JPH01294979A - electronically controlled pump - Google Patents

Abstract

PURPOSE:To simply an surely damp serge pressure in a discharge line from a pump by connecting an inlet port to the discharge line, and by connecting a spring chamber to an orifice in a pilot line branching off from the discharge line while providing a serve absorbing valve. CONSTITUTION:An electronic controller 17 changes over a servo valve 10 so as to connect the secondary port A thereof to a pilot line 8 branching off from a discharge line 6 connected to a hydraulic cylinder 21 when a serge pressure is produced in the discharge line 6. Further, a pressure control valve 14 is changed over so as to connect its secondary port A top the secondary port A of the servo valve 10. Further, a swash plate 2 in a pump 1 is tilted toward a neutral position so as to discharge oil at a high pressure but at a low flow rate. In this arrangement, with the use of a differential pressure across an orifice 7 in the pilot line 8, the serge pressure is opened. Thereby it is possible to relieve the serge pressure from the discharge line 6 into a tank 22 even though a relief valve 13 does not open.

Description

[Detailed Description of the Invention] <Industry> 2 Field of Application The present invention is an electronic device that tilts a swash plate using a servo valve that receives a deviation signal from an electronic controller and controls the discharge pressure and discharge amount to a target value. Regarding control pumps.

<Prior Art> Conventionally, as this type of electronically controlled pump, for example, a variable displacement pump has a servo cylinder that operates against a bias spring to tilt a swash plate in a neutral direction, and a secondary port has a variable displacement pump as described above. A pilot line branched from the discharge line of the displacement pump is connected to the tank, a safety valve is connected to the pilot line via a throttle, and a secondary port communicating with the servo cylinder is connected to the servo valve. A pressure control valve is connected to the secondary port and the pilot line in response to the differential pressure before and after the throttle, and the detection values of the pressure sensor and swash plate angle sensor installed in the discharge line, as well as the discharge pressure and discharge. It is known to include an electronic controller that outputs a control signal to the servo valve according to the deviation from the set value of the amount. In this electronically controlled pump, when the pressure in the discharge line increases and the safety valve opens, the pressure control valve is switched by the differential pressure before and after the pressure oil flowing through the throttle, and the pressure in the discharge line is guided to the servo cylinder. , the swash plate is tilted to the neutral position to reduce the discharge amount to the minimum I.

<Problems to be Solved by the Invention> Generally, when a hydraulic cylinder is connected to the discharge line of a hydraulic pump via a switching valve or the like and the hydraulic cylinder is driven in a staggered manner, the switching valve is switched at the end of the stroke or the like to switch from large flow rate control to pressure control. It is well known that large pressure surges are generated in the discharge line during transfer. However, the conventional electronically controlled pump described above is only equipped with a safety valve that tilts the swash plate to neutral via a pressure control valve at a set pressure slightly higher than the maximum set pressure. generates oil or surge pressure discharged from the pump while tilting to
Unless a surge absorbing valve is separately installed in the connection line, there is a problem in that various elements of the hydraulic circuit and piping are damaged.

Furthermore, it was thought that the surge absorption valve could only be activated by the differential pressure created before and after the throttle by the vent flow that occurs when the safety valve opens, so there was no compact and useful electronically controlled pump with a built-in surge absorption valve.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a new and useful electronically controlled pump that has a built-in surge absorption valve that is operated by pressure oil from the discharge line without relying on the vent flow of the safety valve, and can sufficiently alleviate the zano pressure in the discharge line. The goal is to provide the following.

<Means for Solving the Problems> In order to achieve the above object, the first electronically controlled pump of the present invention tilts the swash plate 2 t! as illustrated in FIG. −
A variable displacement pump 1 having a rotor cylinder 5, a secondary port A branched from a discharge line 6 of the variable displacement pump 1, and connected to a pilot line 8 having a calibration 7 and a tank 9 by switching and connecting a servo valve 10. , a safety valve 13 connected to the pilot line 8 on the downstream side of the throttle 7, and a secondary port A communicating with the cylinder 5 of the variable displacement pump l.
A pressure control valve 14 is connected to the secondary port A of the servo valve IO and the bipedal pilot line 8 in response to the differential pressure before and after the throttles 7 and 11, and the discharge pressure of the discharge line 6 or Equipped with an electronic controller 17 that outputs a control signal to the servo valve lO according to the deviation between the set value and the detected value regarding the discharge amount, the pressure on the downstream side of the throttle 11 is guided to the spring chamber, and the inlet port is It is characterized by comprising a surge absorption valve I8 connected to the discharge line 6. Further, the second electronically controlled pump of the present invention is formed by adding an oil chamber 19 provided in communication with the spring chamber of the surge absorption valve I8 to the components of the first electronically controlled pump I.

Function> It is assumed that, for example, a hydraulic cylinder 21 is connected to the discharge line 6 of the first electronically controlled pump of the present invention and is driven. For example, when the hydraulic cylinder 21 reaches its stroke end and the control is automatically switched from large flow rate control to pressure control, a large surge pressure is generated in the discharge line 6. At this time, the servo valve 10 is switched to connect its secondary port A to the pilot line 8 branched from the discharge line 6 by a control signal output from the electronic controller 17 in conjunction with the above control change, Pressure control valve 1・
1 has been switched to a steady state position in which the secondary port A communicating with the cylinder 5 of the variable displacement pump 1 is connected to the secondary port A of the servo valve IO. Therefore, the pressure oil in the discharge line 6 is transferred to the pilot line 8. Servo valve 10. The oil flows into the cylinder 5 of the variable displacement pump 1 through the pressure control valve 14, tilts the swash plate 2 in the neutral direction, and makes the oil discharged from the pump 1 high pressure and small flow rate. As a result, a pressure difference is generated before and after the calibration 7 of the pilot line 8. Then, the surge absorption valve 18, which is connected to the inlet port on the upstream side of the throttle 7, that is, the discharge line 6, and to the spring chamber on the downstream side of the throttle 7, opens in response to the differential pressure, and the surge absorption valve 18 is opened in response to the differential pressure. The surge pressure is transferred to tank 22.
escape to

In this way, if the safety valve 13 connected to the piping line 8 does not open, the surge absorption valve 18 opens and the surge pressure generated in the discharge line 6 is greatly alleviated.

When the hydraulic cylinder 2I is driven by the second electronically controlled pump 1 of the present invention in the same manner as described above, a large surge pressure is also generated in the discharge line 6. At this time, the servo valve lO and the pressure control valve 14 operate in the same manner as described above, and the swash plate 2 is tilted toward the neutral direction due to the inflow of pressure oil into the cylinder 5 of the pump 1, and the above pressure passing through the pilot line 8 is The throttle 7 of the pilot line 8 is caused by the inflow of oil and the inflow of pressure oil into the oil chamber 19.
゜l! A differential pressure occurs before and after. Then, the surge absorption valve 18 opens in response to this differential pressure, and the surge pressure generated in the discharge line 6 is released to the tank 22, and the surge pressure is significantly alleviated.

<Example> Hereinafter, the present invention will be explained in detail with reference to illustrated embodiments.

FIG. 1 is a circuit diagram showing an example of a second electronically controlled pump of the present invention, and this electronically controlled pump consists of a bias spring 3 and a bias cylinder 4 for tilting the swash plate 2 in the direction of the maximum inclination angle, and the swash plate 2. A variable displacement pump l has a servo cylinder 5 that tilts the pump in the neutral direction, a pilot line 8 (P port) whose secondary port A is branched from the discharge line 6 of the pump 1 and has a throttle 7, and a tank 9 (T
a servo valve 10 which is switchably connected to
A safety valve 13 is connected to the pilot line 8 on the downstream side of the servo valve 13 through a line I2 having a throttle 11, and a secondary port A communicating with the servo ring 5 of the pump 1 is connected to the servo valve! 0 secondary port A (T port) and the pilot line 8 (P port) on the downstream side of the throttle 7.
A pressure control valve 14 is provided which is switched and connected in response to the differential pressure between the front and rear (control ports x, y) of the pressure control valve 11.

Further, the electronically controlled pump includes a drop pressure sensor 15 that detects the pressure of the discharge line 6, a swash plate angle sensor 16 that detects the inclination angle of the swash plate 2, that is, the discharge amount, and these sensors l5.
．． An electronic controller 17 outputs a control signal to the servo valve 10 according to the deviation between the detection value inputted from the servo valve 16 and the set value of the discharge pressure and discharge amount manually inputted in advance. The chamber (control port Y) is aperture 11
surge absorption valves 1 respectively connected to lines 12 on the downstream side of the
8, an oil chamber 19 provided so as to communicate with the spring chamber of this surge absorption valve 18, and a secondary port A of the pressure control valve 14 between the secondary port of the servo valve 10 and the secondary port A of the pressure control valve 14. A check valve 20 is provided to prevent the flow to direct sound.

The opening differential pressure of the surge absorption valve I8 is created by pressure oil flowing into the servo cylinder 5 from the discharge line 6 through the servo valve 10, the pressure control valve 14, and the check valve 20 located at the symbol position on the right in FIG. The differential pressure generated before and after the throttle 7.11 due to pressure oil flowing from the discharge line 6 to the oil chamber 19 via the line 12, or the effective sum of the above two differential pressures is set. , is higher than the opening differential pressure of the pressure control valve 14.

The operation of the electronically controlled pump having the above configuration will be described next.

A hydraulic cylinder 21 is connected to the discharge line 6 of the electronically controlled pump and is driven. Now, when the hydraulic linter 21 reaches its stroke end and switches from large flow rate control to pressure control, a large surge pressure is generated in the discharge line 6. At this time, the servo valve IO connects its secondary port A to the pilot line 8 (■) port branched from the discharge line 6 by the control signal output from the electronic controller 17 in conjunction with the above control change. The pressure control valve 14 connects the secondary port communicating with the servo cylinder 5 of the pump I to the secondary port A (T port) of the servo valve IO. position, ie, the steady state position. Therefore, the pressure oil in the discharge line 6 having surge pressure is
．． It flows into the servo cylinder 5 of the pump 1 through the pressure control valve 14 and the check valve 20, and tilts the swash plate 2 in the neutral direction. Further, the pressure oil in the discharge line 6, which has the above-mentioned surge pressure, flows into the oil chamber I9 via the line 12. Therefore, a predetermined pressure difference is generated before and after the throttle 7 of the pilot line 8 and the throttle 11 of the line 12 due to the pressure oil flowing into the servo cylinder 5 and the oil chamber 19 from the discharge line 6, and the surge absorption valve 18 suppresses the pressure difference. Internal pilot bow 1-X
and the external pilot port Y, and the Zahn pressure generated in the discharge line 6 is released to the tank 22 and is significantly relieved.

As described above, in the present invention, the surge absorption valve 18, which was conventionally thought to be able to be opened only by the differential pressure across the throttle caused by the vent flow accompanying the opening of the safety valve I3, is now opened by the servo cylinder 5 via the servo valve lO and the pressure control valve 14. The pilot line 8 is throttled by the pressure oil flowing into the oil chamber 19 or the pressure oil flowing into the oil chamber 19, or in addition to this, the pressure difference generated before and after the throttle 11 of the line 12 causes the opening side to be opened. By using a combat electronically controlled pump with a built-in surge absorption valve 18, the surno pressure in the discharge line 6 can be significantly reduced without requiring the trouble of installing piping, etc., which is required when installing an external pump.

In the above embodiment, the pilot line 8 on the downstream side of the throttle 7
A line 12 is branched from the line 12, and a throttle 11 is interposed therein, and the downstream side of the throttle 11 is connected to an oil chamber 19 and a surge absorption valve 18.
Since the valves are connected to the external pilot ports Y, the differential pressure across the throttle 11 caused by the pressure oil flowing into the oil chamber 19 can be applied to the surge absorption valve 18, and the surge pressure absorption capacity is improved accordingly. do.

In the above embodiment, the case where both the surge absorption valve 18 and the oil chamber I9 are provided has been described, but the oil chamber 19 is omitted and the discharge line 6 is connected to the servo valve 10 and the pressure control valve 14.
The surge absorption valve 18 can be opened only by the differential pressure across the throttle 7 caused by the pressure oil flowing into the servo cylinder 5 through the servo cylinder 5.

It goes without saying that the present invention is not limited to the two-legged embodiment.

<Effects of the Invention> As is clear from the above description, the electronically controlled pump of the present invention is equipped with a safety valve and allows pressure oil from the pilot line, which has a restriction branching from the discharge line of the variable displacement pump, to be supplied from the electronic controller. discharge pressure.

It is supplied to the swash plate tilting cylinder of the pump through a servo valve operated by a discharge amount control deviation signal and a pressure control valve that responds to the differential pressure across the throttle.

In the discharge line, the inlet port is connected to the above discharge line,
Since the spring chamber is equipped with a surge absorption valve connected to the downstream side of each of the above-mentioned throttles, and is further equipped with an oil chamber that is connected to the above-mentioned spring chamber, a surge pressure smaller than the crab king pressure of the safety valve is discharged. Even if surge pressure is generated in the surge absorption line, the surge absorption valve can be opened by the differential pressure generated before and after the throttle due to the pressure oil flowing from this discharge line into the swash plate tilting nolinder and the oil chamber as described above, and the surge pressure can be significantly reduced. I can do it.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an example of the second electronically controlled pump of the present invention. l...Variable displacement pump, 2...Swash plate, butt...Surho ring, 6...Discharge line, 7.11...Aperture, 8
・・Pilot line, 10 ・Surho valve, I3・・Safety valve, 14 Pressure control valve, 17・・Electronic controller, I8
・Surge absorption valve, 19・Oil chamber.

Claims (2)

[Claims] (1) A variable displacement pump (1) having a cylinder (5) for tilting the swash plate (2), and a secondary port (A) branched from the discharge line (6) of the variable displacement pump (1). A pilot line (8) with a restriction (7) and a tank (
9) and a servo valve (10) which is switchably connected to the above-mentioned throttle (
A safety valve (13) connected to the pilot line (8) on the downstream side of the servo valve (10) and a secondary port (A) communicating with the cylinder (5) of the variable displacement pump (1) )'s secondary port (A) and the above pilot line (
8) and a pressure control valve (14) which is switched and connected in response to the differential pressure before and after the throttle (7, 11), and the discharge line (
6) in an electronically controlled pump equipped with an electronic controller (17) that outputs a control signal to the servo valve (10) in accordance with a deviation between a set value and a detected value regarding the discharge pressure or discharge amount; An electronically controlled pump characterized in that it is equipped with a surge absorption valve (18) whose downstream pressure is guided into a spring chamber and whose inlet port is connected to the discharge line (6). (2) A variable displacement pump (1) having a cylinder (5) that tilts the swash plate (2), and a secondary port (A) branched from the discharge line (6) of the variable displacement pump (1). A servo valve (10) switchably connected to the pilot line (8) and the tank (9), a safety valve (13) connected to the pilot line (8) via a throttle (11), and the variable displacement pump. The secondary port (A) communicating with the cylinder (5) of (1) is connected to the secondary port (A) of the servo valve (10) and the pilot line (8).
1) Pressure control valve (
14), and an electronic controller (17) that outputs a control signal to the servo valve (10) according to the deviation between the set value and the detected value regarding the discharge pressure or discharge amount of the discharge line (6).
An electronically controlled pump equipped with a surge absorption valve (18) in which the pressure downstream of the throttle (11) is guided to a spring chamber and whose inlet port is connected to the discharge line (6); (18) An electronically controlled pump characterized by comprising an oil chamber (19) provided to communicate with the spring chamber.