Control devices and construction machinery

Abstract

The present invention provides a control device and a construction machine. The control device of the present invention comprises: a control valve that controls the flow rate from a pump that delivers a fluid to control the drive of a driving body driven by the fluid; and a pair of relief valves that are arranged in a pair of supply and exhaust passages between the driving body and the control valve and reduce the pressure of the fluid in any one of the pair of supply and exhaust passages based on an external signal.

Description

Technical Field

[0001] The invention relates to a control device and a construction machine. Background Art

[0002] Construction machinery includes: various hydraulic actuators for driving a revolving body (cab), a bucket, a boom, etc.; and a hydraulic drive device for driving these hydraulic actuators. The hydraulic drive device includes: an operating unit; a hydraulic pump for supplying oil to the hydraulic actuator; and a hydraulic control valve for controlling the flow rate of oil supplied to each hydraulic actuator. In order to improve the operability of the drive device, various technologies have been proposed.

[0003] For example, there is a control device in which, when an operation unit is operated when rotating a rotating body, the rotating body automatically rotates within a set braking range, and the rotation of the rotating body automatically stops at the end of the braking range.

[0004] As a specific structure of such a control device, for example, a relief valve is provided between the hydraulic actuator and the hydraulic control valve. In addition, a discharge oil circuit is provided in the relief valve, and an electromagnetic proportional valve is provided downstream of the discharge oil circuit via a check valve. The downstream side of the electromagnetic proportional valve is connected to the port of the hydraulic pump. In addition, the pump oil circuit is connected to the tank oil circuit.

[0005] Based on such a structure, if the tank oil circuit is throttled, the pressure of the pump oil circuit is increased. If the pressure of the pump oil circuit is increased, the check valve of the discharge oil circuit is closed. In addition, the pressure increase of the pump oil circuit acts on the rear section of the electromagnetic proportional valve to increase the pressure of the discharge oil circuit. As a result, the braking force acts on the hydraulic actuator.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Laid-Open No. 6-24688 Summary of the invention

[0009] Problem that the invention aims to solve

[0010] However, when the pressure of the pump oil circuit is increased by throttling the tank oil circuit as described above, the pressure of the supply passage for supplying oil to the hydraulic actuator is also increased at the same time. Therefore, there is a possibility that a stable braking force cannot be obtained due to the operation of the hydraulic actuator.

[0011] Furthermore, since the throttling of the tank oil line has the function of adjusting the pressure of the pump oil line in order to improve the operability of the hydraulic actuator, there is a possibility that the operability of the hydraulic actuator will be reduced.

[0012] The present invention provides a control device and a construction machine that can obtain a stable braking force with a simple structure without impairing the operability of a driving body driven by the above-mentioned fluid.

[0013] Solutions for solving problems

[0014] A control device of one technical solution of the present invention comprises: a control valve, which controls the flow rate from a pump that delivers fluid to perform drive control of a driving body driven by the fluid; and a pair of overflow valves, which are arranged in a pair of supply and exhaust passages between the driving body and the control valve, and reduce the pressure of the fluid in any one of the pair of supply and exhaust passages based on an external signal.

[0015] With such a configuration, when the pressure of the fluid in one of the pair of supply and exhaust passages is reduced by the relief valve, no extra load is applied to the driving body, and the driving body can be automatically operated. Therefore, the operability of the driving body is not impaired.

[0016] On the other hand, if the relief valve is closed to increase the pressure of the fluid in the one supply and discharge passage, a stable braking force can be obtained.

[0017] In the above structure, the control device may include an operating unit that outputs a pilot pressure for driving the control valve, and the pair of relief valves may each include a first port for inputting the pilot pressure and a second port for inputting the pressure of the fluid in the supply and exhaust passage.

[0018] By configuring in this way, the pressure difference between the pressure of the fluid in the supply and discharge passage and the pilot pressure can be used as a signal, and the relief valve can be opened and closed based on the signal. That is, when the pressure of the fluid in the supply and discharge passage is higher than the pilot pressure, the relief valve is opened. In contrast, when the pilot pressure is higher than the pressure of the fluid in the supply and discharge passage, the relief valve is closed. The opening and closing of such a relief valve can be used to release the braking force applied to the driving body, or to make the braking force act on the driving body. Therefore, the control device can be set to a simple structure and a stable braking force can be obtained.

[0019] In the above configuration, the control device may include a switching valve provided between the operation unit and the first port and capable of switching between connection between the first port and the operation unit and connection between the first port and a tank from which the fluid is discharged.

[0020] With this configuration, the braking force can be reliably obtained based on the pressure difference between the pressure of the fluid in the supply and discharge passage and the pilot pressure without impairing the operability of the driving body.

[0021] In the above configuration, the control device may include another control valve capable of driving the relief valve according to a driving state of the driving body.

[0022] By configuring in this way, a braking force can be generated according to the driving condition of the driving body. Therefore, the convenience of the control device can be improved, and safety can also be improved.

[0023] The control device of another technical scheme of the present invention comprises: a control valve, which controls the flow rate from a pump that delivers a fluid to perform drive control of a driving body driven by the fluid; a pair of relief valves, which are arranged in a pair of supply and exhaust passages between the driving body and the control valve and are connected to a tank for discharging the fluid, and reduce the pressure of the fluid at any one of the pair of supply and exhaust passages based on an external signal, and when one of the relief valves in the pair of relief valves is opened, the other relief valve is closed, and when the relief valve arranged in the one of the supply and exhaust passages is closed, the fluid flowing out to one of the pair of supply and exhaust passages through the control valve is not discharged to the tank at the closed relief valve, but is discharged to the tank via the driving body, and when the relief valve arranged in the one of the supply and exhaust passages is opened, the fluid is discharged to the tank via the open relief valve.

[0024] By configuring in this way, the braking force applied to the driving body can be released or the braking force can be applied to the driving body by opening and closing the relief valve. Therefore, the control device can be made into a simple structure and a stable braking force can be obtained.

[0025] A construction machine according to another aspect of the present invention includes the above-mentioned control device, wherein the pump is a hydraulic pump, and the driving body is a hydraulic actuator.

[0026] By configuring in this way, it is possible to provide a construction machine that can obtain a stable braking force with a simple structure without sacrificing operability.

[0027] Effects of the Invention

[0028] The control device and construction machine described above can obtain stable braking force with a simple structure without sacrificing operability. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic structural diagram of a construction machine according to a first embodiment of the present invention.

[0030] Figure 2 It is a schematic structural diagram of a construction machine according to a second embodiment of the present invention.

[0031] Description of Reference Numerals

[0032] 1. 201, driving device; 2. hydraulic motor (driving body, hydraulic actuator); 3. hydraulic pump (pump); 4. operating unit; 5. 205, control device; 9. control valve; 13a, 13b, supply and exhaust passages; 17a, 17b, overflow valve; 18, first port; 19, second port; 20, third switching valve (switching valve); 33, third proportional control valve (other control valves); 34, fourth proportional control valve (other control valves); 100, 200, construction machinery. DETAILED DESCRIPTION

[0033] Next, embodiments of the present invention will be described based on the drawings.

[0034] First Embodiment

[0035] (Construction machinery)

[0036] Figure 1 It is a schematic structural diagram of the construction machine 100.

[0037] The construction machine 100 is a crane vehicle such as an off-road crane, and includes a revolving body 101 and a driving device 1 for driving the revolving body 101 to revolve.

[0038] (Drive device)

[0039] like Figure 1 As shown, the driving device 1 mainly includes the following components: a hydraulic motor for rotation (equivalent to the hydraulic actuator in the claims) 2, which is used to drive the rotating body 101 to rotate; a hydraulic pump (equivalent to the pump in the claims) 3, which is used to drive the hydraulic motor 2; an operating unit 4, which is used to operate the hydraulic motor 2; and a control device 5 and a control unit 6, which control the driving of the hydraulic motor 2 based on the output signal of the operating unit 4. The rotating body 101 is connected to the output shaft 2a of the hydraulic motor 2.

[0040] In order to drive the hydraulic motor 2 , the hydraulic pump 3 supplies pressurized oil to the hydraulic motor 2 .

[0041] As the hydraulic pump 3, for example, a swash plate type variable capacity type hydraulic pump is used. The swash plate type variable capacity type hydraulic pump has a piston (not shown) inside that reciprocates in conjunction with the rotation of the swash plate and the pump shaft. In addition, the stroke of the piston can be changed by using the inclination angle of the swash plate, thereby adjusting the ejection flow rate of the pressure oil. In addition, the hydraulic pump 3 is not limited to the swash plate type variable capacity type hydraulic pump. For example, a bent shaft type capacity type hydraulic pump may also be used.

[0042] The operating unit 4 includes, for example, an operating lever (not shown), and outputs a pilot pressure P1 and an operating signal S1 as signals by tilting the operating lever. The operating signal S1 is input to the control unit 6.

[0043] The first center passage L1 is connected to the discharge port of the hydraulic pump 3. The first center passage L1 connects the hydraulic pump 3 and the tank 7. The control device 5 is connected to a portion of the first center passage L1 between the hydraulic pump 3 and the tank 7.

[0044] The control device 5 includes: a second central passage L2 connected to the first central passage L1; a control valve 9 and a pressure compensation control unit 10 connected to the second central passage L2; and a switching unit 8 provided in the operation unit 4 for driving and controlling the pressure compensation control unit 10. A switching signal S2 of the switching unit 8 is output to the control unit 6.

[0045] The control valve 9 is a so-called three-position four-way directional control valve. The pilot pressure P1 output from the operation unit 4 is input to the control valve 9. As a result, the control valve 9 is driven.

[0046] The control valve 9 is connected to the hydraulic motor 2 via a pair of supply and exhaust passages 13 a and 13 b .

[0047] The control valve 9 controls the flow rate of oil delivered from the hydraulic pump 3 via the second center passage L2 based on the pilot pressure P1. In addition, the control valve 9 supplies oil to the hydraulic motor 2 via a pair of supply and exhaust passages 13a and 13b at a controlled flow rate. The control valve 9 controls the flow rate of oil flowing to the hydraulic motor 2, thereby performing brake control of the hydraulic motor 2.

[0048] The pressure compensation control unit 10 is disposed in the upstream passage L3 of the second center passage L2 on the upstream side (on the hydraulic pump 3 side) of the control valve 9. The pressure compensation control unit 10 includes a first switching valve 11 and a second switching valve 12 connected to the upstream passage L3.

[0049] The first switching valve 11 is provided in the middle of the bypass passage 16 which branches from the upstream passage L3 and is connected to the tank 7. The first switching valve 11 is a so-called two-position two-way directional control valve. The first switching valve 11 has the function of maintaining the hydraulic pressure of the upstream passage L3 so as to become the hydraulic pressure (driving pressure range, pressure range of the fluid that drives the driving body, pressure range defined by upper and lower limits) that causes the hydraulic actuator (driving body) to operate appropriately. In addition, the first switching valve 11 is connected to the control unit 6 via the first proportional control valve 14. The first proportional control valve 14 provides driving hydraulic pressure to the first switching valve 11 based on the output signal from the control unit 6. Thereby, the first switching valve 11 is driven.

[0050] A check valve 21 is connected to the bypass passage 16 downstream (tank 7 side) of the first switching valve 11. When the hydraulic pressure of the bypass passage 16 reaches a pressure (or higher than a predetermined hydraulic pressure) that actuates the check valve 21, the check valve 21 opens.

[0051] The second switching valve 12 is disposed at a position on the downstream side (control valve 9 side) of the branch point between the upstream passage L3 and the bypass passage 16. The second switching valve 12 is a so-called two-position two-way directional control valve. The second switching valve 12 has a function of adjusting the flow rate of oil supplied to the control valve 9. In addition, the second switching valve 12 is connected to the control unit 6 via the second proportional control valve 15. The second proportional control valve 15 provides a driving hydraulic pressure to the second switching valve 12 based on an output signal from the control unit 6. As a result, the second switching valve 12 is driven.

[0052] The control unit 6 is, for example, an ECU (Electronic Control Unit) and controls the drive device 1 comprehensively based on the operation signal S1 and the switching signal S2 output from the operation unit 4 .

[0053] In addition, the control unit 6 detects the pressure difference between the pre-throttle hydraulic pressure PG on the upstream side (hydraulic pump 3 side) of the second switching valve 12 and the post-throttle hydraulic pressure LSG on the downstream side (control valve 9 side) of the second switching valve 12 (hereinafter referred to as the pressure difference before and after the second switching valve 12). The control unit 6 controls the driving of the first switching valve 11 and the second switching valve 12 or synchronizes the control valve 9 and the second switching valve 12 based on the detection result and the switching signal S2 of the switching unit 8 so that the pressure difference before and after the second switching valve 12 is constant. In addition, the details of the operation of the control device 5 will be discussed later.

[0054] A pair of relief valves 17a, 17b and a pair of check valves 18a, 18b are connected to a pair of supply and exhaust passages 13a, 13b connecting the control valve 9 and the hydraulic motor 2. The pair of relief valves 17a, 17b function as safety valves for preventing the pressure of the hydraulic motor 2 from excessively rising, and also function to apply a braking force to the hydraulic motor 2.

[0055] The relief valves 17a and 17b include a first port 18 to which the pilot pressure P1 is input, and a second port 19 connected to the pair of supply and exhaust passages 13a and 13b to which the hydraulic pressure of each supply and exhaust passage 13a and 13b is input.

[0056] A third switching valve 20 (corresponding to the switching valve in the claims) is connected between the first port 18 and the operation unit 4 . The third switching valve 20 switches between the first port 18 and the operation unit 4 and between the first port 18 and the tank 7 based on an operation signal S1 from the operation unit 4 .

[0057] (Control device operation)

[0058] Next, the operation of the control device 5 will be described.

[0059] First, the operation of the pressure compensation control unit 10 will be described.

[0060] The pressure compensation control unit 10 switches between the driven state and the non-driven state based on the switching signal S2 output from the switching unit 8 of the operation unit 4 .

[0061] (Non-driving state)

[0062] When the switching signal S2 of the non-driven state of the pressure compensation control unit 10 is input to the control unit 6, the first switching valve 11 is kept open. And the control valve 9 is driven based on the pilot pressure P1 output from the operating unit 4. In addition, when the operation signal S1 of the operating unit 4 is input to the control unit 6, the control unit 6 drives the second switching valve 12 based on the operation signal S1. At this time, the control valve 9 and the second switching valve 12 are driven synchronously. The flow rate of the oil sent from the hydraulic pump 3 is controlled by the control valve 9 and the second switching valve 12, and flows to a pair of supply and discharge passages 13a and 13b. The remaining oil after being controlled by the control valve 9 flows back to the tank 7 via the second center passage L2. In addition, when the hydraulic pressure of the first center passage L1 and the upstream passage L3 becomes abnormally high pressure, the check valve 21 connected to the bypass passage 16 is opened to allow the oil to flow back to the tank 7. In this way, in the non-driven state of the pressure compensation control unit 10, the so-called relief regulation control (relief regulation method) is performed.

[0063] (Drive Status)

[0064] When the switching signal S2 of the driving state of the pressure compensation control unit 10 is input to the control unit 6, the control unit 6 detects the pressure difference before and after the second switching valve 12. The set pressure difference area before and after the second switching valve 12 (hereinafter referred to as the set pressure difference area) is pre-stored in the control unit 6. The control unit 6 detects the pressure difference before and after the second switching valve 12 to drive the first switching valve 11 so that the pressure difference is in the set pressure difference area. Specifically, when the pressure difference before and after the second switching valve 12 is lower than the set pressure difference area, the bypass passage 16 is closed by the first switching valve 11. When the pressure difference before and after the second switching valve 12 exceeds the set pressure difference area, the bypass passage 16 is opened by the first switching valve 11.

[0065] When the operation signal S1 of the operation unit 4 is input to the control unit 6, the control unit 6 drives the second switching valve 12 based on the operation signal S1. As a result, the flow rate of oil supplied to the control valve 9 is controlled. The flow rate of oil supplied to the control valve 9 via the second switching valve 12 is controlled by the control valve 9 and flows to a pair of supply and exhaust passages 13a and 13b. In this way, in the driving state of the pressure compensation control unit 10, the hydraulic pressure of the second center passage L2 is maintained in a manner that becomes a hydraulic pressure (driving pressure range) that causes the hydraulic actuator to operate appropriately, and the so-called pressure compensation control (pressure compensation control method) is performed.

[0066] Here, in the two controls of the relief adjustment control and the pressure compensation control, it can be said that the control valve 9 controls the drive of the hydraulic motor 2 by controlling the flow rate of oil sent from the hydraulic pump 3 , and then controls the braking of the hydraulic motor 2 .

[0067] (Operation of the relief valve)

[0068] Next, the operation of the pair of relief valves 17a and 17b connected to the pair of supply and discharge passages 13a and 13b will be described. In addition, in order to simplify the description, the following case will be described: by tilting the operating lever (not shown) of the operating unit 4 in one direction, the supply and discharge passage 13a of the pair of supply and discharge passages 13a and 13b becomes the passage on the side of supplying oil to the hydraulic motor 2 (hereinafter referred to as the supply passage 13a), and the supply and discharge passage 13b becomes the passage for returning oil from the hydraulic motor 2 (hereinafter referred to as the discharge passage 13b).

[0069] By operating the operating unit 4 as described above, the third switching valve 20 is switched so that the first port 18 of the relief valve 17a on the supply passage 13a side is connected to the operating unit 4. As a result, the pilot pressure P1 is applied to the relief valve 17a on the supply passage 13a side, and the relief valve 17a on the supply passage 13a side is closed due to the pressure difference between the pilot pressure P1 and the hydraulic pressure of the supply passage 13a. As the relief valve 17a is closed, the hydraulic pressure of the supply passage 13a is increased.

[0070] Meanwhile, the pilot pressure P1 applied to the relief valve 17b on the discharge passage 13b side decreases. Therefore, the relief valve 17b opens due to the pressure difference between the pilot pressure P1 and the discharge passage 13b, and the oil in the discharge passage 13b flows back to the tank 7.

[0071] In this way, the pressure difference between each supply and discharge passage 13a, 13b and the pilot pressure P1 is used as a signal, and based on the signal, the supply passage 13a becomes high pressure and the discharge passage 13b becomes low pressure. Therefore, by a single operation of the operating unit 4, the hydraulic motor 2 continues to rotate in the desired direction. In other words, the hydraulic motor 2 automatically operates.

[0072] When the hydraulic motor 2 is stopped, the operating lever (not shown) of the operating unit 4 is tilted in the direction opposite to the one direction. Then, the third switching valve 20 is switched so that the first port 18 of the relief valve 17b on the discharge passage 13b side is connected to the operating unit 4. As a result, the pilot pressure P1 applied to the relief valve 17a on the supply passage 13a side decreases. Therefore, the relief valve 17a is opened due to the pressure difference between the pilot pressure P1 and the supply passage 13a, and the oil in the supply passage 13a flows back to the tank 7.

[0073] On the other hand, the pilot pressure P1 is applied to the relief valve 17b on the discharge passage 13b side, and the relief valve 17b on the discharge passage 13b side is closed due to the pressure difference between the pilot pressure P1 and the hydraulic pressure of the discharge passage 13b. Since the relief valve 17b is closed, the hydraulic pressure of the discharge passage 13b is increased. In this way, the pressure difference between each supply and discharge passage 13a, 13b and the pilot pressure P1 is used as a signal, and based on the signal, the discharge passage 13b becomes high pressure, and the supply passage 13a becomes low pressure. Therefore, the braking force acts on the hydraulic motor 2.

[0074] Furthermore, it is desirable to control the second switching valve 12 to be closed when a braking force is applied to the hydraulic motor 2, that is, when the operating lever (not shown) is tilted in the opposite direction. This control can prevent the oil from flowing out to the second center passage L2 in vain.

[0075] In this way, the control device 5 is provided with relief valves 17a and 17b in the middle of a pair of supply and exhaust passages 13a and 13b between the control valve 9 and the hydraulic motor 2. The relief valves 17a and 17b reduce the hydraulic pressure of one of the pair of supply and exhaust passages 13a and 13b based on the pilot pressure P1 (external signal) output from the operating unit 4, the operation signal S1 (external signal), and the hydraulic pressure of the supply and exhaust passages 13a and 13b (external signal). In contrast, the hydraulic pressure of the other of the pair of supply and exhaust passages 13a and 13b is increased.

[0076] Therefore, an extra load is not applied to the hydraulic motor 2, and the hydraulic motor 2 can be automatically operated. Therefore, the operability of the hydraulic motor 2 is not impaired.

[0077] Furthermore, when the opening and closing of the relief valves 17 a and 17 b are reversed based on the operation of the operation unit 4 , the hydraulic pressure of one of the supply and discharge passages 13 a and 13 b is increased, and a stable braking force can be obtained.

[0078] In addition, the relief valves 17a and 17b are provided with a first port 18 for inputting the pilot pressure P1 and a second port 19 for inputting the hydraulic pressure of each supply and discharge passage 13a and 13b. Therefore, the pressure difference between the hydraulic pressure of each supply and discharge passage 13a and 13b and the pilot pressure P1 can be used as a signal, and the relief valves 17a and 17b can be opened and closed based on the signal. That is, when the hydraulic pressure of the supply and discharge passage 13a and 13b is higher than the pilot pressure P1, the corresponding relief valves 17a and 17b are opened. On the other hand, when the pilot pressure P1 is higher than the hydraulic pressure of the supply and discharge passage 13a and 13b, the corresponding relief valves 17a and 17b are closed. By opening and closing such relief valves 17a and 17b, the braking force applied to the hydraulic motor 2 can be released, or the braking force can be applied to the hydraulic motor 2. Therefore, the control device 5 can be set to a simple structure and a stable braking force can be obtained.

[0079] In addition, a third switching valve 20 is connected between the first port 18 and the operating unit 4. The third switching valve 20 switches the connection between the first port 18 and the operating unit 4 and the connection between the first port 18 and the tank 7 based on the operation signal S1 of the operating unit 4. Therefore, the braking force can be reliably obtained based on the pressure difference between the hydraulic pressure of the supply and exhaust passages 13a, 13b and the pilot pressure P1 without impairing the operability of the hydraulic motor 2.

[0080] (Second embodiment)

[0081] Next, based on Figure 2 A second embodiment of the present invention will be described.

[0082] Figure 2 2 is a schematic diagram of a construction machine 200 according to the second embodiment. Figure 2 In the present invention, the same schemes as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

[0083] like Figure 2 As shown, the drive device 201 used in the construction machine 200 is different from the first embodiment described above in the following points: That is, the control device 205 of the drive device 201 drives the relief valves 17a and 17b according to the driving condition of the hydraulic motor 2.

[0084] More specifically, one of the relief valves 17a and 17b is connected to the control unit 6 via the third proportional control valve 33 (equivalent to the other control valves in the claims). The third proportional control valve 33 provides a driving hydraulic pressure to the one relief valve 17a based on an output signal from the control unit 6. In addition, the other relief valve 17b of the pair of relief valves 17a and 17b is connected to the control unit 6 via the fourth proportional control valve 34 (equivalent to the other control valves in the claims). The fourth proportional control valve 34 provides a driving hydraulic pressure to the other relief valve 17b based on an output signal from the control unit 6. In this way, the pair of relief valves 17a and 17b are driven by the third proportional control valve 33 and the fourth proportional control valve 34 in addition to being driven by the third switching valve 20.

[0085] In addition, the control device 205 is provided with a sensor 40 for detecting the rotation speed, rotation angle, etc. of the output shaft 2a of the hydraulic motor 2. The detection result of the sensor 40 is output as a signal to the control unit 6. The control unit 6 drives the relief valves 17a and 17b based on the output signal from the sensor 40. That is, the control unit 6 drives the relief valves 17a and 17b so that the braking force acts on the hydraulic motor 2 when, for example, the rotation speed of the output shaft 2a is greater than a predetermined rotation speed (for example, a rated rotation speed) or the rotation angle of the output shaft 2a (the braking range of the rotary body 101) is greater than a predetermined angle (for example, an allowable angle, an allowable braking range).

[0086] The control valve 9 is connected to the control unit 6 via the fifth proportional control valve 35 and the sixth proportional control valve 36. The fifth proportional control valve 35 and the sixth proportional control valve 36 supply driving hydraulic pressure to the control valve 9 based on output signals from the control unit 6. As a result, the control valve 9 is driven.

[0087] In this way, the control device 205 includes the third proportional control valve 33 and the fourth proportional control valve 34 that drive the relief valves 17a and 17b based on the output signal (external signal) from the control unit 6. Therefore, it is possible to generate a braking force on the hydraulic motor 2 according to the driving condition of the hydraulic motor 2. Therefore, according to this second embodiment, in addition to the same effects as the first embodiment described above, the convenience of the control device 205 can be improved, and the safety of the control device 205 can also be improved.

[0088] In addition, the present invention is not limited to the above-described embodiment, and includes embodiments in which various modifications are added to the above-described embodiment within a scope that does not depart from the gist of the present invention.

[0089] For example, in the above-mentioned embodiments, the construction machines 100 and 200 are described as hydraulic excavators. However, the present invention is not limited thereto, and the above-mentioned drive devices 1 and 201 (control devices 5 and 205) can be applied to various construction machines.

[0090] In the above embodiment, the control device 5 is applied to a hydraulic circuit that drives the hydraulic motor 2 using oil delivered from the hydraulic pump 3. However, the present invention is not limited thereto, and the configuration of the control device 5 can be applied to various circuits of fluids other than oil.

[0091] In the above-mentioned embodiment, the hydraulic motor 2 is used as the driving body driven by oil. However, the present invention is not limited to this, and various actuators such as a hydraulic cylinder can be used as the driving body.

[0092] In addition, in the above-mentioned second embodiment, the case where the sensor 40 detects the rotation speed, rotation angle, etc. of the output shaft 2a of the hydraulic motor 2 is described. However, this is not limited to this, and a desired sensor can be used. For example, the temperature of the hydraulic motor 2 can also be detected by the sensor 40. In addition, a monitor can also be provided as the sensor 40 on the boom of the construction machine 200 to detect the approach to a building, etc. Furthermore, it is also possible that a braking force is applied to the hydraulic motor 2 when the temperature of the hydraulic motor 2 rises to a predetermined temperature (for example, a rated temperature) or above, or when a building, etc., is abnormally close to the boom.

[0093] In the second embodiment described above, the third proportional control valve 33 and the fourth proportional control valve 34 are used as control valves for driving the relief valves 17a and 17b based on the output signal of the control unit 6. However, the present invention is not limited thereto, and various control valves may be used instead of the third proportional control valve 33 and the fourth proportional control valve 34.

Claims

1. A control device, wherein: The control device has: a control valve for controlling the flow rate from a pump that delivers a fluid to control the driving of a driving body driven by the fluid; an upstream passage located upstream of the control valve in the central passage connected to the pump; a pair of relief valves disposed in a pair of supply and exhaust passages between the driving body and the control valve, and configured to reduce the pressure of the fluid in any one of the pair of supply and exhaust passages based on an external signal; as well as The operating unit outputs the pilot pressure that drives the control valve. The pair of relief valves each comprises: a first port for inputting the pilot pressure; and a second port for inputting the pressure of the fluid in the supply and exhaust passage, The control device comprises: a first switching valve connected to the upstream passage and used to maintain the hydraulic pressure of the upstream passage; a second switching valve connected to the upstream passage and configured to adjust a flow rate of the fluid supplied to the control valve; as well as a third switching valve provided between the operating portion and the first port, The third switching valve can switch between a connection between the first port and the operation portion and a connection between the first port and a tank from which the fluid is discharged.

2. The control device according to claim 1, wherein: The control device includes another control valve capable of driving the pair of relief valves according to a driving state of the driving body.

3. A construction machine, wherein: The construction machine comprises the control device according to claim 1 or 2, The pump is a hydraulic pump, The driving body is a hydraulic actuator.

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