JP2014159851A - Hydraulic control device and construction machine equipped with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To compatibly increase the speed of a hydraulic actuator during light-load work and secure the driving force of the hydraulic actuator during heavy-load work even when the temperature of working oil is reduced.SOLUTION: A hydraulic control device includes a controller 32 for changing over a selector valve 28 into a regeneration position V when a discharge pressure P detected by a pressure detector 20 is a reference pressure or lower, and for changing over the selector valve 28 into a regeneration cut position W when the discharge pressure P is higher than the reference pressure. The controller 32 changes the reference pressure to be higher when a temperature T of working oil detected by a temperature detector 31 is on a low-temperature side with reference to a specified temperature than when it is on a high-temperature side.

Description

  The present invention relates to a hydraulic control device having a regeneration function for supplying return oil from a hydraulic actuator to a supply side of the hydraulic actuator.

  Conventionally, for example, in a hydraulic excavator, an arm is provided by supplying (regenerating) return oil from the rod side chamber of the arm cylinder to the head side chamber of the arm cylinder during a light load operation such as when performing an arm pulling operation in the air. A speeding up of the pulling operation is being performed.

  In addition, the regeneration function is also cut in order to sufficiently secure the driving force by the arm pulling operation at the time of heavy load work such as excavation work while increasing the speed at the time of light load work described above. (For example, refer to Patent Document 1).

  Specifically, the device described in Patent Document 1 includes a regenerative oil passage that connects a supply oil passage for supplying hydraulic oil to the arm cylinder and a discharge oil passage for discharging the hydraulic oil from the arm cylinder to the tank. , A regeneration valve that can be switched between a regeneration position for flowing hydraulic oil from a discharge oil passage to a supply oil passage through a regeneration oil passage and a regeneration cut position that regulates the flow, and a discharge pressure of a hydraulic pump is preset. And a controller for switching the regeneration valve to the regeneration position when the pressure is lower than the reference pressure and for switching the regeneration valve to the regeneration cut position when the discharge pressure of the hydraulic pump is higher than the reference pressure. .

  According to this configuration, the speed of the arm pulling operation can be increased by regenerating the return oil from the arm cylinder to the supply side of the arm cylinder at the time of a light load operation in which the discharge pressure of the hydraulic pump is lower than the reference pressure. . On the other hand, back pressure is generated in the discharge side oil passage of the arm cylinder by discharging the return oil from the arm cylinder to the tank without going through the regeneration oil passage during heavy load work where the discharge pressure of the hydraulic pump is higher than the reference pressure. And the driving force of the arm cylinder can be secured.

JP-A-10-267007

  Here, since the viscosity of the hydraulic oil has a characteristic that the hydraulic oil becomes higher as the temperature of the hydraulic oil becomes lower, the flow resistance of the hydraulic oil in the oil passage increases and the pressure of the hydraulic oil increases as the hydraulic oil becomes lower in temperature.

  However, in Patent Document 1, since the temperature characteristic of the hydraulic oil is not taken into consideration, the regeneration valve is in spite of the state that should be regenerated due to the increase of the hydraulic oil pressure (pump discharge pressure) accompanying the temperature drop. May switch to the playback cut position and cut playback. In this case, it is not possible to effectively increase the speed at the time of light load work, or the speed decreases during the light load work.

  Accordingly, it is conceivable to set the reference pressure in advance on the high pressure side in consideration of the temperature characteristics of the hydraulic oil. However, if this is done, the regeneration state may be maintained during heavy load work, i.e., the regeneration should be cut off. As a result, the driving force of the hydraulic actuator cannot be secured sufficiently.

  An object of the present invention is to achieve both speeding up of the hydraulic actuator during light load work and securing of driving force of the hydraulic actuator during heavy load work even when the temperature of the hydraulic oil is lowered.

  In order to solve the above problems, the present invention provides a hydraulic pump and a tank, a hydraulic actuator driven by hydraulic oil from the hydraulic pump, and a supply oil passage for supplying hydraulic oil from the hydraulic pump to the hydraulic actuator. And a supply / discharge circuit including a discharge oil path for discharging hydraulic oil from the hydraulic actuator to the tank, a regeneration oil path connecting the supply oil path and the discharge oil path, and through the regeneration oil path Regeneration switching means capable of switching between a regeneration state that allows the flow of hydraulic oil from the discharge oil passage to the supply oil passage and a regeneration cut state that restricts the flow of the hydraulic oil through the regeneration oil passage; Including a regeneration circuit, a pressure detector for detecting a discharge pressure of the hydraulic pump, a temperature detector for detecting a temperature of the hydraulic oil, and a discharge pressure detected by the pressure detector being lower than a reference pressure. A controller for switching the regeneration switching means to the regeneration state when the discharge pressure is higher than the reference pressure, and a controller for switching the regeneration switching means to the regeneration cut state. When the temperature of the hydraulic oil detected by the temperature detector is on the low temperature side with reference to a specific temperature predetermined based on the viscosity characteristics of the hydraulic oil, the reference pressure is higher than that on the high temperature side. Provided is a hydraulic control device for changing the reference pressure so that

  According to the present invention, when the temperature of the hydraulic oil is on the low temperature side with respect to the specific temperature, the reference pressure can be changed higher than when the temperature of the hydraulic oil is on the high temperature side. For this reason, even if the discharge pressure increases as the temperature (viscosity) of the hydraulic oil decreases, the regeneration switching means can be prevented from being switched to the regeneration cut state. it can.

  Therefore, even when the temperature of the hydraulic oil is lower than the specific temperature, it is possible to achieve both speeding up of the hydraulic actuator during light load work and securing of driving force of the hydraulic actuator during heavy load work.

  The “specific temperature” in the present invention is a temperature determined in advance based on the characteristic of the viscosity of the hydraulic oil with respect to the temperature of the hydraulic oil. Basically, the discharge pressure of the pump does not originally reach the reference pressure. Nevertheless, it refers to the temperature value at which the viscosity increases until it rises above the reference pressure.

  In the hydraulic control device, the reference pressure may be switched between a preset first pressure and a second pressure higher than the preset first pressure with the specific temperature as a boundary.

  According to this aspect, it is possible to simplify the process of changing the reference pressure as compared with the case where the reference pressure is set for each temperature of the hydraulic oil.

  In the hydraulic control device, as the specific temperature, a first specific temperature serving as a reference for switching from the first pressure to the second pressure, a temperature different from the first specific temperature, and the first pressure from the second pressure. It is preferable that a second specific temperature as a reference for switching to the pressure is set.

  According to this aspect, the first temperature that serves as a reference for increasing the reference pressure and the second temperature that serves as a reference for decreasing the reference pressure are set to different temperatures. Therefore, it is possible to prevent the reference pressure from frequently switching due to increase or decrease in the temperature of the hydraulic oil across the specific temperature as in the case where one temperature is set as the specific temperature.

  Further, the present invention includes a base machine, a driven member attached to the base machine so as to be displaceable, and the hydraulic control device having a hydraulic actuator for driving the driven member. Provide construction machinery.

  According to the present invention, even when the temperature of the hydraulic oil is lowered, it is possible to achieve both speeding up of the hydraulic actuator during light load work and securing of driving force of the hydraulic actuator during heavy load work.

1 is a left side view illustrating an overall configuration of a hydraulic excavator according to an embodiment of the present invention. It is a circuit diagram which shows the hydraulic control apparatus provided in the hydraulic shovel shown in FIG. It is a flowchart which shows the process performed by the controller shown in FIG.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. The following embodiments are examples embodying the present invention, and are not of a nature that limits the technical scope of the present invention.

  Referring to FIG. 1, a hydraulic excavator 1 as an example of a construction machine includes a self-propelled lower traveling body 2, an upper revolving body 3 provided so as to be pivotable with respect to the lower traveling body 2, and an upper revolving body. 3 is provided with an attachment 4 that can be raised and lowered, and a hydraulic control device 5 shown in FIG.

  The attachment 4 has a boom 6 attached to the upper swing body 3 so as to be raised and lowered, an arm (driven member) 7 attached so as to be rotatable with respect to the tip of the boom 6, and a tip of the arm 7. And a bucket 8 attached to be rotatable.

  The attachment 4 also has a boom cylinder 9 that raises and lowers the boom 6 relative to the upper swing body 3, an arm cylinder 10 that rotates the arm 7 relative to the boom 6, and a bucket 8 that rotates relative to the arm 7. A bucket cylinder 11 is provided.

  Referring to FIG. 2, the hydraulic control device 5 operates with respect to the hydraulic pump 14, the tank 15, the arm cylinder 10 as a hydraulic actuator driven by hydraulic oil from the hydraulic pump 14, and the arm cylinder 10. A supply / discharge circuit 16 for supplying and discharging oil, a regeneration circuit 17 for regenerating the return oil from the arm cylinder 10 to the supply side of the arm cylinder 10, and a remote controller as operating means for operating the arm 7 A valve 18, an operation amount detector 19 that detects the operation amount of the remote control valve 18, a pressure detector 20 that detects the discharge pressure of the hydraulic pump 14, a temperature detector 31 that detects the temperature of the hydraulic oil, and a regeneration circuit. 17 is provided.

  The supply / discharge circuit 16 connects the control valve 21 that controls supply / discharge of hydraulic oil to / from the arm cylinder 10, the pump-side oil passage 22 that connects the control valve 21 and the hydraulic pump 14, and the control valve 21 and the tank 15. The first tank side oil passage 23 and the second tank side oil passage 24, the head side oil passage 25 connecting the control valve 21 and the head side chamber of the arm cylinder 10, the control valve 21 and the rod side chamber of the arm cylinder 10 And a rod-side oil passage 26 for connecting the two.

  The control valve 21 has a neutral position X for stopping supply and discharge of hydraulic oil to and from the arm cylinder 10, an arm pulling position Y for extending the arm cylinder 10 to perform the pulling operation of the arm 7, and reducing the arm cylinder 10. Thus, it is possible to switch between the arm pushing position Z for pushing the arm 7.

  Further, the control valve 21 is normally biased to the neutral position X, and is switched to the arm pulling position Y or the arm pushing position Z according to the pilot pressure from the remote control valve 18 operated by the lever. The operation amount for arm pulling by the remote control valve 18 is detected by the operation amount detector 19 as a pilot pressure.

  At the arm pulling position Y, the pump side oil passage 22 and the head side oil passage 25 are connected to form a supply oil passage, and the first tank side oil passage 23 and the rod side oil passage 26 are connected to discharge. An oil passage is formed. On the other hand, at the arm pushing position Z, the pump-side oil passage 22 and the rod-side oil passage 26 are connected to form a supply oil passage, and the second tank-side oil passage 24 and the head-side oil passage 25 are connected. As a result, a drain oil passage is formed.

  The regeneration circuit 17 includes a switching valve 28 provided in the first tank-side oil passage 23, a regeneration oil passage 27 that connects the switching valve 28 and the control valve 21, and an operation valve (electromagnetic) for operating the switching valve 28. Proportional valve) 29.

  The switching valve 28 has a regeneration position V for regenerating the return oil from the rod side chamber of the arm cylinder 10 to the head side chamber of the arm cylinder 10 during the arm pulling operation, and from the rod side chamber of the arm cylinder 10 during the arm pulling operation. Switching between the return cut position W for discharging the return oil to the tank 15 is possible.

  At the regeneration position V and the regeneration cut position W, the regeneration oil passage 27 joins the first tank side oil passage 23. Further, at the regeneration position V, a throttle 28 a is provided on the downstream side of the junction with the regeneration oil passage 27 in the first tank side oil passage 23. On the other hand, the regenerative oil passage 27 is provided with a check valve 27a that permits the flow of hydraulic oil from the switching valve 28 toward the control valve 21 while restricting the flow in the opposite direction. Further, the regenerated oil passage 27 joins the pump side oil passage 22 in the control valve 21 through a joining oil passage 27b provided at the arm pulling position Y.

  With this configuration, when the control valve 21 is switched to the arm pulling position Y and the switching valve 28 is switched to the regeneration position V, the return oil from the rod side chamber of the arm cylinder 10 enters the regeneration oil path 27 from the front of the throttle 28a. It is led to the head side oil passage 25 through the check valve 27a and the control valve 21, that is, it is in a regeneration state.

  On the other hand, in the state where the control valve 21 is switched to the arm pulling position Y and the switching valve 28 is switched to the regeneration cut position W, the throttle 28 a is not interposed in the first tank side oil passage 23. Therefore, the return oil from the arm cylinder 10 is discharged to the tank 15 through the first tank side oil passage 23 having a lower pressure than the regeneration oil passage 27 (pump side oil passage 22) (becomes a regeneration cut state). .

  Thus, the switching valve 28 can be switched between a regeneration state in which the return oil from the rod side of the arm cylinder 10 is returned to the head side of the arm cylinder 10 through the regeneration oil passage 27 and a regeneration cut state in which regeneration is cut off. A simple reproduction switching means.

  The switching valve 28 is biased to the normal regeneration position V, while being switched to the regeneration cut position W in a state where pilot pressure is supplied via the operation valve 29.

  The operation valve 29 supplies the pilot pressure from the pilot pump 30 to the switching valve 28 in accordance with an electrical command from the controller 32.

  The controller 32 switches the switching valve 28 to the regeneration position V when the discharge pressure of the hydraulic pump 14 detected by the pressure detector 20 is equal to or lower than the reference pressure, and switches the switching valve 28 when the discharge pressure is higher than the reference pressure. A command is output to the operation valve 29 so that 28 is switched to the regeneration cut position W.

  As a result, during a light load operation where the discharge pressure of the hydraulic pump 14 is lower than the reference pressure (for example, arm pulling operation in the air), the return oil from the rod side chamber of the arm cylinder 10 is regenerated to the head side chamber to perform arm pulling. The speed of operation can be increased. On the other hand, the driving force of the arm pulling operation is suppressed by preventing the back pressure from being generated in the first tank side oil passage 23 during heavy load work (for example, during excavation work) where the discharge pressure of the hydraulic pump 14 is higher than the reference pressure. (Digging force) can be secured.

  Here, since the viscosity of the hydraulic oil has a characteristic that the hydraulic oil becomes higher as the temperature of the hydraulic oil becomes lower, the flow resistance of the hydraulic oil in the oil passage increases and the pressure of the hydraulic oil increases as the hydraulic oil becomes lower in temperature.

  Therefore, the controller 32 sets the reference pressure based on the temperature of the hydraulic oil in order to achieve both the speeding up and securing the driving force even when the hydraulic oil becomes lower than the specific temperature. change.

  Specifically, the controller 32 sets the first pressure PsaL preset based on the specific temperatures TU and TD based on the temperature of the hydraulic oil detected by the temperature detector 31 and the map M1 shown in FIG. And the second pressure PsaH higher than the reference pressure is switched.

  The first specific temperature TU is a reference temperature for switching from the first pressure PsaL to the second pressure PsaH. The second specific temperature TD is a temperature higher than the first specific temperature TU and is a reference temperature for switching from the second pressure PsaH to the first pressure PsaL.

  Thus, the first specific temperature TU for increasing the reference pressure and the second specific temperature TD for decreasing the reference pressure are set to different temperatures. Therefore, it is possible to prevent the reference pressure from frequently switching due to the temperature of the hydraulic oil increasing or decreasing across the specific temperature, as in the case where the reference temperature is raised or lowered at a common (one) specific temperature. .

  In addition, since the viscosity of the hydraulic oil has a characteristic of rapidly increasing below 20 ° C., each specific temperature TU, TD is set to a temperature around 20 ° C. (for example, a temperature of 20 ° C. to 30 ° C.). ing.

  Further, the controller 32 creates the map M2 shown in FIG. 3 based on the reference pressure set according to the temperature of the hydraulic oil as described above, and the hydraulic pump detected by the map M2 and the pressure detector 20 The command values I_H and I_L for the operation valve 29 are determined based on the 14 discharge pressures.

  Here, the command value I_H is a command value sent to the operation valve 29 so that the pilot valve for switching the switching valve 28 shown in FIG. 2 to the regeneration cut position W is output from the operation valve 29. The command value I_L is a command value sent to the operation valve 29 so that the pilot pressure for switching the switching valve 28 to the regeneration position V is output from the operation valve 29.

  Hereinafter, the processing executed by the controller 32 will be described with reference to FIG.

  When processing by the controller 32 is started, it is first determined whether or not an arm pulling operation has been performed based on a detection value by the operation amount detector 19 (step S1).

  When the arm pulling operation is performed (YES in step S1), the temperature T of the hydraulic oil is detected by the temperature detector 31, and this is input to the controller 32 (step S2).

  Next, a reference pressure is determined based on the temperature T input in step S2 and the map M1 (step S3).

  Specifically, when the currently set reference pressure is the first pressure PsaL, when the temperature T is equal to or lower than the first specific temperature TU, the reference pressure is switched to the second pressure PsaH, and the temperature T is the first pressure PsaL. When the temperature is higher than the specific temperature TU, the reference pressure is maintained at the first pressure TD.

  On the other hand, when the currently set reference pressure is the second pressure PsaH, when the temperature T is equal to or lower than the second specific temperature TD, the reference pressure is maintained at the second pressure PsaH and the temperature T is the second specific temperature. When the temperature is higher than TD, the reference pressure is switched to the first pressure PsaL.

  Note that step S3 in FIG. 3 shows a state in which the second pressure PsaH is determined by the temperature T.

  When the reference pressure is thus determined, the discharge pressure P of the hydraulic pump 14 is detected by the pressure detector 20, and this is input to the controller 32 (step S4).

  Next, a command value for the operation valve 29 is determined based on the discharge pressure P input in step S4 and the reference pressure (map M2) determined in step S3 (step S5).

  Specifically, the command value is set to I_H when the discharge pressure P is equal to or lower than the reference pressure (second pressure PsaH in FIG. 3), and the command value is set to I_L when the discharge pressure P is higher than the reference pressure. The

  Note that step S5 in FIG. 3 shows a state in which the command value I_L is determined by the discharge pressure P.

  Then, the command value determined in this way is output to the operation valve 29 (step S6), and the process returns to step S1.

  As described above, when the temperature T of the hydraulic oil is on the low temperature side based on the specific temperature TU (or TD), the temperature T of the hydraulic oil is on the high temperature side based on the specific temperature TU (or TD) The reference pressure can be changed higher than that (change from the first pressure PsaL to the second pressure PsaH). For this reason, even if the discharge pressure increases as the hydraulic fluid temperature T (viscosity) decreases due to a situation that should be regenerated, the switching valve 28 is prevented from being switched to the regeneration cut position W. be able to.

  Moreover, according to the said embodiment, there exist the following effects.

  In the embodiment, since the reference pressure is switched between the first pressure PsaL and the second pressure PsaH with the specific temperature TU (or TD) as a boundary, the reference pressure is set for each temperature of the hydraulic oil. Compared to the above, the process of changing the reference pressure can be simplified.

  In the embodiment, the first temperature TU that serves as a reference for increasing the reference pressure and the second temperature TD that serves as a reference for decreasing the reference pressure are set to different temperatures. Therefore, it is possible to prevent the reference pressure from frequently switching due to increase or decrease in the temperature of the hydraulic oil across the specific temperature as in the case where one temperature is set as the specific temperature.

  In the above embodiment, the regeneration during the arm pulling operation is described as an example. However, the hydraulic actuator to be regenerated is a boom cylinder 9 for raising and lowering the boom (driven member) 6 shown in FIG. And the bucket cylinder 11 which rotates the bucket (driven member) 8 may be sufficient.

TD, TU Specific temperature V Regeneration position W Regeneration cut position 1 Hydraulic excavator (an example of construction machinery)
5 Hydraulic control device 7 Arm (an example of driven member)
10 Arm cylinder (example of hydraulic actuator)
DESCRIPTION OF SYMBOLS 14 Hydraulic pump 15 Tank 16 Supply / discharge circuit 17 Regeneration circuit 20 Pressure detector 22 Pump side oil path (an example of supply oil path)
23 First tank side oil passage (an example of a discharge oil passage)
27 Reclaimed oil passage 27a Check valve (an example of regeneration switching means)
28 selector valve (an example of regeneration switching means)
31 Temperature detector 32 Controller

Claims (4)

A hydraulic pump and a tank;
A hydraulic actuator driven by hydraulic oil from the hydraulic pump;
A supply / discharge circuit including a supply oil path for supplying hydraulic oil from the hydraulic pump to the hydraulic actuator, and a discharge oil path for discharging hydraulic oil from the hydraulic actuator to the tank;
A regeneration oil passage connecting the supply oil passage and the discharge oil passage, a regeneration state allowing the flow of hydraulic oil from the discharge oil passage to the supply oil passage through the regeneration oil passage, and the regeneration oil passage A regeneration circuit including regeneration switching means that is switchable between a regeneration cut state that restricts the flow of the hydraulic oil;
A pressure detector for detecting a discharge pressure of the hydraulic pump;
A temperature detector for detecting the temperature of the hydraulic oil;
The regeneration switching means is switched to the regeneration state when the discharge pressure detected by the pressure detector is below a reference pressure, and the regeneration switching means is switched to the regeneration cut when the discharge pressure is higher than the reference pressure. A controller for switching to a state,
When the temperature of the hydraulic oil detected by the temperature detector is on the low temperature side based on a specific temperature determined in advance based on the viscosity characteristics of the hydraulic oil, the controller is higher than the temperature on the high temperature side. A hydraulic control device that changes the reference pressure so that the reference pressure becomes higher.   2. The hydraulic control device according to claim 1, wherein the controller switches the reference pressure between a first pressure set in advance and a second pressure higher than the first pressure with the specific temperature as a boundary.   As the specific temperature, a first specific temperature serving as a reference for switching from the first pressure to the second pressure, and a reference different from the first specific temperature and switching from the second pressure to the first pressure. The hydraulic control apparatus according to claim 2, wherein a second specific temperature is set. A base machine,
A driven member movably attached to the base machine;
A construction machine comprising the hydraulic control device according to claim 1, further comprising a hydraulic actuator for driving the driven member.

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