JP4976920B2 - Pump discharge control device - Google Patents

Description

  The present invention relates to an improvement of a pump discharge amount control device.

  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 pilot pressure gear pump disposed coaxially with a swash plate type piston pump is provided. The signal pressure acting on the tilt regulator that controls the tilt angle of the swash plate is adjusted to control the discharge flow rate to be variable according to the rotational speed of the swash plate type piston pump.
JP 2002-202063 A

  However, the target differential pressure of the tilt regulator is set during operation at the rated speed of the piston pump. For example, if the rated speed of the piston pump varies to the lower side, the discharge flow rate decreases, and the hydraulic machine There is a risk that the operating speed of the actuator included in the actuator will be reduced.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a pump discharge amount control device that maintains a predetermined discharge flow rate even if the rated rotational speed of the piston pump varies.

The present invention provides a first pump in which a pump discharge amount supplied to a hydraulic circuit is variable according to a tilt angle of the swash plate, and reduces a tilt angle of the swash plate according to an increase in the supplied control pressure. A tilting actuator, a first regulator that changes the control pressure supplied to the tilting actuator according to the pump discharge pressure, and a control pressure supplied from the first regulator to the tilting actuator. in the pump discharge amount control device and a second regulator to adjust in accordance with the load pressure of the hydraulic circuit, via a second pump in conjunction with the first pump, the discharge circuit of said second pump instrumentation and the orifice, and an actuator for driving so as to reduce the control pressure that is adjusted by the second regulator in response to an increase in differential pressure across the orifice, the orifice Scan and provided in parallel, the differential pressure of the orifice and a relief valve that opens when exceeding a predetermined value, the predetermined rotational speed or more of the pump, the differential pressure by the relief valve is opened is substantially the same is maintained in the pump discharge amount of the first pump is a pump discharge amount control apparatus, characterized in that to not increase any more.

  According to the present invention, when the rotational speed of the drive source is equal to or higher than the predetermined rotational speed, the orifice operates a relief function to maintain the differential pressure at the predetermined differential pressure, and the discharge flow rate of the first pump at the predetermined rotational speed. Since the regulator controls the hydraulic pressure supplied to the first pump so as to maintain the discharge flow rate, the predetermined discharge flow rate can be maintained even if the rated rotation speed of the first pump varies due to variations in the rotation speed of the drive source. .

  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 two pumps arranged coaxially and driven by the engine 1. The first pump 10 is a swash plate type double piston pump capable of changing the discharge flow rate, and the second pump 12 is constituted by, for example, a gear pump whose discharge flow rate is defined according to the rotational speed of the engine 1.

  The first pump 10 includes a discharge port 16, a first main flow path 20 communicates with the discharge port 16, and hydraulic oil from the first port 24 drives, for example, a shovel bucket through a flow path (not shown). Supplied to the cylinder. The second main flow path 36 communicates with the discharge port 28 of the second pump 12, and low pressure (so-called pilot pressure) hydraulic oil is supplied from the second port 32.

  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 the discharge pressure of the first pump 10 is changed from the first source pressure channel 50 to the first signal pressure channel so that one end of the spool is switched at positions a and b. 58 is supplied as a signal pressure. The urging force of the horsepower control spring 44 against the supplied hydraulic pressure acts on the other end of the spool.

  The horsepower control regulator 40 has positions a and b defined by the magnitude relationship between the signal pressure based on the discharge pressure of the first pump 10 acting on one end of the spool and the urging force of the horsepower control spring 44 acting on the other end. .

  The horsepower control regulator 40 switches to the position b when the signal pressure based on the discharge pressure of the first pump 10 is smaller than the urging force of the horsepower control spring 44, and the third original pressure flow connected to the load sensing valve 42 which is a servo valve. The suction side flow path 56 connected to the suction side of each pump via the path 75 and the drain flow path 59 is in communication.

  On the other hand, when the signal pressure based on the discharge pressure of the first pump 10 is larger than the urging force of the horsepower control spring 44, the first original pressure flow path is switched to the position a and the hydraulic oil in the first main flow path 20 is guided. 50 and the 3rd original pressure flow path 75 will be in a communication state.

  A load sensing regulator is provided in the middle of the fourth source pressure channel 74 that transmits the pressure of the third source pressure channel 75 switched by the horsepower control regulator 40 to the large diameter actuator 76 that changes the tilt angle of the swash plate of the first pump 10. A load sensing valve 42 is provided. The load sensing valve 42 is switched by detecting the hydraulic circuit load pressure acting on the first and second ports 24, 32 and the like. For this reason, 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 third port 60, and the third 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.

  In addition, the hydraulic pressure from the fourth 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 third port 60. A flow path downstream of the control valve is connected to the fourth port 62, and therefore the hydraulic pressure supplied from the fourth port 62 to the spool is, for example, a pressure based on the load pressure supplied to the bucket cylinder.

  Further, the acting force of the hydraulic actuator 64 is configured to act on the spool as the acting force against the signal pressure from the third port 60.

  Pilot hydraulic oil from the second pump 12 is supplied to the hydraulic actuator 64 via the differential pressure channel 70 and the second main channel 36 to the left and right oil chambers sandwiching the piston, respectively. An orifice 68 is installed in the middle of the second main flow path 36 to be connected, and the differential pressure flow path 70 is branched from the upstream side of the orifice 68. Therefore, the hydraulic actuator 64 connected to the spool of the load sensing valve 42 is connected to the orifice 68. In response to the differential pressure before and after, an acting force is generated to move the rod to the right side in the figure, that is, to move the spool to the right side.

  Accordingly, the position of the load sensing valve 42 is such that the hydraulic oil pressure (signal pressure) from the fourth port 62 and the hydraulic actuator 64 are different from the hydraulic pressure (signal pressure) from the third 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 third port 60 is larger than the total signal pressure from the fourth port 62 and the like, the spool moves to the left side in the figure and becomes the position d. A second source pressure channel 73 connected to the main channel 20 through which high-pressure hydraulic fluid flows and a fourth source pressure channel 74 connected to a 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 third port 60 is smaller than the total signal pressure of the fourth port 62 and the like, the spool moves to the right side in the drawing to the position c, and the third original pressure flow communicating with the horsepower control regulator 40 The passage 75 and the fourth source pressure passage 74 communicate with each other.

  When the hydraulic pressure supplied from the load sensing valve 42 to the large-diameter actuator 76 increases, the large-diameter actuator 76 reduces the tilt angle of the swash plate, that is, in the direction in which the discharge flow rate of the first pump 10 decreases. Tilt. A small-diameter actuator 78 that generates an action force that opposes the action force of the large-diameter actuator 76 is provided. The small-diameter actuator 78 is configured so that the pressure receiving area of the piston is smaller than that of the large-diameter actuator 76. The small-diameter actuator 78 is supplied with hydraulic pressure from a fifth original pressure channel 61 that branches from the first main channel 20. Therefore, even if the same hydraulic pressure is applied, the tilt angle of the swash plate is defined by the magnitude relationship between the pressure receiving area of the large diameter actuator 76 and the pressure receiving area of the small diameter actuator 78.

  The hydraulic actuator 64 is supplied with hydraulic oil at the pilot pressure of the second pump 12 into the oil chamber. The piston of the hydraulic actuator 64 is sandwiched, and the oil chamber on the right side (load sensing valve 42 side) passes through the second main channel 36, and the oil chamber on the left side from the differential pressure channel 70 branched from the second main channel 36, respectively. Hydraulic pressure is supplied. Further, an orifice 68 is installed between the branch point of the second main flow path 36 and the differential pressure flow path 70 connected to the oil chamber on the right side in the drawing and the hydraulic actuator 64, and the pressure difference before and after the orifice 68 is determined by the hydraulic actuator. In response to this differential pressure, the rod of the hydraulic actuator 64 connected to the spool of the load sensing valve 42 expands to generate an acting force that moves the spool to the right side in the drawing, that is, to the right side. A relief valve 69 is provided in parallel with the orifice 68, and when the differential pressure across the orifice exceeds a predetermined value, the relief valve 69 opens. For this reason, the differential pressure between the front and rear of the orifice 68 is a predetermined discharge pressure of the second pump 12. As described above, in other words, a predetermined differential pressure is maintained at a predetermined rotational speed of the engine 1 or more.

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

  In the hydraulic circuit configured as described above, when a load pressure is applied to 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 a discharge pressure of 10 is regulated and sent to the load sensing valve 42 through the first source pressure channel 50 and the third source pressure channel 75. Since the load sensing valve 42 is at the position c, the hydraulic oil from the third source pressure channel 75 is supplied to the large diameter actuator 76 through the fourth source pressure channel 74, and the large diameter actuator 76 increases the supplied hydraulic pressure. Accordingly, the stroke is performed so as to reduce the tilt angle of the swash plate of the first pump 10.

  Therefore, when the discharge pressure of the first pump 10 increases, the tilt angle of the swash plate of the first pump 10 is changed, and the discharge flow rate is reduced.

  On the other hand, when the discharge pressure of the first pump 10 decreases, the spool of the horsepower control regulator 40 moves to the left in the figure by the urging force of the horsepower control spring 44 and switches to the position b. And the suction side channel 56 communicate with each other through the drain channel 59. The third source pressure channel 75 communicates with the fourth source pressure channel 74 via the position c of the load sensing valve 42. Therefore, the hydraulic oil of the large diameter actuator 76 is discharged to the suction side flow path 56 through the fourth original pressure flow path 74 and the third original pressure flow path 75, and the large diameter actuator 76 defining the tilt angle of the swash plate of the first pump 10. The hydraulic pressure acting on the swash plate of the first pump 10 is increased by the small diameter actuator 78. 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 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 the hydraulic pressure supplied to the large-diameter actuator 76 is changed. The discharge flow rate is maintained and eventually 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 can be set as equal horsepower control for controlling the driving horsepower of the first pump 10 to be substantially constant.

  Next, the action of the load sensing valve 42 that is displaced according to the balance of the signal pressure acting on both ends of the spool will be described.

  For example, in the case of a low load where the load pressure supplied to the bucket cylinder is no load, the load sensing valve 42 switches to the position d according to the low load pressure, and the hydraulic pressure based on the discharge pressure of the first pump 10. Is supplied to the large-diameter actuator 76 through the second source pressure channel 73 and the fourth source pressure channel 74. Accordingly, the hydraulic pressure of the same pressure is supplied to the large-diameter actuator 76 and the small-diameter actuator 78, and the tilt angle of the swash plate of the first pump 10 is minimized according to the ratio of the pressure receiving areas of these actuators 76 and 78.

  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.

  The load increases from this state, and the differential pressure between the signal pressure from the third port 60 and the total signal pressure from the fourth port 62, the hydraulic actuator 64, etc. changes, and the spool is shown in the figure according to the differential pressure. Move to the right. When the position of the spool is set at an intermediate position between the position c and the position d, the second source pressure channel 73 and the third source pressure channel 75 communicate with the fourth source pressure channel 74.

  Therefore, hydraulic oil is supplied to the large-diameter actuator 76 from the second source pressure channel 73 and the third source pressure channel 75 according to the opening degree of the load sensing valve 42. Here, the hydraulic pressure supplied to the load sensing valve 42 is higher than the hydraulic pressure from the third source pressure channel 75 connected to the horsepower control regulator 40 in the second source pressure channel 73 connected to the first main channel 20. Set high. For this reason, when the load sensing valve 42 is at an intermediate opening between the positions c and d, the regulated hydraulic pressure is larger than the fourth source pressure channel 74 due to the influence of the second source pressure channel 73. To the radial actuator 76. Thereby, the tilt angle of the first pump 10 is relatively small, that is, the discharge flow rate is also relatively smaller than that during the horsepower control.

  Next, pump discharge flow rate control based on engine speed will be described.

  Therefore, when the rotational speed of the engine 1 is low and the differential pressure of the orifice 68 is sufficiently smaller than the predetermined differential pressure, the opening on the position d side of the horsepower control regulator 40 is large, and the hydraulic pressure acting on the large-diameter actuator 76 is the first. Close to the high pressure side hydraulic pressure from the binary pressure flow path 73, the discharge flow rate of the first pump 10 is limited.

  Then, as the rotational speed of the engine 1 increases and the differential pressure at the orifice 68 increases, the regulated hydraulic pressure supplied to the large-diameter actuator 76 is shared by the low-pressure side hydraulic pressure from the third source pressure channel 75. As the rate increases, it decreases, and as a result, the discharge flow rate of the first pump 10 increases as the rotational speed of the engine 1 increases.

  Thus, until the differential pressure generated by the orifice 68 reaches a predetermined differential pressure, the discharge flow rate of the first pump 10 is controlled to increase in proportion to the increase in the rotational speed of the engine 1.

  The orifice 68 is provided with a relief mechanism that maintains the differential pressure at a predetermined value by opening the relief valve 69 at a predetermined rotational speed of the first pump 10 or more, and is above the predetermined rotational speed of the first pump 10 (≈engine 1). Thus, the load sensing valve 42 is held constant by pressure regulation control based on the rotational speed. Therefore, at a speed higher than the rotational speed of the engine 1 that generates a predetermined differential pressure, even if the load sensing valve 42 has the same opening, the first pressure is increased according to the increase in the pump discharge pressure supplied to the large-diameter actuator 76 due to the increased rotational speed. The tilt angle of the swash plate of one pump 10 changes in the direction of decreasing the discharge flow rate. Therefore, as the overall discharge flow rate of the first pump 10, the increase in the discharge flow rate due to the increase in the number of revolutions of the engine 1 and the decrease in the discharge flow rate due to the change in the tilt angle of the swash plate are cancelled. The discharge flow rate of the first pump 10 is controlled to be substantially constant above the engine 1 speed.

  Next, the effect of providing the orifice 68 with the relief mechanism will be described with reference to FIG.

  In FIG. 2, the broken line indicates the characteristic of the discharge flow rate with respect to the conventional first pump rotation speed (≈the rotation speed of the engine 1), and the discharge flow rate increases in proportion to the increase in the rotation speed. And it sets so that it may become predetermined | prescribed discharge flow rate with a rated rotation speed, and even if it exceeds a rated rotation speed, the discharge flow rate is increasing in proportion to rotation speed. However, for example, when the rated rotational speed of the first pump 10 decreases due to variations in the rotational speed of the engine 1, the discharge flow rate decreases by A, and the operating speed of the actuator supplied with hydraulic oil decreases. Will do.

  In the present invention, the orifice 68 having a relief function for maintaining the differential pressure constant at a predetermined rotational speed of the engine 1 that generates the predetermined differential pressure is provided in the flow path for supplying the signal pressure to the load sensing valve 42. For this reason, the differential pressure is maintained at a predetermined differential pressure by the relief function of the orifice 68 at a predetermined rotational speed or higher, and the tilt angle of the swash plate changes so that the discharge flow rate decreases as the rotational speed of the engine 1 increases. By doing so, the discharge flow rate of the first pump 10 is made constant. Then, the tilt angle of the swash plate is set so that the discharge flow rate at the lower limit value of the rated rotational speed at which the predetermined differential pressure occurs is the same as the discharge flow rate at the rated rotational speed of the first pump 10.

  With such a configuration, even when the rated rotational speed of the engine varies, the hydraulic fluid is supplied with the discharge flow rate discharged from the first pump 10 as the specified discharge flow rate at the rated rotational speed. The operation speed can be kept constant.

  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. It is a figure explaining the flow volume characteristic of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 10 1st pump 12 2nd pump 20 1st main flow path 24 1st port 28 Discharge port 32 2nd port 36 2nd main flow path 40 Horsepower control regulator (1st regulator)
42 Load sensing valve (second regulator)
44 Horsepower Control Spring 50 First Primary Pressure Channel 56 Suction Side Channel 58 First Signal Pressure Channel 59 Drain Channel 64 Hydraulic Actuator 68 Orifice 69 Relief Valve 70 Differential Pressure Channel 73 Second Source Pressure Channel 74 Fourth Source Pressure Channel 75 Third source pressure channel 76 Large diameter actuator 78 Small diameter actuator

Claims (3)

A first pump in which a pump discharge amount supplied to the hydraulic circuit is variable according to a tilt angle of the swash plate;
A tilt actuator that reduces the tilt angle of the swash plate in response to an increase in the supplied control pressure;
A first regulator that changes the control pressure supplied to the tilt actuator according to the pump discharge pressure;
A second regulator for adjusting a control pressure supplied from the first regulator to the tilting actuator according to a load pressure of the hydraulic circuit;
In the pump discharge amount control device equipped with
A second pump in conjunction with the first pump;
An orifice interposed in the discharge circuit of the second pump ;
An actuator that drives to reduce the control pressure adjusted by the second regulator in response to an increase in differential pressure across the orifice;
A relief valve that is provided in parallel with the orifice and opens when a differential pressure across the orifice exceeds a predetermined value;
With
In more than a predetermined rotational speed of said pump, and wherein the differential pressure by the relief valve is opened is maintained substantially the same, and to a pump discharge amount of the first pump does not increase any more Pump discharge amount control device. Predetermined rotational speed, the pump discharge amount control apparatus according to claim 1, characterized in that the lower limit value of the variation of the rated speed of the first pump. Predetermined discharge flow rate of the rotation speed, the pump discharge amount control apparatus according to claim 1 or 2, characterized in that the discharge flow rate of the rated speed of the first pump.

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