JP2014109208A - Internal combustion engine for automobile - Google Patents

Abstract

PROBLEM TO BE SOLVED: To cool an EGR cooler accurately according to its operation state.SOLUTION: An EGR gas is allowed to flow back to an intake passage at an engine speed higher than an idling minimum speed. A coolant is supplied to the EGR cooler 14 from an EGR cooler supply pipe 33, and is discharged from an EGR cooler drain pipe 34. The EGR cooler supply pipe 33 is connected to a portion near an inlet of a first coolant passage 17 for cooling a cylinder block 1, and the EGR cooler supply pipe 33 is connected to an upper tank 22 of a radiator 21. A flow resistance (pressure loss) of the EGR cooler supply pipe 33 is set to the magnitude such that the coolant flows when the engine speed reaches an EGR possible speed and a coolant pressure of the first coolant passage 17 becomes high. Accordingly, when the engine speed reaches the EGR possible speed, the coolant automatically flows into the EGR cooler 14, and the EGR cooler can be cooled sufficiently.

Description

  The present invention relates to an automatic internal combustion engine equipped with an EGR device in which EGR gas is cooled by a water-cooled EGR cooler.

  In recent years, internal combustion engines for automobiles are often provided with an EGR device that recirculates exhaust gas to the intake system, and the EGR device is often provided with a water-cooled EGR cooler to cool the EGR gas.

  The cooling of the EGR cooler is incorporated in a part of a cooling system for cooling the cylinder block and the cylinder head, and is cooled by the cooling water discharged from the water pump. The cooling system of the internal combustion engine is equipped with a radiator, and the cooling water that is received by cooling the engine body is cooled by the radiator and returns to the engine body again, but the cooling system prevents the cooling water from flowing to the radiator during warm-up operation. Is provided with a thermo valve so that when the temperature of the cooling water becomes higher than a certain level, the thermo valve is opened and the cooling water circulates through the radiator.

  Patent Document 1 discloses that a bypass pipe is provided in a circulation path passing through a radiator so as to straddle a thermo valve, and an EGR cooler is disposed in the bypass pipe. That is, in Patent Document 1, the water flow to the radiator and the water flow to the EGR cooler are completely interlocked, and an amount of cooling water corresponding to the opening of the thermo valve is also passed to the EGR cooler.

  Since the cooling water flows through the engine body even during the warm-up operation, it is necessary to raise the temperature of the cooling water as soon as possible in order to shorten the warm-up time. However, if the cooling water flows through the EGR cooler when the temperature of the EGR passage through which the EGR gas passes is lower than the temperature of the cooling water, the heat of the cooling water heated in the engine body is dissipated to the EGR passage and the warm-up time However, the fuel consumption will be worsened. On the other hand, if water flow to the EGR cooler is interlocked with the thermo valve as in Patent Document 1, it can be said that water is not passed through the EGR passage during the warm-up operation, which can contribute to shortening the warm-up time.

JP 2007-255257 A (particularly FIG. 3)

  Now, looking at the relationship between the radiator and the EGR device, the two are not directly related to each other, and the radiator operates simply according to the temperature of the cooling water, whereas the EGR device operates mainly with the rotation speed and load as variables. ing. Therefore, in the idling state in which the automobile is stopped, the EGR device is generally stopped, but when the temperature of the cooling water is raised to a predetermined temperature or higher, water is passed through the radiator.

  For this reason, in Patent Document 1 in which the flow of water to the EGR cooler is linked to the flow of water to the radiator, the EGR cooler is not necessary for the EGR cooler, and the EGR cooler is overcooled. A condition may occur. In addition, even when the automobile is running, the EGR gas recirculation stops when the engine rotates at a low speed as in the case of decelerating the foot from the accelerator pedal. However, in Patent Document 1, such a case also occurs in the EGR cooler. Since the cooling water continues to flow, it can be said that the EGR cooler may be excessively cooled. That is, Patent Document 1 is concerned that there is a possibility that the EGR cooler cannot be cooled without excess or deficiency, and this is one of the problems of Patent Document 1.

  Further, in Patent Document 1, the EGR cooler is set so that the engine body is cooled to a high temperature and the cooling water flows in. Since the highest temperature cooling water flows in, the EGR cooler travels while operating the EGR device. In such a state, the EGR cooler may be insufficiently cooled. This is also one of the problems of Patent Document 1.

  The present invention has been made to complete such a current situation.

  The EGR device exhibits its effect mainly in the state of medium rotation / medium load, and the EGR gas is not recirculated in a state where the rotational speed is low as in the low rotation idling state. The flow resistance (pressure loss) of the cooling water flowing through the cooling water passage is proportional to the discharge pressure of the water pump, but the discharge pressure of the water pump increases as the rotational speed increases. Pressure also increases. That is, although the absolute value of the pressure varies depending on the distance from the water pump, the cooling water pressure increases in accordance with the engine speed at any point in the cooling water passage. The inventor of the present application has completed the present invention based on such knowledge.

That is, the invention of the present application includes the inventions of claims 1 and 2, wherein the invention of claim 1 includes an engine body having an intake passage and an exhaust passage connected to each other and a cooling water passage, and the cooling water passage. A water pump that pumps the cooling water to, a radiator in which the cooling water flows from the upper tank to the lower tank, and an EGR that recirculates a part of the exhaust gas from the exhaust passage to the intake passage at an EGR possible rotational speed that is higher than the minimum idling rotational speed. A passage and
The upper tank of the radiator is always in communication with the cooling water passage, and the lower tank of the radiator is connected to the cooling water passage through a thermo valve, while the EGR passage is provided with a water-cooled EGR cooler, and The basic configuration is that the flow resistance of the cooling water circulation path that circulates between the water pump and the cooling water passage increases in proportion to the engine speed.

  According to the first aspect of the present invention, in the above basic configuration, the EGR cooler water supply pipe that sends the cooling water to the EGR cooler is branched from the cooling water circulation path, while the EGR through which the cooling water discharged from the EGR cooler passes. The cooler drain pipe is connected to the upper tank of the radiator or the cooling water circulation path, and the flow resistance of the cooling water in the cooling water circulation path and the flow resistance of the cooling water in the EGR cooler water supply pipe are approximately equal in engine speed. The cooling water does not flow into the EGR water supply pipe from the cooling water circulation path to the EGR feed pipe until the EGR possible rotation speed is reached, and when the engine rotation speed reaches the EGR possible rotation speed, the cooling water is removed from the cooling water circulation path. The relationship is set to flow into the EGR water supply pipe.

  According to a second aspect of the present invention, in the first aspect, the EGR cooler water supply pipe branches off from a portion close to the water pump in the cooling water passage, while the EGR cooler water supply pipe is made narrower in inner diameter. The cooling water is set so as not to flow from the cooling water circulation path to the EGR cooler water supply pipe in a rotation range lower than the possible rotation speed.

  The warm-up operation is generally performed in an idling state in which the automobile is stopped, and it is normal that the EGR gas is not recirculated in the low-speed idling region (the idling speed is wide and idling is not performed). During operation, for example, when an alternator or an air conditioner compressor is driven, the rotational speed increases slightly and the load also increases, and the rotational speed can increase considerably in the no-load idling state. And it is possible to recirculate the EGR gas when the rotational speed is considerably high.)

  In the present invention, in the warm-up operation in which the EGR passage is not heated and the rotational speed is low, the cooling water does not flow at all or almost through the EGR pipe that has not been heated, so the temperature of the cooling water is decreased. When the engine speed increases to a certain level and the EGR gas begins to flow, the cooling water flows into the EGR cooler due to the pressure increase in the cooling water passage, and the EGR gas is removed. Can be cooled accurately.

  As described above, in the present invention, since the cooling water does not flow through the EGR cooler when the EGR gas is not recirculated, the EGR cooler is prevented from being excessively cooled, and the EGR cooler is cooled sufficiently. it can.

  In the present invention, the cooling water to the EGR cooler branches off from the cooling water circulation path from the water pump to the end of the cooling water passage, and the cooling water that has been heated up from the cooling water passage is removed from the EGR cooler. Therefore, the cooling performance of the EGR cooler after warm-up can be improved.

  More specifically, since the EGR cooler is exposed to exhaust gas, the EGR cooler becomes very hot during normal operation. In the present invention, this can be cooled with cooling water having the lowest possible temperature. The performance can be improved and the charging efficiency can be improved, which in turn can contribute to the improvement of fuel consumption. In particular, when the configuration of claim 2 is adopted, the EGR gas can be cooled with cooling water that has not been heated by the engine body, which is suitable for improving the cooling performance of the EGR gas.

  Further, the pressure of the cooling water circulation path varies depending on the number of rotations of the water pump. However, since the pressure change is larger as the water pump is closer, if the EGR cooler water supply pipe is branched from the portion near the water pump as in claim 2 The responsiveness of the ease of inflow of cooling water into the EGR cooler water supply pipe when the rotational speed changes can be improved. Therefore, it is possible to more surely cool the EGR cooler appropriately and appropriately according to the recirculation of the EGR gas.

  Further, when the EGR cooler water supply pipe is branched from a portion close to the water pump as in claim 2, it is preferable that the EGR cooler can be accurately cooled with low-temperature cooling water. In particular, when the EGR cooler water supply pipe is connected to the upper tank of the radiator, the cooling water heated by the EGR cooler heated to a high temperature after being warmed up can be accurately cooled, and the cooling water heated by the EGR cooler passes through the engine body. It can also prevent the engine body from cooling down.

  Furthermore, since the invention of claim 2 only reduces the inner diameter of the EGR cooler water supply pipe, it has the advantage that the configuration is simple and the cost can be reduced accordingly. It should be noted that reducing the inner diameter of the EGR cooler water supply pipe means, for example, making it thinner than the inner diameter of the pipe for allowing cooling water to enter and exit from the engine body to the radiator. The specific inner diameter is the total amount of cooling water. And the performance of the water pump.

(A) is a schematic diagram of the whole structure, (A) is a top view, (B) is a front view. It is a figure which shows an effect | action. It is a graph which shows the relationship between an engine speed, a cooling water circulation path, and the internal pressure (flow resistance) of an EGR cooler feed pipe. It is a figure which shows the difficulty of inflow of the cooling water from a cooling water circulation path to an EGR cooler feed pipe, and the relationship between each element, (A) is a conceptual circuit diagram, (B) is a graph which shows the influence of each element. .

(1). Outline of Structure Next, an embodiment of the present invention will be described with reference to the drawings. First, an outline of the configuration of the internal combustion engine will be described mainly with reference to FIG. The present embodiment is applied to a three-cylinder internal combustion engine for a vehicle, and includes a cylinder block 1 and a cylinder head 2 overlapping the upper surface as main parts of the engine body. (Not shown) is fixed. A chain cover 3 is fixed to one side surface of the cylinder block 1 and the cylinder head 2, and a CVT transmission 4 is attached to the other side surface of the cylinder block 1. The chain cover 3 also constitutes a part of the engine body.

  The internal combustion engine of the present embodiment is a horizontal type in which the crankshaft is turned sideways toward the traveling direction of the vehicle, an intake manifold 5 is fixed to the rear surface of the cylinder head 2, and an exhaust manifold 6 is mounted on the front surface of the cylinder head 2. Is fixed. An intake passage 8 starting from an air cleaner 7 is connected to the intake manifold 5, and a throttle valve 9 and a surge tank 10 located downstream thereof are provided in the intake passage 8.

  On the other hand, an exhaust passage 11 is connected to the exhaust manifold 6. The exhaust passage 11 is connected to a catalytic exhaust gas purification device 12, an exhaust turbocharger (not shown), a silencer (not shown), and the like. Is provided. Further, the exhaust passage 11 and the intake passage 8 are connected by an EGR passage 13, and the EGR passage 13 is provided with a water-cooled EGR cooler 14 and an EGR valve 15 for adjusting the flow rate.

  In the present embodiment, the EGR passage 13 is connected to the upstream side of the purification device 12 in the exhaust passage 11, but may be connected to the downstream side. The EGR passage 13 is entirely shown as a pipe line away from the engine body, but a part of the EGR passage 13 is incorporated in the exhaust manifold 6 and the cylinder head 2 (that is, the EGR passage is connected to the exhaust manifold 6 and the cylinder head 2). 13 can also be formed). The illustrated EGR valve 15 is provided at a position near the intake passage 8 on the downstream side of the EGR cooler 14, but can also be provided on the upstream side of the EGR cooler 14.

  The cylinder block 1 and the cylinder head 2 are provided with cooling water passages (water jackets) 17 and 18, respectively. The cooling water is supplied to the cooling water passages 17 and 18 from a water pump 19 driven by a crankshaft. Pumped. In the embodiment, the cooling water is set to flow from the first cooling water passage 17 to the second cooling water passage 18, but the reverse flow can also be adopted (in this case, the cooling water is supplied from the water pump 19. It is pumped to the second cooling water passage 18).

  A thermo valve 20 that communicates with the cooling water passage 18 of the cylinder head 2 is provided on one side of the cylinder head 2, and when the temperature of the cooling water reaches a predetermined level, the radiator 21 passes through the thermo valve 20. It circulates to. Hereinafter, for convenience, the cooling water passage 17 of the shilling block 1 is referred to as a first cooling water passage, and the cooling water passage 18 of the cylinder head 2 is referred to as a first cooling water passage.

  The radiator 21 has an upper tank 22, a lower tank 23, a narrow tube group 24 connecting them, and a fan 22 a that sucks heat from the thin tube group 24. The upper tank 22 is an outward pipe 25 and is connected to the second cooling water passage 18. The lower tank 23 is connected to the end portion, and is connected to the thermo valve 21 via the return pipe 26. When the thermo valve 20 is opened by increasing the temperature of the cooling water, the forward pipe 26 can pass water, Cooling water circulates in the radiator 21. The cooling water that has returned from the return pipe 26 of the radiator 21 to the thermo valve 20 returns to the water pump 19 from the return passage 30. The cooling water heated by the engine body circulates through the heater 31 at all times.

  The discharge port 19a of the water pump 19 and the inlet 17a of the first cooling water passage 17 are connected by a water supply passage 32 formed in the chain cover 3, and the water supply passage 32 and the first and second cooling water passages 17, 18 constitutes the cooling water circuit described in the claims. An EGR cooler water supply pipe 33 that sends cooling water to the EGR cooler 14 branches off from a portion of the first cooling water passage 17 close to the inlet 17a, while the EGR cooler through which the cooling water discharged from the EGR cooler 14 passes. The drain pipe 34 is connected to the upper tank 22 of the radiator 21.

  As shown in FIG. 2, most of the EGR cooler water supply pipe 33 is constituted by a hose (tube) 35, and the hose 35 is connected to the shilling block 1 via a joint pipe 36. In the illustrated example, the joint pipe 36 is orthogonal to the wall surface of the shilling block 1 in a plan view and a side view. Therefore, the inlet portion 33 a of the EGR cooler water supply pipe 33 is orthogonal to the flow of the first cooling water passage 17. It has become a posture.

(2) Action Next, the action will be described with reference to FIGS. As described above, the EGR cooler water supply pipe 33 is constituted by the hose 35, but the pressure loss (flow resistance) when the cooling water flows through the EGR cooler water supply pipe 33 first depends on the inner diameter d thereof. That is, when the inner diameter d is large, the cooling water easily flows and the pressure loss is small, and when the inner diameter d is small, the cooling water hardly flows and the pressure loss is large.

  Accordingly, when the water pump 19 is driven, the pressure at the start end of the first cooling water passage 17 is P1, and the pressure (resistance) at the inlet 33a of the EGR cooler water supply pipe 33 is P2. As the number increases and the discharge amount per unit time of the water pump 19 increases, the flow resistance of the first cooling water passage 17 becomes higher. Therefore, as shown in FIG. 3, P1 is proportional to the engine speed. Get higher. On the other hand, the internal pressure (resistance) P2 of the EGR cooler water supply pipe 33 is highly dependent on the inner diameter d and the length L2 (see FIG. 4).

  On the other hand, the recirculation of the EGR gas is started after the engine speed has increased to some extent. Therefore, as shown in FIG. 3, the internal pressure (resistance) P2 of the EGR cooler water supply pipe 33 is higher than the internal pressure P1 of the first cooling water passage 17 until the engine speed reaches the EGR possible speed R2, and the engine speed When the number exceeds the EGR possible rotation speed R2, the cooling water pressure P1 of the first cooling water passage 17 is set to be higher than the internal pressure (resistance) P2 of the EGR cooler water supply pipe 33.

  That is, EGR is such that cooling water flows from the first cooling water passage 17 into the EGR cooler water supply pipe 33 against the flow resistance of the EGR cooler water supply pipe 33 when the engine speed exceeds the EGR possible rotation speed R2. The inner diameter d of the cooler water supply pipe 33 is set. In other words, the pressure difference P ′ between P2 and P1 is set to switch from positive to negative around the EGR possible rotation speed R2. The reflux of EGR may be started after the EGR possible rotation speed R2 is exceeded.

  Thereby, when the recirculation of the EGR gas is started, the inflow of the cooling water to the EGR cooler 14 is started almost at the same time, and the EGR cooler 14 can be accurately cooled. When the rotational speed becomes lower than the EGR possible rotational speed R2 as in the idling state or the deceleration state in which the throttle valve 9 is fully closed, the water flow to the EGR cooler 14 is also stopped. Thereby, the EGR cooler 14 can be cooled without excess or deficiency.

  The idling speed has a certain range, but even in the idling state, for example, when one or both of the alternator and the air conditioner compressor is driven, the rotational speed is high and has a certain level. When a load is applied, the EGR gas may be refluxed. That is, the EGR possible rotation speed R2 is higher than the minimum idling speed R1, but may be slightly lower than the maximum idling speed.

  Further, the actual recirculation of the EGR gas and the inflow of the cooling water to the EGR cooler 14 may be mixed. In other words, the cooling of the EGR cooler 14 and the recirculation of the EGR gas may be started at the same time as reaching the EGR possible rotation speed R2, or one of them may be earlier and the other may be later.

  1B, the EGR cooler water supply pipe 33 can also be branched from a water supply passage 32 between the water pump 19 and the first cooling water passage 17. As shown in FIG. Alternatively, it is possible to branch from the second cooling water passage 18. Further, for some reason, it is possible that some cooling water may flow through the EGR cooler water supply pipe 33 in a rotation range slightly lower than the EGR possible rotation speed R2, in which case the dotted line in FIG. As indicated by an arrow 37, the air also escapes from the upper tank 22 of the radiator 21 through the forward pipe 25 of the radiator 21 to the second cooling water passage 18. Therefore, no particular problem occurs.

  The ease of flow of the cooling water from the first cooling water passage 17 to the EGR cooler water supply pipe 33 (the size of (P2-P1) under a certain condition) is determined in addition to the inner diameter d and the length of the EGR cooler water supply pipe 33. Various eases are also acting. For example, as shown in FIG. 4, the distance L1 from the start end of the EGR cooler water supply pipe 33 to the end of the second cooling water passage 18 is one of them, and the longer the L1, the longer the distance from the first cooling water passage 17 to the EGR cooler. It becomes difficult to flow into the water supply pipe 33.

  Further, since the flow resistance of the EGR cooler water supply pipe 33 tends to increase as the capacity Q of the upper tank 22 constituting the radiator 21 increases, the ease of flow from the first cooling water passage 17 to the EGR cooler water supply pipe 33 increases. It has a negative proportional relationship.

  In addition, the greater the crossing angle θ of the EGR cooler water supply pipe 33 with respect to the flow direction of the first cooling water passage 17, the higher the ease of inflow into the EGR cooler water supply pipe 33. On the other hand, it can be said that there is a direct proportional relationship.

  As mentioned above, although embodiment of this invention was described, this invention can be variously embodied other than said embodiment. For example, the EGR cooler water supply pipe can be connected to the cooling water passage (second cooling water passage) of the cylinder head without being connected to the upper tank of the radiator.

  The present invention can actually be embodied in an automobile internal combustion engine. Therefore, it can be used industrially.

DESCRIPTION OF SYMBOLS 1 Chilling block which comprises engine main body 2 Cylinder head which comprises engine main body 8 Intake passage 11 Exhaust passage 13 EGR passage 14 EGR cooler 17 1st cooling water passage (cooling water passage of a shilling block) which comprises a cooling water circulation path
18 Second cooling water passage (cooling water passage of cylinder head) constituting cooling water circulation path
19 water pump 21 radiator 22 upper tank 23 lower tank 32 water supply passage constituting cooling water circulation path 33 EGR cooler water supply pipe 33 EGR cooler drain pipe

Claims (2)

An engine body having a cooling water passage connected to an intake passage and an exhaust passage, a water pump for pumping the cooling water to the cooling water passage, a radiator for the cooling water to flow from the upper tank to the lower tank, and a minimum idling speed An EGR passage that recirculates a part of the exhaust gas from the exhaust passage to the intake passage at a higher EGR possible rotational speed,
The upper tank of the radiator is always in communication with the cooling water passage, and the lower tank of the radiator is connected to the cooling water passage through a thermo valve, while the EGR passage is provided with a water-cooled EGR cooler, and The flow resistance of the cooling water circulation path that circulates between the water pump and the cooling water path is configured to increase in proportion to the engine speed,
An EGR cooler water supply pipe that feeds cooling water to the EGR cooler is branched from the cooling water circulation path, while an EGR cooler drain pipe through which the cooling water discharged from the EGR cooler passes is an upper tank of the radiator or the cooling water circulation path Connected to
The flow resistance of the cooling water in the cooling water circulation path and the flow resistance of the cooling water in the EGR cooler water supply pipe are divided into the EGR water supply pipe from the cooling water circulation path until the engine speed reaches substantially the EGR possible rotation speed. The cooling water flows into the EGR water supply pipe from the cooling water circulation path when the engine rotation speed reaches approximately the EGR possible rotation speed with little or no inflow.
Automotive internal combustion engine. The EGR cooler water supply pipe branches off from the portion near the water pump in the cooling water passage, while the EGR cooler water supply pipe is cooled to cool the cooling water in a rotation range lower than the EGR possible rotation speed. It is set not to flow from the water circulation path to the EGR cooler water supply pipe.
An internal combustion engine for automobiles according to claim 1.

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