Hydraulic circuit of construction machine, track deviation correcting device, and track deviation correcting method

Abstract

The application discloses an engineering machinery hydraulic circuit, a track deviation rectifying device and a track deviation rectifying method. The engineering machinery hydraulic circuit comprises a main pump, a first main oil path, a second main oil path, a third main oil path, a fourth main oil path, a first control valve, a second control valve, a first proportional reversing valve, a second proportional reversing valve, a left traveling motor and a right traveling motor. The first proportional reversing valve is arranged on the first main oil path to adjust the flow of the first main oil path flowing into the left traveling motor. The second proportional reversing valve is arranged on the third main oil path to adjust the flow of the third main oil path flowing into the right traveling motor. In the engineering machinery hydraulic circuit, the track deviation rectifying device and the track deviation rectifying method, the flow on the first main oil path and the third main oil path can be controlled by controlling the position of the proportional reversing valve, so that the traveling of the left traveling motor and the right traveling motor is adjusted, automatic deviation rectification is realized, manual operation is not needed, and the labor intensity of an operator is reduced.

Description

Technical Field

[0001] This application relates to the field of basic construction technology, and in particular to a hydraulic circuit for engineering machinery, a track correction device, and a track correction control method. Background Technology

[0002] Currently, tracked construction machinery such as horizontal directional drilling rigs and excavators are powered by left and right travel motors to move. Ideally, when the operator operates the left and right travel control levers simultaneously, the left and right travel motors should work synchronously, and the tracked walking mechanism should move in a straight line. However, tracked construction machinery often experiences deviation from its intended path during straight-line movement due to various reasons. For example, if the terrain traversed by the left and right travel motors differs, or if their volumetric efficiencies differ, deviation may occur.

[0003] When tracked construction machinery appeared, the operator needed to manually adjust the movement trajectory by relying on the operator's sense of control. This increased the operator's workload, made adjustments inconvenient, and the adjustment effect heavily depended on the operator's experience. Summary of the Invention

[0004] In view of this, the purpose of this application is to provide a hydraulic circuit for engineering machinery, a track correction device, and a track correction control method to reduce the difficulty of operating tracked engineering machinery and make adjustment more convenient and simple.

[0005] To achieve the above objectives, this application provides a hydraulic circuit for engineering machinery, including a main pump, a first main oil circuit, a second main oil circuit, a third main oil circuit, a fourth main oil circuit, a first control valve, a second control valve, a first proportional directional valve, a second proportional directional valve, a first actuator, and a second actuator. The main pump is used to supply oil to the first actuator through the first main oil circuit or the second main oil circuit. The main pump is also used to supply oil through the third main oil circuit or the fourth main oil circuit. The first control valve and the second control valve are connected to the main pump, and the first control valve is connected to the first main oil circuit. The first main oil circuit and the second main oil circuit are connected to control whether the main pump supplies oil to the first actuator through the first main oil circuit or the second main oil circuit. The second control valve is connected to the third main oil circuit and the fourth main oil circuit to control whether the main pump supplies oil to the second actuator through the third main oil circuit or the fourth main oil circuit. The first proportional directional valve is located on the first main oil circuit to regulate the flow rate of the first main oil circuit into the first actuator. The second proportional directional valve is located on the third main oil circuit to regulate the flow rate of the third main oil circuit into the second actuator.

[0006] Optionally, the first actuator is a left travel motor, the second actuator is a right travel motor, and the main pump is used to supply oil to the left travel motor through the first main oil circuit or the second main oil circuit to make the left travel motor rotate forward or reverse, respectively. The main pump is also used to supply oil through the third main oil circuit or the fourth main oil circuit to make the right travel motor rotate forward or reverse, respectively.

[0007] Optionally, the first proportional directional valve is used to directly connect the first end of the left travel motor and the first control valve, or to connect the first end of the left travel motor and the first control valve through a throttle valve; the second proportional directional valve is used to directly connect the third end of the right travel motor and the second control valve, or to connect the third end of the right travel motor and the second control valve through a throttle valve.

[0008] Optionally, the first proportional directional valve includes a first directional port, a second directional port, and a third directional port. The first directional port is connected to the first control valve, and the third directional port is connected to the first end of the left travel motor. The first proportional directional valve includes a first directional position and a second directional position. In the first directional position, the first directional port and the third directional port are directly connected, and the second directional port is disconnected from both the first and third directional ports. In the second directional position, the first directional port and the third directional port are connected through a throttle valve, and the first directional port and the second directional port are connected.

[0009] The second proportional directional valve includes a fourth directional port, a fifth directional port, and a sixth directional port. The fourth directional port is connected to the second control valve, and the sixth directional port is connected to the third end of the right travel motor. The second proportional directional valve includes a third directional position and a fourth directional position. In the third directional position, the fourth and sixth directional ports are directly connected, and the fifth directional port is disconnected from both the fourth and sixth directional ports. In the fourth directional position, the fourth and sixth directional ports are connected through a throttle valve, and the fourth and fifth directional ports are connected.

[0010] Optionally, the valve core displacement response of the first proportional directional valve and the second proportional directional valve is a ramp response; or, the first main oil circuit and the third main oil circuit are directly connected through a connecting oil circuit.

[0011] This application also provides a track correction device for controlling the hydraulic circuit of the aforementioned construction machinery. The track correction device includes a position detection element, a tilt angle detection element, and a control module. The position detection element is used to detect the initial position (x) of the construction machinery. t0 ,y t0) and current position (x) t '1,y t '1) The tilt angle detection element is used to detect the initial azimuth angle of the engineering machinery. The control module is used to determine the initial position (x) t0 ,y t0 ), the current position (x) t '1,y t '1) and the initial azimuth angle Calculate the shortest distance deviation L between the current position and the theoretical trajectory, and determine whether the absolute value of the shortest distance deviation L is less than or equal to the deviation threshold. If the absolute value of the shortest distance deviation L is greater than the deviation threshold, control the first proportional directional valve to adjust the flow rate of the first main oil circuit into the left travel motor or control the second proportional directional valve to adjust the flow rate of the third main oil circuit into the right travel motor.

[0012] Optionally, the control module determines the initial position (x) based on the initial position (x). t0 ,y t0 ), the current position (x) t '1,y t '1) and the initial azimuth angle When calculating the shortest distance deviation L between the current position and the theoretical trajectory, it is specifically used for: according to the formula Calculate the current azimuth angle of the current position. And according to the formula Calculate the shortest distance deviation L, where,

[0013] The control module determines whether the absolute value of the shortest distance deviation L is less than or equal to the deviation threshold, and controls the first proportional directional valve to adjust the flow rate of the first main oil circuit into the left travel motor or controls the second proportional directional valve to adjust the flow rate of the third main oil circuit into the right travel motor when the absolute value of the shortest distance deviation L is greater than the deviation threshold. Specifically, it determines whether the shortest distance deviation L is less than or equal to the deviation threshold and greater than or equal to the negative value of the deviation threshold. If not, it determines whether the shortest distance deviation L is greater than the deviation threshold. When the shortest distance deviation L is greater than the deviation threshold, it controls the first proportional directional valve to be in a state where the first end of the left travel motor and the first control valve are connected through a throttle valve. When the shortest distance deviation L is less than the negative value of the deviation threshold, it controls the second proportional directional valve to be in a state where the third end of the right travel motor and the second control valve are connected through a throttle valve.

[0014] The track correction device also includes a joystick detection element, which is used to detect the movement of the joystick. The control module is also used to determine whether the tracked walking mechanism is moving in a straight line based on the movement of the joystick, and to perform correction control when the tracked walking mechanism is moving in a straight line.

[0015] This application also provides a track correction device for controlling tracked construction machinery equipped with the aforementioned hydraulic circuit, wherein the track correction method includes:

[0016] Start the tracked walking mechanism and operate the control lever to make the tracked walking mechanism start moving. At this time, both the first proportional directional valve and the second proportional directional valve are in the initial state.

[0017] The movement of the control lever is detected, and it is determined whether the tracked walking mechanism is moving in a straight line based on the movement of the control lever. If it is, the shortest distance deviation L between the current position and the theoretical trajectory is obtained. If not, the first proportional directional valve and the second proportional directional valve remain in their initial state.

[0018] After obtaining the shortest distance deviation L, determine whether the absolute value of the shortest distance deviation L is less than or equal to the deviation threshold. If it is, continue to travel in a straight line. If not, control the switching state of the first proportional directional valve to adjust the flow rate of the first main oil circuit into the left travel motor or control the switching state of the second proportional directional valve to adjust the flow rate of the third main oil circuit into the right travel motor.

[0019] Optionally, the step of detecting the movement of the control lever and determining whether the tracked walking mechanism is moving in a straight line based on the movement of the control lever specifically includes:

[0020] Acquire the actions of the left and right joysticks;

[0021] Based on the actions of the left and right joysticks, determine whether both joysticks move forward and whether the difference in time between the left and right joysticks switching positions satisfies |T1-T2|≤△T, where △T is a preset time difference threshold.

[0022] The tracked walking mechanism is determined to be traveling in a straight line when |T1-T2|≤△T and both left and right control levers move forward; otherwise, the tracked walking mechanism is not traveling in a straight line.

[0023] Optionally, the steps for obtaining the shortest distance deviation L between the current position of the construction machinery and its theoretical trajectory specifically include:

[0024] Detect the initial position (x) of the construction machinery t0 ,y t0 ) and current position (x) t '1,y t'1) Detect the initial azimuth angle of the construction machinery. According to the formula Calculate the current azimuth angle of the current position. And according to the formula Calculate the shortest distance deviation L, where,

[0025] Optionally, determining whether the absolute value of the shortest distance deviation L is less than or equal to the deviation threshold specifically includes:

[0026] Determine whether the shortest distance deviation L is less than or equal to the deviation threshold and greater than or equal to the negative value of the deviation threshold. If yes, continue straight-line travel; otherwise, determine whether the shortest distance deviation L is greater than the deviation threshold. If the shortest distance deviation L is greater than the deviation threshold, control the first proportional directional valve to be in a state where the first end of the left travel motor and the first control valve are connected through a throttle valve. If the shortest distance deviation L is less than the negative value of the deviation threshold, control the second proportional directional valve to be in a state where the third end of the right travel motor and the second control valve are connected through a throttle valve.

[0027] Optionally, the track correction method further includes the following steps: during the movement of the tracked walking mechanism, determining whether the tracked walking mechanism is moving in a straight line; if the tracked walking mechanism is moving in a straight line, proceeding to the step of obtaining the shortest distance deviation L between the current position of the construction machinery and the theoretical trajectory; if the tracked walking mechanism is not moving in a straight line, proceeding to the step of maintaining the initial state of the first proportional directional valve and the second proportional directional valve; determining whether the tracked walking mechanism is moving in a straight line during the movement of the tracked walking mechanism specifically includes: determining whether the displacement of the left and right control levers satisfies |x1-x2|≤b; when the displacement of the left and right control levers satisfies |x1-x2|≤b, it is determined that the tracked walking mechanism is moving in a straight line; otherwise, it is determined that the tracked walking mechanism is not moving in a straight line; where x1 and x2 refer to the displacement of the left and right control levers, respectively, and b is a preset displacement threshold.

[0028] As described above, in the hydraulic circuit, track correction device, and track correction method of the engineering machinery of this application, by setting proportional directional valves on the first main oil circuit and the third main oil circuit, when the tracked walking mechanism runs off track, the flow rate on the first main oil circuit and the third main oil circuit can be controlled by controlling the position of the proportional directional valves, thereby adjusting the walking of the left and right walking motors and realizing automatic correction without manual operation, thus reducing the labor intensity of the operator. Attached Figure Description

[0029] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a schematic diagram of the structure of a hydraulic circuit for engineering machinery provided in an embodiment of this application.

[0031] Figure 2 This is a schematic diagram of the track correction device provided in one embodiment of this application.

[0032] Figure 3 for Figure 2 The diagram shows the principle of the track correction device during track correction.

[0033] Figure 4 This is a schematic flowchart of a track correction method provided in an embodiment of this application.

[0034] Figure 5 for Figure 4 A detailed flowchart of step S13 in the method shown is provided.

[0035] Figure 6 for Figure 4 A detailed flowchart of step S15 in the method shown is provided.

[0036] Figure 7 for Figure 4 A detailed flowchart of step S16 in the method shown is provided. Detailed Implementation

[0037] The specific embodiments of this application will now be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are merely some, not all, of the embodiments of this application. Based on the description of this application, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this application.

[0038] In the description of this application, unless otherwise expressly specified and limited, the terms "set," "install," "connect," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms based on the specific circumstances.

[0039] The terms “first,” “second,” “third,” etc., are used merely to distinguish numerical values ​​or elements with similar properties, rather than to indicate or imply relative importance or a specific order.

[0040] The terms “include,” “comprising,” or any other variation thereof are intended to cover non-exclusive inclusion, which includes not only the elements listed but also other elements not expressly listed.

[0041] Figure 1 This is a schematic diagram of the structure of a hydraulic circuit for engineering machinery provided in one embodiment of this application. Figure 1 As shown, this embodiment uses a tracked hydraulic system as an example to illustrate the hydraulic circuit of engineering machinery. One embodiment of the tracked hydraulic system includes a main pump 11, a first main oil circuit 13, a second main oil circuit 15, a third main oil circuit 17, a fourth main oil circuit 19, a first control valve 21, a second control valve 23, a first proportional directional valve 25, a second proportional directional valve 27, a left travel motor 29, and a right travel motor 31. The main pump 11 supplies oil to the left travel motor 29 through the first main oil circuit 13 or the second main oil circuit 15, causing the left travel motor 29 to rotate forward or reverse, respectively. The main pump 11 also supplies oil through the third main oil circuit 17 or the fourth main oil circuit 19, causing the right travel motor 31 to rotate forward or reverse, respectively. The first control valve 21 and the second control valve 23 are connected to the main pump 11. The first control valve 21 is connected to the first main oil circuit 13 and the second main oil circuit 15 to control whether the main pump 11 supplies oil to the left travel motor 29 through the first main oil circuit 13 or the second main oil circuit 15. The second control valve 23 is connected to the third main oil circuit 17 and the fourth main oil circuit 19 to control whether the main pump 11 supplies oil to the right travel motor 31 through the third main oil circuit 17 or the fourth main oil circuit 19. The first proportional directional valve 25 is provided on the first main oil circuit 13 to regulate the flow rate of the oil flowing into the left travel motor 29 from the first main oil circuit 13. The second proportional directional valve 27 is provided on the third main oil circuit 17 to regulate the flow rate of the oil flowing into the right travel motor 31 from the third main oil circuit 17.

[0042] In the tracked hydraulic system of this embodiment, by setting proportional directional valves on the first and third main oil circuits, when the tracked walking mechanism deviates from its course, the flow rate on the first and third main oil circuits can be controlled by controlling the position of the proportional directional valves, thereby adjusting the walking of the left and right walking motors and achieving automatic correction without manual operation, thus reducing the labor intensity of the operator.

[0043] In this embodiment, the left travel motor 29 includes a first end and a second end, and the right travel motor 31 includes a third end and a fourth end. One end of the first main oil circuit 13 is connected to the first end of the left travel motor 29, and the other end of the first main oil circuit 13 is connected to the first control valve 21. One end of the second main oil circuit 15 is connected to the second end of the left travel motor 29, and the other end of the second main oil circuit 15 is connected to the first control valve 21. One end of the third main oil circuit 17 is connected to the third end of the right travel motor 31, and the other end of the third main oil circuit 17 is connected to the second control valve 23. One end of the fourth main oil circuit 19 is connected to the fourth end of the right travel motor 31, and the other end of the fourth main oil circuit 19 is connected to the second control valve 23. When the pressurized oil supplied by the main pump 11 passes through the first control valve 21 and the first main oil circuit 13, it flows from the first end of the left travel motor 29 to the second end, causing the left travel motor 29 to rotate forward. At this time, the tracked travel mechanism can move forward. The oil then flows back to the oil tank from the second end through the second main oil circuit 15 and the first control valve 21. When the pressurized oil supplied by the main pump 11 passes through the first control valve 21 and the second main oil circuit 15, it flows from the second end of the left travel motor 29 to the first end, causing the left travel motor 29 to rotate in reverse. At this time, the tracked travel mechanism can move backward. The oil then flows back to the oil tank from the first end through the first main oil circuit 13 and the first control valve 21. The pressurized oil supplied by the main pump 11 passes through the second control valve 23 and then through the third main oil circuit 17. When it flows from the third end to the fourth end of the right travel motor 31, the right travel motor 31 rotates forward, allowing the tracked travel mechanism to move forward. The oil then flows back to the oil tank from the fourth end through the fourth main oil circuit 19 and the second control valve 23. Conversely, when the pressurized oil supplied by the main pump 11 passes through the second control valve 23 and then through the fourth main oil circuit 19, and flows from the fourth end to the third end of the right travel motor 31, the right travel motor 31 rotates forward, allowing the tracked travel mechanism to move backward. The oil then flows back to the oil tank from the third end through the third main oil circuit 17 and the second control valve 23. Alternatively, it can be designed so that the pressurized oil from the main pump 11 flows from the second end to the first end and from the fourth end to the third end for forward movement, while the pressurized oil from the main pump 11 flows from the first end to the second end and from the third end to the fourth end for backward movement.

[0044] In this embodiment, the tracked hydraulic system further includes a main pressure oil circuit 33 and a return oil circuit 35. One end of the main pressure oil circuit 33 is connected to the main pump 11, and the other end is connected to the first control valve 21 and the second control valve 23. One end of the return oil circuit 35 is connected to the oil tank 37, and the other end is connected to the first control valve 21 and the second control valve 23.

[0045] Specifically, both the first control valve 21 and the second control valve 23 are three-position four-way directional valves. The first control valve 21 includes a first port 212, a second port 213, a third port 214, and a fourth port 215. The first port 212 is connected to the main pump 11 via the main pressure oil circuit 33, the second port 213 is connected to the return oil circuit 35, the third port 214 is connected to the first main oil circuit 13, and the fourth port 215 is connected to the second main oil circuit 15. The first control valve 21 includes a first position, a second position, and a third position. The first position (i.e....) Figure 1 When the first oil port 212, the second oil port 213, the third oil port 214, and the fourth oil port 215 are disconnected from each other (i.e., in the middle position); Figure 1 When the first oil port 212 and the fourth oil port 215 are connected, and the second oil port 213 and the third oil port 214 are connected, the pressure oil provided by the main pump 11 flows into the second end of the left travel motor 29 through the main pressure oil circuit 33, the first oil port 212, the fourth oil port 215, and the second main oil circuit 15, and the left travel motor 29 reverses; the third position (i.e. Figure 1 When the first oil port 212 and the third oil port 214 are connected, the second oil port 213 and the fourth oil port 215 are connected, and the pressure oil provided by the main pump 11 flows into the first end of the left travel motor 29 through the main pressure oil circuit 33, the first oil port 212, the third oil port 214 and the first main oil circuit 13, and the left travel motor 29 rotates in the forward direction.

[0046] Specifically, the second control valve 23 includes a fifth port 232, a sixth port 233, a seventh port 234, and an eighth port 235. The fifth port 232 is connected to the main pump 11 via the main pressure oil circuit 33, the sixth port 233 is connected to the return oil circuit 35, the seventh port 234 is connected to the third main oil circuit 17, and the eighth port 235 is connected to the fourth main oil circuit 19. The second control valve 23 includes a fourth position, a fifth position, and a sixth position. The fourth position (i.e., Figure 1 When the fifth oil port 232, the sixth oil port 233, the seventh oil port 234, and the eighth oil port 235 are disconnected from each other (i.e., the middle position), the fifth position (i.e., the middle position) Figure 1 When the fifth oil port 232 and the eighth oil port 235 are connected, and the sixth oil port 233 and the seventh oil port 234 are connected, the pressure oil provided by the main pump 11 flows into the second end of the right travel motor 31 through the main pressure oil circuit 33, the fifth oil port 232, the eighth oil port 235, and the fourth main oil circuit 19, and the right travel motor 31 reverses; the sixth position (i.e. Figure 1 When the fifth oil port 232 and the seventh oil port 234 are connected, the sixth oil port 233 and the eighth oil port 235 are connected. The pressure oil provided by the main pump 11 flows into the first end of the right travel motor 31 through the main pressure oil circuit 33, the fifth oil port 232, the seventh oil port 234 and the third main oil circuit 17, and the right travel motor 31 rotates forward.

[0047] Specifically, the first control valve 21 and the second control valve 23 can be integrated into the same multi-way valve, or they can be separate independent valves.

[0048] Specifically, the control terminals of the first control valve 21 and the second control valve 23 can be connected to the control oil circuit (not shown in the figure). The control oil circuit is used to supply pilot oil to the first control valve 21 and the second control valve 23 according to the operation of the operating handle of the tracked construction machinery, so as to control the switching of the first control valve 21 and the second control valve 23.

[0049] In this embodiment, the first proportional directional valve 25 is used to directly connect the first end of the left travel motor 29 and the third oil port 214 of the first control valve 21, or to connect the first end of the left travel motor 29 and the third oil port 214 of the first control valve 21 through a throttle valve. The second proportional directional valve 27 is used to directly connect the third end of the right travel motor 31 and the seventh oil port 234 of the second control valve 23, or to connect the third end of the right travel motor 31 and the seventh oil port 234 of the second control valve 23 through a throttle valve.

[0050] Specifically, both the first proportional directional valve 25 and the second proportional directional valve 27 can be two-position three-way valves. The first proportional directional valve 25 includes a first reversing port 252, a second reversing port 253, and a third reversing port 254. The first reversing port 252 is connected to the third port 214 of the first control valve 21, and the third reversing port 254 is connected to the first end of the left travel motor 29. The first proportional directional valve 25 includes a first reversing position (i.e., Figure 1 The right position in the middle) and the second reversal position (i.e. Figure 1 In the first reversing position (left position), the first reversing port 252 and the third reversing port 254 are directly connected, and the second reversing port 253 is disconnected from both the first reversing port 252 and the third reversing port 254; in the second reversing position, the first reversing port 252 and the third reversing port 254 are connected through a throttle valve, and the first reversing port 252 and the second reversing port 253 are connected. The second proportional reversing valve 27 includes a fourth reversing port 272, a fifth reversing port 273 and a sixth reversing port 274. The fourth reversing port 272 is connected to the seventh port 234 of the second control valve 23, and the sixth reversing port 274 is connected to the third end of the right travel motor 31. The second proportional reversing valve 27 includes a third reversing position (i.e., the left position). Figure 1 The right position in the middle) and the fourth reversal position (i.e. Figure 1 In the left position), when in the third reversing position, the fourth reversing port 272 and the sixth reversing port 274 are directly connected, and the fifth reversing port 273 is disconnected from both the fourth reversing port 272 and the sixth reversing port 274; when in the fourth reversing position, the fourth reversing port 272 and the sixth reversing port 274 are connected through a throttle valve, and the fourth reversing port 272 and the fifth reversing port 273 are connected.

[0051] Specifically, both the first proportional directional valve 25 and the second proportional directional valve 27 can be solenoid valves. When the solenoids of the first proportional directional valve 25 and the second proportional directional valve 27 are not energized, the first proportional directional valve 25 and the second proportional directional valve 27 are in the right position. When the solenoids of the first proportional directional valve 25 and the second proportional directional valve 27 are energized, the first proportional directional valve 25 and the second proportional directional valve 27 are in the left position.

[0052] Specifically, the valve core displacement response of the first proportional directional valve 25 and the second proportional directional valve 27 is a ramp response, so as to ensure smooth operation during correction. That is to say, when the flow rate is adjusted by the first proportional directional valve 25 and the second proportional directional valve 27, the flow rate changes gradually.

[0053] Specifically, the first main oil circuit 13 and the third main oil circuit 17 are directly connected through the connecting oil circuit 38. In this way, when the first proportional directional valve 25 is energized and in the left position, part of the flow in the first main oil circuit 13 flows to the third main oil circuit 17. Similarly, when the second proportional directional valve 27 is energized and in the left position, part of the flow in the third main oil circuit 17 flows to the first main oil circuit 13.

[0054] In this embodiment, the tracked hydraulic system further includes a relief valve 39, one end of which is connected to the main pressure oil circuit 33, and the other end is connected to the return oil circuit 35. The relief valve 39 is used to overflow when the pressure of the pressure oil provided by the main pump 11 is greater than the set pressure of the relief valve 39.

[0055] It is understood that the travel motor in the tracked hydraulic system of this embodiment can be replaced with other actuators such as hydraulic cylinders to form hydraulic circuits for other engineering machinery, such as the synchronous control hydraulic circuit for the upper and lower lateral movement cylinders of a TRD chain grooving machine. In the specific connection of the hydraulic circuit, the first and second ends of the left travel motor 29 in this embodiment are basically replaced with the rodless and rod-type chambers of the upper lateral movement cylinder, respectively, and the third and fourth ends of the right travel motor 31 are replaced with the rodless and rod-type chambers of the lower lateral movement cylinder, respectively. The connecting oil line 38 can be omitted. The remaining structures are basically the same and will not be described in detail here.

[0056] In the hydraulic circuit of the engineering machinery in this embodiment, when the first proportional directional valve 25 is energized and in the left position, the flow rate into the left travel motor 29 decreases, the rotation speed of the left travel motor 29 decreases, the left side of the tracked travel mechanism travels slower, and the right side travels faster. The tracked travel mechanism will deflect to the left by a certain angle. When the tracked travel mechanism deflects too much to the right, the deflection can be corrected by reducing the speed of the left travel motor 29, thus achieving leftward correction. Correspondingly, when the second proportional directional valve 27 is energized and in the left position, the flow rate into the right travel motor 31 decreases, which can cause the tracked travel mechanism to deflect to the right by a certain angle, achieving rightward correction.

[0057] This application also provides a track correction device for controlling the hydraulic circuit of the aforementioned construction machinery. This track correction device can be applied to tracked construction machinery. Figure 2 As shown, the tracked construction machinery includes a main unit 41, a first guide wheel 42, a second guide wheel 43, a first drive wheel 44, and a second drive wheel 45. The first guide wheel 42 and the second guide wheel 43 are respectively installed at the front ends of both sides of the main unit 41, and the first drive wheel 44 and the second drive wheel 45 are respectively installed at the rear ends of both sides of the main unit 41. The left travel motor 29 and the right travel motor 31 are used to drive the first drive wheel 44 and the second drive wheel 45 to rotate, thereby enabling the tracked walking mechanism of the tracked construction machinery to move.

[0058] In this embodiment, the track correction device includes a position detection element 51, a tilt angle detection element 53, and a control module 55. Please refer to [the relevant documentation / reference]. Figure 3 The position detection element 51 is used to detect the initial position (x) of the construction machinery. t0 ,y t0 ) and current position (x) t '1,y t '1) The tilt angle detection element 53 is used to detect the initial azimuth angle of the engineering machinery. Control module 55 is used to determine the initial position (x) t0 ,y t0 ), current position (x) t '1,y t '1) and initial azimuth angle The system calculates the shortest distance deviation L between the current position and the theoretical trajectory, and determines whether the absolute value of the shortest distance deviation L is less than or equal to the deviation threshold a. If the absolute value of the shortest distance deviation L is greater than the deviation threshold a, the system controls the first proportional directional valve 25 to adjust the flow rate of the first main oil circuit 13 into the left travel motor 29, or controls the second proportional directional valve 27 to adjust the flow rate of the third main oil circuit 17 into the right travel motor 31. Specifically, the position detection element 51 can be a GPS detection device, and the tilt detection element 53 can be an inclinometer.

[0059] In the track correction device of this embodiment, when the tracked walking mechanism deviates from its course, the flow rate in the first main oil circuit and the third main oil circuit can be controlled by controlling the position of the proportional reversing valve, thereby adjusting the movement of the left and right walking motors and achieving automatic correction without manual operation, thus reducing the labor intensity of the operator.

[0060] In this embodiment, the control module 55 determines the initial position (x) based on the initial position (x). t0 ,y t0 ), current position (x) t '1,y t '1) and initial azimuth angle When calculating the shortest distance deviation L between the current position and the theoretical trajectory, it is specifically used for: according to the formula Calculate the current azimuth angle of the current position. And according to the formula Calculate the shortest distance deviation L, where, Among them, the initial azimuth angle The angle between the reference trajectory and the x-axis; the current azimuth of the current position. The angle between the line connecting the current position and the initial position and the x-axis. In this embodiment, the current trajectory deviation value is obtained in real time through an algorithm based on the data provided by the position detection element 51 and the tilt detection element 53, and the trajectory is corrected, which can improve the accuracy of the correction. The shortest distance deviation L is the distance perpendicular to the theoretical trajectory and passing through the current position (x...). t '1,y t The theoretical trajectory on the straight line of '1) and the current position (x) t '1,y t The line segment between '1).

[0061] In this embodiment, the control module 55 determines whether the absolute value of the shortest distance deviation L is less than or equal to the deviation threshold a, and controls the first proportional directional valve 25 to adjust the flow rate of the first main oil circuit 13 into the left travel motor 29 or controls the second proportional directional valve 27 to adjust the flow rate of the third main oil circuit 17 into the right travel motor 31 when the absolute value of the shortest distance deviation L is greater than or equal to the deviation threshold a and greater than or equal to the negative value of the deviation threshold - a. If not, it determines whether the shortest distance deviation L is greater than the deviation threshold a. When the shortest distance deviation L is greater than the deviation threshold a, it controls the first proportional directional valve 25 to be in the state of connecting the first end of the left travel motor 29 and the third oil port 214 of the first control valve 21 through the throttle valve. Otherwise, it controls the second proportional directional valve 27 to be in the state of connecting the third end of the right travel motor 31 and the seventh oil port 234 of the second control valve 23 through the throttle valve. Specifically, when L>a, it indicates that the tracked walking mechanism has deviated to the right by a certain amount, and the first proportional directional valve 25 can be controlled to correct the deviation to the left; when L<-a, it indicates that the tracked walking mechanism has deviated to the left by a certain amount, and the second proportional directional valve 27 can be controlled to correct the deviation to the right.

[0062] In this embodiment, the track correction device also includes a joystick detection element 57, which is used to detect the movement of the joystick. The control module 55 is also used to determine whether the tracked walking mechanism is moving in a straight line based on the movement of the joystick, and to perform correction control when the tracked walking mechanism is moving in a straight line.

[0063] Specifically, the control module 55 is used to determine whether the tracked walking mechanism is moving in a straight line based on the movement of the joysticks. Specifically, at the initial start of the tracked walking mechanism, the control module 55 checks whether both left and right joysticks have moved forward and whether the difference in their reversal times satisfies |T1-T2|≤△T. When |T1-T2|≤△T is satisfied and both left and right joysticks have moved forward, correction control is performed. Here, T1 and T2 refer to the reversal times of the left and right joysticks, respectively, and △T is a preset time difference threshold. Reversing the joysticks means pushing them to their extreme positions in a certain direction. The control module 55 is also used to determine whether the displacement of the left and right joysticks satisfies |x1-x2|≤b during the straight-line movement of the tracked walking mechanism. If the displacement of the left and right joysticks satisfies |x1-x2|≤b, the tracked walking mechanism is judged to be moving in a straight line; otherwise, it is judged not to be moving in a straight line. Here, x1 and x2 refer to the displacement of the left and right joysticks, respectively, and b is a preset displacement threshold.

[0064] This application also provides a track correction method for controlling tracked construction machinery equipped with the aforementioned hydraulic circuit. Please refer to [reference needed]. Figure 4The track correction method in this embodiment includes the following steps:

[0065] S11, start the tracked walking mechanism, operate the control lever to make the tracked walking mechanism start moving. At this time, the first proportional reversing valve 25 and the second proportional reversing valve 27 are both in the initial state, that is, the first proportional reversing valve 25 is directly connected to the first end of the left walking motor 29 and the third oil port 214 of the first control valve 21, and the second proportional reversing valve 27 is directly connected to the third end of the right walking motor 31 and the seventh oil port 234 of the second control valve 23.

[0066] S13: Detect the movement of the control lever and determine whether the tracked walking mechanism is moving in a straight line based on the movement of the control lever. When the tracked walking mechanism is moving in a straight line, proceed to step S15; when the tracked walking mechanism is not moving in a straight line, proceed to step S17.

[0067] S15, obtain the shortest distance deviation L between the current position of the construction machinery and the theoretical trajectory.

[0068] S16, determine whether the absolute value of the shortest distance deviation L is less than or equal to the deviation threshold a. If yes, continue walking in a straight line; otherwise, proceed to step S18.

[0069] S17, the first proportional directional valve 25 and the second proportional directional valve 27 remain in their initial state and do not perform correction control on the tracked walking mechanism.

[0070] S18, control the first proportional directional valve 25 to switch states to adjust the flow rate of the first main oil circuit 13 into the left travel motor 29, or control the second proportional directional valve 27 to switch states to adjust the flow rate of the third main oil circuit 17 into the right travel motor 31.

[0071] S19. During the movement of the tracked walking mechanism, determine whether the tracked walking mechanism is moving in a straight line. If the tracked walking mechanism is moving in a straight line, proceed to step S15. If the tracked walking mechanism is not moving in a straight line, proceed to step S17.

[0072] In the track correction method of this embodiment, when the tracked walking mechanism deviates from its course, the flow rate in the first main oil circuit and the third main oil circuit can be controlled by controlling the position of the proportional reversing valve, thereby adjusting the movement of the left and right walking motors and achieving automatic correction without manual operation, thus reducing the labor intensity of the operator.

[0073] In this embodiment, please refer to Figure 5 Step S13 specifically includes:

[0074] S131, obtain the movement of the left and right joysticks.

[0075] S133, based on the actions of the left and right joysticks, determine whether both joysticks have moved forward and whether the difference between the reversing times of the left and right joysticks satisfies |T1-T2|≤△T, where T1 and T2 refer to the reversing times of the left and right joysticks, respectively. △T is a preset time difference threshold.

[0076] S135: The tracked walking mechanism is considered to be traveling in a straight line when |T1-T2|≤△T and both left and right control levers move forward; otherwise, the tracked walking mechanism is not traveling in a straight line. Control lever reversal refers to pushing the control lever to its extreme position in a certain direction.

[0077] In this embodiment, please refer to Figure 6 Step S15 specifically includes:

[0078] S151, Detecting the initial position (x) of the construction machinery. t0 ,y t0 and initial azimuth angle

[0079] S153, Obtain the current position (x) of the construction machinery. t '1,y t '1), and based on the current position (x) t '1,y t '1) and initial position (x t0 ,y t0 Obtain the current azimuth angle of the construction machinery. Specifically, according to the formula Calculate the current azimuth angle of the current position.

[0080] S155, based on the initial azimuth angle When the front azimuth angle initial position (x) t0 ,y t0 ) and current position (x) t '1,y t '1) Obtain the shortest distance deviation L between the current position and the theoretical trajectory. Wherein, the shortest distance deviation L is the distance perpendicular to the theoretical trajectory and passing through the current position (x... t '1,y t The theoretical trajectory on the straight line of '1) and the current position (x) t '1,y t The line segment between '1) and '2). Specifically, according to the formula Calculate the shortest distance deviation L, where, Among them, the initial azimuth angle The angle between the reference trajectory and the x-axis; the current azimuth of the current position. Let x be the angle between the line connecting the current position and the initial position and the x-axis. It can be understood that when returning from step S19 to step S15, the initial position (x...) t0 ,y t0 and initial azimuth angle No further detection is needed; that is, returning to step S15 only requires repeating steps S153 and S155. Furthermore, the shortest distance deviation L is not limited to the method used in steps S151 to S155; it can also be obtained through other methods. For example, obtaining the initial position and initial azimuth angle to obtain the theoretical trajectory, recording the time t1 from the initial position to the current position, obtaining the theoretical current position that should be reached after time t1 from the initial position based on the current speed and the theoretical trajectory, and calculating the shortest distance deviation L based on the theoretical current position and the current position.

[0081] In this embodiment, please refer to Figure 7 Step S16 specifically includes:

[0082] S161, determine whether the shortest distance deviation L is less than or equal to the deviation threshold a and greater than or equal to the negative value of the deviation threshold -a. If yes, continue walking in a straight line; otherwise, proceed to step S163.

[0083] S163, determine whether the shortest distance deviation L is greater than the deviation threshold a. If yes, proceed to step S165; if no (i.e., if L < -a), proceed to step S167.

[0084] S165, the first proportional directional valve 25 is controlled to be in a state where the first end of the left travel motor 29 and the third oil port 214 of the first control valve 21 are connected through the throttle valve. Specifically, when L>a, it means that the tracked travel mechanism deflects to the right, and the speed of the left travel motor 29 is greater than the speed of the right travel motor 31. At this time, the electromagnet controlling the first proportional directional valve 25 is energized, so that the first proportional directional valve 25 is in the left position. The pressure oil provided by the main pump 11 passes through the throttle valve of the first proportional directional valve 25, reducing the flow rate into the left travel motor 29. This allows the tracked travel mechanism to deflect to the left until L is less than or equal to a.

[0085] S167, the second proportional directional valve 27 is controlled to be in a state where it is connected to the third end of the right travel motor 31 and the seventh oil port 234 of the second control valve 23 through the throttle valve. Specifically, when L < -a, it means that the tracked travel mechanism deflects to the left and the speed of the right travel motor 31 is greater than the speed of the left travel motor 29. At this time, the electromagnet controlling the second proportional directional valve 27 is energized, so that the second proportional directional valve 27 is in the left position. The pressure oil provided by the main pump 11 passes through the throttle valve of the second proportional directional valve 27, reducing the flow rate into the right travel motor 31. This allows the tracked travel mechanism to deflect to the left until L is greater than or equal to -a.

[0086] In this embodiment, step S19 specifically includes: determining whether the displacement of the left and right control levers satisfies |x1-x2|≤b during the movement of the tracked walking mechanism; if the displacement of the left and right control levers satisfies |x1-x2|≤b, it is determined that the tracked walking mechanism is moving in a straight line; otherwise, it is determined that the tracked walking mechanism is not moving in a straight line. Here, x1 and x2 refer to the displacement of the left and right control levers, respectively, and b is a preset displacement threshold.

[0087] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the appended claims.

Claims

1. A track correction device, characterized in that, This hydraulic circuit is used to control the hydraulic circuit of construction machinery. The hydraulic circuit includes a main pump (11), a first main oil circuit (13), a second main oil circuit (15), a third main oil circuit (17), a fourth main oil circuit (19), a first control valve (21), a second control valve (23), a first proportional directional valve (25), a second proportional directional valve (27), a first actuator, and a second actuator. The main pump (11) supplies oil to the first actuator through the first main oil circuit (13) or the second main oil circuit (15). The main pump (11) also supplies oil through the third main oil circuit (17) or the fourth main oil circuit (19). The first control valve (21) and the second control valve (23) are connected to the main pump (11). The first main oil circuit (13) and the second main oil circuit (15) control whether the main pump (11) supplies oil to the first actuator through the first main oil circuit (13) or the second main oil circuit (15). The second control valve (23) is connected to the third main oil circuit (17) and the fourth main oil circuit (19) to control whether the main pump (11) supplies oil to the second actuator through the third main oil circuit (17) or the fourth main oil circuit (19). The first proportional directional valve (25) is provided on the first main oil circuit (13) to adjust the flow rate of the first main oil circuit (13) into the first actuator. The second proportional directional valve (27) is provided on the third main oil circuit (17) to adjust the flow rate of the third main oil circuit (17) into the second actuator. The first actuator is a left travel motor (29), the second actuator is a right travel motor (31), the main pump (11) is used to supply oil to the left travel motor (29) through the first main oil circuit (13) or the second main oil circuit (15) to make the left travel motor (29) rotate forward or reverse respectively, the main pump (11) is also used to supply oil through the third main oil circuit (17) or the fourth main oil circuit (19) to make the right travel motor (31) rotate forward or reverse respectively; The valve core displacement response of the first proportional directional valve (25) and the second proportional directional valve (27) is a ramp response; or, the first main oil circuit (13) and the third main oil circuit (17) are directly connected through a connecting oil circuit (38); The track correction device includes a position detection element (51), a tilt angle detection element (53), and a control module (55). The position detection element (51) is used to detect the initial position of the construction machinery. x t0 , y t0 ) and current location ( x 't1, y 't1), the tilt angle detection element (53) is used to detect the initial azimuth angle of the engineering machinery. φ The control module (55) is used to determine the initial position ( x t0 , y t0 The current position ( x 't1, y 't1) and the initial azimuth angle φ Calculate the shortest distance deviation between the current position and the theoretical trajectory. L And determine the shortest distance deviation. L Is the absolute value less than or equal to the deviation threshold? a ), and in the shortest distance deviation L The absolute value is greater than the deviation threshold ( a When the first proportional directional valve (25) is controlled to adjust the flow rate of the first main oil circuit (13) into the left travel motor (29), or the second proportional directional valve (27) is controlled to adjust the flow rate of the third main oil circuit (17) into the right travel motor (31).

2. The track correction device as described in claim 1, characterized in that, The control module (55) is based on the initial position ( x t0 , y t0 The current position ( x 't1, y 't1) and the initial azimuth angle φ Calculate the shortest distance deviation between the current position and the theoretical trajectory. L Specifically used for: according to the formula φ ’ =arctan[( y 't1- y t0 ) / ( x 't1- x t0 )] Calculate the current azimuth angle of the current position. φ ’ And according to the formula L =sqrt[( x 't1 - x t0 ) 2 +( y 't1- y t0 ) 2 ]×sin(△ φ Calculate the shortest distance deviation. L , where △ φ = φ - φ ’ ; The control module (55) determines the shortest distance deviation. L Is the absolute value less than or equal to the deviation threshold? a ), and in the shortest distance deviation L The absolute value is greater than the deviation threshold ( a When controlling the first proportional directional valve (25) to adjust the flow rate of the first main oil circuit (13) into the left travel motor (29) or controlling the second proportional directional valve (27) to adjust the flow rate of the third main oil circuit (17) into the right travel motor (31), it is specifically used to: determine the shortest distance deviation. L Is it less than or equal to the deviation threshold? a If the deviation is greater than or equal to the negative value (-a) of the deviation threshold, then the shortest distance deviation is determined. L Whether the deviation is greater than the deviation threshold (a), when the shortest distance deviation L Greater than the deviation threshold ( a When the first proportional directional valve (25) is controlled to be in a state where the first end of the left travel motor (29) and the first control valve (21) are connected through the throttle valve, the shortest distance deviation is... L Less than the negative value of the deviation threshold ( -a When the second proportional directional valve (27) is in a state where the third end of the right travel motor (31) and the second control valve (23) are connected through the throttle valve; The track correction device also includes a joystick detection element (57), which is used to detect the movement of the joystick. The control module (55) is also used to determine whether the tracked walking mechanism is moving in a straight line based on the movement of the joystick, and to perform correction control when the tracked walking mechanism is moving in a straight line.

3. The track correction device as described in claim 1, characterized in that, The first proportional directional valve (25) is used to directly connect the first end of the left travel motor (29) and the first control valve (21), or to connect the first end of the left travel motor (29) and the first control valve (21) through a throttle valve; the second proportional directional valve (27) is used to directly connect the third end of the right travel motor (31) and the second control valve (23), or to connect the third end of the right travel motor (31) and the second control valve (23) through a throttle valve.

4. The track correction device as described in claim 3, characterized in that, The first proportional directional valve (25) includes a first directional port (252), a second directional port (253), and a third directional port (254). The first directional port (252) is connected to the first control valve (21), and the third directional port (254) is connected to the first end of the left travel motor (29). The first proportional directional valve (25) includes a first directional position and a second directional position. In the first directional position, the first directional port (252) and the third directional port (254) are directly connected, and the second directional port (253) is disconnected from both the first directional port (252) and the third directional port (254). In the second directional position, the first directional port (252) and the third directional port (254) are connected through a throttle valve, and the first directional port (252) and the second directional port (253) are connected. The second proportional directional valve (27) includes a fourth directional port (272), a fifth directional port (273), and a sixth directional port (274). The fourth directional port (272) is connected to the second control valve (23), and the sixth directional port (274) is connected to the third end of the right travel motor (31). The second proportional directional valve (27) includes a third directional position and a fourth directional position. In the third directional position, the fourth directional port (272) and the sixth directional port (274) are directly connected, and the fifth directional port (273) is disconnected from both the fourth directional port (272) and the sixth directional port (274). In the fourth directional position, the fourth directional port (272) and the sixth directional port (274) are connected through a throttle valve, and the fourth directional port (272) and the fifth directional port (273) are connected.

5. A track correction method for controlling a track correction device as described in any one of claims 1 to 4, characterized in that, The track correction method includes: Start the tracked walking mechanism and operate the control lever to make the tracked walking mechanism start walking. At this time, the first proportional reversing valve (25) and the second proportional reversing valve (27) are both in the initial state. The movement of the control joystick is detected, and the movement of the joystick is used to determine whether the tracked walking mechanism is moving in a straight line. If it is, the shortest distance deviation between the current position and the theoretical trajectory is obtained. L If not, the first proportional directional valve (25) and the second proportional directional valve (27) remain in their initial states; Obtain the shortest distance deviation L Then, determine the shortest distance deviation. L Is the absolute value less than or equal to the deviation threshold? a If the vehicle continues to travel in a straight line, then if not, control the first proportional directional valve (25) to switch states to adjust the flow rate of the first main oil circuit (13) into the left travel motor (29) or control the second proportional directional valve (27) to switch states to adjust the flow rate of the third main oil circuit (17) into the right travel motor (31).

6. The track correction method as described in claim 5, characterized in that, The steps of detecting the movement of the control joystick and determining whether the tracked walking mechanism is moving in a straight line based on the movement of the control joystick specifically include: Acquire the actions of the left and right joysticks; Based on the movements of the left and right joysticks, determine whether both joysticks move forward and whether the time difference between the left and right joysticks reaching their final positions satisfies | T 1- T 2|≤△ T , △ T The preset time difference threshold; In satisfying | T 1- T 2|≤△ T When both left and right control levers move forward, the tracked walking mechanism is determined to be traveling in a straight line; otherwise, the tracked walking mechanism is not traveling in a straight line.

7. The track correction method as described in claim 5, characterized in that, Obtain the shortest distance deviation between the current position of the construction machinery and its theoretical trajectory. L The specific steps include: Detecting the initial position of construction machinery ( x t0 , y t0 ) and current location ( x 't1, y 't1), to detect the initial azimuth angle of the construction machinery. φ According to the formula φ ’ =arctan[( y 't1- y t0 ) / ( x 't1- x t0 )] Calculate the current azimuth angle of the current position. φ ’ And according to the formula L =sqrt[( x 't1- x t0 ) 2 +( y 't1- y t0 ) 2 ]×sin(△ φ Calculate the shortest distance deviation. L , where △ φ = φ - φ ’ .

8. The track correction method as described in claim 5, characterized in that, Determine whether the absolute value of the shortest distance deviation L is less than or equal to the deviation threshold. a Specifically, it includes: Determine whether the shortest distance deviation L is less than or equal to the deviation threshold. a And greater than or equal to the negative value of the deviation threshold ( -a If yes, continue walking in a straight line; otherwise, determine the deviation of the shortest distance. L Is it greater than the deviation threshold? a ); if the shortest distance deviation L Greater than the deviation threshold ( a ), control the first proportional directional valve (25) to be in a state where the first end of the left travel motor (29) and the first control valve (21) are connected through the throttle valve, if the shortest distance deviation L Negative values ​​less than the deviation threshold ( -a The second proportional directional valve (27) is controlled to be in a state where the third end of the right travel motor (31) and the second control valve (23) are connected through the throttle valve.

9. The track correction method as described in claim 5, characterized in that, The track correction method further includes the following steps: during the movement of the tracked walking mechanism, determining whether the tracked walking mechanism is moving in a straight line; if the tracked walking mechanism is moving in a straight line, obtaining the shortest distance deviation between the current position of the construction machinery and the theoretical trajectory. L If the tracked walking mechanism is not traveling in a straight line, it enters the step of maintaining the initial state of the first proportional directional valve (25) and the second proportional directional valve (27); During the movement of the tracked walking mechanism, determining whether the tracked walking mechanism is moving in a straight line specifically includes: determining whether the displacement of the left and right control levers meets the requirements of | x 1- x 2|≤ b When the displacement of the left and right joysticks satisfies | x 1- x 2|≤ b If the tracked walking mechanism is moving in a straight line, it is determined that the tracked walking mechanism is moving in a straight line; otherwise, it is determined that the tracked walking mechanism is not moving in a straight line. x 1. x 2 refers to the displacement of the left and right joysticks, respectively. b This is a preset displacement threshold.

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