Purge valve drive control device

Abstract

Provided is a purge valve driving control device that is able to detect abnormality using an existing circuit as much as possible while ensuring resolution and accuracy in detecting a solenoid resistance value.　A solenoid 1a has one end to which a battery voltage is applied via a first connection terminal 3a and has the other end connected to a second connection terminal 3b. In a driver circuit 120, a driving transistor 4 and a shunt resistor 5 are connected in series and provided between the second connection terminal 3b and the ground, and an overcurrent detection circuit 11 enabling detection of occurrence of an overcurrent in the driving transistor 4 on the basis of a voltage of the shunt resistor 5 is provided. A microcomputer 110 is configured to be able to determine the presence or absence of occurrence of a battery short-circuit equivalent to an electrical short-circuit state between the first connection terminal 3a and the second connection terminal 3b on the basis of an output of the overcurrent detection circuit 11.　

Description

[Technical field]

[0001] The present invention relates to a purge valve drive control device, and more particularly to one which aims to improve the reliability and stability of drive control. [Background technology]

[0002] It is now mandatory for gasoline-powered automobiles to be equipped with devices to prevent the emission of fuel evaporative emissions, and it is well known that the vehicle is equipped with a fuel evaporative emissions control device having a configuration suited to the structure, etc., of the vehicle. For example, a relatively well-known configuration is one in which fuel evaporative gas is adsorbed onto activated charcoal stored in a canister, and when the engine is running, a portion of the engine's intake air is passed through the canister and released (purged) into the engine's intake system via a purge valve, i.e., the air is allowed to flow into the engine's intake port and used as engine fuel.

[0003] In order to realize appropriate engine control, it is necessary to grasp as accurately as possible the amount of evaporated fuel supplied to the engine intake port via the purge valve. For this reason, the opening degree of the purge valve is usually controlled by feedback control or the like. In particular, in the case of a solenoid-type purge valve, its opening is determined by the magnitude of the current passing through it, but the main factors that determine the current passing through it, the battery voltage and the resistance value of the solenoid, change depending on the operating state of the vehicle and the ambient temperature.

[0004] For this reason, a detection circuit is usually provided to detect the resistance value of the solenoid, and while successively detecting the resistance value, the deviation of the current flowing from the target value is feedback corrected, thereby ensuring an appropriate current flowing, thereby reliably ensuring the desired opening degree (see, for example, Patent Document 1, etc.).

[0005] On the other hand, in the above-mentioned purge valve drive control device, from the viewpoint of the importance of the device, it is required to detect an abnormal state such as a short circuit or an open circuit in the connection terminal with the purge valve. FIG. 6 shows an example of the configuration of a conventional purge valve drive control device. Hereinafter, abnormality detection in the conventional device will be described with reference to this figure. In a conventional purge valve drive control device using this vehicle electronic control unit ECU, a battery voltage VB is applied to one end of a solenoid 51a of a purge valve 51, while the other end of the solenoid 51a is connected to a driver circuit 52 composed of a so-called low-side transistor 53.

[0006] A low-side transistor 53 of the driver circuit 52 is turned on and off in response to PWM control by a microcomputer (referred to as "CPU" in FIG. 6) 54, thereby controlling the current flowing through the solenoid 51a, thereby making it possible to adjust the valve opening.

[0007] This conventional device is also provided with a resistance detection circuit 55 for detecting the resistance value of the solenoid 51a (hereinafter, for convenience of explanation, referred to as the "solenoid resistance value"). A voltage dividing resistor (indicated as "Rdiv" in FIG. 6) 56 is provided between the connection point between the solenoid 51a and the low-side transistor 53 and the ground. The resistance detection circuit 55 amplifies and outputs a differential voltage Vdef, which is the difference between the battery voltage VB and the divided voltage Vdiv obtained at the voltage dividing resistor 56, to the microcomputer 54 as a detection voltage Vdet.

[0008] In the microcomputer 54, the solenoid resistance value is calculated based on the output voltage of the resistance detection circuit 55, the actual battery voltage VB detected by the battery voltage detection circuit (indicated as "VB-DET" in FIG. 6), and the resistance value of the voltage dividing resistor 56. The calculated solenoid resistance value is used for duty correction in PWM control.

[0009] In such a conventional device, in addition to detecting the solenoid resistance value as described above, first and second comparators 59, 60 are provided to enable detection of the presence or absence of an abnormality in the first and second connection terminals 58a, 58b to which the solenoid 51a is connected. That is, the output voltage of the resistance detection circuit 55 is compared with threshold values ​​Vth1, Vth2 in first and second comparators 59, 60, respectively, and the presence or absence of an abnormality is determined in the microcomputer 54 based on the comparison result.

[0010] For example, if for some reason the supply line of the battery voltage VB is directly connected to the output of the driver circuit 52, in other words, a state equivalent to the first connection terminal 58a and the second connection terminal 58b being electrically connected directly (hereinafter, for convenience of explanation, referred to as "battery short circuit"), the differential voltage Vdef will be approximately zero V, and naturally the detection voltage Vdet of the resistance detection circuit 55 will also be approximately zero V. In this case, the first comparator 59 detects that the output voltage of the resistance detection circuit 55 falls below the first threshold value Vth1, and as a result, the microcomputer 54 determines that a battery short circuit has occurred.

[0011] On the other hand, when a terminal open occurs, in which the connection between the driver circuit 52 and the solenoid 51a is cut off, or when a ground short occurs, in which the output stage of the driver circuit 52 is directly connected to ground, in other words, when the second connection terminal 58b is connected to ground, the differential voltage Vdef will be close to the battery voltage VB in either case.

[0012] In this case, the second comparator 60 detects that the output voltage of the resistance detection circuit 55 exceeds the second threshold Vth2, and as a result, the microcomputer 54 determines that a terminal open circuit or a short circuit to ground has occurred. [Prior art documents] [Patent documents]

[0013] [Patent Document 1] JP 2013-199874 A Summary of the Invention [Problem to be solved by the invention]

[0014] However, in the conventional configuration in which the detection voltage Vdet of the resistance detection circuit 55 is used for abnormality detection, there are problems such as limitations on the detection timing of abnormality detection due to the electrical characteristics of the solenoid, and reduced resolution and accuracy in detecting the solenoid resistance value. First, FIG. 7 is a schematic diagram showing waveforms of the main parts when controlling the energization of the solenoid 51a. Hereinafter, the detection timing of the abnormality detection will be described with reference to this figure.

[0015] The energization control of the solenoid 51a of the purge valve 51 is usually performed by so-called PWM control, so that the low-side transistor 53 is driven to be turned on and off by the microcomputer 54 at a predetermined duty ratio. When the solenoid 51a is energized and the low-side transistor 53 is turned on, the voltage Vout at the second connection terminal 58b drops to a voltage close to zero V, while the energizing current Is gradually increases (see Figures 7(A) and 7(B)). Furthermore, the detection voltage Vdet of the resistance detection circuit 55 also rises with the increase in the energizing current Is, and then becomes a constant voltage (see FIG. 7C).

[0016] After a predetermined energization time has elapsed, the low-side transistor 53 is turned off by the microcomputer 54. However, due to the inductance of the solenoid 51a, the voltage Vout at the second connection terminal 58b rises temporarily and reaches a predetermined clamp voltage Vcl, and then gradually decreases over time to a predetermined battery voltage VB (see FIG. 7(A)). Due to the influence of inductance, the flowing current Is also does not immediately become zero when the low-side transistor 53 is turned off, but decreases over time (see FIG. 7B).

[0017] Furthermore, the output voltage Vdet of the resistance detection circuit 55 temporarily becomes the maximum output (5V in this example) due to the influence of inductance when the low-side transistor 53 is off, and then drops to zero V as the inductance decreases, and then the output state returns to the normal state (see FIG. 7(C)). Note that in FIG. 7(C), the period represented by Ttr is the period during which a transient response due to the inductance occurs, and after this period has elapsed, the output state of the resistance detection circuit 55 returns to the normal state.

[0018] As a result, the detection of the solenoid resistance value by the resistance detection circuit 55 and the detection of abnormalities such as a battery short circuit are limited to the period after the above-mentioned transient response period Ttr has elapsed, that is, from time ta to time tb when the low-side transistor 53 is turned on again.

[0019] Next, the degradation of resolution and accuracy in detecting the solenoid resistance value will be described with reference to FIG. In Fig. 8, a change characteristic example of the output voltage Vdet of the resistance detection circuit 55 with respect to the change in the battery voltage VB when the solenoid resistance value is 38.5Ω is shown by a solid characteristic line marked with a symbol L1 (hereinafter, for convenience of explanation, referred to as "characteristic line L1"). Note that the dotted lines above and below the characteristic line L1 indicate an example of the fluctuation range. Note that Fig. 8 shows an example when the maximum output voltage of the resistance detection circuit 55 is 5V.

[0020] In addition, an example of the change characteristic of the output voltage Vdet of the resistance detection circuit 55 in response to a change in the battery voltage VB when the solenoid resistance value is 17Ω is shown by a solid characteristic line labeled L2 (hereinafter, for convenience of explanation, referred to as "characteristic line L2"). The dotted lines above and below the characteristic line L2 indicate an example of the fluctuation range.

[0021] Furthermore, in this example, it is assumed that the threshold value Vth1 of the first comparator 59 is 500 mV, and the threshold value Vth2 of the second comparator 60 is 4500 mV. Therefore, in this case, the output voltage Vdet of the resistance detection circuit 55 that can be used to detect the solenoid resistance value in the microcomputer 54 will be limited to the range of 500 mV < Vdet < 4500 mV.

[0022] The above characteristic lines L1 and L2 are the result of adjusting the circuit constants etc. of the resistance detection circuit 55 in consideration of the limited range of the output voltage Vdet. In solenoid resistance value detection, in order to ensure higher resolution and accuracy, for example, it is necessary to ensure that the slopes of the characteristic lines L1 and L2, that is, the change in the output voltage Vdet with respect to the change in the battery voltage VB, are as large as possible within the possible range.

[0023] Therefore, the limitation of the output voltage Vdet as described above will naturally limit the resolution and accuracy of the solenoid resistance value detection. For example, if the characteristic line L1 shown in FIG. 8 is adjusted such that the output voltage Vdet near the upper end side thereof, that is, near the battery voltage VB = 16V, becomes near 5V, and the slope of the characteristic line is increased to ensure higher resolution and accuracy of the solenoid resistance value detection.

[0024] In this case, even if it is possible to improve the resolution and accuracy of the solenoid resistance value detection in the vicinity of the central part of the characteristic line L1, that is, in the vicinity of the battery voltage of approximately 10V to 14V (the shaded part in FIG. 8), the range that overlaps near the previous threshold value Vth2 in the upper end side part of the characteristic line L1 will overlap with the abnormal determination range. For this reason, this overlapping part has to be excluded from both abnormal determination and solenoid resistance value detection. That is, there is a problem that the improvement of the resolution and accuracy of the solenoid resistance value detection is limited to a partial range, and it becomes difficult to improve the resolution and accuracy without unevenness in the desired range.

[0025] The present invention has been made in view of the above actual situation, and provides a purge valve drive control device capable of abnormal detection with a circuit configuration that makes the best use of the existing circuit while ensuring the resolution and accuracy of the solenoid resistance value detection.

Means for Solving the Problems

[0026] In order to achieve the above object of the present invention, the purge valve drive control device according to the present invention comprises: A purge valve drive control device including a driver circuit for energizing a solenoid of a solenoid purge valve and a microcomputer configured to be able to control a valve opening degree of the solenoid purge valve via the driver circuit, The solenoid has one end to which a battery voltage is applied via a first connection terminal provided on the purge valve drive control device, and the other end is connected to a second connection terminal provided on the purge valve drive control device, the driver circuit includes a drive transistor as a low-side transistor and a shunt resistor, the drive transistor and the shunt resistor being connected in series between the second connection terminal and ground in this order from the second connection terminal side; an overcurrent detection circuit configured to be able to detect occurrence of an overcurrent in the drive transistor based on a voltage of the shunt resistor; The microcomputer is configured to be able to determine, based on the output of the overcurrent detection circuit, whether or not a battery short circuit equivalent to an electrical short state between the first connection terminal and the second connection terminal has occurred. Effect of the Invention

[0027] According to the present invention, a battery short circuit, in which the potential at the connection point between the drive transistor and the solenoid becomes the battery voltage, can be detected based on the current flowing through the drive transistor by utilizing the drive transistor. This makes it possible to adopt a configuration that utilizes existing circuits, and unlike conventional circuits, this is separate from the solenoid resistance detection circuit, so there is no degradation in the resolution and accuracy of solenoid resistance detection, and stable solenoid resistance detection can be ensured. Furthermore, by providing a comparator and comparing the voltage at the connection point between the drive transistor and the solenoid with a reference voltage, it becomes possible to detect a ground short circuit, in which the connection point is short-circuited to ground, or an open terminal, in which the connection between the drive transistor and the solenoid is severed.As with a battery short circuit, this has the effect of making it possible to detect circuit abnormalities while ensuring stable solenoid resistance value detection without degrading the resolution and accuracy of solenoid resistance value detection. [Brief description of the drawings]

[0028] [Figure 1] 1 is a configuration diagram showing a configuration example of a purge valve drive control device according to an embodiment of the present invention; [Diagram 2] 5 is a flowchart showing a procedure for detecting a battery short circuit by an abnormality detection process in the purge valve drive control device according to the embodiment of the present invention. [Diagram 3] 5 is a flowchart showing a procedure for detecting a ground short circuit or an open terminal by the abnormality detection process in the purge valve drive control device according to the embodiment of the present invention. [Figure 4] 4A is a waveform diagram showing a schematic diagram of signal changes in main parts to explain the drive state of the purge valve by the purge valve drive control device and the timing of abnormality detection in an embodiment of the present invention, FIG. 4A is a waveform diagram showing a schematic diagram of changes in voltage Vout of the second connection terminal, FIG. 4B is a waveform diagram showing a schematic diagram of changes in current Is flowing through the second connection terminal, and FIG. 4C is a waveform diagram showing a schematic diagram of changes in output voltage Vdet of the resistance detection voltage amplifier. [Diagram 5] 4 is a schematic diagram illustrating a relationship between an abnormality detection operation and on / off of a drive transistor of a valve drive circuit provided in the purge valve drive control device according to the embodiment of the present invention. FIG. [Figure 6] FIG. 1 is a diagram showing a configuration example of a conventional device. [Figure 7]These are waveform diagrams showing schematic signal changes in main parts to explain the drive state of a purge valve and the timing of abnormality detection in a conventional device, where FIG. 7(A) is a waveform diagram showing schematic changes in voltage Vout of the second connection terminal, FIG. 7(B) is a waveform diagram showing schematic changes in current Is flowing through the solenoid, and FIG. 7(C) is a waveform diagram showing schematic changes in the detection voltage of the resistance detection circuit. [Figure 8] 10 is a characteristic diagram showing the correlation between the battery voltage and the output voltage of the resistance value detection circuit in detection of a solenoid resistance value by a conventional device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] Hereinafter, an embodiment of the present invention will be described with reference to FIGS. It should be noted that the components, arrangements, etc. described below do not limit the present invention, and various modifications can be made within the scope of the present invention. First, a configuration example of a purge valve drive control device according to an embodiment of the present invention will be described with reference to FIG. The purge valve drive control device in the embodiment of the present invention is configured to control the drive of a solenoid purge valve 1 as well as detect abnormalities (described in detail later) centered around a vehicle electronic control unit (referred to as "ECU" in FIG. 1) 100 mounted on a vehicle.

[0030] The vehicle electronic control unit 100 in the embodiment of the present invention is configured with, as its main components, a microcomputer (represented as "CPU" in FIG. 1) 110, a driver circuit (represented as "DRV" in FIG. 1) 120, a resistance detection voltage amplifier 130, a battery voltage detection circuit (represented as "VB-DET" in FIG. 1) 140, and a voltage dividing resistor (represented as "Rdiv" in FIG. 1) 2.

[0031] The microcomputer 110 has a memory element such as a RAM or a ROM (not shown), an analog-digital converter (not shown), an interface circuit, etc., and has a known and commonly-known configuration. The microcomputer 110 in the embodiment of the present invention is configured to be capable of executing various control processes such as solenoid resistance value detection, purge valve drive control, and abnormality detection, as will be described in detail later.

[0032] The vehicle electronic control unit 100 in the embodiment of the present invention is provided with first and second connection terminals 3a, 3b for connection to a purge valve 1 provided externally. That is, the battery voltage VB is applied to the first connection terminal 3a, and one end of the solenoid 1a of the purge valve 1 is connected thereto. The other end of the solenoid 1a is connected to a second connection terminal 3b, which is connected to the output stage of the driver circuit 120, and the solenoid 1a is controlled by the driver circuit 120 as described below.

[0033] The resistance detection voltage amplifier 130 amplifies and outputs a voltage required for calculating the solenoid resistance value, which is the resistance value of the solenoid 1a, in the microcomputer 110. The resistance detection voltage amplifier 130 has a well-known amplifier circuit configuration.

[0034] One input stage of the resistance detection voltage amplifier 130 is connected to the first connection terminal 3a, and is adapted to receive the battery voltage VB. The other input stage of the resistance detection voltage amplifier 130 is connected to the second connection terminal 3b, and the voltage dividing resistor 2 is connected between this second connection terminal 3b and the ground.

[0035] Therefore, a voltage corresponding to the voltage drop in the voltage dividing resistor 2 is applied to the other input stage of the resistance detection voltage amplifier 130 . Here, if the voltage at the second connection terminal 3b is the drive output voltage Vout, the input voltage of the resistance detection voltage amplifier 130 is the differential voltage Vdef, the amplification degree of the resistance detection voltage amplifier 130 is α, the battery voltage is VB, and the output voltage of the resistance detection voltage amplifier 130 is the detection voltage Vdet, the detection voltage Vdet input to the microcomputer 110 is expressed by the following equation 1.

[0036] Vdet=α×Vdef=α×(VB-Vout)...Equation 1

[0037] On the other hand, if the solenoid resistance value of the solenoid 1a is Rva and the resistance value of the voltage dividing resistor 2 is Rdiv, the relationship expressed by the following equation 2 is established between these two resistance values ​​and the drive output voltage Vout and the differential voltage Vdef.

[0038] Vdef / Vout=Rva / Rdiv...Formula 2

[0039] Moreover, Vout is expressed by the following formula 3.

[0040] Vout=VB×Rdiv / (Rva+Rdiv)...Equation 3

[0041] Thus, in the microcomputer 110, the solenoid resistance value Rva is calculated based on the following equation 4.

[0042] Rva=(Vdet×Rdiv) / (α×VB-Vdet)=...Equation 4

[0043] The solenoid resistance value calculated as described above is used by the microcomputer 110 for PWM control of the drive transistor 4 provided in the driver circuit 120, which will be described later.

[0044] The battery voltage detection circuit 140 is configured to convert the battery voltage VB into a voltage suitable for the microcomputer 110 and output the voltage. The microcomputer 110 is adapted to execute a monitoring process to determine whether the battery voltage VB is normal or not. The value of the battery voltage VB obtained by the battery voltage detection circuit 140 is also adapted to be used for the calculation of the above-mentioned solenoid resistance value, etc.

[0045] The driver circuit 120 is composed of a driving transistor 4, a shunt resistor (represented as "Rs" in FIG. 1) 5, an overcurrent detection circuit (represented as "I-DET" in FIG. 1) 11, a comparator 12, and an error register (represented as "F-REG" in FIG. 1) 13 as its main components. The driver circuit 120 in the embodiment of the present invention controls the energization of the solenoid 1a in the same manner as in the conventional case, and is configured to be capable of detecting abnormalities together with the microcomputer 110, as will be described in detail later.

[0046] Here, in the embodiment of the present invention, abnormality detection means detection of an abnormal state of the voltage and current at the first and second connection terminals 3a, 3b. The above-mentioned abnormal states in the embodiment of the present invention are roughly classified into two types, namely, a "battery short circuit" and a "ground short circuit / terminal open circuit", as will be described below. The term "battery short circuit" refers to a state equivalent to an electrical short circuit between the first connection terminal 3a and the second connection terminal 3b. In other words, the term "battery short circuit" refers to a state in which the battery voltage VB is directly applied to the second connection terminal 3b.

[0047] Next, "ground short circuit / terminal open" is a general term for ground short circuit and terminal open circuit. In the embodiment of the present invention, a distinction is not made between a ground short circuit and a terminal open circuit, but only one of the two is determined (details will be described later). Note that "short to ground" refers to a state in which the second connection terminal 3b is connected to ground, and "open terminal" refers to a state in which the connection between the second connection terminal 3b and the solenoid 1a is cut off, i.e., the drain of the drive transistor 4 described later is in an open state.

[0048] Next, a specific configuration of the driver circuit 120 will be described. First, the drive transistor 4 is PWM-controlled in response to a valve drive control signal Svc input from the microcomputer 110, and controls the energization of the solenoid 1a of the purge valve 1. The PWM control of the drive transistor 4 by the microcomputer 110 is basically the same as in the conventional method, and will be briefly described below.

[0049] In the microcomputer 110, the duty ratio in the PWM control of the drive transistor 4 is set according to the desired valve opening of the purge valve 1, in other words, the operating state of the vehicle, and the drive transistor 4 is driven at that duty ratio.

[0050] However, since the solenoid resistance value fluctuates due to fluctuations in battery voltage and temperature changes, the duty ratio set as described above does not provide the desired valve opening degree. Therefore, in the microcomputer 110, the duty ratio is corrected based on the solenoid resistance value calculated as described above, and PWM control of the drive transistor 4 is performed by feedback control.

[0051] The driving transistor 4 in the embodiment of the present invention functions as a so-called low-side transistor. Specifically, in the embodiment of the present invention, a MOSFET (Metal-Oxide-Semiconductor-Field-Effect-Transistor) is used as the drive transistor 4. The drain of the drive transistor 4 is connected to one end of the solenoid 1a of the purge valve 1 via the second connection terminal 3b. The other end of the solenoid 1a is adapted to receive a battery voltage VB via a first connection terminal 3a provided on the vehicle electronic control unit 100.

[0052] In addition, a shunt resistor 5 is provided between the source of the drive transistor 4 and the ground. The above-mentioned valve drive control signal Svc is input to the gate of the drive transistor 4, and as described above, is subjected to PWM control by the microcomputer 110, so that the current flowing through the solenoid 1a is controlled by the drive transistor 4.

[0053] The overcurrent detection circuit 11 detects an overcurrent that flows through the drive transistor 4 due to the occurrence of a "battery short circuit." That is, first, the voltage of the shunt resistor 5 (hereinafter, for convenience of explanation, referred to as the “shunt voltage”) is input to the input stage of the overcurrent detection circuit 11.

[0054] When the current flowing through the shunt resistor 5 becomes an overcurrent due to a "battery short circuit," the shunt voltage exceeds a predetermined overcurrent reference voltage set in the overcurrent detection circuit 11. The overcurrent detection circuit 11 is configured to output a predetermined overcurrent detection voltage when the shunt voltage exceeds the predetermined overcurrent reference voltage, determining that the shunt current Ish has exceeded a predetermined reference overcurrent Ith. Note that such an overcurrent detection circuit 11 is not unique to the present invention, but has a circuit configuration that has been well known in the past.

[0055] The comparator 12 is for detecting the occurrence of a ground short circuit or a terminal open circuit. The non-inverting input terminal of the comparator 12 is connected to the second connection terminal 3b, while a predetermined judgment reference voltage Vth is applied to the inverting input terminal. When there is no “battery short circuit” or “ground short circuit / terminal open circuit” and the driver circuit 120 is operating normally, a voltage exceeding a predetermined judgment reference voltage Vth corresponding to the operating state of the drive transistor 4 is applied to the non-inverting input terminal of the comparator 12. In this case, the comparator 12 outputs a predetermined positive voltage that corresponds to a logical value "1".

[0056] On the other hand, in a state where a "ground short" occurs in which the second connection terminal 3b is connected to ground, or in a state where an "open terminal" occurs in which the connection between the second connection terminal 3b and the solenoid 1a is cut and the second connection terminal 3b is in an open state, in either case, the voltage at the non-inverting input terminal of the comparator 12 becomes a voltage close to the ground potential and falls below the above-mentioned judgment reference voltage Vth. As a result, the comparator 12 outputs a voltage corresponding to a logical value "0", that is, 0V or a predetermined negative voltage.

[0057] The error register 13 is a register for temporarily storing whether or not the overcurrent detection circuit 11 has detected a "battery short circuit" and whether or not the comparator 12 has detected a "ground short circuit / terminal open circuit." Such error register 13 is divided (not shown) into, for example, a register area for temporarily writing and storing whether or not a "battery short circuit" has been detected (hereinafter, for convenience of explanation, referred to as the "battery short circuit register area"), and a register area for temporarily writing and storing whether or not a "ground short circuit / terminal open" has been detected (hereinafter, for convenience of explanation, referred to as the "ground short circuit / terminal open register area").

[0058] As mentioned above, when a "battery short circuit" occurs and a predetermined overcurrent detection voltage (e.g., 5V) is output from the overcurrent detection circuit 11, a logical value of "1" is written to the battery short circuit register area and is stored and held until the output voltage of the overcurrent detection circuit 11 is reset to zero.

[0059] On the other hand, when a "ground short circuit / terminal open" occurs and the output voltage of comparator 12 changes from a voltage corresponding to a logical value of "1" to a voltage corresponding to a logical value of "0", the logical value of "1", indicating that a "ground short circuit / terminal open" has occurred, is written to the ground short circuit / terminal open register area and is stored and held until the output voltage of comparator 12 returns to the specified positive voltage.

[0060] The logical value data written to the error register 13 as described above is used for abnormality determination processing in the microcomputer 110 as will be described later. It should be noted that "logical value data" here is a general term for the logical values ​​"1" and "0."

[0061] Next, an abnormality detection processing operation in the purge valve drive control device in the embodiment of the present invention will be described with reference to the flowcharts shown in FIGS. 2 and 3 and the waveform diagram shown in FIG. First, when the process by the microcomputer 110 is started, it is determined whether the "drive transistor is ON", that is, whether the drive transistor 4 is in the ON state (driving state) or not (see step S110 in FIG. 2).

[0062] In step S110, if it is determined that the drive transistor 4 is in the on state (YES), battery short-circuit detection is performed as described below. Also, in step S110, if it is determined that the drive transistor 4 is not in the on state (NO), ground short-circuit / terminal open detection is performed as described below.

[0063] Steps S120 to S150 explain the flow of operations of the entire device from when an overcurrent caused by a battery short circuit is detected by the overcurrent detection circuit 11 until the microcomputer 110 determines that a battery short circuit has occurred. Similarly, steps S120 and S160 to S180 explain the flow of operation of the entire device until the overcurrent detection circuit 11 does not detect an overcurrent due to a battery short circuit and the microcomputer 110 determines that the battery voltage is normal.

[0064] First, the overcurrent detection circuit 11 determines whether or not an "overcurrent has occurred" due to a battery short circuit, that is, whether or not the state is "Ish>Ith" (see step S120 in FIG. 2).

[0065] In the overcurrent detection circuit 11, when the shunt voltage exceeds a predetermined overcurrent reference voltage, it is determined that an overcurrent has occurred, i.e., the shunt current Ish has exceeded a predetermined reference overcurrent Ith (if YES), and a predetermined overcurrent detection voltage is output. It should be noted that the overcurrent detection circuit 11 does not operate only at the timing of step S120, but is always in an operating state in which it can detect the presence or absence of the above-mentioned overcurrent after the supply of power supply voltage begins in conjunction with the startup of the purge valve drive control device.

[0066] Each step in FIG. 2 is merely for the convenience of explaining the overall flow of the abnormality determination process by the microcomputer 110, the overcurrent detection circuit 11, the comparator 12, and the error register 13, and does not limit the timing of circuit operation. Thus, when a predetermined overcurrent detection voltage is output from the overcurrent detection circuit 11, "VB short circuit occurrence error register writing" is performed (see step S130 in FIG. 2). Here, "VB short circuit occurrence" means the occurrence of a battery short circuit.

[0067] That is, when a predetermined overcurrent detection voltage is output from the overcurrent detection circuit 11, the logic value "1" indicating that a battery short circuit has occurred is written to the battery short circuit register area described above in the error register 13. Meanwhile, in the microcomputer 110, "error register reading" is performed (see step S140 in FIG. 2). That is, in the microcomputer 110, the logic value data of the battery short-circuit register area of ​​the error register 13 is repeatedly read out at a predetermined timing.

[0068] In the purge valve drive control device according to the embodiment of the present invention, when the drive transistor 4 is in the on state, the only abnormality that can be detected is a battery short circuit, and therefore the target area for reading the logical value data of the error register 13 by the microcomputer 110 is the battery short circuit register area only.

[0069] In the microcomputer 110, when it is determined that the logical value data read from the battery short-circuit register area of ​​the error register 13 is "1", it is determined that a "VB short-circuit has occurred", that is, that a battery short-circuit has occurred (see step S150 in FIG. 2). After the determination in step S150 is made, the process returns to the main routine (not shown), and after other required processing is performed, the above-mentioned operation is restarted from the beginning.

[0070] In addition, if it is determined that a battery short circuit has occurred, normally warning processes such as turning on warning lights, sounding an alarm, and other abnormality response processes such as forcibly stopping device operation are executed, but the specific processing content should be determined individually according to the vehicle specifications, etc., and is not limited to specific processing content, etc.

[0071] On the other hand, in the overcurrent detection circuit 11, if the shunt voltage does not exceed the predetermined overcurrent reference voltage (NO), the output of the overcurrent detection circuit 11 is a predetermined voltage (e.g., zero V) corresponding to no battery short circuit. As a result, "error register normal writing" is performed in the error register 13 (see step S160 in FIG. 2). That is, the logical value "0" is written in the battery short-circuit register area of ​​the error register 13, which corresponds to a normal state in which no battery short-circuit has occurred.

[0072] Meanwhile, in the microcomputer 110, "error register reading" is performed (see step S170 in FIG. 2). That is, the microcomputer 110 reads out the logic value data of the battery short-circuit register area of ​​the error register 13 .

[0073] In the microcomputer 110, when it is determined that the logical value data read from the battery short-circuit register area of ​​the error register 13 is logical value "0", it is determined that "VB normal judgment" is made, that is, that the battery is in a normal state where no short-circuit has occurred (see step S180 in FIG. 2). Thereafter, the process returns to a main routine (not shown) and other required processes are executed, after which the above-mentioned operation centered around the microcomputer 110 is restarted from the beginning.

[0074] On the other hand, when the microcomputer 110 judges whether the driving transistor 4 is ON (see step S110 in FIG. 2) and judges that the driving transistor 4 is not ON (NO), the microcomputer 110 performs ground short-circuit / terminal open detection based on the operation of the comparator 12 and the error register 13 as described below. To explain this in more detail below, first, the comparator 12 judges whether or not "terminal voltage detection" has occurred, that is, judges whether or not "Vout>Vth" (see step S200 in FIG. 3).

[0075] As described above, the second connection terminal 3b is connected to the non-inverting input terminal of the comparator 12, and the output voltage Vout at the second connection terminal 3b is applied to the non-inverting input terminal thereof, and a comparison is made with the judgment reference voltage Vth set at the inverting input terminal thereof. When no ground short circuit or terminal open circuit occurs, Vout>Vth, and therefore comparator 12 outputs a predetermined voltage (for example, 5V) that corresponds to a logical value High (YES in FIG. 3).

[0076] When the output of the comparator 12 becomes a predetermined voltage corresponding to the logical value High, an "error register normal write" is performed in the error register 13 (see step S210 in FIG. 3). That is, the logical value "0" is written in the ground short-circuit / terminal open register area of ​​the error register 13, which corresponds to the output voltage Vout at the second connection terminal 3b being normal.

[0077] In addition, like the overcurrent detection circuit 11 described above, the comparator 12 does not operate only at the timing of step S200, but is in an operating state at all times after the supply of power supply voltage begins upon startup of this device.

[0078] Meanwhile, in the microcomputer 110, "error register reading" is performed (see step S220 in FIG. 3). That is, in the microcomputer 110, the logic value data of the ground short-circuit / terminal open register area of ​​the error register 13 is read out. The microcomputer 110 reads out the logical value “0” from the ground short-circuit / terminal open register area of ​​the error register 13 as logical value data.

[0079] Next, in the microcomputer 110, since the logical value "0" is read from the ground short-circuit / terminal open register area, it is determined that the terminals are "normal", that is, that the first and second connection terminals 3a, 3b are electrically normal (see step S230 in FIG. 3). Thereafter, the process returns to a main routine (not shown) where other required processing is carried out, after which the above-mentioned operation centered around the microcomputer 110 is repeated again.

[0080] On the other hand, if Vout>Vth is not true, that is, if the output voltage Vout is lower than the judgment reference voltage Vth (if NO in step S200 in FIG. 3), the comparator 12 outputs a predetermined voltage equivalent to the logical value "0" as described above. When the comparator 12 outputs a predetermined voltage corresponding to a logical value "0", "ground short / open error register writing" is performed in the error register 13 (see step S240 in FIG. 3). That is, in the error register 13, the logic value "1" indicating that a ground short circuit or terminal open has occurred is written in the ground short circuit or terminal open register area described above.

[0081] Meanwhile, in the microcomputer 110, "error register reading" is performed (see step S250 in FIG. 3). That is, in the microcomputer 110 , the logic value data of the logic value “1” is read out from the ground short-circuit / terminal open register area of ​​the error register 13 .

[0082] Next, in the microcomputer 110, based on the logical value "1" read out from the ground short-circuit / terminal open register area, a "ground short-circuit / open judgment" is made, i.e., it is judged that a ground short-circuit / terminal open has occurred at the second connection terminal 3b (see step S260 in FIG. 3). Thereafter, the process returns to a main routine (not shown) where other required processing is carried out, after which the above-mentioned operation centered around the microcomputer 110 is repeated again.

[0083] FIG. 4 is a waveform diagram showing a schematic diagram of the waveforms of the main parts for explaining the temporal relationship between the on / off of the drive transistor 4 and the abnormality detection process described above. Below, the temporal relationship between the on / off of the drive transistor 4 and the abnormality detection process will be explained with reference to this diagram. In each of FIGS. 4(A) to 4(C), the horizontal axis is the time axis. In addition, the vertical axis in FIG. 4(A) represents voltage, the vertical axis in FIG. 4(B) represents current, and the vertical axis in FIG. 4(C) represents voltage.

[0084] In FIG. 4, the period from time t0 to time tb is a period during which the drive transistor 4 is in an off state, and the period from time tb to time tc is a period during which the drive transistor 4 is in an on state. Since the control of the current supply to the solenoid 1a by the drive transistor 4 is the same as in the conventional technique, the example of change in the output voltage Vout at the second connection terminal 3b in association with the on / off of the drive transistor 4 shown in FIG. 4(A), the example of change in the current Is flowing to the solenoid 1a via the second connection terminal 3b shown in FIG. 4(B), and the example of change in the output voltage Vdet of the resistance detection voltage amplifier 130 shown in FIG. 4(C) are all the same as in the conventional technique.

[0085] In a conventional circuit in which the resistance detection voltage amplifier 130 is used to detect a battery short circuit, a ground short circuit, and an open terminal, it was only possible to detect a battery short circuit, a ground short circuit, and an open terminal during the period from time t0 to time ta during which a transient response caused by inductance occurs after the drive transistor 4 is turned off and until the drive transistor 4 is turned on, that is, during the period from time ta to time tb.

[0086] In contrast to this, in the embodiment of the present invention, while the drive transistor 4 is in the off state, that is, between time t0 and time tb, the comparator 12 can detect a ground short circuit / terminal open circuit without being limited to a specific timing (see steps S200 to S260 in FIG. 3). Furthermore, while the drive transistor 4 is in the on state, that is, between time tb and time tc, battery short-circuit detection is possible by the resistance detection voltage amplifier 130 without being limited to a specific timing (see steps S110 to S180 in FIG. 2).

[0087] FIG. 5 shows an explanatory diagram for summarizing the relationship between the on / off state of the drive transistor 4 and abnormality detection described above, and the contents thereof will be described below with reference to FIG. In the explanatory diagram shown in Figure 5, the "ECU terminal status" column in the upper left corner of the page refers to the electrical status of the first and second connection terminals 3a, 3b of the vehicle electronic control unit 100, and the column shows "normal," "VB short circuit," "ground short circuit," and "terminal open," each of which is classified as such.

[0088] Here, "normal" means that no battery short circuit (VB short circuit), ground short circuit, or terminal open circuit has occurred, and the drive transistor 4 is controlling the energization of the solenoid 1a normally. In addition, "VB short circuit" means a state in which a battery short circuit has occurred, "ground short circuit" means a state in which the second connection terminal 3b is connected to ground, and "terminal open" means a state in which the connection between the second connection terminal 3b and the solenoid 1a is cut off.

[0089] As mentioned above, in the embodiment of the present invention, it is not possible to distinguish which abnormal state has occurred between "ground short" and "terminal open" by the comparison operation using comparator 12, but they are described separately here for the purpose of explaining that the circuit operation is the same.

[0090] Next, in FIG. 5, the column to the right of the "ECU Terminal Status" labeled "FET Voltage State" shows the voltage at the second connection terminal 3b in response to the on / off state of the drive transistor 4 for each category of the "ECU Terminal Status" in the left column.

[0091] Each of the items in the "FET voltage state" column will be explained below with reference to FIGS. 2 to 4 as appropriate. First, when the ECU terminal state is normal and the drive transistor 4 is on, the voltage at the second connection terminal 3b becomes zero V (see FIG. 4(A)). Next, when the ECU terminal state is VB short circuit (battery short circuit) and the drive transistor 4 is on, an overcurrent flows through the shunt resistor 5. In this case, the battery short circuit is detected by the microcomputer 110 based on the overcurrent detection (see steps S110 to S150 in FIG. 2).

[0092] Next, when the ECU terminal state is shorted to ground or open, and the drive transistor 4 is on, the voltage at the second connection terminal 3b becomes zero volts. In this case, since it is impossible to distinguish from the case where the operation of the drive transistor 4 is normal, the microcomputer 110 does not judge whether a ground short circuit or terminal open circuit has occurred, as described above.

[0093] Next, when the ECU terminal state is normal and the drive transistor 4 is off, the voltage at the second connection terminal 3b becomes the battery voltage VB (see FIG. 4(A)). Next, when the ECU terminal state is a battery short circuit and the drive transistor 4 is off, the voltage at the second connection terminal 3b becomes the battery voltage VB.

[0094] Next, when the ECU terminal state is short-circuited to ground or open-circuited and the drive transistor 4 is off, the voltage at the second connection terminal 3b becomes approximately zero V. In this case, the microcomputer 110 detects the battery short-circuit / open-circuited terminal based on the output of the comparator 12 (see step S200 and steps S240 to S260 in FIG. 3).

[0095] Thus, in the purge valve drive control device in the embodiment of the present invention, when the drive transistor 4 is off, it is possible to detect a ground short circuit or an open terminal by the comparator 12 provided in the driver circuit 120, while when the drive transistor 4 is on, it is possible to detect a battery short circuit by an overcurrent detection operation using this drive transistor 4. Unlike the conventional technology, abnormality detection is not limited to an extremely short period of time, so that abnormalities can be detected earlier than in the conventional technology. Moreover, since the driving transistor 4 can be used, the configuration can be simplified. Furthermore, unlike conventional techniques, the output voltage of the resistance detection voltage amplifier 130 is not used to detect the presence or absence of an abnormality in the first and second connection terminals 3a, 3b, but is provided only for detecting the solenoid resistance value, thereby ensuring higher resolution and accuracy in detecting the solenoid resistance value than conventional techniques. [Industrial Applicability]

[0096] The present invention can be applied to a purge valve drive control device in which it is desired to detect abnormalities using a circuit configuration that makes maximum use of existing circuits while ensuring the resolution and accuracy of solenoid resistance value detection.

Claims

1. A driver circuit for energizing a solenoid of a solenoid-type purge valve; a microcomputer that controls the valve opening of the solenoid purge valve via the driver circuit; A battery voltage detection circuit; a resistor sense voltage amplifier; A purge valve drive control device having The solenoid has one end to which a battery voltage is applied via a first connection terminal provided on the purge valve drive control device, and the other end connected to a second connection terminal provided on the purge valve drive control device, the driver circuit includes a drive transistor as a low-side transistor and a shunt resistor, the drive transistor and the shunt resistor being connected in series between the second connection terminal and ground in this order from the second connection terminal side, an overcurrent detection circuit configured to be able to detect occurrence of an overcurrent in the drive transistor based on a voltage of the shunt resistor; the microcomputer is configured to be able to determine, based on an output of the overcurrent detection circuit, whether or not a battery short circuit equivalent to an electrical short state between the first connection terminal and the second connection terminal has occurred; the battery voltage detection circuit detects the battery voltage; the resistance detection voltage amplifier has one input stage connected to the first connection terminal and the other input stage connected to the second connection terminal, amplifies a differential voltage between the battery voltage input to the one input stage and a voltage input to the other input stage, and outputs the amplified differential voltage to the microcomputer; a voltage dividing resistor connected to ground is connected between the other input stage and the second connection terminal; a resistance detection circuit for detecting a resistance of the solenoid based on the voltage obtained from the resistance detection voltage amplifier and the battery voltage obtained from the battery voltage detection circuit,

2. The driver circuit is provided with a comparator that is capable of detecting the occurrence of a ground short circuit equivalent to a state in which the second connection terminal is shorted to ground, or a terminal open state in which the connection between the second connection terminal and the solenoid is cut off, based on a comparison between the voltage of the second connection terminal and a judgment reference voltage; 2. The purge valve drive control device according to claim 1, wherein the microcomputer is configured to be able to determine whether or not a ground short circuit or a terminal open circuit has occurred based on the output of the comparator.

3. the driver circuit is provided with an error register configured to be able to write and store separately predetermined logical value data corresponding to the presence or absence of an overcurrent detected by the overcurrent detection circuit, and predetermined logical value data corresponding to the presence or absence of a ground short or a terminal open detected by the comparator; 3. The purge valve drive control device according to claim 2, wherein the microcomputer is configured to be able to determine whether or not a battery short circuit, a ground short circuit, or an open terminal has occurred based on the logical value data stored in the error register.

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