JPH058003U - Hydraulic control circuit for directional valve - Google Patents

Abstract

(57) [Summary] [Purpose] To reduce the switching speed of the directional control valve when the actuator is stopped rather than when it is started, and when the actuator is suddenly switched by reversing the forward / reverse drive, Automatically increase the switching speed of the directional control valve and shorten the warm-up operation time. [Structure] Switching oil chamber connection ports 3a, 3b of slow-return valve-shaped flow control valves 1a, 1b which are fully opened when the pilot valves 12a, 12b supply pilot oil pressure to the switching oil chambers 4a, 4b of the directional control valve 4. Between the drain oil passages 6a and 6b, the pressure of the switching oil chamber connection port is increased by the pilot valve connection port 2
A normally closed valve 5a for pilot operation that opens when the pressure of a and 2b is slightly higher than the sum of the maximum return hydraulic pressure generated in the return side switching oil chamber by the neutral position return spring of the direction switching valve.
Slow return valves 7a and 7b are provided which connect 5b and delay the closing of the normally closed valve until the draining of the return side switching oil chamber by the opened normally closed valve is almost completed.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a hydraulic control circuit of a directional control valve that controls an actuating actuator of a movable member having a large inertia such as a power shovel.

[0002]

[Prior Art]

 Conventionally, in the middle of the oil passages on both sides of the switching oil chambers on both sides of the directional control valve equipped with the neutral position return spring and the pilot valves that supply and discharge pilot oil pressure to and from the switching oil chambers, respectively When the oil is supplied, the flow path is fully opened, and when the oil is discharged from the switching oil chamber, the flow rate control valve that restricts the flow path is inserted, and the spring return speed of the directional switching valve from the actuator drive position to the neutral position is inserted. Is controlled to be slower than the switching speed of the directional control valve from the neutral position to the actuator drive position to prevent the impact of the movable member driven by the actuator during a sudden stop at the time of a sudden stop. In the circuit, the forward and reverse drive of the boom cylinder of the power shovel is suddenly reversed and the bucket is supported by an arm at the tip of the boom to perform the pressure spreading work on the ground. When switching between the forward and reverse drive of the motor, the flow control valve should be provided with a switching oil chamber that can be fully opened by pilot hydraulic pressure to prevent the impact prevention. It is disclosed in Japanese Utility Model Application Laid-Open No. 1-163201 that the switching oil chambers are connected to the pilot valve connection ports of the flow control valves on the other side.

[0003]

[Problems to be solved by the device]

 According to this conventional technique, when warming up each actuator such as a power shovel at low temperatures in winter, the directional control valve is first kept in the neutral position and the hydraulic pump is operated under no load, so that the tank and the center bypass are bypassed. The oil temperature in the circuit is raised, and then the pilot valve is turned back on and suddenly operated forward and backward to move each actuator idly.However, between the pilot valve and the flow control valve that must be installed in the operator's cab. The oil passage is extremely long, and even if the pilot valve is turned back and forth and the forward / reverse operation is suddenly performed, the oil in the flow control valve only reciprocates in the oil passage and does not replace the oil in the tank. As the warm-up time for idling becomes longer, the driver may get tired and the life of each part of the hydraulic equipment may be shortened.

According to the present invention, when the hydraulic pump is operated without load in the neutral position of the directional control valve, the oil in the switching oil chamber of the directional control valve is heated by heat conduction from the oil passing through the center bypass circuit. With this in mind, during warm-up operation, in which the pilot valve is operated quickly and in reverse, the oil in the return side switching oil chamber to the tank is directly discharged from the normally closed valve to the drain oil passage. Then, by making it easier for the oil in the oil passage between the flow control valve and the pilot valve to replace the oil in the tank, it is possible to solve the above problems and to have the same function as the conventional technology. To aim.

[0005]

[Means for Solving the Problems]

 In order to achieve this object, the present invention provides a switching oil chamber connection port (3a, 3b) of each flow control valve (1a, 1b) with a switching oil chamber connection port and a pilot valve connection port (2a, 2b), respectively. ), And the neutral position of the directional control valve (4) is slightly higher than the maximum return oil pressure generated in the return side switching oil chambers (4a, 4b) by the return spring elasticity. Connect the drain oil passages (6a, 6b) to the tank via the normally closed valves (5a, 5b) with cracking pressure, and open the pilot oil pressure from each switching oil chamber connection port to the corresponding normally closed valve. The slow-return valves (7a, 7b) that open during the supply of each of the switching oil chamber connection ports and the normally-closed valve in the middle of the pilot oil passage (8a, 8b). When opened, the oil pressure in the corresponding return-side switching oil chamber is discharged almost at the same time. As normally closed valve is closed, one in which it sets the Litan function of Suroritan valve.

[0006]

[Action]

 Since the present invention has the above-mentioned configuration, when the pilot valve is operated to supply the pilot hydraulic pressure to one of the switching oil chambers (for example, 4a) of the directional switching valve in the neutral position, when starting the actuator, The flow control valve 1a that supplies the pilot oil pressure to the switching oil chamber 4a is fully opened, while the flow control valve 1b that returns the oil in the other switching oil chamber 4b to the tank has a narrowed flow passage. When returning to the neutral position and stopping the actuator, the flow control valve 1a that returns the oil in the one switching oil chamber 4a to the tank is throttled, and the other flow control valve is also throttled. Since the directional control valve must be switched to the actuator drive position against the elastic force of the neutral position return spring, the pilot hydraulic pressure is generated in the return side switching oil chamber by the neutral position return spring elastic force. It is common to maximize return 1.5 to 1.8 times that of the hydraulic pressure that.

For this reason, as the spool of the directional control valve slides from the neutral position to the actuator drive position by the pilot hydraulic pressure, the neutral position return spring elastic force gradually increases from the initial elastic force. The return hydraulic pressure from the chamber 4b, that is, the pressure difference before and after the throttle in the return side flow control valve 1b, is caused when the spool of the directional control valve is returned from the actuator drive position to the neutral position by the spring elasticity alone and the actuator is stopped. The return hydraulic pressure from the return side switching oil chamber 4a, that is, the pressure difference before and after the throttle in the return side flow control valve 1a is always significantly larger during the sliding of the spool.

On the other hand, since the velocity or flow rate of the oil flowing in the throttle is proportional to the square root of the oil column height corresponding to the pressure difference before and after that, the spool of the directional control valve is eventually switched from the neutral position to the actuator drive position. The switching speed at this time is significantly higher than the switching speed at the spring return of the spool from the actuator drive position to the neutral position. Moreover, when the spool is spring-returned from the actuator drive position to the neutral position and the oil in the switching oil chamber 4a is discharged to the tank, the other switching oil chamber 4b passes through the throttle of the flow control valve 1b. Since the oil must be sucked in, this not only causes resistance to return to the neutral position of the spool, but is also influenced by the compressibility of the oil.

Therefore, the switching speed of the directional switching valve when the actuator that has driven the movable member having a large inertia is stopped is made significantly lower than the switching speed of the directional switching valve when the actuator is started, and the switching speed of the actuator is significantly reduced. It is possible to prevent the impact that occurs when stopping.

When the pressure at the pilot valve connection port of the flow rate control valve becomes higher than the pressure at the switching oil chamber connection port during the normal control of the above-described directional control valve, the normally closed valve is placed between the pilot operation parts on both sides thereof. Is closed and biased by the elastic force of the valve closing spring that sets the cracking pressure, there is no risk of the normally closed valve opening, and conversely the pressure at the switching oil chamber connection port is increased by the pilot valve. When the pressure becomes higher than the pressure at the connection port, it occurs when the oil in the return side switching oil chamber returns to the tank, and the maximum pressure difference is the maximum pressure difference generated in the switching oil chamber by the neutral position return spring elasticity of the directional switching valve. There is no danger of the normally closed valve opening because it is equal to or lower than the return hydraulic pressure.

Further, when the forward / reverse drive of the actuator is suddenly reversed and switched, the operation lever of the pilot valve is operated in one direction, for example, in the forward direction to switch the directional switching valve to the forward drive position. , While the actuator is being driven in the forward direction, the operating lever is suddenly operated in the reverse direction to supply the pilot hydraulic pressure to the switching oil chamber (for example, 4b) in the reverse direction of the directional control valve. When the directional control valve starts switching to the reverse drive position, the oil in the switching oil chamber 4a on the return side to the tank at that time receives the neutral position return spring elasticity and the spool pressing force by the pilot hydraulic pressure at the same time. Since the pressure becomes higher than the cracking pressure of the normally closed valve 5a, this high oil pressure opens the slow return valve 7a to open the normally closed valve, and the oil pressure in the return side switching oil chamber 4a changes to the drain oil passage 6a. Begins to be discharged. In this case, since the flow control valve 1a has a large resistance due to its throttle, the discharged hydraulic pressure almost flows to the normally closed valve 5a having a small resistance.

When the oil pressure in the return side switching oil chamber 4a begins to be discharged to the drain oil passage 6a, not only the primary side oil pressure of the normally closed valve decreases but also near the end of switching of the directional switching valve to the reverse drive position. , The pressure corresponding to the difference between the spool pressing force due to the pilot oil pressure and the neutral position return spring elasticity acts on the oil in the return side switching oil chamber, so that the oil pressure in the return side switching oil chamber is the normally closed valve. Although the normally closed valve starts to close when the pressure drops below the cracking pressure, the slow-return valve operates so that the normally closed valve closes when the hydraulic pressure in the return side switching oil chamber is almost completely discharged. Can be repeated.

[0013]

【Example】

 A tandem center type directional control valve 4 to which pressure oil is supplied from a hydraulic pump 9 is used to extend and retract a boom cylinder (which may be an arm cylinder or a bucket cylinder) 10 of a power shovel. Will be explained.

The output ports of the pair of pilot valves 12a, 12b, which are supplied with a constant pilot hydraulic pressure from a pilot hydraulic power source 11 such as an accumulator, have their respective output ports of the flow control valves 1a, 1b with pressure compensation via oil passages 13a, 13b, respectively. When the operating lever 14 which is connected to the valve connection ports 2a and 2b and selectively controls the both pilot valves is in the neutral position shown in FIG. 1, the pilot valves connect the oil passages 13a and 13b to the tank T, respectively. Pilot hydraulic pressure is supplied to the left oil passage 13a when the operation lever 14 is rotated to the left side in the figure, and to the right side oil passage 13b when the operation lever is rotated to the right side. To be done.

The flow control valve 1a, the normally closed valve 5a, and the slow return valve 7a constitute one valve block 15a, and the flow control valve 1b, the normally closed valve 5b, and the slow return valve 7b also have one valve block 15b. Since both valve blocks have the same structure, the structure of the valve block 15a will be described below. However, a added to the end of the numeral reference of each component of the valve block 15a is changed to b. Those are the corresponding components of the valve block 15b.

The flow control valve 1a is provided with pressure compensation, and as shown in FIG. 2, on both sides of a fixed throttle 17a provided in the middle of a cylindrical spool 16a, oil chambers 19a and 20a which cooperate with the spool are provided on both sides. Is provided on the valve casing 18a side, and the land 22a adjacent to the annular groove 21a on the valve casing side communicating with the pilot valve connection port 2a, and the radial direction provided on the spool portion corresponding to the land 22a are formed. The variable throttle 23a is formed by the hole, and the switching oil chamber connection port 3a is formed by sequentially passing the other oil chamber 20a through a radial hole provided in a spool portion on the outer periphery thereof and an annular groove 24a on the valve casing side. An annular groove 26a that forms an on-off valve in cooperation with a land 25a formed between the annular grooves 21a and 24a on the valve housing side is provided on the spool 16a side, and the spool 16a is connected to the spool 16a shown in FIG. Shown in Figure 2 Weak compression springs 27a and 28a, which are clamped at constant positions, are installed in the oil chambers 19a and 20a, respectively. Reference numeral 29a denotes an oil passage connecting the connection port 3a to the switching oil chamber 4a of the directional control valve.

Therefore, by rotating the operating lever 14 to the left A, the pilot oil pressure is supplied from the pilot valve connection port 2a to the switching oil chamber 4a, and the directional switching valve 4 is moved to the left side from the neutral position shown in FIG. When switching to the drive position (boom lowering position), the pressure of the oil chamber 19a to which the pilot oil pressure is supplied from the variable throttle 23a in a substantially fully opened state is the oil pressure to which the pilot oil pressure is supplied from the oil chamber through the fixed throttle 17a. Since the pressure is higher than the pressure in the chamber 20a, the spool 16a slides to the left from the normal position in FIG. 2 to open the on-off valve including the land 25a on the valve casing side and the annular groove 26a on the spool side. The casing-side annular grooves 21a and 24a communicate with each other by the spool-side annular groove 26a so that the flow path is fully opened, and the pilot hydraulic pressure is supplied to the switching oil chamber 4a with almost no resistance, and the other is turned off. The oil in the oil exchange chamber 4b is discharged to the tank T through the throttles 17b and 23b and the pilot valve 12b in order.

When the directional control valve, which has been switched to the boom lowering position, is returned to the neutral position by the spring by returning the operating lever 14 to the neutral position shown in the drawing, the return hydraulic pressure in the switching oil chamber 4a is changed to the connection port. 3a is supplied to the oil chamber 20a, while the connection port 2a is connected to the tank T via the pilot valve 12a, the pressure in the oil chamber 20a becomes higher than the pressure in the oil chamber 19a, and the spool 16a. 2 by sliding to the right in FIG. 2, the variable throttle 23a is throttled according to the pressure difference on both sides of the fixed throttle 17a to keep the pressure difference constant, and thus the flow rate of the fixed throttle 17a is kept constant. Thus, the discharge of the oil in the switching oil chamber 4a is delayed.

The normally closed valve 5a communicates with a land 33a provided in the middle of a rod-shaped spool 32a having piston-shaped lands 30a and 31a at both ends and a switching oil chamber connection port 3a provided on the valve casing side. The sliding valve is constituted by the land 36a formed between the annular groove 34a that forms the drain oil passage 6a and the annular groove 35a that communicates with the drain oil passage 6a, and the pilot oil passage 37a in the spool 32a is connected to the pilot valve connection port 2a. A valve closing spring 39a that regulates the cracking pressure is compression-loaded into the hydraulic oil chamber 38a on the side of the land 30a that is in constant communication with the hydraulic oil chamber 40a on the side of the land 31a, and the pilot oil passage 8a and the flow control valve. The oil chamber 20a of 1a is sequentially connected to the switching oil chamber connection port 3a.

The slow return valve 7a inserted in the middle of the pilot oil passage 8a has a small hole 43a for delaying the closing of the normally closed valve 5a to an in-line type check valve 42a which is normally biased to be closed by a weak compression spring 41a. When the hydraulic pressure in the return side switching oil chamber 4a exceeds the cracking pressure of the normally closed valve and the slow return valve 7a and the normally closed valve 5a are opened as shown in FIG. 3, the normally closed valve is opened. As described above, the diameter of the small hole 43a of the slow-return valve is set so that the normally closed valve closes at the same time as the completion of the discharge of the hydraulic pressure in the return side switching oil chamber 4a.

Although one embodiment has been described above, it is needless to say that the flow rate control valve is configured with pressure compensation, and it is also possible to use a slow return valve.

[0022]

[Effect of the device]

 Since the present invention has the above-mentioned configuration, when the normal directional control valve, in which the actuator drive time is relatively long, is controlled, the neutral position return speed of the directional control valve that returns the spring from the actuator drive position to the neutral position is changed from the neutral position to the actuator. Not only can the impact that occurs when the actuator stops suddenly be prevented by making it slower than the switching speed of the directional control valve to the drive position, but also in the case where the forward / reverse drive of the actuator is reversed and the switching is suddenly performed, With the same effect of the conventional technology that automatically increases the neutral position return speed, and during warm-up operation in winter, the oil in the oil passage between the flow control valve and the pilot valve is replaced with the oil in the tank. In this way, it is possible to reduce the warm-up time by quickly reversing the forward / backward empty motion of the movable member by the actuator and to shorten the warm-up time, and to prevent the driver's fatigue based on this. An effect which can be long time the life of the equipment units.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram of an embodiment of the present invention.

FIG. 2 is a detailed view of a part of FIG.

FIG. 3 is an explanatory diagram of the operation of FIG.

[Explanation of symbols]

 1a, 1b Flow control valve 2a, 2b Pilot valve connection port 3a, 3b Switching oil chamber connection port 4 Directional switching valve 4a, 4b Switching oil chamber 5a, 5b Normally closed valve 6a, 6b Drain oil passage 7a, 7b Slow return valve 10 Power shovel Boom cylinders 12a, 12b Pilot valve 14 Operation lever

Claims (1)

[Claims for utility model registration] [Claim 1] Halfway of both side oil passages between the switching oil chambers on both sides of the directional control valve equipped with the neutral position return spring and the pilot valves for supplying and discharging the pilot hydraulic pressure respectively. In the hydraulic control circuit of the directional control valve, the flow path is fully opened when the pilot oil pressure is supplied to the switching oil chamber, and the flow control valve is inserted when the oil is discharged from the switching oil chamber. , The switching oil chamber connection port (3a, 3) of each flow control valve (1a, 1b)
In b), the pilot operation is performed by the pressure difference between the switching oil chamber connection port and the pilot valve connection port (2a, 2b), respectively, and its return by the neutral position return spring elasticity of the direction switching valve (4). Through the normally closed valve (5a, 5b) having a cracking pressure slightly higher than the maximum return oil pressure generated in the switching oil chamber (4a, 4b) on the side of the drain oil passage (6).
a, 6b) and the slow-return valves (7a, 7b) which are opened from the respective switching oil chamber connection ports to the corresponding normally closed valves when the valve opening pilot oil pressure is supplied to the switching oil chamber connection port and the normally closed valve, respectively. When the normally closed valve is opened once by inserting it in the middle of the pilot oil passage (8a, 8b) between, the normally closed valve closes at the same time when the discharge of the hydraulic pressure in the corresponding return side switching oil chamber is completed. Thus, the hydraulic control circuit for the directional control valve is characterized in that the return function of the slow return valve is set.