JPH0240870B2 - YUATSUKUDOGATAPISUTONHONPU - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention reciprocates pump pistons in a pair of pump cylinders in opposite directions by operating a pair of pump-driving hydraulic cylinders to suck in a fluid such as concrete. This invention relates to a hydraulically driven piston pump such as a concrete pump that pumps concrete.

Generally, such piston pumps supply pressurized oil generated from a high-pressure hydraulic source such as a hydraulic pump to a pair of pump-driving hydraulic cylinders by alternating the flow direction by switching the pump-driving switching valve. The hydraulic cylinder is then operated in a reciprocating manner. The pump cylinder is reciprocated as the hydraulic cylinder operates, and the fluid such as concrete that is sucked in and discharged by the pump cylinder is transferred to the piston pump's discharge through a valve that is switched in conjunction with the operation of the pump driving hydraulic cylinder. It is designed to be pumped through a pipe.

By the way, in such a piston pump, if the piston pump is temporarily stopped during its operation, the piston pump may reverse due to the load. For example, in a concrete pump that handles a heavy fluid such as concrete, if there is a pause during pumping of concrete, the weight of the concrete being pumped will be added to the pump piston in the pump cylinder, causing the pump connected to this to stop pumping. The hydraulic oil in the drive hydraulic cylinder may flow backwards, causing the piston pump to rotate in reverse. If such a reverse rotation of the pump occurs, there is a risk that the pump piston will collide with the end wall of the pump cylinder and be damaged, and furthermore, there is a risk that the hydraulic equipment, piping system, etc. will be damaged. Therefore, in order to prevent such reverse rotation of the pump, a three-position switching valve is used as the pump drive switching valve, in which the port connected to the hydraulic cylinder is closed in the neutral position, and when the pump is temporarily stopped, , the switching valve is switched to the neutral position to lock the pump driving hydraulic cylinder.

In addition, in order to automatically switch the pump drive switching valve in conjunction with valve switching and continuously drive the piston pump, the switching valve is usually a pilot-operated switching valve. However, in such a device, when driving a piston pump that is in a stopped state, it is necessary to generate pilot oil pressure to switch the switching valve to the operating position. In order to generate the pilot oil pressure from a hydraulic pump, which is a high-pressure oil source, it is desirable to be able to shut off the oil passage from the hydraulic pump to the pump driving hydraulic cylinder.

For this reason, as a pump drive switching valve, all ports are closed in the neutral position.
It is considered optimal to use a position switching valve.

By the way, using the 3-position switching valve as described above,
In order to switch the flow direction of the hydraulic oil supplied from the hydraulic pump to the pump driving hydraulic cylinder, conventionally, the three-position switching valve is switched from one side to the neutral position to the other side at once at the end of the switching operation of the valve. As a result, the time from when the switching operation of the valve ends until the three-position switching valve actually completes switching inevitably becomes long, resulting in the following problems. That is, from the end of the switching operation of the valve until the 3-position switching valve actually completes switching, the valve is stopped and the hydraulic cylinder for driving the pump is not activated yet. A large amount of hydraulic fluid discharged from the hydraulic pump is left in a state where it has no place to go, and if this state continues for a long time, high surge pressure will occur in the hydraulic circuit connected to the hydraulic pump, and the relief in the circuit will be removed. The valve also opens, causing loud noise and reducing the durability of the hydraulic pump.

The present invention was proposed in view of the above, and uses a three-position switching valve as a switching valve for driving the pump in a hydraulically operated piston pump as described above, and when the valve is switched, surge pressure in the circuit is generated. An object of the present invention is to provide a piston pump that can minimize the rise in

In order to achieve this purpose, the present invention
A pair of pump cylinders arranged in parallel to suck in and discharge fluid; A pair of pump driving hydraulic cylinders to reciprocate each pump piston of the pump cylinder; and each pump piston to reciprocate in opposite directions. The flow direction of the pressure oil supplied from the high-pressure oil source to the pair of pump driving hydraulic cylinders is alternately switched by the pilot oil pressure, and when the pilot oil pressure is not applied, the neutral position is where the flow of the pressure oil is cut off. a pilot-operated switching valve for driving the pump that automatically returns to the position; a reciprocating valve that alternately communicates the discharge sides of the pair of pump cylinders with the discharge pipe of the piston pump; a hydraulic cylinder for driving the valve that drives the valve reciprocally; ; a valve driving switching valve that switches the flow direction of pressure oil supplied from a high-pressure hydraulic source to the valve driving hydraulic cylinder; and a pair of communicating oil between the valve driving switching valve and the valve driving hydraulic cylinder. a pair of pilot oil passages each branching from the pilot oil passageway and connected to the pilot oil chamber of the pump drive switching valve; a pair of check valves that allow only the flow of oil; and a pair of check valves that automatically return the pump driving switching valve to the neutral position during switching operation of the valve driving hydraulic cylinder and return to the neutral position at the end of the switching operation. In order to move the check valves from one to the next switching position, one of the pair of check valves is held open in response to the hydraulic pressure during the switching operation of the valve drive hydraulic cylinder, and the other is held open. It is characterized in that the valve is opened in conjunction with the driving piston at the end of the switching operation of the valve driving hydraulic cylinder.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In FIG. 1, at the base ends of a pair of parallel pump cylinders 1 and 1', there are first and second pump driving hydraulic cylinders 2. , 2' are arranged in series. Pump pistons 3, 3' that slide into each pump cylinder 1, 1' and drive pistons 4, 4' that slide into each hydraulic cylinder 2, 2' are integrally connected by connecting rods 5, 5', respectively. is connected to. The drive pistons 4, 4' are connected to each hydraulic cylinder 2,
2' is divided into base chambers a, a' and tip chambers b, b'.

At the tip of each hydraulic cylinder 2, 2', a control valve 6, 6' is provided, respectively, which is activated when the drive piston 4, 4' reaches the tip. Each control valve 6, 6' has an inlet port 7,
7' and the outlet ports 8, 8', the valve rods 9, 9'
project into the tip chambers b, b' of the hydraulic cylinders 2, 2'. Each control valve 6, 6' has a drive piston 4,
4' is opened when it comes into contact with the valve rods 9, 9', and closed when the drive pistons 4, 4' are moved away.

A common valve chamber 10 is provided at the tip of each pump cylinder 1, 1' across them, and a discharge pipe 11 of a piston pump is connected to the center of this valve chamber 10. A valve 12 is slidably fitted in the valve chamber 10, and this valve 12 is connected to driving pistons 14, 14' of valve driving hydraulic cylinders 13, 13' connected to both ends of the valve chamber 10, and connected to a connecting rod. They are integrally connected by 15 and 15'. Each hydraulic cylinder 13,1
Oil chambers c and c' partitioned by drive pistons 14 and 14' are formed at the tip of the piston 3', respectively, and hydraulic oil is alternately supplied to these oil chambers c and c'. As a result, the drive pistons 14, 14' are reciprocated. This hydraulic cylinder 1
3 and 13', the valve 12 is reciprocated, thereby alternately communicating the discharge side of the pump cylinder 1 and the discharge pipe 11, or the discharge side of the pump cylinder 1' and the discharge pipe 11, respectively.

A pair of check valves 16, 16' is provided at the tip of each hydraulic cylinder 13, 13', and these valves 16, 16', as described later,
One of them is the valve driving hydraulic cylinder 13,
During the switching operation of the valve driving hydraulic cylinder 13, 13', the valve is held open in response to the hydraulic pressure, and the other hydraulic cylinder 13, 13' is interlocked with the driving piston 14, 14' at the end of the switching operation of the valve driving hydraulic cylinder 13, 13'. The valve is configured to open when the valve is opened. Each check valve 16,
16' each have one inlet port 17,1
7' and two outlet ports 18, 18' and 19,
19', and its spools 20,2
By the movement of 0', the inflow port 17, 17' communicates with either the outflow port 18, 18' or 19, 19', and the outflow port 18, 18' or 19, 19' and the other side is now cut off.

A high-pressure oil passage 21 connected to the discharge side of the hydraulic pump P, which is a high-pressure oil source, is branched into branch high-pressure oil passages 22 and 23, and one of the branch high-pressure oil passages 22 is a pilot-operated three-position switching valve. Connected to one pump drive switching valve 24 and connected to the other branch high pressure oil line 23
is connected to a valve driving switching valve 25 which is also a pilot-operated two-position switching valve. Further, the hydraulic oil discharged through these switching valves 24 and 25 is returned to the oil tank T via a return oil passage 26. Pump drive switching valve 24
Other oil passages 27, 27' coming out from the other side are connected to respective tip chambers b, b' of the pump driving hydraulic cylinders 2, 2', and coming out from the other side of the valve driving switching valve 25. Another oil passage, namely the communicating oil passage 28, 28'
are valve driving hydraulic cylinders 13 and 1, respectively.
3' are connected to each oil chamber c, c'.

The base chambers a, a' of the respective hydraulic cylinders 2, 2' communicate with each other through a connecting oil passage 29, and pressure oil is introduced into the tip chamber b of the hydraulic cylinder 2, causing the drive piston 4 to move toward the base side. At this time, the hydraulic oil in the base chamber a flows into the base chamber a' of the hydraulic cylinder 2' through the connecting oil passage 29, and presses and moves the drive piston 4' toward the tip side. At this time,
The hydraulic oil in the front chamber b' of the hydraulic cylinder 2' is discharged through the oil passage 27'. Similarly, when the drive piston 4' moves toward the base side, the hydraulic oil in the base chamber a' is sent to the base chamber a through the connecting oil passage 29, and the drive piston 4 is pushed toward the front side. The hydraulic oil in the tip chamber b is discharged through the oil passage 27.

Near the pump drive switching valve 24 and the valve drive switching valve 25, there is a first valve that switches between them.
and second solenoid valves 30 and 31 are provided, respectively, and pilot oil passages 32 and 3 are connected to two ports on one side of the first solenoid valve 30.
2' applies pilot oil pressure to the left and right pilot oil chambers of the pump drive switching valve 24, and the pilot oil passages 33 and 33' connected to the two ports on one side of the second solenoid valve 31 control the valve drive switching valve. Pilot oil pressure is applied to the left and right pilot oil chambers of 25. These first and second
The solenoid valves 30 and 31 are two-position switching valves in which the right position in the figure is a normal rotation position and the left position is a reverse rotation position.

The two ports on the other side of the first solenoid valve 30 are connected to each of the check valves 16, 16' provided at the tips of the valve driving hydraulic cylinders 13, 13' via pilot oil passages 34, 34'. Inflow side port 1
7 and 17', respectively. One outlet port 18, 1 of this check valve 16, 16'
8' is communicated with oil passages 28' and 28 through pilot oil passages 35 and 35', respectively. Also,
The other outlet port 19 of the check valves 16, 16',
19' is communicated with each oil chamber c, c' of the hydraulic cylinders 13, 13' through pilot oil passages 36, 36', respectively. On the other hand, the second solenoid valve 31
The two ports on the other side are the pilot oil passage 37,
37', the control valves 6, 6' are connected to inlet ports 7, 7', respectively. The outflow side port 8 of the control valve 6 is connected to the tip chamber b' of the second hydraulic cylinder 2' by the pilot oil passage 38, and
The outflow side port 8' of the control valve 6' is connected to the pilot oil passage 3.
8' communicate with the tip chamber b of the first hydraulic cylinder 2, respectively.

A relief valve 39 is provided between the high pressure oil passage 21 and the return oil passage 26, and this relief valve 39
When the oil pressure in the high pressure oil passage 21 becomes higher than the set pressure, the pressure oil in the oil passage 21 is recirculated,
The oil pressure is maintained at a set pressure.

When the pump drive switching valve 24 is in its neutral position, communication between the oil passages 22, 26, 27, and 27' is cut off, and no pilot oil pressure is applied to the pilot oil chambers on either side of the valve. At times, it is returned to the neutral position and held there by pressure springs 40, 40' provided on both sides.

Since the configurations of the check valves 16 and 16' are exactly the same, we will take up the check valve 16 here and explain one example of its specific structure.As shown in FIGS. The stop valve 16 is connected to the hydraulic cylinder 1
3 and a valve hole 41 provided at the tip of the valve hole 4.
1 and a spool 20 that slides into the spool 20.

The valve hole 41 has one end open to the oil chamber c of the hydraulic cylinder 13, a first large diameter hole 42 connected to the opening, and a first small diameter hole 4 connected to the large diameter hole 42.
3. A second large-diameter hole 44 continuous to this small-diameter hole 43 and a second small-diameter hole 45 continuous to this are provided in this order. On the other hand, the spool 20 has a first small diameter part 47, a second large diameter part 48, and a second small diameter part 49 in this order from the first large diameter part 46 on the side of the oil chamber c. Spool 2
The first large diameter portion 46 at one end of the valve hole 4 has an outer diameter that is
Slightly larger than the inner diameter of the first small diameter hole 43 of No. 1,
Its length is equal to or slightly longer than the length of the first large diameter hole 42 of the valve hole 41. Also,
The outer diameter of the first small diameter portion 47 of the spool 20 is the same as that of the valve hole 41.
The inner diameter of the first small diameter hole 43 is smaller than the inner diameter of the first small diameter hole 43, and the length thereof is larger than the length of the first small diameter hole 43. Further, the outer diameter of the second large diameter portion 48 of the spool 20 is larger than the inner diameter of the first small diameter hole 43 of the valve hole 41 and smaller than the inner diameter of the second large diameter portion 44 . The second small diameter portion 49 at the rear end of the spool 20 is connected to the valve hole 4.
1, and the rear end surface of the spool 20 allows the second small diameter hole 4
An oil chamber d is defined within 5. The spool 20 has this oil chamber d and a hydraulic cylinder 13.
A longitudinal through hole 50 is provided that communicates with the oil chamber c.

Further, a valve hole 41 is provided in the wall of the hydraulic cylinder 13.
A port 51 connected to the first large diameter hole 42, a port 17 connected to the first small diameter hole 43, and a second large diameter hole 44.
A port 18 connected to is provided. The communicating oil passage 28 and the pilot oil passages 34 and 35 shown in FIG. 1 are connected to these ports 51, 17 and 18, respectively. Therefore, the first large diameter hole 42 and the first
The oil passage 52 formed between the large diameter portion 46 and the oil chamber c
In the communication oil passage 28, the oil passage 53 formed between the first small diameter hole 43 and the first small diameter part 47 is connected to the pilot oil passage 34, and the second large diameter hole 44 and the second large diameter part 48. The oil passages 54 formed between the second small diameter portion 49 and the second small diameter portion 49 communicate with the pilot oil passage 35, respectively.

Thus, when pressure oil is introduced from the port 18 through the pilot oil passage 35, the second large diameter portion 48 is pushed leftward in the figure by the oil pressure, and the second large diameter hole 44 is opened as shown in FIG. It abuts against the step portion 55 at the left end. As a result, the oil passage 54 and the oil passage 53 are completely cut off. At this time, the stepped portion 56 formed between the first large diameter portion 46 and the first small diameter portion 47 of the spool 20 is sufficiently separated from the stepped portion 57 at the right end of the first large diameter hole 42, and the oil path 52 and 53 are communicated with each other. Therefore, the pressure oil from the pilot oil passage 35 does not flow into the pilot oil passage 34. The pilot oil passage 34 communicates with the oil chamber c of the hydraulic cylinder 13 and the communication oil passage 28.

At this time, the spool 20 is at the most advanced position to the left, and its left end protrudes into the oil chamber c. Therefore, when the drive piston 14 (FIG. 1) of the hydraulic cylinder 13 approaches the tip, the drive piston 14 and the spool 20 first come into contact. As the drive piston 14 moves, the spool 20 is pushed rightward and retreats. When the drive piston 14 reaches its travel limit position,
Stepped portion 56 at the rear end of the first large diameter portion 46 of the spool 20
as shown in FIG. 3, contacts the stepped portion 57 of the valve hole 41 and blocks the oil passages 52 and 53. on the other hand,
The second large diameter portion 48 is separated from the stepped portion 55 and allows the oil passages 53 and 54 to communicate with each other. As a result, the pressure oil introduced from the pilot oil passage 35 is guided from the port 17 to the pilot oil passage 34.

Next, when pressure oil is introduced from the port 51 through the communication oil passage 28, the pressure oil flows into the hydraulic cylinder 1.
3 enters the oil chamber c and presses the drive piston 14, so the drive piston 14 separates from the spool 20, but since the oil pressure is also applied to the left end surface of the spool 20, the spool 20 is in the position shown in Figure 3. Retained. At this time, the pressure oil enters the oil chamber d in the second small diameter hole 45 through the through hole 50 and applies a leftward force to the spool 20, but the pressure receiving area on the left side of the spool 20 is larger than the pressure receiving area on the right side. Since it is large, the spool 20 will not move to the left. In this state, the pressure oil in the oil chamber c of the hydraulic cylinder 13 does not flow into the pilot oil path 34. The pilot oil passage 34 communicates with a pilot oil passage 35.

When the spool 20 is in the state shown in Fig. 2, if the oil pressure in the communicating oil passage 28 or the oil chamber c rises for some reason, the pressure receiving area of the spool 20 that receives the oil pressure from the left side is larger than the pressure receiving area from the right side. Since it is large, the spool 20 rapidly retreats to the right, resulting in the state shown in FIG. Therefore, large oil pressure in the communicating oil passage 28 or the oil chamber c is not transmitted to the pilot oil passage 34.

As described above, this check valve 16 is a pilot operated check valve that opens and closes between the pilot oil passage 34 and the pilot oil passage 35, and a pilot operated type check valve that opens and closes between the pilot oil passage 34 and the pilot oil passage 35.
4 and the oil chamber c. In this embodiment, in order to ensure this valve operation, the spool 20 is
A pressure spring 58 is provided between the valve hole 41 and the valve hole 41 to always urge the spool 20 in the backward direction. Further, the first small diameter part 47 and the second large diameter part 48 of the spool 20 are connected by a conical part 59 so that the outer surface of the conical part 59 comes into contact with the corner of the stepped part 55 of the valve hole 41. Thus, communication and interruption between the oil passages 53 and 54 is ensured. The oil chamber d communicating with the oil chamber c is for smooth movement of the spool 20.

Note that by making the outer diameter of the first large diameter portion 46 of the spool 20 equal to the inner diameter of the first small diameter hole 43 of the valve hole 41 and sliding them together at the most retracted position of the spool 20, the oil passage 52 It is also possible to cut off the connection between and 53. Alternatively, instead of communicating with the oil chamber c via the oil passage 52, the port 51 to which the communication oil passage 28 is connected may be opened in the end wall surface of the hydraulic cylinder 13 and communicated directly with the oil chamber c. good.

In this control valve 16, the oil passage 52 is
It will be obvious that this corresponds to the pilot oil passage 36 shown in the figure and the outlet port 19 to which it is connected.

Next, to explain the operation of the above-mentioned piston pump, referring again to FIG. Suppose it is in the left position. When the hydraulic pump P is not being driven, no pilot oil pressure is being generated, so the pump driving switching valve 24 is held at the neutral position by the pressure springs 40, 40' on both sides thereof.

When the hydraulic pump P is driven in this state, the pressure oil discharged from the hydraulic pump P passes through the high pressure oil passage 21 and branch high pressure oil passages 22 and 23 to the pump drive switching valve 24 and the valve drive switching valve 25, respectively. be guided. Pump drive switching valve 24 in neutral position
Since each oil passage leading to this is blocked, the oil pressure in the branch high pressure oil passage 22 increases, and this oil pressure is transmitted to the branch pressure oil passage 23. Pressure oil led from the branch high-pressure oil passage 23 to the valve driving switching valve 25 flows from the switching valve 25 through the communicating oil passage 28' into the oil chamber c' of the valve driving hydraulic cylinder 13'. The outflow side port 18 of the check valve 16 is connected to the outflow side port 18 of the check valve 16 through the pilot oil passage 35 branching from the communication oil passage 28'.
guided by. In the check valve 16, the port 18
Since the spool 20 is moved to the forward position as shown in FIG. 2 by the pressure oil flowing in from the spool 20, the flow of the pressure oil is interrupted.

The pressure oil flowing into the oil chamber c' of the hydraulic cylinder 13' presses the driving piston 14', and moves the valve 12, which is integrally connected by the connecting rod 15', in the direction shown by the arrow in FIG. let Valve 1
The movement of the piston 2 is stopped when the drive piston 14 connected thereto via the connecting rod 15 comes into contact with the tip wall of the hydraulic cylinder 13. In this position, the valve 12 completely connects the delivery side of the pump cylinder 1' to the delivery pipe 11 of the piston pump. During this period, the hydraulic oil in the oil chamber c of the hydraulic cylinder 13 flows through the communication oil passage 28, the switching valve 25,
The oil is returned to the oil tank T via the return oil path 26.

At the end of the operation of the hydraulic cylinders 13, 13' in this direction, the drive piston 14 abuts against the spool 20 of the check valve 16 and presses it into the position shown in FIG. As a result, the pilot oil passage 35 and the pilot oil passage 34 communicate with each other, and the pressure oil in the communication oil passage 28' passes through the pilot oil passage 35, the check valve 16, and the pilot oil passage 34, and then enters the first solenoid valve. Guided by 30. This pressure oil is further led to the pilot oil passage 32' through the first solenoid valve 30 located at the right position, and flows into the pilot oil chamber on the right side of the pump drive switching valve 24. In this way, the pilot oil pressure is applied to the switching valve 24 from the right side, so that the switching valve 24 is switched to the right position. During this time, the check valve 16' is closed to the hydraulic cylinder 1.
Since the oil pressure in the oil chamber c' of 3' is in the state shown in Fig. 3, the inlet side port 17' and the outlet side port 1
8', and the hydraulic oil in the pilot oil chamber on the left side of the switching valve 24 is connected to the pilot oil passage 32, the first solenoid valve 30, the pilot oil passage 34', the check valve 16', and the pilot oil chamber on the left side of the switching valve 24. It is discharged to the communication oil passage 28 via 35'.

When the pump drive switching valve 24 is switched to the right position, pressure oil from the hydraulic pump P flows into the tip chamber b of the first hydraulic cylinder 2 through the branch high pressure oil passage 22, the switching valve 24, and the oil passage 27. do. In this way, the drive piston 4 is retracted by the hydraulic pressure in the front chamber b, and the pump piston 3, which is coupled to the drive piston 4 by the connecting rod 5, is retracted. At the same time, the hydraulic oil in the base chamber a of the first hydraulic cylinder 2 is transferred to the second hydraulic cylinder 2' through the connecting oil passage 29.
into the base chamber a' of the engine to advance its driving piston 4'. Therefore, this driving piston 4'
The pump piston 3', which is integrally connected to the pump piston 3', also moves forward. The hydraulic oil in the tip chamber b' of the second hydraulic cylinder 2' is distributed through the oil passage 27', the switching valve 24, and the return oil passage 2.
6, it is refluxed to the oil tank T.

At this time, the pump cylinder 1, in which the pump piston 3 is retracted, is in the suction process and sucks a fluid such as concrete from a hopper (not shown) or the like. On the other hand, the pump cylinder 1', in which the pump piston 3' moves forward, is in the discharge process, and discharges the fluid sucked into the interior, and pumps it out from the discharge pipe 11 through the hole of the valve 12.

When the driving piston 4' moves forward and reaches the tip of the second hydraulic cylinder 2', the valve rod 9' of the control valve 6' is pressed thereby, the control valve 6' opens, and the outlet port 8 is opened. ' to the inflow side port 7' is communicated. As a result, a part of the pressure oil that has flowed into the tip chamber b of the first hydraulic cylinder 2 flows into the pilot oil passage 3.
8', the control valve 6', the pilot oil passage 37', the second solenoid valve 31, and the pilot oil passage 33'. In addition, this switching valve 25 is switched to the right position.

When the valve drive switching valve 25 is switched to the right position, the pressure oil in the branch high pressure oil passage 23 is transferred to the switching valve 2.
5 and the communication oil passage 28 into the oil chamber c of the valve driving hydraulic cylinder 13, and the oil pressure presses the driving piston 14 to move the valve 12 in the opposite direction of the arrow. At this time, the spool 20 of the check valve 16 does not move to follow the drive piston 14, but remains held at the position shown in FIG. communication is maintained. Furthermore, the communication oil passage 28' is connected to the return oil passage 26 by switching the switching valve 25 to the right position, so the pilot oil chamber on the right side of the pump drive switching valve 24 is connected to the pilot oil passage 32', the 1 solenoid valve 30, a pilot oil passage 34, a check valve 16, a pilot oil passage 35, and a communication oil passage 28'.

On the other hand, the oil chamber of the valve driving hydraulic cylinder 13'
c' communicates with the oil tank T through the communication oil passage 28', and pilot oil pressure is applied to the outflow side port 18' of the check valve 16' through the pilot oil passage 35', so that the check valve 16' is held in the state shown in FIG. 2, and the inflow side port 1 of the check valve 16' is
7' and the outflow side port 19', and the pilot oil chamber on the left side of the pump drive switching valve 24 is
It communicates with the oil tank T via a pilot oil passage 32, a first solenoid valve 30, a pilot oil passage 34', a check valve 16', a pilot oil passage 36', an oil chamber c', and a communication oil passage 28'. Therefore, since no pilot oil pressure is applied to the switching valve 24 from either side, the switching valve 24 automatically returns to the neutral position by the action of the pressure springs 40, 40'. That is, the valve drive switching valve 25 is switched and the valve 1
2 starts moving, the pump drive switching valve 24 is switched to the neutral position almost at the same time.

The valve 12 moves further, and the hydraulic cylinder 1
3, 13', the drive piston 1
4' presses the spool 20' of the check valve 16' to retract it. When the check valve 16' is in the state shown in Fig. 3,
The inlet port 17' and the outlet port 18' communicate with each other. As a result, the pressure oil in the communication oil passage 28 passes through the pilot oil passage 35', the check valve 16', the pilot oil passage 34', the first solenoid valve 30, and the pilot oil passage 32, and is then transferred to the pump drive switching valve. valve 2
It flows into the pilot oil chamber on the left side of No.4. On the other hand, since the check valve 16 is maintained as it is, the pilot oil chamber on the right side of the switching valve 24 is connected to the oil tank T.
is connected to. As a result, the switching valve 24 is switched from the neutral position to the left position. At this time, the valve 12 is in a position connecting the pump cylinder 1 to the discharge pipe 11.

When the pump drive switching valve 24 is switched to the left position, the pressure oil from the hydraulic pump P is transferred to the branch high pressure oil path 2.
2, flows into the tip chamber b' of the second hydraulic cylinder 2' through the switching valve 24 and the oil passage 27', retracts the driving piston 4', and transfers the hydraulic oil in the base chamber a' to the connecting oil passage. 29 into the base chamber a of the first hydraulic cylinder 2 to advance the drive piston 4. Therefore, since the pump piston 3' is moved backward while the pump piston 3' is moved forward, the pump cylinder 1' sucks in the fluid, and the pump cylinder 1 pumps out the fluid from the discharge pipe 11.

When the drive piston 4 approaches the tip of the first hydraulic cylinder 2, the control valve 6 opens, and the pressure oil in the tip chamber b' of the second hydraulic cylinder 2' flows through the pilot oil passage 38, the control valve 6, The oil is guided to the pilot oil passage 37, the second solenoid valve 31, and the pilot oil passage 33, and the valve drive switching valve 25 is switched to the left position again.

When the switching valve 25 is switched to the left position, the valve 12 is moved in the direction of the arrow by the pressure oil introduced into the oil chamber c' of the hydraulic cylinder 13' from the communication oil passage 28' through the branch high-pressure oil passage 23. start. At this time, the spool 20' of the check valve 16' is connected to the drive piston 1.
4', and the 3rd
Since the pilot oil passages 34' and 35' remain in the position shown in the figure, communication between the pilot oil passages 34' and 35' is maintained. Furthermore, the communication oil passage 28 is connected to the return oil passage 26 by switching the switching valve 25 to the left position, so the pilot oil chamber on the left side of the pump driving switching valve 24 is connected to the pilot oil passage 32, the first solenoid Valve 30, pilot oil passage 34', check valve 1
6', a pilot oil passage 35', a communication oil passage 28, a switching valve 25, and a return oil passage 26 to communicate with the oil tank T.

On the other hand, the oil chamber c of the valve driving hydraulic cylinder 13
is in communication with the oil tank T through the communication oil passage 28', and pilot oil pressure is applied to the outflow side port 18 of the check valve 16 through the pilot oil passage 35, so the check valve 16 is connected to the oil tank T as shown in FIG. The pilot oil chamber on the right side of the pump drive switching valve 24 is maintained in the state of the pilot oil passage 32', the first Solenoid valve 30, pilot oil passage 34, check valve 16, pilot oil passage 36, oil chamber
It communicates with the oil tank T via c' and the communication oil passage 28'.
Therefore, since no pilot oil pressure is applied to the switching valve 24 from either side, the switching valve 24
automatically returns to the neutral position by the action of the pressing springs 40, 40'. That is, when the valve driving switching valve 25 is switched and the valve 12 starts moving, the pump driving switching valve 24 is switched to the neutral position almost at the same time.

When the hydraulic cylinder 13' is further operated and the drive piston 14 of the hydraulic cylinder 13 reaches the tip,
The check valve 16 is switched to the state shown in FIG. switch to the right position. In this way, the driving pistons 4 of the pump driving hydraulic cylinders 2, 2' move back and the driving pistons 4' move forward again, causing the pump cylinder 1 to suck the fluid and pump cylinder 1'
The fluid is discharged by.

Thereafter, the above operation process is repeated.

In the above operating process, either the driving piston 14 or 14' of the valve driving hydraulic cylinder 13 or 13' is connected to the spool 20 or the spool 20 of the check valve 16 or 16'.
20', the pump drive switching valve 24 is held at the neutral position. In this neutral position, both the oil passages 27 and 27' are blocked, so the pump driving hydraulic cylinders 2 and 2' are both locked. Therefore, the pump piston 3, integrally connected to its drive piston 4, 4'
3' is fixed, reliably preventing the piston pump from reversing. Even if the hydraulic pump P is stopped while the driving pistons 14, 14' are in contact with the spools 20, 20', the hydraulic pressure in the pilot oil passages 35, 35' decreases, so the switching valve 24 It returns to the neutral position and prevents the piston pump from reversing.

When it becomes necessary to drive the piston pump in reverse to draw fluid from the discharge pipe 11,
It is sufficient to operate both the first and second solenoid valves 30 and 31 to switch them to the left position. Then, when the valve 12 connects the pump cylinder 1 and the discharge pipe 11, the pump piston 3 retreats, and when the valve 12 connects the pump cylinder 1' and the discharge pipe 11, the pump piston 3' retreats. Become.

In the above embodiment, valve driving hydraulic cylinders 13 and 1 are provided at both ends of the valve 12, respectively.
3', but it is also possible to use only one hydraulic cylinder 13 and replace the base chamber and tip chamber defined by the driving piston 14 with the oil chambers c and c' in the above-described embodiment. can. In that case,
The check valves 16, 16' are provided at the base end and the distal end of the hydraulic cylinder 13. Further, the valve chamber 10 itself can also be used as a hydraulic cylinder, and the valve 12 can be used as a driving piston.

In the switching operation process of the valve 12 in the embodiment of the present invention, one check valve 16, 16'
By keeping the valve in the open state (the state shown in FIG. 3), the pilot oil pressure of the pump drive switching valve 24 can be extinguished, and the switching valve 24 can be temporarily switched from one side to the neutral position. After that, when the valve 12 moves further and reaches the end of the switching operation,
The drive pistons 14, 14' of the valve drive hydraulic cylinders 13, 13' engage with the other check valve 16, 16' to open it, thereby moving the pump drive switching valve 24 from the neutral position. Since the switching operation of the switching valve 24 is divided into two parts, the switching operation of the switching valve 24 is divided into two parts, and as a result, the switching operation of the switching valve 24 is divided into two parts, and as a result, the switching operation of the switching valve 24 is divided into two parts. time, i.e. hydraulic pump P
The time during which a large amount of hydraulic fluid discharged from the pump is left with nowhere to go can be reduced by approximately half compared to the conventional example. Therefore, it is possible to prevent an excessive increase in surge pressure in the hydraulic circuit, which is caused by the above-mentioned condition continuing for a relatively long time as in the conventional example, and also to prevent the situation in which the relief valve 39 in the circuit is frequently opened. can be avoided as much as possible.

FIG. 4 compares the surge pressure generated in the hydraulic circuit connected to the discharge side of the hydraulic pump between the present invention and a conventional example. As is clear from this figure, in the present invention shown by the solid line, the switching valve 2 after the switching of the valve 12 is completed.
The spool movement time t of No. 4, that is, the time t from the end of the switching operation of the valve 12 to the time when the switching valve 24 actually completes switching, is approximately half of that of the conventional example shown by the two-dot chain line. The surge pressure according to the present invention is much lower.

As described above, according to the present invention, a pair of pump cylinders arranged in parallel that sucks in and discharges a fluid;
a pair of pump-driving hydraulic cylinders that reciprocate each pump piston of the pump cylinder; and a high-pressure hydraulic power source supplied to the pair of pump-driving hydraulic cylinders so as to reciprocate each pump piston in opposite directions. a pilot-operated pump drive switching valve that alternately switches the flow direction of the pressurized oil using a pilot oil pressure, and automatically returns to a neutral position where the flow of the pressure oil is cut off when the pilot oil pressure is not applied; A reciprocating valve that alternately communicates the discharge side of the pump cylinder with the discharge pipe of the piston pump; A valve driving hydraulic cylinder that drives this valve reciprocally; Pressure oil supplied to this valve driving hydraulic cylinder from a high-pressure hydraulic source. a valve driving switching valve that switches the flow direction of the valve; each branching from a pair of communicating oil passages between the valve driving switching valve and the valve driving hydraulic cylinder and connected to the pilot oil chamber of the pump driving switching valve; and a pair of check valves provided in the middle of each of the pilot oil passages to allow oil to flow in only one direction from the pilot oil chamber to the communicating oil passage side. In order to automatically return the pump driving switching valve to a neutral position during the switching operation of the valve driving hydraulic cylinder and to move it from the neutral position to the next switching position at the end of the switching operation, the pair of check valves is configured to: One of them is held open in response to the hydraulic pressure during the switching operation of the valve driving hydraulic cylinder, and the other is linked to the driving piston at the end of the switching operation of the valve driving hydraulic cylinder. Since the valve is configured to be opened, the pump driving switching valve can be moved to the neutral position in advance by using the switching operation time of the valve, and at the end of the switching operation of the valve, the pump driving switching valve is opened. Since it is sufficient to simply move the valve from the neutral position to the next switching position, the time from the end of the switching operation of the valve until the pump drive switching valve actually completes switching, that is, from the hydraulic source to The time during which a large amount of discharged hydraulic fluid is left in a state where it has no place to go can be approximately halved compared to the conventional example, and as a result, the above-mentioned state continues for a relatively long time as in the conventional example. It is possible to prevent an excessive rise in surge pressure in the hydraulic circuit, and to avoid the frequent opening of the relief valve in the same circuit as much as possible, which reduces the operating noise of the piston pump, reduces the load on the hydraulic source, and improves durability. It can contribute to sexual improvement.

[Brief explanation of drawings]

FIG. 1 is an overall schematic diagram showing an embodiment of a hydraulically driven piston pump according to the present invention, and FIGS. 2 and 3 are vertical sectional views of check valves used in the piston pump, each showing two different A diagram showing the location,
FIG. 4 is an explanatory diagram showing the effects of the present invention. 1, 1'... Pump cylinder, 2, 2'... Hydraulic cylinder for pump drive, 3, 3'... Pump piston, 4, 4'... Drive piston, 6, 6'... Control valve, 11... ...Discharge pipe, 12...Valve, 13,
13'... Valve drive hydraulic cylinder, 14,1
4'... Drive piston, 16, 16'... Check valve,
17, 17'... Inflow side port, 18, 18'; 1
9, 19... Outflow side port, 20, 20'... Spool, 24... Pump drive switching valve, 25...
Valve drive switching valve, 28, 28'... communicating oil passage,
32, 32'; 34, 34'; 35, 35'... Pilot oil path, P... Hydraulic pump, c, c'... Oil chamber.

Claims (1)

[Scope of Claims] 1. A pair of pump cylinders 1, 1' arranged in parallel to suck and discharge fluid; a pair of pump cylinders 1, 1' that reciprocate each pump piston 3, 3' of the pump cylinders 1, 1' Pump driving hydraulic cylinders 2, 2';
The flow direction of the pressure oil supplied from the high-pressure hydraulic source P to the pair of pump driving hydraulic cylinders 2, 2' is alternately controlled by pilot hydraulic pressure so as to reciprocate these pump pistons 3, 3' in opposite directions. a pilot-operated pump drive switching valve 24 that automatically returns to a neutral position to cut off the flow of pressure oil when pilot oil pressure is not applied; A reciprocating valve 12 that alternately communicates with the discharge pipe 11 of the piston pump; and a valve driving hydraulic cylinder 13, 1 that reciprocates the valve 12.
3'; this valve driving hydraulic cylinder 13, 1
3', a valve driving switching valve 25 that switches the flow direction of pressure oil supplied from the high pressure hydraulic source P; a pair of communication between these valve driving switching valves 25 and the valve driving hydraulic cylinders 13, 13'; Oil road 28,
A pair of pilot oil passages 32, 34', 3 branched from 28' and connected to a pair of pilot oil chambers of the pump drive switching valve 24, respectively.
5';32', 34, 35; each pilot oil passage 32, 34', 35'; It is provided with at least a pair of check valves 16, 16' that allow oil to flow in only one direction; The pair of check valves 16, 16' are set such that one of the check valves 16, 16' is activated when the hydraulic cylinders 13, 13' for driving the valve are activated to automatically return the valve to the next position, and at the end of the switching operation, the check valves 16, 16' are moved from the neutral position to the next switching position. The middle valve is held open in response to the working oil pressure, and the other valve is opened by communicating with the driving piston 14, 14' at the end of the switching operation of the valve driving hydraulic cylinder 13, 13'. A hydraulically driven piston pump characterized by being configured as follows. 2. The valve driving switching valve 25 is a pilot operated switching valve, and the pilot oil pressure is applied to the pair of pump driving hydraulic cylinders 2,
control valves 6, which alternately switch in conjunction with the operation of 2';
A hydraulically driven piston pump according to claim 1, comprising: 6'. 3. The check valves 16, 16' have spools 20, 20' with one end protruding into the oil chambers c, c' of the valve driving hydraulic cylinders 13, 13',
The spools 20, 20' are pressed by the drive pistons 14, 14' at the end of the switching operation of the valve driving hydraulic cylinders 13, 13', and the pilot oil passages 32', 34, 35;
2, 34', 35' are electrically connected to each other, the hydraulically driven piston pump according to claim 1.