# Patent

## Title
Safety device for hydraulic working machine

## Abstract

There are provided: control valves 22-24 that control flow of pressure oil from the hydraulic source 21 to the hydraulic actuators 15-17; electric lever devices 51-53 that output electrical operation signals, which are drive instructions for the hydraulic actuators 15-17, in correspondence to lever operation; and a control unit 25-30 and 50 that controls the control valves 22-24 in correspondence to the operation signals. When the determination unit determines that an operation signal is not within the normal range, the hydraulic actuators 15-17 are allowed to be driven with flow of pressure oil to the hydraulic actuators 15-17 limited more significantly than in a case where it is decided that an operation signal is within the normal range.

## Background
TECHNICAL FIELD
The present invention related to a safety device for hydraulic working machine that is operated through an electric lever.
BACKGROUND ART
There is a device known in the related art that drives an electromagnetic proportional valve in correspondence to the operation amount of an electric lever and applies pilot pressure generated thereby to a control valve so as to drive a hydraulic actuator (refer to, for example, patent reference literature 1).

    Patent Reference Literature 1: Japanese Laid Open Patent Publication No. H7-19207


DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
However, if failure occurs in the electric lever itself, a signal in correspondence to the operation amount is not output from the electric lever so as to create difficulty in driving a hydraulic actuator. In this case, repair work may be affected because an operation such as changing the attitude of the actuator can not be performed when the working machine is to be moved to a safe repair site.
Means for Solving the Problems
A safety device for hydraulic working machine according to the present invention comprises: a hydraulic source; a hydraulic actuator that is driven by pressure oil from the hydraulic source; a control valve that controls a flow of pressure oil from the hydraulic source to the hydraulic actuator; an electric lever device that outputs an electrical operation signal, which is a drive instruction for the hydraulic actuator, in correspondence to lever operation; a control unit that controls the control valve in correspondence to the operation signal; and a determination unit that makes a decision as to whether or not the operation signal is within a normal range, wherein: when the determination unit determines that an operation signal is not within the normal range, the control unit allows the hydraulic actuator to be driven with a flow of pressure oil to the hydraulic actuator limited more significantly than in a case where it is decided that an operation signal is within the normal range.
When the determination unit determines that an operation signal is not within the normal range, the control unit may enlarge a dead band ranging from a point at which a lever is in a neutral state to a point at which pressure oil is supplied to the hydraulic actuator by a lever operation, compared to when it is decided that an operation signal is within the normal range.
When the determination unit determines that an operation signal is not within the normal range, the control unit may decrease an amount to which the control valve is to be operated, compared to when it is decided that an operation signal is within the normal range.
It is also possible that, upon making a decision that the operation signal is not within the normal range, the determination unit further makes a decision as to whether or not an operation signal is within a limited range which is beyond the normal range by a predetermined extent; and that when the determination unit determines that an operation signal is within the limited range, the control unit allows the hydraulic actuator to be driven with a flow of pressure oil to the hydraulic actuator limited more significantly than in a case where it is decided that an operation signal is within the normal range, and when it is decided that an operation signal has exceeded the limited range, the control unit inhibits a flow of pressure oil to the hydraulic actuator.
A power supply unit that supplies electric power to the electric lever device so as to output the operation signal may be further provided, and the determination unit may also determine an abnormality in the power supply unit.
In a case where a plurality of the power supply units are provided, it is preferable that, when the determination unit determines that an abnormality has occurred in at least one of the power supply units, the control unit invalidates only output of an electric lever device, to which electric power is supplied from a power supply unit in which it is decided that an abnormality has occurred.
The electric lever device may be a variable resistance type electric lever device which slides on a resistor pattern provided on a proximal end of a lever so as to output an operation signal.
The electric lever device may include a first and second output units that output operation signals which are symmetric with respect to each other in correspondence to an operation amount; the control unit may control the control valve in accordance with an operation signal that has been output from the first output unit; and the determination unit may make a decision as to whether or not the operation signal is within the normal range based upon a mean of the operation signals that have been output from the first and second output units.
Advantageous Effect of the Invention
According to the present invention, if it is decided that an operation signal of the electric lever device is not within the normal range, the hydraulic actuator is allowed to be driven, with the flow of pressure oil to the hydraulic actuator limited more significantly than in the case where it is decided that an operation signal of the electric lever device is within the normal range. Therefore, even if an abnormality has occurred in the electric lever device, the hydraulic actuator can be driven safely.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows an external side view of a crusher to which a safety device according to an embodiment of the present invention is applied.
FIG. 2 is a hydraulic circuit diagram showing a configuration of the safety device according to the present embodiment.
FIG. 3 shows an example of output characteristics of an electromagnetic proportional valve.
FIG. 4 shows a flowchart of an example of processing that may be executed by the control circuit of FIG. 2.
FIG. 5 shows an output characteristics of the electric lever of FIG. 2.
FIG. 6 shows a flowchart presenting an example of a variation of FIG. 4.
FIG. 7 shows the normal range and error range of an operation signal.
FIG. 8 shows another example of output characteristics of an electromagnetic proportional valve.
FIG. 9 shows an example of a variation of the electric lever.
FIG. 10 shows an output characteristics of the electric lever of FIG. 9.



BEST MODE FOR CARRYING OUT THE INVENTION
The following is an explanation of an embodiment of a safety device for hydraulic working machine according to the present invention, given in reference to FIGS. 1 ̃10.
FIG. 1 is an external side view of a crusher, which is an example of a hydraulic working machine to which the safety device according to the present embodiment is applied. The crusher, which is configured based upon a hydraulic excavator, includes an undercarriage 1, a revolving superstructure 2 rotatably mounted on top of the undercarriage 1, a boom 3 rotatably provided on the revolving superstructure 2, an arm 4 rotatably provided on the distal end of the boom, and a crusher attachment 5 rotatably provided on the distal end of the arm. A blade 6 is attached to the undercarriage 1 as an optional component. It is to be noted that, in place of the attachment 5, a bucket is attached to a standard hydraulic excavator.
The boom 3 is vertically rotatably supported by a boom cylinder 11. The arm 4 is vertically rotatably supported by an arm cylinder 12. The attachment 5 is vertically rotatably supported by a bucket cylinder 13. The undercarriage 1 is driven by right and left hydraulic motors 14 for traveling. A standard hydraulic excavator initially includes hydraulic actuators such as the cylinders 11 to 13 and the motors 14. In addition, as FIG. 2 shows, in the present embodiment, a hydraulic cylinder 15 that opens/closes the distal end of the attachment 5, a hydraulic motor 16 that rotates the attachment 5 relative to the arm 4, and a hydraulic cylinder 17 that drives the blade 6 are included as optional hydraulic actuators.
The standard hydraulic actuators 11 to 14 are driven by hydraulic pilot system. More specifically, a pressure reducing valve is actuated by operating a control lever provided for each of the actuators 11 to 14 so as to generate pilot pressure, and direction control valves (not figured herein) are each switched by the pilot pressure so as to drive the hydraulic actuators 11 to 14. On the other hand, if the hydraulic pilot system is adopted to drive the optional hydraulic actuators 15 to 17, a circuit structure would be complicated. Therefore, not a hydraulic pilot type actuator but an electric lever type actuator is adopted in the optional hydraulic actuators 15 ̃17 so that each actuator is operated by an electric lever.
FIG. 2 is a hydraulic circuit diagram showing the configuration of the safety device according to the present embodiment, in particular, presenting a drive circuit of the hydraulic actuators 15 to 17 which are driven by electric lever system. Pressure oil from a hydraulic pump 21 being driven by an engine (not figured herein) is supplied to the hydraulic actuators 15 to 17 through direction control valves 22 to 24, respectively. Pressure of pressure oil from a pilot pump 31 is reduced by electromagnetic proportional pressure reducing valves (hereinafter called electromagnetic proportional valves) 25 to 30 and the pressure oil is applied to each pilot port of the direction control valves 22 to 24, so that the pilot pressure switches the direction control valves 22 to 24.
An electric lever 51 that instructs open/close movement of the attachment 5, an electric lever 52 that instructs rotational movement of the attachment 5, and an electric lever 53 that instructs drive of the blade 6 are connected to a controller 50. A predetermined voltage vx (e.g., 5 v) is applied from a power supply circuit 50a in the controller 50 to the electric levers 51 and 52, whereas a predetermined voltage (e.g., 5 v) is applied from a power supply circuit 50b to the electric lever 53. The electric levers 51 to 53 are variable resistance electric levers, in which resistance value varies in correspondence to the operation amount, and electric signals in correspondence to the operation amount of the electric levers 51 to 53 are input to a control circuit 50c in the controller 50. The controller 50 includes a processing unit including a CPU, a ROM, a RAM, other peripheral circuits, and so on. It is to be noted that a reference numeral 54 represents a battery that supplies the controller 50 with power at a predetermined voltage (e.g., 24V).
FIG. 3 shows the relationship between a lever signal v being output from the electric levers 51 to 53 and control pressure P corresponding to the lever signal. Characteristics f1 and f2 are stored in the controller 50 in advance as lever characteristics to be achieved when the electric levers 51 to 53 operate normally. The characteristic f1 is that of control pressure P which is output to the electromagnetic proportional valves 25, 27, and 29, whereas the characteristic f2 is that of control pressure which is output to the electromagnetic proportional valves 26, 28, and 30. The control circuit 50c controls the electromagnetic proportional valves 25 to 30 so that pilot pressure applied to the control valves 22 to 24 becomes control pressure P corresponding to the lever signal v.
In FIG. 3, the lever signal is v0 (e.g., 2.5 v) when a control lever 31, 32 or 33 is in neutral. A dead band, in which control pressure is zero (P=0), is formed in a range where the lever signal v is between va1 (e.g., 2.3 v) and vb1 (e.g., 2.7 v), including v0 (va1≦v≦vb1). The range in which the lever signal v is va2≦v<va1 and vb1<v≦vb2 is a control pressure variable region where control pressure P increases with an increase in the operation amount of the control lever 31, 32 or 33 along the characteristics f1 and f2. The range where the lever signal v is v<va2 and vb2<v is the control pressure maximum region where control pressure P is maximum (P=Pa).
In the electric lever type hydraulic circuit which is thus configured, the hydraulic actuators 15 to 17 do not act properly in the case of failure (e.g., when stick occurs) of the electromagnetic proportional valves 25 to 30. Accordingly, in the present embodiment, abnormality in the electromagnetic proportional valves 25 to 30 is monitored in the following manner so as to limit the action of the hydraulic actuators 15 to 17 in the event of a fault. It is to be noted that in the description below the lever signals v of the electric levers 51 to 53 may be respectively indicated by v51 to v53, and control pressure P of the electromagnetic proportional valves 25 to 30 may be respectively indicated by P25 to P30.
As FIG. 2 shows, a shuttle valve 41 is connected to pipelines L1 and L2 that respectively connect the pilot ports of the direction control valve 22 with the electromagnetic proportional valves 25 and 26, and a shuttle valve 42 is connected to pipelines L3 and L4 that respectively connect the pilot ports of the direction control valve 23 with the electromagnetic proportional valves 27 and 28. Pressure oil on the high pressure side of the pipelines L1 and L2 and the pipelines L3 and L4 is guided to pipelines L7 and L8, respectively, through the shuttle valves 41 and 42. In addition, a shuttle valve 43 is connected to the pipelines L7 and L8 so as to guide pressure oil on the high pressure side of the pipelines L7 and L8 to a pipeline L9. Pressure of the pressure oil guided to the pipeline L9, in other words, the maximum pressure P1 in the pipelines L1 to L4 is detected by a pressure sensor 45. The shuttle valves 41 to 43 and the pressure sensor 45 constitute a first abnormality detection circuit that detects abnormality in the electromagnetic proportional valves 25 to 28.
A shuttle valve 44 is connected to pipelines L5 and L6 that respectively connect the pilot ports of the direction control valve 24 with the electromagnetic proportional valves 29 and 30, and pressure oil on the high pressure side of the pipelines L5 and L6 is guided to a pipeline L10 through the shuttle valve 44. Pressure of the pressure oil guided to the pipeline L10, in other words, the maximum pressure P2 in the pipelines L5 and L6 is detected by a pressure sensor 46. The shuttle valve 44 and the pressure sensor 46 constitute a second abnormality detection circuit that detects abnormality in the electromagnetic proportional valves 29 and 30.
An electromagnetic switching valve 47 is provided between the pilot pump 31 and the electromagnetic proportional valves 25 to 28, whereas an electromagnetic switching valve 48 is provided between the pilot pump 31 and the electromagnetic proportional valves 29 and 30. The electromagnetic switching valves 47 and 48 operate in response to a signal from the control circuit 50c. As the electromagnetic switching valve 47 is switched to the position A, pilot pressure is allowed to flow to the electromagnetic proportional valves 25 to 28, whereas as the electromagnetic switching valve 47 is switched to the position B, pilot pressure is prohibited to flow to the electromagnetic proportional valves 25 to 28. As the electromagnetic switching valve 48 is switched to the position A, pilot pressure is allowed to flow to the electromagnetic proportional valves 29 and 30, whereas as the electromagnetic switching valve 48 is switched to the position B, pilot pressure is prohibited to flow to the electromagnetic proportional valves 29 and 30.
In the above structure, a drive circuit of the hydraulic actuators 15 and 16 that perform one operation (crush operation) and a drive circuit of the hydraulic actuator 17 that performs another operation (blade operation) are grouped separately. Abnormalities in each of the groups are detected by the pressure sensors 45 and 46, respectively. If any abnormality is detected, the electromagnetic switching valve 47 or 48 is operated so as to prohibit driving of the actuators 15 and 16 or the actuator 17 of the group in which the abnormality is detected. In this manner, the two pressure sensors 45 and 46 and the two electromagnetic switching valves 47 and 48, which are smaller than the three hydraulic actuators in number, are provided, thereby achieving efficiency.
FIG. 4 is a flowchart of an example of processing that may be executed by the control circuit 50c according to the present embodiment. The processing in this flowchart starts, for example, as an engine key switch is turned on. In an initial state, the electromagnetic switching valves 47 and 48 have already been switched to the position A. In a step S1, each of the lever signals v51 to v53 of the electric levers 51 to 53 is read. In a step S2, based upon predetermined characteristics of FIG. 3, each of the control pressures P25 to P30 in correspondence with the lever signals v51 to v53 is calculated. In addition, the maximum value P1max of the control pressures P25 to P28 corresponding to a detected value P1 of the pressure sensor 45 and the maximum value P2max of the control pressures P29 and P30 corresponding to a detected value P2 of the pressure sensor 46 are each calculated. In a step S3, control signals are output to the electromagnetic proportional valves 25 to 30 so that pilot pressures applied to the control valves 22 to 24 become equal to the control pressures P25 to P30. In a step S4, detected values P1 and P2 which are detected by the pressure sensors 45 and 46 are read.
In a step S5, a deviation API between the maximum value P1max of the control pressures P25 to P28 and the detected value P1 of the pressure sensor 45 is calculated so as to make a decision as to whether or not the deviation ΔP1 is equal to or less than a predetermined value. This is a process to make a decision as to whether or not an abnormality has occurred in the electromagnetic proportional valves 25 to 28. As long as the deviation ΔP1 is equal to or less than the predetermined value, it is decided that outputs of the electromagnetic proportional valves 25 to 28 are normal.
If an affirmative decision is made in the step S5, the flow of processing proceeds to a step S6. In the step S6, a control signal is output to the electromagnetic switching valve 47 so as to switch the electromagnetic switching valve 47 to the position A. This allows pilot pressure to flow to the electromagnetic proportional valves 25 to 28. On the other hand, if a negative decision is made in the step S5, the flow of processing proceeds to a step S7. In this case, it is decided that the output of any of the electromagnetic proportional valves 25 to 28 which generates the maximum control pressure P1max is abnormal, and a control signal is output to the electromagnetic switching valve 47 so as to switch the electromagnetic switching valve 47 to the position B. This prohibits pilot pressure from flowing to the electromagnetic proportional valves 25 to 28.
In a step S8, a deviation ΔP2 between the maximum value P2max of the control pressures P29 and P30 and the detected value P2 of the pressure sensor 46 is calculated so as to make a decision as to whether or not the deviation ΔP2 is equal to or less than a predetermined value. This is a process to make a decision as to whether or not an abnormality has occurred in the electromagnetic proportional valves 29 and 30. As long as the deviation ΔP2 is equal to or less than the predetermined value, it is decided that outputs of the electromagnetic proportional valves 29 and 30 are normal.
If an affirmative decision is made in the step S8, the flow of processing proceeds to a step S9. In the step S9, a control signal is output to the electromagnetic switching valve 48 so as to switch the electromagnetic switching valve 48 to the position A. This allows pilot pressure to flow to the electromagnetic proportional valves 29 and 30. On the other hand, if a negative decision is made in the step S8, the flow of processing proceeds to a step S10. In this case, it is decided that the output of any of the electromagnetic proportional valves 29 and 30 which generates the maximum control pressure P2max is abnormal, and a control signal is output to the electromagnetic switching valve 48 so as to switch the electromagnetic switching valve 48 to the position B. This prohibits pilot pressure from flowing to the electromagnetic proportional valves 29 and 30. In a step S11, a control signal is output to an indicator 55 (FIG. 2) so as to display abnormality information of the electromagnetic proportional valves 25 to 30.
More specific explanation is now given as to the operation of the safety device according to the first embodiment.
(1) In Normal State
Firstly, the case where all of the electromagnetic proportional valves 25 to 30 operate properly is explained. For instance, when the electric lever 51 is operated so as to output a drive signal to the electromagnetic proportional valve 25 (the step S3), pilot pressure is applied from the pilot pump 31 to the direction control valve 22 through the electromagnetic proportional valve 25. The pilot pressure is also guided to the pipeline L9 through the shuttle valves 41 and 43, and is detected by the pressure sensor 45. At this time, if the electromagnetic proportional valve 25 acts normally, the deviation ΔP1 between the maximum value P1max (=P25) of control pressure at the first abnormality detection circuit and the detected value P1 of pilot pressure is equal to or less than the predetermined value. Therefore, the electromagnetic switching valve 47 is switched to the position A (the step S6) so as to allow pilot pressure to flow to the direction control valve 22, thereby driving the actuator 15 in correspondence to the operation amount of the lever.
For example, when the electric lever 52 is operated so as to output a drive signal to the electromagnetic proportional valve 27, pilot pressure is applied to the direction control valve 23 through the electromagnetic proportional valve 27. The pilot pressure is also guided to the pipeline L9 through the shuttle valves 42 and 43, and is detected by the pressure sensor 45. At this time, if the electromagnetic proportional valve 27 acts normally, the deviation ΔP1 between the maximum value P1max (=P27) of control pressure and the detected value P1 of pilot pressure is equal to or less than the predetermined value. Therefore, the electromagnetic switching valve 47 is switched to the position A so as to allow pilot pressure to flow to the direction control valve 23, thereby driving the actuator 16 in correspondence to the operation amount of the lever. It is to be noted that since operations for the other electromagnetic proportional valves 26 and 28 to 30 are the same, explanations for them are not given herein.
(2) In Abnormal State
The case where the output of at least one of the electromagnetic proportional valves 25 to 30 is abnormal is explained. For instance, in the event that the output of the electromagnetic proportional valve 25 is abnormal, even if a control signal in accordance with the operation amount of the electric lever 51 is output to the electromagnetic proportional valve 25, pilot pressure corresponding to the control pressure P25 does not apply to the direction control valve 22, so that the deviation ΔP1 between the maximum value P1max (=P25) of control pressure and the detected value P1 of pilot pressure becomes greater than the predetermined value. This causes the electromagnetic switching valve 47 to be switched to the position B (the step S7), the pilot ports of the direction control valves 22 and 23 to be communicated with a reservoir, and the direction control valves 22 and 23 to be forcibly switched to a neutral position. As a result, the actuators 15 and 16 are prohibited from driving, so that malfunction of the actuator 15 caused by failure of the electromagnetic proportional valve 25 can be prevented.
At this time, if the outputs of the electromagnetic proportional valves 29 and 30 are normal, the electromagnetic switching valve 48 maintains the position A, which is the initial position (the step S9), and the operation of the actuator 17 in accordance with operation of the electric lever 53 is allowed. Accordingly, even in the case of failure of the electromagnetic proportional valve 25, the operation of the actuator 17, which is unaffected by failure, is not limited, thereby minimizing effect caused by the electromagnetic proportional valve 25.
In the event that the output of the electromagnetic proportional valve 27 is abnormal, even if a control signal in accordance with the operation amount of the electric lever 52 is output to the electromagnetic proportional valve 27, pilot pressure corresponding to the control pressure P27 does not apply to the direction control valve 23, so that the deviation ΔP1 between the maximum value P1max (=P27) of control pressure and the detected value P1 of pilot pressure becomes greater than the predetermined value. This causes the electromagnetic switching valve 47 to be switched to the position B, and the actuator 16 to be prohibited from driving. Therefore, a single pressure sensor 45 can detect not only failure of the electromagnetic proportional valve 25 but also failure of the electromagnetic proportional valve 27, thereby reducing the number of sensors and reducing the costs.
Thus, in the present embodiment, pilot pressures applied to the direction control valves 22 and 23 are detected by the pressure sensor 45 through the shuttle valves 41 to 43, and pilot pressure applied to the direction control valve 24 is detected by the pressure sensor 46 through the shuttle valve 44. This enables the pressure sensors 45 and 46, which are small in number, to detect abnormality in the greater number of the electromagnetic proportional valves 25 to 30 and thus, the safety device can be achieved at low cost.
The electromagnetic switching valve 47 is provided between the electromagnetic proportional valves 25 to 28 and the pilot pump 31, whereas the electromagnetic switching valve 48 is provided between the electromagnetic proportional valves 29 and 30 and the pilot pump 31. When any abnormality in the electromagnetic proportional valves 25 to 30 is detected by the pressure sensors 45 and 46, only the actuator which is acted by the electromagnetic proportional valve in which an abnormality has been detected is prohibited from driving. This prevents the drive of the actuators 15 to 17 from being unnecessarily limited, so that the operation can be continued using the normal electromagnetic proportional valves.
Abnormalities in the actuators 15 and 16 for the attachment are detected by a single pressure sensor 45 through the shuttle valves 41 to 43. More specifically, in this case, if an abnormality has occurred in at least one of the electromagnetic proportional valves 25 to 28, the attachment 5 can not work properly, and therefore the pressure sensor 45 is configured to detect whether or not the attachment 5 can work properly. This further reduces the number of the pressure sensors, thereby achieving efficiency.
In electric lever type drive circuits, failure may occur, not only in the electromagnetic proportional valves 25 to 30, but also in the electric levers 51 to 53 themselves. In that case, the actuators 15 to 17 can not be driven in accordance with the operation amount of the electric levers 51 to 53, which may interfere with the work operation. Therefore, in the present embodiment, the safety device is configured as follows so as to address abnormalities also in the electric levers 51 to 53.
FIG. 5 shows the relationship of the lever signal v with respect to the operation angle s of a electric lever 51, 52 or 53. When the electric lever 51, 52 or 53 works normally, the lever signal v varies along a characteristic g1 (solid line). According to the characteristic g1, the lever signal is v0 when the electric lever 51, 52 or 53 is in neutral (s=0), whereas, the lever signal becomes va3 (e.g., 0.5 v) when the electric lever 51, 52 or 53 is fully operated in one direction (s=−s1), and the lever signal becomes vb3 (e.g., 4.5 v) when the electric lever 51, 52 or 53 is fully operated in the opposite direction (s=+s1). It is to be noted that, as FIG. 3 shows, the lever signals va3 and vb3 satisfy the conditions va3<va2 and vb2<vb3, respectively.
The variable resistance electric levers 51 to 53 slide on resistor patterns provided on the proximal ends of the levers so as to output the lever signal v. Therefore, the patterns may become worn due to the slide of the levers 51 to 53. If the patterns become worn, the output characteristics of the electric levers 51 to 53 shift, for example, as represented by a characteristic g2 (dotted line). On the other hand, since resistance value increases if wear dust of the patterns adheres to a part of the patterns, the lever signal v locally decreases as a characteristic g3 (dotted line) indicates. In contrast, since resistance value decreases if a part of the patterns delaminates, the lever signal v locally increases as a characteristic g4 (dotted line) indicates. In the case where the output is represented by any of the characteristics g2 to g4, an abnormality has occurred in any of the electric levers 51 to 53 themselves. In this case, output of the lever signal v is limited as follows.
FIG. 6 is an example of a flowchart including processing for addressing abnormalities in the electric levers 51 to 53. In this flowchart, the process executed in the step S2 of FIG. 4 is modified. In other words, upon reading the lever signals v51 to v53 in the step S1, the flow of process proceeds to a step S101 to make a decision as to whether or not the lever signals v51 to v53 are within the normal range. The normal range is, as FIG. 7 shows, a range between va3 and vb3 (va3≦v≦vb3), i.e., a range of the output characteristics g1 in the normal state as shown in FIG. 5. Upon making an affirmative decision in the step S101, the flow of process proceeds to a step S102 to calculate the control pressures P25 to P30 based upon the characteristics f1 and f2 of FIG. 3. Then, in the step S3, the electromagnetic proportional valves 25 to 30 are controlled so that pilot pressures applied to the control valves 22 to 24 become equal to the control pressures P25 to P30.
On the other hand, upon making a decision in the step S101 that the lever signals are not within the normal range, the flow of process proceeds to a step S103 to make a decision as to whether or not the lever signals are within the first error range. The first error range is, as FIG. 7 shows, a range of va4 (e.g., 0.4 v)≦v<va3 and a range of vb3<v≦vb4 (e.g., 4.6 v), i.e., ranges beyond the normal range by a predetermined value (e.g., 0.1 v). The first error range is set so as to correspond to the characteristics g2 to g4 of FIG. 5. Upon making an affirmative decision in the step S103, the flow of process proceeds to a step S104, to calculate the control pressures P25 to P30 based upon the characteristics f3 and f4 as shown in FIG. 8. Then, in the step S3, the electromagnetic proportional valves 25 to 30 are controlled so that pilot pressures applied to the control valves 22 to 24 become equal to the control pressures P25 to P30.
The characteristic f3 shown in FIG. 8 is a characteristic of control pressure to be output to the electromagnetic proportional valves 25, 27, and 29, whereas the characteristic f4 is a characteristic of control pressure to be output to the electromagnetic proportional valves 26, 28, and 30. In FIG. 8, a dead band is formed in a range of va5≦v≦vb5, where control pressure is zero (P=0). This dead band is wider than the normal dead band (va1≦v≦vb1). The range in which the lever signal v is between va2 and va5 (va2≦v≦va5) and between vb5 and vb2 (vb5≦v≦vb2) is a control pressure variable region where control pressure P increases with an increase in the operation amount of the control levers 51 to 53 along the characteristics f3 and f4. The range where the lever signal is v≦va2 and vb2≦v is the control pressure maximum region where control pressure P is maximum (P=Pb). The maximum control pressure Pb in the abnormal state is smaller than the maximum control pressure Pa in the normal state. For example, Pb is approximately 0.4 to 0.6 times Pa.
Upon making a decision in the step S103 that the lever signal is not in the first error range but in the second error range (v<va4 or v>vb4) shown in FIG. 7, the flow of processing proceeds to a step S105 to stop outputting control signal to any of the electromagnetic proportional valves 25 to 30 that is operated by the particular electric lever 51, 52 or 53. Next, information that an abnormality has occurred in any of the levers 51 to 53 is displayed on the indicator 55 in the step S11.
In the above, as long as the electric levers 51 to 53 are normal, lever signals are output within the normal range va3≦v≦vb3 throughout the operation range of the levers 51 to 53 (characteristics g1 of FIG. 5). This causes the electromagnetic proportional valves 25 to 30 to be controlled based upon the characteristics f1 and f2 shown in FIG. 8 (the step S102), the predetermined maximum pilot pressure Pa to be applied to the direction control valves 22 to 24 when the levers are fully operated, and the hydraulic actuators 15 to 17 to be driven at high speed.
On the other hand, if output characteristics of the electric lever 51 is shifted to the characteristic g2 shown in FIG. 5 due to, for instance, worn pattern, the lever signal generated when the electric lever 51 is fully operated exceeds the normal range (v<va3). Similarly, an abrupt change in output characteristics of the electric lever 51 as the characteristics g3 and g4 shown in FIG. 5 due to wear dust of the patterns adhering to a part of the patterns or a part of the patterns having delaminated causes the lever signal to exceed the normal range. In this case, the electromagnetic proportional valves 25 and 26 are controlled based upon the characteristics f3 and f4 shown in FIG. 8 (the step S104).
Accordingly, the dead band, ranging from the neutral state of the lever to the point at which the control valve 22 is opened by lever operation, becomes wider compared to that in the normal state, thereby improving safety when the lever is operated. In addition, the maximum control pressure Pb achieved when the lever is fully operated is smaller than the maximum control pressure Pa in the normal state, and the maximum operation amount of the control valve 22 becomes smaller. This limits drive speed of the hydraulic actuator 15 when the lever is fully operated, thereby ensuring performing the minimum operation even if an abnormality has occurred in the electric lever 51.
On the other hand, in the event that, for instance, disconnection has occurred in wiring of the electric lever 51, the lever signal exceeds the first error range to be in the second error range. This stops output of control signals to the electromagnetic proportional valves 25 and 26 and causes pilot pressure not to apply to the direction control valve 22, so that the direction control valve 22 maintains a neutral position. Accordingly, the hydraulic actuator 15 maintains an inactive state, thereby preventing the hydraulic actuator 15 from undesirably driving. In this case, an abnormal state of the electric lever 51 is displayed on the indicator 55 so that an operator can easily recognize the abnormal state.
As described above, a decision is made as to whether or not the lever signals v of the electric levers 51 to 53 are within the normal range. If the lever signal is within the normal range, the corresponding electromagnetic proportional valve 25, 26, 27, 28, 29 or 30 is controlled based upon the characteristics f1 and f2 in the normal state. Whereas, if the lever signal is outside the normal state (the first error range), the corresponding electromagnetic proportional valve 25, 26, 27, 28, 29 or 30 is controlled based upon the characteristics f3 and f4 in an abnormal state. This enables the hydraulic actuators 15 to 17 to drive while limiting operations the actuators even if an abnormality has occurred in the lever signal v, thereby ensuring safe operation.
The dead band for the lever neutral state is widened when the lever signal v exceeds the normal range (to be in the first error range). Therefore, the hydraulic actuators 15 to 17 are not driven unless operation amount of the lever becomes greater, thereby enhancing safety in the event that an abnormality has occurred in the lever signal v. In addition, the maximum control pressure Pb applied to the control valves 22 to 24 is smaller than the maximum control pressure Pa in the normal state. Therefore, drive speed of the hydraulic actuators 15 to 17 is restricted, thereby ensuring safe operation.
Output of control signals to the electromagnetic proportional valves 25 to 30 is stopped when the lever signal v exceeds the first error range (to be in the second error range). Therefore, in the event that disconnection occurs in one of the signal lines of the electric levers 51 to 53, the corresponding hydraulic actuator 15, 16 or 17 is prohibited from being driven, thereby resulting in a high level of safety. In the event that an abnormality has occurred in the lever signal v from any of the electric levers 51 to 53, drive of only the corresponding hydraulic actuator 15, 16 or 17 operated by the particular electric lever 51, 52 or 53 is limited. Therefore, limitation imposed on the operation of the hydraulic actuators 15 to 17 can be minimized.
It is to be noted that although in the above embodiment the lever signals v in correspondence to the operation amount of the levers are output from the electric levers 51 to 53 so as to control the electromagnetic proportional valves 25 to 30, the structures of the electric levers 51 to 53 are not limited to those described in reference to the embodiment. For instance, as FIG. 9 shows, signals in correspondence to the operation amount of the electric levers 51 to 53 may be picked up from a signal line a (main), which functions as a first output unit, and a signal line b (sub), which functions as a second output unit, so as to control the electromagnetic proportional valves 25 to 30 based upon output from the signal line a (main output vm) and output from the signal line b (sub output vs). Explanation on this point will now be given below. It is to be noted that in FIG. 9 a signal line c and a signal line d are connected to a power source and the ground, respectively.
The electric levers 51 to 53 of FIG. 9 exhibit output characteristics in the normal state, for example, as shown in FIG. 10, in which the solid line and the dotted line indicate characteristics of the main output vm and the sub output vs, respectively. A mechanical dead band for the lever mechanism is provided near the neutral position of the lever. The main output vm and the sub output vs are symmetric with respect to each other relative to a reference signal v0, and the mean of the sum of the both outputs vmea (=(vm+vs)/2) is equal to the reference signal v0 regardless of the operation angle of the lever.
If the mean vmea of the sum of the main output vm and the sub output vs is greater or smaller than the reference signal v0, it is decided that the lever signal v is abnormal. This enables an abnormality of the electric levers 51 to 53 to be determined even if output characteristics are shifted due to worn pattern, without the electric levers 51 to 53 being fully operated. In this case, if vmea and v0 are equal, the electromagnetic proportional valves 25 to 30 may be controlled based upon the characteristics f1 and f2 of FIG. 8. If the difference between vmea and v0 is equal to or less than a predetermined value, the electromagnetic proportional valves 25 to 30 may be controlled based upon the characteristics f3 and f4 of FIG. 8. If the difference between vmea and v0 exceeds the predetermined value, signal output to the electromagnetic proportional valves 25 to 30 may be stopped.
A decision may be made as to whether or not the main output vm and the sub output vs are each within the normal range. In the case where only the main output vm is not within the normal range, the electromagnetic proportional valves 25 to 30 may be controlled based upon the characteristics f1 and f2 with the sub output vs as lever signal v, on the other hand, in the case where only the sub output vs is not within the normal range, the electromagnetic proportional valves 25 to 30 may be controlled based upon the characteristics f1 and f2 with the main output vm as lever signal v.
In the present embodiment, as FIG. 2 shows, signals from the power supply circuits 50a and 50b of the controller 50 are taken into the control circuit 50c, and an abnormality decision is also made as to the power supply circuits 50a and 50b. In this case, the control circuit 50c makes a decision as to whether or not signals from the power supply circuits 50a and 50b are equal to a predetermined voltage vx (5 v). If the signals are not equal to the predetermined voltage vx, it is decided that an abnormality has occurred in the power supply circuits 50a and 50b. This allows a decision to be made as to whether an abnormality has occurred in the power supply circuits 50a and 50b or an abnormality has occurred in the electric lever itself in the event that the operation signal v is not within the normal range. Therefore, it is possible to identify in which part the failure has occurred. In the event that an abnormality has occurred in at least one of the power supply circuits 50a and 50b (e.g., 50a), only output of the electric levers 51 and 52, to which electric power is supplied from the power supply circuit 50a, may be disabled. This allows the electric lever 53 to be operated with no difficulty by power from the power supply circuit 50b, in which any abnormality has not occurred.
It is to be noted that although in the above embodiment (FIG. 2), the first abnormality detection circuit, which is constituted by the shuttle valves 41 to 43 and the pressure sensor 45, detects abnormality in output of the electromagnetic proportional valves 25 to 28 for driving the hydraulic actuators 15 and 16, as well as, the second abnormality detection circuit, which is constituted by the shuttle valve 44 and the pressure sensor 46, detects abnormality in output of the electromagnetic proportional valves 29 and 30 for driving the hydraulic actuator 17, the structures of the abnormality detection circuits may be varied depending upon the type of a hydraulic actuator. For instance, in the case where a hydraulic actuator of the same type as the hydraulic actuator 17 is provided, an abnormality decision may be made by using output, selected by a shuttle valve, of either the electromagnetic proportional valve for driving the said hydraulic actuator or the electromagnetic proportional valves 29 and 30 for driving the hydraulic actuator 17.
Although in the above, a single abnormality detection circuit detects an abnormality in output of the electromagnetic proportional valves 25 to 28 corresponding to the hydraulic actuators 15 and 16, which perform the same work operation, combination of the electromagnetic proportional valves is not limited to those mentioned above and may be varied appropriately. More specifically, not only the electromagnetic proportional valves 25 to 28, which are provided so as to perform the same work operation, but also any electromagnetic proportional valves may be grouped depending upon characteristics of individual working attachments and/or working conditions.
It is to be noted that although in the above embodiment a decision is made at the control circuit 50c as to which of the normal range, the first error range, and the second error range the lever signal v is within, any structure may be adopted in a determination unit as long as a decision is made as to at least whether or not the lever signal v is within the normal range. Accordingly, an abnormality of the power supply circuits 50a and 50b, which is power supply units, may not be determined. Although the electromagnetic proportional valves 25 to 30 are controlled based upon the characteristics f3 and f4 if the lever signal v exceeds the normal range, the electromagnetic proportional valves 25 to 30 may be controlled based upon other characteristics on the following conditions. That is, if it is decided that the lever signal v is not within the normal range, the hydraulic actuators 15 to 17 are allowed to be driven, with the flow of pressure oil to the hydraulic actuators 15 to 17 limited or regulated compared to the case where it is decided that the lever signal v is within the normal range. In other words, any structures may be adopted in the controller 50 and the like, which functions as a control unit, as long as, if it is decided that an operation signal is not within the normal range, the hydraulic actuators 15 to 17 are allowed to be driven with the flow of pressure oil to the hydraulic actuators 15 to 17 restricted by larger extent than in the case where it is decided that the operation signal is within the normal range.
In addition, although the electromagnetic proportional valves 25 to 30 are controlled in correspondence to the operation signals v so as to control the direction control valves 22 to 24, any structure may be adopted in the control unit as long as the control valves 22 to 24 are controlled in correspondence to the operation signals v. If the operation signal v is within the first error range (within a limited range), the electromagnetic proportional valves are controlled based upon the characteristics f3 and f4 so as to allow the hydraulic actuators 15 to 17 to be driven with drives of the hydraulic actuators 15 to 17 limited. If the operation signal v exceeds the first error range, output to the electromagnetic proportional valves 25 to 30 is stopped so as to prohibit the hydraulic actuators 15 to 17 from being driven. However, the structure of a control unit is not limited to that described in reference to the embodiment. Although an example of the driving circuit of the hydraulic actuators 15 to 17 is presented in FIG. 2, the structure of a hydraulic circuit is not limited to that described in reference to the embodiment. Any structure may be adopted in the electric levers 51 to 53, as electric lever devices, as long as the operation signal v is output by lever operation.
Although the above embodiment is adopted in a crusher (FIG. 1), which is based upon a hydraulic excavator, the above embodiment may be adopted in the same manner in other hydraulic working machines. Namely, as long as the features and functions of the present invention are realized effectively, the present invention is not limited to the safety device for hydraulic working machine achieved in the embodiment.
The disclosure of the following priority application are herein incorporated by reference:
Japanese Patent Application No. 2007-50761 (filed on 28 Feb. 2007)

## Claims

1. A safety device for hydraulic working machine, comprising:
a hydraulic source;
a hydraulic actuator that is driven by pressure oil from the hydraulic source;
a control valve that controls a flow of pressure oil from the hydraulic source to the hydraulic actuator;
an electric lever device that outputs an electrical operation signal, which is a drive instruction for the hydraulic actuator, in correspondence to lever operation;
a control unit that controls the control valve in correspondence to the operation signal; and
a determination unit that makes a decision as to whether or not the operation signal is within a normal range, wherein:
when the determination unit determines that an operation signal is not within the normal range, the control unit allows the hydraulic actuator to be driven with a flow of pressure oil to the hydraulic actuator limited more significantly than in a case where it is decided that an operation signal is within the normal range,
upon making a decision that the operation signal is not within the normal range, the determination unit further makes a decision as to whether or not an operation signal is within a limited range which is beyond the normal range by a predetermined extent; and
when the determination unit determines that an operation signal is within the limited range, the control unit allows the hydraulic actuator to be driven with a flow of pressure oil to the hydraulic actuator limited more significantly than in a case where it is decided that an operation signal is within the normal range, and when it is decided that an operation signal has exceeded the limited range, the control unit inhibits a flow of pressure oil to the hydraulic actuator.

2. A safety device for hydraulic working machine according to claim 1, wherein:
when the determination unit determines that an operation signal is not within the normal range, the control unit enlarges a dead band ranging from a point at which a lever is in a neutral state to a point at which pressure oil is supplied to the hydraulic actuator by a lever operation, compared to when it is decided that an operation signal is within the normal range.

3. A safety device for hydraulic working machine according to claim 1, wherein:
when the determination unit determines that an operation signal is not within the normal range, the control unit decreases an amount to which the control valve is to be operated, compared to when it is decided that an operation signal is within the normal range.

4. A safety device for hydraulic working machine according to claim 1, further comprising:
a power supply unit that supplies electric power to the electric lever device so as to output the operation signal, wherein:
the determination unit also determines an abnormality in the power supply unit.

5. A safety device for hydraulic working machine according to claim 4, further comprising:
a plurality of the power supply units, wherein:
when the determination unit determines that an abnormality has occurred in at least one of the power supply units, the control unit invalidates only output of an electric lever device, to which electric power is supplied from a power supply unit in which it is decided that an abnormality has occurred.

6. A safety device for hydraulic working machine according to claim 1, wherein:
the electric lever device is a variable resistance type electric lever device which slides on a resistor pattern provided on a proximal end of a lever so as to output an operation signal.

7. A safety device for hydraulic working machine according to claim 6, wherein:
the electric lever device includes a first and second output units that output operation signals which are symmetric with respect to each other in correspondence to an operation amount;
the control unit controls the control valve in accordance with an operation signal that has been output from the first output unit; and
the determination unit makes a decision as to whether or not the operation signal is within the normal range based upon a mean of the operation signals that have been output from the first and second output units.