Patent Application
20110173962
The invention relates to a heat retention/cooling control device for a PM filter device (a device for capturing particulate matters (PM) contained in an exhaust gas).
Note that, in the invention, a front-back traveling direction when viewed from a side surface of an work machine is defined as a front-back direction, and a right-left direction when viewed from a front surface of the work machine is defined as a vehicle width direction.
Conventionally, a PM filter device has been used to prevent PM (particulate matters) which are particulate substances contained in an exhaust gas of a diesel engine from being emitted into the atmosphere as it is. The PM filter device is used as a device which is disposed in an exhaust passage of the exhaust gas and captures and reduces PM contained in the exhaust gas by a filter.
As a basic configuration of the PM filter device, the PM filter device is configured to capture PM by a filter. Further, the PM filter device may have a self-cleaning function capable of combusting PM captured by the filter and refreshing the filter to prevent deterioration of a filter function when the filter is clogged.
As a filter refreshing technology, an oxidation catalyst disposed upstream of a filter is oxidized and caused to generate heat by supplying a fuel into an exhaust gas. Then, a temperature of the exhaust gas that flows into the filter is increased, and PM deposited on the filter is self-combusted by the exhaust gas whose temperature has been increased. The filter is refreshed by eliminating clogging of the filter caused by the PM by combusting the PM.
When the PM filter device combusts the PM to eliminate the clogging of the filter, the PM filter device can improve a combustion efficiency at the time the PM is combusted by placing the PM filter device in a high temperature state. However, at this time, since a temperature of an outer periphery of the PM filter device also becomes high, a bad influence due to heat (so-called heat damage) is applied to peripheral equipment disposed in a periphery of the PM filter device. Further, when a driver's cabin is disposed in the vicinity of the PM filter device, a temperature in the driver's cabin is increased when the PM is combusted.
Various devices have been proposed to prevent the heat damage by the PM filter device, such as a cooling fan control device for predicting and preventing a temperature increase in the periphery of the PM filter device (refer to Patent Document 1), and a filter refresh control device of a diesel engine by which a combustion efficiency of a PM filter device is improved (refer to Patent Document 2). In the filter refresh control device of Patent Document 2, a heat shield plate is disposed in the periphery of a PM filter device so that outside air can be taken between the PM filter device and the heat shield plate and the intake outside air is caused to flow into a hot air duct, thereby improving the combustion efficiency of the PM filter device.
Since the radiator 73 and the capacitor 74 of the air conditioner are cooled by air supplied from the cooling fan 72, temperatures of cooling water and a refrigerant can be reduced by the air. Further, temperatures of components such as the engine 70 and the PM filter device 75 disposed in the engine room can be reduced by waste heat wind from the cooling fan 72.
Then, a rotation speed of the cooling fan 72 is set to increase when the temperature of the cooling water is high, when a load of the air conditioner is large, and when the PM filter device 75 is being refreshed. Further, a control is performed so that a predetermined time difference is provided until the rotation speed of the cooling fan 72 is controlled from a time at which a refresh signal of the PM filter device 75 is received. That is, the control of the rotation speed of the cooling fan 72 is started after a start delay time t1 passes.
An intake air switch valve 81 is opened and closed so as to switch the air taken from the hot air duct 92 and the air taken from a fresh air duct 80. When the intake air switch valve 81 is opened, air is taken from the hot air duct 92. When the intake air switch valve 81 is closed, air is taken from the fresh air duct 80.
The intake air is cleaned by an air cleaner 82, an intake amount of the air is detected by an air flow meter 83, and the air is supercharged by a turbocharger 84. After the air, which is supercharged by the turbocharger 84 (hereinafter, called supercharged air) is cooled by an intercooler 85 (corresponding to an aftercooler), the air is taken into an engine main body 88 flowing through an intake shutter 86 and an intake manifold 87.
When the intake air switch valve 81 is opened and the air, which is heated by heat radiated from the PM filter device 90, is taken into the engine, a temperature of an exhaust gas from the engine can be increased. Then, since a temperature of the PM filter device 90 can be promptly increased, a combustion efficiency of the PM filter device 90 can be improved.
A fuel supplied from a fuel pump 93 to a common rail 94 is mixed with the supercharged air cooled by the intercooler 85, and the supercharged air is taken into the engine main body 88 as an air/fuel mixed gas. That is, the fuel supplied from the fuel pump 93 to the common rail 94 is injected from an injection nozzle 95 and mixed with the supercharged air cooled by the intercooler 85.
After the air/fuel mixed gas is ignited and the engine is driven, an exhaust gas as a combustion gas is exhausted from an exhaust manifold 89.
The PM contained in the exhaust gas is captured by, and deposited on, a filter of the PM filter device 90. Further, a part of the exhaust gas is returned from the exhaust manifold 89 to the intake manifold 87 flowing through an EGR cooler 96 and an EGR valve 97.
A pressure difference between an inlet and an outlet of the PM filter device 90 is detected by a difference pressure sensor 98. Further, an inlet temperature of the PM filter device 90 is detected by a PM filter device inlet temperature sensor 99, and an outlet temperature is detected by a PM filter device outlet temperature sensor 100. The signals detected by the sensors are sent to an engine control unit 101. When clogging of the filter of the PM filter device 90 is eliminated and the filter is refreshed, a control is performed to introduce heated air from the hot air duct 92 to increase a combustion efficiency of PM deposited on the filter.
Incidentally, in, for example, a dump track as an work machine, cooling devices such as a radiator, an aftercooler, and the like are ordinarily disposed on a front surface of a vehicle body so that wind generated when the vehicle travels is positively used as cold wind.
Moreover, since a cooling fan for cooling the cooling devices is often directly coupled with an engine, the cooling devices are disposed in a limited space on the front surface side of the engine. Accordingly, as shown also in the conventional example 1 described above, a configuration in which cooling members of the radiator, the aftercooler, and the like are overlapped is employed.
In the configuration in which the cooling members are overlapped as described above, a cooling member disposed on a rear side of the overlapped cooling members is impinged with waste heat wind preheated by a cooling member disposed in front of the cooling member. Accordingly, a cooling efficiency of the cooling member disposed on the rear side is lowered.
The problem can be solved by increasing a pressure receiving area of the cooling member impinged with the waste heat wind in the cooling device disposed on the rear side and increasing an amount of air of a cooling fan of the cooling device disposed forward. However, the increase in the pressure receiving area of the cooling member and the increase in the amount of air of the cooling fan result in an increase in a size of the cooling device itself disposed on the rear side and use of a large cooling fan.
In this case, a new problem arises in that an installation space, which is necessary to install the cooling device and the cooling fan configured in the large size cannot be sufficiently secured, the cooling device and the cooling fan interfere with other equipment, and noise generated by the cooling fan is increased. In particular, when heat rejection of the engine increases, the layout configuration described above cannot overcome the increased heat rejection.
To solve the problems, the applicant has proposed a cooling device of a hydraulic shovel in which an aftercooler is disposed in a space different from an engine room in which a radiator is disposed (refer to Patent Document 3).
A radiator 55 and a hydraulic oil cooler 54 are disposed in series forward of a cooling fan 53 directly coupled with the engine 52, and an air cleaner 57 is disposed above the engine 52. The air cleaner 57 is connected to a turbocharger 56 via an air piping 60, and the turbocharger 56 is connected to an air-cooled aftercooler 58 via an air piping 59. Further, the air-cooled aftercooler 58 is connected to the engine 52 via an air piping 61.
Further, the air-cooled aftercooler 58 is disposed separately outside the engine room 51 at a position approximately adjacent laterally to the radiator 55 so as to be located near a side wall portion side of the large hydraulic shovel.
Patent Document 1: Japanese Patent Application Laid-Open No. 2007-138872
Patent Document 2: Japanese Patent Application Laid-Open No. 2005-299628
Patent Document 3: Japanese Patent Application Laid-Open No. 9-125972
In the cooling fan control device described in Patent Document 1, the engine 70 and the PM filter device 75 are disposed together in the engine room 71. Moreover, after the engine is cooled by the waste heat wind from the cooling fan 72, an outer periphery of the PM filter device 75 is cooled. Accordingly, although the outer periphery of the PM filter device 75 can be cooled a little, an outer periphery of the PM filter device 75, by which PM is being combusted, cannot be forcibly cooled.
Accordingly, to prevent a heat damage to peripheral equipment disposed in the periphery of the PM filter device 75, a special countermeasure of surrounding the peripheral equipment by an insulation material, and the like must be taken. Further, although it is not particularly described to dispose an aftercooler, even when the aftercooler is disposed, the aftercooler is disposed in the engine room 71. Thus, a cooling efficiency of an intake pipe connected to the aftercooler is lowered by warm air in the engine room 71.
The filter refresh control device described in Patent Document 2 is configured only to take the outside air from the space formed between the PM filter device 90 and the heat shield plate 91 and cannot forcibly cool an outer periphery of the PM filter device 90 or control a temperature of the outer periphery of the PM filter device 90. Moreover, since a periphery of the PM filter device 90 must be covered with the heat shield plate 91, a heat shield plate having a special specification must be used as a heat shield plate that can be used for a long period.
Further, since the intercooler 85 is disposed in the engine room, a cooling efficiency of an intake pipe connected to the intercooler 85 is lowered by warm air in the engine room. In particular, the air cooled by the intercooler 85 is warmed in an intake pipe connected to the intercooler 85 by the warm air in the engine room.
Further, to improve the combustion efficiency of PM in the PM filter device 90, the intake air switch valve 81, the hot air duct 92, and the like need to be disposed. Thus, an arrangement for disposing the intake air switch valve 81, the hot air duct 92, and the like becomes complex, and further an installation space for installing the intake air switch valve 81 and the hot air duct 92 is necessary.
In the cooling device described in Patent Document 3, to easily introduce outside air into the air-cooled aftercooler 58, the air-cooled aftercooler 58 is disposed in the portion near the side wall portion side of the large hydraulic shovel. Accordingly, the air-cooled aftercooler 58 is disposed in a portion in a side direction away from the portion where the engine is disposed in a vehicle width direction of the large hydraulic shovel.
Since the cooling device is configured as described above, the air piping 59, which connects the air-cooled aftercooler 58 to the turbocharger 56, and the air piping 61, which connects the air-cooled aftercooler 58 to the engine 52 each have a long length. Moreover, the air piping 59 and the air piping 61 are disposed long in the engine room 51.
In particular, since the air piping 61, through which the air cooled in the air-cooled aftercooler 58 is caused to flow, is disposed long in the engine room 51, the air which flows in the air piping 61 is warmed by the warm air in the engine room 51. Therefore, even if the air is cooled in the air-cooled aftercooler 58, a cooling effect of the air is lowered thereafter in the air piping 61.
Moreover, since the air-cooled aftercooler 58 and the radiator 62 are disposed along the vehicle width direction of the large hydraulic shovel, it is difficult to effectively make use of wind generated by traveling.
The invention, which has been made to overcome the disadvantages described above, is to provide a heat retention/cooling control device for a PM filter device which can efficiently perform a temperature control of an outer periphery of the PM filter device when combustion is performed by a filter of the PM filter device, can cause the PM filter device to efficiently perform combustion, and moreover does not apply an influence of a heat damage to the peripheral portion of the PM filter device effectively making use of wind generated by traveling.
In order to achieve the above object, a heat retention/cooling control device for a PM filter device for reducing PM as particulate matters contained in an exhaust gas exhausted from a diesel engine mounted on an work machine, includes:
a cooling passage disposed in parallel with an engine room configured in a front-back direction of the work machine and demarcated from the engine room via a partition wall; an aftercooler disposed in the cooling passage for cooling air supercharged by a supercharger disposed in the engine room; the PM filter device which is disposed on a downstream side of the aftercooler in the cooling passage and into which the exhaust gas from the engine is introduced; a cooling fan which is disposed in the cooling passage, cools the aftercooler, and cools an outer periphery of the PM filter device by waste heat wind which has cooled the aftercooler;
a temperature sensor for detecting an exhaust gas temperature of the exhaust gas; and a controller connected to the temperature sensor for controlling an amount of air of the cooling fan when the PM captured by a filter of the PM filter device PM is combusted,
being characterized in that, when the exhaust gas temperature detected by the temperature sensor is higher than a target temperature, the controller performs a control for increasing a cooling effect to the outer periphery of the PM filter device by increasing the amount of air from the cooling fan, and when the exhaust gas temperature detected by the temperature sensor is lower than the target temperature, the controller performs a control for assisting to increase and to retain a temperature in the outer periphery of the PM filter device by reducing the amount of air from the cooling fan.
Also in the invention, an exhaust pipe for introducing an exhaust gas exhausted from the engine into the PM filter device is disposed to receive wind from the cooling fan on an upstream side of the PM filter device.
In the invention, when the PM captured by the filter of the PM filter device is combusted, an amount of air of a cooling fan, which cools an aftercooler and the outer periphery of the PM filter device, can be controlled by the controller based on an exhaust gas temperature of an exhaust gas.
When the exhaust gas temperature of the exhaust gas is higher than a target temperature at the time the PM captured by the filter of the PM filter device is combusted, it can be determined that the exhaust gas temperature is a temperature at which the PM can be sufficiently combusted in the PM filter. At this time, to reduce an influence of a heat damage due to combustion, the outer periphery of the PM filter device can be cooled by increasing the amount of air from the cooling fan.
Further, when the exhaust gas temperature of the exhaust gas is lower than the target temperature at the time the PM is combusted, it can be determined that the exhaust gas temperature does not reach a temperature at which the PM can be sufficiently combusted in the PM filter device. At this time, since a priority is placed on sufficient combustion of the PM rather than on reduction of the influence of heat damage, the cooling fan is controlled to reduce the amount of air therefrom to increase the exhaust gas temperature.
When the amount of air from the cooling fan is reduced, a cooling efficiency of the aftercooler is lowered and a temperature of the supercharged air taken from the aftercooler into the engine can be increased. Then, since the temperature of the exhaust gas exhausted from the engine is also increased, an oxidation catalyst disposed on an upstream side of the filter can be easily oxidized and caused to generate heat. With the operation, since the temperature of the exhaust gas supplied to the filter is increased, the PM clogged in the filter can be self-combusted.
When the combustion in the filter is sufficiently performed and the exhaust gas temperature increases higher than the target temperature, the cooling fan can be controlled to increase the amount of air therefrom to cool the outer periphery of the PM filter device in turn. Then, heat damage due to heat radiated from the outer periphery of the PM filter device can be prevented.
In the invention, a cooling passage demarcated from the engine room across a partition wall is disposed in parallel with the engine room, and the aftercooler, the cooling fan for cooling the aftercooler, and the PM filter device, to which the waste heat wind exhausted from the cooling fan is supplied, are disposed in the cooling passage.
With the configuration described above, since the wind generated by traveling can be separately introduced into the engine room and the cooling passage, a radiator disposed in the engine room and the aftercooler disposed in the cooling passage can be cooled efficiently. Moreover, an outer peripheral surface of the PM filter device can be efficiently cooled by the waste heat wind by which the aftercooler is cooled.
Further, the partition wall can make an inside of the cooling passage unlikely to be influenced by the warm air in the engine room. Since the aftercooler can be disposed in the cooling passage which is unlikely to be influenced by the warm air in the engine room, a cooling effect of the aftercooler and a cooling effect when the outer peripheral surface of the PM filter device is cooled by the waste heat wind after the aftercooler is cooled can be increased.
Further, since the partition wall can prevent occurrence of a turbulent flow caused by collision between the waste heat wind from the radiator which flows in the engine room, and the waste heat wind from the aftercooler which flows in the cooling passage, the partition wall can prevent the amounts of the respective waste heat wind from being reduced by the occurrence of the turbulent flow.
Moreover, the waste heat wind from the radiator, which flows in the engine room, can be caused to flow in the engine room as a laminar flow, and the waste heat wind, which flows in the cooling passage from the aftercooler, can be caused to flow in the cooling passage as a laminar flow. As a result, the respective air flows and the respective amounts of air in the engine room and in the cooling passage can be influenced well.
Further, since the cooling passage is demarcated from the engine room across the partition wall, noise generated from a cooling fan for the radiator and noise from the engine can be prevented from being leaked to the outside through the cooling path.
Further, in the invention, an exhaust pipe, which introduces the exhaust gas exhausted from the engine into the PM filter device, can be disposed so as to receive wind from the cooling fan upstream of the PM filter device. Then, when the PM filter device performs combustion and is increased in temperature, the exhaust pipe can be cooled by the wind from the cooling fan whose amount is increased. With the operation, the exhaust gas temperature of the exhaust gas introduced into the PM filter device can be prevented from becoming excessively high.
Further, when the exhaust gas temperature of the exhaust gas is lower than the target temperature at the time the PM is combusted, since the cooling fan is controlled so as to reduce an amount of air, a temperature drop of the exhaust pipe cooled by the wind from the cooling fan can be suppressed low. The exhaust gas can be introduced into the PM filter device without lowering a temperature of the exhaust gas whose exhaust gas temperature is increased. This operation can contribute to improving the combustion efficiency of the PM filter device.
A typical embodiment of a heat retention/cooling control device for a PM filter device according to the invention will be explained below referring to the drawings.
As shown in
Then, an upper portion of the engine room 11 is covered with an engine hood 17 (refer to
Further, the work machine 10 is mounted with a cab 23 disposed in an upper rear portion of the engine room 11, and right and left front wheels (not shown), a transmission, an axle device, and the like are disposed in a region below the cab backward of the engine room 11.
A cooling passage 20 is disposed in parallel with the engine room 11 along the front-back direction of the work machine 10. The cooling passage 20 is surrounded by an aftercooler cover (not shown), the partition wall 18, and a lower surface plate (not shown), and the air, which is taken from an outside air introduction port disposed forward of the aftercooler cover, flows backward. As shown in
Note that the aftercooler cover may be configured integrally with the engine hood 17 that covers an upper portion of the engine room 11 described above. On the contrary, the aftercooler cover may have a divided configuration in a structure by which a flow of air is not inhibited in place of the configuration by which the aftercooler cover integrally covers up to a PM filter device 25 described later.
Further, as a part of a wall that configures the partition wall 18, a side wall surface of an aftercooler 21 disposed in the cooling passage 20 to be described later may be used. The partition wall 18 may be configured to demarcate between the engine room 11 and the cooling passage 20 only by a wall without using the side wall surface of the aftercooler 21. The partition wall 18 may be configured to perfectly shut off between the engine room 11 and the cooling passage 20 or may be configured to have a gap through which air can enter and exit between the engine room 11 and the cooling passage 20 a little without perfectly shutting off between the engine room 11 and the cooling passage 20.
Even if the partition wall 18 is configured to have the gap, it is preferable to configure the gap so that air, which flows in the engine room 11, and the air, which flows in the cooling passage 20, are not disturbed by the air which enters from the gap.
An air cleaner 16, the aftercooler 21, a cooling fan 22 for cooling the aftercooler 21, and the PM filter device (particulate matter filter device) 25 the periphery of which is cooled by the waste heat wind from the cooling fan 22 are disposed in series in the cooling passage 20. The PM filter device 25 is disposed on a side of the cab 23 upward of the front wheels (not shown).
The PM filter device is a device (filter) for reducing PM (particulate matters) as particulate substances contained in an exhaust gas of a diesel engine and basically configured as a device for capturing the PM by the filter. The PM filter device 25 shown in an illustrated example has a self-cleaning function capable of refreshing the filter by combusting the PM captured by the filter to prevent that a filter function from being lowered when the filter is clogged.
The cooling fan 14, which is disposed forward of the engine 12, may be directly coupled with the engine 12 or may be driven by a hydraulic motor driven by an ejection pressure from a hydraulic pump (not shown) driven by the engine 12 like the cooling fan 22 of the aftercooler 21. Alternatively, the cooling fan 14 may be driven by an electrically driven motor.
When the cooling fan 14 and the cooling fan 22 are driven by hydraulic motors, respectively, a degree of freedom of disposition of the radiator 13, the hydraulic oil cooler 19, and the like to the position at which the aftercooler 21 is disposed can be increased. Further, the cooling air, which is caused to flow by the cooling fan 14 and the cooling fan 22, may be configured as a flow on an intake side with respect to the radiator 13 and the aftercooler 21 as shown in
The radiator 13 is connected with a pair of pipings 29 (only a piping 29 is illustrated in
The outside air taken via the air cleaner 16 is supplied to the exhaust gas turbocharger 15 via the pipe passage 28 and supercharged by a compressor 15b (refer to
The supercharged air cooled by the aftercooler 21 passes through an intake pipe 26b and taken into the engine 12 via an intake manifold (not shown). Then, the supercharged air is mixed with a fuel and used for combustion in the engine 12. The exhaust gas exhausted from the engine 12 after combustion is introduced into the exhaust gas turbocharger 15 via an exhaust pipe 27a (refer to
After the exhaust gas introduced into the exhaust gas turbocharger 15 is used to drive a turbine 15a (refer to
The exhaust gas introduced into the PM filter device 25 is exhausted to outside air passing through an exhaust pipe 27c (refer to
A connection port of the exhaust gas turbocharger 15, which connects the intake pipe 26a connected to the aftercooler 21, and an intake manifold of the engine 12 are disposed near the partition wall 18. Further, as shown in
As shown in
Since the heat retention/cooling control device is configured as described above, wind generated by traveling can be separately introduced into the engine room 11 and the cooling passage 20. Moreover, since lengths of the intake pipes 26a, 26b in the engine room 11 can be configured short, the air flowing in the intake pipes 26a, 26b can be prevented from being warmed by the warm air in the engine room 11.
With the configuration, since an inside of the cooling passage 20 is unlikely to be influenced by the warm air in the engine room 11, a cooling effect to the aftercooler 21 and a cooling effect to an outer peripheral surface of the PM filter device 25 can be increased.
In particular, since the cooling passage 20 can be configured as a kind of duct which is opened in the front-back direction, the wind generated by traveling, which is introduced into the cooling passage 20, and the amount of air, which is generated by the cooling fan 22 for the aftercooler 21, can be effectively used as cooling wind for the aftercooler 21 and as cooling wind for the outer peripheral surface of the PM filter device 25.
As a result, an influence of heat to equipment (not shown) disposed in the periphery of the PM filter device 25 can be prevented by cooling the outer peripheral surface of the PM filter device 25 and further an increase in temperature in the cab (not shown) disposed adjacent to the PM filter device 25 can be suppressed.
Moreover, since the noise generated in the engine room 11 can be shut off by the partition wall 18, a leakage of the noise generated in the engine room 11 to the outside via the cooling passage 20 can be prevented.
Further, the connection port of the exhaust gas turbocharger 15 for connecting the intake pipe 26a connected to the aftercooler 21 and the intake manifold of the engine 12 are disposed near the partition wall 18, the piping lengths of the intake pipes 26a, 26b in the engine room 11 can be configured short.
Since the lengths of the intake pipes 26a, 26b in the engine room 11 can be configured short by the above configuration, the air flowing in the intake pipes 26a, 26b is not exposed to the warm air in the engine room 11 for a long time. As described above, the air flowing in the intake pipes 26a, 26b can be prevented from being warmed by the warm air in the engine room 11.
Next, the heat retention-cooling control device for the PM filter device will be explained using
Accordingly, in
In the illustrated example, after the part of the exhaust gas is cooled by the EGR cooler 39, it passes through the EGR valve 40 and is returned into the intake pipe 26b via a diaphragm 41 disposed in the intake pipe 26b. That is, the exhaust gas cooled by the EGR cooler 39 is taken into the intake pipe 26b by a suction operation in the diaphragm 41. An opening/closing amount of the EGR valve 40 can be detected by a lift sensor 40a.
Further, the CCV device 42 is disposed because, although respective cycles of so-called compression, combustion, and exhaust are generally performed continuously in a diesel engine, the air/fuel mixed gas leaks via a gap of a piston ring between the respective cycles and the blow-by gas is discharged to the crankcase.
Since a pressure in the crankcase is increased by the blow-by gas, a leakage of oil from the crankcase is accelerated. A conventional diesel engine is configured such that a pressure increased in the crankcase is released to the atmosphere via a breather.
However, it is proposed, from an environmental point of view, to return the blow-by gas in the crankcase into a combustion chamber without discharging it to the atmosphere. Thus, there is a CCV device devised for the purpose. In the CCV device 42 of the illustrated example which is configured to return the blow-by gas together with the air/fuel mixed gas to the engine 12 and to combust them in the engine 12, a pressure can be detected by a pressure sensor 42a.
A configuration shown in
The air supplied to the compressor 15b turns into supercharged air by the operation of the compressor 15b and introduced into the aftercooler 21. The supercharged air cooled by the aftercooler 21 is supplied with fuel while it is cooled, turns into an air/fuel mixed gas, and is supplied to the engine 12. Further, as described above, the part of the exhaust gas, which is cooled by the EGR cooler 39 is mixed with the supercharged air and supplied to the engine 12 via the diaphragm 41 disposed in the intake pipe 26b.
Rotation of the engine 12 can be detected by an engine rotation sensor 38. Further, a temperature of intake air supplied to the engine 12 can be detected by an intake air temperature sensor 37b, and a pressure of the intake air supplied to the engine 12 can be detected by an intake air pressure sensor 37a.
A part of the exhaust gas generated by the combustion in the engine 12 is introduced into the EGR cooler 39, and a remaining exhaust gas is introduced into the turbine 15a of the exhaust gas turbocharger 15 passing through the exhaust pipe 27a. The turbine 15a is driven in rotation by the exhaust gas introduced thereinto and drives in rotation the compressor 15b coupled with the turbine 15a. The number of revolutions of the compressor 15b can be detected by a turbo rotation sensor 15c.
In the illustrated example, the turbine 15a is configured as a variable speed turbine, and a capacity of the turbine can be changed by changing an angle of a swash plate. The number of revolutions of the turbine 15a can be controlled by changing the capacity of the turbine. The angle of the swash plate can be detected by a position sensor 15d.
The exhaust gas, which drives the turbine 15a in rotation, is introduced into the PM filter device 25 passing through the exhaust pipe 27b. As shown in
The oxidation catalyst 31 is a catalyst for oxidizing a dosing fuel, which is supplied by the fuel supply device 36, and causing the dosing fuel to generate heat, and an activation temperature of the oxidation catalyst 31 is about 250° C. in terms of an exhaust gas temperature. The temperature of the exhaust gas can be increased by the heat generated by the oxidation catalyst 31, and the PM deposited on the filter 32 can be self-combusted.
The filter 32 is configured to have a lot of small holes communicating with each other from, for example, a flow-in side of the exhaust gas to a flow-out side thereof. The small holes are configured such that small holes whose flow-in sides are opened and whose flow-out sides are closed, and small holes whose flow-in sides are closed and whose flow-out sides are opened are alternately disposed. When the exhaust gas, which flows into the small holes whose flow-in sides are opened, passes through boundary walls between adjacent small holes, the PM is captured by the boundary walls.
Although a material of the filter 32 can be appropriately selected according to a way of use, the filter 32 can be configured using a ceramics material such as cordierite or silicon carbide, and a metal material such as stainless steel or aluminum.
The PM filter device 25 is provided with a difference pressure sensor 33 for measuring a difference between pressures in front of and behind the filter 32, a temperature sensor 34a for detecting a temperature of the exhaust gas introduced from the exhaust pipe 27b, a temperature sensor 34b for detecting a temperature of the exhaust gas after it passes through the oxidation catalyst 31, and a temperature sensor 34c for detecting a temperature of the exhaust gas after it passes through the filter 32. The exhaust gas, which passes through the filter 32 and from which the PM is removed, passes through the exhaust pipe 27C and is exhausted into the atmosphere.
The cooling fan 22, which cools the aftercooler 21 as well as supplies the waste heat wind to an outer periphery of the PM filter device 25, is controlled by a controller 43. The controller 43 controls an amount of air of the cooling fan 22 based on whether an exhaust gas temperature of the exhaust gas detected by the temperature sensor 34c is higher or lower than a preset target temperature.
That is, when the controller 43 determines that the exhaust gas temperature of the exhaust gas detected by the temperature sensor 34c is higher than the preset target temperature at the time the PM captured by the filter 32 of the PM filter device 25 is combusted, the controller 43 determines that the PM is sufficiently combusted in the PM filter device 25 and performs a control for increasing the amount of air of the cooling fan 22.
With this operation, the outer periphery of the PM filter device 25 can be sufficiently cooled by the waste heat wind after it cools the aftercooler 21. Then, the influence of heat damage caused by the PM filter device 25 can be prevented so that peripheral equipment of the PM filter device 25 is not influenced by the heat damage. At this time, since the exhaust pipe 27b disposed on an upstream side of the PM filter device 25 can be cooled by the increased amount of air from the cooling fan 22, the exhaust gas temperature of the exhaust gas can be prevented from becoming excessively high.
Even at the time the PM is combusted in a low outside air temperature state, when it is determined that the exhaust gas temperature of the exhaust gas detected by the temperature sensor 34c is lower than the preset target temperature, the cooling fan 22 is controlled so as to reduce the amount of air.
With this operation, since the supercharged air is insufficiently cooled in the aftercooler 21, a temperature of the supercharged air taken from the aftercooler 21 into the engine 12 is increased. Accordingly, the exhaust gas temperature of the exhaust gas exhausted from the engine 12 is also increased. Moreover, at this time, since the cooling fan is controlled so as to reduce the amount of air, a temperature drop of the exhaust pipe 27b cooled by the wind from the cooling fan can be suppressed low. This contributes to improving a combustion efficiency of the PM filter device 25.
Since combustion in the oxide catalyst 31 is liable to occur, the PM is liable to be self-combusted in the PM filter device 25. When the PM is sufficiently self-combusted in the PM filter device 25 and the exhaust gas temperature of the exhaust gas detected by the temperature sensor 34c becomes higher than the preset target temperature, the outer periphery of the PM filter device 25 can be cooled by increasing the amount of air of the cooling fan 22.
When the amount of air of the cooling fan 22 is reduced, a temperature of the outer periphery of the PM filter device 25 cannot be suppressed low. However, when the exhaust gas temperature of the exhaust gas detected by the temperature sensor 34c is lower than the preset target temperature, since the temperature of the outer periphery of the PM filter device 25 does not become so high, the influence of heat damage to the peripheral equipment disposed in the periphery of the PM filter device 25 can be reduced.
A configuration example for controlling the amount of air of the cooling fan 22 will be explained using
To control the pressurized oil ejected from the hydraulic pump 47 and supplied to the hydraulic motor 44, a flow control valve 48 is disposed at a position which bypasses an intake side and a discharge side of the hydraulic motor 44. The flow control valve 48 is switched by controlling a proportional electromagnetic valve 49 disposed in a pilot line 24 in response to a control command from the controller 43.
The proportional electromagnetic valve 49 is linearly driven in response to the control command from the controller 43, thereby controlling a pilot pressure P supplied to the proportional electromagnetic valve 49. The flow control valve 48 is switched by controlling the pilot pressure, which is supplied from the pilot line 24 to switch the flow control valve 48, by the proportional electromagnetic valve 49. With the operation, a flow rate of the pressurized oil supplied to the hydraulic motor 44 is changed, and the number of revolutions of the hydraulic motor 44 is controlled.
In the example described above, the configuration example, in which the hydraulic pump 47 and the hydraulic motor 44 are configured as a fixed capacity by using the flow control valve 48, has been explained. However, any one of the hydraulic pump 47 and the hydraulic motor 44 can be also configured as a variable capacity type without using the flow control valve 48.
Further, the cooling fan 22 may be driven by an electrically driven motor in place of using the hydraulic motor. In this case, the number of revolutions of the electrically driven motor can be controlled by controlling a current supplied to the electrically driven motor, whereby an amount of air from the cooling fan 22 can be controlled.
As described above, in the invention, since the aftercooler 21, the cooling fan 22, and the PM filter device 25 are disposed in the cooling passage 20 independent from the engine room 11, a combustion control in the PM filter device 25 and a control of an outer peripheral temperature can be efficiently performed by controlling the amount of air of the cooling fan 22. Moreover, a heat retention control to the PM filter device 25 and a cooling control of the outer periphery can be performed by controlling the amount of air of the cooling fan 22.
Note that the configuration example for controlling the amount of air of the cooling fan 22 using the temperature detected by the temperature sensor 34c as the exhaust gas temperature of the exhaust gas has been described. However, the amount of air of the cooling fan 22 can be controlled using the temperature detected by the temperature sensor 34a or the temperature sensor 34b or can be controlled by appropriately combining appropriate detected values detected by the temperature sensors 34a to 34c.
The cooling device according to the invention can be favorably applied to an work machine including a PM filter device.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2008-278400 | Oct 2008 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2009/066532 | 9/24/2009 | WO | 00 | 3/28/2011 |
