A based on the outputs of the air flow meter 82 and the accelerator opening sensor 83. Various control objects such as the W / P 11, the flow rate control valve 14, the on-off valve 21, and the EGR flow rate control valve 32 are electrically connected to the ECU 70A.

  The ROM 72 is configured to store a program in which various processes executed by the CPU 71 are described, map data, and the like. When the CPU 71 executes processing while using the temporary storage area of the RAM 73 based on a program stored in the ROM 72, various control means, determination means, detection means, calculation means, etc. are functional in the ECU 70A. To be realized.

In this regard, in the ECU 70A, specifically, for example, a control unit that performs heat transfer suppression control that is control for suppressing heat transfer from the cylinder block 51 to the cylinder head 52 is functionally realized. Specifically, the control means is realized to perform heat transfer suppression control when the engine operating state is a high load, and more specifically, the heat transfer suppression control when the engine operating state is a low rotation high load. Is realized to do. Further, the control means is realized to perform heat transfer suppression control by controlling the on-off valve 21 so as to permit the flow of EGR gas (that is, by opening the on-off valve 21).
The control means is basically realized to control the EGR flow rate adjustment valve 32 so as to permit the flow of the EGR gas.
In addition, the control means controls the W / P 11 and the flow rate control valve 14 and performs control for establishing the operation of the engine 50 not only when the engine operating state is a high load but also in other operating states. To be realized.

  In this respect, the engine operation state is specifically classified into six categories shown in FIG. 4 depending on whether the engine 50 is in cold operation or engine start in addition to the rotational speed and load of the engine 50. It is classified from D1 to D6. When the control means performs control, specifically, as shown below, a request to be satisfied is set for each of the sections D1 to D6, and a control guideline for satisfying the set request is defined.

First, when the engine operating state is an idle state corresponding to the section D1, two requirements are set, namely, a combustion speed improvement by intake air temperature increase and an exhaust temperature increase for catalyst activity. In accordance with this, two control guidelines are set, namely, the temperature rise of the intake port 52a and the upper part of the cylinder 51a and the temperature rise of the exhaust port 52b.
In this regard, in order to increase the temperature of the intake port 52a, for example, the flow rate control valve 14 can be closed or opened with a small opening, or the on-off valve 21 can be opened. In order to increase the temperature of the upper portion of the cylinder 51a, for example, the W / P 11 can be stopped or driven with a low discharge amount. In order to raise the temperature of the exhaust port 52b, for example, the flow control valve 14 can be closed or opened with a small opening.

In addition, when the engine operating state is a light load corresponding to the category D2, two requirements are set: improvement in thermal efficiency (reduction of cooling loss) and improvement in combustion speed due to intake air temperature rise. In accordance with this, two control guidelines are defined: heat insulation of the cylinder head 52 and temperature rise of the intake port 52a and the upper part of the cylinder 51a.
In this regard, in order to insulate the cylinder head 52, for example, the flow rate control valve 14 can be closed or opened with a small opening, or the on-off valve 21 can be opened. In order to increase the temperature of the intake port 52a, for example, the flow rate control valve 14 can be closed or opened with a small opening, or the on-off valve 21 can be opened. In order to raise the temperature of the upper portion of the cylinder head 52, for example, the W / P 11 can be stopped or driven with a low discharge amount.

Further, when the engine operating state is a low rotation and high load corresponding to the section D3, a request for reducing knocking and improving thermal efficiency (reducing cooling loss) is set. Further, control guidelines for cooling the intake port 52a and the upper part of the cylinder 51a and insulating the cylinder head 52 are determined.
In this regard, in order to cool the intake port 52a, for example, the flow rate control valve 14 can be fully opened or opened with a large opening, or the on-off valve 21 can be closed. In order to cool the upper portion of the cylinder 51a, for example, the W / P 11 can be driven with a maximum discharge amount or a high discharge amount applied during engine operation. In order to insulate the cylinder head 52, for example, the flow rate control valve 14 can be closed or opened with a small opening, or the on-off valve 21 can be opened.

Further, when the engine operating state is a high rotation and high load corresponding to the section D4, two requirements of ensuring reliability and reducing knocking are set. In accordance with this, two control guidelines for cooling the periphery of the spark plug 56, between the intake and exhaust valves 52a and 52b, and the exhaust port 52b, and cooling the intake port 52a are defined.
In this regard, in order to cool the periphery of the spark plug 56, the space between the intake / exhaust valves 52a and 52b, and the exhaust port 52b, for example, the flow control valve 14 can be fully opened. In order to cool the intake port 52a, for example, the flow control valve 14 can be fully opened or the on-off valve 21 can be closed. Moreover, about W / P11, it can drive with the maximum discharge amount applied, for example at the time of engine operation.

Further, when the engine corresponding to the section D5 is cold, two requirements are set, namely, acceleration of engine warm-up and improvement of the combustion speed by intake air temperature rise. In response to this, two control guidelines are set for promoting heat transfer of the cylinder head 52 and for increasing the temperature of the intake port 52a and the upper portion of the cylinder 51a.
In this regard, in order to promote heat transfer of the cylinder head 52, for example, the flow rate control valve 14 can be opened in consideration of the large contribution of heat received by the cooling water in the cylinder head 52. In order to increase the temperature of the intake port 52a, for example, the flow rate control valve 14 can be closed or opened with a small opening, or the on-off valve 21 can be opened. In order to increase the temperature of the upper portion of the cylinder 51a, for example, the W / P 11 can be stopped or driven with a low discharge amount.

At the time of starting the engine corresponding to the category D6, two requirements are set for improving ignitability and promoting fuel vaporization. In accordance with this, two control guidelines are set, namely, the temperature rise of the intake port 52a and the temperature rise around the spark plug 56 and the upper portion of the cylinder 51a.
In this regard, in order to increase the temperature of the intake port 52a, for example, the flow rate control valve 14 can be closed or opened with a small opening, or the on-off valve 21 can be opened. In order to increase the temperature around the spark plug 56, for example, the flow rate control valve 14 can be closed or opened with a small opening. In order to increase the temperature of the upper portion of the cylinder 51a, for example, the W / P 11 can be stopped or driven with a low discharge amount.

On the other hand, in the cooling device 1A, in consideration of the consistency and simplification of the overall control, the control means more specifically performs the following control on the W / P 11, the flow rate adjustment valve 14, and the on-off valve 21. Realized to do.
In other words, the control means includes a case where the engine operating state is an idle state corresponding to the section D1, a case where the engine operating state is a light load corresponding to the section D2, a time when the engine is cold corresponding to the section D5, and a section D6. At the time of starting the engine corresponding to the above, the control for stopping the W / P 11 is performed, the control for closing the flow rate adjusting valve 14 is performed, and the on-off valve is further circulated through the gas passage 525. 21 is realized.
The control means performs control for driving the W / P 11 at a high discharge amount when the engine operating state is a low rotation and high load corresponding to the section D3, and closes the flow rate control valve 14 or Control is performed to open the valve in a mode capable of suppressing boiling of the cooling water in the cylinder head 52 (hereinafter referred to as boiling suppression mode) while suppressing the circulation of the cooling water to the cylinder head 52, and further, the gas passage 525. The on-off valve 21 is controlled so as to circulate the EGR gas.
In addition, when the engine operating state is a high rotation and high load corresponding to the section D4, the control means performs control for driving the W / P 11 with the maximum discharge amount applied at the time of engine operation, and the flow rate adjusting valve 14 Is implemented to control the on-off valve 21 so as to stop the flow of the EGR gas in the gas passage 525.

  In this regard, when the engine operating state is a low rotation and high load corresponding to the section D3, in performing the control for opening the flow rate adjustment valve 14 in the boiling suppression mode, the control means specifically includes, for example, any The flow control valve 14 is opened at the minimum necessary opening that can suppress the boiling of the cooling water under the conditions, the temperature of the cooling water flowing through the cylinder head 52 is detected or estimated, and the temperature of the cooling water is adjusted. Based on this, it is possible to open the flow rate control valve 14 intermittently, or to open the flow rate control valve 14 at a predetermined rotational speed or higher. Thereby, in suppressing the cooling capacity of the cylinder head 52, it is possible to suppress the flow rate adjusting valve 14 from being opened more than necessary while suppressing the boiling of the cooling water.

In the cooling device 1A, under the control of the control means, in the section D3, the flow rate control valve 14 reduces the flow rate of the cooling water flowing through the cylinder head 52 in this way, thereby the flow rate of the cooling water flowing through the engine 50. Is reduced locally.
In the cooling device 1A, the cooling capacity of the cylinder head 52 is suppressed by suppressing the flow of the cooling water to the cylinder head 52 when the flow rate adjustment valve 14 is not fully opened. In this regard, in the cooling device 1A, more specifically, the cooling capacity of the cylinder head 52 is suppressed when the flow control valve 14 is closed or the flow control valve 14 is opened in a boiling suppression mode. Will be.
In this case, the flow rate of the cooling water flowing through the block side W / J 511 is adjusted so as to increase the cooling capacity of the cylinder block 51. In the cooling device 1A, the block side W / The control means is controlled to control the on-off valve 21 so that the EGR gas is circulated through the gas passage 525 in a state where the cooling water is circulated through J511.

  Next, processing performed by the ECU 70A will be described using the flowchart shown in FIG. The ECU 70A determines whether or not it is at the time of engine start (step S1). If the determination is affirmative, the ECU 70A opens the on-off valve 21 (step S21A) and stops W / P11 (step S22). The EGR flow rate adjustment valve 32 is basically controlled so as to permit the flow of EGR gas. On the other hand, if a negative determination is made in step S1, ECU 70A determines whether or not the engine is cold (step S5). Whether or not the engine is cold can be determined, for example, based on whether or not the cooling water temperature is a predetermined value (for example, 75 ° C.) or less. If it is affirmation determination by step S5, it will progress to step S21A. On the other hand, if a negative determination is made in step S5, ECU 70A detects the rotational speed and load of engine 50 (step S11).

  Subsequently, the ECU 70A determines a classification corresponding to the detected rotation speed and load (from step S12 to S14). Specifically, if the corresponding category is category 1, the process advances from step S12 to step S21A. If the corresponding category is category 2, the process proceeds from step S13 to step S21A. On the other hand, if the corresponding category is category 3, the process proceeds from step S14 to step S31A. At this time, the ECU 70A opens the on-off valve 21 (step S31A), drives the W / P 11 with a high discharge amount (step S32), and further closes the flow rate adjustment valve 14 (step S33). If the corresponding category is category 4, control proceeds from step S14 to step S41A. At this time, the ECU 70A closes the on-off valve 21 (step S41A), drives the W / P 11 with the maximum discharge amount applied during engine operation (step S42), and further opens the flow rate control valve 14 (step S43). ).

  Next, the effect of the cooling device 1A will be described. Here, the heat transfer coefficient and the surface area ratio of the combustion chamber 55 according to the crank angle of the engine 50 are as shown in FIG. As shown in FIG. 6, it can be seen that the heat transfer coefficient increases near the top dead center of the compression stroke. As for the surface area ratio, it can be seen that the surface area ratios of the cylinder head 52 and the piston 53 increase near the top dead center of the compression stroke. Therefore, it can be seen that the influence of the temperature of the cylinder head 52 is large on the cooling loss. On the other hand, knocking depends on the compression end temperature, and it can be seen that the surface area ratio of the cylinder 51a is large in the intake compression stroke that affects the compression end temperature. Therefore, it can be seen that the influence of the temperature of the cylinder 51a is large for knocking.

On the other hand, in the cooling device 1 </ b> A, based on such knowledge, when the operating state of the engine 50 is a low rotation and high load, the EGR gas is circulated through the gas passage 525 by opening the on-off valve 21. Thus, by suppressing the heat transfer from the cylinder block 51 to the cylinder head 52, it is possible to suppress the occurrence of more cooling loss in the cylinder head 52, thereby reducing the cooling loss.
Further, in the cooling device 1A, when the operating state of the engine 50 is a low rotation and high load, the cooling water is circulated to the block side W / J 511 by further driving the W / P 11 and closing the flow rate adjusting valve 14. In this state, the on-off valve 21 is opened. And since intake air can be cooled by this, generation | occurrence | production of knocking can also be suppressed.

  That is, in the cooling device 1A, the state of heat transfer is locally varied in a rational manner based on the above-described knowledge to insulate the cylinder head 52 (reduce cooling loss) and to cool the cylinder block 51. Therefore, the occurrence of knocking can also be suppressed. And heat efficiency can be improved by making reduction of a cooling loss and knock performance compatible in this way.

  Further, in the cooling device 1A, when the operating state of the engine 50 is a low rotation and high load, the cooling of the cylinder head 52 by the cooling water is stopped by closing the flow rate adjustment valve 14. This also makes it possible to reduce the cooling loss. In this regard, in the cooling device 1A, the heat insulation effect of the engine 50 can be enhanced by allowing the EGR gas to flow through the gas passage 525, whereby the cooling water for the head side W / J 521 can be provided without providing the gas passage 525. Compared with the case where distribution is stopped, the cost for improving the thermal efficiency can be increased.

  Further, in the cooling device 1A, when the operating state of the engine 50 is in an idle state, the on-off valve 21 is opened and the driving of the W / P 11 is stopped, thereby increasing the temperature of the intake air and cooling the engine 50. Stop. As a result, it is possible to reduce the unburned loss and the cooling loss by improving the combustion speed. In addition, since the cooling of the exhaust port 52b can be stopped by this, the exhaust temperature can be kept high and the active state of the catalyst can be maintained.

  Further, in the cooling device 1A, when the operating state of the engine 50 is a light load, the opening / closing valve 21 is opened and the driving of the W / P 11 is stopped. As a result, unburned loss and cooling loss can be reduced. In addition, this can improve combustion, thereby expanding the EGR operation region and the lean burn operation region.

  In the cooling device 1A, when the operating state of the engine 50 is a high rotation and high load, the on-off valve 21 is closed, the W / P 11 is driven, and the flow rate control valve 14 is opened, The flow of EGR gas in the gas passage 525 is stopped, and the cooling water is circulated to the block side W / J511 and the head side W / J521. As a result, each part of the engine can be cooled, so that reliability can be ensured and occurrence of knocking can be suppressed.

Further, in the cooling device 1A, when the engine is cold, the on-off valve 21 is opened and the driving of the W / P 11 is stopped, so that unburned loss and cooling loss can be reduced. Can be promoted.
Further, in the cooling device 1A, by opening the on-off valve 21 and stopping the driving of the W / P 11 when the engine is started, it is possible to improve ignitability and promote fuel vaporization.

  That is, the cooling device 1A can improve the thermal efficiency mainly at the time of a low rotation and a high load, but can establish the operation of the engine 50 in other operation states, and as a result, only in a specific operation state. In addition, the thermal efficiency can be improved even when the engine 50 is operated as usual.

  Further, in the cooling device 1A, by using the EGR gas as the gas flowing through the gas passage 525, the exhaust recirculation device 30 and the parts (for example, the EGR pipe 31) can be shared. For this reason, in the cooling device 1A, the number of parts can be reduced as compared with the case where another gas is used as the gas flowing through the gas passage 525, and thus the cost can be reduced. Further, in the cooling device 1A, the EGR gas is circulated through the gas passage 525 provided in the peripheral portion of the intake port 525 having a relatively low heat load, thereby ensuring the reliability of the engine 50 and cooling the EGR gas. it can.

  As shown in FIG. 7, the cooling device 1B according to the present embodiment includes a switching valve 22A instead of the on-off valve 21, a point further including an air storage tank 25, and an ECU 70B instead of the ECU 70A. Except for the point provided, it is substantially the same as the cooling device 1A. The ECU 70B is substantially the same as the ECU 70A except that the control means is realized as shown below and that the switching valve 22A is electrically connected as a control target instead of the on-off valve 21. It has become. For this reason, the illustration of the ECU 70B is omitted.

The air storage tank 25 is a pressure accumulation tank, and specifically, compressed air is accumulated by an air compressor (not shown). The compressed air accumulated in the air storage tank 25 is a second gas having a temperature lower than that of the EGR gas.
The switching valve 22A is provided in the EGR branch path C4, and an air storage tank 25 is connected to the switching valve 22A. The switching valve 22A is a flow changing means configured to be able to switch the gas to be passed through the gas passage 525 between the EGR gas and the compressed air when changing the gas flow state in the gas passage 525.

  The ECU 70 </ b> B is realized such that the control means controls the switching valve 22 </ b> A instead of the on-off valve 21 when changing the gas flow state in the gas passage 525. In this regard, in the ECU 70B, the control means is realized to control the switching valve 22A so that the EGR gas is circulated through the gas passage 525 when the engine operating state is other than the high rotation and high load. On the other hand, in the ECU 70B, the control means is realized to control the switching valve 22A so that the compressed air is circulated through the gas passage 525 when the operating state of the engine 50 is a high rotation and high load.

  Next, the operation of the ECU 70B will be described using the flowchart shown in FIG. This flowchart is the same as the flowchart shown in FIG. 5 except that steps S21B, S31B, and S41B are provided instead of steps S21A, S31A, and S41A. Further, steps S21B and S31B are the same as the ECU 70A in that the EGR gas is circulated through the gas passage 525, although the switching valve 22A is a control target. For this reason, step S41B will be particularly described here. When the engine operating state is high rotation and high load, the ECU 70B switches the switching valve 22A to the compressed air side (step S41B), drives the W / P 11 (step S42), and further opens the flow rate adjustment valve 14 (step S42). Step S43).

  Next, the effect of the cooling device 1B will be described. In the cooling device 1 </ b> B, when the engine operating state is high rotation and high load, the switching valve 22 </ b> A is switched to the compressed air side, whereby compressed air having a temperature lower than that of the EGR gas can be supplied to the gas passage 525. For this reason, in the cooling device 1B, the cooling of each part of the engine can be promoted, and as a result, the reliability can be more suitably ensured. This also makes it possible to reduce the intake air temperature in the cooling device 1B, thereby further suppressing the occurrence of knocking. Furthermore, in the cooling device 1B, since compressed air is supplied from the air storage tank 25, gas can be suitably supplied to the gas passage 525 in that the compressed air can be supplied to the gas passage 525 quickly. As described above, the cooling device 1B can improve the thermal efficiency mainly at the time of low rotation and high load, and further at the time of high rotation and high load, which is particularly concerned about the decrease in reliability and occurrence of knocking as another operating state. The operation of the engine 50 can be favorably established in that the reliability and knock performance can be improved.

  The cooling device 1C according to the present embodiment is substantially the same as the cooling device 1B except that a switching valve 22B is provided instead of the switching valve 22A and an ECU 70C is provided instead of the ECU 70B. The switching valve 22B is substantially the same as the switching valve 22A except that the switching valve 22B is configured to permit or prohibit the gas flow in the gas passage 525. The ECU 70C is substantially the same as the ECU 70B except that the control means is realized as described below. For this reason, illustration of the cooling device 1C and the ECU 70C is omitted.

  In the ECU 70C, when the control means performs a large amount of exhaust gas recirculation (hereinafter referred to as a large amount of EGR), the ECU 70C further functions to control the switching valve 22B so as to stop the flow of the EGR gas in the gas passage 525. Realized. In this regard, in the present embodiment, the switching valve 22B is a flow changing unit, and at the same time, is a flow stopping unit capable of stopping the flow of EGR gas in the gas passage 525. For example, it is possible to further include a flow stopping means for permitting or prohibiting the flow of the gas in the gas passage 525 without changing the switching valve 22A to the switching valve 22B. Further, in the cooling device 1A described in the first embodiment, it is possible to apply the same change to the control means after using the on-off valve 21 as the flow stopping means.

  Next, the operation of the ECU 70C will be described using the flowchart shown in FIG. This flowchart is the same as the flowchart shown in FIG. 8 except that steps S2, S3 and S4 are added and that steps S21C, S31C and S41C are provided instead of steps S21B, S31B and S41B. It has become a thing. Steps S21C, S31C, and S41C are not substantially changed except that the switching valve 22B is a control target, and therefore, here, steps S2, S3, and S4 will be particularly described. Following the negative determination in step S1, the ECU 70C determines whether or not a condition for performing a large amount of EGR (a large amount of EGR condition) is satisfied (step S2). If the determination is negative, the switching valve 22B is opened (step S4), and then the process proceeds to step S5. On the other hand, if the determination in step S2 is affirmative, the ECU 70C closes the switching valve 22B (step S3), and then proceeds to step S5.

  Next, the effect of the cooling device 1C will be described. Here, a large amount of EGR (for example, when the EGR rate is 60% or more) is performed in order to improve exhaust emission at a high level in view of, for example, recent serious environmental problems. On the other hand, in the cooling device 1C, when the mass EGR condition is satisfied, the switching valve 22B is closed to ensure the amount of EGR gas necessary for the mass EGR. For this reason, in the cooling device 1C, the operation of the engine 50 can be more preferably established in that the deterioration of exhaust emission that may occur when the required amount of EGR gas cannot be ensured can be further suppressed.

The embodiment described above is a preferred embodiment of the present invention. However, the present invention is not limited to this, and various modifications can be made without departing from the scope of the present invention.
For example, in the above-described embodiment, the case where W / P 11 is the cooling medium pumping means has been described because it is suitable for establishing the operation of the engine 50. However, the present invention is not necessarily limited to this, and the cooling medium pumping means may be, for example, a mechanical W / P driven by the output of the engine.

In the above-described embodiment, an example of control performed by the control unit based on the above-described control guideline when the operation of the engine 50 is established has been described.
However, the present invention is not necessarily limited to this, and the control means may perform other appropriate control in establishing the engine operation. In this regard, for example, the first cooling medium passage provided in the cylinder block includes a plurality of first partial cooling medium passages, and the second cooling medium passage provided in the cylinder head is the second partial cooling medium passage. A plurality of partial cooling capacity adjusting means corresponding to each of the first and second partial cooling medium passages, and based on the above control guidelines, the cooling medium pressure feeding means and the cooling capacity adjusting means Alternatively, the flow rate changing means and the partial cooling capacity adjusting means may be appropriately controlled. Thereby, the operation of the engine can be more preferably established.

  In addition, it is reasonable to realize the control means mainly by each ECU 70 that controls the engine 50, but it may be realized by, for example, other electronic control devices, hardware such as a dedicated electronic circuit, or a combination thereof. . The control means may be realized in a distributed control manner by, for example, hardware such as a plurality of electronic control devices and a plurality of electronic circuits, or a combination of electronic control devices and hardware such as electronic circuits.

1 Cooling device 11 W / P
12 Radiator 13 Thermostat 14 Flow Control Valve 21 Open / Close Valve 22 Switching Valve 30 Exhaust Recirculation Device 40 Exhaust Pipe 50 Engine 51 Cylinder Block 511 Block Side W / J
52 Cylinder head 521 Head side W / J
525 Gas passage 70 ECU

Claims (6)

An engine having a cylinder block provided with a cooling medium passage, and a cylinder head provided with a gas passage at a position where heat transfer from the cylinder block can be suppressed;
A flow changing means capable of changing a flow state of the gas in the gas passage;
Control for controlling the flow changing means to flow the first gas through the gas passage while the cooling medium is passed through the cooling medium passage when the engine is operating at a low rotation and high load. And an engine cooling device. The engine cooling device according to claim 1,
The flow changing means is configured to be able to switch a gas to flow through the gas passage between the first gas and a second gas having a temperature lower than that of the first gas,
An engine cooling apparatus, wherein the control means further controls the flow changing means to flow the second gas through the gas passage when the operating state of the engine is a high rotation and high load. The engine cooling device according to claim 2,
An engine cooling apparatus in which the gas passage is provided in the periphery of the intake port in the cylinder head. The engine cooling device according to any one of claims 1 to 3,
An engine cooling apparatus, wherein the first gas is exhaust gas recirculated to the engine. The engine cooling device according to claim 4,
Further comprising a flow stopping means capable of stopping the flow of the first gas in the gas passage,
An engine cooling apparatus that further controls the flow stopping means to stop the flow of the first gas in the gas passage when the control means performs a large amount of exhaust gas recirculation. The engine cooling device according to any one of claims 2 to 5,
The engine cooling device, wherein the second gas is a gas stored in an air storage tank.

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