JP4847219B2 - Exhaust gas purification equipment for construction machinery - Google Patents

Description

  The present invention relates to an exhaust gas purification apparatus for a construction machine that is provided in a construction machine such as a hydraulic excavator and that can purify exhaust gas discharged from an engine that drives a hydraulic pump.

  Construction machines, such as hydraulic excavators, include an engine and a hydraulic pump driven by the engine, and the torque is controlled so that the absorption torque of the hydraulic pump does not exceed the output torque of the engine. In addition, a hydraulic drive circuit to which pressure oil of a hydraulic pump is supplied is provided. The hydraulic drive circuit includes a boom cylinder for driving a working machine such as a boom and an arm, a hydraulic actuator such as an arm cylinder, a turning body, and a traveling body. Includes hydraulic actuators such as a swing motor and a traveling motor for driving the motor, and hydraulic equipment such as a directional control valve for controlling the operation of these hydraulic actuators. In a hydraulic excavator having such a configuration, it has recently been desired to purify exhaust gas discharged from an engine.

  As a prior art for purifying exhaust gas, there is one disclosed in Patent Document 1. Unlike the construction machine targeted by the present invention, this prior art is an exhaust gas purifying device provided in an automobile. However, this prior art is a process for purifying nitrogen oxides in exhaust gas discharged from an engine by a reducing agent such as urea. Exhaust gas control means to be performed, a reducing agent solution tank for storing a reducing agent solution such as urea water supplied to the exhaust gas control means, and a liquid level sensor for detecting the remaining amount of the reducing agent solution stored in the reducing agent solution tank That is, a remaining amount detecting means is provided. Also provided is an alarm device that is activated to notify the driver when the remaining amount of the reducing agent solution stored in the reducing agent solution tank becomes a predetermined amount or less.

In this prior art, when the remaining amount of the reducing agent solution becomes a predetermined amount or less, the alarm is activated as described above to inform the driver, and the engine control unit controls the engine to low output, By these, replenishment of the reducing agent solution is promoted.
JP 2002-371831 A

  The prior art disclosed in Patent Document 1 described above is considered effective for purifying exhaust gas in automobiles, but cannot be applied to construction machines such as hydraulic excavators as they are. For example, a hydraulic excavator is provided with a hydraulic pump that is driven by an engine and supplies pressure oil for driving a boom, an arm, a turning body, a traveling body, and the like to a corresponding hydraulic actuator. The relationship with the output of is important. As in the above-described prior art, when the engine is controlled to a low output when the remaining amount of the reducing agent solution becomes a predetermined amount or less, the load on the hydraulic pump becomes larger depending on the type of work. There is a risk that an excavation work, a suspended load work, etc., which have been performed until then, will be interrupted.

  The present invention has been made from the above-described prior art, and an object of the present invention is to provide an exhaust gas purifying apparatus suitable for a construction machine including a hydraulic pump driven by an engine.

In order to achieve this object, the present invention provides an engine, a variable displacement hydraulic pump that is driven by the engine and whose absorption torque is controlled so as not to exceed the output torque of the engine, and a tilt of the variable displacement hydraulic pump. A construction machine having a regulator for controlling a turning angle and a hydraulic drive circuit including a plurality of hydraulic actuators supplied with pressure oil discharged from the variable displacement hydraulic pump is provided in an exhaust gas discharged from the engine. Exhaust gas control means for performing a treatment for purifying nitrogen oxides, a reducing agent solution tank for storing a reducing agent solution supplied to the exhaust gas control means, and a remaining amount of the reducing agent solution stored in the reducing agent solution tank. provided with a remaining amount detecting means for detecting that, when the remaining amount of the reducing agent solution to be detected by the remaining amount detection means has decreased to the first predetermined amount A warning informing means for informing a warning that requires replenishment of the reducing agent solution, the less than the first predetermined amount remaining amount from said first predetermined amount of the reducing agent solution to be detected by the level detecting means while reduced to second predetermined amount, the state quantity related to the driving of the variable displacement hydraulic pump, have gradually row control to decrease to a predetermined value within a range the operation of the hydraulic actuator is possible, the remaining amount detection State quantity control means for maintaining the state quantity at the predetermined value within a range in which the hydraulic actuator can be operated when the remaining amount of the reducing agent solution detected by the means decreases below the second predetermined quantity ; the provided, the variable displacement hydraulic pump, in a state in which the state quantity related to the driving of the variable displacement hydraulic pump by the state quantity control means is controlled, the tilt angle by the regulator is controlled, the intake Torque is characterized in that it is in the torque control does not exceed the output torque of the engine.

  In the present invention configured as described above, sufficient reducing agent solution is supplied to the exhaust gas control means until the remaining amount of the reducing agent solution in the reducing agent solution tank reaches a predetermined amount, and is thereby discharged from the engine. Nitrogen oxides in the exhaust gas are purified, and clean exhaust gas can be discharged. When the remaining amount of the reducing agent solution in the reducing agent solution tank reaches a predetermined amount, it is detected by the remaining amount detecting means, and a warning is notified by the warning notification means. In addition, the state quantity control means operates in response to the detection of the remaining quantity detection means, and the state quantity related to the driving of the hydraulic pump, for example, the pump absorption torque, the flow rate of the hydraulic pump, or the discharge pressure of the hydraulic pump is compared with that during normal operation. In other words, control for decreasing the state quantity to a predetermined value within a range in which the hydraulic actuator can be operated is performed.

  As a result, even when the remaining amount of the reducing agent solution in the reducing agent solution tank becomes equal to or less than the predetermined amount, the exhaust gas of the engine whose load is reduced by reducing the state quantity related to the driving of the hydraulic pump is reduced. Is continued, and clean exhaust gas can be discharged. Moreover, it is urged | required that it is necessary to replenish a reducing agent solution with the alerting | reporting of the above-mentioned warning by workability | operativity falling. Further, although the workability is reduced as described above by the control of the state quantity control means, the operation of the hydraulic actuator can be continued within the limited range, so that the work can be continued.

According to the present invention, in the above invention, the state quantity is pump absorption torque, the state quantity control means includes pump absorption torque control means, and the variable displacement hydraulic pump is controlled by the pump absorption torque control means. According to the pump absorption torque, the tilt angle is controlled by the regulator, and the torque is controlled so that the absorption torque does not exceed the output torque of the engine .

Further, the present invention is the above invention, wherein the state quantity is a flow rate discharged from the variable displacement hydraulic pump, the state quantity control means comprises flow rate control means, and the variable displacement hydraulic pump is controlled by the flow rate control means. According to the controlled flow rate, while the tilt angle is controlled by the regulator, the torque is controlled so that the absorption torque does not exceed the output torque of the engine .

Further, the present invention is characterized in that, in the above invention, the state quantity is a discharge pressure of the variable displacement hydraulic pump, and the state quantity control means comprises a discharge pressure control means.

  Further, the present invention is characterized in that, in the above-mentioned invention, the reducing agent solution is composed of urea water.

  Further, the present invention is characterized in that, in the above invention, the warning notification means comprises an alarm lamp.

The present invention relates to a variable displacement hydraulic pump whose absorption torque is controlled so as not to exceed the output torque of the engine, a regulator that controls the tilt angle of the variable displacement hydraulic pump, and an engine that drives the variable displacement hydraulic pump. The exhaust gas control means for purifying the nitrogen oxides in the exhaust gas to be discharged and the reducing agent solution tank for storing the reducing agent solution supplied to the exhaust gas control means are provided. Can be purified. The present invention also provides a remaining amount detecting means for detecting the remaining amount of the reducing agent solution stored in the reducing agent solution tank, and the remaining amount of the reducing agent solution detected by the remaining amount detecting means is reduced to a first predetermined amount. when a warning informing means for informing a warning that requires replenishment of the reducing agent solution, less than the remaining amount is the first predetermined amount from the first predetermined amount of the reducing agent solution to be detected by the remaining amount detecting means while decreases to a second predetermined amount, the state quantity related to the driving of the variable capacity hydraulic pump, have gradually row control to decrease to a predetermined value within a range of hydraulic actuator operation is possible, in the remaining amount detecting means State quantity control means for maintaining the state quantity at a predetermined value within a range in which the hydraulic actuator can be operated when the remaining amount of the reducing agent solution to be detected is reduced below the second predetermined quantity , and the variable capacity The hydraulic pump is used as the state quantity control means. In a state in which the state quantity related to the driving of the variable displacement hydraulic pump is controlled me, and the tilt angle by the regulator is controlled and the torque control so that the absorption torque does not exceed the output torque of the engine Therefore, when the remaining amount of the reducing agent solution in the reducing agent solution tank becomes a predetermined amount or less, the exhaust gas purification of the engine with the load reduced by reducing the state quantity related to the driving of the hydraulic pump is reduced. Can be continued, and a warning is issued to reduce workability, thereby prompting replenishment of the reducing agent solution. In addition, although it is within the limited range, the operation can be continued without causing an engine stall. Therefore, an apparatus suitable for a construction machine can be realized.

  Hereinafter, the best mode for carrying out an exhaust gas purifying apparatus for a construction machine according to the present invention will be described with reference to the drawings.

  FIG. 1 is a hydraulic circuit diagram showing a first embodiment of an exhaust gas purifying apparatus for a construction machine according to the present invention, FIG. 2 is a block diagram showing a main part configuration of a controller provided in the first embodiment shown in FIG. These are the figures which show the characteristic acquired by 1st Embodiment of this invention.

  A first embodiment of the present invention shown in FIG. 1 is provided in a construction machine such as a hydraulic excavator. The hydraulic excavator includes an engine 1 and a variable displacement hydraulic pump 2 driven by the engine 1. Torque control is performed so that the absorption torque of the hydraulic pump 2 does not exceed the output torque of the engine 1. In addition, a rotation speed instruction device 3 that instructs the target rotation speed of the engine 1, a regulator 4 that controls the displacement of the hydraulic pump 2, a main relief valve 5 that regulates the maximum discharge pressure of the hydraulic pump 2, A rotation control means 6 for controlling the rotation speed, and a controller 7 for outputting a control signal corresponding to the target rotation speed designated by the rotation speed instruction device 3 to the rotation control means 6 and a drive signal for driving the regulator 4. It has.

  Furthermore, a hydraulic drive circuit 8 to which pressure oil discharged from the hydraulic pump 2 is supplied is provided. The hydraulic drive circuit 8 includes a boom cylinder that drives a work machine such as a boom and an arm, a hydraulic actuator such as an arm cylinder, or a hydraulic actuator such as a swing body, a swing motor that drives the traveling body, and a travel motor. Hydraulic equipment such as a directional control valve for controlling the operation of the hydraulic actuator is included.

  The exhaust gas purifying apparatus according to the first embodiment provided in such a hydraulic excavator is supplied to the exhaust gas control means 9 that performs a process of purifying nitrogen oxides in the exhaust gas discharged from the engine 1 and to the exhaust gas control means 9. A reducing agent solution tank for storing a reducing agent solution, for example, urea water, that is, a urea water tank 10 and a remaining amount detecting means 11 for detecting the remaining amount of urea water stored in the urea water tank 10 are provided. .

  Further, when the remaining amount of urea water detected by the remaining amount detecting means 11 decreases to a first predetermined amount A described later, a warning notifying means for notifying that urea water needs to be replenished, for example, an alarm lamp 12 It has.

  Further, as will be described later, as the remaining amount of urea water in the urea water tank 10 detected by the remaining amount detecting means 11 decreases from the first predetermined amount A, a state amount related to driving of the hydraulic pump 2, for example, State amount control means, for example, pump absorption torque control means, is provided for performing control to reduce the pump absorption torque to a predetermined value within a range in which the hydraulic actuator included in the hydraulic drive circuit 8 described above can be operated. This pump absorption torque control means is included in the controller 7.

  As shown in FIG. 2, the controller 7 includes an on / off signal generator 7 a that outputs an on signal or an off signal to the alarm lamp 12 in accordance with a detection signal output from the remaining amount detecting means 11. ing. The on / off signal generator 7a outputs an off signal until the remaining amount of the urea water tank 10 becomes the first predetermined amount A, and outputs an on signal when the remaining amount becomes the first predetermined amount A or less.

  The controller 7 also includes a pump absorption torque calculator 7b that calculates the maximum pump absorption torque M of the hydraulic pump 2 that does not exceed the output torque of the engine 1 during normal operation.

  In particular, the controller 7 selects the function generator 7c, the signal S1 output from the function generator 7c, and the signal S2 output from the pump absorption torque calculator 7b, whichever is smaller in value. And a minimum value selector 7d that outputs to the regulator 4 as a drive signal. The function generating unit 7c and the minimum value selecting unit 7d constitute a pump absorption torque control unit that is the state quantity control unit described above.

  The function generator 7c outputs a signal S1 corresponding to the maximum pump absorption torque M until the remaining amount of the urea water tank 10 reaches the first predetermined amount A, and the remaining amount becomes equal to or less than the first predetermined amount A. Sometimes, a signal S1 for gradually decreasing the value according to the decrease in the remaining amount is output, and when the remaining amount decreases below the second predetermined amount B smaller than the first predetermined amount A, for example, the maximum pump absorption torque M The function relationship is such that a signal S1 corresponding to a limit torque m of 70% is output. Note that the second predetermined amount B that gives the limit torque m described above is a predetermined value within a range in which the hydraulic actuator included in the hydraulic drive circuit 8 can be operated.

  In the first embodiment configured as described above, sufficient urea water is supplied to the exhaust gas control means 9 until the remaining amount of urea water in the urea water tank 10 reaches the first predetermined amount A. The nitrogen oxide in the exhaust gas discharged from 1 is purified, and clean exhaust gas can be discharged. During this time, the detection signal of the remaining amount detecting means 11 is input to the controller 7, an off signal is output from the on / off signal generator 7a shown in FIG. 2 to the alarm lamp 12, and the alarm lamp 12 is kept in the extinguished state. Further, a signal S2 corresponding to the maximum pump absorption torque M is output from the function generation unit 7c, and a drive signal corresponding to the maximum pump absorption torque M is output to the regulator 4 from the signals S1 and S2 in the minimum value selection unit 7d. Is done. As a result, the regulator 4 is operated, and the maximum pump absorption torque M is controlled so that the tilt angle of the hydraulic pump 2 does not exceed the output torque of the engine 1. A characteristic line 13 in FIG. 3 is a PQ characteristic line corresponding to the maximum pump absorption torque M at this time.

  When the urea water in the urea water tank 10 decreases from the above state and the remaining amount of the urea water detected by the remaining amount detecting means 11 reaches the first predetermined amount A, the on / off signal generator 7a of the controller 7 is reached. Is output to the alarm lamp 12. As a result, the alarm lamp 12 is turned on. Further, as the remaining amount of urea water decreases from the first predetermined amount A, the alarm lamp 12 is kept on, and the signal S1 output from the function generator 7c gradually becomes smaller than the maximum pump absorption torque M. The small value is selected by the minimum value selector 7d, and a drive signal corresponding to the small value is output to the regulator 4. As a result, the tilt angle of the hydraulic pump 2 is controlled to gradually decrease, and the PQ characteristic shown in FIG. 3, that is, the pump absorption torque is controlled to gradually decrease as indicated by the arrows in FIG. Is done.

  Further, when the remaining amount in the urea water tank 10 decreases and the remaining amount detected by the remaining amount detecting means 11 becomes equal to or less than the second predetermined amount B, the warning lamp 12 is kept on and the function generator 7c The output signal S1 has a value corresponding to the limit torque m, the limit torque m is selected by the minimum value selection unit 7d, and a drive signal corresponding to the limit torque m is output to the regulator 4. Accordingly, the tilt angle of the hydraulic pump 2 is limited to be further reduced, and the PQ characteristic shown in FIG. 3, that is, the pump absorption torque is shown by the characteristic line 14.

  When this state is reached, the time required for one work cycle, such as the work of excavating debris with this excavator and loading the excavated debris on a dump truck, becomes slower than in normal work, and workability is reduced.

  As described above, even if the remaining amount of urea water in the urea water tank 10 is equal to or less than the second predetermined amount B, the exhaust gas of the engine 1 that has been reduced in load as the pump absorption torque is reduced is purified. Is continued, and clean exhaust gas can be discharged.

  As described above, according to the first embodiment, the exhaust gas control means 9 that performs the process of purifying nitrogen oxides in the exhaust gas discharged from the engine 1 that drives the hydraulic pump 2, and the exhaust gas control means 9 Since the urea water tank 10 for storing the supplied urea water is provided, the exhaust gas discharged from the engine 1 can be purified.

  Further, the remaining amount detecting means 11 for detecting the remaining amount of the urea water stored in the urea water tank 10 and the remaining amount of the urea water detected by the remaining amount detecting means 11 are reduced to the first predetermined amount A. In addition, the alarm lamp 12 for notifying that the urea water needs to be replenished and the hydraulic pump 2 is driven as the remaining amount of the urea water detected by the remaining amount detecting means 11 decreases from the first predetermined amount A. Control that reduces the related pump absorption torque to a predetermined value within a range in which the hydraulic actuator included in the hydraulic drive circuit 8 can be operated, that is, to a limit torque m that is, for example, 70% of the maximum pump absorption torque M. When the remaining amount of urea water in the urea water tank 10 is equal to or less than the first predetermined amount A, the function generating unit 7c and the minimum value selecting unit 7d included in the pump absorption torque control means for performing Hydraulic port State quantity related to the flop 2, or load along with reducing the pump absorption torque can be continued purification of exhaust gas of the engine 1 is reduced.

  At the same time, the alarm lamp 12 is turned on, and the workability is also lowered, so that the supply of urea water is promoted, and the work can be continued without causing an engine stall within a limited range. It becomes. Therefore, a device suitable for this hydraulic excavator can be realized.

  FIG. 4 is a block diagram showing a main part configuration of a controller provided in the second embodiment of the present invention, and FIG. 5 is a diagram showing characteristics obtained in the second embodiment of the present invention.

  In the second embodiment of the present invention, the controller 7 calculates the discharge flow rate of the hydraulic pump 2 in accordance with the rotational speed of the engine 1 in addition to the on / off signal generator 7a equivalent to that in the first embodiment. Then, a pump discharge flow rate calculation unit 7e that outputs a signal S4 corresponding to the calculated value and a function generation that outputs a signal S3 corresponding to a flow rate corresponding to a value corresponding to the remaining amount of urea water in the urea water tank 10 are generated. 7f, the minimum value to be output to the regulator 4 as a drive signal by selecting the smaller one of the signal S3 output from the function generator 7f and the signal S4 output from the pump discharge flow rate calculator 7e And a selector 7g.

  As the remaining amount of urea water detected by the remaining amount detecting means 11 decreases from the predetermined amount by the function generating unit 7f and the minimum value selecting unit 7g, the state amount related to driving of the hydraulic pump 2, for example, the hydraulic pressure A flow rate control means for controlling the flow rate discharged from the pump 2 to a predetermined value within a range in which the hydraulic actuator included in the hydraulic drive circuit 8 can be operated, that is, a state quantity control means is configured.

  The function generator 7f outputs a signal S3 corresponding to the maximum flow rate Q corresponding to the rotational speed of the engine 1 until the remaining amount of urea water in the urea water tank 10 reaches the first predetermined amount A, and the remaining amount is When the amount falls below the first predetermined amount A, a signal S3 whose value is gradually decreased in response to a decrease in the remaining amount of the urea water tank 10 is output, and the remaining amount of the urea water tank 10 is greater than the first predetermined amount A. Is smaller than the second predetermined amount B, for example, a signal S3 corresponding to a limited flow rate q that is 70% of the maximum flow rate Q during normal operation is output. Note that the second predetermined amount B that gives the limit flow rate q is a predetermined value within a range in which the hydraulic actuator included in the hydraulic drive circuit 8 can be operated.

  Other configurations are the same as those of the first embodiment described above.

  In the second embodiment configured as described above, sufficient urea water is supplied until the remaining amount of urea water in the urea water tank 10 reaches the first predetermined amount A, as in the first embodiment. As a result, nitrogen oxides in the exhaust gas are purified, and clean exhaust gas can be discharged. Further, the alarm lamp 12 is kept off. Further, since the signal S3 output from the function generation unit 7f of the controller 7 and the signal S4 output from the pump discharge flow rate calculation unit 7e have the same value, the minimum value selection unit 7g changes the rotational speed of the engine 1. A drive signal corresponding to the corresponding maximum flow rate Q is output to the regulator 4. As a result, the PQ characteristic line in FIG. 5 becomes the characteristic line 13 as in the first embodiment described above.

  From this state, when the urea water in the urea water tank 10 decreases and the remaining amount of urea water detected by the remaining amount detecting means 11 reaches the first predetermined amount A, the alarm lamp 12 is turned on. Further, as the remaining amount of urea water decreases from the first predetermined amount A, the lighting of the alarm lamp 12 is maintained, and the signal S3 output from the function generator 7f gradually becomes smaller than the maximum flow rate Q, This small value is selected by the minimum value selector 7g, and a drive signal corresponding to the small value is output to the regulator 4. Thereby, the PQ characteristic shown in FIG. 5, that is, the flow rate of the hydraulic pump 2 is controlled so as to gradually decrease as shown by the arrow in FIG.

  Further, when the urea water in the urea water tank 10 decreases to become the second predetermined amount B or less, the warning lamp 12 is kept on, and the signal S3 output from the function generator 7f corresponds to the limit flow rate q. The drive signal corresponding to this value is output from the minimum value selector 7g to the regulator 4. As a result, the PQ characteristic shown in FIG.

  When this state is reached, the maximum flow rate supplied to the hydraulic actuator included in the hydraulic drive circuit 8 is limited to the limited flow rate q, so that the operating speed of the hydraulic actuator becomes slower than the operating speed during normal work. And workability is reduced.

  Even when the remaining amount of urea water in the urea water tank 10 is equal to or less than the second predetermined amount B as described above, the load is reduced by reducing the flow rate discharged from the hydraulic pump 2. Purification of the exhaust gas from the engine 1 is continued, and clean exhaust gas can be discharged.

  The second embodiment configured as described above can also purify the exhaust gas discharged from the engine 1 as in the first embodiment described above.

  Further, when the remaining amount of urea water detected by the remaining amount detecting means 11 becomes the first predetermined amount A or less, the alarm lamp 12 is turned on.

  Further, when the remaining amount of the urea water detected by the remaining amount detecting means 11 becomes equal to or less than the first predetermined amount A, the flow rate discharged from the hydraulic pump 2 is gradually reduced due to the restriction and is equal to or less than the second predetermined amount B. Then, the flow rate decreases to the limit flow rate q which is 70% of the maximum flow rate Q. Even when the remaining amount of urea water is equal to or less than the second predetermined amount B in this way, it is possible to continue the purification of the exhaust gas of the engine 1 with a reduced load.

  Then, as described above, the alarm lamp 12 is turned on, and the workability is lowered at the same time, so that the urea water is replenished. Further, it is possible to continue the operation by supplying pressure oil to the hydraulic actuator without causing an engine stall within a limited range.

  FIG. 6 is a hydraulic circuit diagram showing a third embodiment of the present invention, and FIG. 7 is a block diagram showing a main configuration of a controller provided in the third embodiment of the present invention.

  As shown in FIG. 6, in the third embodiment of the present invention, in addition to the configuration of the first embodiment described above, an electromagnetic valve 16 capable of controlling the discharge pressure of the main relief valve 5, and a pilot for the solenoid valve 16. And a pilot pump 17 capable of supplying pressure.

  In addition to the on / off signal generator 7a equivalent to that in the first embodiment, the controller 7 corresponds to a discharge pressure corresponding to a value corresponding to the remaining amount of urea water in the urea water tank 10. A function generator 7h that outputs the signal S5 and a function generator 7i that outputs a current corresponding to the signal S5 output from the function generator 7h to the electromagnetic valve 16 as a drive signal are provided.

  As the remaining amount of urea water detected by the remaining amount detecting means 11 is reduced from a predetermined amount by the function generating units 7h and 7i, the electromagnetic valve 16, and the pilot pump 17, the hydraulic pump 2 is driven. A discharge pressure control means for performing control to reduce a state quantity to be performed, for example, a discharge pressure of the pressure oil discharged from the hydraulic pump 2 to a predetermined value within a range in which the hydraulic actuator included in the hydraulic drive circuit 8 can be operated; That is, state quantity control means is configured.

  The function generator 7h outputs a signal S5 corresponding to the preset maximum discharge pressure P during normal operation of the hydraulic pump 2 until the remaining amount of urea water in the urea water tank 10 reaches the first predetermined amount A. When the remaining amount is equal to or less than the first predetermined amount A, a signal S5 that is gradually decreased according to the decrease in the remaining amount of the urea water tank 10 is output, and the remaining amount of the urea water tank 10 is the first. When it decreases to the second predetermined amount B or less, which is smaller than one predetermined amount A, for example, a functional relationship is output that outputs a signal corresponding to the limited discharge pressure Ps that is 70% of the maximum discharge pressure P during normal work.

  Note that the second predetermined amount B that gives the above-described limit discharge pressure Ps is a predetermined value within a range in which the hydraulic actuator included in the hydraulic drive circuit 8 can be operated.

  The function generator 7i outputs, as a drive signal, a current ranging from the maximum current SM to the limit current Sm smaller than the maximum current SM according to the value of the signal 5 output from the function generator 7h, that is, the discharge pressure. To do.

  Other configurations are the same as those of the first embodiment described above.

  In the third embodiment configured as described above, sufficient urea water is supplied until the remaining amount of urea water in the urea water tank 10 reaches the first predetermined amount A, as in the first embodiment. As a result, nitrogen oxides in the exhaust gas are purified, and clean exhaust gas can be discharged. Further, the alarm lamp 12 is kept off. Further, a signal S5 corresponding to the maximum discharge pressure P during normal operation is output from the function generator 7h of the controller 7, and a drive signal corresponding to the maximum current SM is output from the function generator 7i in response to this signal S5. 6 is output. Thereby, the set pressure of the main relief valve 5 is maintained at a high set pressure during normal operation.

  From this state, when the urea water in the urea water tank 10 decreases and the remaining amount of urea water detected by the remaining amount detecting means 11 reaches the first predetermined amount A, the alarm lamp 12 is turned on. Furthermore, as the remaining amount of urea water decreases from the first predetermined amount A, the alarm lamp 12 is kept on, and the signal S5 output from the function generator 7h is a value that is gradually lower than the maximum discharge pressure P. In response to this low value, a drive signal corresponding to a current smaller than the maximum current SM is output from the function generator 7 i to the solenoid valve 16. As a result, the solenoid valve 16 is activated, and the pilot pressure of the pilot pump 17 is applied to the control unit of the main relief valve 5 via the solenoid valve 16, and the main relief valve 5 sets the set pressure higher than the maximum discharge pressure P. It is controlled to gradually lower.

  Further, when the urea water in the urea water tank 10 decreases to become the second predetermined amount B or less, the alarm lamp 12 is kept on and the signal S5 output from the function generator 7h is set to the limit discharge pressure Ps. The drive signal corresponding to the limit current Sm corresponding to this value is output from the function generator 7 i to the solenoid valve 16. Accordingly, the set pressure of the main relief valve 5 becomes the limit discharge pressure Ps by the pilot pressure supplied via the electromagnetic valve 16.

  In this state, when the hydraulic actuator included in the hydraulic drive circuit 8 is operated, the maximum force cannot be generated, and for example, a hard ground excavation that is possible during normal work cannot be performed, and workability is reduced. To do.

  Even when the remaining amount of the urea water in the urea water 10 is equal to or less than the second predetermined amount B as described above, the load is reduced along with the reduction of the maximum discharge pressure of the pressure oil discharged from the hydraulic pump 2. The purification of the exhaust gas of the engine 1 in which is reduced is continued, and the clean exhaust gas can be discharged.

  The present embodiment configured as described above can also purify the exhaust gas discharged from the engine 1 as in the first embodiment described above.

  When the remaining amount of urea water detected by the remaining amount detecting means 11 is equal to or less than the first predetermined amount A, the alarm lamp 12 is turned on as in the first embodiment.

  Further, when the remaining amount of the urea water detected by the remaining amount detecting means 11 becomes the first predetermined amount A or less, the discharge pressure of the hydraulic pump 2 gradually becomes lower than the maximum discharge pressure P and becomes the second predetermined amount B or less. Then, the pressure is reduced to the limit discharge pressure Ps which is 70% of the maximum discharge pressure P. In this way, even if the remaining amount of urea water is equal to or less than the second predetermined amount B, it is possible to continue the purification of the exhaust gas of the engine 1 with a reduced load.

  Since the alarm lamp 12 is turned on as described above, and the workability is lowered at the same time, even in the third embodiment, replenishment of urea water is urged and within a limited range. It is possible to continue the operation by supplying pressure oil to the hydraulic actuator without causing an engine stall.

1 is a hydraulic circuit diagram showing a first embodiment of an exhaust gas purifying apparatus for a construction machine according to the present invention. It is a block diagram which shows the principal part structure of the controller with which 1st Embodiment shown in FIG. 1 is equipped. It is a figure which shows the characteristic acquired by 1st Embodiment of this invention. It is a block diagram which shows the principal part structure of the controller with which 2nd Embodiment of this invention is equipped. It is a figure which shows the characteristic acquired by 2nd Embodiment of this invention. It is a hydraulic circuit diagram which shows 3rd Embodiment of this invention. It is a block diagram which shows the principal part structure of the controller with which 3rd Embodiment of this invention is equipped.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 2 Variable displacement hydraulic pump 3 Rotation speed indicating device 4 Regulator 5 Main relief valve 6 Rotation control means 7 Controller 7a On / off signal generation section 7b Pump absorption torque calculation section 7c Function generation section (pump absorption torque control means) [State Quantity control means]
7d Minimum value selection unit (pump absorption torque control means) [state quantity control means]
7e Pump discharge amount calculation unit 7f Function generation unit (flow rate control means) [state quantity control means]
7g Minimum value selector (flow rate control means) [state quantity control means]
7h Function generator (discharge pressure control means) [state quantity control means]
7i Function generator (discharge pressure control means) [state quantity control means]
8 Hydraulic drive circuit 9 Exhaust gas control means 10 Urea water tank (reducing agent solution tank)
11 Remaining amount detection means 12 Alarm lamp (warning notification means)
13 Characteristic Line 14 Characteristic Line 15 Characteristic Line 16 Solenoid Valve (Discharge Pressure Control Unit) [State Quantity Control Unit]
17 Pilot pump (discharge pressure control means) [state quantity control means]

Claims (6)

An engine, a variable displacement hydraulic pump that is driven by the engine and whose absorption torque is controlled so as not to exceed an output torque of the engine, a regulator that controls a tilt angle of the variable displacement hydraulic pump, and the variable displacement hydraulic pressure Pressure oil discharged from the pump is supplied, and is provided in a construction machine having a hydraulic drive circuit including a plurality of hydraulic actuators,
Exhaust gas control means for performing a treatment to purify nitrogen oxides in the exhaust gas discharged from the engine;
A reducing agent solution tank for storing a reducing agent solution supplied to the exhaust gas control means;
With a remaining amount detecting means for detecting the remaining amount of the reducing agent solution stored in the reducing agent solution tank,
Warning notifying means for notifying that a replenishment of the reducing agent solution is required when the remaining amount of the reducing agent solution detected by the remaining amount detecting means has decreased to a first predetermined amount;
A state relating to driving of the variable displacement hydraulic pump while the remaining amount of the reducing agent solution detected by the remaining amount detecting means is decreased from the first predetermined amount to a second predetermined amount smaller than the first predetermined amount. amounts, have gradually row control to decrease to a predetermined value within a range the operation of the hydraulic actuator is possible, than the remaining amount is the second predetermined amount of the reducing agent solution to be detected by the level detecting means A state amount control means for maintaining the state amount at the predetermined value within a range in which the hydraulic actuator can be operated ,
The variable displacement hydraulic pump has a state angle related to driving of the variable displacement hydraulic pump controlled by the state amount control means, the tilt angle of the variable displacement hydraulic pump is controlled by the regulator, and absorption torque is reduced by the engine. An exhaust gas purifying apparatus for a construction machine , wherein the torque is controlled so as not to exceed an output torque . In the invention of claim 1,
The state quantity is pump absorption torque, and the state quantity control means comprises pump absorption torque control means ,
The variable displacement hydraulic pump has a torque so that the absorption torque does not exceed the output torque of the engine while the tilt angle is controlled by the regulator according to the pump absorption torque controlled by the pump absorption torque control means. An exhaust gas purification device for construction machinery, which is controlled . In the invention of claim 1,
The state quantity is a flow rate discharged from the variable displacement hydraulic pump, and the state quantity control means comprises a flow rate control means ,
The variable displacement hydraulic pump is torque controlled so that the absorption torque does not exceed the output torque of the engine while the tilt angle is controlled by the regulator according to the flow rate controlled by the flow rate control means. An exhaust gas purification device for construction machinery. In the invention of claim 1,
The exhaust gas purifying apparatus for a construction machine, wherein the state quantity is a discharge pressure of the variable displacement hydraulic pump, and the state quantity control means comprises a discharge pressure control means. In the invention according to any one of claims 1 to 4,
An exhaust gas purifying apparatus for construction machinery, wherein the reducing agent solution comprises urea water. In the invention according to any one of claims 1 to 4,
An exhaust gas purification apparatus for construction machinery, wherein the warning notification means comprises an alarm lamp.

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