JP7474626B2 - Excavator - Google Patents

Description

The present invention relates to a shovel.

There is known an excavator that supplies hydraulic oil discharged from a hydraulic pump to a hydraulic actuator in response to the operation of an operating lever by an operator, thereby operating the hydraulic actuator. In addition, the excavator is provided with a bleed valve that controls the flow rate of hydraulic oil discharged from the hydraulic pump that flows to the hydraulic oil tank without passing through the hydraulic actuator.

For example, Patent Document 1 discloses a hydraulic circuit for a hydraulic excavator that has spool opening characteristics in which the opening area of the bleed valve corresponds one-to-one to the amount of operation (stroke) of the operating lever.

JP 2010-47983 A

When driving the hydraulic actuator, hydraulic oil is supplied from the hydraulic pump to the hydraulic actuator through a small opening of the bleed valve. For this reason, controllability of the small opening of the bleed valve is required to improve the operability of the excavator. In addition, when the hydraulic actuator decelerates or stops, it is necessary to guide the hydraulic oil discharged from the hydraulic pump to the hydraulic oil tank, and therefore it is required to increase the maximum opening of the bleed valve.

Therefore, in consideration of the above issues, the objective is to provide a shovel that is easy to operate.

A shovel according to an embodiment of the present invention includes a hydraulic pump, a hydraulic actuator driven by hydraulic oil discharged by the hydraulic pump, an oil passage capable of supplying the hydraulic oil discharged by the hydraulic pump to the hydraulic actuator, a control valve provided in the oil passage and controlling the flow rate of the hydraulic oil supplied to the hydraulic actuator, a first bleed valve provided in the oil passage and controlling the flow rate of the hydraulic oil flowing to a hydraulic oil tank without passing through the hydraulic actuator, and a second bleed valve provided in the oil passage and arranged in parallel to the first bleed valve , wherein the first bleed valve has a function of specializing in minute opening changes, and the second bleed valve has a function of specializing in large opening changes .

According to an embodiment of the present invention, a shovel with good operability can be provided.

FIG. 1 is a side view of a shovel according to an embodiment of the present invention; FIG. 2 is a block diagram showing an example of the configuration of a drive system of the excavator shown in FIG. FIG. 2 is a schematic diagram showing an example of the configuration of a hydraulic circuit mounted on the excavator of FIG. Graph showing bleed valve opening area in a reference example Graph explaining the bleed valve opening area in this embodiment Flowchart showing the control of the bleed valve Graph showing the change in lever operation amount and pressure over time FIG. 2 is a schematic diagram showing another example of the configuration of a hydraulic circuit mounted on the excavator of FIG. Graph showing bleed valve opening area in another configuration example FIG. 1 is a diagram showing a configuration example of an operation system including an electric operation device.

Below, a description of the embodiment of the invention will be given with reference to the drawings. In each drawing, the same components are given the same reference numerals, and duplicated explanations may be omitted.

First, the overall configuration of a shovel according to an embodiment of the present invention will be described with reference to FIG. 1. FIG. 1 is a side view of a shovel (excavator) according to an embodiment of the present invention.

As shown in FIG. 1, an upper rotating body 3 is rotatably mounted on a lower running body 1 of the excavator via a rotating mechanism 2. A boom 4 is attached to the upper rotating body 3. An arm 5 is attached to the tip of the boom 4, and a bucket 6 is attached to the tip of the arm 5 as an end attachment. The boom 4, arm 5, and bucket 6 constitute an excavation attachment as an example of an attachment, and are hydraulically driven by a boom cylinder 7, arm cylinder 8, and bucket cylinder 9, respectively. A cabin 10, which is a driver's room, is provided on the upper rotating body 3, and a power source such as an engine 11 is mounted on it.

A controller 30 is installed inside the cabin 10. The controller 30 functions as a main control unit that controls the drive of the shovel. In this embodiment, the controller 30 is configured as a computer including a CPU, RAM, ROM, etc. The various functions of the controller 30 are realized, for example, by the CPU executing a program stored in the ROM.

Next, the configuration of the drive system of the shovel in FIG. 1 will be described with reference to FIG. 2. FIG. 2 is a block diagram showing an example of the configuration of the drive system of the shovel in FIG. 1. In FIG. 2, the mechanical power system, high-pressure hydraulic line, pilot line, and electrical control system are indicated by double lines, thick solid lines, dashed lines, and dashed dotted lines, respectively.

As shown in FIG. 2, the drive system of the excavator mainly includes an engine 11, a regulator 13, a main pump 14, a pilot pump 15, a control valve 17, an operating device 26, a discharge pressure sensor 28, an operating pressure sensor 29, a controller 30, a proportional valve 31, etc.

The engine 11 is the driving source of the excavator. In this embodiment, the engine 11 is, for example, a diesel engine that operates to maintain a predetermined rotation speed. In addition, the output shaft of the engine 11 is connected to the input shafts of the main pump 14 and the pilot pump 15.

The main pump 14 supplies hydraulic oil to the control valve 17 via a high-pressure hydraulic line. In this embodiment, the main pump 14 is a swash plate type variable displacement hydraulic pump.

The regulator 13 controls the discharge volume of the main pump 14. In this embodiment, the regulator 13 controls the discharge volume of the main pump 14 by adjusting the swash plate tilt angle of the main pump 14 in response to a control command from the controller 30.

The pilot pump 15 supplies hydraulic oil to various hydraulic control devices, including the operating device 26 and the proportional valve 31, via a pilot line. In this embodiment, the pilot pump 15 is a fixed displacement hydraulic pump.

The control valve 17 is a hydraulic control device that controls the hydraulic system in the excavator. The control valve 17 includes control valves 171 to 176 and a bleed valve 177. The control valve 17 can selectively supply hydraulic oil discharged by the main pump 14 to one or more hydraulic actuators through the control valves 171 to 176. The control valves 171 to 176 control the flow rate of hydraulic oil flowing from the main pump 14 to the hydraulic actuators and the flow rate of hydraulic oil flowing from the hydraulic actuators to the hydraulic oil tank. The hydraulic actuators include the boom cylinder 7, the arm cylinder 8, the bucket cylinder 9, the left-side traveling hydraulic motor 1A, the right-side traveling hydraulic motor 1B, and the swing hydraulic motor 2A. The bleed valve 177 controls the flow rate of hydraulic oil (hereinafter referred to as the "bleed flow rate") that flows to the hydraulic oil tank without passing through the hydraulic actuators out of the hydraulic oil discharged by the main pump 14. The bleed valve 177 may be installed outside the control valve 17.

The operating device 26 is a device used by an operator to operate the hydraulic actuators. In this embodiment, the operating device 26 supplies hydraulic oil discharged by the pilot pump 15 to the pilot ports of the control valves corresponding to each hydraulic actuator via a pilot line. The pressure of the hydraulic oil supplied to each pilot port (pilot pressure) is a pressure that corresponds to the operation direction and amount of operation of the lever or pedal (not shown) of the operating device 26 corresponding to each hydraulic actuator.

The discharge pressure sensor 28 detects the discharge pressure of the main pump 14. In this embodiment, the discharge pressure sensor 28 outputs the detected value to the controller 30.

The operating pressure sensor 29 detects the operation content of the operator using the operating device 26. In this embodiment, the operating pressure sensor 29 detects the operation direction and operation amount of the lever or pedal of the operating device 26 corresponding to each hydraulic actuator in the form of pressure (operating pressure), and outputs the detected value to the controller 30. The operation content of the operating device 26 may be detected using a sensor other than the operating pressure sensor.

The proportional valve 31 operates in response to a control command output by the controller 30. In this embodiment, the proportional valve 31 is a solenoid valve that adjusts the secondary pressure introduced from the pilot pump 15 to the pilot port of the bleed valve 177 in the control valve 17 in response to a current command output by the controller 30. The proportional valve 31 operates such that, for example, the larger the current command, the greater the secondary pressure introduced to the pilot port of the bleed valve 177.

Next, referring to FIG. 3, an example of the configuration of a hydraulic circuit mounted on a shovel will be described. FIG. 3 is a schematic diagram showing an example of the configuration of a hydraulic circuit mounted on the shovel of FIG. 1. In FIG. 3, similar to FIG. 2, the mechanical power system, high-pressure hydraulic line, pilot line, and electrical control system are shown by double lines, thick solid lines, dashed lines, and dashed dotted lines, respectively.

The hydraulic circuit in FIG. 3 circulates hydraulic oil from main pumps 14L, 14R driven by engine 11 through lines 42L, 42R to a hydraulic oil tank. Main pumps 14L, 14R correspond to main pump 14 in FIG. 2.

Pipe 42L is a high-pressure hydraulic line that connects each of control valves 171, 173, 175L, and 176L arranged in control valve 17 in parallel between main pump 14L and the hydraulic oil tank. Pipe 42R is a high-pressure hydraulic line that connects each of control valves 172, 174, 175R, and 176R arranged in control valve 17 in parallel between main pump 14R and the hydraulic oil tank.

The control valve 171 is a spool valve that switches the flow of hydraulic oil to supply the hydraulic oil discharged by the main pump 14L to the left-side traveling hydraulic motor 1A and to discharge the hydraulic oil discharged by the left-side traveling hydraulic motor 1A to the hydraulic oil tank.

The control valve 172 is a spool valve that switches the flow of hydraulic oil to supply the hydraulic oil discharged by the main pump 14R to the right-side traveling hydraulic motor 1B and to discharge the hydraulic oil discharged by the right-side traveling hydraulic motor 1B to the hydraulic oil tank.

The control valve 173 is a spool valve that switches the flow of hydraulic oil to supply the hydraulic oil discharged by the main pump 14L to the rotation hydraulic motor 2A and to discharge the hydraulic oil discharged by the rotation hydraulic motor 2A to the hydraulic oil tank.

The control valve 174 is a spool valve that supplies hydraulic oil discharged by the main pump 14R to the bucket cylinder 9 and discharges the hydraulic oil in the bucket cylinder 9 to the hydraulic oil tank.

The control valves 175L and 175R are spool valves that supply hydraulic oil discharged from the main pumps 14L and 14R to the boom cylinder 7 and switch the flow of hydraulic oil to discharge the hydraulic oil in the boom cylinder 7 to the hydraulic oil tank.

The control valves 176L and 176R are spool valves that supply hydraulic oil discharged from the main pumps 14L and 14R to the arm cylinder 8 and switch the flow of hydraulic oil to discharge the hydraulic oil in the arm cylinder 8 to the hydraulic oil tank.

Bleed valves 177L1 and 177L2 are spool valves that control the bleed flow rate of the hydraulic oil discharged by main pump 14L. Bleed valves 177L1 and 177L2 are arranged in parallel. Bleed valves 177R1 and 177R2 are spool valves that control the bleed flow rate of the hydraulic oil discharged by main pump 14R. Bleed valves 177R1 and 177R2 are arranged in parallel. Bleed valves 177L1, 177L2, 177R1, and 177R2 correspond to bleed valve 177 in FIG. 2.

Bleed valves 177L1, 177L2, 177R1, and 177R2 have, for example, a first valve position with a minimum opening area (0% opening) and a second valve position with a maximum opening area (100% opening). Bleed valves 177L and 177R can be moved steplessly between the first valve position and the second valve position. The maximum opening area of bleed valve 177L1 is smaller than the maximum opening area of bleed valve 177L2. In other words, bleed valve 177L1 is a valve capable of controlling minute opening changes. The maximum opening area of bleed valve 177L2 is larger than the maximum opening area of bleed valve 177L1. In other words, bleed valve 177L2 is a valve capable of large opening changes. The maximum opening area of bleed valve 177R1 is smaller than the maximum opening area of bleed valve 177R2. In other words, bleed valve 177R1 is a valve capable of controlling minute changes in opening. It is specialized for minute changes in opening. The maximum opening area of bleed valve 177R2 is larger than the maximum opening area of bleed valve 177R1. In other words, bleed valve 177R2 is a valve capable of large changes in opening.

The regulators 13L, 13R control the discharge volume of the main pumps 14L, 14R by adjusting the swash plate tilt angle of the main pumps 14L, 14R. The regulators 13L, 13R correspond to the regulator 13 in FIG. 2. For example, the controller 30 adjusts the swash plate tilt angle of the main pumps 14L, 14R with the regulators 13L, 13R in response to an increase in the discharge pressure of the main pumps 14L, 14R to reduce the discharge volume. This is to prevent the absorption horsepower of the main pump 14, which is expressed as the product of the discharge pressure and the discharge volume, from exceeding the output horsepower of the engine 11.

The arm operating lever 26A is an example of the operating device 26, and is used to operate the arm 5. The arm operating lever 26A uses hydraulic oil discharged by the pilot pump 15 to introduce a control pressure according to the lever operation amount to the pilot ports of the control valves 176L and 176R. Specifically, when the arm operating lever 26A is operated in the arm closing direction, it introduces hydraulic oil to the right pilot port of the control valve 176L and introduces hydraulic oil to the left pilot port of the control valve 176R. When the arm operating lever 26A is operated in the arm opening direction, it introduces hydraulic oil to the left pilot port of the control valve 176L and introduces hydraulic oil to the right pilot port of the control valve 176R.

The boom operation lever 26B is an example of an operation device 26, and is used to operate the boom 4. The boom operation lever 26B uses hydraulic oil discharged by the pilot pump 15 to introduce a control pressure according to the lever operation amount to the pilot ports of the control valves 175L and 175R. Specifically, when the boom operation lever 26B is operated in the boom-up direction, it introduces hydraulic oil to the right pilot port of the control valve 175L and introduces hydraulic oil to the left pilot port of the control valve 175R. When the boom operation lever 26B is operated in the boom-down direction, it introduces hydraulic oil to the left pilot port of the control valve 175L and introduces hydraulic oil to the right pilot port of the control valve 175R.

The discharge pressure sensors 28L and 28R are examples of discharge pressure sensors 28, which detect the discharge pressure of the main pumps 14L and 14R and output the detected value to the controller 30.

Operation pressure sensors 29A and 29B are examples of operation pressure sensors 29, and detect the operation contents of the operator on arm operation lever 26A and boom operation lever 26B in the form of pressure, and output the detected value to controller 30. The operation contents include, for example, the lever operation direction, the lever operation amount (lever operation angle), etc.

The left and right travel levers (or pedals), bucket operation lever, and swing operation lever (none shown) are operation devices for operating the travel of the lower travel body 1, the opening and closing of the bucket 6, and the swing of the upper swing body 3, respectively. Like the arm operation lever 26A and the boom operation lever 26B, these operation devices use hydraulic oil discharged from the pilot pump 15 to introduce a control pressure according to the lever operation amount (or pedal operation amount) into either the left or right pilot port of the control valve corresponding to each hydraulic actuator. The operation content of each of these operation devices by the operator is detected in the form of pressure by the corresponding operation pressure sensor, like the operation pressure sensors 29A and 29B, and the detected value is output to the controller 30.

The controller 30 receives the outputs of the operating pressure sensors 29A, 29B, etc., and outputs control commands to the regulators 13L, 13R as necessary to change the discharge rates of the main pumps 14L, 14R. It also outputs current commands to the proportional valves 31L1, 31L2, 31R1, 31R2 as necessary to change the opening areas of the bleed valves 177L1, 177L2, 177R1, 177R2.

The proportional valves 31L1, 31L2, 31R1, and 31R2 adjust the secondary pressure introduced from the pilot pump 15 to the pilot ports of the bleed valves 177L1, 177L2, 177R1, and 177R2 in response to a current command output by the controller 30. The proportional valves 31L1, 31L2, 31R1, and 31R2 correspond to the proportional valve 31 in FIG. 2.

The proportional valve 31L1 is capable of adjusting the secondary pressure so that the bleed valve 177L1 can be stopped at any position between the first valve position and the second valve position. The proportional valve 31L2 is capable of adjusting the secondary pressure so that the bleed valve 177L2 can be stopped at any position between the first valve position and the second valve position. The proportional valve 31R1 is capable of adjusting the secondary pressure so that the bleed valve 177R1 can be stopped at any position between the first valve position and the second valve position. The proportional valve 31R2 is capable of adjusting the secondary pressure so that the bleed valve 177R2 can be stopped at any position between the first valve position and the second valve position.

Next, we will explain the negative control (hereinafter referred to as "negative control") used in the hydraulic circuit shown in Figure 3.

In the pipe 42L, a negative control throttle 18L is disposed between the most downstream bleed valves 177L1, 177L2 and the hydraulic oil tank. In the pipe 42R, a negative control throttle 18R is disposed between the most downstream bleed valves 177R1, 177R2 and the hydraulic oil tank. The flow of hydraulic oil passing through the bleed valves 177L1, 177L2 to the hydraulic oil tank is restricted by the negative control throttle 18L. The flow of hydraulic oil passing through the bleed valves 177R1, 177R2 to the hydraulic oil tank is restricted by the negative control throttle 18R. The negative control throttles 18L, 18R generate a control pressure (hereinafter referred to as "negative control pressure") for controlling the regulators 13L, 13R. The negative control pressure sensors 19L, 19R are sensors for detecting the negative control pressure and output the detected value to the controller 30.

In this embodiment, the negative control apertures 18L and 18R are variable apertures whose opening area changes. However, the negative control apertures 18L and 18R may also be fixed apertures.

The controller 30 controls the discharge volume of the main pumps 14L, 14R by adjusting the swash plate tilt angle of the main pumps 14L, 14R according to the negative control pressure. Hereinafter, the relationship between the negative control pressure and the discharge volume of the main pumps 14L, 14R is referred to as the "negative control characteristic." The negative control characteristic may be stored in a ROM or the like as a reference table, for example, or may be expressed by a predetermined formula. The controller 30, for example, refers to a table that represents a predetermined negative control characteristic, and decreases the discharge volume of the main pumps 14L, 14R as the negative control pressure increases, and increases the discharge volume of the main pumps 14L, 14R as the negative control pressure decreases.

Specifically, in the standby state in which none of the hydraulic actuators are operated as shown in FIG. 3, the hydraulic oil discharged from the main pumps 14L and 14R passes through the bleed valves 177L1, 177L2, 177R1, and 177R2 to the negative control throttles 18L and 18R. The flow of hydraulic oil passing through the bleed valves 177L1, 177L2, 177R1, and 177R2 increases the negative control pressure generated upstream of the negative control throttles 18L and 18R. As a result, the controller 30 reduces the discharge rate of the main pumps 14L and 14R to a predetermined allowable minimum discharge rate, suppressing pressure loss (pumping loss) when the discharged hydraulic oil passes through the pipes 42L and 42R. This predetermined allowable minimum discharge rate in the standby state is an example of a bleed flow rate, and is hereinafter referred to as the "standby flow rate."

On the other hand, when any of the hydraulic actuators is operated, the hydraulic oil discharged from the main pumps 14L and 14R flows into the hydraulic actuator through the control valve corresponding to the hydraulic actuator to be operated. Therefore, the bleed flow rate through the bleed valves 177L1, 177L2, 177R1, and 177R2 to the negative control throttles 18L and 18R decreases, and the negative control pressure generated upstream of the negative control throttles 18L and 18R decreases. As a result, the controller 30 increases the discharge rate of the main pumps 14L and 14R to supply sufficient hydraulic oil to the hydraulic actuator to be operated, ensuring the drive of the hydraulic actuator to be operated. In the following, the flow rate of hydraulic oil flowing into the hydraulic actuator is referred to as the "actuator flow rate." In this case, the flow rate of hydraulic oil discharged from the main pumps 14L and 14R corresponds to the sum of the actuator flow rate and the bleed flow rate.

With the above-mentioned configuration, the hydraulic circuit of FIG. 3 can reliably supply sufficient hydraulic oil from the main pumps 14L and 14R to the hydraulic actuators to be operated when the hydraulic actuators are operated. In addition, in the standby state, unnecessary consumption of hydraulic energy can be suppressed. This is because the bleed flow rate can be reduced to the standby flow rate.

In order to improve the operability of the excavator, it is necessary to control the small opening of the bleed valve 177. Also, when decelerating the hydraulic actuators (boom cylinder 7, arm cylinder 8, bucket cylinder 9, left-side traveling hydraulic motor 1A, right-side traveling hydraulic motor 1B, swing hydraulic motor 2A), it is necessary to quickly guide the hydraulic oil discharged from the main pump 14 to the hydraulic oil tank, and it is therefore necessary to increase the maximum opening of the bleed valve 177.

In this embodiment, therefore, the line 42L connecting the main pump 14L to the hydraulic oil tank has bleed valves 177L1 and 177L2 arranged in parallel. Similarly, the line 42R connecting the main pump 14R to the hydraulic oil tank has bleed valves 177R1 and 177R2 arranged in parallel. Bleed valves 177L1 and 177R1 are small flow rate bleed valves with high control resolution of the opening area. Bleed valves 177L2 and 177R2 are large flow rate bleed valves with large maximum opening area.

The controller 30 includes a bleed valve opening area determination unit 301, a current value generation unit 302, and a memory unit 303.

The bleed valve opening area determination unit 301 determines the opening area of the bleed valves 177L1, 177L2, 177R1, and 177R2 based on the operation amount of the hydraulic actuators (boom cylinder 7, arm cylinder 8, bucket cylinder 9, left-side traveling hydraulic motor 1A, right-side traveling hydraulic motor 1B, and swing hydraulic motor 2A).

The current value generating unit 302 generates a current command to be output to the proportional valve 31 (proportional valves 31L1, 31L2, 31R1, 31R2). The proportional valve 31 adjusts the secondary pressure introduced to the pilot port of the bleed valve 177 according to the current command output by the controller 30. The bleed valve 177 moves a spool based on the secondary pressure introduced to the pilot port, changing the opening area.

The storage unit 303 stores tables and other data used for control. The tables stored in the storage unit 303 will be described later with reference to FIG. 5.

Here, we will explain the bleed valve opening area control in the excavator according to this embodiment, comparing it with the excavator according to the reference example.

First, the shovel according to the reference example will be described. The shovel according to this embodiment is provided with two bleed valves 177L1, 177L2 (177R1, 177R2) for each of the pipelines 42L (42R), whereas the shovel according to the reference example is different in that it has one bleed valve for each of the pipelines 42L (42R). The rest of the configuration is similar, and duplicated explanations will be omitted. In the following explanation, an example will be described in which the operator operates the boom operating lever 26B to cause the shovel to raise the boom 4.

When the operator operates the boom operation lever 26B in the boom-raising direction, a control pressure corresponding to the amount of lever operation (hereinafter also referred to as the "boom-raising pilot pressure") is introduced into the pilot ports of the control valves 175L and 175R. In addition, the boom-raising pilot pressure is detected by the operation pressure sensor 29B and input to the controller 30.

Figure 4(a) is a graph showing the relationship between boom raising pilot pressure and bleed valve opening area. As shown in Figure 4(a), the controller 30 according to the reference example stores a table that associates boom raising pilot pressure with bleed valve opening area. Here, the maximum opening area of the bleed valve opening area is set to S1 corresponding to the control range of the boom raising pilot pressure. The controller 30 according to the reference example determines the bleed valve opening area based on the boom raising pilot pressure detected by the operating pressure sensor 29B and the table.

Figure 4(b) is a graph showing the relationship between the bleed valve secondary pressure and the bleed valve opening area in the bleed valve of the reference example. As shown in Figure 4(b), the controller 30 of the reference example stores a table that associates the secondary pressure of the bleed valve with the bleed valve opening area as characteristic information of the bleed valve. The controller 30 of the reference example determines the bleed valve secondary pressure based on the determined bleed valve opening area and the table.

For example, as shown in FIG. 4, when the boom raising pilot pressure is P1, the bleed valve secondary pressure is C1. When the boom raising pilot pressure is P2, the bleed valve secondary pressure is C2. When the boom raising pilot pressure is P3, the bleed valve secondary pressure is C3.

The controller 30 according to the reference example also stores a table (not shown) that associates the current command value with the opening area of the proportional valve 31 (corresponding to the "bleed valve secondary pressure") as characteristic information of the proportional valve 31. The controller 30 according to the reference example determines the current command value for the proportional valve 31 based on the determined bleed valve secondary pressure and the table. For example, in the case of boom raising pilot pressure P1, the opening area of the proportional valve 31 is determined so as to become the bleed valve secondary pressure C1, and the current command value for the proportional valve 31 is determined based on the determined opening area of the proportional valve 31 and the table. The current command value for the proportional valve 31 is determined similarly for the cases of boom raising pilot pressures P2 and P3.

As described above, the controller 30 refers to various tables and determines the current command value for the proportional valve 31 from the boom raising pilot pressure. The controller 30 controls the bleed valve 177 by outputting the determined current command value to the proportional valve 31.

As shown in FIG. 4(b), the excavator according to the reference example is configured to be able to control the opening area from maximum opening area S1 to opening area 0 with one bleed valve. Therefore, the bleed valve of the excavator according to the reference example corresponds to the control range of the bleed valve secondary pressure from opening area 0 to maximum opening area S1, making it difficult to increase the resolution of the control of the bleed valve opening area.

Next, the excavator according to this embodiment will be described. Here, the control of the bleed valves 177L1 and 177L2 of the pipeline 42L will be described as an example. The control of the bleed valves 177R1 and 177R2 of the pipeline 42R is similar, so duplicated explanations will be omitted.

The excavator according to this embodiment is provided with two bleed valves 177L1, 177L2 for each pipeline 42L. The bleed valves 177L1, 177L2 are configured so that the opening area can be controlled individually via proportional valves 31L1, 31L2. In the following explanation, an example will be given in which the operator operates the boom operation lever 26B to cause the excavator to raise the boom 4.

When the operator operates the boom operation lever 26B in the boom-raising direction, a control pressure (boom-raising pilot pressure) corresponding to the amount of lever operation is introduced into the pilot ports of the control valves 175L and 175R. In addition, the boom-raising pilot pressure is detected by the operation pressure sensor 29B and input to the controller 30.

Figure 5(a) is a graph showing the relationship between boom raising pilot pressure and bleed valve opening area. As shown in Figure 5(a), the controller 30 according to this embodiment stores a table that associates boom raising pilot pressure with bleed valve opening area. Note that the table shown in Figure 5(a) is the same as the table shown in Figure 4(a). The controller 30 according to this embodiment determines the bleed valve opening area based on the boom raising pilot pressure detected by the operating pressure sensor 29B and the table.

Figure 5(b) is a graph showing the relationship between the bleed valve secondary pressure and the bleed valve opening area in the bleed valve 177L1 for small opening in this embodiment. Figure 5(c) is a graph showing the relationship between the bleed valve secondary pressure and the bleed valve opening area in the bleed valve 177L2 for large flow rate in this embodiment. The controller 30 according to this embodiment stores a table in which the secondary pressure of the bleed valve shown in Figure 5(b) and the bleed valve opening area correspond to each other as characteristic information of the bleed valve 177L1 for small opening. In addition, the controller 30 according to this embodiment stores a table in which the secondary pressure of the bleed valve shown in Figure 5(c) and the bleed valve opening area correspond to each other as characteristic information of the bleed valve 177L2 for large flow rate. The controller 30 according to this embodiment determines the bleed valve secondary pressures of the bleed valves 177L1 and 177L2 based on the determined bleed valve opening area and the table.

For example, as shown in Figure 5, for boom raising pilot pressure P1, the bleed valve secondary pressure of bleed valve 177L1 is A1, and the bleed valve secondary pressure of bleed valve 177L2 is B0 (valve fully closed). For boom raising pilot pressure P2, the bleed valve secondary pressure of bleed valve 177L1 is A2, and the bleed valve secondary pressure of bleed valve 177L2 is B0 (valve fully closed). For boom raising pilot pressure P3, the bleed valve secondary pressure of bleed valve 177L1 is A3, and the bleed valve secondary pressure of bleed valve 177L2 is B0 (valve fully closed). For boom raising pilot pressure P4, the bleed valve opening area is S4 (see Figure 5(a)). Here, the opening area of bleed valve 177L1 is S3, the opening area of bleed valve 177L2 is S4-S3, and the sum of the opening areas of bleed valve 177L1 and bleed valve 177L2 is S3. That is, the bleed valve secondary pressure of bleed valve 177L1 is A4, and the bleed valve secondary pressure of bleed valve 177L2 is B4.

Here, the opening area S3 is a threshold value for determining whether the opening area is controlled using only the bleed valve 177L1 for small openings, or whether the opening area is controlled using both the bleed valve 177L1 for small flow rates and the bleed valve 177L2 for large flow rates. The opening area S3 may be the maximum opening area of the bleed valve 177L1, or may be set to a value smaller than the maximum opening area of the bleed valve 177L1.

In addition, the controller 30 according to this embodiment stores a table (not shown) that associates the current command value with the opening area of the proportional valve 31 (corresponding to the "bleed valve secondary pressure") as characteristic information of the proportional valve 31. The controller 30 according to this embodiment determines the current command value to the proportional valve 31 based on the determined bleed valve secondary pressure and the table. For example, in the case of boom raising pilot pressure P1, the opening area of the proportional valve 31L1 is determined so that the secondary pressure of the bleed valve 177L1 becomes the bleed valve secondary pressure A1, and the current command value to the proportional valve 31L1 is determined based on the determined opening area of the proportional valve 31L1 and the table. The opening area of the proportional valve 31L2 is determined so that the secondary pressure of the bleed valve 177L2 becomes the bleed valve secondary pressure B0, and the current command value to the proportional valve 31L2 is determined based on the determined opening area of the proportional valve 31L2 and the table. Similarly, the current command value for proportional valves 31L1 and 31L2 is determined for boom raising pilot pressures P2 to P4.

In addition, the pressure value detected by the negative control pressure sensor 19L is input to the controller 30 in this embodiment. The controller 30 uses this detected value of the negative control pressure sensor 19L to control the bleed valve 177L1 so that the determined bleed valve secondary pressure is reached.

As described above, the controller 30 refers to various tables and determines the current command value for the proportional valve 31 from the boom raising pilot pressure. The controller 30 controls the bleed valve 177 by outputting the determined current command value to the proportional valve 31.

As shown in FIG. 5(b), the shovel according to this embodiment is configured such that the bleed valve 177L1 for small opening can be controlled from an opening area S3 to an opening area 0. Therefore, the bleed valve of the shovel according to this embodiment has an opening area from 0 to an opening area S3 corresponding to the control range of the bleed valve secondary pressure, and therefore can have a higher resolution for controlling the bleed valve opening area compared to the reference example.

Figure 6 is a flowchart that explains an example of a method for determining the opening area of the two bleed valves 177L1 and 177L2.

In step S101, the controller 30 determines the bleed valve opening area S (= the sum of the opening area of bleed valve 177L1 and the opening area of bleed valve 177L2) based on the boom raising pilot pressure and the table shown in FIG. 5(a).

In step S102, the controller 30 determines whether the determined bleed valve opening area S is equal to or less than the opening area S3. If the determined bleed valve opening area S is equal to or less than the opening area S3 (S102, Yes), the processing of the controller 30 proceeds to step S103. If the determined bleed valve opening area S is not equal to or less than the opening area S3 (S102, No), the processing of the controller 30 proceeds to step S105.

In step S103, the controller 30 determines the secondary pressure of the bleed valve 177L1 for the small opening based on the table shown in FIG. 5(b), with the opening area S determined in step S101 as the opening area of the bleed valve 177L1 for the small opening.

In step S104, the controller 30 sets the opening area of the high flow bleed valve 177L2 to 0 and determines the secondary pressure of the bleed valve 177L2 based on the table shown in FIG. 5(c). Then, the process of the controller 30 proceeds to step S107.

In step S105, the controller 30 determines the secondary pressure of the bleed valve 177L1 based on the table shown in FIG. 5(b), with the opening area of the bleed valve 177L1 for small opening as the opening area S3.

In step S106, the controller 30 determines the secondary pressure of the bleed valve 177L2 based on the table shown in FIG. 5(c), taking the opening area of the large flow bleed valve 177L2 as the difference (S-S3) between the opening area S determined in step S101 and the opening area S3 of the small opening bleed valve 177L1. As a result, the sum of the opening area of the small opening bleed valve 177L1 and the opening area of the large flow bleed valve 177L2 becomes the opening area S determined in step S101. Then, the processing of the controller 30 proceeds to step S107.

In step S107, the controller 30 determines the current command values to be output to the proportional valves 31L1 and 31L2 based on the secondary pressures of the bleed valves 177L1 and 177L2.

In step S108, the controller 30 outputs a current command value to the proportional valves 31L1 and 31L2.

With this configuration, for example, when the control lever 26B is in the neutral state, the bleed valve opening area is determined to be S1 (see FIG. 5), and the secondary pressure of each bleed valve is determined so that the opening area of the small opening bleed valve 177L1 is S3, and the opening area of the large flow bleed valve 177L2 is S1-S3. By tilting the control lever 26B from the neutral state, first, the opening area of the small opening bleed valve 177L1 remains S3, while the opening area of the large flow bleed valve 177L2 becomes smaller (see S102, No, S105, S106).

When the control lever 26B is further tilted and the bleed valve opening area determined in step S101 becomes S3, the opening area of the small opening bleed valve 177L1 remains at S3 and the large flow bleed valve 177L2 closes. Then, by further tilting the control lever 26B, the opening area of the small opening bleed valve 177L1 becomes smaller while the large flow bleed valve 177L2 remains closed (S102, Yes, see S103, S104).

Figure 7 is a graph showing the relationship between the lever operation amount and the pressure of hydraulic oil supplied to the hydraulic actuator in the excavators according to this embodiment and the reference example. The graph at the ideal value of 700 is shown by a two-dot chain line.

Here, it is assumed that the bleed valve opening area deviates from the ideal value due to an error caused by the control resolution of the bleed valve secondary pressure. In the excavator according to the reference example, the dashed line 711 shows a case in which the bleed valve opening area is smaller than the ideal value due to an error in the bleed valve secondary pressure. Also, in the excavator according to the reference example, the dashed line 712 shows a case in which the bleed valve opening area is larger than the ideal value due to an error in the bleed valve secondary pressure. As shown in FIG. 4(b), the bleed valve opening area varies greatly with respect to the error in the bleed valve secondary pressure. For this reason, the deviation in pressure relative to the lever operation amount also becomes large, as shown in FIG. 7.

In contrast, in the excavator according to this embodiment, the large flow bleed valve 177L2 is closed and the opening area is controlled by the small opening bleed valve 177L1, so the resolution of the bleed valve opening area can be increased. In the excavator according to this embodiment, the solid line 701 shows a case where the bleed valve opening area is smaller than the ideal value due to an error in the bleed valve secondary pressure. Also, in the excavator according to this embodiment, the solid line 702 shows a case where the bleed valve opening area is larger than the ideal value due to an error in the bleed valve secondary pressure. As shown in FIG. 7, the pressure relative to the lever operation amount can be brought closer to the ideal value 700. This allows the hydraulic actuator to operate optimally in response to the lever operation amount, improving the operability of the excavator.

The excavator in this embodiment has been described as being equipped with a bleed valve for a small opening and a bleed valve for a large flow rate, but this is not limited to this. A relief valve may be used instead of the bleed valve for a large flow rate.

Figure 8 is a schematic diagram showing another example of the configuration of a hydraulic circuit mounted on an excavator. Figure 9(a) is a graph showing the relationship between the bleed valve secondary pressure and the bleed valve opening area for bleed valves 177L1 and 177R1 in another example of the configuration. Figure 9(b) is a graph showing the relationship between the relief valve secondary pressure and the bleed valve opening area for relief valves 177L3 and 177R3 in another example of the configuration.

As shown in FIG. 8, relief valves 177L3 and 177R3 are provided instead of the high flow bleed valves 177L2 and 177R2. The rest of the configuration is the same as the configuration example shown in FIG. 3, so repeated explanations will be omitted.

The bleed valves 177L1 and 177R1 for small openings are configured to be able to control the opening area from S5 to 0. Therefore, the bleed valves of the excavator according to the other configuration examples have an opening area from 0 to S5 that corresponds to the control range of the bleed valve secondary pressure, so that the resolution of the control of the bleed valve opening area can be increased compared to the reference example.

The opening area S5 is a threshold value for determining whether to control the opening area using only the bleed valves 177L1 and 177R1, or to use both the bleed valves 177L1 and 177R1 and the relief valves 177L3 and 177R3. The opening area S5 may be the maximum opening area of the bleed valves 177L1 and 177R1, or may be set to a value smaller than the maximum opening area of the bleed valves 177L1 and 177R1.

The relief valves 177L3 and 177R3 are valves that open and close when a secondary pressure controlled by the proportional valves 31L2 and 31R2 is introduced. As shown in FIG. 9(b), the relief valves 177L3 and 177R3 are capable of taking a maximum opening area S1 and an opening area of 0.

In other configuration examples, the bleed valves 177L1 and 177R1 for small openings may have a larger opening area S5 (S5>S3) than the configuration example shown in FIG. 3. This allows the control range to be expanded.

According to another configuration example, the valves arranged in parallel with the bleed valves 177L1 and 177R1 can be replaced with relief valves (on-off valves) that can control the opening area, thereby reducing costs. In addition, the space occupied can be reduced.

The above describes the form for implementing the present invention, but the above content does not limit the content of the invention, and various modifications and improvements are possible within the scope of the present invention.

For example, in FIG. 3, the control valves 171, 173, 175L, and 176L that control the flow of hydraulic oil from the main pump 14L toward the hydraulic actuator are connected in parallel to each other between the main pump 14L and the hydraulic oil tank. However, the control valves 171, 173, 175L, and 176L may also be connected in series between the main pump 14L and the hydraulic oil tank. In this case, regardless of the valve position of the spool that constitutes each control valve, the pipe 42L can supply hydraulic oil to the adjacent control valve located downstream without being blocked by the spool.

Similarly, the control valves 172, 174, 175R, and 176R that control the flow of hydraulic oil from the main pump 14R toward the hydraulic actuator are connected in parallel to each other between the main pump 14R and the hydraulic oil tank. However, the control valves 172, 174, 175R, and 176R may also be connected in series between the main pump 14R and the hydraulic oil tank. In this case, regardless of the valve position of the spool that constitutes each control valve, the pipe 42R can supply hydraulic oil to the adjacent control valve located downstream without being blocked by the spool.

In addition, when the control valves 171, 173, 175L, and 176L are connected in series between the main pump 14L and the hydraulic oil tank, and the control valves 172, 174, 175R, and 176R are connected in series between the main pump 14R and the hydraulic oil tank, the configuration may include center bypass lines 40L, 40R and parallel lines 42L, 42R.

In the above embodiment, a hydraulic operating device is used as the operating device 26, but an electric operating device may also be used. FIG. 10 shows an example of the configuration of an operating system including an electric operating device. Specifically, the operating system of FIG. 10 is an example of a boom operating system, and is mainly composed of a pilot pressure operated control valve 17, a boom operating lever 26B as an electric operating lever, a controller 30, a solenoid valve 60 for boom raising operation, and a solenoid valve 62 for boom lowering operation. The operating system of FIG. 10 can also be similarly applied to an arm operating system, a bucket operating system, etc.

As shown in FIG. 3, the pilot pressure operated control valve 17 includes control valves 175L, 175R for the boom cylinder 7. The solenoid valve 60 is configured to adjust the flow area of the oil passage connecting the pilot pump 15 to the right (raising side) pilot port of the control valve 175L and the left (raising side) pilot port of the control valve 175R. The solenoid valve 62 is configured to adjust the flow area of the oil passage connecting the pilot pump 15 to the right (lowering side) pilot port of the control valve 175R.

When manual operation is performed, the controller 30 generates a boom-raising operation signal (electrical signal) or a boom-lowering operation signal (electrical signal) in response to an operation signal (electrical signal) output by an operation signal generating unit of the boom operation lever 26B. The operation signal output by the operation signal generating unit of the boom operation lever 26B is an electrical signal that changes depending on the amount and direction of operation of the boom operation lever 26B.

Specifically, when the boom operation lever 26B is operated in the boom-up direction, the controller 30 outputs a boom-up operation signal (electrical signal) corresponding to the lever operation amount to the solenoid valve 60. The solenoid valve 60 adjusts the flow path area according to the boom-up operation signal (electrical signal) and controls the pilot pressure acting on the right (up) pilot port of the control valve 175L and the left (up) pilot port of the control valve 175R. Similarly, when the boom operation lever 26B is operated in the boom-down direction, the controller 30 outputs a boom-down operation signal (electrical signal) corresponding to the lever operation amount to the solenoid valve 62. The solenoid valve 62 adjusts the flow path area according to the boom-down operation signal (electrical signal) and controls the pilot pressure acting on the right (down) pilot port of the control valve 175R.

When performing automatic control, the controller 30 generates a boom-raising operation signal (electrical signal) or a boom-lowering operation signal (electrical signal) in response to a correction operation signal (electrical signal) instead of the operation signal output by the operation signal generating unit of the boom operation lever 26B. The correction operation signal may be an electrical signal generated by the controller 30, or may be an electrical signal generated by an external control device other than the controller 30.

1A Hydraulic motor for left side travel (hydraulic actuator)
1B Right side travel hydraulic motor (hydraulic actuator)
2A Swing hydraulic motor (hydraulic actuator)
7 Boom cylinder (hydraulic actuator)
8 Arm cylinder (hydraulic actuator)
9 Bucket cylinder (hydraulic actuator)
14 Main pump 15 Pilot pump 17 Control valve 26 Operation device 26A Arm operation lever 26B Boom operation lever 29 Operation pressure sensor 29A, 29B Operation pressure sensor 30 Controller 31 Proportional valve 42L, 42R Pipe (oil line)
171 to 176 Control valve 177 Bleed valve 301 Bleed valve opening area determination unit 302 Current value generation unit 303 Storage unit

Claims (6)

A hydraulic pump;
a hydraulic actuator driven by hydraulic fluid discharged from the hydraulic pump;
an oil passage capable of supplying hydraulic oil discharged by the hydraulic pump to the hydraulic actuator;
a control valve provided in the oil passage for controlling a flow rate of hydraulic oil supplied to the hydraulic actuator;
a first bleed valve provided in the oil passage and configured to control a flow rate of hydraulic oil flowing to a hydraulic oil tank without passing through the hydraulic actuator;
A second bleed valve is provided in the oil passage and is provided in parallel with the first bleed valve ,
The first bleed valve has a function specialized for a minute change in opening,
The second bleed valve has a function specialized for large opening changes.
Shovel. if the required opening is less than the maximum opening of the first bleed valve, only the first bleed valve is operated;
The shovel according to claim 1 . activating the second bleed valve if the required opening is greater than the maximum opening of the first bleed valve;
The shovel according to claim 1 or 2 . Further comprising an operating lever,
When the operating lever is not operated, the first bleed valve is open.
The shovel according to any one of claims 1 to 3 . When the operating lever is operated,
the second bleed valve closes before the first bleed valve closes;
The shovel according to claim 4 . When the operating lever is operated,
the first bleed valve closes after the second bleed valve closes;
The shovel according to claim 5 .

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