JP5872274B2 - Work vehicle - Google Patents

Description

  The present invention relates to a technique for avoiding engine stall of a work vehicle.

As the work vehicle, for example, a turning work vehicle that performs excavation work of earth and sand is known. The work vehicle includes an engine and a hydraulic drive system. The hydraulic drive system is a force transmission system using hydraulic oil. The hydraulic drive system includes a hydraulic pump and a hydraulic actuator. The hydraulic pump applies pressure to the hydraulic oil and sends the hydraulic oil to the hydraulic actuator.

  The work vehicle performs necessary work by rotating a hydraulic pump (variable displacement type or fixed displacement type) by an engine and driving a hydraulic actuator by pressure oil discharged from the hydraulic pump. In the engine, the fuel injection amount is controlled according to the target rotational speed set by an accelerator lever or the like, and the actual rotational speed is controlled.

  Patent Document 1 discloses speed sensing control for avoiding engine stall. In the speed sensing control, a difference (rotational speed deviation) between the target rotational speed of the engine and the actual rotational speed is obtained, and the input torque of the hydraulic pump is controlled using the rotational speed deviation. In other words, the speed sensing control is a method that reduces the load torque of the hydraulic pump, avoids engine stall, and effectively uses the engine output when the detected actual rotational speed decreases with respect to the target rotational speed. is there.

  However, even if speed sensing control is executed, the actual rotational speed detected with respect to the target rotational speed may further decrease. Even in such a case, it is necessary to somehow avoid engine stall and effectively use the engine output. In the field of work vehicles, in addition to speed sensing control, in order to avoid engine stall from another aspect, it is a problem to reduce the engine load.

Japanese Examined Patent Publication No. 62-8618

  The subject of this invention is providing the work vehicle which can avoid an engine stall.

  The problem to be solved by the present invention is as described above. Next, means for solving the problem will be described.

In Claim 1, the engine, the target rotation speed setting means for setting the target rotation speed of the engine, the actual rotation speed detection means for detecting the actual rotation speed of the engine, and at least one driven by the engine A hydraulic pump, a hydraulic drive system including the hydraulic pump, a compressor driven by the engine, an air conditioning system including the compressor, and a control means for controlling the engine, the hydraulic drive system and the air conditioning system; And the control means reduces the load torque of the hydraulic pump having a variable discharge amount when the actual rotational speed decreases with respect to the target rotational speed , and further reduces the actual rotational speed with respect to the target rotational speed. When the pressure drops, the engine is disconnected from the compressor.

  According to the work vehicle of the present invention, engine stall can be avoided.

The side view which shows the whole structure of the turning working vehicle which concerns on 1st Embodiment of this invention. The block diagram which similarly shows the surrounding structure of an engine. The flowchart which similarly shows the flow of engine stall avoidance control. The schematic diagram which similarly shows the structure of a stepped control pin.

  A turning work vehicle 100 will be described with reference to FIG. The turning work vehicle 100 is an embodiment of the turning work vehicle of the present invention. The turning work vehicle 100 includes a traveling device 120, a turning device 130, and a working device 140.

  The traveling device 120 includes a pair of left and right crawlers 125, 125, a left traveling hydraulic motor 125L, and a right traveling hydraulic motor 125R. The traveling device 120 drives the turning work vehicle 100 forward and backward by driving the left crawler 125 by the left traveling hydraulic motor 125L and the right crawler 125 by the right traveling hydraulic motor 125R. It is.

  The traveling device 120 includes a blade 170 that is used when performing leveling work accompanying excavation work. The blade 170 is supported on the front and rear sides of the traveling device 120 so as to be pivotable in the vertical direction, and is lifted and lowered by a blade cylinder 175 that is extended and retracted.

  The swivel device 130 includes a swivel base 131, a swivel motor 132, a control unit 133, the engine 10, and the air conditioning system 20. The swivel 131 is disposed above the traveling device 120 and is supported by the traveling device 120 so as to be able to swivel. The turning device 130 drives the turning motor 132 to turn the turntable 131 with respect to the traveling device 120. On the swivel base 131, a control unit 133 including various operating tools, an engine 10 serving as a power source, an air conditioning system 20 that performs air conditioning of the control unit 133, and the like are arranged.

  The working device 140 includes a boom 141, an arm 142, a bucket 143, a boom cylinder 146, an arm cylinder 147, a bucket cylinder 148, and a swing cylinder 149.

  One end of the boom 141 is supported by a front portion of the swivel base 131 so as to be rotatable in the front-rear direction, and is rotated by a boom cylinder 146 that is extended and retracted. Further, one end of the boom 141 is supported so as to be rotatable in the left-right direction via the boom bracket, and the boom bracket is rotated by a swing cylinder 149 that is driven to extend and retract. One end of the arm 142 is pivotally supported by the other end of the boom 141 and is rotated by an arm cylinder 147 that is extended and retracted. One end of the bucket 143 is supported by the other end of the arm 142 and is rotated by a bucket cylinder 148 that is driven to extend and contract.

  The surrounding configuration of the engine 10 will be described with reference to FIG. In FIG. 2, in the hydraulic drive system 30, a thick line indicates a main circuit, and a thin line indicates a pilot circuit. Moreover, in FIG. 2, in the air conditioning system 20, the thick line has shown the refrigerant circuit. Furthermore, in FIG. 2, the dotted line has shown the electric signal line.

  Around the engine 10, there are a first pump 31 as a hydraulic pump, a second pump 32 as a hydraulic pump, a third pump 33 as a hydraulic pump, a compressor 21, and a controller 50 as control means. A rack actuator 53 as a rotation speed changing means and an accelerator lever 55 as a target rotation speed setting means are provided.

  The configuration of the engine 10 will be described. The output shaft of the engine 10 is connected to the input shaft of the first pump 31, the input shaft of the second pump 32, and the input shaft of the third pump 33 (in this embodiment, the input shaft of the first pump 31, The input shaft of the second pump 32 and the input shaft of the third pump 33 are constituted by the same shaft, which is the input shaft 201 described later in FIG. 4), the first pump 31, the second pump 32, and the third pump 33. The engine 10 is driven, and the output shaft of the engine 10 is connected to the input shaft of the compressor 21 via the clutch 52 and driven.

  In the vicinity of the crankshaft of the engine 10, an engine speed sensor 51 as an actual speed detection means is disposed. The engine speed sensor 51 detects the actual speed Ne of the engine 10. The engine speed sensor 51 is connected to the controller 50.

  The engine 10 is controlled by the electronic governor so as to reach the target rotational speed set by the accelerator lever 55. More specifically, the fuel injection amount is changed and controlled by the operation of the rack actuator 53 serving as the rotation speed changing means so that the target rotation speed set by the accelerator lever 55 is obtained. The rack actuator 53 is connected to the controller 50.

  The configuration of the hydraulic pump will be described. The first pump 31, the second pump 32, and the third pump 33 are included in the hydraulic drive system 30. The hydraulic drive system 30 includes, as hydraulic actuators described above, the left traveling hydraulic motor 125L, the right traveling hydraulic motor 125R, the blade cylinder 175, the boom cylinder 146, the arm cylinder 147, the bucket cylinder 148, and the swing. And a cylinder 149. In the hydraulic drive system 30, the hydraulic oil stored in the hydraulic oil tank is sucked and applied with a hydraulic pump, and the hydraulic oil is pumped to the hydraulic actuator.

  The first pump 31 and the second pump 32 are variable displacement pumps that can change the discharge amount of hydraulic oil by changing the inclination angle of the movable swash plate 41 or the movable swash plate 42. The movable swash plate 41 and the movable swash plate 42 are integrally formed. That is, in the first pump 31 and the second pump 32, a plurality of plungers are housed in the same cylinder block so as to be able to reciprocate, one suction port and two discharge ports are formed, and the plunger is one swash plate. The discharge amount is changed at the same time. The third pump 33 is, for example, a fixed displacement type pump configured by a trochoid type or gear type pump with a constant discharge amount.

  The movable swash plate 41 is configured such that the inclination angle is limited (controlled) by the spring mechanism 47, the first damper mechanism 61, and the rotation deviation damper mechanism 65. The spring mechanism 47 biases the movable swash plate 41 so that the discharge amount of the first pump 31 and the second pump 32 becomes the maximum discharge amount, that is, the movable swash plate 41 is inclined at a predetermined inclination angle. Is. The first damper mechanism 61 is movable so as to adjust the discharge amount of the first pump 31 and the second pump 32 according to the discharge amount of the first pump 31, that is, to adjust the inclination angle of the movable swash plate 41. The swash plate 41 is urged.

  The movable swash plate 42 is configured such that the inclination angle is limited by the second damper mechanism 62 and the third damper mechanism 63. The second damper mechanism 62 is movable so as to adjust the discharge amount of the first pump 31 and the second pump 32 according to the discharge amount of the second pump 32, that is, to adjust the inclination angle of the movable swash plate 42. The swash plate 42 is energized. The third damper mechanism 63 is movable so as to adjust the discharge amount of the first pump 31 and the second pump 32 according to the discharge amount of the third pump 33, that is, to adjust the inclination angle of the movable swash plate 42. The swash plate 42 is energized.

  The electromagnetic proportional control valve 69 adjusts the pilot pressure sent to the rotation deviation damper mechanism 65 from a pilot pump (not shown). A solenoid serving as a switching operation unit of the electromagnetic proportional control valve 69 is connected to the controller 50.

  The configuration of the compressor will be described. The compressor 21 is included in the air conditioning system 20. The air conditioning system 20 includes an outdoor heat exchanger (not shown), an expansion valve, and an indoor heat exchanger. The air conditioning system 20 circulates the refrigerant by the compressor 21 and performs air conditioning of the control unit 133.

  A clutch 52 is interposed between the output shaft of the engine 10 and the input shaft of the compressor 21, and the clutch 52 is switched between ON (connected) and OFF (disconnected). The clutch 52 is constituted by an electromagnetic clutch and is connected to the controller 50.

  The accelerator lever 55 is for setting a target rotational speed mNe of the engine 10. The accelerator lever 55 is disposed in the control unit 133. The operation amount (rotation angle) of the accelerator lever 55 is detected by an angle sensor serving as an operation amount detection means, and the angle sensor is connected to the controller 50.

  The controller 50 comprehensively controls the engine 10, the air conditioning system 20, and the hydraulic drive system 30. An engine speed sensor 51, a clutch 52, an accelerator lever 55 (angle sensor), and an electromagnetic proportional control valve 69 are connected to the controller 50.

  The flow of the engine stall avoidance control S100 will be described with reference to FIG. Note that steps S120 to S130 indicate speed sensing control steps.

  In the engine 10, for example, when the load of the hydraulic pump increases, the actual engine speed Ne decreases. However, until the load of the first set value A1, which will be described later, is reduced to a predetermined actual engine speed by the electronic governor. It is done. Further, the engine load A increases, and until the second set value A2 exceeds the first set value A1, the electromagnetic proportional control valve 69 is operated, the inclination of the movable swash plate 42 is changed, and the first pump 31 and the second pump The amount of hydraulic oil discharged from the pump 32 is reduced. Furthermore, if the second set value A2 is exceeded, the engine 10 will stall. Therefore, when the engine load A exceeds the second set value A2, the engine stall avoidance control S100 shuts off the power transmission to the compressor 21 by turning off the clutch 52 for a certain time, and the engine 10 is stalled. It is controlled so as to avoid it.

  In the present embodiment, the engine load is calculated based on the difference between the target rotational speed mNe and the actual rotational speed Ne. However, the detection of the load is not limited to the present embodiment. For example, the difference between the target rack position and the actual rack position for changing the fuel injection amount, the difference between the target angle and the actual angle of the movable swash plate, the hydraulic pressure, etc. You can also ask for it.

  In step S110, the controller 50 calculates a rotational speed deviation dNe obtained by subtracting the actual rotational speed Ne detected by the engine rotational speed sensor 51 from the target rotational speed mNe set by the accelerator lever 55, and further the rotational speed deviation. The engine load A is calculated based on dNe.

  In step S120, when the rotational speed deviation dNe increases and the engine load A is greater than the first set value A1, the controller 50 proceeds to step S130. On the other hand, when the engine load A is equal to or less than the first set value A1, the process proceeds to step S200, and the rotational speed deviation dNe is controlled to approach 0 by governor control.

  In step S130, the controller 50 adjusts the pilot pressure by the electromagnetic proportional control valve 69 to change the inclination of the movable swash plate 42, and decreases the discharge amount of the hydraulic oil from the first pump 31 and the second pump 32, that is, The load torque of the first pump 31 and the second pump 32 is reduced. As mentioned above, step S120-step S130 have shown the step of speed sensing control.

  In step S140, even if the speed sensing control is executed, the controller 50 determines whether or not the rotation speed deviation dNe still increases and the engine load A is greater than the second set value A2. If the engine load is greater than the second set value A2, the process proceeds to step S150.

  In step S150, the controller 50 turns off the clutch 52, and proceeds to step S160. At this time, the connection between the engine 10 and the compressor 21 is disconnected, and the engine load A is reduced.

  In step S160, it is determined whether the set time t1 has elapsed since the clutch 52 was turned off. When the set time t1 has elapsed, the process proceeds to step S170, and the clutch 52 is turned on.

  The effect of the engine stall avoidance control S100 will be described. According to the engine stall avoidance control S100, engine stall can be avoided. That is, even if the speed sensing control is executed, if the rotational speed deviation dNe still increases and the load increases, the connection between the engine 10 and the compressor 21 is disconnected, and the load on the engine 10 is reduced. By reducing the engine output, engine stall can be avoided.

  The left stepped pin 210 and the right stepped pin 220 will be described with reference to FIG. FIG. 4A schematically shows a side view of the pump unit 200 as a partial cross-sectional view. FIG. 4B schematically shows the plane of the pump unit 200 as a partial cross-sectional view. In FIG. 4, the first pump 31 and the second pump 32 are not shown for easy understanding.

  The pump unit 200 is obtained by integrating the first pump 31, the second pump 32, and the third pump 33 into one casing 300.

  The pump unit 200 includes a casing 300, an input shaft 201, plungers of a first pump 31 and a second pump 32 (not shown), a third pump 33, a pin 210 with a left step, a pin 220 with a right step, a spring A mechanism 230 and a swash plate 240 are provided.

  The swash plate 240 corresponds to the movable swash plate 41 and the movable swash plate 42 of FIG. The spring mechanism 230 corresponds to the spring mechanism 47 of FIG.

  The left stepped pin 210 corresponds to the first damper mechanism 61 and the second damper mechanism 62 of FIG. The left stepped pin 210 includes a first diameter portion (small diameter portion) 211 and a second diameter portion (large diameter portion) 212. The first diameter portion 211 is formed on one end side of the left stepped pin 210. The second diameter portion 212 is formed at the other end portion of the left stepped pin 210, and the other end is in contact with the swash plate 240. The second diameter portion 212 is formed with a larger diameter than the first diameter portion 211.

  The casing 300 is formed with a space for housing the left stepped pin 210. The first space 311 is a space that houses the first diameter portion 211 of the pin 210 with the left step. The second space 312 is a space that houses the second diameter portion 212 of the left stepped pin 210. The first oil passage 411 is formed so as to communicate with one end side of the first diameter portion 211. The first oil passage 411 communicates with the discharge pipe of the first pump 31. The second oil passage 412 is formed so as to communicate with one end side of the second diameter portion 212. The second oil passage 412 communicates with the discharge pipe of the second pump 32. The ratio of the pressure receiving area of the first diameter portion 211 and the pressure receiving area of the second diameter portion 212 is proportional to the ratio of the discharge capacity of the first pump 31 and the discharge capacity of the second pump 32.

  With such a configuration, the left stepped pin 210 is urged toward the swash plate 240 in accordance with the discharge amount of the first pump 31 or the discharge amount of the second pump 32. . That is, the inclination angle of the swash plate 240 is changed by the left stepped pin 210.

  The right stepped pin 220 corresponds to the third damper mechanism 63 and the rotation deviation damper mechanism 65 of FIG. The right stepped pin 220 includes a third diameter part (small diameter part) 223 and a fourth diameter part (large diameter part) 224. The third diameter portion 223 is formed on one end side of the right stepped pin 220. The fourth diameter portion 224 is formed at the other end portion of the right stepped pin 220, and the other end is in contact with the swash plate 240. The fourth diameter part 224 is formed with a larger diameter than the third diameter part 223.

  The casing 300 is formed with a space for storing the right-stage pin 220. The third space 323 is a space that houses the third diameter portion 223 of the right-stage pin 220. The fourth space 324 is a space that houses the fourth diameter portion 224 of the right-stage pin 220. The third oil passage 423 is formed so as to communicate with one end side of the third diameter portion 223. The third oil passage 423 communicates with the discharge pipe of the third pump 33. The fourth oil passage 424 is formed so as to communicate with one end side of the fourth diameter portion 224. The fourth oil passage 424 communicates with the pilot piping of the electromagnetic proportional control valve 69.

  With this configuration, the right-stage pin 220 is urged toward the swash plate 240 according to the discharge amount of the third pump 33 or the pilot pressure adjusted by the electromagnetic proportional control valve 69. Will be. That is, the inclination angle of the swash plate 240 is changed by the right stepped pin 220.

DESCRIPTION OF SYMBOLS 10 Engine 20 Air conditioning system 21 Compressor 30 Hydraulic drive system 31 1st pump 32 2nd pump 33 3rd pump 50 Controller 51 Engine speed sensor 52 Clutch 100 Turning work vehicle 200 Pump unit

Claims (1)

Engine,
Target speed setting means for setting the target speed of the engine;
An actual engine speed detecting means for detecting the actual engine speed;
At least one hydraulic pump driven by the engine;
A hydraulic drive system including the hydraulic pump;
A compressor driven by the engine;
An air conditioning system including the compressor;
Control means for controlling the engine, the hydraulic drive system and the air conditioning system;
Comprising
The control means includes
When the actual rotational speed decreases with respect to the target rotational speed, the load torque of the hydraulic pump is decreased,
Further , when the actual rotational speed decreases with respect to the target rotational speed, the engine and the compressor are disconnected.
Work vehicle.

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