JP5856230B2 - Work machine - Google Patents

Description

  The present invention relates to a work machine such as a backhoe.

  Conventionally, a backhoe, which is an example of a work machine, generally includes a hydraulic pump that supplies hydraulic oil to a hydraulic actuator for a working unit such as an arm, and an engine that operates the hydraulic pump. A predetermined work is executed by driving the hydraulic actuator at. Further, the output of the engine is distributed and transmitted not only to the hydraulic pump but also to a traveling unit such as a crawler.

  In this type of backhoe, the engine controller controls the operation of the fuel injection device with an electronic governor based on the output characteristic map, so that the target engine speed according to the operation amount of the throttle lever and the like and the engine load can be handled. Thus, the engine output (engine speed and output torque) is controlled by adjusting the fuel injection amount (see, for example, Patent Document 1).

JP 2004-340152 A

  By the way, in a backhoe in which the output of one engine is used to drive both the traveling unit and the working unit, when the engine is in a low idle state where the number of revolutions is low, low power is required from the viewpoint of energy saving, low noise, and low vibration. Idle speed (idling speed) is kept as low as possible.

  However, in this case, the increase in the output torque of the engine with respect to the sudden increase in the hydraulic load becomes slower than in the case where the engine speed is in the high speed rotation range. For this reason, for example, when loading and unloading a backhoe from a transport truck, if the bucket is pressed against the ground in a low idle state, the load of the hydraulic pump will increase rapidly, but the response of the engine output torque cannot be followed, and the hydraulic pump The engine output torque is insufficient with respect to the load. As a result, there is a problem that black smoke is discharged to cause knocking or engine stall.

  Therefore, the present invention aims to prevent black smoke and engine stall due to an increase in hydraulic load in a low idle state, and to maintain a stable low idle state.

The present invention relates to an engine, a hydraulic power source that is rotationally driven by the engine, a working unit that is driven by hydraulic oil supplied from the hydraulic power source, a fuel injection device that injects fuel into the engine, and an engine speed detection A rotational speed detection means for storing, a storage means for storing in advance a control pattern indicating the relationship between the engine rotational speed and the fuel injection amount, and a control means for controlling the operation of the fuel injection device based on the control pattern In a working machine that is set at a low idle speed that keeps the idling speed of the engine in an idle state as low as possible , the control means is configured to increase the engine speed when the engine load increases during low speed rotation of the engine. When the engine pressure decreases, the control pattern is temporarily corrected so that the maximum fuel injection amount in the low-speed rotation range of the engine increases. Te, wherein a configuration for executing correction injection control for controlling the fuel injection amount on the basis of the corrected control pattern, the value of the measured value is below the low idle speed of the engine rotational speed and the engine speed of If the difference between the target value and the measured value is greater than or equal to a predetermined value, the correction injection control is executed , and the engine load is detected when the correction injection control is executed once or more after the engine is started. The load factor of the engine obtained from the load detection means is not less than a specified value, the load factor of the engine does not change from the value before correction, or the target value of the engine speed does not change from the value before correction. At this time, the execution of the correction injection control is prohibited .

  Further, when the oil pressure change rate of the hydraulic oil from the oil pressure source is equal to or higher than a preset oil pressure rate, temporary correction of the control pattern may be permitted.

  Further, when the corrected injection control is executed once or more after the engine is started, if the load factor of the engine obtained from the load detection means for detecting the load of the engine is a predetermined value or more, the control pattern is temporarily stored. The correction injection control may not be executed without performing a general correction.

  Further, when the corrected injection control is executed one or more times after the engine is started, if the target value of the engine speed does not change from the value before correction, the control pattern is not temporarily corrected. The correction injection control is not executed. Further, when the correction injection control is executed at least once after the engine is started, when the load factor of the engine does not change from the value before correction, the control pattern The correction injection control may not be performed without performing temporary correction.

  According to the present invention, when the engine speed decreases due to an increase in engine load during low-speed rotation of the engine, the engine speed and fuel injection are increased so that the maximum fuel injection amount in the low-speed rotation range of the engine increases. Since the control pattern indicating the relationship with the amount is temporarily corrected, even if the load on the engine increases due to, for example, hydraulic pressure during the low-speed rotation of the engine, the maximum fuel The engine output torque can be increased by temporarily raising the injection amount. Therefore, it is possible to eliminate the decrease in the engine speed due to the torque shortage, prevent the occurrence of black smoke and knocking, and suppress the possibility of engine stall.

  Further, for example, the detection timing of the load increase due to the hydraulic pressure or the like can be grasped based on the hydraulic pressure of the hydraulic oil from the hydraulic power source, so that it is possible to make a determination faster than when the detection timing is measured based on the engine speed. There is an effect that it is possible to shorten the time required for executing the temporary correction of the control pattern.

It is a side view of a backhoe. It is a top view in a cabin. It is a hydraulic system diagram of a backhoe. It is a functional block diagram of a control means. It is explanatory drawing of the output characteristic map which shows the relationship between an engine speed and a rack position. It is a flowchart of the correction | amendment injection control of 1st Example. It is a flowchart of the correction | amendment injection control of 2nd Example. It is a flowchart of the correction | amendment injection control of 3rd Example. It is a flowchart of the correction | amendment injection control of 4th Example.

  DESCRIPTION OF EMBODIMENTS Hereinafter, an embodiment embodying the present invention will be described based on drawings (FIGS. 1 to 9) applied to a backhoe as a work machine.

(1). Outline of Backhoe First, an outline of the backhoe 1 will be described with reference mainly to FIGS. 1 and 2. In FIG. 2, the illustration of the cabin 6 is omitted for convenience of explanation.

  A backhoe 1, which is an example of a work machine, includes a crawler-type traveling device 2 having a pair of left and right traveling crawlers 3 (shown only on the left side in FIG. 1), and a swivel base 4 (airframe) provided on the traveling device 2. I have. The swivel base 4 is configured to be capable of horizontal swivel over 360 ° in all directions by a swivel motor 9 (see FIG. 2). A soil discharge plate 5 is mounted on the front portion of the traveling device 2 so as to be rotatable up and down.

  The swivel 4 is equipped with a cabin 6 as a control unit and a diesel-type engine 7. A working unit 10 having a boom 11, an arm 12, and a bucket 13 for excavation work is provided at the front of the swivel 4. As shown in detail in FIG. 2, the cabin 6 includes a control seat 8 on which an operator is seated, a throttle lever 116 as a throttle operating means for setting and maintaining the output rotational speed of the engine 7, and a working unit operating means. The lever / switch groups 117 to 120 (the turning operation lever 117, the arm operation lever 118, the bucket operation switch 119, and the boom operation lever 120) are arranged.

  The boom 11, which is a component of the working unit 10, is formed in a shape that protrudes forward at the tip side and is bent in a square shape when viewed from the side. The base end portion of the boom 11 is pivotally attached to a boom bracket 14 attached to the front portion of the swivel base 4 so as to be swingable about a horizontal boom shaft 15. On the inner surface (front surface) side of the boom 11, a one-rod double-acting boom cylinder 16 is disposed for swinging it up and down. The cylinder side end of the boom cylinder 16 is pivotally supported by the front end of the boom bracket 14 so as to be rotatable. The rod side end portion of the boom cylinder 16 is pivotally supported by a front bracket 17 fixed to the front surface side (dent side) of the bent portion of the boom 11. The boom cylinder 16 corresponds to a hydraulic actuator.

  A base end portion of a long rectangular tube-like arm 12 is pivotally attached to a tip end portion of the boom 11 so as to be swingable about a lateral arm shaft 19. A one-rod double-acting arm cylinder 20 for swinging and swinging the arm 12 is disposed on the upper front side of the boom 11. The cylinder side end portion of the arm cylinder 20 is pivotally supported by a rear bracket 18 fixed to the back side (projecting side) of the bent portion of the boom 11. The rod side end of the arm cylinder 20 is pivotally supported by an arm bracket 21 fixed to the base end side outer surface (front surface) of the arm 12.

  A bucket 13 as an attachment for excavation is pivotally attached to the distal end portion of the arm 12 so that the bucket 13 can be swung around a lateral bucket shaft 22. On the outer surface (front surface) side of the arm 12, a one-rod double-acting bucket cylinder 23 for scrambling and rotating the bucket 13 is disposed. A cylinder side end portion of the bucket cylinder 23 is pivotally supported by the arm bracket 21. The rod side end of the bucket cylinder 23 is pivotally supported by the bucket 13 via a connecting link 24 and a relay rod 25. The swing motor 9, the arm cylinder 20, and the bucket cylinder 23 also correspond to hydraulic actuators.

(2). Next, the structure of the hydraulic system 30 of the backhoe 1 will be described with reference to FIG.

  The hydraulic system 30 of the backhoe 1 shown in FIG. 3 includes a variable displacement hydraulic pump motor 31 and a variable displacement hydraulic pump 32 as hydraulic sources. An output shaft 27 protruding from the engine 7 passes through the pumps 31 and 32 group, and the pumps 31 and 32 group are configured to be driven by the rotation of the output shaft 27. That is, the rotating shaft (output shaft 27) for driving the pumps 31 and 32 is a common shaft.

  The hydraulic pump motor 31 is for supplying hydraulic oil to the boom cylinder 16 that requires a relatively large driving force. The hydraulic pump 32 is for supplying hydraulic oil to the swing motor 9, the arm cylinder 20 and the bucket cylinder 23.

(2-1). Structure of Closed Loop Hydraulic Circuit First, the closed loop hydraulic circuit 34 that drives the boom cylinder 16 will be described. The closed-loop hydraulic circuit 34 includes the above-described single-rod double-acting boom cylinder 16 and a hydraulic pump motor 31 that is a swash plate type axial piston pump motor. The boom cylinder 16 and the hydraulic pump motor 31 are connected in a closed loop by a bottom side oil passage 35 and a rod side oil passage 36. In this case, the bottom oil chamber 37 of the boom cylinder 16 is connected to the hydraulic pump motor 31 via the bottom side oil passage 35, and the rod oil chamber 38 of the boom cylinder 16 is connected to the hydraulic pump motor 31 via the rod side oil passage 36. It is connected.

  For this reason, hydraulic oil from the boom cylinder 16 is supplied to the hydraulic pump motor 31 via the bottom side or rod side oil passages 35 and 36, and as a result, the hydraulic pump motor 31 exhibits an action as a motor. The driving of the hydraulic pump 32 on the common output shaft 27 is partially or entirely borne. That is, since the driving load of the hydraulic pump 32 is reduced by the motor-like operation of the hydraulic pump motor 31, the work amount of the engine as a whole can be reduced, which is effective in improving fuel consumption.

  The closed loop hydraulic circuit 34 includes a hydraulic servo mechanism 40 that controls the inclination angle (swash plate angle) of the movable swash plate 31 a in the hydraulic pump motor 31. The hydraulic servo mechanism 40 includes a single-rod double-acting adjustment cylinder 41 that changes the inclination angle of the movable swash plate 31a, an adjustment pump 42 that supplies hydraulic oil to the adjustment cylinder 41, and supply of hydraulic oil from the adjustment pump 42. And a 4-port 3-position switching electromagnetic servo valve 43 for adjusting the direction and supply amount.

  The inlet port of the electromagnetic servo valve 43 is connected to the hydraulic oil tank 44 via the adjustment pump 42, and the outlet port is directly connected to the hydraulic oil tank 44. The bottom port of the electromagnetic servo valve 43 is connected to the bottom oil chamber 45 of the double acting adjustment cylinder 41, and the rod side port is connected to the rod oil chamber 46 of the double action adjusting cylinder 41. The tip of the piston rod 47 in the double-action adjusting cylinder 41 is linked to the movable swash plate 31 a of the hydraulic pump motor 31.

  The electromagnetic servo valve 43 has a neutral state and a hydraulic oil supply state to the bottom oil chamber 45 of the double acting adjustment cylinder 41 by excitation of an electromagnetic solenoid corresponding to an operation amount of the boom operation lever 120 disposed in the cabin 6. The double-acting adjustment cylinder 41 is configured to be switched to a hydraulic oil supply state to the rod oil chamber 46.

  When the electromagnetic servo valve 43 is switched and driven by operating the boom operation lever 120, the double-action adjusting cylinder 41 expands and contracts, and the inclination angle of the movable swash plate 31a in the hydraulic pump motor 31 is changed / adjusted. The supply direction and supply amount of hydraulic oil from 31 to the boom cylinder 16 are adjusted. As a result, the expansion / contraction direction and the expansion / contraction amount of the boom cylinder 16 are changed steplessly, and the boom 11 swings up and down.

  Between the bottom side oil passage 35 and the rod side oil passage 36, a three-port three-position switching type direction switching valve 50 is disposed. In the direction switching valve 50, the amount of hydraulic oil flowing out from one oil chamber 37 due to the pressure receiving area difference between the two oil chambers 37, 38 in the boom cylinder 16 is greater than the amount of hydraulic oil flowing into the other oil chamber 38. This is to discharge the surplus when there are many.

  One inlet port in the direction switching valve 50 is connected to the bottom oil passage 35 via the first inlet oil passage 51, and the other inlet port is connected to the rod side oil passage 36 via the second inlet oil passage 52. It is connected. The outlet port of the direction switching valve 50 is connected to the hydraulic oil tank 44 via the drain oil passage 53.

  Further, the direction switching valve 50 is connected to the bottom side oil passage 35 via the bottom side pilot oil passage 54, and is connected to the rod side oil passage 36 via the rod side pilot oil passage 55. For this reason, the pressure of the bottom pilot oil passage 54 is substantially the same as the pressure of the bottom oil passage 35, and hence the pressure of the bottom oil chamber 37 in the boom cylinder 16. The pressure in the rod-side pilot oil passage 55 is substantially the same as the pressure in the rod-side oil passage 36 and, consequently, the pressure in the rod oil chamber 38 in the boom cylinder 16.

  The direction switching valve 50 has a neutral state, a hydraulic oil discharge state from the bottom side oil passage 35 to the drain oil passage 53, and a drain oil from the rod side oil passage 36 according to the pressure difference between the pilot oil passages 54 and 55. It is configured to be switched to a hydraulic oil discharge state to the passage 53. Due to the action of the direction switching valve 50, the imbalance in the amount of hydraulic fluid flowing between the bottom side and rod side oil passages 35 and 36 is corrected, and the boom cylinder 16 smoothly expands and contracts.

  A charge relief circuit 60 having two relief valves 63 and 64 and two check valves 65 and 66 is disposed between the bottom side oil passage 35 and the rod side oil passage 36. Basically, if the pressure in one oil passage 35 (36) becomes too high, the charge relief circuit 60 does not supply hydraulic oil to one oil chamber 37 (38) in the boom cylinder 16, but the other oil. It is configured to escape to the passage 36 (35) and the hydraulic oil tank 44 to prevent overload of the closed loop hydraulic circuit 34. When the amount of hydraulic oil in the closed loop hydraulic circuit 34 is small, the hydraulic oil is supplied from the hydraulic oil tank 44 through the charge relief circuit 60 by the self-priming force of the hydraulic pump motor 31.

  In the embodiment, a pair of bypass oil passages 61 and 62 are connected in parallel to the bottom side oil passage 35 and the rod side oil passage 36. A first relief valve 63 for releasing the pressure in the bottom side oil passage 35 and a second relief valve 64 for releasing the pressure in the rod side oil passage 36 are provided in the cylinder side bypass oil passage 61. ing. In the pump-side bypass oil passage 62, a first check valve 65 that opens only in the direction of the bottom-side oil passage 35 and a second check valve 66 that opens only in the direction of the rod-side oil passage 36 are provided. .

  A discharge oil passage 67 connects between the relief valves 64 and 65 in the cylinder-side bypass oil passage 61 and between the check valves 66 and 67 in the pump-side bypass oil passage 62. The leading end of the discharge oil passage 67 is connected to the middle portion of the drain oil passage 53. Accordingly, the drain oil passage 67 communicates with the hydraulic oil tank 44 via the drain oil passage 53.

(2-2). Structure of Charge Hydraulic Circuit Next, the charge hydraulic circuit 74 that drives the swing motor 9, the arm cylinder 20, and the bucket cylinder 23 will be described. The charge hydraulic circuit 74 includes the swing motor 9, the single rod double acting arm cylinder 20, the single rod double acting bucket cylinder 23, the hydraulic pump 32 which is a swash plate type axial piston pump, and hydraulic adjustment. And a mechanism 75.

  The suction side of the hydraulic pump 32 communicates with the hydraulic oil tank 44 via the suction oil passage 76. The swing motor 9, the arm cylinder 20, and the bucket cylinder 23 are branched and connected to the charge oil passage 77 extending from the discharge side of the hydraulic pump 32 via corresponding flow control valve units 78, 79, and 80.

  The flow control valve unit 78 for turning is in a neutral state according to the amount of operation of the turning operation lever 117 disposed in the cabin 6, and in a state where hydraulic oil is supplied to one motor oil passage 81 for the turning motor 9. It is configured to be switched to a hydraulic oil supply state to the other motor oil passage 82. When the flow control valve unit 78 for turning is switched by operating the turning operation lever 117, the supply direction and the supply amount of hydraulic oil from the hydraulic pump 32 to the turning motor 9 are adjusted. As a result, the rotation direction and the rotation amount of the turning motor 9 are changed steplessly, and the turntable 4 turns horizontally.

  The flow control valve unit 79 for the arm includes a neutral state, a hydraulic oil supply state to the bottom side oil passage 83 with respect to the arm cylinder 20, and a rod according to the operation amount of the arm operation lever 118 disposed in the cabin 6. The drive oil is configured to be switched to a hydraulic oil supply state to the side oil passage 84. When the arm flow control valve unit 79 is switched and operated by operating the arm operation lever 118, the supply direction and supply amount of hydraulic oil from the hydraulic pump 32 to the arm cylinder 20 are adjusted. As a result, the direction and amount of expansion and contraction of the arm cylinder 20 are changed steplessly, and the arm 12 swings up and down.

  The bucket flow control valve unit 80 includes a neutral state, a hydraulic oil supply state to the bottom side oil passage 85 with respect to the bucket cylinder 23, and a rod side oil passage 86 according to the operation amount of the sliding bucket operation switch 119. It is configured to switch to the hydraulic oil supply state. When the bucket flow control valve unit 80 is switched and driven by operating the bucket operation switch 119, the supply direction and supply amount of hydraulic oil from the hydraulic pump 32 to the bucket cylinder 23 are adjusted. As a result, the expansion / contraction direction and the expansion / contraction amount of the bucket cylinder 23 are changed steplessly, and the bucket 13 at the distal end portion of the arm 12 scoops and rotates around the lateral bucket shaft 22.

  The hydraulic adjustment mechanism 75 is for controlling the inclination angle of the movable swash plate 32a in the hydraulic pump 32. The single-rod single-acting adjustment cylinder 90 that changes the inclination angle of the movable swash plate 32a, and the hydraulic pump 32. And a three-port two-position switching electromagnetic servo valve 91 for adjusting the supply direction and supply amount of hydraulic oil from the single-acting adjustment cylinder 90 to the single-acting adjustment cylinder 90.

  The oil path side first port of the charging electromagnetic servo valve 91 is connected between the hydraulic pump 32 in the charge oil path 77 and the branching portion 87 to each flow control valve unit 78-80, and the oil path side second port is Directly connected to the hydraulic oil tank 44. The cylinder side port of the charging electromagnetic servo valve 91 is connected to the bottom oil chamber of the single acting adjustment cylinder 90. In the rod chamber of the single-acting adjustment cylinder 90, a return spring 95 that urges the piston rod 94 in the direction of shortening is housed. The tip of the piston rod 94 in the single-acting adjustment cylinder 90 is linked to the movable swash plate 32 a of the hydraulic pump 32.

  The charging electromagnetic servo valve 91 is connected between the hydraulic pump 32 and the branch portion 87 in the charge oil passage 77 via the first pilot oil passage 96, while being connected via the second pilot oil passage 97. It is connected to each flow control valve unit 78-80. For this reason, the pressure in the first pilot oil passage 96 is substantially the same as the pressure on the discharge side of the hydraulic pump 32. The pressure in the second pilot oil passage 97 is substantially the same as the highest pressure among the suction side pressures in the swing motor 9, the arm cylinder 20, and the bucket cylinder 23.

  In this case, the charging electromagnetic servo valve 91 basically has a hydraulic oil supply state to the bottom oil chamber of the single acting adjustment cylinder 90 according to the pressure difference between the first and second pilot oil passages 96 and 97, and the bottom. It is configured to be switched to a hydraulic oil discharge state from the oil chamber.

  When the pressure difference between the first and second pilot oil passages 96 and 97 deviates from a predetermined range set in advance and the charging electromagnetic servo valve 91 is switched, the single-acting adjustment cylinder 90 expands and contracts, and the hydraulic pump 32 The inclination angle of the movable swash plate 32a is changed and adjusted, and the supply direction and supply amount of hydraulic oil from the hydraulic pump 32 to each hydraulic actuator (in this case, the swing motor 9, the arm cylinder 20 and the bucket cylinder 23) are adjusted. The

  As a result, the difference between the pressure on the discharge side of the hydraulic pump 32 and the pressure on the suction side of each hydraulic actuator 9, 20, 23 is adjusted within a predetermined range, so that the load applied to each hydraulic actuator 9, 20, 23 is increased or decreased. Regardless, the amount of hydraulic oil supplied to each hydraulic actuator 9, 20, 23 is kept substantially constant. That is, a load sensing function for maintaining the operating speed of each hydraulic actuator 9, 20, 23 substantially constant works.

(3). Configuration for Executing Fuel Injection Control Next, a configuration for executing fuel injection control of the backhoe 1 will be described with reference to FIGS. 4 and 5.

  The backhoe 1 is equipped with a main unit controller 101 and an electronic governor controller 102 as control means. These controllers 101 and 102 are for controlling the overall operation of the backhoe 1 and for performing fuel injection control and the like to be described later. In addition to the CPUs 101a and 102a for executing various arithmetic processes and controls, control programs and data ROM 101b and 102b as storage means for storing the data, RAMs 101c and 102c for temporarily storing a control program and data, an input / output interface, and the like. The main controller 101 and the electronic governor controller 102 are electrically connected to each other via the CAN communication bus 100.

  The controller 101 is connected to a battery 104 via a key switch 103 for applying power. The key switch 103 is also connected to a starter 105 for starting the engine 7. Further, in this machine controller 101, as output-related devices, an electromagnetic servo valve 43 for adjusting the supply direction and supply amount of hydraulic oil from the adjustment pump 42, the supply direction of hydraulic oil from the hydraulic pump 32, and A charging electromagnetic servo valve 91 for adjusting the supply amount is connected. Further, the machine controller 101 includes lever / switch groups 117 to 120 arranged in the cabin 6 as input-related devices (the turning operation lever 117, the arm operation lever 118, the bucket operation switch 119, and the boom operation lever 120). The first hydraulic sensor 121 as hydraulic pressure detecting means for detecting the hydraulic pressure of the hydraulic oil supplied from the hydraulic pump motor 31 on the closed loop hydraulic circuit 34 side, and the hydraulic oil supplied from the hydraulic pump 32 on the charge hydraulic circuit 74 side A second hydraulic pressure sensor 122 or the like serving as a hydraulic pressure detecting means for detecting the hydraulic pressure is connected.

  The electronic governor controller 102 includes an electronic governor 107 provided in a fuel injection pump 106 that is a fuel injection device, an engine rotation sensor 108 as a rotation speed detection means for detecting the engine rotation speed, and a rack position of the fuel injection pump 106. The power generation amount of the rack position sensor 109 as a load detection means for detecting the fuel injection amount from the throttle, the throttle potentiometer 110 for detecting the operation position of the throttle lever 116, and the alternator 111 as a generator for generating power with the power of the engine 7 A power generation amount sensor 112 is connected as a power generation amount detecting means for detecting. The electronic governor 107 has a rack actuator (not shown) for adjusting the rack position of the fuel injection pump 106.

  The ROM 102b of the electronic governor controller 102 stores in advance an output characteristic map MP (see FIG. 5) as a control pattern indicating the relationship between the engine speed N and the rack position R (fuel injection amount). This type of output characteristic map MP is obtained through experiments or the like. The control pattern is not limited to the map format as in the embodiment, but may be a function table format, for example.

  In the output characteristic map MP shown in FIG. 5, the engine speed N is taken on the horizontal axis, and the rack position R (fuel injection amount) is taken on the vertical axis. In the output characteristic map, a solid line Rmax drawn in an upward convex curve is a maximum rack position line representing the maximum rack position with respect to each engine speed N. A solid line Rmin drawn in a substantially L shape is a minimum rack position line representing the minimum rack position for each engine speed N, and the fuel injection amount at this time is 0 (zero). A curved solid line Ridl drawn between the maximum rack position line Rmax and the minimum rack position line Rmin is a no-load rack position line representing the no-load rack position with respect to each engine speed N. Furthermore, a two-dot chain line Rmod drawn in the low-speed rotation region (the region on the left side of FIG. 5 where the engine speed N is low) is a correction rack position line for temporarily raising the maximum rack position in the low-speed rotation region. .

  The electronic governor controller 102 mainly includes an actual measurement value Ni of the engine speed N detected by the engine speed sensor 108, a target value Ns of the engine speed N detected by the throttle potentiometer 110, and a rack position sensor 109. Fuel injection control in which the target value Rs of the fuel injection amount is calculated from the measured value Ra of the detected fuel injection amount (rack position R) using the output characteristic map MP, and the rack actuator is driven according to the calculation result. Is configured to run.

(4). Description of Fuel Injection Control Next, an example of fuel injection control will be described with reference to the flowcharts shown in FIGS.

  As an example of fuel injection control, the electronic governor controller 102 according to the embodiment has a maximum fuel injection amount in the low speed rotation region when the engine speed N decreases due to an increase in engine load during low speed rotation of the engine 7. The output characteristic map MP is temporarily corrected so that the (maximum rack position) increases, and the corrected injection control for controlling the operation of the fuel injection pump 106 based on the corrected output characteristic map MP is executed. Has been. This correction injection control is interrupted during execution of normal fuel injection control.

  The flow of the first embodiment of the correction injection control will be described with reference to the flowchart of FIG. Here, the target value Ns of the engine speed N is set in advance by the throttle lever 116, and a set reduction rate D0, a set load rate Z0 and a set time T0 per unit time of the engine speed N, which will be described later, are determined by the electronic governor controller. It is assumed that it is set in advance, for example, by being stored in the ROM 102b or the like of 102. Further, it is assumed that a correction execution flag F, which will be described later, is set to a reset state (F = 0) when the engine 7 is started (when the electronic governor controller 102 is started).

  In the correction injection control of the first embodiment, first, an actual measurement value Ni of the engine speed N detected by the engine rotation sensor 108 and an actual measurement value Ra of the fuel injection amount (rack position R) corresponding to the actual measurement value Ni. Are read at appropriate intervals, and the target value Ns of the engine speed N, the set reduction rate D0 per unit time of the engine speed N, and the set load ratio Z0 are read (step S1).

  Next, a decrease rate D per unit time of the engine speed N is calculated from the actually measured value Ni (1) read earlier and the actually measured value Ni (2) read later (step S2). Here, the decrease rate D is expressed as a percentage of a value obtained by dividing the difference between the previous actual measurement value Ni (1) and the subsequent actual measurement value Ni (2) by the previous actual measurement value Ni (1). . That is, D = {(Ni (1) −Ni (2)} / Ni (1) × 100).

  Next, it is determined whether or not the decrease rate D calculated in step S2 is equal to or greater than a set decrease rate D0 (predetermined value) (step S3). When the rate of decrease D is equal to or greater than the set rate of decrease D0, the load on the engine 7 increases as the load on the hydraulic pump motor 31 and the hydraulic pump 32 suddenly increases during the low speed rotation of the engine 7, resulting in an increase in engine rotation. This means that the number N has decreased. In this state, the output torque of the engine 7 cannot follow the increased load of the hydraulic pump motor 31 and the hydraulic pump 32, and the engine torque becomes insufficient, causing black smoke to be knocked or cause engine stall. .

  Even if the difference between the previous actual measurement value Ni (1) and the subsequent actual measurement value Ni (2) is not so large, the previous actual measurement value Ni (1) serving as the denominator of the decrease rate D is, for example, about the low idle rotational speed. If the value is small, the decrease rate D is a large value. For this reason, it is possible to determine that the engine 7 is rotating at a low speed and the engine speed N is decreased only by the decrease rate D per unit time of the engine speed N.

  Therefore, if the decrease rate D calculated in step S2 is less than the set decrease rate D0 (S3: NO), there will be no situation where the output torque of the engine 7 becomes insufficient, and the correction injection control routine is immediately exited ( Return to normal fuel injection control. On the other hand, if the decrease rate D calculated in step S2 is equal to or greater than the set decrease rate D0 (S3: YES), the output torque of the engine 7 is insufficient as it is, and then the correction execution flag F is reset (F = 0) or not (step S4).

  The correction execution flag F is a flag for determining whether or not the correction injection control has been executed so far after the engine 7 is started. If the correction execution flag F is in the set state (F = 1) (S4: NO), since the correction injection control has been executed at least once after the engine 7 is started, the routine proceeds to step S15 described later.

  If the correction execution flag F is in the reset state (F = 0) (S4: YES), the correction injection control has not been executed once after the engine 7 is started. Correction for temporarily switching the portion of the maximum rack position line Rmax of the output characteristic map MP that corresponds to the low-speed rotation region of the engine 7 to the correction rack position line Rmod positioned above this so that the fuel injection amount increases. Execute (Step S5).

  Then, the target value Rs of the fuel injection amount (rack position R) is calculated using the corrected rack position line Rmod obtained by temporarily raising the maximum rack position in the low speed rotation range, and the rack actuator is operated according to the calculation result. Correction injection control of driving is executed (step S6).

  Next, the actual measured value Ni (3) of the current engine speed N is detected and read by the engine speed sensor (step S7), and the actual measured value Ni (3) is the value of the engine speed N read in step S1. It is determined whether or not the target value Ns has been restored (step S8). If the measured value Ni (3) of the engine speed N has returned to the target value Ns (S8: YES), for example, the correction rack position line Rmod is translated downward gradually (stepwise), and finally Returns the state of the low-speed rotation region in the maximum rack position line Rmax to the original state before correction (step S10).

  If the measured value Ni (3) of the engine speed N has not returned to the target value Ns (S8: NO), then the time T from the execution of the correction injection control in step S6 has passed the set time T0. Whether or not (step S9). The set time T0 of the first embodiment is set to 1 to 3 seconds, for example. If the set time T0 has elapsed (S9: YES), the process proceeds to step S10, and the state of the low speed rotation region at the maximum rack position line Rmax is returned to the original state before correction. If the set time T0 has not elapsed (S9: NO), the process returns to step S7.

  Since the correction injection control forcibly raises the maximum rack position in the low speed rotation region, if the correction injection control is continued for a long time, the burden on the engine 7 is very large. Therefore, in the first embodiment, by performing the steps S7 to S9, the execution time of the correction injection control is shortened as much as possible, the time that the load on the engine 7 is applied is limited to a short time, and the engine 7 is protected. I am trying.

  In step S10, after the state of the low speed rotation range on the maximum rack position line Rmax is returned to the original state before correction, the target value Ns (x) of the engine speed N at this time and the actual value of the rack position R are measured. Ra (x) is read (step S11), the load factor Z (x) of the engine 7 is calculated from the measured value Ra (x) of the rack position R according to the output characteristic map MP, and the RAM 102c of the electronic governor controller 102, etc. (Step S12). The target value Ns (x) of the engine speed N and the load factor Z (x) are used as discrimination criteria in step S15 and later described later.

  Here, the load factor Z of the engine 7 (the same applies to Z (x)) means that between any point Ri on the no-load rack position line Ridl and a point Rm on the maximum rack position line Rmax at any engine speed N. The width is assumed to be 100%, and the ratio of the width between the point Ri on the no-load rack position line Ridl and the actual measurement value Ra of the rack position R is shown. That is, it is expressed as Z = (Ra−Ri) / (Rm−Ri) × 100.

  After execution of step S12, it is determined whether or not the correction execution flag F is in a reset state (step S13). If the correction execution flag F is in the reset state (S13: YES), after changing to the set state (step S14), the correction injection control routine is exited and the normal fuel injection control is resumed. If it is in the set state (S13: NO), the routine exits the correction injection control routine and returns to normal fuel injection control.

  As described above, in step S4, if the corrected injection control has been executed at least once after the engine 7 is started (S4: NO), the process proceeds to step S15. In step S15, the load factor Z of the engine 7 is calculated according to the output characteristic map MP from the actually measured value Ra (1) of the rack position R previously read in step S1.

  Next, it is determined whether or not the load factor Z calculated in step S15 is equal to or greater than a set load factor Z0 (specified value) (step S16). The case where the load factor Z is equal to or greater than the set load factor Z0 means that a load larger than the output torque of the engine 7 (for example, a load caused by hydraulic pressure) may be continuously acting on the engine 7. Yes. In this state, since the correction injection control is repeatedly performed, the burden on the engine 7 is very large, which may cause the engine 7 to fail.

  Therefore, if the load factor Z calculated in step S15 is equal to or greater than the set load factor Z0 (S16: YES), the correction injection control routine is exited as it is in order to prevent repeated execution of the correction injection control. Return to fuel injection control. On the other hand, if the load factor Z calculated in step S15 is less than the set load factor (S16: NO), then, the target value Ns of the engine speed N read in step S1 and the correction performed last time. It is determined whether or not the target value Ns (x) of the engine speed N stored in the RAM 102c in step S12 of the injection control is the same (step S17).

  If the target value Ns and the previously stored target value Ns (x) are the same (S17: YES), a load larger than the output torque of the engine 7 continuously acts on the engine 7 as in the case of step S16 YES. Therefore, the correction injection control routine is exited and the normal fuel injection control is resumed. If the target value Ns is different from the previously stored target value Ns (x) (S17: NO), then, the load factor Z calculated in step S15 and step S12 of the corrected injection control performed last time. Whether or not the load factor Z (x) of the engine 7 stored in the RAM 102c is the same is determined (step S18).

  If load factor Z and load factor Z (x) stored last time are the same (S18: YES), a load larger than the output torque of engine 7 is continuously applied to engine 7 as in the case of steps S16 YES and S17 YES. Therefore, the control exits the correction injection control routine and returns to normal fuel injection control. If the load factor Z and the previously stored load factor Z (x) are different (S18: NO), the process proceeds to step S5 described above, and the portion corresponding to the low speed rotation region of the maximum rack position line Rmax is corrected rack. Correction for temporarily switching to the position line Rmod is executed.

  As can be seen from the above description, in the first embodiment, if the correction injection control has been executed at least once after the engine 7 is started, the steps of steps S15 to S18 are performed. The repeated execution is prevented and the engine 7 is protected.

  According to the above configuration, when the engine speed N decreases due to an increase in engine load during low speed rotation of the engine 7, the output characteristic map is set so that the maximum fuel injection amount in the low speed rotation range of the engine 7 increases. Since the MP is temporarily corrected (see step S5), even if the load applied to the engine 7 increases due to, for example, hydraulic pressure during the low-speed rotation of the engine 7, the maximum fuel injection amount (maximum rack) The output torque of the engine 7 can be increased by temporarily raising the position). Therefore, a decrease in the engine speed N due to insufficient torque can be eliminated, black smoke and knocking can be prevented, and the possibility of engine stall can be suppressed.

  Further, when the decrease rate D of the engine speed N is equal to or greater than the set decrease rate D0 (predetermined value), the output characteristic map MP is temporarily corrected (see Steps S3 to S5). It can be prevented that the increase in the load of the engine 7 due to the acceleration of 2 is a load increase caused by, for example, hydraulic pressure. Further, even when the engine speed N decreases along the maximum rack position line Rmax of the output characteristic map MP during excavation or the like, there is a risk that such a decrease in the rotational speed may be mistaken as a load increase caused by, for example, hydraulic pressure or the like. Also disappear. Therefore, it is possible to appropriately execute the correction injection control (temporary correction of the output characteristic map MP).

  Further, after the output characteristic map MP is temporarily corrected, the output characteristic map MP is returned to the original state when the set time T0 has elapsed (see step S9), and therefore the execution time of the corrected injection control. The time required for the engine 7 can be limited, which contributes to the protection of the engine 7. In particular, in the first embodiment, after temporarily correcting the output characteristic map MP, if either the elapse of the set time T0 or the return of the engine speed N to the target value Ns is established first, the output characteristic map Since the MP is configured to return to the original state (see Steps S7 to S9), the load on the engine 7 can be limited to a shorter time, which is highly effective in terms of protecting the engine 7.

  In addition, when returning the output characteristic map MP to the original state, the correction rack position line Rmod is translated downward gradually (stepwise), and finally, the state of the low speed rotation region at the maximum rack position line Rmax is changed. Since the maximum fuel injection amount (maximum rack position) in the low-speed rotation region is gradually shifted so as to return to the original state before correction (see step S10), the maximum fuel injection amount (maximum rack position). This prevents the undershoot from occurring and can return to the original state smoothly. Further, since the maximum fuel injection amount (maximum rack position) does not decrease rapidly, safety during driving of the engine 7 can be ensured.

  In the first embodiment, after the output characteristic map MP is returned to the original state, the load factor Z of the engine 7 obtained from the detection information of the rack position sensor 109 is equal to or higher than the set load factor Z0 (specified value). Since the temporary correction of the output characteristic map MP is prohibited (see step S16), a load larger than the output torque of the engine 7 (for example, a load caused by hydraulic pressure) is continuously applied to the engine 7. When there is a possibility of action, it is possible to prevent repeated execution of the correction injection control, and this also contributes to protection of the engine 7.

  Further, after the output characteristic map MP is returned to the original state, the target value Ns of the engine speed N does not change from the value Ns (x) before correction, or the load factor Z of the engine 7 is the value before correction. Even when Z (x) does not change, the temporary correction of the output characteristic map MP is prohibited (see steps S17 and S18). Even in these cases, the correction injection control is repeated. Execution can be prevented and it is effective in terms of protecting the engine 7.

(5). Another Example of Corrected Injection Control FIGS. 7 to 9 show other examples of corrected injection control. The modes of the corrected injection control in these other examples are basically the same as those in the first embodiment described above. However, when the criterion for executing the temporary correction of the output characteristic map MP is the first embodiment (engine rotation) It is different from the decrease rate D) of the number N.

  The flowchart of FIG. 7 shows a second embodiment of the correction injection control, and differences from the first embodiment will be described below. In the correction injection control of the second embodiment, first, the actual measurement value Ni of the engine speed N detected by the engine rotation sensor 108 and the actual measurement value Ra of the fuel injection amount (rack position R) corresponding to the actual measurement value Ni Then, the target value Ns of the engine speed N and the set load factor Z0 are read (step S21).

  Next, it is determined whether the measured value Ni of the engine speed N is less than the low idle speed (step S22). The low idle rotation speed of the second embodiment is set to about 1000 rpm, for example. If the measured value Ni of the engine speed N is equal to or higher than the low idle speed (S22: NO), there will be no situation where the output torque of the engine 7 becomes insufficient. Return to control.

  If the measured value Ni of the engine speed N is less than the low idle speed (S22: YES), then, the difference (Ns−Ni) between the target value Ns of the engine speed N and the measured value Ni is the set speed N0. It is determined whether or not (predetermined value) or more (step S23). The set rotation speed N0 is set in advance by storing it in the ROM 102b of the electronic governor controller 102 or the like. If the difference between the target value Ns of the engine speed N and the measured value Ni is less than the set speed N0 (S23: NO), the output torque of the engine 7 will not be insufficient in this case as well, so that the corrected injection control is performed as it is. Exit the routine and return to normal fuel injection control.

  If the difference between the target value Ns of the engine speed N and the measured value Ni is equal to or greater than the set speed N0 (S23: NO), the load applied to the engine 7 increases during the low speed rotation of the engine 7 and the engine speed. Since N is in a lowered state, the output torque of the engine 7 cannot follow the increase in the load of the hydraulic pump motor 31 or the hydraulic pump 32 and is insufficient. Therefore, the following is performed through steps S24 to S38 which are the same procedure as the correction injection control (steps S4 to S18) of the first embodiment described above.

  Even when such control is executed, the same effects as those of the first embodiment can be obtained. That is, the measured value Ni of the engine speed N is a value less than the low idle speed, and the difference between the target value Ns of the engine speed N and the measured value Ni is greater than or equal to the set speed N0 (predetermined value). Since the output characteristic map MP is temporarily corrected, the correction injection control is performed in the same manner as in the first embodiment in which the determination criterion for executing the correction is the reduction rate D of the engine speed N. (Temporary correction of the output characteristic map MP) can be appropriately executed.

  The flowchart of FIG. 8 shows a third embodiment of the correction injection control, and differences from the first and second embodiments will be described below. In the correction injection control of the third embodiment, first, the hydraulic oil actual measurement value P1 detected by the first hydraulic sensor 121 and the hydraulic oil actual measurement value P2 detected by the second hydraulic sensor 122 are used. It is read in every short time as appropriate, and the actual value Ra of the fuel injection amount (rack position R) detected by the rack position sensor 109, the target value Ns of the engine speed N, and the set load factor Z0 are read (step) S41).

  Next, regarding the first hydraulic pressure sensor 121, the hydraulic pressure change rate ΔP1 on the hydraulic pump motor 31 side is calculated from the hydraulic pressure actual value P1 (1) read earlier and the hydraulic pressure actual value P1 (2) read later. At the same time, regarding the second hydraulic pressure sensor 122, the hydraulic pressure change rate ΔP2 on the hydraulic pump 32 side is calculated from the hydraulic pressure actual value P2 (1) read earlier and the hydraulic pressure actual value P2 (2) read later. Step S42).

  Here, the hydraulic pressure change rates ΔP1 and ΔP2 are the differences between the previous hydraulic pressure actual measurement values P1 (1) and P2 (1) and the subsequent hydraulic pressure actual measurement values P1 (2) and P2 (2). This is expressed as a percentage of the value divided by P1 (1) and P2 (1). That is, ΔP1 = {(P1 (1) −P1 (2)} / P1 (1) × 100, ΔP2 = {(P2 (1) −P2 (2)} / P2 (1) × 100).

  Next, it is determined whether one of the hydraulic pressure change rates ΔP1 and ΔP2 calculated in step S32 is equal to or higher than a set change rate ΔP0 (predetermined value) (step S43). The set change rate ΔP0 is set in advance by storing it in the ROM 102b of the electronic governor controller 102 or the like. If at least one of the hydraulic pressure change rates ΔP1 and ΔP2 is less than the set change rate ΔP0 (S43: NO), the output torque of the engine 7 will not be insufficient in this case as well. Return to the fuel injection control.

  If at least one of the hydraulic pressure change rates ΔP1 and ΔP2 is equal to or higher than the set change rate ΔP0 (S43: YES), the load applied to the engine 7 increases during the low speed rotation of the engine 7 and the engine speed N decreases. Therefore, in this state, the output torque of the engine 7 cannot follow the load increase of the hydraulic pump motor 31 and the hydraulic pump 32 and is insufficient. Therefore, the following is performed through steps S44 to S58 which are the same procedure as the correction injection control (steps S4 to S18) of the first embodiment described above.

  Even when such control is executed, the same effects as those of the first and second embodiments can be obtained. In particular, when at least one of the hydraulic pressure change rates ΔP1 and ΔP2 of the hydraulic oil supplied from the pumps 31 and 32 is equal to or higher than the set change rate ΔP0 (predetermined value), the output characteristic map MP is temporarily corrected. Therefore, for example, the detection timing of the load increase due to the hydraulic pressure or the like is grasped from the hydraulic pressure change rates ΔP1 and ΔP2 of the hydraulic oil from the pumps 31 and 32. For this reason, it becomes possible to make a quicker determination than in the first and second embodiments in which the detection timing is measured based on the engine speed N, and the time required for the correction injection control can be shortened.

  The flowchart of FIG. 9 shows a fourth embodiment of the correction injection control, and differences from the first to third embodiments will be described below. In the correction injection control of the fourth embodiment, first, the power generation amount actual measurement value Ei of the alternator 111 detected by the power generation amount sensor 112 is read appropriately every short time, and the fuel injection amount detected by the rack position sensor 109 is read. The actual value Ra of (rack position R), the target value Ns of the engine speed N, and the set load factor Z0 are read (step S61).

  Next, an output change rate ΔE of the alternator 111 is calculated from the power generation amount actual measurement value Ei (1) read earlier and the power generation amount actual measurement value Ei (2) read later (step S62). Here, the output change rate ΔE is a value obtained by dividing the difference between the previous power generation amount actual measurement value Ei (1) and the subsequent power generation amount actual measurement value Ei (2) by the previous power generation amount actual measurement value Ei (1). It is expressed as a percentage. That is, ΔE = {(Ei (1) −Ei (2)} / Ei (1) × 100.

  Next, it is determined whether or not the output change rate ΔE calculated in step S62 is greater than or equal to a reference change rate ΔE0 (predetermined value) (step S63). The reference change rate ΔE0 is set in advance, for example, by being stored in the ROM 102b of the electronic governor controller 102 or the like. If the output change rate ΔE is less than the reference change rate ΔE0 (S63: NO), the output torque of the engine 7 will not be insufficient in this case as well, so the correction injection control routine is directly exited and normal fuel injection control is performed. Return.

  If the output change rate ΔE is equal to or greater than the reference change rate ΔE0 (S63: YES), the load applied to the engine 7 increases during the low speed rotation of the engine 7 and the engine speed N decreases. The output torque of the engine 7 cannot follow the load increase of the hydraulic pump motor 31 and the hydraulic pump 32 and is insufficient. Therefore, the following is performed through steps S64 to S78 which are the same procedure as the correction injection control (steps S4 to S18) of the first embodiment described above.

  Even when such control is executed, the same effects as those of the first to third embodiments can be obtained. In particular, when the output change rate ΔE of the alternator 111 is greater than or equal to a reference change rate ΔE0 (predetermined value), the output characteristic map MP is temporarily corrected. For example, an increase in load caused by, for example, hydraulic pressure is detected. The timing is grasped from the output change rate ΔE of the alternator 111. This makes it possible to make a quicker determination than in the first and second embodiments in which the detection timing is measured based on the engine speed N, and the time required for the correction injection control is reduced as in the third embodiment. It can be shortened.

(6). Others The present invention is not limited to the above-described embodiment, and can be embodied in various forms. For example, the present invention is not limited to a backhoe, but can also be applied to agricultural machines such as a combiner and special work vehicles such as a wheel loader. In addition, the configuration of each unit is not limited to the illustrated embodiment, and various modifications can be made without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1 Backhoe 7 as a working machine Engine 10 Working part 31 Hydraulic pump motor 32 as a hydraulic source Hydraulic pump 101 as a hydraulic source This machine controller 102 as a control means Electronic governor controller 106 as a control means 106 Fuel injection pump 107 Electronic governor 108 Engine rotation sensor 109 as rotation speed detection means Rack position sensor 121 as load detection means First hydraulic pressure sensor 122 Second hydraulic pressure sensor

Claims (1)

An engine, a hydraulic source that is rotationally driven by the engine, a working unit that is driven by hydraulic oil supplied from the hydraulic source, a fuel injection device that injects fuel into the engine, and a rotational speed detection that detects the rotational speed of the engine Means, storage means for storing in advance a control pattern indicating the relationship between the engine speed and the fuel injection amount, and control means for controlling the operation of the fuel injection device based on the control pattern , In the work machine set by the low idle speed that suppresses the idling speed of the engine in the idle state as low as possible ,
When the engine speed decreases due to an increase in engine load during low-speed rotation of the engine, the control means temporarily sets the control pattern so that the maximum fuel injection amount in the low-speed rotation range of the engine increases. And correcting injection control for controlling the fuel injection amount based on the corrected control pattern,
When the measured value of the engine speed is less than the low idle speed and the difference between the target value of the engine speed and the measured value is greater than or equal to a predetermined value, the corrected injection control is executed .
When the corrected injection control is executed at least once after the engine is started, the load factor of the engine obtained from the load detection means for detecting the load of the engine is a specified value or more, or the load factor of the engine is not corrected. When the target value of the engine speed does not change from the value before correction, execution of the correction injection control is prohibited.
Work machine.

Images