PUMP DEVICE

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority under 35 U.S.C. § 119 to Japanese Patent Application 2018-039948, filed on Mar. 6, 2018, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

This disclosure relates to a pump device.

BACKGROUND DISCUSSION

JP 2011-256987A (Reference 1) discloses the following technique. In order to perform a speed change control process of an automatic transmission, there is provided a linear solenoid valve which controls a hydraulic pressure for supplying hydraulic operating oil to a friction element. When the hydraulic operating oil serving as the hydraulic pressure having an output hydraulic pressure target value is supplied from the linear solenoid valve, a command current is calculated, based on a map of the command current vs a command hydraulic pressure which is prepared for each individual linear solenoid valve.

According to Reference 1, a difference between an actual output hydraulic pressure and the command hydraulic pressure is calculated by sweeping the command current, and a reference map previously prepared based on the difference is corrected so as to prepare the map of the command current vs the command hydraulic pressure. In order to perform the automatic transmission based on the prepared map of the command current vs the command hydraulic pressure, an individual difference of electrohydrostatic control means is reduced so as to realize improved control accuracy.

JP 2005-155920A (Reference 2) discloses the following technique. A parametric variable relating to hydraulic pressure characteristics of a solenoid valve used for the automatic transmission is stored in a memory, and the parametric variable stored in the memory is called up. Based on the parametric variable, a target current for a target hydraulic pressure is calculated.

According to Reference 2, as an automatic transmission system, optimum virtual map identification information and the parametric variable which are stored in the memory are called up so as to select an optimum virtual map. Based on selection of the optimum virtual map and the parametric variable, the target current to be supplied to a target solenoid valve is calculated.

JP 2016-98768A (Reference 3) discloses the following technique for an oil pump. The oil pump includes a solenoid valve that has an inner rotor having external teeth, an outer rotor having internal teeth, and an adjustment ring for regulating a discharge amount of the hydraulic operating oil by adjusting a position, and that controls a pressure applied to the adjustment ring from a discharge port. The oil pump operates the adjustment ring by controlling the solenoid valve so as to control the discharge amount of the hydraulic operating oil.

According to Reference 3, the oil pump includes a coil spring which biases the adjustment ring in a direction in which a discharge pressure of the discharge port increases. The pressure applied to the adjustment ring is raised by controlling the solenoid valve. In this manner, the adjustment ring is operated against a biasing force of the coil spring. An operating form is set so as to reduce the discharge pressure in the discharge port.

According to the techniques respectively disclosed in References 1 and 2, a current value to be supplied to an electromagnetic solenoid is calculated based on the map so as to realize proper control by using the current value calculated in this way. However, viscosity of the hydraulic operating oil increases at a low temperature. Accordingly, it is necessary to consider a temperature when the current value to be supplied to the electromagnetic solenoid is set. However, the techniques respectively disclosed in References 1 and 2 do not take the temperature into consideration. Consequently, there is room for improvement.

Here, as disclosed in Reference 3, it is conceivable to use a pump which can change the discharge pressure. However, even though the pump is configured in this way, the discharge pressure is greatly affected by the temperature of the hydraulic operating oil. For example, even if the map is set using the techniques respectively disclosed in References 1 and 2 and the control is performed by calculating the current value to be supplied to the solenoid valve based on the map, it is difficult to obtain a target discharge pressure.

In order to eliminate this disadvantage, it is conceivable to set table data which takes the temperature into consideration. However, if controlling of a variable capacity-type pump disclosed in Reference 3 is considered, the table data has a data structure in which a current to be supplied to the solenoid valve is calculated based on rotation speed (rotation speed per unit time) of a drive source of the pump, capacity of the set pump, and an oil temperature. Accordingly, the table data requires a huge amount of data, and a nonvolatile memory having large capacity is required. In addition, if the table data has the huge amount of data, a process becomes complicated when the table data is set.

Thus, a need exists for a pump device which is not susceptible to the drawback mentioned above.

SUMMARY

A feature of a pump device according to an aspect of this disclosure resides in that the pump device includes a variable capacity-type pump unit configured to include an inner rotor having a plurality of external teeth and rotatable around a first shaft core, an outer rotor having a plurality of internal teeth meshing with a portion of the plurality of external teeth of the inner rotor and rotatable around a second shaft core, a housing accommodating the inner rotor and the outer rotor, a suction port and a discharge port which are formed in the housing, an adjustment member rotatably supporting the outer rotor and adjusting a discharge pressure of a fluid in the discharge port by changing a positional relationship between the first shaft core and the second shaft core, a biasing mechanism biasing the adjustment member in a direction in which the discharge pressure is increased or decreased, a control flow passage causing a fluid pressure from the discharge port to be applied to the adjustment member to apply a pressure to the adjustment member against a biasing force of the biasing mechanism, a solenoid valve interposed in the control flow passage in order to adjust the fluid pressure to be applied to the adjustment member, a bypass flow passage causing the fluid of the discharge port to flow into the suction port, and a relief valve disposed in the bypass flow passage so as to be brought into an open state when the discharge pressure reaches a predetermined value or more, a rotation speed sensor measuring a rotation speed per unit time of a drive source that drives the inner rotor or the outer rotor, and a control unit controlling the solenoid valve. The control unit includes a pressure value conversion unit that converts a target discharge pressure into a conversion target discharge pressure serving as position information within a predetermined range, in a definition region where a maximum discharge pressure and a minimum discharge pressure which are set based on the rotation speed of the drive source and a temperature of the fluid are respectively defined as a maximum value and a minimum value in the predetermined range, a map data selection unit that stores first map data in which the relief valve is brought into an open state in the maximum discharge pressure and second map data in which the relief valve is brought into a closed state in the maximum discharge pressure, as map data having a data structure represented by an orthogonal coordinate system in which the definition region is denoted in a direction of a target axis and a target current value of the solenoid valve is denoted in a direction of an output axis orthogonal to the target axis, and that selects any one of the first map data and the second map data, based on the rotation speed of the drive source measured by the rotation speed sensor and the temperature of the fluid measured by a temperature sensor, and an output current control unit that acquires the target current value corresponding to the conversion target discharge pressure with reference to the selected map data, and that outputs the target current value to the solenoid valve.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and additional features and characteristics of this disclosure will become more apparent from the following detailed description considered with the reference to the accompanying drawings, wherein:

FIG. 1 is a hydraulic pressure circuit diagram illustrating a configuration of a pump control device;

FIG. 2 is a sectional view of a pump unit for which a discharge pressure is set to a maximum;

FIG. 3 is a sectional view of the pump unit for which the discharge pressure is set to a minimum;

FIG. 4 is a block circuit diagram of a control unit;

FIG. 5 is a view illustrating a relationship between a target hydraulic pressure and a conversion target hydraulic pressure;

FIG. 6 is a view illustrating a shape of map data;

FIG. 7 is a view illustrating representative map data;

FIG. 8 is a graph illustrating a relationship between a hydraulic pressure and a current at mutually different rotation speeds when a temperature of a fluid is 0° C.;

FIG. 9 is a graph illustrating a relationship between the hydraulic pressure and the current at mutually different rotation speeds when the temperature of the fluid is 30° C.;

FIG. 10 is a graph illustrating a relationship between the hydraulic pressure and the current at mutually different rotation speeds when the temperature of the fluid is 60° C.;

FIG. 11 is a graph illustrating a relationship between the hydraulic pressure and the current at mutually different rotation speeds when the temperature of the fluid is 90° C.;

FIG. 12 is a view illustrating a map data correspondence table; and

FIG. 13 is a flowchart of a discharge pressure control routine.

DETAILED DESCRIPTION

Hereinafter, embodiments disclosed here will be described with reference to the drawings.

Basic Configuration

As illustrated in FIG. 1, a pump device 100 is configured to include a variable capacity-type pump unit P driven by an engine E as a drive source, a solenoid valve V for controlling a hydraulic pressure (hereinafter, also referred to as a discharge pressure) of oil (example of a fluid) discharged from the pump unit P, and a control unit C for controlling the solenoid valve V, based on a measuring result of a rotation speed sensor SR and a measuring result of a temperature sensor ST.

The pump device 100 is installed in a vehicle such as a passenger car. The pump unit P is driven by the engine E of the vehicle, and suctions the oil of an oil pan of the engine E by using a suction flow passage 1 so as to supply the oil via a supply flow passage 2. The vehicle includes a hydraulic pressure actuator 3 such as a valve timing controller for setting opening and closing timings of an intake valve of the engine E and a hydraulic pressure-type transmission, and a main gallery 4 for lubricating the engine E. The oil is supplied thereto from the supply flow passage 2. The pump device 100 may be configured to supply water or chemicals in addition to the oil.

As illustrated in FIG. 1, the pump device 100 includes a supply flow passage 2, a control flow passage 5, and a drain flow passage 6. The solenoid valve V is interposed in the control flow passage 5, and the control flow passage 5 supplies a portion of the oil (example of the fluid) to be fed to the supply flow passage 2 to a pressure chamber PS (refer to FIG. 2) of the pump unit P via the solenoid valve V. The drain flow passage 6 discharges the oil of the pressure chamber PS via the solenoid valve V.

The control unit C functions as an ECU for controlling an oil pressure. A measuring signal of the rotation speed sensor SR which acquires a rotation speed per unit time (hereinafter, abbreviated as a “rotation speed”) of a crankshaft of the engine E (example of a drive source, hereinafter, abbreviated as the “engine E”) and a measuring signal from the temperature sensor ST which measures an oil temperature (temperature of the fluid) of the oil suctioned by the pump unit P are input to the control unit C.

In a case where the control unit C acquires a target hydraulic pressure (example of a target discharge pressure) from the outside, the control unit C acquires a target current value with reference to map data M (FIG. 5), and drives the solenoid valve V (strictly, an electromagnetic solenoid of the solenoid valve V) by using the target current value. In this manner, a control form is adopted so as to supply the oil having a proper target discharge pressure (this control form will be described later).

FIG. 1 illustrates a two position switching type in which spools are set at 2 positions as the solenoid valve V. The solenoid valve V is not limited to this configuration. For example, a relief valve or an unload valve may be used which can adjust the fluid pressure applied to the pressure chamber PS (refer to FIG. 2) via the control flow passage 5 by electromagnetically controlling a relief pressure. The solenoid valve V is held at an initial position illustrated in FIG. 1 in a case where a drive current is not supplied to the solenoid valve V (the solenoid valve V is not driven). In this manner, the control flow passage 5 and the drain flow passage 6 communicate with each other, and the pressure of the pressure chamber PS is reduced to an atmospheric pressure. In addition, in a case where the drive current is supplied to the solenoid valve V (in a case where the solenoid valve V is driven), as the drive current increases, a flow of the oil is blocked in the drain flow passage 6, and concurrently, the hydraulic pressure acting on the pressure chamber PS from the control flow passage 5 increases.

Pump Unit

As illustrated in FIGS. 2 and 3, in the pump unit P, a housing H having a suction port 11 and a discharge port 12 accommodates an inner rotor 14, an outer rotor 15, and an adjustment mechanism 20.

The inner rotor 14 has a plurality of external teeth 14A, is rotatably supported around a driving shaft core X (example of a first shaft core), and is rotated in a direction indicated by an arrow in the drawing by a drive shaft 13 driven using the engine E. The outer rotor 15 has a plurality of internal teeth 15A meshing with the external teeth 14A of the inner rotor 14, and is rotatably supported around a driven shaft core Y (example of a second shaft core) which is eccentric from the driving shaft core X.

The pump unit P is also referred to as an internal gear type. The external teeth 14A of the inner rotor 14 are formed in a tooth surface shape following a mathematical curve. The teeth number of the internal teeth 15A of the outer rotor 15 is set to be one more than the teeth number of the external teeth 14A of the inner rotor 14.

The adjustment mechanism 20 includes an adjustment ring 21 (example of an adjustment member) which rotatably accommodates the outer rotor 15, an arm portion 22 formed integrally with the adjustment ring 21, and a compression coil-type adjustment spring 23 (example of a biasing mechanism) which applies a biasing force to the arm portion 22. In the adjustment mechanism 20, a guide pin 24 to be fixed to the housing H is inserted into a pair of elongated guide holes 21A formed in the adjustment ring 21. In this manner, the adjustment ring 21 is operated in a state of being guided by the pair of guide pins 24.

In addition, oil seals 25 for maintaining a sealed state even when the adjustment ring 21 is operated are respectively provided at two locations on an outer periphery of the adjustment ring 21 and in a protruding end of the arm portion 22. In this manner, on an outer peripheral side of the adjustment ring 21 in an internal space of the housing H, a low pressure chamber LS communicating with the suction port 11, a high pressure chamber HS communicating with the discharge port 12, and the pressure chamber PS are formed. In particular, a control hole 16 communicating with the control flow passage 5 is formed on a wall surface of the housing H configuring the pressure chamber PS.

The adjustment ring 21 adjusts the discharge pressure of the oil in the discharge port 12 by changing a positional relationship between the driving shaft core X and the driven shaft core Y. Specifically, the adjustment mechanism 20 operates the adjustment ring 21 in a state of being guided by the pair of guide pins 24. In this manner, the outer rotor 15 is moved in a form where the driven shaft core Y revolves around the driving shaft core X. According to this movement, a meshing relationship in a pressurizing region between the external teeth 14A of the inner rotor 14 and the internal teeth 15A of the outer rotor 15 is changed so as to realize adjustment of the discharge pressure of the oil. As a result of adjusting the discharge pressure, a discharge amount of the oil is also adjusted.

In addition, in a case where the adjustment ring 21 (arm portion 22) adopts a posture illustrated in FIG. 2, a meshing depth between the external teeth 14A of the inner rotor 14 and the internal teeth 15A of the outer rotor 15 in the discharge port 12 is greatly changed. Accordingly, the discharge pressure of the oil is maximized (pump capacity is maximized). In a case where the adjustment ring 21 (arm portion 22) adopts a posture illustrated in FIG. 3, the meshing depth between the external teeth 14A of the inner rotor 14 and the internal teeth 15A of the outer rotor 15 in the discharge port 12 is less changed. Accordingly, the discharge pressure of the oil is minimized (pump capacity is minimized).

Furthermore, the biasing force of the adjustment spring 23 is applied from the pump unit P in a direction in which the discharge pressure of the oil is increased. In this manner, the pressure of the pressure chamber PS is controlled so that the adjustment ring 21 is operated against the biasing force of the adjustment spring 23. Accordingly, the oil can be supplied in a state where the discharge pressure is set to any desired value.

The pump unit P adopts a configuration in which the inner rotor 14 is rotationally driven and rotated using the drive shaft 13 driven by the engine E. However, a configuration may be adopted in which the outer rotor 15 is rotationally driven using a drive force of the engine E.

Pump Unit: Capacity Control

In a case where the drive current is not supplied to the solenoid valve V when the engine E is operated, the oil of the pressure chamber PS is discharged outward via the drain flow passage 6. Accordingly, the pressure of the pressure chamber PS is equal to an atmospheric pressure. In this manner, the adjustment ring 21 is caused to maintain the posture illustrated in FIG. 2 by the biasing force of the adjustment spring 23, and the discharge pressure of the oil in the discharge port 12 is maximized (flow rate is maximized).

Therefore, as when the engine E starts, in a situation where the rotation speed of the engine E is low and the oil amount decreases, even if the control unit C does not perform controlling to supply the drive current to the solenoid valve V, the oil amount required for the hydraulic pressure actuator 3 or the main gallery 4 is supplied.

In addition, in a case where it is necessary to adjust the discharge pressure (discharge amount) from the pump unit P to the supply flow passage 2, the control unit C adjusts the drive current to be supplied to the solenoid valve V so as to control the oil pressure supplied from the solenoid valve V to the pressure chamber PS via the control flow passage 5. In this manner, the adjustment ring 21 is operated integrally with the arm portion 22 up to a position corresponding to the oil pressure applied to the pressure chamber PS. Accordingly, the adjustment of the discharge pressure (discharge amount) of the oil is realized.

The pump unit P includes a bypass flow passage 26 which causes the fluid of the discharge port 12 to flow into the suction port 11, and a relief valve 27 disposed in the bypass flow passage 26. The relief valve 27 is configured to be brought into an open state if the discharge pressure of the discharge port 12 is equal to or more than a predetermined value. A hydraulic pressure sensor SP is provided on the discharge port 12 side of the pump unit P (refer to FIG. 1).

Control Unit

As illustrated in FIG. 4, the control unit C includes a region setting unit 31, a pressure value conversion unit 32, a map data selection unit 33, and an output current control unit 34.

In the control unit C, the region setting unit 31, the pressure value conversion unit 32, the map data selection unit 33, and the output current control unit 34 are configured to adopt software. However, these may be configured to adopt hardware, or may be configured to adopt a combination of the hardware and the software.

A measuring signal of the rotation speed sensor SR and a measuring signal of the temperature sensor ST are input to the region setting unit 31. Based on combinations of the rotation speed of the engine E (drive source) and the oil temperature (temperature of the fluid) of the oil, in the region setting unit 31, an upper limit value Max (example of the maximum discharge pressure) and a lower limit value Min (example of the minimum discharge pressure) of the hydraulic pressure which can be discharged in each combination are stored in advance. If the target hydraulic pressure is input to the pressure value conversion unit 32, as illustrated in FIG. 5, the region setting unit 31 specifies the upper limit value Max and the lower limit value Min of the hydraulic pressure which can be discharged, based on the rotation speed of the engine E measured by the rotation speed sensor SR at that time and the oil temperature measured by the temperature sensor ST at that time. The region setting unit 31 outputs the upper limit value Max and the lower limit value Min of the specified hydraulic pressure to the pressure value conversion unit 32. The pressure value conversion unit 32 sets the input upper limit value Max and the input lower limit value Min in a definition region D, and performs conversion so as to fall within a range of 0 to 1 (range in a vertical axis direction). In the definition region D, the upper limit value Max and the lower limit value Min which are set based on the rotation speed of the engine E (drive source) and the oil temperature of the oil are respectively defined as a maximum value and a minimum value in a predetermined range.

Specifically, in the definition region D of 0 to 1, the upper limit value Max expressed by MPa (mega Pascal) is converted into “1”, and the lower limit value Min expressed by MPa (mega Pascal) is converted into “0”.

Thereafter, in the pressure value conversion unit 32, in the definition region D, the input target hydraulic pressure is converted into a conversion target hydraulic pressure (example of a conversion target discharge pressure) having position information within the predetermined range. That is, in a state where the upper limit value Max is associated with a value of “1” in the definition region D and the lower limit value Min is associated with a value of “0”, the target hydraulic pressure between the upper limit value Max and the lower limit value Min is converted by the pressure value conversion unit 32, and is provided as a numerical value included in the range of 0 to 1. The numerical value obtained by converting the target hydraulic pressure in this way is called the conversion target hydraulic pressure. The specified conversion target hydraulic pressure is output to the output current control unit 34.

As illustrated in FIG. 6, the map data M has a data structure represented by an orthogonal coordinate system in which the definition region D in the range of 0 to 1 is denoted in a direction of a vertical axis (target axis) and the target current value is denoted in a direction of a horizontal axis (output axis) orthogonal to the vertical axis (target axis).

As illustrated in FIG. 6, the map data M is configured to include an upper limit line portion Ma, a lower limit line portion Mb, and a conversion line portion Mc. In order to realize the target hydraulic pressure, the target current value for supplying power to the solenoid valve V is acquired from the map data M as the target current value for the conversion target hydraulic pressure obtained by converting the target hydraulic pressure.

As the specific map data M, the map data selection unit 33 mainly stores first map data M1 indicating a relationship between the conversion target hydraulic pressure and the target current value when the relief valve 27 is brought into an open state in the maximum discharge pressure, and a second map data M2 indicating a relationship between the conversion target hydraulic pressure and the target current value when the relief valve 27 is brought into a closed state in the maximum discharge pressure. As illustrated in FIG. 7, the map data selection unit 33 according to the present embodiment stores a total of three items of the map data such as one item of the first map data M1 and two items of second map data M2A and M2B. Out of the two items of the second map data M2A and M2B, the second map data M2A is applied to a case where the rotation speed of the engine E is greater than a predetermined value, and the second map data M2B is applied to a case where the rotation speed of the engine E is smaller than the predetermined value.

The first map data M1, the second map data M2A, and the second map data M2B are prepared by aggregating a plurality of items of the map data formed using a relationship between the discharge pressure and the current value which are set in accordance with the rotation speed of the engine E in predetermined oil temperatures (0° C., 30° C., 60° C., and 90° C.) illustrated in FIGS. 8 to 11.

FIGS. 8 to 11 are graphs illustrating each change in the discharge pressure which results from an increase in the current value when different rotation speeds are set in a case where the oil temperatures are respectively 0° C., 30° C., 60° C., and 90° C. In FIGS. 8 to 11, the vertical axis of the upper graph shows an actual value of the discharge pressure, and the vertical axis of the lower graph shows that the upper limit value Max and the lower limit value Min of the discharge pressure of the upper graph are converted into the definition region D. The upper graph shows a plurality of items of the map data. However, when the map data has the same current value, the rotation speed of the engine E is lowered as the discharge pressure is lowered.

In FIG. 8 illustrating a case where the oil temperature of the oil is 0° C., if the upper graphs of the respective rotation speeds are converted so that the vertical axis shows the definition region D, the lower graphs show the result. The lower graphs substantially overlap each other regardless of the rotation speed. The lower graphs can be aggregated in one type of graph, that is, the first map data M1 illustrated in FIG. 7. On the other hand, in FIGS. 9 to 11 illustrating a case where the oil temperatures of the oil are respectively 30° C., 60° C., and 90° C., if the upper graphs of the respective rotation speeds are converted so that the vertical axis shows the definition region D to become the lower graphs, the converted graphs can be aggregated into the first map data M1 when the rotation speed of the engine E is high. As the rotation speed decreases, the converted graphs can be aggregated into the second map data M2A, and further into the second map data M2B.

The first map data M1 illustrated in FIGS. 7 and 8 to 11 is a graph obtained by aggregating changes in the discharge pressure when the rotation speed of the engine E is high and the relief valve 27 is brought into the open state in the maximum discharge pressure. The second map data M2A which is one of the items of the second map data M2 is a graph obtained by aggregating changes in the discharge pressure when the rotation speed of the engine E is approximately medium and the relief valve 27 is brought into the closed state in a state where the maximum discharge pressure is equal to or more than a predetermined value. The second map data M2B which is one of the items of the second map data M2 is a graph obtained by aggregating changes in the discharge pressure when the rotation speed of the engine E is low and the relief valve 27 is brought into the closed state in a state where the maximum discharge pressure is equal to or smaller than predetermined value.

The first map data M1 shows a characteristic that the discharge pressure is not changed until the relief valve 27 is closed by applying the current to the solenoid valve V, and that the discharge pressure starts to be greatly lowered when the discharge pressure exceeds a predetermined current value. On the other hand, the map data M2A and M2B show a characteristic that the discharge pressure is gradually lowered by applying the current to the solenoid valve V, and that the discharge pressure starts to be greatly lowered when the discharge pressure exceeds the predetermined current value. A value of the discharge pressure which brings the relief valve 27 into the open state in the pump device 100 can be calculated using a structure or a test operation of the pump device 100.

Based on a progress in the discharge pressure illustrated in FIGS. 8 to 11, the map data M corresponding to the rotation speed of the engine E and the oil temperature of the oil which are measured from the first map data M1, the second map data M2A, and the second map data M2B is selected. In this manner, for example, a map data correspondence table illustrated in FIG. 12 can be obtained. The map data selection unit 33 stores a plurality of items of the map data M1, M2A, and M2B, and the map data correspondence table. Based on the rotation speed of the engine E measured by the rotation speed sensor SR and the oil temperature of the oil measured by the temperature sensor ST, the map data selection unit 33 refers to the map data correspondence table (for example, FIG. 12), and selects whether to apply any one of the first map data M1, the second map data M2A, and the second map data M2B. The applied map data M is output to the output current control unit 34, and the output current control unit 34 determines an instruction current value, based on the input conversion target hydraulic pressure and the map data M selected by the map data selection unit 33.

In this manner, in a situation where the target hydraulic pressure input to the pressure value conversion unit 32 is constant, it is possible to acquire a proper target current value to be applied to the solenoid valve V with reference to the map data M selected in the map data selection unit 33. In a case where any one of the rotation speed of the engine E and the oil temperature fluctuates, the upper limit value Max and the lower limit value Min which are set by the region setting unit 31 are changed. In conjunction therewith, the conversion target hydraulic pressure in the definition region D is changed. Accordingly, the map data selection unit 33 newly selects the map data M corresponding to the changed rotation speed of the engine E and the changed oil temperature from the map data correspondence table. The pressure value conversion unit 32 converts the input target hydraulic pressure into the new conversion target hydraulic pressure, and the output current control unit 34 applies the new target current value corresponding to the new conversion target hydraulic pressure to the solenoid valve V.

According to the present embodiment, the actual discharge pressure (actual hydraulic pressure) measured by the hydraulic pressure sensor SP is input to the output current control unit 34. In the output current control unit 34, the target current value is controlled to be fed back, based on the discharge pressure measured by the hydraulic pressure sensor SP. Specifically, the actual discharge pressure (actual hydraulic pressure) and the target hydraulic pressure corresponding to the target current value obtained with reference to the map data M are compared with each other. In a case where there is a difference between both of these, the target current value is corrected, based on the difference. In this manner, the discharge pressure of the pump unit P can coincide with (or approximate to) the target hydraulic pressure. The output current control unit 34 may be configured so that the feedback control based on a measured value of the hydraulic pressure sensor SP is not performed.

Control Form

A flowchart in FIG. 13 shows a schematic control configuration in a discharge pressure control routine performed by the control unit C. If the control starts, based on the map data correspondence table, the map data selection unit 33 selects the map data M corresponding to the rotation speed (the rotation speed per unit time) of the engine E measured by the rotation speed sensor SR and the oil temperature of the oil measured by the temperature sensor ST. In parallel therewith, based on the rotation speed measured by the rotation speed sensor SR and the oil temperature measured by the temperature sensor ST, the region setting unit 31 specifies the upper limit value Max and the lower limit value Min which enable the target hydraulic pressure to be obtained, and outputs the upper limit value Max and the lower limit value Min to the pressure value conversion unit 32. The pressure value conversion unit 32 converts the upper limit value Max and the lower limit value Min so as to show the definition region D in which the upper limit value Max corresponds to “1” and the lower limit value Min corresponds to “0” (Step #101 and Step #102).

According to this control, based on the rotation speed of the engine E measured by the rotation speed sensor SR and the oil temperature of the oil, the map data M corresponding to the rotation speed and the oil temperature is selected from a plurality of items of the map data M1, M2A, and M2B stored in the map data selection unit 33 with reference to the map data correspondence table, and a process for outputting (loading) the map data M to the output current control unit 34 is performed. In addition, based on the rotation speed measured by the rotation speed sensor SR and the oil temperature measured by the temperature sensor ST, the region setting unit 31 specifies the upper limit value Max and the lower limit value Min, and the pressure value conversion unit 32 sets the definition region D.

If the target hydraulic pressure is input to the pressure value conversion unit 32, the target hydraulic pressure is converted into the conversion target hydraulic pressure within a range of the definition region D. According to this control, the target hydraulic pressure serving as a real value is converted into the conversion target hydraulic pressure which is a numerical value included within the range of 0 to 1 corresponding to the definition region D (Step #103 and Step #104).

The conversion target hydraulic pressure converted from the target hydraulic pressure in the pressure value conversion unit 32 is output to the output current control unit 34. From the loaded map data M and the input conversion target hydraulic pressure, the output current control unit 34 acquires the target current value corresponding thereto, and outputs the current value corresponding to the target current value to the solenoid valve V (Step #105 and Step #106).

As described above, the first map data M1 and the second map data M2 (M2A and M2B) which are set depending on whether or not the maximum discharge pressure is the discharge pressure for bringing the relief valve 27 into an open state have inherent characteristics. Therefore, any one of the first map data M1 and the second map data M2 (M2A and M2B) is selected, based on the rotation speed of the engine E measured by the rotation speed sensor SR and the oil temperature of the oil. In this manner, in order to obtain the target discharge pressure corresponding to the rotation speed of the engine E and the oil temperature of the oil from the selected map data M, it is possible to properly set the target current value to be supplied to the solenoid valve V. In this manner, it is possible to reduce the number of items of the map data to be referenced. Therefore, the storage capacity of the map can be minimized in the control unit C, and the calculation process of the target current value can be simplified.

In a case where the maximum discharge pressure has a magnitude so that the relief valve 27 is not brought into the open state, the map data selection unit 33 selects the second map data M2. Here, as illustrated in FIGS. 9 to 11, in the maximum discharge pressure which has a magnitude so that the relief valve 27 is not brought into the open state, a pressure (for example, a medium pressure) slightly lower than the discharge pressure which brings the relief valve 27 into the open state and a considerably low pressure (for example, a low pressure) are mixed with each other. For example, if the maximum discharge pressure is the low pressure, the pressure applied to the adjustment member is low. Accordingly, in some cases, the pump device may be greatly affected by the biasing mechanism which biases the adjustment member in the direction in which of the discharge pressure is increased or decreased. On the other hand, in a case where the maximum discharge pressure is the medium pressure, the pump device is less affected by the biasing mechanism, and the pressure applied to the adjustment member becomes dominant. Therefore, in the maximum discharge pressure which has a magnitude so that the relief valve 27 is not brought into the open state, in some cases, a progress of the map data may greatly vary depending on a magnitude of the discharge pressure.

Therefore, according to this configuration, two items of the second map data M2A and M2B are stored in the map data selection unit 33. In this manner, in accordance with to the rotation speed of the engine E and the oil temperature of the oil, the map data selection unit 33 can select the proper map data M in which the maximum discharge pressure is set to have a magnitude so that the relief valve 27 is not brought into the open state. As a result, in order to obtain the target discharge pressure corresponding to the rotation speed and the oil temperature, it is possible to accurately set the target current value to be supplied to the solenoid valve V.

Other Embodiments

In the above-described embodiment, an example has been described in which the map data selection unit 33 stores two items of the map data M2A and M2B as the second map data M2. However, the number of items of the second map data M2 is not limited to two. In a case where the map data is less changed even if the upper limit value Max (maximum discharge pressure) which has a magnitude so that the relief valve 27 is not brought into the open state is raised or lowered, the number of items of the second map data M2 may be one. In addition, in order to further improve the accuracy of the target current value to be supplied to the solenoid valve V, the number of items of the second map data M2 may be three or more.

In the above-described embodiment, an example has been described in which the definition region D falls within the range of 0 to 1. However, alternatively, the definition region D may fall within a range set using any desired numerical value.

Embodiments disclosed here can be widely utilized for a pump device having a variable capacity-type pump unit and a control unit.

According to this configuration, in a case where the target discharge pressure is acquired, the control unit causes the pressure value conversion unit to convert the target discharge pressure into the conversion target discharge pressure. Next, the map data selection unit selects by one of the first map data when the relief valve is in an open state and the second map data when the relief valve is in a closed state, which are stored as the map data, based on the rotation speed of the drive source measured by the rotation speed sensor and the temperature of the fluid measured by the temperature sensor. Next, the output current control unit acquires the target current value corresponding to the conversion target discharge pressure with reference to the selected map data, and outputs the target current value to the solenoid valve.

Even though the target discharge pressure has the same value, the current value to be supplied to the solenoid valve varies corresponding to the rotation speed of the drive source and the temperature of the fluid. For this reason, it is necessary to prepare the map data corresponding to the rotation speed of the drive source and the temperature of the fluid.

In this case, if it is considered that the target current value is acquired with reference to the map data by using the target discharge pressure expressed in units of MPa (mega Pascal), it is necessary to prepare the data structure on which the target discharge pressure and the target current value corresponding to units of MPa are reflected as the map data. However, in the data structure configured in this way, in a case where the rotation speed of the drive source or the temperature of the fluid is changed, the map data needs to be corrected or modified in order to cope with this change, or the map data needs to be newly set. In a case where the map data is newly prepared, it is necessary to provide multiple items of the map data in advance.

In contrast, according to this configuration, the definition region is defined in which the maximum discharge pressure and the minimum discharge pressure which are set based on the rotation speed of the drive source and the temperature of the fluid are respectively set as the maximum value and the minimum value in the predetermined range. The pressure value conversion unit converts the target discharge pressure into the conversion target discharge pressure serving as the position information within the predetermined range. Then, the map data has the data structure represented by the orthogonal coordinate system in which the definition region is denoted in the direction of the target axis and the target current value of the solenoid valve is denoted in the direction of the output axis orthogonal to the target axis. The map data is configured to include the first map data when the relief valve is brought into an open state in the maximum discharge pressure and the second map data when the relief valve is brought into a closed state in the maximum discharge pressure.

In a case where the maximum discharge pressure set based on the rotation speed of the drive source measured by the rotation speed sensor and the temperature of the fluid measured by the temperature sensor is high enough to bring the relief valve into the open state, the first map data is selected. The first map data has a characteristic that the discharge pressure is not changed until the relief valve is closed by applying the current to the solenoid valve and the discharge pressure starts to be greatly lowered when the discharge pressure exceeds a predetermined current value. On the other hand, in a case where the maximum discharge pressure has a magnitude so that the relief valve is not brought into the open state, the second map data is selected. The second map data has a characteristic that the discharge pressure is gradually lowered by applying the current to the solenoid valve and the discharge pressure starts to be greatly lowered when the discharge pressure exceeds the predetermined current value. A value of the discharge pressure which brings the relief valve into the open state in the pump device can be calculated using a structure or a test operation of the pump device.

In this way, the first map data and the second map data which are set according to whether or not the maximum discharge pressure is the discharge pressure for bringing the relief valve into the open state have inherent characteristics. Therefore, any one of the first map data and the second map data is selected, based on the maximum discharge pressure. In this manner, it is possible to properly set the target current value to be supplied to the solenoid valve in order to obtain the target discharge pressure corresponding to the rotation speed of the drive source and the temperature of the fluid from the selected map data. In this manner, it is possible to reduce the number of items of the map data to be referenced. Accordingly, storage capacity of the map can be minimized in the control unit, and a calculation process of the target current value can be simplified.

Therefore, one is selected from two items of the map data in accordance with the maximum discharge pressure. In this manner, it is possible to properly set the target current value to be supplied to the solenoid valve in order to obtain the target discharge pressure corresponding to the rotation speed and the temperature of the fluid. As a result, the storage capacity of the map can be minimized in the control unit, and the calculation process of the target current value can be simplified.

Another feature resides in that the map data selection unit stores a plurality of items of the second map data in accordance with an upper limit value of the target discharge pressure based on the rotation speed of the drive source and the temperature of the fluid.

In a case where the maximum discharge pressure has a magnitude so that the relief valve is not brought into the open state, the second map is selected as the map data. However, in the maximum discharge pressure which is not high enough to bring the relief valve into the open state, a pressure (medium pressure) slightly lower than the discharge pressure which brings the relief valve into the open state and a considerably low pressure (low pressure) are mixed with each other. For example, in a case where the maximum discharge pressure is the low pressure, the pressure applied to the adjustment member is low. Accordingly, in some cases, the pump device may be greatly affected by the biasing mechanism which biases the adjustment member in the direction in which the discharge pressure is increased or decreased. On the other hand, in a case where the maximum discharge pressure is the medium pressure, the pump device is less affected by the biasing mechanism, and the pressure applied to the adjustment member becomes dominant. Therefore, in the maximum discharge pressure which has a magnitude so that the relief valve is not brought into the open state, it is considered that the map data may greatly vary depending on the discharge pressure.

Therefore, according to this configuration, the map data selection unit stores a plurality of items of the second map data in accordance with the upper limit value of the target discharge pressure, based on the rotation speed of the drive source and the temperature of the fluid. In this manner, the proper map data in which the maximum discharge pressure is set to have a magnitude so that the relief valve is not brought into the open state can be selected in accordance with the rotation speed and the temperature of the fluid. As a result, it is possible to accurately set the target current value to be supplied to the solenoid valve in order to obtain the target discharge pressure corresponding to the rotation speed and the temperature of the fluid.

Another feature resides in that the pump device further includes a hydraulic pressure sensor measuring the discharge pressure, and the target current value is controlled to be fed back, based on the discharge pressure measured by the hydraulic pressure sensor.

Similarly to this configuration, if the target current value is controlled to be fed back based on the discharge pressure measured by the hydraulic pressure sensor, in a case where an actual discharge pressure and the target hydraulic pressure do not coincide with each other, the target current value can be easily adjusted. In this manner, the discharge pressure of the electric pump can coincide with (or approximate to) the target hydraulic pressure.

The principles, preferred embodiment and mode of operation of the present invention have been described in the foregoing specification. However, the invention which is intended to be protected is not to be construed as limited to the particular embodiments disclosed. Further, the embodiments described herein are to be regarded as illustrative rather than restrictive. Variations and changes may be made by others, and equivalents employed, without departing from the spirit of the present invention. Accordingly, it is expressly intended that all such variations, changes and equivalents which fall within the spirit and scope of the present invention as defined in the claims, be embraced thereby.

PUMP DEVICE

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