Fluid pressure circuit of the working machine

Abstract

Problem: A hydraulic circuit for a machine needs to be developed that reliably and smoothly increases the operating speed of the attachment when operating independently. Solution: The control unit (27) feeds back the pressure from the other pump (25) to control the opening degree of the bypass control valve (37) of one pump (25) so that the pressure of this pump (25) is brought close to the pressure of the other pump (25), and then causes the hydraulic oil from the other pump (25) to flow together with the hydraulic oil from the first pump (25) via the straight-ahead valve (28).

Description

Technical field

[0001] The present invention relates to a fluid pressure circuit of a working machine, which conveys working fluid from a pump to a plurality of fluid pressure actuators. State of the art

[0002] In construction machinery such as hydraulic excavators equipped with a dual-pump system, it is common to control the opening and closing of the bucket using only the hydraulic oil of one pump.

[0003] On the other hand, with working machines there is a need to increase the opening and closing speed, especially when the bucket is operated alone.

[0004] In this respect, it is conceivable to supply two pumps with hydraulic oil to the bucket cylinder, however, the use of two control valves for the bucket or a flow control valve increases the space requirement and the cost.

[0005] Therefore, it is known to combine two hydraulic oil pumps and to increase the operating speed of a hydraulic actuator, such as a bucket cylinder, by means of a mixing valve provided in a hydraulic circuit, such as a forward travel valve used in a straight-ahead travel function which integrates left and right travel in one pump to prevent deviation from the direction of travel during simultaneous operation with other hydraulic drives (see, for example, patent documents 1 to 4). State-of-the-art documents, patent documents Patent Document 1: JP 1999-6174 A Patent Document 2: JP 2000-45340 A Patent Document 3: JP 2004-100847 A Patent Document 4: JP 2011-247365 A Summary of the invention Problems to be solved by the invention

[0006] Particularly in the case of paddle cylinders, the pressure of the pump that delivers the hydraulic oil to the paddle cylinder fluctuates significantly depending on the presence or absence of soil. For example, if hydraulic oil from other pumps at relatively low pressure is combined in a high-pressure state, the pump pressure can be reduced, potentially resulting in inadequate acceleration.

[0007] Against this background, an objective of the present invention is to provide a fluid pressure circuit for a working machine which can reliably and smoothly increase the operating speed of an attachment when it is operated alone. Means to solve the problem

[0008] The invention according to claim 1 is a fluid pressure circuit of a working machine comprising several pumps, several control valves that control the working fluid supplied by the pumps to several fluid pressure actuators, a straight-ahead valve, a bypass control valve that diverts the working fluid delivered by the pump to a tank, and a control unit which, when an attachment is operated alone, actuates the through-flow valve and the bypass control valve to cause the working fluid from one pump to mix with the working fluid from the other pump, and introduces the working fluid into the attachment control valve according to a required flow rate of the working fluid to the fluid pressure actuator for the attachment, wherein the control unit feeds back the pressure of one pump to control the opening degree of the bypass control valve of the other pump in order to bring the pressure of the other pump closer to the pressure of the one pump.and then combines the working fluid from one pump with the working fluid from the other pump via the through-valve. A fluid pressure circuit of a working machine that combines working fluid from other pumps with working fluid.

[0009] The invention according to claim 2 is a fluid pressure circuit of a working machine configured with a notch area that suppresses a change in the opening area relative to a stroke in an opening characteristic.

[0010] The invention according to claim 3 is a fluid pressure circuit of a working machine, wherein the fluid pressure actuator for attachment in the fluid pressure circuit of the working machine according to claim 1 or 2 is a vane cylinder. Effect of the invention

[0011] According to the invention according to claim 1, when the fluid pressure actuator for the attachment is operated alone, the working fluid from the several pumps is combined and supplied with a small pulse using the straight-ahead valve for straight-ahead travel, and the operating speed of the attachment can be increased reliably and smoothly.

[0012] According to the invention according to claim 2, the flow rate of the combined working fluid in the notch area can be varied smoothly, and a shock can be suppressed more reliably if the combined working fluid is interposed via the straight-ahead valve.

[0013] According to the invention according to claim 3, it is possible to increase the speed appropriately according to the load pressure of a pump, which varies according to the load of the blade. Brief description of the drawings Fig. Figure 1 is a circuit diagram illustrating a first embodiment of a fluid pressure circuit of a working machine according to the present invention, wherein (a) shows a state in which simultaneous operation and an even motion function are switched off, (b) shows a state in which simultaneous operation and an even motion function are switched on, and (c) shows a state in which an attachment operates alone. Fig. Figure 2 is a flowchart illustrating the control of a usage decision of a straight-ahead valve when an attachment is operated solely by a control unit in the fluid pressure circuit mentioned above. Fig. Figure 3 is a diagram illustrating an example of the relationship between the operating dimension of an actuating device for an attachment of the above-mentioned fluid pressure circuit, the flow rate requested by the pump, and the stroke between the attachment control valve and the straight-ahead valve. Fig. Figure 4 is a diagram illustrating an example of an opening characteristic of the notch control of a straight-ahead valve of the above-mentioned fluid pressure circuit. Fig. Figure 5 is a side view illustrating an example of a working machine that includes the fluid pressure circuit mentioned above. Fig. Figure 6 is a circuit diagram illustrating a second embodiment of a fluid pressure circuit of a working machine according to the present invention, wherein (a) shows a state in which a simultaneous operation and a straight-ahead driving function are switched off, (b) shows a state in which a simultaneous operation and a straight-ahead driving function are switched on, and (c) shows a state in which an attachment operates alone. Embodiments for implementing the invention

[0014] The present invention will now be described with reference to a first embodiment, which is described in the Fig. 1 to 5, and a second embodiment, which is shown in Fig. Figure 6 is shown and described in detail.

[0015] First, the first embodiment, which is described in the Fig. Numbers 1 to 5 are shown.

[0016] In Fig. Figure 5 represents a working machine. In the illustrated example, the working machine 1 is a hydraulic excavator, specifically a swiveling working machine. The working machine 1 is equipped with a lower carriage 2 and an upper swivel body 3, which is rotatably mounted within the lower carriage 2.

[0017] The lower chassis 2 comprises a left and a right pair of crawler tracks 5. Each crawler track 5 is equipped with a sprocket 7, a drive wheel (idler wheel) 8, and several road wheels 9, each rotatable at the front and rear of a long frame 6, and an endless track 10 is wrapped around them. The sprocket 7 is rotatably driven by a drive motor 11, which is a fluid pressure motor acting as a fluid pressure actuator, thus rotating the track 10.

[0018] The upper rotating body 3 is rotatably mounted relative to the frame 6 of the lower carriage 2 by a pivot bearing 13. The upper rotating body is rotated about the pivot bearing 13 relative to the lower carriage 2 by a pivot motor 14, which is a fluid pressure motor acting as a fluid pressure actuator.

[0019] A device 17 is axially coupled to the upper pivoting body 3 on one side of a cabin 16, which is a driver's cabin in which a driver sits. Furthermore, the upper pivoting body 3 is provided with an engine compartment 18, in which a motor, a pump, a control valve, etc., are housed. Various tanks, such as a hydraulic oil tank and a fuel tank, are provided on one side opposite the cabin 16 and the working device 17. A counterweight 19 is attached at one end opposite the working device 17 with respect to the engine compartment 18 and the various tanks.

[0020] The working device 17 comprises several connecting elements 28, and these connecting elements 28 are actuated according to the telescoping of the hydraulic cylinder 22, which is a fluid pressure cylinder acting as a fluid pressure actuator. In the present embodiment, the working device 17 comprises a boom 21a as a connecting element, a rod (arm) 21b as a connecting element, and a bucket 21c, which is an attachment as a connecting element. A base end of the boom 21a is axially connected to the upper pivoting body 3, a base end of the rod 21b is axially connected to a distal end of the boom 21a, and the bucket 21c is axially connected to a distal end of the rod 21b.The boom 21a, stick 21b, and bucket 21c are each pivoted by a boom cylinder 22a (a hydraulic cylinder), a stick cylinder (arm cylinder) 22b (a hydraulic cylinder), and a bucket cylinder 22c (a hydraulic cylinder), respectively. The boom 21a is vertically rotatable relative to a motor body, i.e., the upper pivot body 3, by telescoping the boom cylinder 22a; the arm 21b is lateral-rotatable relative to the boom 21a by extending the stick cylinder 22b; and the bucket 21c is lateral-rotatable relative to the bucket 21c by extending the bucket cylinder 22c.It should be noted that the configuration of the working device 17 is not limited to this configuration and may be configured to include four or more connecting elements 21, or to be provided with a suitable fastening instead of the shovel 21c.

[0021] The working machine 1 is equipped with a hydraulic circuit, which is one integrated into the Fig. The hydraulic circuit is shown in Figures 1(a) to 1(c). The hydraulic circuit comprises several pumps (main pumps) 25, several control valves 26 for controlling the hydraulic fluid, which is directed as working fluid from the pumps 25 to several fluid pressure actuators, and a control unit 27 for controlling the operation of the control valves 26.

[0022] The number of pumps 25 can be three or more; however, in the present embodiment, for example, a pair consisting of a first pump 25a and a second pump 25b is provided. The pump 25 is connected to the output shaft of the motor and is driven by the motor. For example, a variable volume pump is used as pump 25.

[0023] The control valve 26 is a spool valve arranged as a control valve within a block. The hydraulic oil delivered from the pump 25 is supplied to the control valves 26, and the hydraulic oil flow is controlled according to the direction and amount of displacement of these control valves 26 to supply the respective fluid pressure actuators. Each control valve 26 is controlled according to the amount of actuation by the actuator, such as a lever or pedal. A signal corresponding to the amount of actuation by the actuator is applied to an input side of the control unit 27, and the flow rate of the hydraulic oil through the pump 25 is controlled according to the current value of a flow command signal issued by the control unit 10 based on the input signal.In other words, pump 25 is a current-controlled pump that can be adjusted according to the load from the minimum flow rate at no load by controlling the capacity variables, such as a swashplate, by means of a controller that is actuated by a solenoid valve (electromagnetic proportional valve) which receives a command signal from the control unit 10.

[0024] In the present embodiment, the control valve 26 is provided with a control valve group corresponding to each of the pumps 25. That is, a control valve group is configured for each pump 25. In the illustrated example, a first control valve group BGa is provided, which primarily supplies hydraulic oil delivered by the first pump 25a to the fluid pressure actuator, and a second control valve group BGb, which primarily supplies hydraulic oil delivered by the second pump 25b to the fluid pressure actuator.

[0025] One of the first control valve groups BGa and the second control valve group BGb comprise at least one drive control valve 26, which controls the flow rate and direction of a drive motor 11 ( Fig. 5) supplied hydraulic oil, and the other comprises at least one drive control valve 26, which controls the flow rate and direction of the hydraulic oil supplied to the other drive motor 11 ( Fig. 5) controls the supplied hydraulic oil.

[0026] For example, the first control valve group BGa of the present embodiment comprises at least one drive control valve 26trR for controlling the flow rate and direction of the right drive motor 11 ( Fig. 5) supplied hydraulic oil, a boom control valve 26bm for controlling the flow rate and direction of the hydraulic oil supplied to the boom cylinder 22a ( Fig. 5) supplied hydraulic oil and an attachment control valve (bucket) 26at for controlling the flow rate and direction of the hydraulic oil supplied to the bucket cylinder 22c ( Fig. 5) is supplied, which is a fluid pressure actuator for the attachment.

[0027] The second control valve group BGb includes, for example, at least one drive control valve 26trL ​​for controlling the flow rate and direction of the flow to the left drive motor 11 ( Fig. 5) supplied hydraulic oil, a stick control valve 26st for controlling the flow rate and direction of the hydraulic oil supplied to the stick cylinder 22b ( Fig. 5) and a swivel control valve 26sw for controlling the flow rate and direction of the rotary motor 14 ( Fig. 5) supplied hydraulic oil includes.

[0028] The supply channel for hydraulic oil from each control valve 26 to each fluid pressure actuator and the return channel that returns the supplied hydraulic oil to the tank are not shown in the figure.

[0029] Furthermore, the control valves 26, with the exception of the driving control valves 26trL ​​and 26trR, are shown together for each control valve group BGa and BGb.

[0030] Furthermore, for the control valve 26, which may include a device for controlling the flow rate and direction of the hydraulic oil supplied to another operating part, it is optional whether the control valve 26 is included in the first control valve group BGa or the second control valve group BGb, and its illustration is omitted in the present embodiment for the sake of clarity.

[0031] Subsequently, a straight-ahead valve 28 is provided between these two control valve groups BGa and BGb. The straight-ahead valve 28 enables the machine 1 to travel straight ahead ( Fig. 5) by ensuring an even supply to the control valve 26 for the left and right drive motors 11 ( Fig. 5) with hydraulic oil. The straight-ahead valve 28 is set to a first position X, which is an off position of the straight-ahead function, and a second position Y, which is an on position of the straight-ahead function. The straight-ahead function is switched on and off by the operator, for example, using an adjustment device such as a switch. In the present embodiment, a proportional control valve is used in the straight-ahead valve 28. That is, the straight-ahead valve 28 is configured to continuously vary an opening amount (of the stroke) between the first position X and the second position Y.

[0032] In the present embodiment, a notched region is formed in the coil of the straight-ahead valve 28 on both the outlet and inlet sides. The notched region defines a notch area that suppresses a change in the opening area relative to the stroke (coil movement amount) in the opening characteristics of the straight-ahead valve 28 and cushions a shock during sudden actuation of the straight-ahead valve 28 when opening and closing by rectifying the hydraulic oil, for example, by consisting of a plurality of notches formed along the coil movement direction on the outer circumference of the coil's land area. An example of the opening characteristics of the straight-ahead valve 28 of the present embodiment is shown in Fig. Figure 4 illustrates this. In contrast to conventional straight-through valves, which had only a minimal notch area to simplify machining and dampen shocks during switching, in the illustrated example, the notch area AN is enlarged to its opening amount with a controlled opening amount (an opening amount that changes continuously and corresponds to a pressure drop acceptable for a hydraulic system). This allows the pump flow rate into the fluid pressure actuator for mounting to be controlled, compared to the conventional example represented by the double-dotted catenary. The notch area AN encompasses at least a mid-section of the total stroke and is set over a range where the opening area is zero. Furthermore, in the notch area AN, the opening characteristic of the straight-through valve 28 is aligned towards the opening area zero, and the change in the opening area relative to the stroke is suppressed.Therefore, the opening characteristics of the straight-ahead valve 28 of the present embodiment are set such that the rate of change of the opening area relative to the stroke amount changes at two points: at the position where the general area and the notch area AN are connected to each other, and at the position near the notch area AN where the opening area is 0.

[0033] Then, as in the Fig. As shown in Figures 1(a) to 1(c), one of the pump channels 30a, 31a of the first pump 25a, for example pump channel 30a, is connected to the travel control valve 26trR, and the other, for example pump channel 31a, is connected to the straight-ahead travel valve 28. Furthermore, one of the pump channels 30b, 31b of the second pump 25b, for example pump channel 30b, is connected to the boom control valve 26st or the slew control valve 26sw, while the other, for example pump channel 31b, is connected to the straight-ahead travel valve 28. In addition, the pump 25 is equipped with a bypass control valve 37. The bypass control valve 37 allows the hydraulic oil discharged from the pump 25 to be diverted to the tank 38. The system pressure of pump 25 is regulated by the pump's delivery rate and the opening degree of the bypass control valve 37.In the present embodiment, the first bypass control valve 37a and the second bypass control valve 37b are arranged corresponding to the first pump 25a and the second pump 25b. The bypass control valves 37a and 37b are connected to the pump channels 30a and 30b via the bypass channels 36a and 36b. The boom control valve 26bm, the attachment control valve 26at, and the travel control valve 26trL ​​are connected to parallel supply channels 32 and 33 to supply hydraulic oil to the straight-ahead travel valve 28. A parallel supply channel 32 and a travel control valve 26trR are connected via a channel 35 for the supply of hydraulic oil, which includes a check valve 34.

[0034] The operation of the straight-ahead valve 28 is controlled by the control unit 27 together with the operation of the control valve 26 and the bypass control valve 37. The control unit 27 is, for example, an onboard control unit mounted on a cabin 16 ( Fig. 5).

[0035] The control unit 27 generates and outputs a command signal to control the straight-ahead valve 28, to move the straight-ahead valve 28 to the first position X when the straight-ahead function is switched off, and to move the straight-ahead valve 28 to the second position Y when the straight-ahead function is switched on, when the operator operates the multiple fluid pressure actuators.

[0036] When the straight-ahead driving function is switched off, the straight-ahead driving valve 28, which is in the first position X due to a command signal from the control unit 27, connects the pump channel 31a to the parallel supply channel 32 and the pump channel 31b to the parallel supply channel 33, as shown in Fig. As shown. In this state, the hydraulic oil delivered by the first pump 25a is directed to the travel control valve 26trR, the boom control valve 26bm, the attachment control valve 26at, etc., while the hydraulic oil delivered by the second pump 25b is directed to the travel control valve 26trL, the stick control valve 26st, the swing control valve 26sw, etc., and a signal generated by the operator according to the actuation dimension and direction of the actuating device is input to the control unit 27, and the control unit 27 generates and outputs a command signal based on this signal, so that each control valve 26 operates independently and the hydraulic oil is supplied to each fluid pressure actuator. Accordingly, the direction of rotation and speed of each in Fig. The direction of rotation and speed of the slewing motor 14 shown in Figure 5, the extension and speed of the boom cylinder 22a, the extension and speed of the stick cylinder 22b, the extension and speed of the bucket cylinder 22c and the extension and speed of the bucket cylinder 22c are each controlled independently of each other, and the travel of the lower carriage 2, the slewing of the upper slewing carriage 3 and the operation of the working device 17 are carried out according to the actuation of the actuating device by the operator.

[0037] When the straight-ahead driving function is activated, as in Fig. As shown in Figure 1(b), the control unit 27 generates and outputs a command signal to control the straight-ahead valve 28, switching the straight-ahead valve 28 to the second position Y. In the second position Y, the straight-ahead valve 28 connects pump channel 31a to the parallel supply channel 33 and connects pump channel 31b to the parallel supply channel 32. In this state, the hydraulic oil delivered by the first pump 25a is directed to the travel control valves 26trR and 26trL, and the hydraulic oil delivered by the second pump 25b is directed to the boom control valve 26bm, the attachment control valve 26at, the stick control valve 26st, the swing control valve 26sw, etc.A signal, generated by the operator according to the actuation magnitude and direction of the actuating device, is fed into the control unit 27, and the control unit 27 generates and outputs a command signal based on this signal, so that each control valve 26 operates independently and the hydraulic oil is supplied to each fluid pressure actuator. By rotating each in... Fig. The drive motor 11 shown in Figure 5, to which the same quantity of hydraulic oil is supplied by the common first pump 25a in the same direction and at the same speed, drives the working machine 1 straight ahead, and at the same time the direction of rotation and rotational speed of the slewing motor 14, the extension and retraction and speed of the boom cylinder 22a, the telescoping and speed of the stick cylinder 22b and the telescoping and speed of the bucket cylinder 22c are controlled independently of each other, and the rotation of the upper slewing body 3 and the operation of the working device 17 are carried out according to the actuation of the actuating device by the operator.

[0038] Furthermore, the control unit 27 generates and outputs, as shown in Fig. 1 (c) shows a command signal for actuating the straight-ahead valve 28 according to the required flow rate of the hydraulic oil, i.e. depending on the actuation quantity of the actuating device, such as a lever or a pedal for actuating the attachment, when the operator alone operates the attachment, in this embodiment the bucket 21c ( Fig. 5), activated.

[0039] That is, as in Fig. As shown in Figure 2, the control unit 27 determines whether the actuation of the actuator for an operation of the attachment has been initiated (step S1), and if it determines that the actuation of the actuator for the operation of the attachment has been initiated (in the case of YES in step S1), it determines whether the actuation of the actuator for an operation other than that of the attachment has been initiated (step S2), and if it determines that no actuation of the actuator for the operation other than the attachment has been initiated (in the case of NO in step S2), it determines whether the requested flow rate is greater than or equal to a predetermined flow rate that is less than the maximum delivery rate of a pump 25 (in the present embodiment, the first pump 25a) (step S3), and if it determines that the requested flow rate is greater than the predetermined flow rate,The straight-ahead valve 28 is actuated to compensate for the difference between the requested flow rate and the delivery rate of one pump 25 from the other pump 25 (in this embodiment, the second pump 25b). In case of other findings, the process returns to step S1.

[0040] Fig. Figure 3 shows an example of the relationship between the actuation amount of the actuating device for the attachment, the requested flow rates Qa, Qb of the pumps 25a, 25b ( Fig. 1 (c)) and the strokes St1, St2 of the implement control valve 26at ( Fig. 5) and the straight-ahead valve 28. In the example shown, the opening quantity of the driving control valve 28 ( Fig. 1 (c)) controlled so that, according to the amount of actuation required for a required flow rate exceeding a predetermined flow rate Q, it gradually increases to a maximum stroke St according to the amount of actuation of the actuating device.

[0041] In the present embodiment, as in Fig. As shown in 1 (c), the drive control valve 26trR is operated by a single actuation of the fluid pressure actuator for the attachment (bucket cylinder 22c ( Fig. 5)) is brought into a neutral position so that the hydraulic oil from the first pump 25a is directed via the passage 35 and the parallel supply channel 32 from the control valve 26trR to the attachment control valve 26at, depending on the actuation amount of the operating device for the operation of the attachment. If the actuation amount of the operating device for the operation of the attachment is greater than the predetermined actuation amount, the straight-ahead valve 28 is actuated and the hydraulic oil from the second pump 25b is combined according to the opening amount and introduced into the attachment control valve 26at. Accordingly, the operation of the attachment, the opening and closing process of the bucket 21c ( Fig. 5) accelerated in the present embodiment.

[0042] At this point, when the control unit 27 switches from controlling the simultaneous operation of the multiple fluid pressure actuators to controlling the individual operation of the fluid pressure actuator for the attachment (bucket cylinder 22c ( Fig. 5)) When transitioning from the control of individual operation of the fluid pressure actuator for the attachment to the control of simultaneous operation of multiple fluid pressure actuators, it is advantageous to control the speed limiter control in such a way that the transition is gradual and smooth. Likewise, when transitioning from the control of individual operation of the fluid pressure actuator for the attachment to the control of simultaneous operation of multiple fluid pressure actuators, it is preferable to implement the speed limiter control in such a way that the transition is gradual and smooth.

[0043] Especially if the attachment is a shovel 21c ( Fig. 5) In this scenario, the load pressure fluctuates significantly depending on the presence or absence of soil to be excavated, the subsoil, etc., and consequently, the pressure of the first pump 25a, which supplies the hydraulic oil to the actuator for the attachment, also fluctuates considerably. If the pump pressure of the first pump 25a is high and the pressure is passed on to the second pump 25b at a relatively low pressure, the pressurized oil of the first pump 25a is relieved via the second bypass control valve 37b on the side of the second pump 25b, or a surge occurs during the convergence.

[0044] To avoid this, when the hydraulic oil of the second pump 25b is combined via the straight-ahead valve 28, the control unit 27 generates a command signal that reports back the pressure of the first pump 25a and controls the opening degree of the second bypass control valve 37b to bring the pressure of the second pump 25b closer to the pressure of the first pump 25a, and then to bring the pressure of the second pump 25b closer to the pressure of the first pump 25a.

[0045] Accordingly, a straight-ahead valve 28 can be used for straight-ahead driving to supply the hydraulic oil from the multiple pumps 25 with fewer shocks when the fluid pressure actuator for the attachment is operated alone in a space-saving and cost-effective manner, and the operating speed of the attachment can be increased reliably and smoothly.

[0046] In particular, if the fluid pressure actuator for the attachment is the bucket cylinder 22c for the bucket 21c, an appropriate acceleration is possible according to the load pressure of the first pump 25a, which varies depending on the load of the bucket 21c.

[0047] By designing the straight-ahead valve 28 as a proportional control valve, the shock generated at the time the hydraulic oil is brought together in the actuating device, such as a lever, can be mitigated, and smooth operation can be achieved.

[0048] Furthermore, since the opening characteristic of the straight-ahead valve 28 is set with a large notch area AN, which suppresses the change in the opening area relative to the stroke, the flow rate of the hydraulic oil to be mixed can be changed smoothly, and the shock when mixing the hydraulic oil through the straight-ahead valve 28 can be suppressed more reliably.

[0049] Next, the second embodiment, which is described in Fig. 6 is shown.

[0050] In the present embodiment, one of the pump channels 30a, 31a of the first pump 25a, for example pump channel 30a, is connected to the boom control valve 26bm or the attachment control valve 26at, while the other, for example pump channel 31a, is connected to the straight-ahead travel valve 28. Furthermore, one of the pump channels 30b, 31b of the second pump 25b, for example pump channel 30b, is connected to the travel control valve 26trL, and the other, for example pump channel 31b, is connected to the straight-ahead travel valve 28. A travel control valve 26trR, a stick control valve 26st, and a slewing control valve 26sw are each connected to the straight-ahead travel valve 28 via parallel supply channels 40, 41 for hydraulic oil supply. In addition, the parallel supply channel 41 and the drive control valve 26trL ​​are connected to a channel 44 for the supply of hydraulic oil, which contains a check valve 43.

[0051] Then, as in the first embodiment, when the straight-ahead driving function is switched off, as in Fig. As shown in Figure 6(a), the straight-ahead valve 28, which is in the first position X by a command signal from the control unit 27, connects the pump channel 31a to the parallel supply channel 40 and connects the pump channel 31b to the parallel supply channel 41. In this state, the hydraulic oil delivered by the first pump 25a is directed to the travel control valve 26trR, the boom control valve 26bm, the attachment control valve 26at, etc., while the hydraulic oil delivered by the second pump 25b is directed to the travel control valve 26trL, the stick control valve 26st, the swing control valve 26sw, etc.A signal, generated by the operator according to the actuation magnitude and direction of the actuating device, is input into the control unit 27. The control unit 27 then generates and outputs a command signal based on this signal, causing each control valve 26 to operate independently and supplying hydraulic oil to each fluid pressure actuator. Accordingly, the direction and speed of rotation of each travel motor 11, the direction and speed of rotation of the slewing motor 14, the extension and speed of the boom cylinder 22a, the extension and speed of the bucket cylinder 22b, and the extension and speed of the bucket cylinder 22c are controlled independently. The travel of the lower carriage 2, the slewing of the upper slewing carriage 3, and the operation of the working device 17 are executed according to the operator's actuation of the actuating device.

[0052] Furthermore, when the straight-ahead driving function is activated, a control signal is generated and output to control the straight-ahead driving valve 28 in order to switch the straight-ahead driving valve 28 to the second position Y. As in Fig. As shown in Figure 6(b), in the second position Y, the straight-ahead valve 28 connects pump channel 31a to parallel supply channel 41 and connects pump channel 31b to parallel supply channel 40. In this state, the hydraulic oil delivered by the first pump 25a is directed to the boom control valve 26bm, the attachment control valve 26at, the stick control valve 26st, the swing control valve 26sw, etc., and the hydraulic oil delivered by the second pump 25b is directed to the travel control valves 26trR, 26trL. A signal, generated by the operator according to the actuation magnitude and direction of the actuating device, is input to the control unit 27. The control unit 27 generates and outputs a command signal based on this signal, so that each control valve 26 operates independently and hydraulic oil is supplied to each fluid pressure actuator.Accordingly, the working machine 1 moves straight ahead, with each one in . Fig. 5 The drive motor 11 shown, to which the same quantity of hydraulic oil is supplied by the common first pump 25a in the same direction and at the same speed, is rotated, wherein the direction of rotation and rotational speed of the slewing motor 14, the extension and retraction and speed of the boom cylinder 22a, the extension and retraction and speed of the stick cylinder 22b and the extension and retraction and speed of the bucket cylinder 22c are controlled independently of each other, and the pivoting of the upper slewing body 3 and the operation of the working device 17 are carried out according to the actuation of the actuating device by the operator.

[0053] Furthermore, the control unit 27 generates and outputs, as shown in Fig. 6 (c) shows a command signal that actuates the straight-ahead valve 28 when the operator operates the attachment alone, in this embodiment the bucket 21c ( Fig. 5), depending on the required flow rate of the hydraulic oil, i.e., depending on the actuation quantity of the actuating device, such as a lever or pedal for actuating the attachment.

[0054] In the present embodiment, the hydraulic oil from the first pump 25a is introduced into the attachment control valve 26at according to the actuation force of the actuating device for operating the attachment. If the actuation force of the actuating device for operating the attachment is greater than a predetermined actuation force, the straight-ahead travel valve 28 is actuated, and depending on its opening force, the hydraulic oil introduced from the second pump 25b into the travel control valve 26trL ​​is directed from the travel control valve 26trL, which is in the neutral position, via the passage 44, the parallel supply channel 41, the straight-ahead travel valve 28, and the pump channel 31a into the mounting control valve 26at and the pump channel 30a. Accordingly, the operation of the attachment, the opening and closing process of the bucket 21c ( Fig. 5) accelerated in the present embodiment.

[0055] At this point, when the hydraulic oil from the second pump 25b is combined via the forward-travel valve 28, the control unit 27 generates a command signal that reports the pressure of the first pump 25a and controls the opening degree of the second bypass control valve 37b to bring the pressure of the second pump 25b closer to the pressure of the first pump 25a, and then brings the pressure of the second pump 25b closer to the pressure of the first pump 25a. Accordingly, it is possible to achieve similar effects to the first embodiment, such that, for example, by using the forward-travel valve 28 for forward travel, the hydraulic oil from the multiple pumps 25 can be combined in a space-saving and cost-effective manner with fewer shocks when the fluid pressure actuator for the attachment is individually actuated, and the operating speed of the attachment can be reliably and smoothly ensured. Industrial applicability

[0056] The present invention is applicable, for example, to an industry that manufactures and sells work machines with hydraulic circuits. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 1999-6174 A

[0005] JP 2000-45340 A

[0005] JP 2004-100847 A

[0005] JP 2011-247365 A

[0005]

Claims

[1] Fluid pressure circuit of a working machine, comprising: a large number of pumps, a multitude of control valves that control the working fluid supplied by the pumps to a multitude of fluid pressure actuators; a straight-ahead valve; a bypass control valve that diverts the working fluid delivered by the pump into a tank; a control unit which, when an attachment is operated alone, actuates the straight-ahead valve and the bypass control valve to cause the working fluid from one pump to combine with the working fluid from the other pump, and directs the working fluid to the attachment control valve according to the required flow rate of the working fluid to the fluid pressure actuator for the attachment, wherein the control unit returns the pressure of one pump to control the opening degree of the bypass control valve of the other pump in order to bring the pressure of the other pump closer to the pressure of one pump, and then combines the working fluid from one pump with the working fluid from the other pump via the straight-ahead valve. [2] Fluid pressure circuit of the working machine according to claim 1, wherein the straight-ahead valve is configured with a notch area that suppresses a change in the opening area relative to a stroke in an opening characteristic. [3] Fluid pressure circuit of a working machine according to claim 1 or 2, wherein the fluid pressure actuator for the attachment is a bucket cylinder.

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