JP6160090B2 - Construction machinery - Google Patents

Description

  The present invention relates to a construction machine such as a hydraulic excavator that performs horsepower control (so-called PQ control) using a variable displacement hydraulic pump and includes an air conditioner.

  The background art will be described using a hydraulic excavator as an example.

  As shown in FIG. 4, the excavator is mounted on a crawler type lower traveling body 1 so that an upper swing body 2 can swing around an axis X perpendicular to the ground. 3, a front attachment 9 having an arm 4, a bucket 5, and booms, arms, and bucket cylinders 6, 7, and 8 to be driven is attached. 2 a is a cabin as a cockpit provided in the upper swing body 2.

  A dozer 10 is attached to the lower traveling body 1. The dozer 10 is driven up and down by a dozer cylinder (not shown), and performs a leveling work for flattening the ground while traveling in a grounded state, a soil carrying work for pushing and carrying soil, and the like.

  FIG. 5 shows the configuration of a hydraulic excavator drive system and a conventional pump control system.

  The hydraulic pump includes first and second main pumps 11 and 12, a dozer pump 13 serving as a hydraulic source for the dozer cylinder, and a pilot pump 14 serving as a pilot hydraulic source, and these pumps 11 to 14 have a common power source. It is driven by the engine 15 as.

  The main pumps 11 and 12 are variable displacement hydraulic pumps whose tilt (pump discharge flow rate) is controlled by a tilt control device.

  On the other hand, the dozer pump 13 is a separate pump from the main pumps 11 and 12 for the purpose of ensuring the independence of the dozer operation, and a fixed displacement hydraulic pump such as an inexpensive gear pump is used.

  The tilt control device includes a spring 16 and a regulator 18 that introduces the pump pressure of both the main and dozer pumps 11 to 13 as a force (control pressure) that opposes the spring force by the pump pressure introduction pipes 17. The tilt of the pump is controlled by the control pressure (pump pressure) and the spring force.

  That is, horsepower control (so-called PQ control) is performed in which the pump flow rate Q decreases as the total pump pressure PpT increases as shown in FIG. Is called.

  In this case, in a hydraulic excavator equipped with a dozer, the load torque increases during the dozer operation in which both running and dozer operations are performed, and there is a danger of engine stall. The structure which performs the horsepower reduction control of the pumps 11 and 12 is taken.

  The pressure oil from both the main pumps 11 and 12 and the dozer pump 13 is supplied to each of the hydraulic actuators (represented by “20”) through the control valve 19.

  On the other hand, in the hydraulic excavator provided with the cabin 2a as shown in the figure, an air conditioner for the cabin (hereinafter referred to as an air conditioner) is provided, and the compressor 21 of this air conditioner serves as a power source common to the respective hydraulic pumps 11-14. It is driven by the engine 15.

  The compressor 21 is connected to a power source 23 via an air conditioner switch 22 provided in the cabin 2a, and operates when the air conditioner switch 22 is turned on.

  That is, an air conditioning circuit 24 is configured by the compressor 21 and the air conditioner switch 22.

  Here, since the sum of the torque of the compressor 21 (hereinafter referred to as air conditioner torque) and the pump torque is the total load torque (full load torque), the PQ control of the variable displacement pump is performed in consideration of the air conditioner torque. There is a need.

  In this case, conventionally, a configuration is adopted in which horsepower control is performed so that the full load torque including the air conditioner torque does not exceed the engine torque when the air conditioner is operated.

  Specifically, a pilot pressure introduction line 25 for introducing a pilot pump pressure as a control pressure into the regulator 18 is provided, and an electromagnetic switching valve 26 is provided in the pilot pressure introduction line 25 so that the pilot pressure can be reduced when the air conditioner is operated. By introducing it into the regulator 18 via the switching valve 26, a configuration is adopted in which the flow rate setting for PQ control is lowered to the low flow rate side. In FIG. 5, T is a tank.

  Further, in the known technique disclosed in Patent Document 1, as a means for achieving the same purpose, the pump pressure of both main pumps is detected and PQ control is performed by a controller and an electromagnetic proportional valve, and the air conditioner is operated. Sometimes, the configuration is such that the torque setting for PQ control is lower than when the air conditioner is stopped.

Japanese Patent Laid-Open No. 08-303403

  In the known techniques including the prior art shown in FIG. 5, on the assumption that the air conditioner operation is maintained as described above, the horsepower control is performed so that the full load torque including the air conditioner torque does not exceed the engine torque. Sometimes, the maximum pump torque is always reduced by the air conditioner torque. For this reason, workability | operativity falls.

  Further, since control is performed to prevent engine stall by changing the torque setting between when the air conditioner is operating and when it is stopped, the equipment for changing the torque setting (the electromagnetic switching valve 26 in the prior art shown in FIG. In the known technique, an electromagnetic proportional valve) is required, which increases the cost.

  Therefore, the present invention is equipped with an air conditioner, and on the premise that horsepower control is performed, it is possible to reliably prevent engine stall while improving workability, and to simplify the necessary equipment and realize cost reduction. Provide machines.

  As means for solving the above problems, in the present invention, a plurality of hydraulic pumps including a variable capacity main pump and a compressor of an air conditioner are driven by an engine as a common power source, and the horsepower of the main pump A tilt control device that performs control, and an air conditioning circuit that activates / stops the compressor based on an on / off operation of an air conditioning switch. The tilt control device includes a pump pressure and a spring force that are introduced as control pressures. In the construction machine configured to control the pump flow rate by changing the tilt of the main pump based on a preset PQ characteristic, the air conditioning circuit is independent of the on / off operation of the air conditioning switch. Open / close means for connecting / disconnecting to / from the power source is provided, and this open / close means is energized by the load torque of the hydraulic pump and the compressor. The air-conditioning circuit and the cut-off state to when a state exceeding the Ntoruku as timing conditioning blocked, when the load torque is smaller than the engine torque is obtained by adapted to the connected state to the air conditioning circuit.

  According to this configuration, when the full load torque including the compressor exceeds the engine torque, the air conditioning circuit is shut off (stops if the air conditioner is operating, and maintains the stopped state if it is stopped. ) To reduce the total load torque, the engine torque can be used with priority given to the pump, and workability can be improved.

  Further, since the horsepower control is performed based only on the pump pressure, there is no need for an extra control such as changing the torque setting between when the air conditioner is activated and when it is stopped, as in the known art. For this reason, a solenoid valve for changing the torque setting is not necessary, and cost reduction can be realized.

  In addition, a high-load operation in which the total load torque exceeds the engine torque is not continuously performed in practice, so that there is little influence even if the air conditioner is stopped.

In the present invention, furthermore, the closing means is constituted when the pressure of one hydraulic pump of the plurality of hydraulic pump exceeds a set value so that the cut-off state of the air conditioning circuit as timing interrupting the air conditioner.

  Even in one of the multiple hydraulic pumps, if the pressure exceeds the set value, the possibility that the full load torque will exceed the engine torque increases, so by shutting off the air conditioning circuit based on one pump pressure, , Can prevent the engine stall.

  Moreover, since only the pressure of one hydraulic pump needs to be monitored, the configuration is simple.

In this case, in a construction machine having a fixed displacement hydraulic pump in addition to the main pump, the opening / closing means uses the time when the pressure of the fixed displacement hydraulic pump exceeds a set value as the air conditioning cutoff time. It is not to wishing configured to cut-off state of the air conditioning circuit.

  In a construction machine equipped with a fixed displacement hydraulic pump, the possibility of engine stall becomes particularly high when the load of the pump is high, so engine stall is prevented by shutting off the air conditioning circuit based on the pressure of the pump. Increases effectiveness.

In particular, since the dozer work is a combined work of running and dozer operation, a large torque is consumed. In other words, the pump pressure of the dozer pump is an indicator of the occurrence of engine stall. Thus, by blocking the air conditioning circuit on the basis of the de Zaponpu pressure, leaving it is possible to reliably prevent the engine stall.

Further, a pressure switch that operates when the pressure of the Dozaponpu exceeds the set value, have to have desired to constitute the switching means by switch open during on operation of the pressure switch provided in the air conditioning circuit.

In this case, the opening / closing means sets a value for shutting off the air conditioning circuit to a set value for the pressure of the hydraulic pump higher than a value for placing the air conditioning circuit in a disconnected state, and provides hysteresis for shutting off / connecting the air conditioning circuit. it was desired to configured to have the.

  In this way, it is possible to prevent wasteful switching of the air conditioning circuit shut-off / connection with respect to pressure fluctuations due to pump pulsation or the like, and to realize control stability.

The above closing means, when the total load torque obtained from the pressure of all the hydraulic pump is a state above the engine torque be configured to cut-off state of the air conditioning circuit as timing interrupting the air-conditioning Yes.

  According to this configuration, since the air conditioning circuit is shut off based on the total load torque of all the pumps, the air conditioning operation can be stopped only in a load situation in which the engine stalls truly, and the air conditioner may be stopped unnecessarily. Absent.

In the present invention, the air conditioner includes a blower fan of the electric, the air blowing fan not to have desired to connect to a power source in the air conditioning circuit and the parallel state.

  According to this configuration, even if the air-conditioning circuit is shut off during the air-conditioner operation, the air-blowing fan continues the air-blowing action, so that the air-conditioning function is not extremely reduced, and the operator feels uncomfortable and uncomfortable. Can do.

  According to the present invention, engine stall can be reliably prevented while improving workability, and necessary equipment can be simplified to reduce costs.

1 is a circuit diagram showing a first embodiment which is an embodiment of the present invention. FIG. It is a figure which shows the hysteresis characteristic of the pressure switch in the embodiment. It is a circuit diagram which shows 2nd Embodiment different from embodiment of this invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic side view of a hydraulic excavator that is one of application targets of the present invention. It is a conventional circuit diagram. It is a figure which shows the relationship between the pump pressure and pump flow volume by horsepower control.

  The embodiment is applied to a hydraulic excavator.

In the first embodiment which is an embodiment of the present invention shown in FIGS. 1 and 2 and the second embodiment which is a reference embodiment shown in FIG. 3, the following points are the same as those in the prior art shown in FIG.

  (A) As a hydraulic pump, the first and second main pumps 11 and 12, a dozer pump 13 serving as a hydraulic source for the dozer cylinder, and a pilot pump 14 serving as a pilot hydraulic source are provided, and these pumps 11 to 14 are common. It is driven by the engine 15 as a power source.

  (B) The main pumps 11 and 12 are variable displacement hydraulic pumps whose tilt (pump discharge flow rate) is controlled by a tilt control device, while the dozer pump 13 is different from the main pumps 11 and 12. It is a separate pump and a fixed displacement hydraulic pump such as an inexpensive gear pump is used.

  (C) The tilt control device includes a spring 18 and a regulator 18 that introduces the pump pressures of the main and dozer pumps 11 to 13 as a force (control pressure) that opposes the spring force by the pump pressure introduction pipes 17. And the tilt of the pump is controlled by the control pressure (pump pressure) and the spring force. In other words, horsepower control (so-called PQ control) is performed in which the pump flow rate decreases as the total pump pressure increases so that the engine pump torque does not exceed the engine torque.

  It is not necessary to provide the pilot pressure introduction conduit 25 and the electromagnetic switching valve 26 in FIG.

  (D) The pressure oil from both the main pumps 11 and 12 and the dozer pump 13 is supplied to each of the hydraulic actuators (represented by the representative symbol “20”) via the control valve 19.

  (E) In the hydraulic excavator with the cabin 2a as shown in FIG. 4, an air conditioner (hereinafter referred to as an air conditioner) for the cabin 2a is provided, and the compressor 21 of this air conditioner has a common power with each of the hydraulic pumps 11-14. A point driven by the engine 15 as a source.

  (F) The compressor 21 is connected to a power source 23 via an air conditioner switch 22 provided in the cabin, and operates when the air conditioner switch 22 is turned on. That is, an air conditioning circuit 24 is configured by the compressor 21 and the air conditioner switch 22.

First embodiment (see FIGS. 1 and 2)
In the first embodiment, when the normally closed contact 28 of the relay 27 serving as a switch is connected in series with the air conditioner switch 22 of the air conditioning circuit 24 and the solenoid 29 of the relay 27 is excited and the normally closed contact 28 is opened. In addition, the air conditioning circuit 24 is configured to be cut off from the power source 23.

  Further, a pressure switch 30 is provided in the discharge pipe of the dozer pump 13, and a series circuit of the pressure switch 30 and a solenoid 29 of the relay 27 is connected to the power supply 23.

  Further, the air conditioner includes an electric blower fan 31, and this blower fan 31 is connected to the power supply 23 in parallel with the air conditioning circuit 24.

  The pressure switch 30 is turned off when the pressure of the dozer pump 13 is less than a predetermined set value, and turned on when the pressure exceeds the set value.

  When the pressure switch 30 is turned on, the relay 27 is activated and the air conditioning circuit 24 is shut off from the power source 23, that is, the air conditioner operation is stopped (if stopped, it is maintained in the stopped state). Has been.

  Here, the sum of the dozer pump torque Td required for the dozer pump 13, the main pump torque Tm required for the main pumps 11 and 12, and the air conditioner torque Ta required for the operation of the air conditioner (compressor 21) is the total load torque T0. Become.

  In this case, the dozer operation is a combined operation of travel and dozer, and the required torque is the sum of the dozer pump torque Td and the torque Tm of one main pump used for the travel motor of the main pumps 11 and 12. is there.

  Since the average main pump torque Tm used for traveling during the dozer operation is determined, whether or not the full load torque T0 exceeds the engine torque Te depends on the dozer pump torque Td.

there,
Te> Td + Tm
The set value of the pressure switch 30 is determined so that

  Thus, when the total load torque T0 including the compressor 21 exceeds the engine torque Te, the air conditioning circuit 24 is shut off regardless of the air conditioner switch 22 and the total load torque T0 is lowered regardless of the air conditioner switch 22. When the torque T0 is smaller than the engine torque Te, the air conditioning circuit 24 is configured to be connected.

  As a result, the engine torque can be used with priority to the pump while preventing the engine stall, thereby improving workability.

  Further, since the horsepower control is performed based only on the pressures (pump pressures) of the main pumps 11 and 12 and the dozer pump 13, extra control such as changing the torque setting between when the air conditioner is operating and when it is stopped as in the known art. It becomes unnecessary. For this reason, a solenoid valve for changing the torque setting is not necessary, and cost reduction can be realized.

  In addition, since the high load operation in which the total load torque T0 exceeds the engine torque Te is not continuously performed in practice, there is little influence even if the air conditioner is stopped.

  Even if the air conditioning circuit 24 is shut off during the operation of the air conditioner, since the air blowing action by the blower fan 31 is continued, there is no possibility that the air conditioning function will be extremely lowered, and the operator's discomfort and discomfort can be reduced. .

  On the other hand, as shown in FIG. 2, the set value Pd1 for turning on the switch 30 (blocking the air conditioning circuit 24) is set higher than the set value Pd2 for turning off. . In FIG. 2, Pr is the relief pressure of the dozer pump 13.

  In other words, it is configured such that it is turned on at a relatively high pressure and turned off at a low pressure, that is, the air-conditioning circuit 24 is provided with hysteresis in the cutoff / connection.

  In this way, it is possible to prevent unnecessary switching of the shutoff / connection of the air conditioning circuit 24 against pressure fluctuations due to pulsation of the dozer pump 13 and the like, and to realize control stability.

Second embodiment (see FIG. 3)
Only differences from the first embodiment will be described.

  In the first embodiment, the air conditioning circuit 24 is shut off when the full load torque T0 exceeds the engine torque Te based on the pressure of the dozer pump 13 while the air conditioning circuit 24 is shut off. In the second embodiment, the pump pressures of all the pumps 11 to 13 except for the pilot pump 14 are detected to obtain the actual full load torque T0, and when this exceeds the engine torque Te, the air conditioning circuit is defined as the air conditioning cutoff time. 24 is cut off.

  That is, pressure sensors 32, 33, and 34 for detecting the pressures of the main pumps 11 and 12 and the dozer pump 13 and a controller 35 for calculating a torque based on all the detected pump pressures are provided. A configuration for controlling the shutoff / connection of the circuit 24 is employed.

  In other words, the pressure sensors 32 to 34, the controller 35, and the relay 27 constitute opening / closing means for connecting / blocking the air conditioning circuit 24.

  The controller 35 performs the following processing.

  (i) The total pump torque is determined from the total pump pressure, and the air conditioner torque Ta is added to the total pump torque to determine the total load torque T0.

  (ii) Comparing the full load torque T0 and the engine torque Te, the process of shutting off the air conditioning circuit 24 when T0> Te, that is, the solenoid 29 of the relay 27 is excited, and the air conditioning circuit 24 is activated when T0 <Te. The connection process, that is, the excitation of the solenoid 29 is stopped.

  As a result, the same effects as those of the first embodiment can be obtained, such as improving the workability by using the engine torque with priority to the pump while preventing the engine stall.

  Further, according to the second embodiment, since the air conditioning circuit is shut off based on the total load torque of all the pumps, the air conditioning operation can be stopped only in a load situation where the engine stalls truly, and the air conditioner is stopped unnecessarily. There is no fear of it.

Other embodiments
(1) As a modification of the first embodiment, a configuration may be adopted in which the dozer pump pressure is detected by a pressure sensor, and the relay 27 is controlled by a controller as in the second embodiment.

  (2) Configuration for detecting the pump pressure of one or both of the main pumps 11 and 12, or the main pump pressure and the dozer pump pressure instead of the dozer pump 13, and controlling the relay 27 based on the total pump pressure You may take

DESCRIPTION OF SYMBOLS 1 Lower traveling body 2 Upper turning body 2a Cabin provided with air conditioner 10 Dozer 11, 12 Main pump 13 Dozer pump 15 Engine 16 Spring constituting tilt control device 17 Same as above, Pump pressure introduction pipe 18 Same as above, Regulator 21 Air conditioning Compressor of apparatus 22 Air conditioner switch 23 Power source 24 Air conditioner circuit 27 Relay as switch 28 Normally closed contact of relay 29 Solenoid 30 Pressure switch 31 Blower fan 32 to 34 Pressure sensor constituting open / close means 35 Controller

Claims (6)

A plurality of hydraulic pumps including a variable capacity main pump, a compressor of the air conditioner is driven by an engine as a common power source, and a tilt control device for controlling the horsepower of the main pump, and an air conditioner switch on An air conditioning circuit that activates / deactivates the compressor based on a turn-off operation, and the tilt control device uses the pump pressure and the spring force introduced as the control pressure, based on a preset PQ characteristic. In a construction machine configured to control the pump flow rate by changing the tilt of the main pump, there is provided an opening / closing means for connecting / blocking the air conditioning circuit to / from the power source regardless of the on / off operation of the air conditioning switch. The opening / closing means detects when the load torque by the hydraulic pump and the compressor exceeds the engine torque. And a blocking state the air-conditioning circuit, when the load torque is smaller than the engine torque is configured to be a connected state of the air conditioning circuit, said closing means, one of the hydraulic pump of the plurality of hydraulic pumps A construction machine configured so that the air conditioning circuit is shut off when the pressure exceeds a set value as the air conditioning cutoff time . In addition to the main pump, a fixed displacement hydraulic pump is provided, and the opening and closing means shuts off the air conditioning circuit when the pressure of the fixed displacement hydraulic pump exceeds a set value as the air conditioning cutoff timing. The construction machine according to claim 1 , wherein the construction machine is configured as described above. A lower traveling body, a dozer attached to the lower traveling body, a dozer cylinder for raising and lowering the dozer, and a fixed displacement type dozer pump as a hydraulic source of the dozer cylinder, and the opening / closing means includes the dozer pump The construction machine according to claim 2, wherein the air-conditioning circuit is shut off when the pressure exceeds a set value as the air-conditioning shut-off time. Claim, characterized in that constitute the opening and closing means and the pressure switch that operates by switch open during on operation of the pressure switch provided in the air conditioning circuit when the pressure of the Dozaponpu exceeds the set value 3 The construction machine described. The opening / closing means sets a value for shutting off the air conditioning circuit to a set value for the pressure of the hydraulic pump higher than a value for setting the connected state so that the air conditioning circuit is shut off / connected. The construction machine according to any one of claims 1 to 4 , wherein the construction machine is configured as follows. The construction machine according to any one of claims 1 to 5 , wherein the air conditioner includes an electric blower fan, and the blower fan is connected to a power source in parallel with the air conditioner circuit.

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