JP2007106564A - Cab lifting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cab lifting device capable of preventing generation of a shock when a cab lifting cylinder for lifting the cab is suddenly stopped at its stroke end. <P>SOLUTION: When the cab lifting cylinder 32 is stretched and arrival at the neighborhood to the stroke end is detected by a proximity switch 84, pressure-reduction function of a pressure-reduction valve 81 is acted and a pilot secondary pressure output from a solenoid proportion valve 73 to a head side pilot line 76 is automatically pressure-reduction-controlled. Thereby, since a control valve 64 is returned to a neutral position, the cab lifting cylinder 32 can be speed-reduced immediately before it arrives at the stroke end by reducing an operation flow rate fed to the cab lifting cylinder 32 and impact at the moment when the cab lifting cylinder 32 arrives at the stroke end can be relaxed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a cab elevating device that elevates a cab relative to a machine body of a work machine.

  In order to obtain a high eye point as required, the cab can be raised and lowered to the eye point that suits the work with a working machine that secures a high eye point with a fixed high eye point cab or a hydraulic carburetor There is a work machine.

As a hydraulic carburetor, an X-type link mechanism in which two sets of links or cab elevating cylinders are configured in an X shape with respect to the vehicle body, or a link mechanism configured so that the upper link and the lower link are kept parallel; Some cab lift cylinders are provided so that the cab can be lifted (see, for example, Patent Documents 1 and 2).
JP 2000-335883 A (page 4-6, FIG. 1-6) Japanese Patent Laid-Open No. 2002-178756 (page 4, FIG. 1-2)

  In a work machine that can raise and lower the cab to obtain such an eye point as needed, when the cab is raised to the highest position, for example, when the highest position is reached by a sudden stop at the stroke end of the cab lifting cylinder Shock occurs, and the cab shakes greatly.

  On the other hand, if the rising speed of the cab is reduced, shaking can be suppressed, but there is a problem that the reduction in speed leads to a decrease in operability.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a cab elevating device that can prevent occurrence of shock due to a sudden stop at the stroke end of a cab elevating cylinder that elevates or lowers the cab.

  According to a first aspect of the present invention, there is provided a cab elevating device for driving a cab, which is movable up and down via a link mechanism, to a machine body of a work machine using a cab elevating cylinder. And a pilot operated control valve that controls the expansion and contraction of the cab elevating cylinder, and a pressure reducing valve that is interposed in the pilot line of the control valve and reduces the pilot pressure to the control valve by a detection signal from the sensor. It is a cab lifting device.

  According to a second aspect of the present invention, the sensor in the cab elevating device according to the first aspect is a proximity switch that detects the operation of the link mechanism and detects that the cab elevating cylinder is located near the stroke end. .

  According to a third aspect of the present invention, the sensor in the cab elevating device according to the first or second aspect detects that the cab elevating cylinder is located in the vicinity of the stroke end on the expansion side and the contraction side.

  According to a fourth aspect of the present invention, in the cab elevating device according to the third aspect, the cab elevating device includes an operation direction detecting means for detecting an operation direction in the expansion / contraction operation of the cab elevating cylinder.

  According to a fifth aspect of the present invention, the pressure reducing valve in the cab elevating device according to any one of the first to fourth aspects is a proportional pressure reducing valve that increases the pressure reduction as the cab elevating cylinder approaches the stroke end.

  According to the first aspect of the present invention, the sensor detects that the cab elevating cylinder is located near the stroke end, and the pilot pressure to the control valve is reduced by the pressure reducing valve. Since sudden stop can be prevented, it can prevent shaking when the cab is stopped.

  According to the second aspect of the invention, the proximity switch that detects the operation of the link mechanism can easily detect that the cab elevating cylinder is located near the stroke end.

  According to the third aspect of the present invention, the sensor operates when the cab elevating cylinder is located near the stroke end on the expansion side and the contraction side, so that the end shock when the cab rises to the uppermost position and the lowering to the lowermost position. Both end shocks can be reduced.

  According to the fourth aspect of the present invention, the end shock at the time of operation stop and operation start (at the time of ascending stop, at the start of ascending, at the time of descending stop, at the time of starting to descend) by the motion direction detecting means by the motion direction detecting means Can be reduced.

  According to the fifth aspect of the present invention, the end shock in the expansion / contraction operation of the cab elevating cylinder can be smoothly reduced by the proportional pressure reducing valve.

  Hereinafter, the present invention will be described in detail with reference to one embodiment shown in FIGS. 1 to 4 and another embodiment shown in FIGS.

  FIG. 3 shows a work machine 10, in which a work device 12 is mounted on a machine body 11, and a cab 13 is provided on the machine body 11 so as to be movable up and down on the side of the work device 12, and between the machine body 11 and the cab 13. Is provided with a cab elevating device 14 for elevating the cab 13. In the airframe 11, an upper revolving body 17 is turnably provided on a lower traveling body 16 to which a crawler belt 15 is attached.

  The work device 12 includes a pivot frame 21 of the upper swing body 17 and a base end of a boom 22 pivotally supported by the pivot frame 21. A boom cylinder 23 for pivoting the boom is provided between the pivot frame 21 and the boom 22. The base end of the arm 24 is pivotally supported at the tip of the arm 22, and an arm cylinder 25 for arm rotation is provided between the boom 22 and the arm 24, and the attachment used for disassembly work etc. at the tip of the arm 24 26 is pivotally supported. As the attachment, a magnet or a fork is also used.

  As shown in FIG. 4, the cab elevating device 14 includes a link mechanism 31 that keeps the cab 13 in a predetermined posture, and a cab elevating cylinder 32 that drives the cab 13 up and down.

  The link mechanism 31 includes a support tower 33 erected on the upper swing body 17 of the airframe 11, an L-shaped link connection 34 integrally provided at the lower part of the cab 13, and an upper part of the support tower 33. An upper link 39 that is pivotally connected by pins 35, 36, 37, and 38 and is vertically rotated by a cab elevating cylinder 32 so as to be always kept parallel to the rear portion of the link connecting portion 34, and And a lower link 40.

  The base end of the cab elevating cylinder 32 is pivotally supported by a pin fitted to a bearing portion (not shown) integrally attached to the lower part of the support tower 33, and the piston rod of the cab elevating cylinder 32 is supported. The tip is connected to a connecting member (not shown) between the upper links 39, 39 by a pin.

  The support tower 33 is a box structure having an upper half 43 bulging rearward from the lower half 44 and having an opening on the front side. The cab 13 is attached to a side plate on one side of the support tower 33. A boss portion having a pin insertion hole 52 into which a lock pin 51 that is aligned with the pin insertion hole 47 (FIG. 3) of the lower link 40 and locks the fall of the cab 13 is inserted at a maintenance position slightly raised from the body 11 53 and a boss portion having a pin insertion hole 54 into which the lock pin 51 is inserted by being aligned with the pin insertion hole 47 of the lower link 40 at the lowest lowered position located below this, that is, the transport position during machine transportation 55 is provided.

  As shown in FIG. 4, the upper link 39 of the link mechanism 31 is provided with a boss portion 57 having a pin storage hole 56. The boss portion 57 has a pin insertion hole 52 at the maintenance position and a pin insertion hole 54 at the transport position. When it is not necessary to insert the lock pin 51, the lock pin 51 is stored in the pin storage hole 56 of the upper link 39. In addition, a stopper 58 protruding obliquely downward is provided at each tip of the lower link 40, and the stopper 58 is locked by the support tower 33 at the transport position.

  FIG. 1 shows a fluid pressure circuit 61 that controls the raising / lowering of the cab 13 by extending and retracting the cab raising / lowering cylinder 32 by an operation in the cab 13, and a main pump 63 driven by an in-vehicle engine 62 mounted on the upper swing body 17. The discharge line is connected to the supply port of the pilot-operated control valve 64, the tank line connected to the tank 65 is connected to the drain port of the control valve 64, and the two output ports of the control valve 64 are connected to the head. The side line 66 and the rod side line 67 are connected to the head side chamber 32h and the rod side chamber 32r of the cab elevating cylinder 32.

  Further, a sliding input device 72 such as a modulation switch is provided at the head portion of the joystick lever 71 that pilot-controls each actuator of the work device 12 by a pilot signal that is manually operated by an operator in the cab 13 and converted into electro-oil. The sliding input device 72 is connected to an electromagnetic part 74 of an electromagnetic proportional valve 73.

  This electromagnetic proportional valve 73 converts the pilot primary pressure discharged from the pilot pump 75 into a pilot secondary pressure in accordance with the electrical signal output from the slide type input device 72. Two output ports are connected to two pilot operation portions of the control valve 64 via a head side pilot line 76 and a rod side pilot line 77. The cab lifting speed is set by the sliding amount of the sliding input device 72.

  An electromagnetically operated pressure reducing valve 81 is provided at least in the head side pilot line 76, and an electromagnetic portion 82 of the pressure reducing valve 81 is connected to a proximity switch 84 as a stroke end sensor via a harness 83. The proximity switch 84 detects directly or indirectly through the link mechanism 31 that the cab elevating cylinder 32 has reached at least the vicinity of the extension stroke end.

  When the proximity switch 84 detects that the cab elevating cylinder 32 has reached the vicinity of the stroke end, the pressure reducing function of the pressure reducing valve 81 is activated, and the pilot secondary pressure output from the electromagnetic proportional valve 73 to the head side pilot line 76. Is automatically reduced and the control valve 64 attempts to return to the neutral position, that is, the amount of shift of the spool of the control valve 64 is reduced, so that the operating flow rate supplied to the cab elevating cylinder 32 is reduced. The cab elevating cylinder 32 is sufficiently decelerated immediately before reaching the stroke end.

  In this fluid pressure circuit 61, an emergency lowering valve for emergency lowering the cab 13 by manual operation on the airframe 11 side into a drain line 85 branched from the head side line 66 of the cab lifting cylinder 32 and led to the tank 65 86 is provided.

  As shown in FIG. 4, the emergency lowering valve 86 is located in the body position that can be operated via the lever 87 with one hand of the operator, that is, the right hand, on the side of the body 11 and in the vicinity of the support tower 33. Has been placed. For example, the emergency lowering valve 86 is installed in a filter chamber 89 that houses a filter 88 provided on the intake side of the in-vehicle engine 62, and a side door 90 is provided in the filter chamber 89 so as to be freely opened and closed.

  When it is necessary to open the lower side of the cab 13 for maintenance work, an operator located on the side of the support tower 33 opens the side door 90 of the airframe 11 located behind the support tower 33. By operating the lever 87 of the emergency descent valve 86 for cab emergency descent in the fuselage 11 with the right hand and lowering the cab 13, the pin insertion hole 52 provided in the left side plate of the support tower 33 and the lower link The pin insertion hole 47 provided in the left side plate of 40 is aligned, and the operator locks the pin 51 with the left hand with the pin insertion holes 52 and 47 pulled out from the pin storage hole 56 of the upper link 39. Is inserted and the downward rotation of the link mechanism 31 is locked, so that the cab 13 can be reliably prevented from falling and maintenance work is performed on the lower side of the cab 13.

  As shown in FIG. 2, the proximity switch 84 is mounted on the side surface of the support tower 33 by a mounting plate 92 fixed with a plurality of bolts 91 in the vicinity of the pin 35 that pivotally supports the upper link 39. It is installed while adjusting the mounting position in a long hole-shaped mounting hole 93 formed in the plate 92.

  The attachment position of the proximity switch 84 is provided at a position where it can be detected by coming off the upper link 39 in the vicinity of the stroke end where the upper link 39 rises most. In other words, the proximity switch 84 indirectly detects that the cab elevating cylinder 32 has reached the vicinity of the stroke end on the extension side by detecting a state in which the cab elevating cylinder 32 does not face the upper link 39 of the link mechanism 31.

  Next, functions and effects of the embodiment shown in FIGS. 1 to 4 will be described.

  When the maintenance work is completed, the lock pin 51 is pulled out from the pin insertion holes 52 and 47 and returned to the pin storage hole 56 of the upper link 39, and the dismantling work by the original working device 12 as shown in FIG. 3 is performed. . That is, the operator in the cab 13 operates the joystick lever 71, pilots the control valve 64, extends the cab elevating cylinder 32, raises the cab 13 to a high position, and dismantling work by the work device 12 Etc.

  At this time, since the proximity switch 84 faces the upper link 39 until the cab elevating cylinder 32 reaches the vicinity of the stroke end, the electromagnetic part 82 of the pressure reducing valve 81 communicates with the head side pilot line 76. However, when the cab elevating cylinder 32 reaches the vicinity of the stroke end, the proximity switch 84 is disconnected from the upper link 39 and is turned off. Therefore, the pressure reducing function of the pressure reducing valve 81 works, and the head side pilot line Since the pilot secondary pressure of 76 is automatically reduced and the control valve 64 tries to return to the neutral position, that is, the shift amount of the spool of the control valve 64 is reduced, the head side chamber 32h of the cab elevating cylinder 32 is reduced. The supplied operating flow rate is reduced, the cab elevating cylinder 32 is decelerated just before reaching the stroke end, and the cab elevating cylinder 32 is Moment of impact reaches Kuendo is relaxed.

  In this way, the proximity switch 84 detects that the cab elevating cylinder 32 is positioned in the vicinity of the stroke end on the expansion side, and the pilot pressure to the control valve 64 is reduced by the pressure reducing valve 81. Since the sudden stop at the extension stroke end can be prevented, the shaking at the time of stopping the cab 13 at the highest position can be prevented.

  In addition, since the sensor for detecting the operation of the link mechanism 31 uses the proximity switch 84 that is inexpensive and not easily damaged, it can easily detect that the cab elevating cylinder 32 is located near the stroke end on the extension side, High reliability.

  Next, another embodiment shown in FIGS. 5 to 8 will be described. 3 and 4 have the same structure, the reference numerals are used.

  In the cab elevating device 14 that drives the cab 13 that can be raised and lowered to the machine body 11 of the work machine 10 via the link mechanism 31 by the cab elevating cylinder 32, it detects that the cab elevating cylinder 32 is located near the stroke end. As shown in FIG. 6, as a sensor, a proximity switch 84a that detects the operation of the upper link 39 of the link mechanism 31 and detects that the cab elevating cylinder 32 is positioned near the stroke end on the extension side, and the cab elevating A proximity switch 84b that detects that the cylinder 32 is positioned near the stroke end on the contraction side is provided. Harnesses 83a and 83b are wired to these proximity switches 84a and 84b, respectively.

  These proximity switches 84a and 84b are drilled in the mounting plate 92 by a mounting plate 92 fixed by a plurality of bolts 91 on the side surface of the support tower 33 and in the vicinity of the pin 35 that pivotally supports the upper link 39. It is installed while adjusting the mounting position within the elongated mounting hole 93 formed.

  The mounting position of one proximity switch 84a is provided at a position where it can be detected by coming off the upper link 39 near the stroke end where the upper link 39 rises most, and the mounting position of the other proximity switch 84b is The link 39 is provided at a position where it can be detected from the upper link 39 in the vicinity of the stroke end where the link 39 descends most.

  That is, the proximity switch 84a indirectly detects that the cab elevating cylinder 32 has reached the vicinity of the extended stroke end by detecting the state in which the cab elevating cylinder 32 is not opposed to the upper link 39 of the link mechanism 31, and the proximity switch 84b. Detects indirectly that the cab elevating cylinder 32 has reached the vicinity of the contraction-side stroke end by detecting a state in which the cab elevating cylinder 32 is not opposed to the upper link 39 of the link mechanism 31.

  As shown in FIG. 5, the cab elevating cylinder 32 is provided from input lines 94 and 95 for transmitting a cab up or down command signal from the slidable input device 72 of the joystick lever 71 to the electromagnetic unit 74 of the electromagnetic proportional valve 73. Operation direction detection lines 96 and 97 as operation direction detecting means for detecting the operation direction in the telescopic operation are drawn out and connected to the input unit of the controller 98, respectively. Harnesses 83a and 83b drawn from the proximity switches 84a and 84b are connected to other inputs of the controller 98, respectively.

  The output of the controller 98 is connected to the electromagnetically operated pressure reducing valves 81a and 81b interposed in the pilot lines 76 and 77 provided for the pilot operated control valve 64 that controls the expansion and contraction of the cab elevating cylinder 32. The electromagnetic parts 82a and 82b are connected. These pressure reducing valves 81a and 81b are controlled by a controller 98 that calculates and processes the detection signals from the proximity switches 84a and 84b and the operation direction signals from the operation direction detection lines 96 and 97, so that the pilot to the control valve 64 is controlled. The pressure is controlled to be reduced. The secondary pilot lines of the pressure reducing valves 81a and 81b are a head side pilot line 76a and a rod side pilot line 77b.

  Next, the operation of the embodiment shown in FIGS. 5 and 6 will be described with reference to the flowcharts shown in FIGS. In these flowcharts, a circled number indicates a step number.

  First, FIG. 7 shows a control method when the upper link 39 and the cab elevating cylinder 32 are positioned near the stroke end on the ascending side.

(Step 1)
The controller 98 determines whether or not the proximity switch 84a detects the upper link 39.

(Step 2)
When the proximity switch 84a does not detect the upper link 39 (NO in step 1), the upper link 39 and the cab elevating cylinder 32 are located near the stroke end on the ascending side. Based on the signal, it is determined whether or not the operating directions of the upper link 39 and the cab elevating cylinder 32 are upward.

(Step 3)
If the operation direction is upward (YES in step 2), it means that the lift operation is near the end and the cab elevating cylinder 32 has reached the end of the extension stroke, so the pressure reducing valve 81a is not decompressed by the controller 98. Even when the pilot pressure output from the electromagnetic proportional valve 73 to the head side pilot line 76 is large, the pilot pressure output from the pressure reducing valve 81a to the head side pilot line 76a is reduced to a low pressure. Since the valve 64 tries to return to the neutral position, that is, the amount of shift of the spool of the control valve 64 is reduced, the operating flow rate supplied to the head side chamber 32h of the cab elevating cylinder 32 through the control valve 64 is reduced. The cab elevating cylinder 32 is decelerated just before reaching the end of the extension stroke, and reaches the end of the extension stroke. You can mitigate the impact of the time.

(Step 4)
On the other hand, if the operation direction is downward (NO in step 2), it means the start of the lowering operation in which the cab elevating cylinder 32 starts to retract from the end of the extension stroke, so the controller 98 causes the joystick lever 71 to lower the cab. Even if the command signal is output, while the proximity switch 84a detects the vicinity of the extension stroke end via the upper link 39, the pressure reducing valve 81b is kept in a reduced pressure state, and the control valve 64 is retracted from the neutral position. Since the operation is not suddenly moved to the side switching position, the operating flow supplied to the rod side chamber 32r of the cab elevating cylinder 32 does not increase suddenly, and the cab elevating cylinder 32 gradually contracts from the end of the extension stroke. It is possible to mitigate the impact when the cab elevating cylinder 32 is contracted and the stroke is suddenly started. When the proximity switch 84a no longer detects the vicinity of the extended stroke end, the pressure reducing valve 81b is controlled from the pressure reducing state to the non-pressure reducing state, and the pilot pressure output from the electromagnetic proportional valve 73 to the rod side pilot line 77 is used as it is on the rod side. Acts on the pilot line 77b.

  Next, FIG. 8 shows a control method when the upper link 39 and the cab elevating cylinder 32 are positioned near the lower stroke end.

(Step 5)
The controller 98 determines whether or not the proximity switch 84b detects the upper link 39.

(Step 6)
When the proximity switch 84b does not detect the upper link 39 (NO in step 5), the upper link 39 and the cab elevating cylinder 32 are located near the lower stroke end. Based on the signal, it is determined whether or not the operating directions of the upper link 39 and the cab elevating cylinder 32 are downward.

(Step 7)
If the operation direction is downward (YES in step 6), it means that the lowering operation is near the end and the cab elevating cylinder 32 has contracted and has reached the end of the stroke, so the pressure reducing valve 81b is not decompressed by the controller 98. The pilot pressure output from the pressure reducing valve 81b to the rod side pilot line 77b is reduced to a low pressure even when the pilot pressure output from the solenoid proportional valve 73 to the rod side pilot line 77 is large. Since the valve 64 attempts to return to the neutral position, the operating flow supplied to the rod side chamber 32r of the cab elevating cylinder 32 through this control valve 64 decreases, and the cab elevating cylinder 32 is decelerated just before reaching the stroke end by contraction. It is possible to alleviate the impact when the contraction stroke end is reached.

(Step 8)
On the other hand, if the operation direction is upward (NO in step 6), it means that the cab elevating cylinder 32 is contracted and starts to move upward from the stroke end, so the controller 98 indicates that the joystick lever 71 is lifted by a large cab. Even if the command signal is output, while the proximity switch 84b detects the vicinity of the contraction stroke through the upper link 39, the pressure reducing valve 81a is maintained in the pressure reducing state, and the control valve 64 extends from the neutral position to the cylinder. Since the side switching position is not actuated suddenly, the operating flow supplied to the head side chamber 32h of the cab elevating cylinder 32 does not increase abruptly, and the cab elevating cylinder 32 gradually extends from the contraction stroke end. It is possible to mitigate the impact when the cab elevating cylinder 32 starts its extension stroke suddenly. When the proximity switch 84b contracts and no longer detects the vicinity of the stroke end, the pressure reducing valve 81a is controlled from the pressure reducing state to the non-pressure reducing state, and the pilot pressure output from the electromagnetic proportional valve 73 to the head side pilot line 76 is directly used as the head side. It acts on the pilot line 76a.

  As described above, the proximity switches 84a and 84b operate when the cab elevating cylinder 32 is located near the stroke end on the expansion side and the contraction side, so that the end shock when the cab 13 is raised to the uppermost position and the lowering to the lowermost position. In addition to reducing both end shocks, the operation direction detection lines 96 and 97 further cause the cab elevating cylinder 32 to extend and retract when the cab elevating cylinder 32 is stopped and started (ie, when rising is stopped and when rising is started). End shock at the time of stopping, descent stop, descent start).

  Next, an embodiment not shown will be described.

  When a fan-shaped detection plate or the like is attached to the upper link 39 of the link mechanism 31 so that the proximity switch operates near the stroke end on the cab rising side and lowering side, the cab rising side and lowering side can be driven by one proximity switch. By detecting the vicinity of the stroke end, it is possible to reduce and control the shock at the stroke end.

  The sensor may be an analog sensor such as a rotary potentiometer that detects a link angle or a direct acting potentiometer that detects a cylinder stroke. Such an analog sensor can detect the extent to which the cab elevating cylinder 32 approaches the stroke end on the expansion side or the contraction side. Furthermore, the controller 98 and the pressure reducing valves 81a and 81b may be electromagnetic proportional pressure reducing valves that increase the pressure in proportion to the extent that the cab elevating cylinder 32 approaches the stroke end on the expansion side or the contraction side. When such an analog sensor and a proportional pressure reducing valve are used, if the controller 98 controls the pressure reducing control to be inversely proportional to the remaining distance to the stroke end, the end of the cab lift cylinder 32 in the expansion / contraction operation The shock can be reduced smoothly, and a smooth stop operation without a shock can be obtained.

  Further, as the operation direction detecting means for detecting the operation direction in the expansion / contraction operation of the cab elevating cylinder 32, for example, a pressure sensor or a pressure switch for detecting the pressure in the head side chamber 32h and the rod side chamber 32r of the cab elevating cylinder 32 may be used. .

  As described above, the control valve 64 automatically controls the oil amount to the cab elevating cylinder 32 only when the cab elevating cylinder 32 is started and stopped, so the cab 13 elevating speed is reduced at other times. Without making it happen, it is possible to suppress a shock at the time of starting and stopping.

  In addition, this invention can be utilized also for the cab raising / lowering apparatus which employ | adopts the X-type link mechanism using two sets of links comprised by the X form.

It is a circuit diagram which shows one Embodiment of the fluid pressure circuit and control circuit which are used for the cab raising / lowering apparatus which concerns on this invention. It is a front view which shows the sensor attachment example of a raising / lowering apparatus same as the above. It is a side view of the working machine provided with the raising / lowering apparatus same as the above. It is a perspective view of a lifting apparatus same as the above. It is a circuit diagram which shows other embodiment of the fluid pressure circuit and control circuit which are used for the cab raising / lowering apparatus which concerns on this invention. It is a front view which shows the example of sensor attachment corresponding to embodiment of FIG. It is a flowchart which shows the control method in the vicinity of the stroke end of the raise side corresponding to embodiment of FIG. It is a flowchart which shows the control method in the downward stroke end vicinity corresponding to embodiment of FIG.

Explanation of symbols

10 work machines
11 Aircraft
13 cab
14 Cab lifting device
31 Link mechanism
32 Cab lifting cylinder
64 Control valve
76, 76a, 77, 77b Pilot line
81, 81a, 81b Pressure reducing valve
84, 84a, 84b Proximity switch as sensor
96, 97 Motion direction detection line as motion direction detection means

Claims (5)

In a cab elevating device that drives a cab provided to be able to be raised and lowered via a link mechanism to a machine body of a work machine by a cab elevating cylinder,
A sensor for detecting that the cab elevating cylinder is located near the stroke end;
A pilot operated control valve that controls the telescopic movement of the cab lifting cylinder;
A cab elevating device comprising: a pressure reducing valve interposed in a pilot line of the control valve to reduce a pilot pressure to the control valve by a detection signal from a sensor. The sensor
The cab elevating device according to claim 1, wherein the cab elevating device detects an operation of the link mechanism and detects that the cab elevating cylinder is positioned near the stroke end. The sensor
The cab elevating device according to claim 1 or 2, wherein the cab elevating cylinder is detected to be positioned in the vicinity of the stroke end on the expansion side and the contraction side. The cab elevating device according to claim 3, further comprising an operation direction detecting means for detecting an operation direction in an expansion / contraction operation of the cab elevating cylinder. The pressure reducing valve
The cab elevating device according to any one of claims 1 to 4, wherein the cab elevating cylinder is a proportional pressure reducing valve that increases pressure reduction as it approaches the stroke end.

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