Hydraulic Control System

Abstract

To reduce heating caused by switching control at a high frequency and reduce failure probability of a control circuit, in a switching control circuit.SOLUTION: A hydraulic control system comprises: an operation device 21; a hydraulic valve 23; electromagnetic proportional valves 24, 25 controlling a hydraulic valve 23; and a control unit 20 controlling electric current applied on the electric valves based on an operational position of the operation device 21 commanding operation of the electromagnetic proportional valves through switching control, wherein the control unit 20 carries out switching control of the current applied on the electromagnetic valves at a first frequency when the operational position is in a neutral area, and switching control of the current applied on the electromagnetic valves at a second frequency when the operational position is in an operational area.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a hydraulic control system applied to a vehicle. [Background technology]

[0002] In recent years, construction machinery has increasingly adopted electronic controls to improve construction efficiency, including providing operator support and remote control. Furthermore, most construction machinery is hydraulically operated. Among hydraulic components, the solenoid proportional valve is a component that acts as the boundary between electricity and hydraulics, switching and adjusting hydraulic paths according to the applied drive current.

[0003] Normally, the drive current applied to a proportional solenoid valve is controlled by switching. In recent years, it has become known that high-frequency switching control of the drive current of a proportional solenoid valve contributes to improving the operability and comfort of machinery, and various specific examples have been presented, including in the following literature. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4802204 Summary of the Invention [Problem to be solved by the invention]

[0005] As in Patent Document 1, performing switching control of current at a high frequency means that the current control circuit continues to experience large switching losses, which can result in increased heat generation and a higher probability of failure of the control circuit.

[0006] The present invention has been made in consideration of the above-mentioned problems, and its object is to reduce heat generated in a switching control circuit due to switching control at high frequencies, and to reduce the probability of failure of the control circuit. [Means for solving the problem]

[0007] In order to solve the above problems, the hydraulic control device of the present invention is a hydraulic control system having an operating device, a hydraulic oil control valve, a solenoid valve that controls the hydraulic oil control valve, and a control device that switches and controls the current applied to the solenoid valve based on the operating position of the operating device that instructs the operation of the solenoid valve, and is characterized in that when the operating position is in a neutral region, the control device switches and controls the current applied to the solenoid valve at a first frequency, and when the operating position is in an operating region, the control device switches and controls the current applied to the solenoid valve at a second frequency different from the first frequency. [Effects of the Invention]

[0008] According to the present invention, it is possible to perform switching control of the current applied to the solenoid valve at a plurality of different frequencies. Therefore, it is possible to perform switching control at not only high frequencies but also relatively low frequencies depending on the operating conditions of the solenoid valve, which makes it possible to suppress heat generation and reduce the probability of failure of the control circuit compared to when switching control is performed at high frequencies. Further features related to the present invention will become apparent from the description of the present specification and the accompanying drawings. In addition, problems, configurations, and effects other than those described above will become apparent from the following description of the embodiments. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a diagram showing an overview of a hydraulic excavator to which a hydraulic control system according to the present invention is applied; [Figure 2] 1 is a block diagram showing an overview of a hydraulic control system according to a first embodiment of the present invention. [Figure 3] FIG. 10 is a diagram showing an example of a current control waveform in low-frequency switching. [Figure 4] FIG. 10 is a diagram showing an example of a current control waveform in high-frequency switching. [Figure 5] FIG. 4 is a block diagram showing the function of an electromagnetic proportional valve control unit. [Figure 6] FIG. 3 is a block diagram showing the function of a drive signal generating unit. [Figure 7] FIG. 3 is a diagram showing an example of a current-pilot pressure characteristic applied to an electromagnetic proportional valve. [Figure 8] 3 is a diagram showing the functional configuration of the operating device and changes in an instruction current value in response to an operation signal in the first embodiment of the present invention. FIG. [Figure 9] 4 is a flowchart showing a process of switching the switching frequency in response to an operation of an operating device in the first embodiment of the present invention. FIG. [Figure 10] 4 is a diagram showing an operation signal and an instruction current value before the start of operation in the first embodiment of the present invention. FIG. [Figure 11] 5A and 5B are diagrams showing operation signals and command current values ​​after the start of operation in the first embodiment of the present invention. [Figure 12] FIG. 4 is a diagram showing an operation signal and an instruction current value during the end of an operation in the first embodiment of the present invention. [Figure 13] FIG. 5 is a block diagram showing an outline of a hydraulic control system according to a second embodiment of the present invention. [Figure 14] FIG. 10 is a diagram showing the functional configuration of an operating device and changes in an instruction current value in response to an operation signal in a third embodiment of the present invention. [Figure 15] FIG. 11 is a flowchart showing an operation mode determination process in a third embodiment of the present invention. [Figure 16] FIG. 11 is a flowchart showing a process of switching the switching frequency in response to an operation of an operating device in a third embodiment of the present invention. [Figure 17] 10A and 10B are diagrams showing operation signals and command current values ​​before and after a transition to an operation mode in a third embodiment of the present invention. [Figure 18] 11 is a diagram showing an operation signal and a command current value after an operation is started after a transition to an operation mode in the third embodiment of the present invention. FIG. [Figure 19] FIG. 11 is a diagram showing an operation signal and an instruction current value during the end of an operation in the third embodiment of the present invention. [Figure 20] FIG. 11 is a diagram showing operation signals and command current values ​​during the time when an operation mode is ended in the third embodiment of the present invention. [Figure 21]FIG. 11 is a flowchart showing a process of switching the switching frequency in response to an operation of an operating device in a fourth embodiment of the present invention. [Figure 22] 10 is a diagram showing an operation signal and an instruction current value after the start of operation in the fourth embodiment of the present invention. FIG. [Figure 23] FIG. 10 is a diagram showing an operation signal and an instruction current value during the end of an operation in the fourth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment will be described with reference to the drawings.

[0011] [First embodiment] 1 is a diagram showing a hydraulic excavator 100 to which the hydraulic control system according to the present invention is applied. The basic structure of the hydraulic excavator 100 is made up of three basic parts: a lower traveling body 7 that travels by driving tracks, an upper rotating body 8 that is rotatably mounted on the lower traveling body 7, and a front attachment 9 that is rotatably (up and down) attached to the upper rotating body 8. A prime mover 3, a pump unit 4, etc. are mounted on the upper rotating body 8.

[0012] The components that directly generate power to operate the hydraulic excavator 100 are called actuators. The hydraulic excavator 100 has multiple actuators, but Figure 1 shows, as examples, an arm cylinder 1, which is an actuator for operating the front attachment 9, and a travel motor 2, which is an actuator for traveling the lower traveling body 7.

[0013] Fig. 2 is a block diagram showing the functional configuration of a hydraulic control system applied to the hydraulic excavator 100 shown in Fig. 1. The hydraulic oil that drives the arm cylinder 1, which is an actuator, is supplied by a main pump 40, and the direction and flow rate of the hydraulic oil are controlled by the displacement of a hydraulic control valve 23. A hydraulic control valve 23 is provided for each actuator, but for simplicity, only one is shown in Fig. 2. Furthermore, parts that are not specific to the present invention, such as a pressure relief valve, are not shown.

[0014] The solenoid proportional valves 24, 25 adjust the flow path for the hydraulic oil supplied by the pilot pump 41, thereby controlling the displacement of the hydraulic control valve 23. When the actuator is not in operation, the hydraulic control valve 23 is in a neutral state, and the flow path to the actuator for the hydraulic oil supplied by the main pump 40 is closed. When the actuator is to be operated, the hydraulic control valve 23 is pushed in a direction along the flow path of the hydraulic oil according to the drive current supplied to the solenoid proportional valves 24, 25, thereby controlling the displacement. Note that although an example using a solenoid proportional valve is shown in this embodiment, another solenoid valve may be used instead of the solenoid proportional valve.

[0015] The control unit 20 has an input signal processing unit 201, solenoid proportional valve control units 202 and 203, and a switching frequency instruction unit 204, and controls the current supplied to the solenoid proportional valves 24 and 25. The input signal processing unit 201 receives and processes outputs from the operation device 21 and signals from sensors and switches (sensor 11 is shown as an example in FIG. 2) attached to various parts of the vehicle body, and outputs them as operation signals 3100, 3101, and 3102, respectively. The solenoid proportional valve control units 202 and 203 control the current supplied to the solenoid proportional valves 24 and 25 to a desired value in accordance with the operation signals 3100 and 3101.

[0016] The switching frequency instruction unit 204 monitors the operation signals 3100, 3101 received from the input signal processing unit 201, and outputs switching frequency instruction signals 3110, 3111 to the solenoid proportional valve control units 202, 203 in accordance with changes in the operation signals, and switches the instructions. In addition, the operation start determination unit 205 and the operation end determination unit 206 determine the timing for switching the switching frequency instruction signals 3110, 3111. In addition, as will be described in a later embodiment, the switching frequency instruction unit also functions as an operation mode determination unit that determines whether an operation mode flag is valid or not, based on the operation signal 3102 received from outside the control unit 20.

[0017] In the present invention, it is assumed that the drive current of the electromagnetic proportional valve is switched and that the switching frequency is changed between high and low, and therefore, hereinafter, switching control using low and high frequencies will be described. Note that, hereinafter, "switching control of the drive current applied to the electromagnetic proportional valve" and "switching control of the electromagnetic proportional valve" have the same meaning.

[0018] First, an example of voltage and current waveforms when performing switching control at low frequency is explained using Figure 3. In Figure 3, CL The average current I L1 , I L2 , I L3 An example of determining the value of is shown below. Due to low frequency switching, the current waveform is accompanied by pulsation of a certain magnitude or more.

[0019] Although it depends on the hydraulic equipment used, the switching frequency (= 1 / T CL ) is often between about 100 and several hundred Hz. L1 , ΔI L2 , ΔI L3 ) changes depending on the ratio of ON / OFF time of the voltage.

[0020] Next, an example of voltage and current waveforms for high-frequency switching control is explained using Figure 4. In Figure 4, the carrier period T CH In addition to the ON / OFF time ratio of the voltage at CH A period T longer than D The dither (oscillation) is actively controlled to control the average current within this period.

[0021] In addition, in FIG. 4, the dither period T D is the carrier period T CH The ratio of the two periods is set to 10 times the dither period T D is the carrier period T CHIt can be selected appropriately as long as it does not affect the switching control in Fig. 4. Also, although a triangular wave is shown as an example of a current dither control waveform in Fig. 4, the optimal waveform shape and amplitude depend on the characteristics of the hydraulic equipment, and waveforms other than a triangular wave can also be used.

[0022] Next, Fig. 5 shows an internal functional block diagram of the solenoid proportional valve control unit 202, which constitutes part of the control unit 20 in Fig. 2. Since the solenoid proportional valve control units 202 and 203 both have the same configuration, only the solenoid proportional valve control unit 202 will be described here. The same applies to the drive signal generation unit described in Fig. 6.

[0023] The electromagnetic proportional valve control unit 202 has an operation signal acquisition unit 300, a drive signal generation unit 301, a electromagnetic proportional valve drive unit 302, and a current detection unit 303. The operation signal acquisition unit 300 generates a drive signal generation instruction signal 3140 based on an operation signal 3100 received from the input signal processing unit 201, and transmits the signal to the drive signal generation unit 301.

[0024] The drive signal generation unit 301 generates a drive signal 3150 in accordance with a drive signal generation instruction signal 3140 received from the operation signal acquisition unit 300. The solenoid proportional valve drive unit 302 controls the switching of a drive current 3120 to be applied to the solenoid proportional valve 25 in accordance with the drive signal 3150 received from the drive signal generation unit 301, and supplies it to the solenoid proportional valve 25. Note that this drive current 3120 is monitored and detected by a current detection unit 303, which generates a feedback signal 3130 in accordance with the detected value and transmits it to the drive signal generation unit 301. Therefore, the drive signal generation unit 301 generates a drive signal 3150 based on this feedback signal 3130 in addition to the drive signal generation instruction signal 3140.

[0025] The drive signal generation unit 301 also switches the switching frequency of the drive signal 3150 to be output to the solenoid proportional valve drive unit 302 in accordance with a switching frequency instruction signal 3110 received from the switching frequency instruction unit 204 (see FIG. 2).

[0026] 6 shows a functional block diagram of the drive signal generation unit 301. The drive signal generation unit 301 has current command value calculation units 3200 and 3201, low-frequency / high-frequency drive signal generation units 3205 and 3204, and low-frequency / high-frequency average current calculation units 3206 and 3207, which correspond to low-frequency signals and high-frequency signals, respectively.

[0027] The drive signal generation unit 301 also has a switching frequency instruction determination unit 3203 that determines whether the switching frequency instruction signal 3110 received from the switching frequency instruction unit 204 is a signal that indicates a low frequency or a high frequency, and a drive signal switching unit 3208 that switches the switching frequency of the drive signal 3150 in accordance with the determination.

[0028] Low-frequency / high-frequency current instruction value calculation units 3200, 3201 calculate the values ​​of low-frequency / high-frequency currents to be generated in response to the drive signal generation instruction received from operation signal acquisition unit 300. Then, low-frequency / high-frequency drive signal generation units 3205, 3204 generate drive signals in accordance with the calculated results. Then, a switching frequency instruction determination unit selects a frequency to be applied, and one of the drive signals is output by switching of drive signal switch unit 3208.

[0029] A low frequency average current calculation unit 3206 and a high frequency average current calculation unit 3207 each calculate a control period average of the actual current from the feedback signal 3130. Furthermore, a dither command signal generation unit 3202 superimposes a dither command on the high frequency drive signal as necessary.

[0030] Next, Fig. 7 shows an example of the current-pilot pressure characteristics of an electromagnetic proportional valve. id_max In the range of I, the pilot pressure is not generated and the current is I id_max The pilot pressure starts to rise after exceeding I. Normally, to prevent the solenoid proportional valve from sticking, even when the hydraulic control valve 23 is not operated, a certain standby current is passed within a range that does not cause the pilot pressure to rise. In Figure 7, the drive current is I id_maxHowever, there may be hysteresis and other nonlinearities inherent to the solenoid valve.

[0031] Next, the operating device 21, the operating signal S generated in accordance with the operating state of the operating device 21, and the command current value generated in accordance with the operating signal S according to the first embodiment of the present invention will be described with reference to FIG.

[0032] Examples of the operating device 21 include a lever device operated by an operator in the cab of a construction machine, a remote control device used for remote control, etc. In FIG. 8, a lever device is shown as an example of the operating device, and the output characteristics of the operating signal S according to the tilt angle of the lever, and the command current value I of the solenoid proportional valve are shown. 24 , I 25 The mapping of the indicated current value I 24 , I 25 indicate the current values ​​applied to the proportional solenoid valves 24 and 25, respectively.

[0033] As shown in FIG. 8, the operation signal S varies depending on its range, from a neutral region (S 0B <S<S 0A ), and the two outer dead zones (S 0A <S<S sA , S sB <S<S 0B ), and the two outer operating regions (S>S sA , S sB ) range.

[0034] When the lever is in the neutral zone or the dead zone, the command current value I to the solenoid proportional valves 24 and 25 is 24 , I 25 are both standby currents I id24 , I id25 ​When the lever is tilted in either direction by a certain angle or more and enters the operating range, a drive current larger than the standby current is supplied to one of the solenoid proportional valves 24, 25 that corresponds to the operating direction of the solenoid proportional valve. In other words, when there are multiple solenoid proportional valves, each has its own corresponding operating range. In this embodiment, there are two operating ranges corresponding to the solenoid proportional valves, but the same applies if there are three or more operating ranges.

[0035] In this embodiment, the driving current is I id24 , I id25 This shows an example of linear control in proportion to the change in the operation signal S in the range larger than <I<I id ) and a current value greater than that, or control at a current value set in stages. Also, although the operation signal is shown as an analog signal in Fig. 8 for the sake of simplicity, it may alternatively be shown as the duty ratio of a periodic pulse signal.

[0036] Next, a flow of the switching frequency instruction process performed by the switching frequency instruction unit 204 in the control unit 20 of Fig. 2 is shown in Fig. 9. Also, changes in the operation signal and the instruction current value caused by the operation of the operation device 21 are shown in Figs.

[0037] First, the operation signal S and the command current value when the operator is not operating the operation device are shown in Figure 10. The operation signal S is constant at the value S0 in the neutral region, and the solenoid proportional valves 24 and 25 both supply a standby current I id is supplied (the command current value is indicated by a dashed line). In the state of FIG. 10, the switching frequency command unit 204 periodically repeats the process of following the flow of FIG. 9, namely, "No" in S1001, "No" in S1002, and "Yes" in S1005, and then terminating. For the sake of simplicity, I id =I id24 =I id25 However, for the purpose of tuning the solenoid proportional valves individually, the standby current I id24 and Iid25 The values ​​of may be different.

[0038] Next, Fig. 11 shows the transition of the operation signal S and the command current value after the operator starts to operate the operation device. When the operator starts to push down the lever, the operation signal S changes, and at time t 0A At this point, the operating signal S reaches the maximum value S in the dead band. 0A However, at this point, the time spent in the dead zone is still short, and the time t 0A From time T S Until this time has elapsed, the flow in FIG. 9 will go through "No" at S1001, "No" at S1002, "No" at S1005, "No" at S1008, and "Yes" at S1009, but by going through "No" at S1010, low-frequency switching control will continue.

[0039] In FIG. 11, the value of the operation signal S is within the dead band S 0A ~S sA range for a given time T S Stay at time t 0As 9, the same flow is followed up to S1009, and by following "Yes" in S1010, the switching frequency of the solenoid proportional valve 25 is switched to the high frequency.

[0040] To set the switching frequency of the solenoid proportional valve 25 to a high frequency as described above, the switching frequency instructing unit 204 transmits a switching frequency instruction signal 3110 instructing the solenoid proportional valve control unit 202 to use a high frequency. In the drive signal generating unit 301 of the solenoid proportional valve control unit 202 that has received the high frequency instruction, the switching frequency instruction determining unit 3203 that has received the instruction determines that the instruction is a high frequency instruction, and the drive signal switching unit 3208 switches the switching frequency of the solenoid proportional valve 25 to a high frequency.

[0041] On the other hand, for the solenoid proportional valve 24, the switching frequency instruction signal 3111 instructing low frequency switching to the solenoid proportional valve control unit 203 continues to be sent from the switching frequency instruction unit 204, and low frequency switching continues.

[0042] In order to determine the duration of time that the operation signal S has been in the dead band, for example, a counter (not shown) is provided in the operation start determination unit 205, and the counter is incremented each time "Yes" is selected in S1008 or S1009 in the flow shown in FIG. 9, which is executed periodically, and the determination can be made by comparing the counter with a preset count value.

[0043] Also, determining that the operation signal S is in the dead band for a certain period of time or more means, in other words, determining whether the time differential value (dS / dT ≒ ΔS / T S ) is a given value ((S sA -S 0A ) / T S ) or less.

[0044] As the operator continues to operate the control device, the operation signal S is sA At this point, S>S sA After this, the current command value to the solenoid proportional valve 25 increases in accordance with the transition of the operation signal S, and the hydraulic control valve 23 starts to operate the actuator. Meanwhile, the solenoid proportional valve 24 operates at a standby current I id The supply of oil continues, and the operation of the hydraulic control valve 23 is not affected.

[0045] Next, the transition of the operation signal S and the command current value when stopping the actuator will be described with reference to Figure 12. Operation signal S>S sA The operation signal S, which had been fluctuating at time t sA At the time of 'S sA In this case, the time t sA 'After this, the drive current of the solenoid proportional valve 25 is the standby current I idAt this point, the operation signal is still within the dead band, so in the flow of Fig. 9, "No" is selected in S1001 and "Yes" is selected in S1002, but the flow ends with "No" in S1004, so that the current supply to the solenoid proportional valve 25 continues to be switched at high frequency.

[0046] Then, the operation signal S decreases further, and at time t s0 At this time, the operation is judged to be completed by following "Yes" in S1002 and then "Yes" in S1004 in the flow of FIG. 9, and the switching frequency of the solenoid proportional valve 25 is set to a low value in S1007. The method for setting the switching frequency of the solenoid proportional valve 25 to a low value is the same as the method for setting it to a high frequency, described above.

[0047] As described above, in this embodiment, only the solenoid proportional valve 25, which affects the operation of the hydraulic control valve 23, is switched at a high frequency, and the solenoid proportional valve 24, which does not affect the operation of the hydraulic control valve 23, is switched at a low frequency. Therefore, compared to when all the solenoid proportional valves are constantly switched at a high frequency, it is possible to significantly suppress heat generation due to switching, and it is possible to reduce the possibility of circuit failure, etc.

[0048] [Second embodiment] Next, a hydraulic control system according to a second embodiment of the present invention will be described with reference to Fig. 13. In Fig. 13, the solenoid proportional valve control units 202 and 203 in the hydraulic control system shown in Fig. 2 are shown as a single functional block 2001, and a solenoid proportional valve drive unit 3001 corresponding to the solenoid proportional valve 24 and a solenoid proportional valve drive unit 3002 corresponding to the solenoid proportional valve 25 are shown as a thermally coupled package 3003.

[0049] In this embodiment, the reason why the two solenoid proportional valve drive units 3001 and 3002 are housed in a single package 3003 is as follows. Specifically, elements such as transistors and FETs are typically used for current switching control. In recent years, semiconductor devices that house multiple elements in a single IC package have come to be used for such switching elements. The hydraulic control system according to the present invention also uses multiple solenoid proportional valves to control the displacement of the hydraulic control valve 23. Therefore, by sharing the solenoid proportional valve drive units 3001 and 3002, which perform switching control among the circuits constituting the solenoid proportional valve control unit 2001, in a single IC package 3003, it becomes easier to disperse the heat generated by the solenoid proportional valve drive units 3001 and 3002, which are the main heat source.

[0050] [Third embodiment] Next, a hydraulic control system according to a third embodiment of the present invention will be described with reference to Figures 14 to 20. This embodiment differs from the first and second embodiments in that the start and end of operation are determined based on signals from sensors and switches external to the control unit 20, rather than on operation signals 3100 and 3101.

[0051] That is, in the control unit 20, the operation start determination unit 205 and the operation end determination unit 206 determine the start / end of the operation based on the operation signal 3102 received from the input signal processing unit 201. Note that the configuration of the control unit 20 in this embodiment may be the same as that of either the first embodiment or the second embodiment. The same applies to the fourth embodiment described later.

[0052] First, an example of an operating device in this embodiment will be described with reference to FIG. 14. As shown in FIG. 14, a lever is also used as an operating device in this embodiment. However, the operating device in this embodiment does not have the dead zone shown in FIG. 8 that the operating device in the first embodiment has. Therefore, the operating signal S is within a range (S 0B <S<S 0A ) and the range (S>S0A , S 0B ) value.

[0053] In this embodiment, when there is no operation by the operator and the operation signal S is in the neutral region, the switching frequency instruction unit 204 detects whether the operation start command is valid or invalid at a predetermined cycle. This state in which the validity of the operation start command is detected is defined as the "operation mode" in this embodiment. Examples of signal sources related to the generation of the operation signal 3102 for transitioning to or canceling this operation mode include a selector switch attached to the operation device, a grip switch incorporated in the lever device, and an instruction signal by remote control. In this embodiment, the sensor 11 is used as an example (see FIG. 2).

[0054] FIG. 15 shows the process of determining the start and end of operation performed by the switching frequency instruction unit 204. In the flow of FIG. 15, when it is determined that the operation signal S is in the neutral region ("Yes" in S3001) and it is detected that the operation signal 3102 is valid ("Yes" in S3002), the control unit 20 determines that it is in the operation mode (S3003). Then, when it is determined that it is in the operation mode, the control unit 20 switches the switching frequencies of both the solenoid proportional valves 24, 25 to high frequencies (S3005). Note that the determination in S3002 is set by an operation mode flag (not shown) inside the switching frequency instruction unit 204. As described above, in this embodiment, the switching frequency instruction unit 204 determines the validity of the operation mode, and therefore the switching frequency instruction unit 204 also functions as an operation mode determination unit in the present invention.

[0055] ​Next, a flow of the switching frequency switching process performed by the switching frequency instruction unit 204 in this embodiment is shown in Fig. 16. Changes in the operation signal and the instruction current value associated with the operation of the operation device 21 are shown in Figs. 17 to 20. Note that the switching process of the switching frequency instruction in response to the transition of the operation signal S shown in Fig. 16 is executed at a different timing from the process described in Fig. 15. The execution cycle of the process may be the same as or different from the execution cycle of the process in Fig. 15.

[0056] First, the judgment of the start of operation and the accompanying switching control of the solenoid proportional valves 24, 25 are shown in Figure 17. While there is no operation by the operator and the operating position of the operating device is in the neutral region, the operation signal S is constant at S0 within the neutral region, the hydraulic control valve 23 is in the neutral state, and the standby current I is supplied to both the solenoid proportional valves 24, 25. id is supplied.

[0057] Time t in Figure 17 0As At this point, the operation start determination unit 205 detects the start of operation by receiving an operation signal 3102 from outside the control unit 20. At this point, in the processing of Fig. 16, "Yes" is selected in S3101, "Yes" in S3102, and "Yes" in S3104, and the switching frequency of the proportional solenoid valve 24 is switched to high frequency.

[0058] As described above, the processing in FIG. 16 is executed at a predetermined cycle, and subsequently, "Yes" in S3101, "No" in S3102, "Yes" in S3103, and "Yes" in S3105 are selected, and the switching frequency of the solenoid proportional valve 25 is switched to high frequency. In this way, when the operation mode is switched to, the switching frequencies of both the solenoid proportional valves 24 and 25 are switched to high frequency. However, since the operation signal S is still in the neutral region, even if the switching frequency is switched to a high frequency, the standby current I id is being supplied.

[0059] Next, the transition of the operation signal S and the current control of the solenoid proportional valves 24, 25 after the transition to the operation mode are shown in FIG. 18. When an operation is performed by the operator, at time t sA At this point, the operation signal S has moved out of the neutral region (S>S 0A ) When the switching frequency instruction unit 204 determines this, the processing in FIG. 16 follows the sequence of "Yes" in S3101, "No" in S3102, "No" in S3103, "No" in S3106, "No" in S3109, and "Yes" in S3110. At this point, the switching frequency instruction unit 204 instructs the solenoid proportional valve 24 to switch to low frequency switching, and the standby current I id Therefore, the solenoid proportional valve 24, which continues to be switched at a low frequency, does not affect the operation of the hydraulic control valve 23.

[0060] Meanwhile, the solenoid proportional valve 25 continues to perform high frequency switching control, and as the operation signal S changes, a drive current is supplied to the solenoid proportional valve 25, and the hydraulic control valve 23 starts driving the actuator.

[0061] Next, as shown in FIG. 19, the value of the operation signal S decreases, and at time t s0 Within the neutral zone at the time of 0B <S<S 0A When the switching frequency instruction unit 204 detects this, it follows "Yes" in S3102 during the processing of FIG. 16, and then follows "Yes" in S3104, and sets the switching frequency of the solenoid proportional valve 24 high (S3107).

[0062] Finally, the operation signal 3102 transmitted from outside the control unit is invalidated, and at time t 0As Assume that this is detected by '. At this time, there is no operation from the operator, and the operation signal S is in the neutral region. Then, in the operation start determination process of FIG. 15, by following "Yes" in S3001 and "No" in S3002, S3004 and S3006 are executed, and the switching frequencies of both solenoid proportional valves 24 and 25 are switched to low. This ends the operation mode.

[0063] As described above, in this embodiment, when the control unit 20 determines that it is in the operation mode, it performs high-frequency switching control on both of the solenoid proportional valves 24, 25, and then switches the switching frequency of the solenoid proportional valve that does not affect the operation of the hydraulic control valve 23 to a low frequency. This suppresses switching heat generated by controlling the solenoid proportional valve, which does not affect the operation of the hydraulic control valve, at a low frequency, while the solenoid proportional valve that operates the hydraulic control valve is already switched at a high frequency when its operation starts, making it possible to control it with very good responsiveness.

[0064] In this embodiment, the transition to and release from the operation mode does not necessarily have to be performed each time the actuator is operated; for example, it is also possible to maintain the operation mode at all times from start to stop of the hydraulic excavator.

[0065] [Fourth embodiment] Finally, a hydraulic control system according to a fourth embodiment of the present invention will be described with reference to FIGS.

[0066] The functional configuration of the operation device 21 in this embodiment is the same as that in the third embodiment described with reference to FIG. 14. In this embodiment, when the operation signal S is in the neutral region (S 0B <S0<S 0A ), both the solenoid proportional valves 24 and 25 are switched at low frequency. When the operation signal S leaves the neutral region and enters the operating region (S>S 0A , or S 0B ), the switching frequency of the solenoid proportional valve to be driven is set high.

[0067] That is, in this embodiment, the transition to the operation mode using the operation signal 3102 as in the third embodiment is not performed, and the start / end of the operation is determined depending on whether the operation signal S itself is within the neutral region or the operating region.

[0068] ​The processing flow of the switching frequency instruction unit 204 in this embodiment is shown in Fig. 21. Furthermore, changes in the instruction current value in response to the operation of the operation device are shown in Figs.

[0069] First, the transition of the operation signal S when starting operation and the current control of the solenoid proportional valves 24, 25 are shown in Figure 22. Here, the operation signal S transitions according to the operation of the operator, and at time t sA When the operation signal S is in the neutral region (S 0B <S0<S 0A ) range and enters operating region 2 (S>S 0A 21, the process proceeds as follows: "No" in S4001, "No" in S4002, "No" in S4005, "No" in S4008, and "Yes" in S4009, and the switching frequency instructing unit 204 sets the switching frequency of the solenoid proportional valve 25 to a high value (S4010).

[0070] Next, as shown in FIG. 23, the value of the operation signal S, which is moving within the operation region 2, decreases, and at time t s0 ' in the neutral area (S 0B <S<S 0A ) When the switching frequency instruction unit 204 detects this, the switching frequency of the solenoid proportional valve 25, which had been switching at a high frequency up until then, is switched to a lower frequency (S4007) by following the process in FIG. 21 , which follows the flow from "No" in S4001 to "Yes" in S4002 and "Yes" in S4004.

[0071] As described above, this embodiment does not employ a dead band as in the first embodiment, nor an operation mode as in the third embodiment, but instead determines the start / end of operation based on whether the operation signal is in the operating region. This makes it possible to reduce the switching heat of the control circuit and the failure rate in a very simple manner. Hysteresis may be set in the threshold value of the operation signal that determines the transition to the operating region and the neutral region.

[0072] According to the embodiment of the present invention described above, the following advantageous effects are achieved. (1) A hydraulic control system having an operating device 21, a hydraulic control valve 23, electromagnetic proportional valves 24, 25 that control the hydraulic control valve 23, and a control unit 20 that switches and controls the current applied to the electromagnetic proportional valves 24, 25 based on the operating position of the operating device 21 that instructs the operation of the electromagnetic proportional valves 24, 25, wherein the control unit 20 switches and controls the current applied to the electromagnetic proportional valves 24, 25 at a first frequency when the operating position is in a neutral region, and switches and controls the current applied to the electromagnetic proportional valves 24, 25 at a second frequency different from the first frequency when the operating position is in an operating region.

[0073] The above configuration makes it possible to appropriately change the frequency at which the electromagnetic proportional valve is switched. This makes it possible to switch the electromagnetic proportional valve at a high frequency when the hydraulic control valve is operated, and at a low frequency when the hydraulic control valve is not operated. Compared to switching control at a constant high frequency, this makes it possible to suppress heat generation due to switching and reduce the probability of failure.

[0074] (2) The hydraulic control valve 23 is controlled by a plurality of individually controlled solenoid proportional valves 24, 25, the operating device is configured to be able to be positioned in a plurality of operating regions corresponding to the plurality of solenoid proportional valves 24, 25, and when the operating position is in one of the plurality of operating regions, the control unit 20 controls the solenoid proportional valve corresponding to that operating region at the second frequency and controls the remaining solenoid proportional valves at the first frequency. Therefore, it is possible to continue switching control at a low frequency for solenoid proportional valves that do not affect the operation of the hydraulic control valve, and as in (1), it is possible to reduce heat generation due to switching.

[0075] (3) The second frequency is higher than the first frequency. Therefore, in order to achieve the effects described in (1) and (2) above, the solenoid proportional valve that affects the operation of the hydraulic control valve is switched at the second frequency, and the solenoid proportional valve that affects the operation of the hydraulic control valve is switched at the first frequency.

[0076] (4) The control unit 20 has an operation mode determination section 204 that determines whether the operation mode flag is enabled. When the operation mode determination section 204 determines that the operation mode flag is enabled and the operating device 21 is in the neutral region, the control unit 20 switches the current applied to the multiple solenoid proportional valves 24, 25 at a high frequency. When the operating position moves from the neutral region to the operating region, the control unit 20 switches the current applied to the multiple solenoid proportional valves other than the solenoid proportional valve corresponding to the operating region at a low frequency. This makes it possible to suppress heat generation during operation of the hydraulic control valve, as in (1)-(3). Moreover, because the solenoid proportional valves that affect the operation of the hydraulic control valve are already switched at a high frequency before they start to operate, they can be controlled with very good responsiveness.

[0077] (5) The control unit 20 includes a plurality of elements that apply current to the respective proportional solenoid valves 24, 25. These elements are mounted in the same package. This makes it easier to disperse heat generated by the proportional solenoid valves 24, 25.

[0078] (6) The operating device 21 is configured to be able to be located in a dead zone between the neutral zone and the operating zone, and the control unit controls the current applied to the solenoid proportional valves 24, 25 at a second frequency when the operating position is in the dead zone for a predetermined time or longer. This makes it possible to prevent erroneous operation when the operating device 21 is located near the boundary between the neutral zone and the operating zone.

[0079] The present invention is not limited to the above-described embodiments, and various design modifications may be made without departing from the spirit of the present invention as defined in the claims. For example, the above-described embodiments have been described in detail to facilitate understanding of the present invention, and the present invention is not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations. [Explanation of symbols]

[0080] 20 control unit (control device), 21 operating device, 23 hydraulic control valve (hydraulic oil control valve), 24, 25 electromagnetic proportional valve (solenoid valve), 202, 203, 2001 electromagnetic proportional valve control section, 204 switching frequency instruction section (operation mode determination section), 3003 IC package

Claims

1. an operating device configured to be able to be positioned in any one of a neutral region, an operating region, and a dead zone region between the neutral region and the operating region; a hydraulic oil control valve; a pair of solenoid valves for controlling the hydraulic oil control valve; a control device that switches and controls a current applied to the solenoid valve based on an operation position of the operating device that instructs an operation of the solenoid valve; A hydraulic control system having: The control device When the operation position is in the neutral region, a current applied to the solenoid valve is switched at a first frequency; When the operation position is within the operation range, a current applied to the solenoid valve is switched and controlled at a second frequency higher than the first frequency; when the operation position is operated into the operation region after being in the dead band region for a predetermined time or more, switching control of the current applied to the solenoid valve from the first frequency to the second frequency, When the operating device is operated into the operating region after being in the dead band region for less than the predetermined time, the switching control at the first frequency is continued. A hydraulic control system characterized by:

2. An operating device; A pair of solenoid valves; a hydraulic oil control valve whose displacement is controlled by the pair of individually controlled solenoid valves; a control device that switches and controls a current applied to the solenoid valve based on an operation position of the operating device that instructs an operation of the solenoid valve; A hydraulic control system having: the operating device is configured to be able to be positioned in a plurality of operating regions respectively corresponding to the solenoid valves; the control device has an operation mode determination unit that determines whether an operation mode flag indicating whether an operation start command is valid or invalid is valid; When the operation mode determination unit determines that the operation mode flag is valid and the operation position is in a neutral region, the control device switches and controls the current applied to all of the solenoid valves at a second frequency that is higher than a first frequency; when the operation position moves from the neutral region to one of the plurality of operation regions, the control device switches and controls the current applied to the solenoid valve corresponding to that operation region at the second frequency, and switches and controls the current applied to the remaining solenoid valves other than the solenoid valve corresponding to that operation region at the first frequency; and when the operation mode flag is determined to be invalid, the control device switches and controls the current applied to all of the solenoid valves at the first frequency. A hydraulic control system characterized by:

3. 3. The hydraulic control system according to claim 1 or 2, a plurality of elements of the control device that apply currents to the pair of solenoid valves are mounted in the same package; A hydraulic control system characterized by:

4. 3. The hydraulic control system according to claim 1 or 2, The control device has hysteresis in the value of the operation signal that determines the operation region and the neutral region. A hydraulic control system characterized by:

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