JP2013224665A - Exhaust emission control device in diesel engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure steady execution, in a filter means 50 for exhaust emission purification in a diesel engine 5, of regeneration control thereof, without causing the occurrence of an engine stall in the diesel engine 5.SOLUTION: An exhaust emission control device includes a hydraulic load mechanism 101 of drive in a diesel engine, and an enforcement operation valve means 104 for operating so as to switch between a state of increasing the hydraulic oil pressure of the hydraulic load mechanism and a state of canceling the increase of the hydraulic oil pressure, and is configured to execute regeneration of a filter means 50 by increasing or decreasing an engine load which the diesel engine 5 takes charge, in a state where an engine speed in the diesel engine 5 is kept at a constant or substantially constant level, by the hydraulic load mechanism, when the filter means is clogged.

Description

  The present invention relates to an exhaust gas purifying apparatus for purifying exhaust gas in a diesel engine mounted as a power source in a traveling vehicle such as a traveling type agricultural working vehicle including a tractor and a combine. is there.

  In general, in a diesel engine mounted on a traveling vehicle as a power source, a particulate filter (hereinafter simply referred to as a filter) is used to purify the exhaust gas. In this case, if the PM collected by the filter exceeds a predetermined amount, the flow resistance in the filter is reduced. Since the engine output decreases due to increase and exhaust resistance increase, it is necessary to remove PM accumulated on the filter and restore the PM collection ability of the filter (regenerate the filter).

  This regeneration of the filter is performed when the temperature of the exhaust gas is high. In Patent Document 1 as a prior art, by providing an electrothermal heater in a portion upstream of the filter (diesel engine side) in the exhaust path from the diesel engine, the temperature of the exhaust gas is adjusted by this heater. It is disclosed to raise.

JP 2001-280121 A

  However, in the configuration of Patent Document 1, a dedicated heater is required to raise the temperature of the exhaust gas, so that there is a problem that the number of parts is increased and the cost is increased. In addition, the exhaust gas must be heated locally by the heater, and the exhaust gas cannot be heated uniformly. Therefore, the exhaust gas cannot be purified uniformly, and the temperature of the filter with an oxidation catalyst adjacent to the heater is not good. There has also been a problem that there is a high possibility that damage such as cracking will occur in the filter with an oxidation catalyst.

  The present invention uses the fact that the temperature of exhaust gas in a diesel engine increases in proportion to the engine load that the diesel engine is responsible for, so that the diesel engine does not cause an operation stop or the like. An object of the present invention is to provide an exhaust gas purification device that solves the problem.

  The invention of claim 1 is an exhaust gas purification device for a diesel engine, comprising: exhaust gas purification filter means disposed in an exhaust path from the diesel engine; and a hydraulic load mechanism driven by the diesel engine. In the state where the engine speed in the diesel engine is kept constant or substantially constant, the engine load that the diesel engine is responsible for is increased or decreased by the hydraulic load mechanism to regenerate the filter means.

  According to a second aspect of the present invention, in the exhaust gas purifying apparatus for a diesel engine according to the first aspect, the forced operation is made to switch between a state in which the hydraulic pressure in the hydraulic load mechanism is increased and a state in which the increase in the hydraulic pressure is released. An operation valve means, and when the filter means is clogged, an upper limit engine load lower than a maximum engine load with respect to an engine speed held by the diesel engine, and a lower limit engine load lower than the upper limit engine load. After the setting, if the engine load that the diesel engine is responsible for is lower than the lower limit engine load, while increasing the operating hydraulic pressure in the hydraulic load mechanism by the forced operating valve means, while regenerating the filter means, When the engine load that the diesel engine is responsible for is higher than the upper limit engine load, The forced operating valve means switches the forced operating valve means while maintaining a predetermined engine speed in the diesel engine by releasing the increase in the operating hydraulic pressure in the hydraulic load mechanism and regenerating the filter means. It works.

  According to the present invention, when the filter means for the exhaust gas from the diesel engine is clogged, the hydraulic pressure in the hydraulic load mechanism is increased, so that the engine load that the diesel engine is responsible for increases and the temperature of the exhaust gas increases. Therefore, the filter means can be regenerated. And it can avoid reliably that the traveling speed in working vehicles, such as a tractor, and various working speeds by working machines, such as a rotary tiller, are fluctuate | varied by regeneration execution of a filter main body.

  The forced operating valve means cancels the increase in the operating hydraulic pressure in the hydraulic load mechanism when the engine load exceeds an upper limit engine load set on the lower side of the engine load than the maximum engine load. With this configuration, an increase in engine load by the forced operation valve means can be regulated so as not to exceed the upper limit engine load. Therefore, it is possible to reliably avoid the occurrence of an engine stop (engine stall) in the diesel engine.

  Further, the forced operating valve means cancels the increase in the operating hydraulic pressure in the hydraulic load mechanism when the engine load exceeds an upper limit engine load set on the side of the engine load lower than the maximum engine load. With this configuration, the temperature of the exhaust gas when the filter means is being regenerated can be brought close to the highest exhaust gas temperature at the maximum engine load in the diesel engine. Regeneration can be achieved in a short time.

It is a side view of a tractor. It is a top view of a tractor. It is a functional block diagram which shows the relationship between an engine and an exhaust gas purification apparatus. It is a circuit diagram in the hydraulic load mechanism of a tractor. It is a functional block diagram of an electronic governor controller. It is a figure which shows the relationship between the engine load in an engine, and an engine speed. It is a flowchart of filter regeneration control. It is a functional block diagram which shows the 2nd example of a forced operation valve means. It is a functional block diagram which shows the 3rd example of a forced operation valve means. It is a functional block diagram which shows the 4th example of a forced operation valve means.

  Hereinafter, an embodiment embodying the present invention will be described with reference to the drawings (FIGS. 1 to 10) when applied to a tractor as an example of a traveling vehicle.

(1). Outline of Tractor First, an outline of the tractor 1 will be described with reference to FIGS. 1 and 2.

  The traveling machine body 2 of the tractor 1 is supported by a pair of left and right rear wheels 4 as well as a pair of left and right front wheels 3 as a traveling unit. The tractor 1 is configured to travel forward and backward by driving the rear wheels 4 and the front wheels 3 with a diesel engine 5 mounted on the front portion of the traveling machine body 2.

  The diesel engine 5 is covered with a bonnet 6, and the diesel engine 5 has an oil pan 10 on its lower surface side for storing lubricating oil for lubricating a crankshaft (not shown) in the diesel engine 5. Is provided.

  A cabin 7 is installed on the upper surface of the traveling machine body 2, and a steering handle by a power steering that moves the steering direction of the front wheel 3 to the left and right by steering the steering seat 8 in the cabin 7. (Round handle) 9 is arranged. A fuel tank 11 that supplies fuel to the diesel engine 5 is provided below the bottom of the cabin 7.

  The steering handle 9 in the cabin 7 is provided on a steering column 25 erected in front of the steering seat 8. On the right side of the steering column 25, a throttle lever 30 for setting and maintaining the output speed of the diesel engine 5 and a pair of left and right brake pedals 31 for braking the traveling machine body 2 are arranged.

  On the left side of the steering column 25, there are a forward / reverse switching lever 32 for switching the traveling direction of the traveling machine body 2 between forward and reverse, and a clutch pedal 33 for operating the main clutch (not shown). Has been placed. A parking brake lever 34 is disposed on the rear side of the steering column 25 to hold the left and right brake pedal 31 in the depressed position.

  On the right side of the steering column 25 in the floor plate 28 in the cabin 7, the engine speed set by the throttle lever 30 is within a range between the minimum idle speed Ro and the maximum speed Rx as shown in FIG. An accelerator pedal 35 for increasing and decreasing the speed is arranged.

  On the left side of the control seat 8 are a sub-transmission lever 40 for switching a traveling output from a mission case 17 described later between a low speed and a high speed, and a PTO transmission lever for switching a driving speed of a PTO shaft 23 described later. 36 are arranged. Further, on the right side of the control seat 8, a main speed change lever 38 for shifting operation and a working part position lever 39 for manually changing and adjusting the height position of the rotary tiller 15 described later are arranged. . A differential lock pedal 37 for executing an operation of rotating the left and right rear wheels 4 at a constant speed is disposed below the control seat 8.

  On the other hand, the traveling machine body 2 includes an engine frame 14 having a front bumper 12 and a front axle case 13 and left and right machine body frames 16 that are detachably fixed to the rear portion of the engine frame 14 with bolts. A transmission case 17 is mounted on the rear part of the body frame 16 to transmit the rotational power from the diesel engine 5 to the front and rear four wheels 3, 3, 4, 4 by appropriately shifting the rotational power. The rear wheel 4 is attached to the mission case 17 via a rear axle case 18 mounted so as to protrude outward from the outer surface of the mission case 17. Upper portions of the left and right rear wheels 4 are covered with a fender 19 fixed to the body frame 16.

  On the rear upper surface of the transmission case 17, a hydraulic lifting mechanism 20 for lifting and lowering the rotary tiller 15 and the like as a working unit is detachably attached. The rotary cultivator 15 is connected to the rear portion of the mission case 17 via a three-point link mechanism including a pair of left and right lower links 21 and a top link 22. On the rear side surface of the transmission case 17, a PTO shaft 23 for transmitting a PTO driving force to the rotary tiller 15 is provided so as to project rearward.

  The hydraulic lift mechanism 20 is provided with a pair of left and right lift arms 96 that can be turned up and down by a single-acting lift control hydraulic cylinder 95 (see FIG. 4). The lower link 21 and the lift arm 96 on the left side in the traveling direction are connected via a left lift rod 97. The lower link 21 and the lift arm 96 on the right side in the traveling direction are connected via a double-acting tilt control hydraulic cylinder 98 as a right lift rod and its piston rod 99.

(2). Next, the structure of the diesel engine 5 and its surroundings will be described with reference to FIGS.

  In the tractor 1, the diesel engine 5 as a power source thereof includes a cylinder block (not shown) having a cylinder head 41 fastened to an upper surface, and an oil pan 10 for storing lubricating oil is disposed on the lower surface of the cylinder block. It is concluded. An intake manifold 42 is connected to one side of the cylinder head 41, and an exhaust manifold 43 is connected to the other side.

  A fuel injection pump 44 (see FIG. 5) for feeding fuel into each combustion chamber (sub chamber) of the diesel engine 5 is provided below the intake manifold 42 on the side surface of the cylinder block. Although not shown in detail, an air cleaner is attached to the upstream side of the intake manifold 42 via an intake pipe 45.

  In this case, the air once filtered by the air cleaner is introduced into each cylinder of the diesel engine 5 (inside the cylinder of the intake stroke) via the intake pipe 45 and the intake manifold 42. When the compression stroke of each cylinder is completed, the fuel sucked from the fuel tank 11 is pumped into each combustion chamber (sub chamber) by the fuel injection pump 44, so that the self-ignition combustion of the air-fuel mixture in each combustion chamber. The expansion stroke is performed.

  A particulate filter 50 (hereinafter simply referred to as filter means), which is an example of filter means, is connected to the distal end side of the exhaust manifold 43 via an exhaust pipe 46. The exhaust gas discharged from each cylinder to the exhaust manifold 43 in the exhaust stroke after the expansion stroke is discharged through the exhaust pipe 46 and the filter means 50 and then discharged to the outside.

  The diesel engine 5 is controlled by a controller 80 mounted on the tractor 1 as described below.

  That is, the controller 80 includes an electronic governor 87 provided in a fuel injection pump 44 that is a fuel supply device, a rotation sensor 88 that detects an engine speed R in the diesel engine 5, and a rack position of the fuel injection pump 44. A rack position sensor 89 as load detecting means for detecting the fuel injection amount and a throttle potentiometer 90 for detecting the operation position of the throttle lever 30 are connected.

  When the throttle lever 30 is manually operated, the controller 80 sets an electromagnetic solenoid for driving the rack (not shown) based on the detection information of the throttle potentiometer 90 so that the engine speed R becomes the set speed set by the throttle lever 30. The rack position of the fuel injection pump 44 is adjusted by driving.

  For this reason, the engine speed R in the diesel engine 5 is automatically controlled so as to be maintained at a value corresponding to the position of the throttle lever 30.

  On the other hand, the filter means 50 is for collecting particulate matter (hereinafter referred to as PM) in the exhaust gas, and is provided in a substantially cylindrical filter case 52 in a casing 51 made of a refractory metal material. , For example, an oxidation catalyst 53 of platinum or the like and a filter main body 54 are accommodated in series.

  The filter main body 54 has a honeycomb structure having a large number of cells partitioned by porous (filterable) partition walls.

  An exhaust introduction port 55 communicating with the exhaust pipe 46 is provided on a side surface of one end portion of the casing 51. One end of the casing 51 is closed by a first bottom plate 56, and one end of the filter case 52 facing the first bottom plate 56 is closed by a second bottom plate 57. The annular gap between the casing 51 and the filter case 52 and the gap between the bottom plates 56 and 57 are filled with a heat insulating material 58 such as glass wool so as to surround the oxidation catalyst 53 and the filter body 54. Yes.

  The other side of the casing 51 is closed by two cover plates 59, 60, and a substantially cylindrical exhaust outlet 61 passes through both the cover plates 59, 60. In addition, a resonance chamber 63 that communicates with the inside of the filter case 52 via a plurality of communication pipes 62 is provided between the cover plates 59 and 60.

  An exhaust gas introduction pipe 65 is inserted into an exhaust introduction port 55 formed on a side surface at one end of the casing 51. The tip of the exhaust gas introduction pipe 65 protrudes on the side surface opposite to the exhaust introduction port 55 across the casing 51. A plurality of communication holes 66 opening toward the filter case 52 are formed on the outer peripheral surface of the exhaust gas introduction pipe 65. A portion of the exhaust gas introduction pipe 65 that protrudes from the side surface opposite to the exhaust introduction port 55 is closed by a lid 67 that is detachably screwed thereto.

  The lid 67 is provided with a pressure sensor 68 as an example of clogging detection means for detecting the clogged state of the filter main body 54. The pressure sensor 68 may have a known structure using, for example, a piezoresistance effect. In this case, the pressure Ps (reference pressure value) on the upstream side of the filter 50 when PM is not deposited on the filter body 54 (when the filter 50 is new) is stored in advance in the ROM 82 or the like of the controller 80 described later. The current pressure P at the same measurement location is detected by the pressure sensor 68, the pressure difference ΔP between the reference pressure value Ps and the detected value P of the pressure sensor 68 is obtained, and the filter body 54 is subjected to the pressure difference ΔP. The PM deposition amount is converted (estimated).

  In addition, pressure sensors are disposed on the upstream and downstream sides of the exhaust path of the diesel engine 5 with the filter 50 interposed therebetween, and the PM accumulation amount of the filter main body 54 is converted (estimated) from the difference between the detected values of both. Also good.

  In the above configuration, the exhaust gas from the diesel engine 5 enters the exhaust gas introduction pipe 65 via the exhaust introduction port 55 and is ejected into the filter case 52 from each communication hole 66 formed in the exhaust gas introduction pipe 65. Then, after being dispersed over a wide area in the filter case 52, it passes through the oxidation catalyst 53 in the order of the filter body 54 and is purified. At this stage, the PM in the exhaust gas is collected without passing through the porous partition walls between the cells in the filter main body 54. Thereafter, the exhaust gas that has passed through the oxidation catalyst 53 and the filter body 54 is discharged from the exhaust outlet 61.

  When the exhaust gas passes through the oxidation catalyst 53 and the filter main body 54, if the exhaust gas temperature exceeds a reproducible temperature (for example, about 300 ° C.), the oxidation catalyst 53 causes the NO ( Nitric oxide) oxidizes to unstable NO2 (nitrogen dioxide). Then, PM accumulated in the filter body 54 is oxidized and removed by O (oxygen) released when NO2 returns to NO, so that the PM collecting ability of the filter body 54 is restored (the filter body 54 is regenerated). Will be).

  The power in the diesel engine 5 is output to the transmission case 17 for the tractor 1 to travel, and is also output to the rotary tiller 15 and the power steering mechanism as the working unit. The output is output to the hydraulic load mechanism to be performed and, of course, to other mechanisms.

  As an example of the hydraulic load mechanism, a working unit hydraulic pump 101 and a pilot pump 102 that are driven by the rotational power of the output shaft 24 in the diesel engine 5 are provided.

  The working unit hydraulic pump 101 is for supplying hydraulic oil to a lift control hydraulic cylinder 95 and a tilt control hydraulic cylinder 98 in the hydraulic lift mechanism 20.

  On the other hand, the pilot pump 102 is for adding a pilot pressure to a switching electromagnetic valve 106 described later.

  Both pumps 101, 102 pass through a hydraulic drive shaft 24 protruding from the diesel engine 5, and both pumps 101, 102 are configured to be driven by the rotation of the hydraulic drive shaft 24. That is, the hydraulic drive shaft 24 that drives both the pumps 101 and 102 is a common shaft.

  The suction side of the working unit hydraulic pump 101 is connected to a transmission case 17 as a hydraulic oil tank. The discharge side of the working unit hydraulic pump 101 is connected to the working unit hydraulic circuit 103 via a pressure regulating valve 104 with a back pressure mechanism 105 described later.

  On the other hand, the suction side of the pilot pump 102 is connected to a mission case 17 as a hydraulic oil tank. The discharge side of the pilot pump 102 is connected to the pump-side first port 106 a of the switching electromagnetic valve 106.

  The pressure regulating valve 104 is used to keep the pressure and flow rate on the working unit hydraulic circuit 103 side constant, and to switch the pressure on the discharge side of the working unit hydraulic pump 101 in two stages. Switching between a normal state where there is no pressure increase on the working unit hydraulic pump 101 side and a high pressure state where the pressure on the working unit hydraulic pump 101 side is increased by a predetermined pressure by the elastic force of the spring 105c via the piston 105b. It is configured to operate.

  The switching electromagnetic valve 106 is a three-port two-position switching type that adds pilot pressure from the pilot pump 102 to the back pressure mechanism 105 of the pressure regulating valve 104, and is based on control information from a controller 80 described later. With the excitation of 107, the back pressure mechanism 105 is configured to be switched between a pilot pressure applied state to the back pressure chamber 105a and a pilot pressure discharge state from the back pressure chamber 105a.

  As described above, the pump-side first port 106 a of the switching electromagnetic valve 106 is connected to the discharge side of the pilot pump 102. The pump-side second port 106b of the switching electromagnetic valve 106 is connected to a mission case 17 as a hydraulic oil tank. The back pressure side port 106 c of the switching electromagnetic valve 106 is connected to the back pressure chamber 105 a of the back pressure mechanism 105.

  When the switching solenoid valve 106 is driven to switch to the pilot pressure application state, hydraulic oil from the pilot pump 102 via the switching solenoid valve 106 flows into the back pressure chamber 105a of the back pressure mechanism 105, and the spring 105c via the piston 105b. , The pressure regulating valve 104 is switched to a high pressure state in which the pressure on the working unit hydraulic pump 101 side is increased by a predetermined pressure.

  Then, due to the action of the pressure adjustment valve 104, the discharge pressure (which may be referred to as the operation amount or load) of the working unit hydraulic pump 101 increases, and accordingly, the engine load that the diesel engine 5 takes as a whole is: The total of the engine load for driving driving, the engine load for driving the rotary tiller 15, and the engine load for driving the power steering is added to the discharge pressure on the working unit hydraulic pump 101 side by a predetermined pressure. By adding the engine load corresponding to the increase, the discharge pressure on the working unit hydraulic pump 101 side is increased by a predetermined pressure.

  As a result, in order to maintain the set rotational speed by the throttle lever 30, the engine load (fuel injection amount) that the diesel engine 5 is responsible for increases and the exhaust gas temperature rises.

  When the switching electromagnetic valve 106 is switched to the pilot pressure discharge state, the hydraulic oil flows out from the back pressure chamber 105a of the back pressure mechanism 105, and the spring 105c is extended by its own elastic restoring force, whereby the pressure adjusting valve Due to the action of 104, the discharge pressure of the working unit hydraulic pump 101 is lowered to the normal state, and accordingly, the engine load that the diesel engine 5 is responsible for is reduced.

  In this case, the working unit hydraulic circuit 103 is supplied with hydraulic oil having substantially the same pressure and flow rate as when the pressure regulating valve 104 is not provided, so that the working unit hydraulic circuit 103 caused by the presence of the pressure regulating valve 104 is supplied. The impact will be minimized.

  The combination of the pressure regulating valve 104 and the switching electromagnetic valve 106 corresponds to the forced operation valve means described in the claims. Note that the switching solenoid valve 106 is usually a pilot (when there is no control information from the controller 80) in order to smoothly circulate and supply hydraulic oil between the working unit hydraulic pump 101 and the working unit hydraulic circuit 103. It is in the pressure discharge state. Therefore, the pressure regulating valve 104 is normally in a normal state where there is no pressure increase on the working unit hydraulic pump 101 side.

  As shown in detail in FIG. 4, the working unit hydraulic circuit 103 includes a single-acting lift control hydraulic cylinder 95 and a double-acting tilt control hydraulic cylinder 98. The working unit hydraulic pump 101 includes: A diversion valve 113 is provided for an elevation hydraulic switching valve 111 for controlling the supply of hydraulic oil to the elevation control hydraulic cylinder 95 and an inclination control electromagnetic valve 112 for controlling the supply of hydraulic oil to the inclination control hydraulic cylinder 98. Connected through.

  The raising / lowering hydraulic switching valve 111 is configured to be switched by manual operation of the working unit position lever 39. The tilt control solenoid valve 112 is automatically switched by driving an electromagnetic solenoid corresponding to detection information of a rolling sensor (not shown) and a working unit position sensor (not shown) arranged on the upper surface of the hydraulic lifting mechanism 20. Is configured to do.

  When the lifting hydraulic switching valve 111 is switched by manual operation of the working part position lever 39, the lifting control hydraulic cylinder 95 is driven to expand and contract, and the left and right lift arms 96 are turned up and down. As a result, the rotary tiller 15 moves up and down via the left and right lower links 21.

  Further, when the tilt control electromagnetic valve 112 is automatically switched based on the detection information of the rolling sensor and the work machine position sensor, the tilt control hydraulic cylinder 98 is driven to extend and contract, and the length of the piston rod 99 changes. As a result, the rotary cultivator 15 tilts left and right via the left and right lower links 21. The working unit hydraulic circuit 103 also includes a relief valve, a flow rate adjustment valve, a check valve, and the like (see FIG. 4).

(3). Configuration for Executing Filter Regeneration Control Next, a configuration for executing filter regeneration control will be described with reference to FIGS. 3, 5, and 6. FIG.

  The controller 80 as a control means mounted on the tractor 1 controls the diesel engine 5 as described above and, based on the detection information of the pressure sensor 68 in the filter 50, the pressure adjustment valve 104 in the forced operation valve means. In this pressure adjustment, the filter regeneration control for increasing the engine load L of the diesel engine 5 is executed by increasing the discharge pressure of the working unit hydraulic pump 101, and various arithmetic processes and controls are executed. In addition to the CPU 81, a ROM 82 for storing control programs and data, a RAM 83 for temporarily storing control programs and data, an input / output interface, and the like are provided.

  The controller 80 is connected to a pressure sensor 68 as clogging detection means and an electromagnetic solenoid 107 that controls driving of the switching electromagnetic valve 106.

(4). Description of Filter Regeneration Control Next, an example of filter regeneration control will be described with reference to FIGS. 6 and 7.

  FIG. 6 shows an engine load line LP between an arbitrary engine speed R between the minimum idle speed Ro and the maximum speed Rx and the maximum engine load Lx at the time when the diesel engine 5 is driven. This engine load line LP has an upwardly convex shape as shown by a solid line, and within the range of the engine load line LP, all the driving in the tractor 1, that is, traveling drive, rotary tiller All driving such as 15 driving, driving of the hydraulic load mechanism and driving of the power steering are totally borne.

  Further, since the temperature of the exhaust gas within the range of the engine load line LP is proportional to the engine load, the temperature of the exhaust gas inside the engine load line LP is a temperature at which the filter 50 can be regenerated. It is divided up and down at the boundary line BL in the case of (for example, about 300 ° C.).

  The upper region across the boundary line BL is a reproducible region in which PM deposited on the filter main body 54 can be oxidized and removed (the oxidation action by the oxidation catalyst 53 works), and the lower region is obtained by oxidizing and removing PM. This is a non-renewable area that accumulates on the filter main body 54.

  Further, in the upper reproducible region across the boundary line BL, there is an upper limit engine load line at the position of the upper limit engine load LS1 that is appropriately lower than the maximum engine load Lx at an arbitrary engine speed R by a load ΔL1. LS1 ′ is set so as to extend substantially parallel to the engine load line LP, as indicated by the alternate long and short dash line.

  In addition, the lower limit engine load line LS2 ′ is a two-dot chain line at the position of the lower limit engine load LS2 that is appropriately lower than the upper limit engine load LS1 by a load ΔL2 in the upper region across the boundary line BL. As shown in FIG. 4, the engine load line LP is set so as to extend substantially in parallel.

  Each of the engine load line LP, the upper limit engine load line LS1 ′, and the lower limit engine load line LS2 ′ is set in advance by, for example, storing it as a map in the ROM 82 or the like of the controller 80. Both the engine load line LS1 'and the lower limit engine load line LS2' are used as triggers for switching operation in the forced operation valve means.

  The flow of filter regeneration control will be described using the flowchart shown in FIG.

  First, in step S1 following the start, the reference pressure value Ps and the detected value P of the pressure sensor 68 are read, and in step S2, it is determined whether or not PM is deposited on the filter body 54. Is determined (NO), the process returns as it is. However, when it is determined that PM is deposited (YES), the process proceeds to step S3.

  In this step S3, the engine load L at a predetermined engine speed R on the engine load line LP, the upper limit engine load LS1 at the predetermined engine speed R on the upper limit engine load line LS1 ′, and the lower limit engine load. After reading the lower limit engine load LS2 at the predetermined engine speed R on the line LS2 ′, the routine proceeds to step S4, where the engine load L at the predetermined engine speed R is smaller than the lower limit engine load LS2. Determine whether or not.

  In step S4, when it is determined that the engine load L at the predetermined engine speed R is smaller than the lower limit engine load LS2 (YES), the process proceeds to step S5, and the pressure regulating valve in the forced operation valve means 104 is operated to switch the switching electromagnetic valve 106 to the pilot pressure application state.

  As a result, the engine load that the diesel engine 5 is responsible for increases the amount of discharge pressure on the working unit hydraulic pump 101 side by a predetermined pressure to increase the exhaust gas temperature. 54 playback is executed.

  On the other hand, when it is determined in step S4 that the engine load L at the predetermined engine speed R is greater than the lower limit engine load LS2 (NO), the process proceeds to step S6, thereby shifting to step S6. In step S1, it is determined whether or not the engine load L at a predetermined engine speed R is larger than the upper limit engine load LS1.

  In this step S6, when it is determined that the engine load L at the predetermined engine speed R is smaller than the upper limit engine load LS1 (NO), the regeneration of the filter main body 54 by the forced operation valve means is performed as it is. Will continue.

  On the other hand, when it is determined in step S6 that the engine load L at the predetermined engine speed R is larger than the upper limit engine load LS1 (YES), the process proceeds to step S7, and the forced operation valve By stopping the operation of the pressure regulating valve 104 in the means and switching the switching electromagnetic valve 106 to the pilot pressure discharge state, the increase in the engine load by the forced operation valve means is released.

  Next, in step S8, the state of the switching operation described above is maintained until an appropriate predetermined time elapses, and when this predetermined time elapses, the process proceeds to step S9, where, as in step S1, After reading the reference pressure value Ps and the detected value P of the pressure sensor 68, the process proceeds to step S10. In this step S10, it is determined whether or not PM is deposited on the filter body 54.

  If it is determined in step S10 that PM has accumulated on the filter main body 54 (YES), the process returns to step S3 and the above is repeated.

  On the other hand, when it is determined in step S10 that PM is not deposited on the filter main body 54 (NO), the process proceeds to step S11, and the operation of the pressure regulating valve 104 in the forced operation valve means is stopped. The switching electromagnetic valve 106 is switched to the pilot pressure discharge state to cancel the increase in engine load due to the forced operation valve means.

  When the filter main body 54 is clogged with respect to the exhaust gas from the diesel engine 5 by the above control, the operating hydraulic pressure in the hydraulic load mechanism is increased by the forced operating valve means, so that the engine load that the diesel engine 5 takes over is increased. And the temperature of the exhaust gas increases, so that the filter main body 54 can be regenerated.

  In this case, when the engine load exceeds the upper limit engine load LS1 set on the side of the engine load that is appropriately lower than the maximum engine load Lx by a load ΔL1, the forced operation valve means is provided in the hydraulic load mechanism. By being configured to cancel the increase in operating hydraulic pressure, the increase in engine load by the forced operation valve means can be restricted so as not to exceed the upper limit engine load LS1.

  In this case, the upper limit engine load LS1, which is set to the side lower than the maximum engine load Lx as appropriate by the load ΔL1, is made closer to the maximum engine load Lx, that is, by reducing the load ΔL1. The temperature of the exhaust gas can be increased, but on the other hand, when the engine load is increased by the forced operation valve means, the frequency at which the operation stop (engine stall) occurs in the diesel engine 5 increases. Therefore, it is preferable to set the frequency at which the operation stop (engine stall) occurs in the diesel engine 5 to a value that can reliably reduce the frequency. The filter main body 54 can be reliably regenerated under the reduced condition.

  On the other hand, when the engine load L exceeds the upper limit engine load LS1, and the increase in the operating hydraulic pressure by the hydraulic load mechanism is released, the engine load L decreases. When the decrease in the engine load L falls below the lower limit engine load LS2, the hydraulic pressure is increased again by the hydraulic load mechanism, and the engine load L is kept high.

  In this case, the lower limit engine load LS2 can increase the temperature of the exhaust gas as it is brought closer to the upper limit engine load LS1, that is, the load ΔL2 is appropriately reduced. it can.

  However, the smaller the load ΔL2, the more frequently the switching operation of the forced operation valve means is performed, which not only causes control instability due to hunting, but also decreases the durability of the forced operation valve means. Therefore, it is preferable to set in consideration of this point.

  Further, in step S8 during the above-described control, the state of the switching operation in the forced operation valve means is maintained until an appropriate predetermined time elapses, whereby the number of switching operations in the forced operation valve means. Can be reduced and its durability can be improved, and hunting can be prevented and control stability can be improved.

  In particular, in the above-described embodiment, the filter load 54 is increased or decreased by the hydraulic load mechanism in the state where the engine speed in the diesel engine 5 is kept constant or substantially constant by the hydraulic load mechanism. In other words, since the forced operation valve means is switched and operated while maintaining a predetermined engine speed, the traveling speed of the tractor 1 and the rotary tiller It is possible to reliably avoid the various working speeds due to 15 etc. from fluctuating due to the regeneration execution of the filter main body 54.

(5). FIG. 8 shows a second example of the forced operation valve means.

  In this second example, the pilot pump 102 of the first embodiment is eliminated, and the pump-side first port 106a of the switching electromagnetic valve 106 is connected to the discharge side of the working-unit hydraulic pump 101. It is different. Other configurations are the same as those of the first embodiment.

  Furthermore, in this second example, as shown in FIG. 8, the pressure regulating valve 104 can be controlled by the self-pressure of the hydraulic oil discharged from the working unit hydraulic pump 101.

  That is, the discharge side of the working unit hydraulic pump 101 is branched and connected to the pump-side first port 106a of the switching solenoid valve 106, and a self-pressure is applied to the back pressure chamber 105a of the back pressure mechanism 105 by a switching command from the controller 80. What is necessary is just to comprise so that it may flow in. In this case, by switching the piston cross-sectional area of the back pressure chamber 105a to be larger than the cross-sectional area of the pressure adjusting valve 104, the switching operation (pressure adjustment) of the pressure adjusting valve 104 becomes possible. By adopting such a configuration, the number of necessary pumps can be reduced as compared with the case of the first embodiment, which simplifies the configuration and contributes to the reduction of manufacturing costs.

  FIG. 9 shows a third example of forced operation valve means.

  The third example is different from the above-described embodiment in that the switching electromagnetic valve 106 of the ON / OFF control type is changed to a pilot pressure adjusting electromagnetic valve 116 capable of adjusting the hydraulic oil supply pressure to the back pressure chamber 105a. doing.

  The pilot pressure adjusting electromagnetic valve 116 is configured to adjust the pilot pressure applied to the back pressure chamber 105 a of the back pressure mechanism 105 by excitation of the electromagnetic solenoid 117 based on control information from the controller 80. Therefore, the discharge pressure on the working unit hydraulic pump 101 side in the pressure adjusting valve 104 is adjusted according to the hydraulic oil supply pressure via the pilot pressure adjusting electromagnetic valve 116. The pressure on the working unit hydraulic circuit 103 side in the pressure regulating valve 104 is kept constant as in the first embodiment.

  The pilot pressure adjusting electromagnetic valve 116 is normally set so that pilot pressure is not applied to the pressure adjusting valve 104 (when there is no control information from the controller 80). Other configurations are the same as those of the first embodiment.

  FIG. 10 shows a fourth example of forced operation valve means.

  In the fourth example, the pressure adjustment valve 104 is controlled by the self-pressure of the hydraulic oil discharged from the working unit hydraulic pump 101.

  That is, the discharge side of the working unit hydraulic pump 101 is branched and connected to the suction side of the pilot pressure adjusting solenoid valve 116, and the self-pressure flows into the back pressure chamber 105 a of the back pressure mechanism 105 by a switching command from the controller 80. The other configurations are the same as those in the first embodiment.

(7). Others As described above, the present invention is not limited to the case where the present invention is applied to a diesel engine mounted on a tractor, but is applied to a traveling agricultural work vehicle such as a combine or a riding rice transplanter, or a diesel engine mounted on another traveling vehicle. It goes without saying that can also be applied.

Reference Signs List 1 tractor 5 diesel engine 30 throttle lever 44 fuel injection pump 50 particulate filter (filter means)
53 Oxidation catalyst 54 Filter body 68 Pressure sensor (clogging detection means)
80 Controller as Control Unit 87 Electronic Governer 88 Engine Rotation Sensor 89 Rack Position (Engine Load) Sensor 101 Working Unit Hydraulic Pump (Hydraulic Load Mechanism)
104 Pressure control valve (forced operation valve means)
106 Switching solenoid valve

Claims (2)

A filter means for purifying exhaust gas disposed in an exhaust path from the diesel engine, and a hydraulic load mechanism driven by the diesel engine,
A diesel engine characterized in that regeneration of the filter means is executed by increasing / decreasing an engine load that the diesel engine takes over with the hydraulic load mechanism in a state where the engine speed in the diesel engine is kept constant or substantially constant. Exhaust gas purification device. Forcibly operating valve means adapted to switch between a state in which the operating oil pressure in the hydraulic load mechanism is increased and a state in which the increase in operating oil pressure is released;
When the filter means is clogged, after setting an upper limit engine load lower than the maximum engine load with respect to the engine speed held by the diesel engine and a lower limit engine load lower than the upper limit engine load, the diesel engine When the engine load handled by the diesel engine is lower than the lower limit engine load, the forced hydraulic valve means increases the hydraulic pressure in the hydraulic load mechanism to regenerate the filter means, while the diesel engine handles the engine load. Is higher than the upper limit engine load, the increase of the operating hydraulic pressure in the hydraulic load mechanism is canceled by the forced operating valve means, and the filter means is regenerated, so that a predetermined engine speed in the diesel engine is restored. The forced operation valve means is switched and operated while maintaining Exhaust gas purifying device in a diesel engine according to claim 1,.

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