JP2008088776A - Swing cylinder control device of turning working machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a swing cylinder control device and a control method capable of reducing rigidity required for a working device and alleviating a load, in a turning working machine in which the working device is made to be swingable by the swing cylinder. <P>SOLUTION: The swing cylinder control device of the turning working machine is mounted to a relief valve (100) for setting the relief pressure (Ps) of a rod-side pressure chamber (34a) and a bottom-side pressure chamber (34b) of the swing cylinder (34), respectively. The swing cylinder control device comprises a control pressure chamber (104) capable of receiving the control pressure in a direction against an urging force of a relief spring (102), and solenoid proportional pressure-reducing valves (114a, 114b) generating the control pressure based on an operation signal of a turning operation lever (46m) using a supply pilot pressure from a pilot pressure pump (58) as initial pressure, and supplying the control pressure to the control pressure chamber (104) of the targeted relief valve (100). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a control device for controlling the expansion / contraction rigidity of a swing cylinder in a swing work machine in which a work device having a work attachment such as a drilling bucket at the tip can swing left and right by expansion and contraction of the swing cylinder.

A swing-type hydraulic excavator is known as this type of swing work machine. In the case of this swing-type hydraulic excavator, a work device having an excavation bucket can swing in the left-right direction with respect to the upper swing body ( For example, see Patent Document 1).
More specifically, the work device has a boom and an arm extending from the upper swing body, and a drilling bucket is attached to the tip of the arm. On the other hand, a swing post swingable in a horizontal plane is provided at the front part of the upper swing body, and a base end portion of a boom in the work device is supported by the swing post so as to be raised and lowered. On the other hand, the swing post and the upper swing body are connected to each other by a double-acting swing cylinder. By extending and retracting the swing cylinder, the work device swings through the swing post, thereby On the other hand, the working device can be positioned at a desired swing angle.

Therefore, in the above-described swing-type hydraulic excavator, even if the front part of the upper swing body does not face the side groove to be excavated, the working device is arranged along the side groove by the swinging thereof. Since it is possible, it is suitable for the excavation work of a gutter.
Japanese Patent No. 3119293

During excavation work, the expansion and contraction rigidity of the swing cylinder is maintained extremely high.
On the other hand, since the excavation work involves a turning operation of the upper swing body, the excavation bucket of the work device may collide with an unexpected obstacle when the upper swing body turns. In such a turning collision, since the expansion and contraction rigidity of the swing cylinder is extremely high, a great torsional moment and bending moment are applied to the base end portion of the boom in the working device.

For this reason, the working device is required to have an excessive rigidity to withstand the impact at the time of a turning collision, which necessitates an increase in the scale and weight of the working device, which is a major factor that increases the manufacturing cost of the working device. Yes.
The present invention has been made based on the above-described circumstances, and the object of the present invention is to reduce the turning impact force received by the work device even when the work device turns and collide, and to reduce the rigidity required of the work device. The present invention is to provide a swing cylinder control device for a swing work machine that can be simplified in structure and weight and can reduce the manufacturing cost.

  In order to achieve the above object, the present invention provides a lower traveling body, an upper revolving body that is turnably provided on the lower traveling body, and revolves according to an operation amount from an operation lever, and is supported on a front portion of the upper revolving body. The swing post can be swung left and right in a horizontal plane, and is placed on either the left or right side of the upper swing body centering on the swing post, and the upper swing body and the swing post are connected to swing the swing post. A swing cylinder control device according to the present invention, comprising: a double-action swing cylinder to be moved; and a swing work machine having a work device supported by the swing post so as to be raised and lowered and having a work attachment movable in the front-rear and vertical directions. Is provided in a hydraulic path that supplies and discharges hydraulic oil to and from the swing cylinder, and a pair of reliefs that respectively determine the relief pressures of both pressure chambers of the swing cylinder. And a reducing means for reducing the relief pressure of the relief valve selected according to the arrangement of the swing cylinder and the turning direction of the upper turning body of the pair of relief valves in accordance with the operation amount of the operation lever. Item 1).

  According to the swing cylinder control device of the first aspect described above, during the turning of the upper swing body, the relief valve selected according to the arrangement of the swing cylinder with respect to the swing post and the swing direction of the upper swing body, specifically, the working device When a turning collision is considered, a relief valve on the side that extends or contracts the swing cylinder is selected to allow the swing of the work device in the direction opposite to the turning direction of the upper turning body, and the relief of the selected relief valve is selected. The pressure is reduced according to the operation amount of the operation lever.

  Therefore, if the working device turns and collides, and if a large torsional moment or bending moment that overcomes the expansion / contraction rigidity of the swing cylinder is applied to the base end of the working device, the relief pressure of the relief valve is reduced at this time. Therefore, the swing cylinder extends or contracts so that the relief pressure of the swing cylinder is passively swung in the direction opposite to the swing direction of the upper swing body, thereby reducing the swing impact force received by the work apparatus. Is done.

Further, the relief pressure of the relief valve is greatly reduced as the operation amount of the operation lever is increased and the turning speed of the upper turning body is increased, and the turning impact force on the working device is optimally reduced.
Specifically, each relief valve includes a relief spring that biases the valve body in one direction, and a control pressure chamber that receives supply of control pressure that biases the valve body in a direction opposite to the biasing direction of the relief spring. And the reducing means supplies the control pressure corresponding to the operation amount of the operation lever to the control pressure chamber of the selected relief valve to reduce the relief pressure of the selected relief valve.

  Specifically, the turning work machine is a pilot pressure source and a pair of pilot valves connected to the pilot pressure source and operated by an operation lever, and the corresponding pilot according to the operation direction and the operation amount of the operation lever. A pair of pilot valves that generate an operation pilot pressure as an operation amount from the original pressure of the pilot pressure source when the valve is operated, and a turn that turns the upper swing body in a predetermined direction based on the operation pilot pressure from the pilot valve In this case, the reducing means includes a pressure reducing valve provided between the pilot pressure source and the control pressure chamber of the relief valve, and is selected based on the operating pilot pressure from each pilot valve. The pressure reducing valve on the relief valve side can be operated (Claim 3).

Further, the reducing means further includes a detector for detecting a work situation including the swing cylinder operating posture and the work attachment work position, and corrects the operation of the pressure reducing valve based on the work situation detected by the detector. (Claim 4).
The above-mentioned reducing means reduces the relief pressure of the selected relief valve based on not only the operation amount of the operation lever but also the above-mentioned work situation, and the expansion / contraction rigidity of the swing cylinder is undesirably lowered. There is no.

  On the other hand, the reducing means includes a connection path that connects the pilot valve and the control pressure chamber of the relief valve, respectively, and the operating pilot pressure from the pilot valve can be directly applied to the control pressure chamber of the relief valve. 5). In this case, when the operation lever is operated, the corresponding pilot valve generates an operation pilot pressure as an operation amount, and this operation pilot pressure is directly supplied to the control pressure chamber of the relief valve. That is, in this case, the operation pilot pressure is used as the control pressure.

  Further, the reducing means includes a pressure reducing valve provided in a connection path connecting the pilot valve and the control pressure chamber of the relief valve, respectively, and the operation pilot pressure from the pilot valve can be used as the original pressure of the pressure reducing valve. (Claim 6).

  The swing cylinder control device for a swing working machine according to any one of claims 1 to 6, wherein the swing is controlled according to at least the operation amount of the operation lever among the operation amount of the operation lever and the work status of the swing cylinder and the work attachment during the turning of the upper swing body. Since the relief pressure of the cylinder is reduced to reduce the expansion and contraction rigidity of the swing cylinder, even if the work attachment of the work device collides with an obstacle, the work device can be The swing collision force that is passively swung and received by the working device is effectively reduced. Further, since the relief pressure of the swing cylinder can be varied, the expansion / contraction rigidity of the swing cylinder is not excessively increased. As a result, the rigidity required of the working device can be reduced, the structure can be simplified and the weight can be reduced, and an inexpensive working device can be obtained.

1 and 2 show a swing type mini excavator as a swing working machine.
The mini excavator includes a self-propelled crawler-type lower traveling body 2, and an upper revolving body 6 is mounted on the upper side of the lower traveling body 2 via a revolving device 4. A working device 8 for performing excavation work or the like is provided at the front of the upper swing body 6. The work device 8 includes a boom 10 extending from the upper swing body 6 and an arm foot at the tip of the boom 10. An arm 14 connected via a pin 12 and a drilling bucket 18 as a work attachment connected to the tip of the arm 14 via a bucket foot pin 16. The boom 10, arm 14, and drilling bucket 18 are The boom cylinder 20, the arm cylinder 22 and the bucket cylinder 24 cause undulation and rotation thereof. The bucket cylinder 24 is connected to the excavation bucket 18 via a link 26.

  The mounting of the boom 10 and the boom cylinder 20 to the upper swing body 6 will be described in detail. A swing post 28 is disposed at the front portion of the upper swing body 6, and the swing post 28 is located in a horizontal plane with respect to the upper swing body 6. It is supported so that it can swing left and right. A base end portion of the boom 10 is pivotally supported on an upper portion of the swing post 28 via a boom foot pin 30, and a lower end of the boom cylinder 20 is supported on a front end of the swing post 28 via a connecting pin.

As shown in FIG. 2, a bracket 32 protrudes from the left side surface of the swing post 28, and the bracket 32 and the upper swing body 6 are connected to each other by a double-acting swing cylinder 34. Therefore, when the swing cylinder 34 is expanded and contracted, the working device 8 can swing left and right around the swing post 28.
In this embodiment, it should be noted that the swing cylinder 34 is arranged on the left side of the swing post 28 toward the front of the upper swing body 6 as is apparent from FIG.

FIG. 3 shows the swing post 28 in an enlarged manner.
The swing post 28 includes a pin hole 36 at the rear end portion on the upper swing body 6 side, and the pin hole 36 has an axis extending in the vertical direction. On the other hand, a pin hole (not shown) corresponding to the pin hole 36 is provided in the front portion of the upper swing body 6, and the pin hole 36 of the swing post 28 is aligned with this pin hole, By inserting the pivot pin 38, the swing post 28 is connected to the upper swing body 6 so as to be swingable around the pivot pin 38. The lower end of the pivot pin 38 is supported at the bottom of the pin hole.

The bracket 32 of the swing post 28 is formed with a pin hole 40 at the tip thereof, while the pin tip of the swing cylinder 34 is formed with a pin hole corresponding to the pin hole 40. Therefore, the swing cylinder 34 is connected to the bracket 32 by aligning these pin holes with each other and inserting the connecting pins 42 into these pin holes.
3 indicate the axis of the boom foot pin 30, the axis of the connecting pin that connects the lower end of the boom cylinder 20 to the swing post 28, and the longitudinal axis of the working device 8, respectively. .

With respect to the traveling of the lower traveling body 2, the turning of the upper revolving body 6 and the operation of the working device 8, these operations are performed by an operator seated on the driver's seat 44 on the upper revolving body 6, and are shown in FIG. As shown, an operation lever 46 and an operation pedal 48 are arranged in the vicinity of the driver seat 44.
1 and 2, reference numerals 50 and 52 denote a canopy and a soil discharging blade that cover the upper side of the driver's seat 44, respectively.

FIG. 4 shows a part of a hydraulic circuit provided in the above-described mini excavator, specifically, a part of the hydraulic circuit of the first embodiment related to the turning device 4 and the swing cylinder 34.
The hydraulic circuit includes a hydraulic source 54, which includes a main hydraulic pump 56 and a pilot pressure pump 58. These pumps 56 and 58 are driven by the engine 60 and can suck hydraulic oil from the hydraulic tank T and discharge the sucked hydraulic oil. The engine 60 is mounted on the upper swing body 6.

  A main hydraulic line 62 extends from the discharge port of the main hydraulic pump 56, and this main hydraulic line 62 passes through a control valve unit 64 to a swing hydraulic motor 66 of the swing device 4 via a pair of motor lines 68a and 68b. Further, the rod side pressure chamber 34a and the bottom side pressure chamber 34b of the swing cylinder 34 are connected via a pair of cylinder side pipes 70a and 70b as hydraulic paths.

  Specifically, the control valve unit 64 controls the drive direction of the swing hydraulic motor 66, that is, the swing direction control valve 72 that controls the swing direction of the upper swing base 6 and the expansion and contraction of the swing cylinder 34, that is, swing of the swing post 28. A swing direction control valve 74 is included. These directional control valves 72 and 74 are both pilot-type 6-port 3-position directional switching valves. When these directional control valves 72 and 74 are in the neutral switching position, the operation is supplied through the main hydraulic line 62. The oil is returned to the hydraulic tank T via the direction control valves 72 and 74 and the bleed-off path 76.

The control valve unit 64 includes a main relief valve 78 on the return line connecting the main hydraulic line 62 to the hydraulic tank T. The main relief valve 78 is the maximum discharge pressure of the main hydraulic pump 56, that is, The allowable maximum supply pressure Pr supplied to the swing hydraulic motor 66 and the swing cylinder 34 is set.
In the swivel device 4 shown in FIG. 4, reference numerals 80 and 82 denote a crossover relief valve for preventing overload of the motor pipe 68 and an adjustment cylinder for adjusting the urging force of the relief spring of the crossover relief valve, respectively. Show.

  On the other hand, the switching operation of the direction control valves 72 and 74 is performed by operation of the turning operation lever 46m and the swing operation pedal 48s among the operation lever 46 and the operation pedal 48 described above. As is clear from FIG. 4, both the turning operation lever 46m and the swing operation pedal 48s are combined with a pair of pilot valves 84 and 86. These pilot valves 84 and 86 have an input port, an output port and a return port. Have each. A pilot supply line 88 and a return line 90 extend from the input port and the return port of the pilot valves 84 and 86. The pilot supply line 88 is connected to the discharge port of the pilot pressure pump 58 described above, and the return pipe. The path 90 is connected to the hydraulic tank T. In FIG. 4, reference numerals 92 and 94 denote a relief line and a relief valve for the pilot pressure pump 58, respectively.

The output ports a and b of the pair of pilot valves 84 are connected to the corresponding input ports a and b of the turning direction control valve 72 via pilot transmission lines, and the output ports c and d of the pair of pilot valves 86 are These are connected to the corresponding input ports c and d of the swing direction control valve 74, respectively.
When the turning operation lever 46m is operated, the pilot valve 84 corresponding to this operation direction is opened, and the pressure of the hydraulic oil discharged from the pilot pressure pump 58, that is, the supplied pilot pressure is used as the operation pilot pressure (operation amount). Then, the output port (a or b) of the opened pilot valve 84 is supplied to the corresponding input port of the turning direction control valve 72, and the turning direction control valve 72 is switched from the neutral position to one switching position.

Therefore, the hydraulic oil discharged from the main hydraulic pump 56 is supplied to the swing hydraulic motor 66, and the swing hydraulic motor 66 is driven in one direction. As a result, the upper swing body 6 swings according to the operation direction of the swing operation lever 46m. To do. The hydraulic oil that has passed through the swing hydraulic motor 66 is returned to the hydraulic tank T via the swing direction control valve 72.
The pilot valve 84 outputs an operation pilot pressure having a magnitude corresponding to the operation amount of the turning operation lever 46m. Therefore, the valve opening when the turning direction control valve 72 is switched, that is, the turning speed of the upper turning body 6 by the turning hydraulic motor 66 is also controlled according to the operation amount of the turning operation lever 46m.

  On the other hand, when the swing operation pedal 48s is depressed, an operation pilot pressure having a magnitude corresponding to the depression amount is supplied from the pilot valve 86 corresponding to the depression direction to the corresponding input port of the oscillation direction control valve 74, and the oscillation is performed. The direction control valve 74 is switched from its neutral position to one switching position. Therefore, the hydraulic oil discharged from the main hydraulic pump 56 is supplied to one pressure chamber (34a or 34b) of the swing cylinder 34 through the swing direction control valve 74 and one cylinder side conduit 70, The hydraulic oil is returned to the hydraulic tank T from the other pressure chamber (34b or 34a) of the swing cylinder 34 through the other cylinder side pipe 70 and the swing direction control valve 74. As a result, the swing cylinder 34 is expanded or contracted according to the depression of the swing operation pedal 48s.

  As described above, when the swing cylinder 34 is expanded and contracted, the swing post 28, that is, the working device 8 is in a horizontal plane with the pivot pin 30 of the swing post 28 as the center with respect to the upper swing body 6 as shown in FIG. 5. Swing left and right at. FIG. 5A shows a state in which the swing cylinder 34 is contracted and the working device 8 is swung from the state shown in FIG. 2 to the left side of the upper swing body 6. In this case, the work of the mini excavator is performed. The device 8 is used for excavating the right gutter.

On the other hand, FIG. 5B shows a state in which the swing cylinder 34 is extended and the working device 8 is swung to the right side of the upper swing body 6 from the state shown in FIG. The device 8 is used for excavating the left gutter.
Further, as is apparent from FIG. 4, the cylinder side pipes 70a and 70b are provided with relief devices 96a and 96b, respectively. Since these relief devices 96a and 96b have the same structure, only the elements of one relief device 96 will be described below, and the elements of the other relief device 96 will be denoted by the same reference numerals, and the description thereof will be omitted. Omitted.

  The relief device 96 has a relief pipeline 98 that connects the cylinder side pipeline 70 and the return pipeline on the hydraulic tank T side, and a relief valve 100 is inserted in the relief pipeline 98. The relief valve 100 has a relief spring 102 that urges the valve body in one direction to determine the relief pressure of the relief valve 100, and a control pressure chamber 104 that is disposed on the opposite side of the relief spring 102. When the control pressure is supplied to the control pressure chamber 104, the control pressure applies an urging force opposite to the urging force of the relief spring 102 to the valve body, and reduces the relief pressure of the relief valve 100.

  Furthermore, the relief device 96 further includes a bypass conduit 106 that branches off from the relief conduit 98 and bypasses the relief valve 100, and a makeup valve 108 is inserted in the bypass conduit 106. The make-up valve 108 is a check valve that opens only toward the pressure chamber on the corresponding side of the swing cylinder 34. The make-up valve 108 is replenished with hydraulic oil to prevent the pressure chamber from becoming negative pressure, thereby generating cavitation. Stop.

  Control pressure lines 110a and 110b respectively extend from the control pressure chambers 104 of the relief devices 96a and 96b described above, and these control pressure lines 110a and 110b are branched from the pilot supply line 88 described above. A pressure reducing valve unit 112 is provided in the middle of the control pressure lines 110a and 110b. The pressure reducing valve unit 112 includes a pair of electromagnetic proportional pressure reducing valves 114a and 114b. These electromagnetic proportional pressure reducing valves 114 are 3-port 2-position electromagnetic pressure control valves, and are respectively inserted in the control pressure lines 110a and 110b.

  The electromagnetic proportional pressure reducing valve 114 is normally in the illustrated rest position. At the rest position, the corresponding control pressure line 110 is divided, and the portion on the control pressure chamber 104 side is connected to the hydraulic tank T through the return line 116. It is connected. When the command signal is supplied to the solenoid of the electromagnetic proportional pressure reducing valve 114, the electromagnetic proportional pressure reducing valve 114 is switched from the rest position to the operating position, and at this operating position, the control pressure line 110 is connected and the return line 16 is connected. Is closed.

  Therefore, when the electromagnetic proportional pressure reducing valve 114 is switched to the operating position, the pilot pressure pump 58 is connected to the control pressure chamber 104 of the corresponding relief device 96 via the electromagnetic proportional pressure reducing valve 114, so that the supplied pilot pressure is The pressure is reduced by the electromagnetic proportional pressure reducing valve 114 and supplied from the electromagnetic proportional pressure reducing valve 114 to the control pressure chamber 104 of the corresponding relief device 96 as a control pressure. Here, the magnitude of the control pressure is determined by the valve opening of the electromagnetic proportional pressure reducing valve 114, that is, the command signal to the solenoid.

As shown in FIG. 4, the solenoids of the electromagnetic proportional pressure reducing valves 114a and 114b are electrically connected to a controller (ECU) 118. The controller 118 is based on the operation direction and operation amount of the turning operation lever 46m described above. Thus, a command signal for the electromagnetic proportional pressure reducing valve 114 is generated, and the generated command signal is supplied to the solenoid of the corresponding electromagnetic proportional control valve 114.
Therefore, in this embodiment, in order to detect the operation direction and the operation amount of the turning operation lever 46m, the pair of pilot valves 84 in the turning operation lever 46m are assigned pressure sensors 120a and 120b on the output port side, respectively. These pressure sensors 120 detect the operation pilot pressure Pis when the turning operation lever 46m is operated, and transmit this sensor signal to the controller 118. Here, the pressure sensor 120 that outputs the sensor signal (operation pilot pressure Pis) indicates the operation direction of the turning operation lever 46m, and the magnitude of the sensor signal (value of the operation pilot pressure Pis) is the operation of the turning operation lever 46m. Indicates the amount.

Specifically, the controller 118 calculates a command signal _SD to the electromagnetic proportional pressure reducing valve 114 from the following equation based on the operation pilot pressure Pis.
S _D = G _IS / Pis
G _IS is a gain set based on the gain map of FIG. 6 in which the controller 118 is built in the operation pilot pressure Pis. Rise Specifically, gain map of FIG. 6, when the operation pilot pressure Pis is below a lower limit value PISC, the gain G _IS is 0, the operation pilot pressure Pis exceeds the lower limit PISC, toward the upper limit Pimax Accordingly, the gain _GIS is gradually increased from zero.

Therefore, as long as the operation pilot pressure Pis does not exceed the lower limit PISC, the gain G _IS is maintained at 0, never command signal S _D to the solenoid proportional pressure reducing valve 114 is supplied from the controller 118, electromagnetic proportional The pressure reducing valve 114 is held in the illustrated rest position.
As a result, since the electromagnetic proportional pressure reducing valve 114 connects the control pressure chamber 104 of the corresponding relief valve 100 to the hydraulic tank T, the relief pressure Ps of the relief valve 100 is determined by the biasing force of its own relief spring 102. The

However, when the operation pilot pressure Pis exceeds the lower limit PISC, the gain G _IS its value is gradually increased, the controller 118 generates a command signal S _D which increases with increase of the operation pilot pressure Pis, this The command signal _SD is supplied to the corresponding electromagnetic proportional pressure reducing valve 114. Therefore, the electromagnetic proportional pressure reducing valve 114 is switched from the illustrated rest position to the operating position, and the pilot pressure supplied from the pilot pressure pump 58 is reduced by the electromagnetic proportional pressure reducing valve 114, and the valve opening degree at the operating position is reduced. Accordingly, the control pressure Pix is supplied from the electromagnetic proportional pressure reducing valve 114 to the control pressure chamber 104 of the corresponding relief valve 100.

Since the control pressure Pix in the control pressure chamber 104 acts on the valve body in a direction opposite to the urging force of the relief spring 102 in the relief valve 100, the relief pressure Ps of the relief valve 100 is reduced.
Here, as the operation pilot pressure Pis increases beyond the lower limit Pisc, the command signal S _D to the electromagnetic proportional pressure reducing valve 114, that is, the control pressure supplied from the electromagnetic proportional pressure reducing valve 114 to the control pressure chamber 104. Pix also increases, and the control pressure Pix and the relief pressure Ps of the relief valve 100 have the relationship shown in FIG. 7. This FIG. 7 shows that the relief pressure Ps can be arbitrarily set based on the control pressure Pix. Show.

In FIG. 7, Psmax indicates the maximum relief pressure of the relief valve 100 determined only by the urging force of the relief spring 102, and Psmin is when the maximum control pressure Pixmax is supplied from the electromagnetic proportional pressure reducing valve 114 to the control pressure chamber 104. The minimum relief pressure of the relief valve 100 is shown.
Here, it should be noted that the maximum relief pressure Psmax is lower than the maximum discharge pressure Pr of the main hydraulic pump 56 determined by the above-described main relief valve 78 (see FIG. 4).

Furthermore, in the case of the present embodiment, the relief pressure Ps of the relief valve 100 is set in consideration of not only the operation pilot pressure Pis but also the working status such as the operating posture of the swing post 28 and the working position of the excavating bucket 18. Specifically, the above-described gain _GIS is corrected according to these operating postures and work conditions.
First, the operation posture of the swing post 28 and the work status of the excavation bucket 18 will be described below.

  As shown in FIG. 4, in addition to the pressure sensor 120 described above, a stroke sensor 122, a boom angle sensor 124, an arm angle sensor 126, and a bucket angle sensor 128 are electrically connected to the controller 118. The sensor 122 is, for example, a wire pull-out type length meter, and detects the expansion / contraction stroke of the swing cylinder 34, that is, the expansion / contraction length thereof, and transmits this sensor signal to the controller 118.

Upon receiving the sensor signal from the stroke sensor 122, that is, the expansion / contraction stroke of the swing cylinder 34, the controller 118 calculates the swing post angle θ of the swing cylinder 34 shown in FIG. 3 based on the expansion / contraction stroke.
Here, the swing post angle θ is the inclination angle of the swing cylinder 34 with respect to the swing post 28, that is, the axis of the swing cylinder 34 in FIG. 3 is represented by the reference symbol X, and the pivot pin 38 on the swing post 28. When the line segment connecting between the axis of the shaft and the axis of the connecting pin 42 that connects the swing post 28 and the swing cylinder 34 is represented by the reference symbol Y, it represents the internal angle formed by the axis X and the segment Y, On the other hand, since the distance between the base end of the swing cylinder 34 and the pivot pin 38 and the center-to-axis distance R that defines the line segment Y are both known, if the expansion / contraction stroke of the swing cylinder 34 is obtained, The swing post angle θ can be obtained by calculation.

  Such a swing post angle θ represents the operating posture of the swing cylinder 34, but in this embodiment, a separation distance Lc shown in FIG. 3 is used instead of the swing post angle θ. The separation distance Lc is represented by the distance from the point of application of the thrust Fc generated by the swing cylinder 34 to the swing center of the swing post 28 (the axis of the pivot pin 38). Can be obtained from

Lc = R · sinθ
On the other hand, the angle sensors 124, 126, and 128 are attached to the boom foot pin 30, the arm foot pin 12, and the bucket foot pin 16 of the boom 10 in the working device 8 described above, respectively, and the boom 10, arm 14, and excavation bucket 18. The undulation and the rotation angle are detected, and these sensor signals are transmitted to the controller 118.

  Since the lengths of the boom 10 and the arm 14 and the sizes of the excavation bucket 18 and the upper swing body 6 are known, the controller 118 detects sensor signals from the above-described sensors 124, 126, and 128, that is, their undulations. Based on the angle and the rotation angle, the working position of the excavation bucket 18, that is, the separation distance Lb (see FIG. 1) from the turning center of the upper swing body 6 to the tip of the excavation bucket 18 can be obtained by calculation.

Distance Lc as described above, Lb are used the gain _{G LC,} the calculation of _{G LB,} these gain _{G LC, G LB} is used for the correction of the command signal _{S D.} That is, in the case of the present embodiment, the command signal _SD is actually calculated from the following equation.
S _D = G _IS / G _LC / G _LB / Pis
In order to calculate the gains G _LC and G _LB , the controller 118 further includes a gain map shown in FIGS. Gain map of FIG. 8, when the distance Lc is below the lower limit value Lcmin, according to the gain G _LC and a minimum value, becomes longer toward the upper limit Lcmax distance Lc is beyond the lower limit Lcmin, the gain G _LC Is gradually increased from its minimum value.

Therefore, if the separation distance Lc is increased and the gain G _LC is increased, the command signal _SD is also increased, so that the control pressure Pix is increased, and as a result, the relief pressure Ps of the relief valve 100 is decreased. .
On the other hand, according to the gain map of FIG. 9, if the distance Lb is less than the lower limit value Lbmin, the gain G _LB to the maximum value, becomes longer toward the upper limit Lbmax distance Lb is beyond the lower limit Lbmin, the gain G It has a characteristic of gradually reducing _LB from its maximum value.

Therefore, in this case, if the separation distance Lb is increased and the gain G _LB is decreased, the command signal SD is also decreased, so that the control pressure Pix is decreased. As a result, the relief pressure of the relief valve 100 is decreased. Ps increases.
The functions of _{GIS ,} G _LC , and G _LB described above are also apparent from the graph of FIG. 10, and FIG. 10 shows the relationship between the operating pilot pressure Pis and the corresponding relief pressure Ps of the relief valve 100.

  As described above, when the operation pilot pressure Pis is equal to or lower than the lower limit Pisc, the relief pressure Ps is maintained at the maximum relief pressure Psmax determined by the urging force of the relief spring 102. When the operation pilot pressure Pis is between the lower limit value Pisc and the upper limit value Pismax, the relief pressure Ps is reduced as the operation pilot pressure Pis increases, and the operation pilot pressure Pis is the same. The relief pressure Ps increases as the separation distance Lb tends to increase or the separation distance Lc decreases. Conversely, as the separation distance Lb tends to decrease or the separation distance Lc increases, the relief pressure Ps increases. The relief pressure Ps decreases.

FIG. 11 shows the above-described relief pressure control routine executed by the controller 118 with respect to the relief pressure Ps of the relief valve 100 in the above-described relief devices 96a and 96b, that is, a control method of the swing cylinder 34.
Here, the relief pressure control routine forms part of the main routine executed by the controller 118, and is executed repeatedly at predetermined control cycles.

  First, the controller 118 reads sensor signals from the pressure sensors 120a and 120b, the stroke sensor 122, the boom angle sensor 124, the arm angle sensor 126, and the bucket angle sensor 128, respectively, (step S1). If there is a sensor signal, the operation pilot pressure Pis is calculated from this sensor signal (step S2).

Then, it is determined whether or not the operating pilot pressure Pis is higher than the lower limit Pisc (step S3). If the determination result here is false (No), the controller 118 exits from this control routine and returns to the main routine. Then, another control routine (not shown) is executed.
Therefore, as long as the determination result of step S3 is maintained to be false, the relief pressure control routine of FIG. 11 is only executed by repeating steps S1 to S3 as long as the operating pilot pressure Pis does not exceed the lower limit Pisc. Instead, the relief pressure Ps of the relief valve 100 is maintained at the maximum relief pressure Psmax described above.

However, if the determination result in step S3 becomes true (Yes), the controller 118 calculates the gain Gis based on the operation pilot pressure Pis (step S4), and the expansion / contraction stroke of the swing cylinder 34 detected by the stroke sensor 122. The swing post angle θ is calculated based on (Step S5). Thereafter, the controller 118 calculates the distance Lc on the basis of the swing post angle theta (step S6), and calculate and obtain the gain _{G LC} from distance Lc (step S7).

Further, the controller 118 calculates the undulation angle of the boom 10 and the rotation angles of the arm 14 and the excavation bucket 18 based on the sensor signals from the angle sensors 124, 126, and 128 described above (step S8). The aforementioned separation distance Lb is calculated from the undulation angle and the rotation angle (step S9), and the gain G _LB is calculated based on the separation distance Lb (step S10).

In the manner described above, the operation pilot pressure Pis, the gain _{G IS,} G _LC, when _{G LB} are respectively determined, the controller 118, they Pis, calculates the gain _{G IS,} G _LC, command signal _{S D} from _{G LB} The command signal _SD is supplied to the solenoid of the electromagnetic proportional pressure reducing valve 114 on the corresponding side of the electromagnetic proportional pressure reducing valves 114a and 114b, and the electromagnetic proportional pressure reducing valve 114 is switched from the rest position to the operating position.

Accordingly, the electromagnetic proportional pressure reducing valve 114 that has received the command signal _SD supplies the control pressure Pix to the relief valve 100 of the target relief device 96 that forms a set, and the relief valve 100 uses the control pressure Pix ( The pressure is reduced to the relief pressure Ps determined by the command signal S _D ).
Here, selection of the target relief device 96 on the side where the relief pressure Ps is decreased upon receiving the command signal _SD will be described in detail.

  The target relief device 96 is determined based on the turning direction of the upper turning body 6, that is, the turning direction of the turning operation lever 46 m in addition to the arrangement of the swing cylinder 34 with respect to the upper turning body 6. Specifically, as in this embodiment, the swing cylinder 34 is disposed on the left side with respect to the upper swing body 6 as viewed in FIG. 2, and now the upper swing body 6 is counterclockwise CC as viewed in FIG. Of the relief devices 96a and 96b, the relief device 96a on the side that weakens the rigidity in the extending direction of the swing cylinder 34, that is, the relief valve 100 connected to the rod side pressure chamber 34a of the swing cylinder 34 is provided. The relief device 96a (see FIG. 4) is selected as the target relief device 96.

On the other hand, when the upper swing body 6 is swung clockwise C as viewed in FIG. 2, the relief device 96b on the side that weakens the rigidity in the contraction direction of the swing cylinder 34, that is, the bottom side pressure chamber 34b of the swing cylinder 34. The relief device 96 b having the relief valve 100 connected to is selected as the target relief device 96.
Unlike the present embodiment, when the swing cylinder 34 is arranged on the right side with respect to the upper swing body 6, the target relief device 96 is the reverse of the above case.

Next, the operation of the above-described relief devices 96a and 96b will be described below.
For the work of the mini excavator, not only excavation work for moving the excavation bucket 18 of the work device 8 up and down, but also loading work for loading surplus sand and sand etc. accompanying excavation from the excavation bucket 18 onto the dump truck, The leveling work for leveling by reciprocating left and right is included, and these loading work and leveling work are performed by reciprocating the upper swing body 6 together with the work device 8.

Therefore, there is a case where the excavation bucket 18 collides with an unexpected obstacle around the upper turning body 6 during the turning, and at this time, the torsional moment Tb and the bending moment applied to the base end portion of the boom 10 in the work device 8. Mb is represented by the following formula, respectively.
Tb = F ′ · L1 (1)
Mb = F ′ · L2 (2)
F ′ represents a turning impact force applied to the excavation bucket 18 at the time of a collision, and L1 and L2 represent distances from the excavation bucket 18 to the base end portion of the boom 10 (see FIG. 1).

  More specifically, the turning torque T of the upper turning body 6 generates a tangential force F in the turning direction at the base end portion of the boom 10, and when the point of action of this tangential force F is indicated by Z in FIG. The distance L1 indicates the distance from the action point Z to the excavation bucket 18 in the direction perpendicular to the longitudinal direction of the boom 10, and the distance L2 indicates the distance from the action point Z to the excavation bucket 18 in the longitudinal direction of the boom 10. Indicates.

Here, the tangential force F, the turning impact force F ′, and the turning torque T have a relationship represented by the following equation.
F = T / Lb (3)
F ′ = α · T / Lb (4)
T = K · P · q (5)
α represents an impact coefficient, K represents a constant, P represents a pressure difference before and after the swing hydraulic motor 66, and q represents a discharge flow rate (push-out volume) per rotation of the swing hydraulic motor 66.

On the other hand, even if the swing impact force F ′ is applied to the excavation bucket 18, the following equation needs to be satisfied in order for the swing post 28 to be held at the swing position.
F ′ · L3 ≦ Fc · Lc (6)
Fc = Px · A (7)
L3 represents the distance from the swing center of the swing post 28 (the axis of the pivot pin 38) to the point of action of the swing impact force F ′, and Px and A represent the internal pressure of the swing cylinder 34 and its pressure receiving area. .

Here, as is clear from FIG. 12, the separation distance Lc varies greatly depending on the posture of the working device 8 with respect to the upper swing body 6, and thus the above (6) regardless of the posture of the working device 8. In order to satisfy the equation, it is necessary to ensure a large internal pressure Px of the swing cylinder 34.
For this reason, conventionally, the internal pressure Px of the swing cylinder 34 is increased to the maximum discharge pressure Pr of the main hydraulic pump 56 in the hydraulic circuit. Therefore, the conventional working device 8 has a large thrust Fc generated by the swing cylinder 34. The rigidity that can withstand is required. Therefore, as described above, in the working device 8, its excessive scale-up and weight increase are caused, and the manufacturing cost cannot be reduced.

  However, in this embodiment, the internal pressure Px of the swing cylinder 34, that is, the relief pressure Ps is not uniquely determined. That is, as is apparent from the above description, when the upper swing body 6 is not swung or is swung, the relief pressure Ps is reduced when the swing speed is low. The maximum relief pressure Psmax determined by the spring 102 is maintained, and this maximum relief pressure Psmax is lower than the maximum discharge pressure Pr of the main hydraulic pump 56.

Moreover, during the turning of the upper swing body 6, the relief pressure Ps is based on the operation amount of the swing operation lever 46 m, that is, the swing speed of the upper swing body 6, the operating posture of the swing cylinder 34, and the working position of the excavation bucket 18. Thus, the maximum relief pressure Psmax is decreased.
Therefore, the thrust Fc of the swing cylinder 34 is greatly reduced, the rigidity required for the work device 8 can be lowered, and the above-described problems that the work device 8 had can be solved.

  On the other hand, when the swing impact force F ′ applied to the excavation bucket 18 is so large that the above expression (6) is not satisfied, the swing cylinder 34 extends or contracts, and the swing post 28 is passively swung. Such swinging of the swing post 28 absorbs the turning impact force F ', so that no overload is applied to the work device 8 and damage to the work device 8 can be reliably prevented.

  When the swing cylinder 34 is extended or contracted due to the turning impact force F ′ described above in a state where the swing direction control valve 74 that controls expansion and contraction of the swing cylinder 34 is in the neutral position, The pressure oil (34a or 34b) on the negative pressure side is replenished with hydraulic oil through the corresponding makeup valve 108 (see FIG. 4), and cavitation does not occur in the pressure chamber.

More specifically regarding the swing impact force F ′, as described above, the control of the relief pressure Ps includes not only the swing speed (gain _GIS ) of the upper swing body 6 but also the operating posture of the swing cylinder 34 (separation distance Lc, The gain G _LC ) and the working position of the excavation bucket 18 (separation distance Lb, gain G _LB ) are taken into consideration, so that even if the excavation bucket 18 collides with an obstacle, The relief pressure Ps can be set by estimating the strength of the applied torsional moment Tb and bending moment Mb (see FIG. 10), and the turning impact force F ′ received by the excavation bucket 18 can be effectively reduced.

The present invention is not limited to the first embodiment described above, and various modifications are possible.
Hereinafter, the control devices and control methods of the second to fourth embodiments will be described with reference to FIGS. 13 to 15. In describing the second to fourth embodiments, elements exhibiting the same functions as those of the first embodiment or the embodiments already described are denoted by the same reference numerals, and description thereof is omitted. To do.

FIG. 13 shows a hydraulic circuit of the second embodiment.
In the case of the second embodiment, the control pressure chamber 104 of the relief valve 100 in the relief devices 96a and 96b is connected to the output ports a and b of the pilot valve 84 on the corresponding side of the turning operation lever 46m via connection paths 130a and 130b. It is connected. Therefore, when the turning operation lever 46m is operated, the operation pilot pressure is applied from the output port a or b of the pilot valve 84 corresponding to the operation direction to the corresponding input port a or b of the turning direction control valve 72. While Pis is supplied, the operation pilot pressure Pis is also supplied to the control pressure chamber 104 of the target relief device 96 (relief valve 100) described above. Therefore, here, the operation pilot pressure Pis also works as the control pressure Pix, and as a result, the relief pressure Ps of the relief valve 100 in the target relief device 96 is reduced according to the operation of the turning operation lever 46m.

According to the second embodiment described above, the relief pressure Ps can be controlled without using the various sensors and controller 118 used in the first embodiment. Further, since the operation direction of the turning operation lever 46m can be mechanically associated with the target relief device 96 (the control pressure chamber 104 of the relief valve 100), no control error occurs.
FIG. 14 shows a hydraulic circuit of the third embodiment.

The hydraulic circuit of the third embodiment includes connection paths 130a and 130b similar to those of the second embodiment, and the pressure reducing valve unit 112 of the first embodiment, that is, its electromagnetic proportional pressure reducing valve is connected to these connection paths 130a and 130b. 114a and 114b are inserted, respectively, and the operation pilot pressure Pis from the pilot valve 84 is used as the original pressure of the electromagnetic proportional control valves 114a and 114b.
According to the third embodiment, the operation pilot pressure Pis can be used as the source pressure of the control pressure Pix to be supplied to the control pressure chamber 104 of the relief devices 96a and 96b (relief valve 100), and the control pressure Pix is the first pressure. As in the case of the embodiment, control is possible using the gains G _IS , G _LC , and G _LB described above.

FIG. 15 shows a double-armed turning work machine of the fourth embodiment.
In the case of the fourth embodiment, the turning work machine includes work devices 8 _L and 8 _R on the left and right of the upper turning body 6, respectively. These working devices 8 _L and 8 _R have the same structure as the working device 8 described above, but have dismantling grapples 132 that can be opened and closed instead of the excavation buckets 18 at their tips. The dismantling grapple 132 is opened and closed by a grapple cylinder (not shown). In FIG. 15, reference numeral 134 indicates a cab.

As apparent from FIG. 15B, the working devices 8 _L and 8 _R are provided with swing cylinders 34 _L and 34 _R , respectively, and the relief pressure Ps of the swing cylinders 34 _L and 34 _R is the same as that in the first embodiment. It is controlled in the same way as the case.
In the case of the above-described double-arm type turning work machine, each of the work devices 8 _L and 8 _R is lighter than the single-arm type turning work machine. Due to work mode. However, the turning device 4 is required to have a turning output determined based on the inertial force of the upper turning body 6, and this turning output is equivalent to that of a single-arm type work machine.

Therefore, by applying the control device and the control method of the present invention to the work devices 8 _L and 8 _{R of} the double-armed turning work machine, the rigidity required for the individual work devices 8 _L and 8 _R can be reduced. The load can be reduced.
On the other hand, the swing cylinders 34 _L and 34 _R of the working devices 8 _L and 8 _R of the double-armed swivel working machine are expanded and contracted, and the disassembly nibbler 132 of the working devices 8 _L and 8 _R is swung left and right. A work form is required. Since such work forms without turning operation of the upper frame 6, never swing cylinder 34 _L, 34 _R of the relief pressure Ps is reduced undesirably, effective swing cylinder 34 _L, 34 _R Telescopic movement is guaranteed.

  Further, in the case of the first embodiment, the turning operation lever 46m can be replaced with an electric lever, and the electric lever directly transmits an electric operation signal indicating the operation direction and the operation amount to the controller 118.

It is the side view which showed the mini excavator as a turning working machine. It is a top view of the mini excavator of FIG. It is the figure which expanded and showed a part of mini excavator of FIG. It is a hydraulic circuit diagram including the control device of the first embodiment. 2A and 2B show a working form of the mini excavator of FIG. 2, in which FIG. 2A shows a state in which the working device swings to the left with respect to the upper swing body, and FIG. Each state is shown. It is a graph showing a gain map to determine the gain G _IS. It is the graph which showed the relationship between control pressure and relief pressure. It is the graph which showed the gain map which calculates _| requires gain GLC. It is the graph which showed the gain map which calculates _| requires gain GLB. It is the graph which showed the relationship between the operation pilot pressure and the relief pressure. It is the flowchart which showed the relief pressure control routine. It shows that the operating posture of the swing cylinder changes depending on the swinging form of the working device, (a) is the operating posture in which the swing cylinder is contracted from the normal state, (b) is the normal operating posture of the swing cylinder, (c) is The operation postures in which the swing cylinder is extended from the normal state are shown. It is a hydraulic circuit diagram containing the control apparatus of 2nd Example. It is a hydraulic circuit including the control device of the third embodiment. FIG. 6 shows another embodiment of the turning work machine to which the present invention is applied, wherein (a) is a side view showing the double-arm turning work machine, and (b) is a plan view of the double-arm turning work machine.

Explanation of symbols

2 Lower traveling body 4 Turning device 6 Upper turning body 8 Working device 18 Excavation bucket (working attachment)
28 Swing post 34 Swing cylinder 34a Rod side pressure chamber 34b Bottom side pressure chamber 46m Turning operation lever 58 Pilot pressure pump (pilot pressure source)
84 Pilot valve 96a, 96b Relief device 100 Relief valve 102 Relief spring 104 Control pressure chamber 114a, 114b Electromagnetic proportional pressure reducing valve (pressure reducing valve)
118 Controller 120a, 120b Pressure sensor 122 Stroke sensor (detector)
124 Boom angle sensor (detector)
126 Arm angle sensor (detector)
128 Bucket angle sensor (detector)

Claims (6)

A lower traveling body, an upper revolving body that is provided on the lower traveling body so as to be pivotable, and that is swung by an operation amount from an operation lever, and is supported by a front portion of the upper revolving body, and can swing left and right within a horizontal plane. A swing post, and a double-acting swing that is arranged on either the left or right of the upper swing body centered on the swing post and connects the upper swing body and the swing post to swing the swing post In a swivel working machine comprising a cylinder and a work device having a work attachment supported by the swing post so as to be raised and lowered and movable in the front-rear and up-down directions,
A pair of relief valves that are provided in a hydraulic path for supplying and discharging hydraulic oil to and from the swing cylinder, and respectively determine relief pressures of both pressure chambers of the swing cylinder;
A reduction means for reducing a relief pressure of a relief valve selected by an arrangement of the swing cylinder and a turning direction of the upper swing body among the pair of relief valves according to an operation amount of the operation lever; A swing cylinder control device for a swing work machine. Each relief valve includes a relief spring that urges the valve body in one direction, and a control pressure chamber that receives supply of control pressure that urges the valve body in a direction opposite to the urging direction of the relief spring,
The said reduction means supplies the control pressure according to the operation amount of the said operation lever to the said control pressure chamber of the said selected relief valve, The relief pressure of the said selected relief valve is reduced. 2. A swing cylinder control device for a swing working machine according to 1. The turning work machine is
A pilot pressure source;
A pair of pilot valves connected to the pilot pressure source and operated by the operation lever, and the corresponding pilot valve is operated according to the operation direction and the operation amount of the operation lever to remove the original pressure of the pilot pressure source. A pair of pilot valves for generating an operation pilot pressure as the operation amount; and
A swirling device for swirling the upper swing body in a predetermined direction based on the operation pilot pressure from the pilot valve;
The reducing means is
A pressure reducing valve provided between the pilot pressure source and the control pressure chamber of the relief valve,
The swing cylinder control device for a swing work machine according to claim 2, wherein the pressure reducing valve on the selected relief valve side is operated based on the operation pilot pressure from each pilot valve. The reducing means further includes a detector for detecting a work situation including an operation posture of the swing cylinder and a work position of the work attachment;
The swing cylinder control device for a swing work machine according to claim 3, wherein the operation of the pressure reducing valve is corrected based on the work situation detected by the detector.   The reduction means includes a connection path that connects the pilot valve and the control pressure chamber of the relief valve, respectively, and causes the operation pilot pressure from the pilot valve to directly act on the control chamber of the relief valve. The swing cylinder control device for a swing working machine according to claim 3 or 4. The reducing means is
The operation pilot pressure from the pilot valve is used as the original pressure of the pressure reducing valve, including a pressure reducing valve that connects the pilot valve and the control pressure chamber of the relief valve, respectively. 5. A swing cylinder control device for a swing work machine according to 4.

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