JP5004665B2 - Piston pump hydraulic circuit - Google Patents

Description

  The present invention relates to an improvement in the hydraulic circuit of a piston pump, and in particular to an improvement in the response of the hydraulic circuit.

  Conventionally, a swash plate type piston pump including a horsepower control regulator that controls a discharge pressure and a discharge flow rate with a constant horsepower characteristic in which horsepower (that is, output) becomes substantially constant is known (see Patent Document 1). The swash plate type piston pump is used in a hydraulic machine such as a mini excavator, and the swash plate type piston pump is driven by an output from an engine of the hydraulic machine.

In such a hydraulic circuit of a conventional hydraulic machine, a load sensing valve for controlling the tilt angle of the swash plate of the piston pump, that is, the discharge flow rate of the piston pump, is provided downstream of the horsepower control regulator via a hydraulic actuator. Therefore, the hydraulic oil discharged from the piston pump is supplied to a hydraulic actuator that controls the tilt angle of the swash plate of the piston pump via a horsepower control regulator and a load sensing valve (load sensing regulator).
JP 2002-202063 A

  When the discharge pressure is changed during the equal horsepower control, the discharge flow rate of the piston pump changes so as to maintain the equal horsepower characteristics. However, since the change in the discharge pressure is transmitted to the hydraulic actuator that tilts the swash plate by flowing hydraulic oil through the horsepower control regulator, the load sensing valve, and the flow path connecting them, there is a time lag that is a time delay. This causes a problem that the change in the discharge flow rate is delayed and the responsiveness deteriorates.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a hydraulic circuit that improves the responsiveness of the discharge flow rate to a change in the discharge pressure in the hydraulic circuit of the piston pump.

The present invention relates to each main flow path connected to each discharge port of a swash plate type double piston pump with variable discharge flow rate, and connected to this main flow path, according to the average pressure of the discharge pressure of the swash plate type double piston pump. A first regulator for supplying a first control hydraulic pressure so as to control a discharge flow rate of the swash plate type double piston pump, and one of the main flow paths connected to a discharge port of the swash plate type double piston pump. A second regulator for supplying a second control hydraulic pressure so as to control a discharge flow rate of the swash plate type double piston pump according to the load of the main flow path, and a first regulator supplied from the first regulator. a high pressure selection valve for selecting the high-pressure side hydraulic of the second control hydraulic pressure supplied control pressure from the second regulator, in accordance with the oil pressure rise that is selected by the high pressure selection valve, the swash plate type twin A first hydraulic actuator for controlling the angle of the swash plate of the swash plate type twin piston pump to reduce the discharge flow rate of the piston pump, in response to an increase in the mean pressure, discharge flow rate of the swash plate type twin piston pump And a second hydraulic actuator for setting an angle of the swash plate of the swash plate type double piston pump so as to increase the swash plate .

  According to the present invention, since the high-pressure hydraulic oil selected by the selection valve passes through the first regulator or the second regulator connected to the main flow path and is supplied to the hydraulic actuator, the conventional system passes through both regulators. Compared with this hydraulic circuit, the time required for the hydraulic oil to reach the hydraulic actuator can be shortened, and the response of the hydraulic actuator can be improved.

  FIG. 1 is a hydraulic circuit diagram to which an orifice structure of a hydraulic circuit according to the present invention is applied.

  The hydraulic circuit is provided with three pumps arranged coaxially and driven by the engine 1. The first pump 10 is a swash plate type double piston pump capable of varying the discharge flow rate, and the second pump 12 and the third pump 14 are configured by a gear pump, for example, whose discharge flow rate is defined according to the rotational speed of the engine 1. Is done.

  The first pump 10 includes two discharge ports 16 and 18, and a first main channel 20 and a second main channel 22 communicate with the respective discharge ports 16 and 18, and the first and second ports 24 and 26 thereof. Hydraulic fluid is supplied to a bucket cylinder that drives, for example, a shovel bucket through a flow path (not shown). The third main channel 30 communicates with the discharge port 28 of the second pump 12, and hydraulic oil is supplied from the third port 32. Further, the fourth main flow path 36 communicates with the discharge port 34 of the third pump 14, and low pressure (so-called pilot pressure) hydraulic oil is supplied from the fourth port 38.

  The hydraulic circuit includes a horsepower control regulator 40 that tilts the swash plate of the first pump 10 in order to control the discharge flow rate according to the discharge pressure so that the driving horsepower of the first pump 10 becomes substantially constant.

  The horsepower control regulator 40 is a three-port two-position switching valve, and at one end of the spool, the average pressure of the discharge pressure of the first pump 10 and the discharge pressure of the second pump 12 are switched at positions a and b. Supplied as signal pressure. A biasing force of a horsepower control spring 44 against the supplied signal pressure acts on the other end of the spool.

  The sub flow paths for supplying the average discharge pressure of the first pump 10 to the spool of the horsepower control regulator 40 are a first signal pressure flow path 46 and a second signal pressure flow path branched from the first and second main flow paths 20 and 22, respectively. 48 and a third signal pressure channel 50 in which the first and second signal pressure channels 46 and 48 merge, and the third signal pressure channel 50 supplies a hydraulic pressure as a signal pressure to the spool of the horsepower control regulator 40. . Orifices 52 and 54 are installed in the first and second signal pressure channels 46 and 48 to relieve pressure pulsations in the first and second main channels 20 and 22 for transmission. Further, a first source pressure channel 58 connected to the joining portion of the first and second signal pressure channels 46 and 48 is further formed. This first source pressure channel 58 is connected to a predetermined port of the horsepower control regulator 40. The hydraulic pressure supplied from the first original pressure flow path 58 becomes the original pressure of the horsepower control regulator 40.

  The horsepower control regulator 40 includes a signal pressure based on the sum of the average discharge pressure of the first pump 10 acting on one end of the spool and the discharge pressure of the second pump 12, and a horsepower control spring 44 acting on the other end. Positions a and b are defined by the magnitude relationship with the power.

  The horsepower control regulator 40 switches to the position b when the signal pressure based on the combined pressure of the average discharge pressure of the first pump 10 and the discharge pressure of the second pump 12 is smaller than the urging force of the horsepower control spring 44, A fourth source pressure channel 77 connected to a large-diameter actuator 76 for controlling the tilt angle of the swash plate of the first pump 10 via a fifth source pressure channel 74 and a first drain channel 59 communicate with each other. The suction side flow path 56 which is a drain flow path provided on the suction side of each of the pumps 10, 12, and 14 through the drain flow path 59 is in communication.

  On the other hand, when the signal pressure based on the combined pressure of the average discharge pressure of the first pump 10 and the discharge pressure of the second pump 12 is larger than the urging force of the horsepower control spring 44, the position a is switched to the first, A first source pressure channel 58 through which hydraulic oil having an average pressure in the second main channels 20 and 22 is guided communicates with a fourth source pressure channel 77. The hydraulic oil is supplied from the first source pressure channel 58 and the fourth source pressure channel 77 to the large-diameter actuator 76 that tilts the swash plate of the first pump 10 via the fifth source pressure channel 74.

  A load sensing valve (load sensing regulator) is provided in the middle of the second source pressure channel 73 that transmits a pressure based on the discharge pressure of the second main channel 22 to the large-diameter actuator 76 that changes the tilt angle of the swash plate of the first pump 10. 42 is provided. The load sensing valve 42 is switched by detecting the load pressure acting on the first to third ports 24, 26, 32, etc. Therefore, both ends of the spool of the load sensing valve 42 are for positioning the spool. Each signal pressure is applied.

  One is the hydraulic pressure from the fifth port 60, and the fifth port 60 is supplied with pressure based on the pressure upstream of a control valve (not shown) installed downstream of the first and second ports 24 and 26. The Here, the control valve is a valve for controlling a bucket cylinder for operating a bucket of a hydraulic machine, for example, a power shovel.

  Also, the hydraulic pressure from the sixth port 62 acts on the opposite end of the spool as the second signal pressure against the signal pressure based on the hydraulic pressure of the fifth port 60. A flow path downstream of the control valve is connected to the sixth port 62, and therefore the hydraulic pressure supplied from the sixth port 62 to the spool is based on the load pressure supplied to the bucket cylinder, for example.

  Further, as an action force against the signal pressure from the fifth port 60, the action force of the hydraulic actuator 64 is configured to act on the opposite end of the spool.

  The hydraulic actuator 64 is supplied with the pilot hydraulic oil of the third pump 14 through the first and second differential pressure passages 70 and 72 to the left and right oil chambers sandwiching the piston, but is connected to the right oil chamber in the figure. In the middle of the fourth main flow path 36 upstream of the second differential pressure flow path 72, an orifice 68 is installed. This produces an action force that moves to

  Therefore, the position of the load sensing valve 42 is such that the hydraulic oil pressure (signal pressure) from the sixth port 62 and the hydraulic actuator 64 are different from the hydraulic pressure (signal pressure) from the fifth port 60 acting on the spool. It is defined by the magnitude relationship of the total acting force with the acting force.

  The load sensing valve 42 has three ports. When the signal pressure from the fifth port 60 is larger than the total signal pressure from the sixth port 62 and the like, the spool moves to the left side in the figure and switches to the position d. The second source pressure channel 73 through which the hydraulic oil flows and the third and fifth source pressure channels 71 and 74 connected to the large-diameter actuator 76 that tilts the swash plate of the first pump 10 communicate with each other.

  On the other hand, when the signal pressure from the fifth port 60 is smaller than the total signal pressure of the sixth port 62 and the like, the spool moves to the right side in the figure and switches to the position c, and the third source pressure channel 71 and the second drain channel 75, the second drain passage 75 communicates with the suction side passage 56 which is a drain passage without passing through the horsepower control regulator 40, and the hydraulic oil is drained to a drain tank (not shown).

  When the hydraulic pressure supplied from the load sensing valve 42 or the horsepower control regulator 40 to the large-diameter actuator 76 increases, the large-diameter actuator 76 decreases the tilt angle of the swash plate, that is, the discharge flow rate of the first pump 10 decreases. Tilt the swashplate in the direction A small-diameter actuator 78 that generates an urging force that resists this acting force is provided, and the small-diameter actuator 78 has a sixth branch branched from the first source pressure channel 58 through which hydraulic oil having an average discharge pressure of the first pump 10 flows. It is supplied through the original pressure channel 61. Therefore, the stroke amount of the large-diameter actuator 76 is defined by the magnitude relationship between the hydraulic pressure acting on the large-diameter actuator 76 and the hydraulic pressure acting on the small-diameter actuator 78. Here, the pressure receiving area of the large diameter actuator 76 is formed larger than the pressure receiving area of the small diameter actuator 78, and the tilt angle of the swash plate of the first pump 10 depends on the ratio of the pressure receiving areas and the horsepower control spring 44. Set by biasing force.

  A fourth source pressure channel 77 connected to the horsepower control regulator 40 is connected to the intersection point where the third source pressure channel 71 connected to the load sensing valve 42 and the fifth source pressure channel 74 connected to the large diameter actuator 76 are connected. . A high-pressure selection valve 79 is provided at this intersection to selectively flow high-pressure hydraulic oil among the hydraulic oil in the third source pressure channel 71 and the hydraulic oil in the fourth source pressure channel 71 to the fifth source pressure channel 74. Is done.

  Next, the operation of the horsepower control regulator 40 will be described.

  In the hydraulic circuit configured as described above, when negative pressure is acting on the hydraulic circuit, that is, when the load sensing valve 42 detects a load, the spool of the load sensing valve 42 acts on the signal pressure, etc. In accordance with the difference, the right side of the figure moves to the right, and the position c is switched over at a predetermined load pressure or higher. In this state, when the discharge pressure of the first pump 10 rises, the spool of the horsepower control regulator 40 moves to the right in the figure against the urging force of the horsepower control spring 44 and switches to the position a. The hydraulic oil having an average discharge pressure of 10 is regulated and sent to the high pressure selection valve 79 through the first original pressure channel 58 and the fourth source pressure channel 77. Further, the hydraulic oil in the second main channel 22 is sent to the load sensing valve 42 through the second source pressure channel 73. Since the load sensing valve 42 is in the position c, the second source pressure channel 73 is closed, and the hydraulic oil in the third source pressure channel 71 is drained from the second drain channel 75. For this reason, the high-pressure hydraulic fluid from the first source pressure channel 58 is supplied to the large diameter actuator 76 through the fourth source pressure channel 77, the high pressure selection valve 79, and the fifth source pressure channel 74, and the large diameter actuator 76 is supplied. The stroke is performed so as to reduce the tilt angle of the swash plate of the first pump 10 according to the hydraulic pressure.

  Therefore, when the discharge pressure (average discharge pressure) of the first pump 10 increases, the tilt angle of the swash plate of the first pump 10 is changed to reduce the discharge flow rate. Here, the average discharge pressure of the first pump 10 is also supplied to the small-diameter actuator 78 through the sixth source pressure channel 61. For this reason, the same pressure acts on the large-diameter actuator 76 and the small-diameter actuator 78, and the tilt angle of the swash plate is determined by the ratio of the pressure receiving area of each actuator and the urging force of the horsepower control spring 44.

  On the other hand, when the increased discharge pressure of the first pump 10 decreases, the spool of the horsepower control regulator 40 moves to the left side in the drawing and switches to the position b, and the hydraulic oil in the fourth source pressure channel 77 is the first. Drain from the drain channel 59 to the suction side channel 56. The second drain channel 75 communicates with the third source pressure channel 71 via the position c of the load sensing valve 42. Therefore, the hydraulic oil of the large-diameter actuator 76 drains to the suction side flow channel 56 through the third original pressure flow channel 71 and the second drain flow channel 75. Accordingly, the hydraulic pressure acting on the large-diameter actuator 76 that defines the tilt angle of the swash plate of the first pump 10 is reduced, and the tilt angle of the swash plate of the first pump 10 is increased by the small-diameter actuator 78 and the horsepower control spring 44. To do. Thereby, it changes to the direction where the discharge flow volume of the 1st pump 10 increases.

  Here, the tilt angle of the swash plate of the first pump 10 is fed back to the horsepower control spring 44 of the horsepower control regulator 40, and the swash plate is stopped at a position balanced with the pump discharge pressure. That is, one end of the horsepower control spring 44 is connected to the swash plate of the first pump 10, and when the swash plate tilts and changes in a direction in which the discharge flow rate decreases, the horsepower control spring 44 increases the urging force. When the swash plate tilts to the opposite side, the urging force decreases. Therefore, when the swash plate tilt angle corresponding to the average pressure of the discharge pressure of the first pump 10 is reached, the position of the horsepower control regulator 40 is alternately switched by the balance with the horsepower control spring 44 and supplied to the large-diameter actuator 76. Therefore, the discharge flow rate is determined according to the pump discharge pressure.

  As described above, the discharge flow rate is decreased when the discharge pressure of the first pump 10 is increased, and on the other hand, the discharge flow rate is increased according to the discharge pressure and the discharge flow rate when the discharge pressure is decreased. It is possible to perform equal horsepower control for controlling the horsepower of the first pump 10 to be substantially constant.

  Next, the operation of the load sensing valve 42 will be described.

  The load sensing valve 42 is displaced according to the balance of the signal pressure acting on both ends of the spool. When the load pressure supplied from the sixth port 62 is equal to or higher than a predetermined pressure (high load range), the load sensing valve 42 is positioned at position c. Located in.

  When the load pressure decreases from this state, the differential pressure between the signal pressure from the fifth port 60 and the signal pressure from the sixth port 62 and the like changes, and the spool moves according to the differential pressure. When the position of the spool is set at an intermediate position between position c and position d, the second source pressure channel 73 and the second drain channel 75 communicate with the third source pressure channel 71. Here, the hydraulic pressures in the second source pressure channel 73 and the second drain channel 75 are added and adjusted according to the opening degree of the load sensing valve 42, and are adjusted from the third source pressure channel 71 to the high pressure selection valve 79. Supplied.

  Furthermore, for example, when the load pressure supplied to the bucket cylinder is low, such as no load, the load sensing valve 42 switches to position d in response to the low load pressure, and the discharge pressure of the first pump 10 is reduced. The high pressure selection valve 79 is supplied through the second source pressure channel 73 and the third source pressure channel 71. At this time, the horsepower control regulator 40 switches to the position b because the discharge pressure is low, and as a result, the high pressure selection valve 79 selects the hydraulic pressure of the third source pressure channel 71 and supplies it to the large diameter actuator 76.

  In this way, when the load pressure is a low pressure such as an unloaded state, the discharge flow rate is reduced to the minimum value even if the discharge pressure of the first pump 10 is low without performing the equal horsepower control.

  In the hydraulic circuit of the present invention, the supply of hydraulic oil to the large-diameter actuator 76 and the discharge of hydraulic oil from the large-diameter actuator 76 only pass through either the horsepower control regulator 40 or the load sensing valve 42. Compared with a configuration in which both are supplied to the large-diameter actuator 76 or drained, the flow length from the horsepower control regulator 40 or the load sensing valve 42 to the large-diameter actuator 76 and the large-diameter actuator 76 are drained. The flow path length up to can be shortened, the response of the large-diameter actuator 76 can be improved, and as a result, the operability can be improved.

  Further, when the discharge pressure of the first pump 10 is low and the discharge pressure of the second pump 12 is high, the position of the horsepower control regulator 40 is at the position a due to the action of the discharge pressure of the second pump 12. The load sensing valve 42 is in the position c when the load pressure is equal to or higher than the predetermined pressure, and the third source pressure channel 71 and the second drain channel 75 are in communication with each other. The oil pressure in the fourth source pressure channel 77 connected to the horsepower control regulator 40 becomes higher than the oil pressure in the third source pressure channel 71 connected to the load sensing valve 42, and the hydraulic oil having an average pressure discharged from the first pump 10 is obtained. Is supplied from the first source pressure channel 58 to the large-diameter actuator 76 through the horsepower control regulator 40, the fourth source pressure channel 77 and the fifth source pressure channel 74.

  Therefore, when the discharge pressure of the first pump 10 is low and the discharge pressure of the second pump 12 is high, the hydraulic oil supplied to the large-diameter actuator 76 does not pass through the load sensing valve 42. Even when the discharge pressure of only the pump 12 increases, the length of the flow path for supplying the hydraulic oil to the large-diameter actuator 76 is shortened, and the time until the hydraulic oil reaches the large-diameter actuator 76 is shortened. The response of the diameter actuator 76 can be improved.

  The present invention is not limited to the above-described embodiment, and it is obvious that various modifications can be made within the scope of the technical idea.

  The present invention can be applied to a hydraulic circuit used in a hydraulic machine.

It is a hydraulic circuit diagram to which the present invention is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 1st pump 12 2nd pump 20 1st main flow path 22 2nd main flow path 30 3rd main flow path 40 Horsepower control regulator (1st regulator)
42 Load sensing valve (second regulator)
44 elastic member 46 first signal pressure channel 48 second signal pressure channel 50 third signal pressure channel 52 orifice 56 suction side channel 58 first source pressure channel 59 first drain channel 61 sixth source pressure channel 64 hydraulic actuator 68 Orifice 71 Third source pressure channel 73 Second source pressure channel 74 Fifth source pressure channel 75 Second drain channel 76 Large diameter actuator (first hydraulic actuator)
77 Fourth pressure passage 78 Small-diameter actuator (second hydraulic actuator)
79 High pressure selection valve

Claims (3)

Each main flow path connected to each discharge port of the swash plate type double piston pump with variable discharge flow rate,
A first regulator that is connected to the main flow path and supplies a first control hydraulic pressure so as to control the discharge flow rate of the swash plate type double piston pump according to the average pressure of the discharge pressure of the swash plate type double piston pump. When,
The second flow passage is connected to one of the main flow paths connected to the discharge port of the swash plate type double piston pump, and the discharge flow rate of the swash plate type double piston pump is controlled according to the load of the main flow path. A second regulator for supplying control oil pressure;
A high-pressure selection valve that selects a high- pressure side hydraulic pressure among a first control hydraulic pressure supplied from the first regulator and a second control hydraulic pressure supplied from the second regulator;
A first hydraulic actuator for controlling an angle of a swash plate of the swash plate type double piston pump so as to reduce a discharge flow rate of the swash plate type double piston pump according to an increase in hydraulic pressure selected by the high pressure selection valve ; ,
A second hydraulic actuator that sets an angle of the swash plate of the swash plate type double piston pump so as to increase a discharge flow rate of the swash plate type double piston pump in response to an increase in the average pressure. The hydraulic circuit of the piston pump. The first hydraulic actuator discharges hydraulic oil when increasing the discharge flow rate of the swash plate type double piston pump, and the discharged hydraulic oil is drained via one of the first and second regulators. The hydraulic circuit of the piston pump according to claim 1, wherein A fourth main flow path connected to a discharge port of a third pump driven by the engine together with the swash plate double piston pump;
A hydraulic actuator in which pilot hydraulic oil generated on the upstream side and downstream side of the orifice provided in the middle of the fourth main flow path is supplied to an oil chamber sandwiching the piston,
3. The piston pump hydraulic circuit according to claim 1, wherein the acting force of the hydraulic actuator acts on a spool of the second regulator .

Images