Patent Application
20240279907
The present invention relates to a technical field of hydraulic control system in working machines such as a hydraulic excavator.
Among the working machines such as hydraulic excavators, there are provided with various hydraulic actuators such as a left and right travel motor that causes the lower travel body to travel and causes the upper swivel body to support on the lower travel body in a free swivel manner, a working part attached to the upper swivel body; a swivel motor that causes the upper swivel body to swivel, and a plurality of working hydraulic actuators that drive the working part. Such a working machine is usually provided with a swivel parking brake that imparts braking to the swivel of the upper swivel body in order to prevent the upper swivel body from turning, for example, when parking on a slope. As such a swivel parking brake, a mechanical brake that allows the swivel to be released from the brake state in which the swivel is braked by supplying pressure oil is commonly used.
However, in such a working machine provided with a swivel parking brake, if the upper swivel body remains in a swivel brake state due to the swivel parking brake when the working part attached to the upper swivel body is driven during the swivel stop, there is a concern that the swivel parking brake and the swivel reducer will be overloaded when the force to swivel the upper swivel body is activated, resulting in damage to these devices.
Therefore, as a valve that supplies pressure oil to the swivel parking brake to switch the swivel parking brake from the brake state to the brake release state, a pilot-activated switching valve (connecting valve 45) is used, and pilot pressure for switching the switching valve is configured to be output when an operation other than a single driving operation is performed, that is, a swivel operation, a working part operation, or a combined driving operation between a travel operation and a workpiece operation is performed, thereby making the swivel parking brake in the brake release state when an operation other than a single driving operation is performed (see, for example, Patent Document 1).
On the other hand, some working machines provided with a plurality of hydraulic actuators such as left and right travel motors, swivel motors, working hydraulic actuators, etc., for example, the aforementioned working machines such as hydraulic excavators, are provided first and second hydraulic pumps as hydraulic supply sources of these plurality of hydraulic actuators, and are provided with pilot-actuated straight travel valves that switch the supply oil passages connected to these first and second hydraulic pumps (see, for example, Patent Document 2). The straight travel valve is configured to switch a supply line to supply the oil discharged by the first or second hydraulic pump to the left or right one of the travel motors and to supply the oil discharged by the other hydraulic pump to the other travel motor when the travel operation is performed alone, and to supply the oil discharged by one hydraulic pump to the left and right travel motors and the oil discharged by the other pump to other hydraulic actuators when a combined travel motion combining the travel operation and operations performed by other hydraulic actuators, so that the same amount of pressure oil can be supplied to the left and right travel motor to ensure travel straightness. In the case of providing such a pilot-actuated straight travel valve, a valve that outputs pilot pressure to the straight travel valve based on a travel operation or other hydraulic actuator operation is required, and in Patent Document 2, an electromagnetic proportional straight-travel control valve controlled by a controller is used.
In a working machine provided with a swivel parking brake as described above, as described in Patent Document 1, when performing an operation other than the travel operation alone, a pilot pressure is output to a switching valve that supplies pressure oil to the swivel parking brake, and the switching valve is switched by the pilot pressure to put the swivel parking brake in a brake release state, so that the swivel parking brake can be put into a brake release state not only when performing the swivel operation but also when operating the working part. However, in Patent Document 1, when outputting the pilot pressure to a switching valve when an operation other than the only travel operation is performed, an auxiliary switching valve is provided in conjunction with these control valves for a travel motor and for a plurality of working hydraulic actuators (a switching valve for travel motor operation, a switching valve for boom cylinder operation, a switching valve for arm cylinder operation, and a switching valve for bucket cylinder operation), and a logical valve is provided to guide the pilot pressure passing through these auxiliary switching valves to the switching valve via a check valve or a shuttle valve, and to flow the pilot pressure to the oil tank during the only travel operation. For this reason, there is a need for a special structure control valve with an auxiliary switching valve, and thus the number of parts is large, and the circuit becomes complicated. Thus there is a problem to be solved by the present invention.
The present invention has been created for the purpose of solving the problem in view of the above actual circumstances, and the invention of claim 1 is a hydraulic control system in a working machine, which is characterized in that the working machine which includes a lower travel body having a left and right travel device, an upper swivel body freely supported by the lower travel body, and a working unit mounted on the upper swivel body, is provided with the hydraulic control system, wherein the hydraulic control system includes a left and a right travel motors that drive the left and right travel device of the lower travel body, a swivel motor for swiveling the upper swivel body, a plurality of hydraulic actuators including working hydraulic actuators for driving the front working unit, a first and second hydraulic pumps for hydraulic supply of these hydraulic actuators, a left and right travel manipulator, a swivel manipulator, and a working manipulator which are operated to drive the left and right travel motors, the swivel motor, and the working hydraulic actuators respectively, a pilot-actuated straight travel valve switching connections of supply oil passages between the first and second hydraulic pumps and various hydraulic actuators, a swivel parking brake for braking swivel of the upper swivel body, and a pilot-actuated brake switch valve for supplying pressure oil to the swivel parking brake and switching to a brake-release state from a brake state,
According to the invention of claim 1, it is possible to put the swivel parking brake in the brake release state even when not only the swivel manipulator but also the working manipulator is operated, and since the common electromagnetic valve that outputs the pilot pressure to the brake switch valve to put the swivel parking brake in the brake release state is common to the common electromagnetic valve that outputs the pilot pressure to the straight travel valve, it is possible to contribute to reducing the number of components and simplifying the circuit without requiring a separate dedicated valve or complex circuit to switch the brake switch valve.
Embodiments of the present invention will be described below with reference to the drawings.
The first hydraulic pump 8 is connected to a first pump line A via a straight travel valve 20 of a neutral position N (to be described later), and is connected to a left-travel direction-switching valve 21 via a left-travel supply oil passage 18. On the other hand, the second hydraulic pump 9 is connected to a second pump line B, and is connected to a right-travel direction-switching valve 22 via the straight travel valve 20 of the neutral position N and a right-travel supply oil passage 19.
The straight travel valve 20 is a pilot-actuated two-position switch valve and is configured to switch to an actuation position X by inputting pilot pressure P (P=P1) greater than or equal to a first set pressure P1 that is input to a pilot port 20a but to a neutral position N in which the pilot P input to the pilot port 20a is less than the first set pressure P1 (P<P1) (including a case where the pilot pressure is not input). Moreover, when the straight travel valve 20 is located in the neutral position N, the discharge oil of the first hydraulic pump 8 is supplied to the first pump line A and the left-travel direction-switching valve 21, and the discharge oil of the second hydraulic pump 9 is supplied to the second pump line B and the right-travel direction-switching valve 22. When the straight travel valve 20 is located in the actuation position X, the discharge oil of the first hydraulic pump 8 is supplied to the left and right-travel direction-switching valves 21, 22, and the discharge oil of the second hydraulic pump 9 is supplied to the first and second pump lines A and B. As described later, the straight travel valve 20 is controlled to be located at the actuation position X at the time of a combined travel operation in which the left and right travel manipulators (not shown) is operated and at least one of a swivel manipulator, a boom manipulator, a stick manipulator, and a bucket manipulator is operated, and to be located at the neutral position N in a case except the combined travel operation. Therefore, when the left and right travel manipulators are operated only in a separate travel operation, the discharge oil of the first and second hydraulic pumps 8 and 9 is supplied to the left and right travel motors 12 and 13 via the left and right travel direction-switching valves 21 and 22, respectively, through the travel straight valve 20 located at the neutral position N, so that the supply flow rates to the two travel motors 12 and 13 are equal. On the other hand, during the combined travel operation, the discharge oil of the first hydraulic pump 8 is distributed only by the left and right travel motors 12 and 13 and can be equally supplied to the two travel motors 12 and 13 in the supply flow rates, and the discharge oil of the second hydraulic pump 9 can be supplied to the swivel motor 14, the boom cylinder 15, the stick cylinder 16 and the bucket cylinder 17. In the following description, the boom manipulator, the stick manipulator, and the bucket manipulator may also be referred to as working manipulators.
Furthermore, 23 is a common electromagnetic proportional valve (corresponding to the common electromagnetic valve of the present invention) connected via the pilot oil passage 24 to the pilot port 20a of the straight travel valve 20, and the common electromagnetic proportional valve 23 outputs a pilot pressure to the pilot port 20a of the straight travel valve 20 based on a control signal from the controller 25 which will be described later. Furthermore, from the pilot oil passage 24, a branch pilot oil passage 24a leading to the pilot port 26a of the brake switch valve 26 described later is branched and formed, and the pilot pressure output from the common electromagnetic proportional valve 23 is also supplied to the pilot port 26a of the brake switch valve 26.
The left and right travel direction-switching valves 13, 14 are spool valves for controlling the supply/discharge flow rate of the left and right travel motors 12 and 13 and for switching the supply/discharge direction, respectively, having forward side and backward side pilot ports 21a, 21b, 22a and 22b. These forward side/backward side pilot ports 21a, 21b, 22a, and 22b are respectively connected with a left travel forward side electromagnetic proportional valve, a left travel backward side electromagnetic proportional valve, a right travel forward side electromagnetic proportional valve, and a right travel backward side electromagnetic proportional valve 57a, 57b, 58a, and 58b (as shown in
On the other hand, branches from the first pump line A connected to the first hydraulic pump 8 are formed so that the boom main-side supply oil passage 27, the stick sub-side supply oil passage 28 and the bucket supply oil passage 29 are parallel to each other, and branches from the second pump line B connected to the second hydraulic pump 9 are formed so that the boom sub-side supply oil passage 30, the swivel supply oil passage 31 and the stick main-side supply oil passage 32 are parallel to each other. The boom main-side supply oil passage 27 and the boom sub-side supply oil passage 30 are oil passages for connecting the first and second hydraulic pumps 8 and 9 to the boom direction-switching valve 34 to be described later, the swivel supply oil passage 31 is an oil passage for connecting the second hydraulic pump 9 to the swivel direction-switching valve 33, the stick main-side supply oil passage 32 and the stick sub-side supply oil passage 28 are oil passages for connecting the second and first hydraulic pumps 9 and 8 to the stick direction-switching valve 35, respectively, and the bucket supply oil passage 29 is an oil passage for connecting the first hydraulic pump 8 to the bucket direction-switching valve 36.
A stick flow control valve 38 for controlling the supply flow rate from the first hydraulic pump 8 to the stick direction-switching valve 35 is disposed in the stick sub-side supply oil passage 28, and the boom sub-side supply oil passage 30 is provided with a boom flow-rate control valve 39 for controlling the supply flow rate from the second hydraulic pump 9 to the boom direction-switching valve 34. The stick flow rate control valve 38 and the boom flow-rate control valve 39 are poppet valves which are pilot operated by a stick flow-rate control electromagnetic proportional valve 63 and a boom flow-rate control electromagnetic proportional valve 64 (shown in
The boom direction-switching valve 34 can be supplied the pressure oil from the first hydraulic pump 8 via the boom main-side supply oil passage 27 and the pressure oil from the second hydraulic pump 9 via the boom sub-side supply oil passage 30, and the boom direction switching valve 34 is supplied the pressure oil from the second hydraulic pump 9 in a state (including an off state) in which the flow rate is controlled by the boom flow rate control valve 39 provided in the boom sub-side supply oil passage 30. Further, the stick direction-switching valve 35 can be supplied the pressure oil from the second hydraulic pump 9 via the stick main-side supply oil passage 32 and the pressure oil from the first hydraulic pump 8 via the stick sub-side supply oil passage 28, and the pressure oil from the first hydraulic pump 8 is supplied to the stick direction-switching valve 35 in a state (including an off state) in which the flow rate is controlled by the stick flow-rate control valve 38 provided in the stick sub-side supply oil passage 28.
Next, the explanation is provided about the boom, swivel, stick and bucket direction-switching valves 23 to 26.
The swivel direction-switching valve 33 is a spool valve for controlling the supply/discharge flow rates to/from the swivel motor 14 as well as switching its supply/discharge directions, and has left and right swivel side pilot ports 33a and 33b respectively connected to swivel left/right swivel electromagnetic proportional valves 59a, 59b (shown in
Here, the swivel directional switch valve 33 and the swivel motor 14 are connected via a pair of supply/discharge lines 40a, 40b, which are connected with overload relief valves 41a, 41b and negative pressure prevention check valves 42a, 42b, respectively, so that shock and swing back can be mitigated when the swivel stops.
In addition, the boom direction-switching valve 34 is a spool valve that controls the supply/discharge flow rate of the boom cylinder 15 and switches the supply/discharge flow direction at the same time, and comprises an extended side and a reduced side pilot ports 34a, 34b, where the extended side and the reduced side pilot ports 34a, 34b are connected with a boom extended side and a reduced side electromagnetic proportional valves 60a, 60b (shown in
In addition, the stick direction-switching valve 35 is a spool valve that controls the supply/discharge flow rate for the stick cylinder 16 and switches the supply/discharge direction at the same time, and comprises an extended side and a reduced side pilot ports 35a, 35b, where the extended side and the reduced side pilot ports 35a, 35b are connected with an extended side and a reduced side electromagnetic proportional valves 61a, 61b (shown in
In addition, the bucket direction-switching valve 36 is a spool valve that controls the supply/discharge flow rate of the bucket cylinder 17 and switches the supply/discharge flow direction, and comprises an extended side and a reduced side pilot ports 36a, 36b, and the extended side and the reduced side pilot ports 36a, 36b are connected to an extended side and a reduced side electromagnetic proportional valves 62a, 62b (shown in
On the other hand, the swivel motor 14 is provided with a swivel parking brake 46 to prevent the upper swivel body 3 from swiveling due to the weight of the front working unit 4 or the like when parking on a slope or the like. The swivel parking brake 46 is configured to be in a brake state in which the brake is applied to an output shaft 14a of the swivel motor 14 by the applied force of a spring 46b when the pressure oil is not supplied to the oil release chamber 46a, but in a brake-released state in which the brake is released when the pressure oil is supplied to the oil release chamber 46a.
Furthermore, 47 is a brake oil supply path from the pilot pump 10 to the release oil chamber 46a of the swivel parking brake 46, and the brake oil supply path 47 is provided with a brake switch valve 26. The brake switch valve 26 is a pilot-actuated two-position switch valve, and when no pilot pressure is input to the pilot port 26a, the brake switch valve 26 is located at a neutral position N in which the oil of the release oil chamber 46a flows to the oil tank 11, but when the pilot pressure greater than or equal to a second set pressure P2 preset in advance (P≥P2) is input, the pressure oil supplied from the pilot pump 10 is switched to an actuation position X supplied to the oil release chamber 46a. Then, when the brake switch valve 26 is located at the neutral position N, the swivel parking brake 46 is in a brake state because the pressure oil is not supplied to the release oil chamber 46a, but the swivel parking brake 46 is configured to be in the brake release state when the brake switch valve 26 is switched to the actuation position X and the pressure oil is supplied to the release oil chamber 46a.
Here, the pilot pressure output from the common electromagnetic proportional valve 23 is input to the pilot port 26a of the brake switch valve 26 as described above, and the second set pressure P2 required for switching the brake switch valve 26 to the neutral position N from the actuation position X is set to a lower pressure (P2<P1) than the first set pressure P1 required for switching the straight travel valve 20 from the neutral position N to the actuation position X. However, if the pilot pressure P is not output from the common electromagnetic proportional valve 23, the brake switch valve 26 and the straight travel valve 20 are both located in the neutral position N, and if the pilot pressure P is greater than or equal to the second set pressure P2 and less than the first set pressure P1 (P2≤P<P1), the brake switch valve 26 switches to the actuation position X but the straight travel valve 20 is located in the neutral position N, and if the pilot pressure P is greater than or equal to the first set pressure P1 (P≥P1), the brake switch valve 26 and the straight travel valve 20 are both configured to switch to the actuation position X.
In
On the other hand, as shown in the block diagram of
Then, the controller 25 performs various controls such as an oil supply and discharge flow control for each hydraulic actuator (the left and right travel motors 12, 13, the swivel motor 14, the boom cylinder 15, the stick cylinder 16, and the bucket cylinder 17), a discharge flow control of the first and second hydraulic pumps 8, 9, a switch control of the straight travel valve 20, a brake control of the swivel motor 14 by the swivel parking brake 46, etc., based on the operation detection signals input from each operation detection means 51-56 and the pressure sensor, among which the switch control of the straight travel valve 20 and the brake control of the swivel parking brake 46 will be described below.
As described above, the straight travel valve 20 switches from the neutral position N to the actuation position X in response to the pilot pressure output from the common electromagnetic proportional valve 23, and the brake switch valve 26 that supplies and stops supplying the pressure oil to the swivel parking brake 46 also switches from the neutral position N to the actuation position X in response to the pilot pressure output from the common electromagnetic proportional valve 23. That is, since the controller 25 is configured to control the output pilot pressure of the common electromagnetic proportional valve 23 to perform the switch control of the straight travel valve 20 and the brake control of the swivel parking brake 46, the control of the common electromagnetic proportional valve 23 performed by the controller 25 will be described below based on the flowchart diagram of
When controlling the common electromagnetic proportional valve 23, the controller 25 first determines whether or not the left and right (both left and right) travel manipulators are operated (step S1).
If the determination of step S1 is “Yes”, that is, the left and right travel manipulators are operated, then it is determined whether at least one of the swivel, boom, stick, and bucket manipulators is operated (step S2).
Then, if the determination of the step S2 is “Yes”, that is, at least one of the swivel, boom, stick, and bucket manipulators is operated, the controller 25 outputs a control signal to the common electromagnetic proportional valve 23 to output a pilot pressure P (P≥P1) of the first set pressure P1 or more (step S3). This switches both the straight travel valve 20 and the brake switch valve 26 to the actuation position X, as previously described.
However, when both the left and right travel manipulators are operated (“Yes” in the determination of step S1), and at least one of the swivel, boom, stick, and bucket manipulators is operated (“Yes” in the determination of step S2), that is, when the combined travel operation is operated, the straight travel valve 20 and the brake switch valve 26 are both controlled to switch to the actuation position X. Then, by switching the straight travel valve 20 to the actuation position X, the discharged oil of the first hydraulic pump 8 can be distributed only by the left and right travel motors 12 and 13 to equalize the flow rates supplied to both the travel motors 12 and 13, while the discharged oil of the second hydraulic pump 9 can be supplied to any of the hydraulic actuators of operated manipulators of the swivel motor 14, the boom cylinder 15, the stick cylinder 16, and the bucket cylinder 17, thereby ensuring the flow rate supplied to these hydraulic actuators.
In addition, by switching the brake switch valve 26 to the actuation position X, the pressure oil is supplied to the release oil chamber 46a of the swivel parking brake 46, and the swivel parking brake 46 becomes the brake release state of the swivel motor 14. As a result, the swivel parking brake 46 is deactivated not only when the swivel manipulator is operated, but also when any of manipulators of the boom, stick, or bucket manipulators is operated. In this way, by releasing the swivel parking brake 46 in the operation of the boom cylinder 15, the stick cylinder 16, and the bucket cylinder 17 not only during swiveling, but also during stopping the swivel, the concern can be avoided that the swivel parking brake 46 will be overloaded when the boom cylinder 15, the stick cylinder 16, and the bucket cylinder 17 are activated while the swivel parking brake 46 is in a brake state.
On the other hand, if the determination of step S2 is “NO”, that is, any of manipulators in the swivel, boom, stick, or bucket manipulators is not operated, the controller 25 does not output the control signal of the pilot pressure output to the common electromagnetic proportional valve 23 (step S4). As a result, this maintains both the straight travel valve 20 and the brake switch valve 26 in the neutral position N, as previously described.
However, if the left and right travel manipulators are manipulated (“Yes” in the determination of step S1), and neither of the swivel, boom, stick, or bucket manipulators is manipulated (“NO” in the determination of step S2), that is, when the travel is operated alone, the straight travel valve 20 and the brake switch valve 26 are both controlled to be located in the neutral positions N. Then, by positioning the straight travel valve 20 in the neutral position N, the discharged oil of the first hydraulic pump 8 is supplied to the left travel motor 12, and the discharged oil of the second hydraulic pump 9 is supplied to the right travel motor 13, respectively, so that the flow rates supplied to the two travel motors 12, 13 can be equalized. In addition, since the brake switch valve 26 is located at the neutral position N, the pressure oil is not supplied to the oil release chamber 46a for the swivel parking brake 46, and the swivel parking brake 46 is in the brake state in which braking is applied to the swivel motor 14. This makes it possible to reliably prevent the upper swivel body 3 from swiveling when it travels alone.
In addition, if the determination of step S1 is “NO”, that is, the left and right travel manipulators are not manipulated (including a case where the left and right travel manipulators are manipulated), then it is determined whether or not at least one of the swivel, boom, stick, and bucket manipulation is operated (step S5).
Then, if the determination of step S5 is “YES”, that is, at least one of the swivel, boom, stick, and bucket manipulators is not operated, the controller 25 outputs a control signal to the common electromagnetic proportional valve 23 to output the pilot pressure P (P2≤P<P1) that is greater than or equal to the second set pressure P2 and less than the first set pressure P1 (step S6). This causes the straight travel valve 20 to be located in the neutral position N and the brake switch valve 26 to switch to the actuation position X, as previously described.
However, if the left and right travel manipulators are not operated (“NO” in the determination of step S1), and at least one of the swivel, boom, stick, and bucket manipulators is operated (“Yes” in the determination of step S5), the straight travel valve 20 is located in the neutral position N and the brake switch valve 26 is controlled to switch to the actuation position X. Then, by locating the straight travel valve 20 at the neutral position N, the discharged oil of the first and second hydraulic pumps 8, 9 is respectively supplied to hydraulic actuators (the swivel motor 14, the boom cylinder 15, the stick cylinder 16, and the bucket cylinder 17) operated by the manipulators via the first and second boom line A, B. In addition, when the brake switch valve 26 is switched to the actuation position X, the pressure oil is supplied to the release oil chamber 46a of the swivel parking brake 46, and the swivel parking brake 46 enters a brake release state to release the brake of the swivel motor 14. This avoids the concern that the boom cylinder 15, the stick cylinder 16, and the bucket cylinder 17 will be deactivated during the operations of the boom cylinder 15, the stick cylinder 16, and the bucket cylinder 17, as in the case of the aforementioned step S3, and that the boom cylinder 15, the stick cylinder 16, and the bucket cylinder 17 will be under overload when the boom cylinder 15, the stick cylinder 16, and the bucket cylinder 17 are actuated while the swivel parking brake 46 is in the brake state.
On the other hand, if the determination of step S5 is “NO”, that is, any of manipulators in the swivel, boom, stick, or bucket manipulators is not operated, the controller 25 proceeds to the processing of step S4. In this step S4, as mentioned above, the control signal of the pilot pressure output is not output from the controller 25 to the common electromagnetic proportional valve 23, so that the straight travel valve 20 and the brake switch valve 26 are both maintained in the neutral positions N.
However, if the left and right travel manipulators are not operated (“NO” in the determination of step S1), and neither manipulator of the swivel, boom, stick, or bucket manipulators is operated (“NO” in the determination of step S5), the straight travel valve 20 and the brake switch valve 26 are both controlled to be located in the neutral positions N. And because the brake switch valve 26 is located in the neutral position N, the swivel parking brake 46 is in the brake state, and the upper swivel body 3 can be reliably prevented from swiveling when parking on a slope or the like.
Here,
In addition,
In the present form configured as described, the hydraulic excavator 1 comprises a lower travel body 2 with a left and right travel device, an upper swivel body 3 that is supported on the lower traveling body 2 in a free swivel manner, and a front working unit 4 that is mounted on the upper swivel body 3; and a hydraulic control system of the hydraulic excavator 1 is provided with a left and a right travel motors 12, 13 that drive the left and right travel device of the lower travel body 2, a swivel motor 14 for swiveling the upper swivel body 3, a plurality of hydraulic actuators including working hydraulic actuators 15 to 17 for driving the front working unit 4 (the boom cylinder 15, the stick cylinder 16, the bucket cylinder 17), the first and second hydraulic pumps 8 and 9 for hydraulic supply of these hydraulic actuators, the left and right travel manipulator, the swivel manipulator, and the working manipulator (the boom manipulator, the stick manipulator, the bucket manipulator) operated to drive the left and right travel motors 12, 13, the swivel motor 14, and the working hydraulic actuators 15-17 respectively, a pilot-actuated straight travel valve 20 switching connections of supply oil passages between the first and second hydraulic pumps 8, 9 and various hydraulic actuators (a left travel supply oil passage 18, a right travel supply oil passage 19, the first pump line A (the boom main side supply oil passage 27, the stick sub-side supply oil passage 28, and the bucket supply oil passage 29 which are connected to the first pump line A), the pump line B (the boom sub-side supply oil passage 30, the swivel supply oil passage 31, and the stick main-side supply oil passage 32 which are connected to the second pump line B)), the swivel parking brake 46 for braking the swivel of the upper swivel body 3, and a pilot-actuated brake switch valve 26 for supplying the pressure oil to the swivel parking brake 46 and switching to the brake-release state from the brake state. The straight travel valve 20 is configured to, by supplying a pilot pressure greater than or equal to the first set pressure P1, switch from a neutral position N at which the first and second hydraulic pumps 8, 9 supply the discharge oil from one hydraulic pump (in this embodiment, the first hydraulic pump 8) to the left travel motor 12 and supply the discharge oil from the other hydraulic pump (in this embodiment, the second hydraulic pump 9) to the right travel motor 13, to an actuation position X at which the discharge oil from the one hydraulic pump 8 is supplied to the left and right travel motors 12 and 13, and the discharge oil from the other hydraulic pump 9 is supplied to the swivel motor 14 and the working hydraulic actuators 15 to 17. The brake switch valve 26 is configured to switch from a neutral position N at which the swivel parking brake 46 is in a brake state to an actuation position X at which the swivel parking brake 46 is in a brake release state by supplying a pilot pressure of the second set pressure P2 lower than the first set pressure P1 (P2<P1). In this case, the straight travel valve 20 and the brake switch valve 26 are supplied a pilot pressure from the common electromagnetic proportional valve 23, and the controller 25 for controlling the common electromagnetic proportional valve 23 is provided. Then, the controller 25 controls the common electromagnetic proportional valve 23 without operating either the left and right travel manipulators, the swivel manipulator or the working manipulator, and not to output the pilot pressure when the left and right travel manipulators are operated and neither the swivel manipulator nor the working manipulator is operated, and to output the pilot pressure greater than or equal to the first set pressure P1 when the left and right travel manipulators are operated and at least one of the swivel manipulator and the working manipulator is operated, and to output the pilot pressure greater than or equal to the second set pressure P2 but less than the first set pressure P1 when the left and right travel manipulators are not operated and at least one of the swivel manipulator and the working manipulator is operated.
However, when neither of the left and right travel manipulators, the swivel manipulator, and the working manipulator is operated, the pilot pressure is not output from the common electromagnetic proportional valve 23, and the straight travel valve 20 and the brake switch valve 26 are both located in the neutral positions N. The swivel parking brake 46 is then maintained in the brake state with the brake switch valve 26 located in the neutral position N.
In addition, when the left and right travel manipulators are operated, and neither the swivel manipulator nor the working manipulator is operated; that is, when the only travel operation is performed, the pilot pressure is not output from the common electromagnetic proportional valve 23, and the straight travel valve 20 and the brake switch valve 26 are both located in the neutral positions N. Then, with the straight travel valve 20 located in the neutral position N, the discharged oil of the first hydraulic pump 8 is supplied to the left travel motor 12 and the discharged oil of the second hydraulic pump 9 is supplied to the right travel motor 13, respectively, so that the flow rates supplied to the two travel motors 12, 13 can be equalized. Also, the swivel parking brake 46 is maintained in the brake state with the brake switch valve 26 located in the neutral position N.
On the other hand, when the left and right travel manipulators are operated, and at least one of the swivel manipulator and the working manipulator is operated; that is, when the travel combined operation is performed, the pilot pressure of the first set pressure P1 or more is output from the common electromagnetic proportional valve 23, and the straight travel valve 20 and the brake switch valve 26 are both switched to the actuation positions X. Then, by switching the straight travel valve 20 to the actuation position X, the discharged oil of one hydraulic pump 8 can be distributed only by the left and right travel motors 12 and 13 to equalize the flow rates supplied to both the travel motors 12 and 13, and the discharged oil of the other hydraulic pump 9 can be supplied to the swivel motor 14 and the working hydraulic actuators 15 to 17 operated by the manipulators, thereby ensuring the flow rates supplied to these hydraulic actuators 14, 15 to 17. In addition, by switching the brake switch valve 26 to the actuation position X, the swivel parking brake 46 is in the brake release state, whereby the swivel parking brake 46 can be deactivated not only during the swivel but also during the operation of the working hydraulic actuators 15-17 even when the swivel is stopped.
Furthermore, when the left and right travel manipulators are not operated, and at least one of the swivel manipulator and the working manipulator is operated, the pilot pressure greater than or equal to the second set pressure P2 and less than the first set pressure P1 is output from the common electromagnetic proportional valve 23, the straight travel valve 20 is located in the neutral position N, and the brake switch valve 26 switches to the actuation position X. Then, with the straight travel valve 20 located in the neutral position N, the discharged oil of the first and second hydraulic pumps 8, 9 is supplied to the swivel motor 14 and the working hydraulic actuators 15-17 operated by the manipulators via the first and second pump lines A and B respectively. In addition, by switching the brake switch valve 26 to the actuation position X, the swivel parking brake 46 is in the brake release state, whereby the swivel parking brake 46 can be deactivated not only during the swivel but also during the operation of the working hydraulic actuators 15-17 even when the swivel is stopped.
In this way, in the present embodiment, the common electromagnetic proportional valve 23, which is a pilot pressure output electromagnetic valve for switching the straight travel valve 20 from the neutral position N to the actuation position X, is also used as the pilot pressure output electromagnetic valve for switching the brake switch valve 26 from the neutral position N to the actuation position X. Therefore, a pilot pressure output electromagnetic valve dedicated to the brake switch valve 26 is not required, and a common of component can be realized. In this case, the second set pressure P2, which is the pilot pressure required for switching the brake switch valve 26, is set to a lower pressure (P2<P1) than the first set pressure P1, which is the pilot pressure required for switching the straight travel valve 20, so that depending on the operation of the left and right travel, swivel, and working (boom, stick, bucket) manipulators, by controlling the output pilot pressure from the common electromagnetic proportional valve 23 to be greater than or equal to the second set pressure P2 and less than the first set pressure P1, it is possible to switch only the brake switch valve 26 to the actuation position X while maintaining the straight travel valve 20 in the neutral position N. On the other hand, by controlling the output pilot pressure from the common electromagnetic proportional valve 23 to be greater than or equal to the first set pressure P1, the straight travel valve 20 and the brake switch valve 26 can be switched to the actuation positions X.
It should be noted that when the left and right travel manipulators are operated, and at least one of the swivel manipulator and the working manipulator is operated, that is, when the travel combination operation is performed, it is necessary to switch the straight travel valve 20 to the actuation position X, and to switch the brake switch valve 26 to the actuation position X in order to put the swivel parking brake 46 in the brake release state, but by controlling the output pilot pressure from the common electromagnetic proportional valve 23 to be greater than or equal to the first set pressure P1, the straight travel valve 20 and the brake switch valve 26 can be switched to the actuation positions X at the same time.
However, by only controlling the output pilot pressure from the common electromagnetic proportional valve 23, it is possible to put the swivel parking brake 46 into the brake release state during the operations of the working hydraulic actuators 15-17 not only during the swivel, but also during stopping the swivel, without separately providing dedicated components and complex circuits, which can contribute to reducing the number of components and simplifying the circuit.
In addition to this, the straight travel valve 20, which shares the brake switch valve 26 and the common electromagnetic proportional valve 23, switches the connection between the first hydraulic pump 8, the second hydraulic pump 9, and the supply oil passage for each hydraulic actuator (the left traveling supply oil passage 18, the right traveling supply oil passage 19, the boom main-side supply oil passage 27, the stick sub-side supply oil passage 28, the bucket supply oil passage 29, the boom sub-side oil supply passage 30, the swivel oil supply passage 31, and the main-side oil supply passage 32 for the stick), and is not a directional switch valve or a flow control valve that controls the flow rate of the supply and discharge to the hydraulic actuator, so that the electromagnetic proportional valve that outputs the pilot pressure to these direction-switching valves or flow control valves and the electromagnetic proportional valve that outputs the pilot pressure to the brake switch valve, and thus it is possible to avoid a concern that the pilot pressure output for switching the brake switch valve will affect the control of the supply and discharge flow to the hydraulic actuator, as in the case of sharing the valve.
It should be noted that the present invention is not limited to the above-described embodiments. In the above-described embodiments, the boom cylinder and the supply flow control to the stick cylinder are configured using a boom direction switching valve, a stick direction switching valve, and a boom flow control valve and a stick flow control valve provided in the sub-side supply oil channel. However, without being limited to the circuits of such a configuration, the circuit may be, for example, a circuit that does not provide a flow control valve, and performs flow control using only a boom direction switching valve and a stick direction switching valve.
It should be note that the present invention is not limited to the above embodiments. In the above embodiments, the flow control to the boom cylinder and the stick cylinder is performed by using the boom direction switching valve and the stick direction switching valve arranged on the main-side supply oil passage, and the boom flow control valve and the stick flow control valve arranged on the sub-side supply oil passage. However, the present invention is not limited to such a circuit. For example, the flow control may be performed only by the boom direction switching valve and the stick direction switching valve without the flow control valve.
The present invention is available for use in the hydraulic control system of working machine such as hydraulic excavator.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-024912 | Feb 2023 | JP | national |
